How are y'all stress testing? I know Fusion and other software have FEA capabilities but what are the tests you run? I was trying to find standards for a DH bike but haven't had much luck
How are y'all stress testing? I know Fusion and other software have FEA capabilities but what are the tests you run? I was trying to find...
How are y'all stress testing? I know Fusion and other software have FEA capabilities but what are the tests you run? I was trying to find standards for a DH bike but haven't had much luck
You could ask EFBE for the loads for category 5...
First rule of frame design, ignore marketing crap. Compare a whole bunch of different designs in Linkage and realize that everyone is slowly converging on the...
First rule of frame design, ignore marketing crap. Compare a whole bunch of different designs in Linkage and realize that everyone is slowly converging on the same thing.
The window of preferred anti-squat and leverage ratios is narrowing in on roughly 100% anti-squat at sag and a LR of 20-25% linear progression starting around 2.8 to 3.0. Anti-rise seems to still be down to designer tastes or a compromise of the chosen linkage platform / shock location.
The more time you spend in Linkage the more you realize everything has already been done...and thus why the window of optimized designs is narrowing.
My past builds.
2014 first fully, classic single pivot
2018 same design at the time as Nukeproof DH bike, now used on their Giga
2019 pull link. I pulled this design from Ancillotti, seems that Specialized likes this to and using it on the proto DH.
2022 another linkage driven single pivot, this little scissor link is a copy of one that Xprezo used on the AdHoc but I moved things around to get the LR I wanted.
Not shown....the countless number of designs worked out in Linkage to get numbers I liked but didn't build. I'll dig some of them up later.
I agree with your observations. Here's my latest creation. split High pivot pinion gearbox downduro bike. 210mm travel for 75mm stroke. around 120% anti-squat, 90%...
I agree with your observations. Here's my latest creation. split High pivot pinion gearbox downduro bike. 210mm travel for 75mm stroke. around 120% anti-squat, 90% anti-rise, 25% progression. Next design will have a motor in it as I feel this analog one outside of small design details, is about perfect for my use with the current available components.
Sooo when are you actually coming up with a name for brand and finally starting to build these beauties and sell them? 😄 Even mk1 and mk2 were pretty good, now this, what is it - mk5???, is super dialed!
How are y'all stress testing? I know Fusion and other software have FEA capabilities but what are the tests you run? I was trying to find...
How are y'all stress testing? I know Fusion and other software have FEA capabilities but what are the tests you run? I was trying to find standards for a DH bike but haven't had much luck
If you can get your hands on a broken dh frame or fork- cut it up and measure wall thickness etc. back out the strength that way.
could probably measure fork tube ID/OD without damaging it.
that would at least give a ballpark number
I ran 1.5ODx .056 wall 4130 downtube on a dh bike. Never broke or cracked it.
Sooo when are you actually coming up with a name for brand and finally starting to build these beauties and sell them? 😄 Even mk1 and...
Sooo when are you actually coming up with a name for brand and finally starting to build these beauties and sell them? 😄 Even mk1 and mk2 were pretty good, now this, what is it - mk5???, is super dialed!
No current plans to build for sale.
MK5 is in the works. Take Mk3 and Mk4 and smash them together you get Mk5, I need to finalize some flat sheet metal design for the shock tunnel and get that off to Send Cut Send.
When talking frame design for me the question is what are the design goals? I started making my own frames when what now is modern geo wasn't available so I was building slack n long when that wasn't a think for trail/enduro/am bikes. Now I could find pretty close to my preferred geo on a commercial bike. For me now it's more about honing in on the right combo or AS/AR/LR. I've done really progressive, linear, and unique S shape LR. The next one is mid/lowish progression with and end stroke ramp up in progression. The change in end stroke will function as mechanical bottom out control on the last 15mm of travel. The same layout is also going to allow me to build a 24" wheeled version for my kids that allows for adjustment from near flat linear to that same mid progression as above, and fit a bottle in the mainframe.
I think they were referring to how Spec patented the Horst link which they did not invent.
I thought spesh bought the patent from the inventor and then made it exclusive to them, which while pretty lame on spesh and for the companies who were liscencing it from the original inventor, isn't illegal.
