Accessibility Widget: On | Off

The Internet Was Wrong: Short Chainstays Suck*

Create New Tag

2/11/2019 8:36 AM

Allen_Gleckner wrote:

Seems to me there’s little doubt that a balanced bike is faster for racing and long gnarly, fatiguing descents. The more interesting question for me is for the non racer that wants to shred, slash turns, manual, but also ride flat turns fast and go fast generally, is a longer CS better and if so, how long. I’m 6’2” and only have short CS bikes (Demo, Process, DJ). The process (485 reach, 426 CS) is super fun. I was also just in Bellingham and rode an XL Patrol for a few days and it was rad and felt plenty stable in the steep gnar. Granted the longest descent was probably 6 - 10 mins.

Jeff, you’ve been clear your point is purely about racing and theoretically it makes sense to me. But wondering about us non racers who like to go fast but play too, are there trade offs and when do those happen. I wish i had the opportunity to try something good with longer CS to get a sense

There are downsides, which is why I kind of started this.

Lets go back in time before the era of long front centers. In those days, everyone was trying like hell to get the shortest chainstays possible on a bike. This actually made some sense for two reasons.

First, when you have a super short reach, super short chainstays actually matched pretty well. Second, and more importantly, it made everyone and their mom feel more Sam Hill meets Sam Blenkishop Blenkinsop on a bike. Its far easier to cutty. Its far easier to loft your front tire. Its far easier to "play" with the terrain with a compact rear end.

...all of a sudden all these intermediate level riders are doing things they never did before. And that felt fun.

So yeah, shorter chainstays do often equal "more fun". Its hard to deny that!

If your skills are higher, and strength higher, a longer rear center isn't too hard to deal with. But make no mistake about it, manualing is harder. Doing a cutty is a lot harder. The bike is just more locked in, for lack of a better word.

Ironically, back in the short chainstay, short front center era, I remember everyone trying like hell to slam their bike to the ground. Funny enough, longer bikes have a similar effect as lowering the bike, so its ironic to me we've solved this problem through different means.

Overall, a long FC with long RCs are not going to be popular as they'll be something only a few freaks (like myself) really want. Maybe slightly longer stays will become a thing, but to the point I'm thinking will have a drastic improvement on handling while racing, I doubt it. It will make the bike feel more planted, more neutral, and more...boring. Outside the race course it just won't be something a lot of dudes love. Kind of how a race ski is awesome between the gates but not so much fun...anywhere else. Maybe not that level of polarization, but I don't think these drastically longer rear ends will have the market, the same way a lot of go-fast gear kind of gets relegated to the freak show "bucket" of a sport.

|

2/11/2019 9:35 AM

Thanks, Jeff. That's really interesting and makes sense. Would you see yourself riding the really long RC race setup all the time, or having a "play" bike too? Or is your riding style such that you're happy to have the fastest setup all the time?

|

2/11/2019 9:46 AM

Allen_Gleckner wrote:

Thanks, Jeff. That's really interesting and makes sense. Would you see yourself riding the really long RC race setup all the time, or having a "play" bike too? Or is your riding style such that you're happy to have the fastest setup all the time?

I'd absolutely stick one bike. One thing I know about myself is the "best" bike is never the best if you keep monkeying with it so much you aren't familiar with it. I also don't think the bike will be completely "not-playful", especially once you adapt to it. I won't be "jibbing" stuff like the 50:01 boys, but I don't do that anyway.

Sticking to one geometry through a season is paramount. Otherwise you are re-learning how to ride everytime you go back and forth.

There are guys who can do this with ease. I'm not one of them.

|

2/11/2019 11:34 AM
Edited Date/Time: 2/11/2019 11:35 AM

I don't really take offense if Ninjichor wants to call the style of riding I'm aiming for, "defensive." That's certainly not how a spectator would describe it after watching me ride by on-course. I ride at the limit, and I'm looking to push the limit with a bike that requires less wasted mental & physical energy from me just to keep the front wheel from pushing out.

You could just as easily call Hill, Gwin and Minnaar "defensive" riders. I am in no way comparing myself to them, but they represent a north star for me in terms of maintaining a neutral positioning on the bike while the bike and line choice does all the talking. Contrasted with riders like Blenki, Brannigan, et al who "look" like they're riding "aggressively" while going slower, making more mistakes and hitting the deck with some regularity. I want less flare and more speed.