How are y'all stress testing? I know Fusion and other software have FEA capabilities but what are the tests you run? I was trying to find...
How are y'all stress testing? I know Fusion and other software have FEA capabilities but what are the tests you run? I was trying to find standards for a DH bike but haven't had much luck
If you can get your hands on a broken dh frame or fork- cut it up and measure wall thickness etc. back out the strength that...
If you can get your hands on a broken dh frame or fork- cut it up and measure wall thickness etc. back out the strength that way.
could probably measure fork tube ID/OD without damaging it.
that would at least give a ballpark number
I ran 1.5ODx .056 wall 4130 downtube on a dh bike. Never broke or cracked it.
That’s a solid down tube! Was it 4130?
It looks to me like .9mm or 1.2mm x 38.1mm is pretty common for 4130 on a down tube. I guess it also depends if the DT has a shock mount on it and needs to be beefed up a bit.
@bradlowery Here’s some info on testing with EFBE.
No info there. If you want loads, it's 500 eur per component which is also a credit for any tests performed later. So in case you go forwards with production, it's basically free.
That’s a solid down tube! Was it 4130?
It looks to me like .9mm or 1.2mm x 38.1mm is pretty common for 4130 on a down...
That’s a solid down tube! Was it 4130?
It looks to me like .9mm or 1.2mm x 38.1mm is pretty common for 4130 on a down tube. I guess it also depends if the DT has a shock mount on it and needs to be beefed up a bit.
@bradlowery Here’s some info on testing with EFBE.
I wonder what happened with the NDA you have to sign to get the numbers...
A lot of the EFBE stuff is based on CEN bike testing standards, which you can find numbers on if you dig around.
Many of the big companies have frame testing standards that they have developed on their own as well which you're not going to get any numbers on.
Specialized had a Demo fully strain gauged and wired up that they had Matt Hunter doing Whistler laps on. It resulted in some very interesting data and led to the development of a completely new bottom out fatigue test for bigger full suspension bikes.
But Specialized also has a mutli million dollar test lab setup in Morgan Hill with half a dozen MTS test beds. That's why places like EFBE exist, good testing equipment is very expensive.
That place Neko used in Canada for Frameworks seemed like they know what they are doing.
I think the main benefit of EFBE is the grade 5 (DH) and grade 4 (trail) & co standards as it gives you an indication of how strong the frame is. If it's internal you don't have the information of how it compares to other companies.
But most of the biggish brands have their own testing labs in some way or shape.
A lot of the EFBE stuff is based on CEN bike testing standards, which you can find numbers on if you dig around.
Many of the...
A lot of the EFBE stuff is based on CEN bike testing standards, which you can find numbers on if you dig around.
Many of the big companies have frame testing standards that they have developed on their own as well which you're not going to get any numbers on.
Specialized had a Demo fully strain gauged and wired up that they had Matt Hunter doing Whistler laps on. It resulted in some very interesting data and led to the development of a completely new bottom out fatigue test for bigger full suspension bikes.
But Specialized also has a mutli million dollar test lab setup in Morgan Hill with half a dozen MTS test beds. That's why places like EFBE exist, good testing equipment is very expensive.
That place Neko used in Canada for Frameworks seemed like they know what they are doing.
was it this shape? That was my 4th or 5th frame (I cant remember) in about 18 months. They would all crack at the BB/seat tube junction. I literally got 1 day out of some of those frames. So Sexy looking, but also made out of wet cardboard.... 135mm rear hub and about as progressive as a soggy noodle. Specialized were fantastic though, I'd crack it on the weekend, show the bike shop on Monday morning and by Wednesday would have another frame. It was always new bike day lol
No, the old Demo with 27 seat stays. The Gwin version was a disaster in many ways.
It's sad when a company knows a product will fail, but keeps going forward with it. Like what happened with the Hubble Space Telescope and why it is now used an example of what not to do in every college level project management course.
That’s a solid down tube! Was it 4130?
It looks to me like .9mm or 1.2mm x 38.1mm is pretty common for 4130 on a down...
That’s a solid down tube! Was it 4130?
It looks to me like .9mm or 1.2mm x 38.1mm is pretty common for 4130 on a down tube. I guess it also depends if the DT has a shock mount on it and needs to be beefed up a bit.
@bradlowery Here’s some info on testing with EFBE.
Yes but it was a dh bike and it had the shock mount, and I didn’t want to worry.
On previous projects I’d used 1.5x.049 4130...
Yes but it was a dh bike and it had the shock mount, and I didn’t want to worry.
On previous projects I’d used 1.5x.049 4130 for the DT. I cracked one due to bad gusset design.
that’s always my concern with home made bikes- testing is always by the rider.
I remember your DH frames. Very cool stuff!
I’ve been using .9mm on these down tubes but now I’m thinking of going up to 1.2mm. The lower shock mount is half on the bb/st and half at the base of the dt. I was thinking I could go lighter on the dt due to that.
Here's a question, how do you feel about size specific chainstays or chainstay length in general? I like my chainstays to be about 435mm long, paired with a 480-490 reach, and I'm a 6'1 man with a long torso, but there has been a big push for longer stays for a "more balanced feel". What are your thoughts?
I think sized specific is very important, maybe don't have 4 sizes of rear centre, but rather one for S/M and another for L/XL atleast.
I'm same height, like my bikes around 490-500mm reach too.
Current bike has 462mm Chainstay, it is amazing for front end grip, with 63 Degree head angle you need a longer CS for flatter corners I find. Another bike I had was similar H/A but CS only 440 and it constantly pushed on flat corners. That chainstay length of 462 is the same across all the sizes, it works great for XL at 505mm reach but imagine that on a small, the CS is longer than the reach! The ride would be interesting.
In saying that, 462 makes manuals and last second pullups off drops rather difficult, I think 450-455 would be perfect IMO.
For my height and centralised riding style, 500mm reach, 455 CS, 660 stack, 63 degree H/A, 77-78 deg STA with a 240mm dropper is heaven. My current bike pretty much ticks all of those.
Here's a question, how do you feel about size specific chainstays or chainstay length in general? I like my chainstays to be about 435mm long, paired...
Here's a question, how do you feel about size specific chainstays or chainstay length in general? I like my chainstays to be about 435mm long, paired with a 480-490 reach, and I'm a 6'1 man with a long torso, but there has been a big push for longer stays for a "more balanced feel". What are your thoughts?
Great question! The tough thing about chainstay length is that there are very different camps on this topic, even within people of a certain height. I'm a tall person who swears by long chainstays, but lots of tall people hate them. So while it makes sense to have size specific chainstays so RC grows proportionately with FC, if they're not adjustable, your CS number's still not going to please everyone. As far as I see it, there are three options for frame manufacturers:
1. Adjustable chainstays with a big range of adjustment. Think of the outgoing Kona Process X, where you could choose 435mm or 450mm. That's a big, immediately noticeable difference, and can actually meet the desires of riders in both camps. I liked this idea. I miss my 10mm of chainstay adjustment on my old Mk.1 Megatower. For Santa Cruz, the swappable dropout/adjustable CS idea debuted with that bike and ended with that bike, once UDH debuted. RIP.
2. Pick a certain type of customer, and cater to that customer when determining chainstay length. Generally speaking, go fast racer-types like longer chainstays for front end grip and stability (and because we're smarter and right). "Fun" seekers, jibby types, and beginners like shorter stays because they're "more flickable" (and because they're wrong). A company can choose who their type of customer is, and cater to them with their chainstay length. For instance, SCOR sponsors Josh Lewis and has always had short stays. By contrast, RAAW is very much a "racer" bike and has always had longer stays. Similarly, while it's true that the new V10 has size-specific and adjustable-length chainstays, they're actually really long across the entire size range, even in the shortest setting. Taking this route is my vote because it builds a clear customer and brand narrative that can drive other decisions, too, like shock tune, internal/external cable routing, hardware accessibility, stack height, etc.