I don't know if I share Jeff's cynicism about how popular a longer RC bike would be... True, mucking around on your bike would be harder. But speed is addictive, and every mountain biker likes going fast, especially if they feel safer and more comfortable while doing it. The question is simply whether some percentage of consumers would be willing to sacrifice stupid pet tricks for more speed. I don't know the answer at large, I just know I certainly would.

|

2/11/2019 12:01 PM

Interesting this thread came back to life....could it be because the bikes have continued to get even longer?

I thought the Vorsprung video was good and backed up my impression that more average height riders look better balanced on bikes with the right FC/RC proportion.

Speaking as a tall dude (6’2”) I do think it’s a bigger problem for taller guys as the balance goes out the window with short Chainstays. Saying that I’ve found that at higher speeds short reach and short Chainstays is horrendous (rider becomes an upside down pendulum).

I have had CS between 415 and 450 on several bikes and I will classify my views in 3 ways.
(1) Climbing - in general short CS is a mare for tall guys as max climb angle is shallow even with steep ST.
(2) Flat - in general short isn’t great at speed as still too much weight on rear wheel. Don’t like long CS for drops/jumps with tricky entry.
(3) Descending - long CS is fine on wider DH tracks and at very high speeds (Mega 290 with 450CS is insanely stable) but really dodgy on tight/narrow Enduro style descents.

So for:

(1) trail/AM bikes a balanced proportion is good and CS needs to increase with reach.
(2) for Enduro the bikes need to be more compact and nimble so generally short/medium CS and not huge reach. Probably slightly higher FC/RC as a result?
(3) For DH bikes high speed implies longer CS. (Also applies to races like Megavalanche).

EveryOne is different but for what it’s worth
Here’s my references

188cm height
Arms average length
Legs long / Torso short
Preferred Reach range 480-500
Preferred CS range 430-450
Preferred stack range 620-650 (bar rise 35-50)
Bars 800 / Stem 40-50

|

2/11/2019 1:15 PM

@rubberduck

Just wanted to throw two more thoughts in...

1) 10 years ago people NEVER would have thought we could ride the geo we currently ride on trail. People would say "how can you get it to corner", "it only wants to go straight", "29" wheels suck" etc etc. Its funny how suggestible the brain really is. That is a big part of the reason things take so long to develop, the demographic has to go in baby steps to wrap their head around what is possible or what works, leaving yesteryear's preconceived notions at the door.

What I'm getting at is I could see these bikes feeling unwieldy at first, but actually feeling really good on tighter trails as a bigger guy once you get used to it. I've watched dirt bikes with crazy long wheelbases smoke some of the tighter trails here at home, so I think its more possible than we think. I also think we may find a happy medium, with guys our size on 475-490mm reaches, but with RCs that are closer to 460mm. Long bike, for sure, but maybe not the 510+mm reaches we are seeing on certain XLs now.

2) Longer rear center actually helps the bike climb IMO. You nailed this one. Longer chainstays just keeps the front end down, even if you have a stupid slack head angle.

|

2/11/2019 2:13 PM

jeff.brines wrote:

@rubberduck

Just wanted to throw two more thoughts in...

1) 10 years ago people NEVER would have thought we could ride the geo we currently ride on trail. People would say "how can you get it to corner", "it only wants to go straight", "29" wheels suck" etc etc. Its funny how suggestible the brain really is. That is a big part of the reason things take so long to develop, the demographic has to go in baby steps to wrap their head around what is possible or what works, leaving yesteryear's preconceived notions at the door.

What I'm getting at is I could see these bikes feeling unwieldy at first, but actually feeling really good on tighter trails as a bigger guy once you get used to it. I've watched dirt bikes with crazy long wheelbases smoke some of the tighter trails here at home, so I think its more possible than we think. I also think we may find a happy medium, with guys our size on 475-490mm reaches, but with RCs that are closer to 460mm. Long bike, for sure, but maybe not the 510+mm reaches we are seeing on certain XLs now.

2) Longer rear center actually helps the bike climb IMO. You nailed this one. Longer chainstays just keeps the front end down, even if you have a stupid slack head angle.