3. Play it safe,split it down the middle, and have a compromise chainstay length for everyone. This is the path I think most manufacturers take. It's never going to be super jibby and it's never gonna be super stable, but your average customer doesn't know the difference, and most of your opinionated riders still don't care enough to rule out a bike just because the chainstay is 6.723mm too short or too long. One big downside to this route is that you're not building a dedicated fan base with a clear customer narrative, which makes it hard to stand out in a rapidly homogenizing MTB landscape. But, the flipside is that you're also not scaring away a big chunk of the market. Lastly, being confident and decisive is scary, so it's way more fun to try to please everyone all the time!
Here's a question, how do you feel about size specific chainstays or chainstay length in general? I like my chainstays to be about 435mm long, paired...
Here's a question, how do you feel about size specific chainstays or chainstay length in general? I like my chainstays to be about 435mm long, paired with a 480-490 reach, and I'm a 6'1 man with a long torso, but there has been a big push for longer stays for a "more balanced feel". What are your thoughts?
Great question! The tough thing about chainstay length is that there are very different camps on this topic, even within people of a certain height. I'm...
Great question! The tough thing about chainstay length is that there are very different camps on this topic, even within people of a certain height. I'm a tall person who swears by long chainstays, but lots of tall people hate them. So while it makes sense to have size specific chainstays so RC grows proportionately with FC, if they're not adjustable, your CS number's still not going to please everyone. As far as I see it, there are three options for frame manufacturers:
1. Adjustable chainstays with a big range of adjustment. Think of the outgoing Kona Process X, where you could choose 435mm or 450mm. That's a big, immediately noticeable difference, and can actually meet the desires of riders in both camps. I liked this idea. I miss my 10mm of chainstay adjustment on my old Mk.1 Megatower. For Santa Cruz, the swappable dropout/adjustable CS idea debuted with that bike and ended with that bike, once UDH debuted. RIP.
2. Pick a certain type of customer, and cater to that customer when determining chainstay length. Generally speaking, go fast racer-types like longer chainstays for front end grip and stability (and because we're smarter and right). "Fun" seekers, jibby types, and beginners like shorter stays because they're "more flickable" (and because they're wrong). A company can choose who their type of customer is, and cater to them with their chainstay length. For instance, SCOR sponsors Josh Lewis and has always had short stays. By contrast, RAAW is very much a "racer" bike and has always had longer stays. Similarly, while it's true that the new V10 has size-specific and adjustable-length chainstays, they're actually really long across the entire size range, even in the shortest setting. Taking this route is my vote because it builds a clear customer and brand narrative that can drive other decisions, too, like shock tune, internal/external cable routing, hardware accessibility, stack height, etc.
3. Play it safe,split it down the middle, and have a compromise chainstay length for everyone. This is the path I think most manufacturers take. It's never going to be super jibby and it's never gonna be super stable, but your average customer doesn't know the difference, and most of your opinionated riders still don't care enough to rule out a bike just because the chainstay is 6.723mm too short or too long. One big downside to this route is that you're not building a dedicated fan base with a clear customer narrative, which makes it hard to stand out in a rapidly homogenizing MTB landscape. But, the flipside is that you're also not scaring away a big chunk of the market. Lastly, being confident and decisive is scary, so it's way more fun to try to please everyone all the time!
That's a great answer, thank you. I'm in the tall guy short chainstay and I had a process x that I loved before I broke it haha, holding on to it to get it repaired eventually, never got to try the long chainstay mode on it. The bike I got after that was a Norco Sight, which had 440 stays and it felt so off for the longest time. What fixed it for me was putting on a shorter stem, going to a 40mm with a 3 degree rise from the 50mm I ran on the Kona, which was not what I was expecting because the reach on the Kona was 490 where the reach on the Norco was 485. There were other geo changes such as stack height and fork travel between them that would definitely have an effect as well but I felt like my weight was too much on the front wheel and the shorter stem and slightly higher rise fixed it.
I think sized specific is very important, maybe don't have 4 sizes of rear centre, but rather one for S/M and another for L/XL atleast. ...
I think sized specific is very important, maybe don't have 4 sizes of rear centre, but rather one for S/M and another for L/XL atleast.
I'm same height, like my bikes around 490-500mm reach too.
Current bike has 462mm Chainstay, it is amazing for front end grip, with 63 Degree head angle you need a longer CS for flatter corners I find. Another bike I had was similar H/A but CS only 440 and it constantly pushed on flat corners. That chainstay length of 462 is the same across all the sizes, it works great for XL at 505mm reach but imagine that on a small, the CS is longer than the reach! The ride would be interesting.
In saying that, 462 makes manuals and last second pullups off drops rather difficult, I think 450-455 would be perfect IMO.
For my height and centralised riding style, 500mm reach, 455 CS, 660 stack, 63 degree H/A, 77-78 deg STA with a 240mm dropper is heaven. My current bike pretty much ticks all of those.
Good feedback, thank you. I've been thinking about this a lot and using my barebones education, I've wondered if women on the whole would benefit more from a longer chainstay than men would, personal preference not being factored in. Thinking of where the center of mass is on men (around the navel) vs women (at the hips) , women would broadly be loading the bike more towards the rear axle and reducing the force on the front wheel than a man of the same weight and height would. Lengthening the rear end a bit more for a women's design would balance the grip between the front and the rear wheels, and could be tailored to be more in line with how the same bike would grip for a man. Thoughts? I know this isn't the end all be all solution for handling and geo, but I'm looking at it in isolation.
FWIW @Eae903 apparently women's skis are the same as mens, but marked to mount the bindings a few cm more forwards. Apparently because they tend to be a bit more defensive in their posture when skiing, thus weighting the rear of the ski a bit more. Moving the bindings forwards offsets this a bit.
It's not the same with bikes as you have handlebars that also define the position of the hands, but food for thought nevertheless.
I think sized specific is very important, maybe don't have 4 sizes of rear centre, but rather one for S/M and another for L/XL atleast. ...
I think sized specific is very important, maybe don't have 4 sizes of rear centre, but rather one for S/M and another for L/XL atleast.
I'm same height, like my bikes around 490-500mm reach too.
Current bike has 462mm Chainstay, it is amazing for front end grip, with 63 Degree head angle you need a longer CS for flatter corners I find. Another bike I had was similar H/A but CS only 440 and it constantly pushed on flat corners. That chainstay length of 462 is the same across all the sizes, it works great for XL at 505mm reach but imagine that on a small, the CS is longer than the reach! The ride would be interesting.
In saying that, 462 makes manuals and last second pullups off drops rather difficult, I think 450-455 would be perfect IMO.
For my height and centralised riding style, 500mm reach, 455 CS, 660 stack, 63 degree H/A, 77-78 deg STA with a 240mm dropper is heaven. My current bike pretty much ticks all of those.
Good feedback, thank you. I've been thinking about this a lot and using my barebones education, I've wondered if women on the whole would benefit more...
Good feedback, thank you. I've been thinking about this a lot and using my barebones education, I've wondered if women on the whole would benefit more from a longer chainstay than men would, personal preference not being factored in. Thinking of where the center of mass is on men (around the navel) vs women (at the hips) , women would broadly be loading the bike more towards the rear axle and reducing the force on the front wheel than a man of the same weight and height would. Lengthening the rear end a bit more for a women's design would balance the grip between the front and the rear wheels, and could be tailored to be more in line with how the same bike would grip for a man. Thoughts? I know this isn't the end all be all solution for handling and geo, but I'm looking at it in isolation.
Good thought.
But I think longer CS for women is counterproductive in a way, let me try to explain.
The longer the CS the more it loads up the front tyre. Now this is all well and good on a smooth trail, but when it becomes rough, the rider needs to be able to keep themselves up and supported. You tend to run more pressure/compression too in a bike with longer CS as the lever effect is heightened, again I would imagine this is not ideal for women.
The comes lofting the front wheel which takes drastically more strength and effort. Not to mention the increase in wheelbase.