Totally agree, but I'd like to ensure we separate reach from front-centre. I'm being particular about this because I'm a fan of very steep seat tube angles, which require a long reach to provide adequate room when seated, but I don't think a super long front-centre is right for everyone. The two variables can be separated and it's important to do so.

At 183 cm, I like a reach over 500 mm and would prefer to test front-centre length and weight balance by varying head angle and offset (and maybe rear-centre length) than by reducing reach.

|

2/11/2019 2:56 PM
Edited Date/Time: 2/11/2019 3:36 PM

There is quite the heated debate going on here. I am very happy about everyone coming out with his ideas/opinions after Vorsprungs Video on that topic. There seems to be an obvious need to discuss this.

Let me try to summarize what looks to be consensual facts so far:
- we would like to balance out FC and RC
- we went through extraordinary changes on that subject in recent times
- we would love to have a factor that scales fine and is representative for a bikes general behavior
- we would love to have an idea where to put ourselves in that factor range according to our riding style/goals

First i want to give credit to Steve from Vorsprung for making this topic as accessible as he did and being particulary open for discussion, even though it derailed pretty quick. I think he is scientist enough to not claim any general validity and he never did. His factor might not scale as nice but i think hes on the right track, especially with his disctance from BB to 55:45 distribution point and looking into balance at 50% travel. If we are reducing the complex dynamics of a fullsuspension bike to a balance point, which i think is absolutely valid, we should look at the very middleground where everything is happening around. To me 55:45 balance at 50% travel is a perfect assumption because from here we go to all othere extremes that happen while riding. Its a choice nonetheless.
The factor itself should scale fine to different bike/rider sizes, which is a problem when looking at (static)FC/RC ratios. Ninjichor suggested to use the bb to 50:50 balance point distance, but why not use distance to 55:45? It´s actually closer to what we are looking for and it scales pretty fine.

Edit:
actually after just modelling up a few fast and easy sketches with bigger reach differences than i normally look into, i don´t think my proposal nor ninjochors are scaling that well at all.
Fixed ratio scaling delivers far more reasonable results. If interessted i can post some screenshots of examples tomorrow.







|

2/11/2019 3:34 PM
Edited Date/Time: 2/11/2019 4:40 PM

I cannot unlink CS length from the FC or WB. This is a vital relationship that determines the bike's weight distro bias. Steve@Vorsprung's video should've emphasized how important this is. Reach is a different matter.

The main point on which I disagree with Steve's work, is where he plotted the CoG. He plotted his almost directly above the BB. I see it changing, based on how the rider positions themselves with their hips and upper body.

Photo
- the distance behind the BB varies, and the rider CoG varies, depending on how a rider is positioned on the bike. The bike has a weight bias preference, set by the RC-FC relationship, and it's up to you to not disrupt that balance if you want it to behave.

I suggested the formula, wheelbase/2 - CS length, to show how far forward the center point is in front of the BB. To make use of this, to find a bike that naturally puts your "neutral" position into its balance point, you need to define this position. If you picture a rider using a "heavy feet, light hands" approach to handling, will it be like a mogul skiier perhaps? People find it hard to break away from the roadie position, thinking that's the proper position, especially if you train your endurance on a road bike, or XC bike with matching position, like Nino Schurter.

Photo
- generally, the bike's centerline should bisect the seated position evenly, but it's a problem when you want to have a different standing position. What if you want one that's more forward of the seated position, or behind it, rather than hovering over it?

When I went out to design my custom frame, I knew I wanted a more forward position. I just didn't know how much was the limit, or if there were any drawbacks besides not being able to go back to slack STA. When I pedal out of the saddle, it's often with my hips forward of the saddle (only done when traction was not an issue). When I descend out of the saddle, it was often behind the saddle or hovering over it (if I didn't, I'd be having a bad time falling). When I was climbing, it was easier if I relaxed and extended my arms, pushing away from the front of the bike. This was because the centerline of the bike was so close to the BB (taller folks wanting longer CS have a problem with the centerline being too far away).

Photo
- illustration of the bike's centerline, when on a slope, with a rider shifting their weight accordingly to not disrupt the bike's weight distro balance.