In the right situation a Long CS is fantastic, you do need to manhandle the bike to make drastic changes in direction and it's just a matter of adapting rider style, if you are central on the bike and like to "stand tall" it is a game changer, you simply stand above the Bottom Bracket and carve corners like you are on ski's almost (not that I've ever been skiing lol)
I think the biggest issue with size-specific chainstays are the cost to manufacture. Most major brands use the same rear triangle carbon molds across all sizes to reduce the massive upfront costs of carbon molds. This shuts down R&D, marketing, and customization before the conversation can even begin.
This is why I think what Forbidden does is brilliant- they vary their chainstay lengths across sizes while still using the same rear triangle by varying the main pivot placement on the front triangle. The front triangle has to vary by size anyways, and the links are machined, so its an excellent way to 'cheat' and provide varying rear-center lengths by size.
The other option of just having adjustable dropouts is also a good solution to allow the reuse of rear-triangle molds across sizes, but it adds complexity, weight, (some) cost, user error, and alters the rear suspension kinematics.
You could also be like Specialized and copy someone else's homework and the patent it as your own.
How are y'all stress testing? I know Fusion and other software have FEA capabilities but what are the tests you run? I was trying to find standards for a DH bike but haven't had much luck
Aren't the Ancilloti frames a single pivot? The new demo and enduros are a Horst link with the pull arm on the bottom for driving the shock.
You could ask EFBE for the loads for category 5...
It's the pull link under the bb they are trying to patent, or rather the kinematics and adjustability they can get from it.
Sooo when are you actually coming up with a name for brand and finally starting to build these beauties and sell them? 😄 Even mk1 and mk2 were pretty good, now this, what is it - mk5???, is super dialed!
If you can get your hands on a broken dh frame or fork- cut it up and measure wall thickness etc. back out the strength that way.
could probably measure fork tube ID/OD without damaging it.
that would at least give a ballpark number
I ran 1.5ODx .056 wall 4130 downtube on a dh bike. Never broke or cracked it.
Lots of great info on https://forum.customframeforum.com
No current plans to build for sale.
MK5 is in the works. Take Mk3 and Mk4 and smash them together you get Mk5, I need to finalize some flat sheet metal design for the shock tunnel and get that off to Send Cut Send.
When talking frame design for me the question is what are the design goals? I started making my own frames when what now is modern geo wasn't available so I was building slack n long when that wasn't a think for trail/enduro/am bikes. Now I could find pretty close to my preferred geo on a commercial bike. For me now it's more about honing in on the right combo or AS/AR/LR. I've done really progressive, linear, and unique S shape LR. The next one is mid/lowish progression with and end stroke ramp up in progression. The change in end stroke will function as mechanical bottom out control on the last 15mm of travel. The same layout is also going to allow me to build a 24" wheeled version for my kids that allows for adjustment from near flat linear to that same mid progression as above, and fit a bottle in the mainframe.
I think they were referring to how Spec patented the Horst link which they did not invent.
I thought spesh bought the patent from the inventor and then made it exclusive to them, which while pretty lame on spesh and for the companies who were liscencing it from the original inventor, isn't illegal.
That’s a solid down tube! Was it 4130?
It looks to me like .9mm or 1.2mm x 38.1mm is pretty common for 4130 on a down tube. I guess it also depends if the DT has a shock mount on it and needs to be beefed up a bit.
@bradlowery Here’s some info on testing with EFBE.
https://www.efbe.de/pdf/Test-order-1-frame.pdf
https://www.efbe.de/index.html#zwei
No info there. If you want loads, it's 500 eur per component which is also a credit for any tests performed later. So in case you go forwards with production, it's basically free.
Pole dropped a bunch of the test numbers in this article on Pinkbike back in 2021.
https://www.pinkbike.com/news/pole-voima-emtb-passes-efbe-tri-test.html
I wonder what happened with the NDA you have to sign to get the numbers...
Yes but it was a dh bike and it had the shock mount, and I didn’t want to worry.
On previous projects I’d used 1.5x.049 4130 for the DT. I cracked one due to bad gusset design.
that’s always my concern with home made bikes- testing is always by the rider.
A lot of the EFBE stuff is based on CEN bike testing standards, which you can find numbers on if you dig around.
Many of the big companies have frame testing standards that they have developed on their own as well which you're not going to get any numbers on.
Specialized had a Demo fully strain gauged and wired up that they had Matt Hunter doing Whistler laps on. It resulted in some very interesting data and led to the development of a completely new bottom out fatigue test for bigger full suspension bikes.
But Specialized also has a mutli million dollar test lab setup in Morgan Hill with half a dozen MTS test beds. That's why places like EFBE exist, good testing equipment is very expensive.
That place Neko used in Canada for Frameworks seemed like they know what they are doing.
I think the main benefit of EFBE is the grade 5 (DH) and grade 4 (trail) & co standards as it gives you an indication of how strong the frame is. If it's internal you don't have the information of how it compares to other companies.
But most of the biggish brands have their own testing labs in some way or shape.
was it this shape? That was my 4th or 5th frame (I cant remember) in about 18 months. They would all crack at the BB/seat tube junction. I literally got 1 day out of some of those frames. So Sexy looking, but also made out of wet cardboard.... 135mm rear hub and about as progressive as a soggy noodle. Specialized were fantastic though, I'd crack it on the weekend, show the bike shop on Monday morning and by Wednesday would have another frame. It was always new bike day lol
No, the old Demo with 27 seat stays.
The Gwin version was a disaster in many ways.
It's sad when a company knows a product will fail, but keeps going forward with it. Like what happened with the Hubble Space Telescope and why it is now used an example of what not to do in every college level project management course.
I remember your DH frames. Very cool stuff!
I’ve been using .9mm on these down tubes but now I’m thinking of going up to 1.2mm. The lower shock mount is half on the bb/st and half at the base of the dt. I was thinking I could go lighter on the dt due to that.
Here's a question, how do you feel about size specific chainstays or chainstay length in general? I like my chainstays to be about 435mm long, paired with a 480-490 reach, and I'm a 6'1 man with a long torso, but there has been a big push for longer stays for a "more balanced feel". What are your thoughts?
I think sized specific is very important, maybe don't have 4 sizes of rear centre, but rather one for S/M and another for L/XL atleast.
I'm same height, like my bikes around 490-500mm reach too.
Current bike has 462mm Chainstay, it is amazing for front end grip, with 63 Degree head angle you need a longer CS for flatter corners I find. Another bike I had was similar H/A but CS only 440 and it constantly pushed on flat corners. That chainstay length of 462 is the same across all the sizes, it works great for XL at 505mm reach but imagine that on a small, the CS is longer than the reach! The ride would be interesting.
In saying that, 462 makes manuals and last second pullups off drops rather difficult, I think 450-455 would be perfect IMO.
For my height and centralised riding style, 500mm reach, 455 CS, 660 stack, 63 degree H/A, 77-78 deg STA with a 240mm dropper is heaven. My current bike pretty much ticks all of those.
I assume that you've all been watching these Frameworks videos. Here's the latest...
https://www.youtube.com/watch?v=nZADPtNg_Js
Great question! The tough thing about chainstay length is that there are very different camps on this topic, even within people of a certain height. I'm a tall person who swears by long chainstays, but lots of tall people hate them. So while it makes sense to have size specific chainstays so RC grows proportionately with FC, if they're not adjustable, your CS number's still not going to please everyone. As far as I see it, there are three options for frame manufacturers:
1. Adjustable chainstays with a big range of adjustment. Think of the outgoing Kona Process X, where you could choose 435mm or 450mm. That's a big, immediately noticeable difference, and can actually meet the desires of riders in both camps. I liked this idea. I miss my 10mm of chainstay adjustment on my old Mk.1 Megatower. For Santa Cruz, the swappable dropout/adjustable CS idea debuted with that bike and ended with that bike, once UDH debuted. RIP.
2. Pick a certain type of customer, and cater to that customer when determining chainstay length. Generally speaking, go fast racer-types like longer chainstays for front end grip and stability (and because we're smarter and right). "Fun" seekers, jibby types, and beginners like shorter stays because they're "more flickable" (and because they're wrong). A company can choose who their type of customer is, and cater to them with their chainstay length. For instance, SCOR sponsors Josh Lewis and has always had short stays. By contrast, RAAW is very much a "racer" bike and has always had longer stays. Similarly, while it's true that the new V10 has size-specific and adjustable-length chainstays, they're actually really long across the entire size range, even in the shortest setting. Taking this route is my vote because it builds a clear customer and brand narrative that can drive other decisions, too, like shock tune, internal/external cable routing, hardware accessibility, stack height, etc.
3. Play it safe, split it down the middle, and have a compromise chainstay length for everyone. This is the path I think most manufacturers take. It's never going to be super jibby and it's never gonna be super stable, but your average customer doesn't know the difference, and most of your opinionated riders still don't care enough to rule out a bike just because the chainstay is 6.723mm too short or too long. One big downside to this route is that you're not building a dedicated fan base with a clear customer narrative, which makes it hard to stand out in a rapidly homogenizing MTB landscape. But, the flipside is that you're also not scaring away a big chunk of the market. Lastly, being confident and decisive is scary, so it's way more fun to try to please everyone all the time!
That's a great answer, thank you. I'm in the tall guy short chainstay and I had a process x that I loved before I broke it haha, holding on to it to get it repaired eventually, never got to try the long chainstay mode on it. The bike I got after that was a Norco Sight, which had 440 stays and it felt so off for the longest time. What fixed it for me was putting on a shorter stem, going to a 40mm with a 3 degree rise from the 50mm I ran on the Kona, which was not what I was expecting because the reach on the Kona was 490 where the reach on the Norco was 485. There were other geo changes such as stack height and fork travel between them that would definitely have an effect as well but I felt like my weight was too much on the front wheel and the shorter stem and slightly higher rise fixed it.
Good feedback, thank you. I've been thinking about this a lot and using my barebones education, I've wondered if women on the whole would benefit more from a longer chainstay than men would, personal preference not being factored in. Thinking of where the center of mass is on men (around the navel) vs women (at the hips) , women would broadly be loading the bike more towards the rear axle and reducing the force on the front wheel than a man of the same weight and height would. Lengthening the rear end a bit more for a women's design would balance the grip between the front and the rear wheels, and could be tailored to be more in line with how the same bike would grip for a man. Thoughts? I know this isn't the end all be all solution for handling and geo, but I'm looking at it in isolation.
FWIW @Eae903 apparently women's skis are the same as mens, but marked to mount the bindings a few cm more forwards. Apparently because they tend to be a bit more defensive in their posture when skiing, thus weighting the rear of the ski a bit more. Moving the bindings forwards offsets this a bit.
It's not the same with bikes as you have handlebars that also define the position of the hands, but food for thought nevertheless.
Good thought.
But I think longer CS for women is counterproductive in a way, let me try to explain.
The longer the CS the more it loads up the front tyre. Now this is all well and good on a smooth trail, but when it becomes rough, the rider needs to be able to keep themselves up and supported. You tend to run more pressure/compression too in a bike with longer CS as the lever effect is heightened, again I would imagine this is not ideal for women.
The comes lofting the front wheel which takes drastically more strength and effort. Not to mention the increase in wheelbase.
In the right situation a Long CS is fantastic, you do need to manhandle the bike to make drastic changes in direction and it's just a matter of adapting rider style, if you are central on the bike and like to "stand tall" it is a game changer, you simply stand above the Bottom Bracket and carve corners like you are on ski's almost (not that I've ever been skiing lol)
I think the biggest issue with size-specific chainstays are the cost to manufacture. Most major brands use the same rear triangle carbon molds across all sizes to reduce the massive upfront costs of carbon molds. This shuts down R&D, marketing, and customization before the conversation can even begin.
This is why I think what Forbidden does is brilliant- they vary their chainstay lengths across sizes while still using the same rear triangle by varying the main pivot placement on the front triangle. The front triangle has to vary by size anyways, and the links are machined, so its an excellent way to 'cheat' and provide varying rear-center lengths by size.
The other option of just having adjustable dropouts is also a good solution to allow the reuse of rear-triangle molds across sizes, but it adds complexity, weight, (some) cost, user error, and alters the rear suspension kinematics.
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