In essence, I see everything in terms of rider CoG in relation to the bike's center point. This is not to create an ideal weight distro bias, but to determine where you should position your body's CoG in order to not disrupt the bike's delicate weight distro bias. If you draw a line along the force of gravity through the center point, the rider's CoG should be a certain amount behind that depending on where the BB is. If you don't do this, you end up falling. A long wheelbase makes the bike's weight distro less sensitive (widens the bike's sweet spot).

*deletes a bunch of wordy explanations, hoping this is more easily digestible*

To try and sum up why this post is significant, as it might look like me repeating the same stuff to some, I'd like to outline the difference in perspective/approach:

- Steve@Vorsprung looked to existing designs, including some slack STA designs, and sought to show how important weight balance distro was, showing the rear:front weight distro. He made a biased conclusion, comparing to what he subjectively thought was ideal, his own bike, and why his not-so-impressive test ride on a Pole served as confirmation (which weren't totally geo related).

- I looked to make a new personal definition of "neutral" position, and decided that my upright relaxed standing pedaling position was it. I took its CoG, measuring how far my hips were behind the BB, and balanced everything else around to it. I steepened the STA and lengthened the reach to make the seated position's CoG match (plus have the centerline bisect it). The dream was to be able to corner/plow from the same position I pedal from, squeezing pedal strokes between corners, rather than trying to pedal from behind the back and end up holding onto the bars tightly. Eliminating the CoG movement when switching from a seated position, to standing, eliminated the compromise of picking one or the other to optimize for.

Essentially, fully adapt the bike to the rider, and their preferred positioning. Your body doesn't change, but the bike can. Can get the same position whether you're on a 1300+mm wheelbase long travel bike, or a 1150mm wheelbase short travel bike, if you get the rider's CoG and BB distance from the centerline matched up (accounting for sag), to get weight bias dialed. Working with percentages doesn't achieve this as accurately--Steve seemingly just did that to calc the weight distro bias.

Reach and STA should be spec'd to get the rider into the balanced position when standing/seated. Can't just name off #s and expect it to work for just any bike. All the dimensions need to be designed holistically as a complete system, with the rider included and their position factored in. This falls in line with my belief that what makes a modern design better, is how they keep adding in new factors to account for in the design, solving issues that caused unnecessary compromises.

|

2/11/2019 10:53 PM
Edited Date/Time: 2/12/2019 3:34 AM

Ok so yes the FC and Reach are different however from a practical standpoint similar style bikes (similar travel, HA and same reach) have only a few MM of extra length. In context that’s less than 0.5% of FC and less 0.25% of WB. Given we are discussing FC/RC ratios of 50/50 through to 60/40 I think this is in the category of super fine tuning.
I cannot see me getting on with CS much over 440 unless it’s on fast wide DH tracks and nor (for my size) much need either on AM or Enduro trails.
The CS length is more important than the FC/RC ratio for my regular (non-DH riding). It drives how nimble the bike is descending and how it climbs for me.
I realised this after testing a bunch of bikes. Saying that I don’t want FC/RC balance miles out either.

There’s also the stem issue....I seem to find 35mm too short and prefer a “real effective stem length” of at least 20mm to keep weight on the front wheel

|

2/12/2019 9:53 AM

Just a fun tip - anyone who wants to try out longer chainstays without buying a new bike, you can.

Just move your cleat as far back on your shoe as possible. Hell, even drill new holes like a certain EWS champion does.

I did this last year and found a noteworthy gain in my lap times. You can actually very the length pretty effectively with this "test".

|

2/12/2019 10:28 AM

jeff.brines wrote:

Just a fun tip - anyone who wants to try out longer chainstays without buying a new bike, you can.

Just move your cleat as far back on your shoe as possible. Hell, even drill new holes like a certain EWS champion does.

I did this last year and found a noteworthy gain in my lap times. You can actually very the length pretty effectively with this "test".

Very interesting point.

I experimented with this a few years back, and permanently changed my riding balance and style. But I never looked at it as effectively lengthening the amount of bike behind my center of gravity. I didn't realize that's what I was doing.

I ride flats and experimented with Catalyst pedals at first and then adopted that foot placement with normal pedals. I've now adapted to riding with the axle somewhere between true mid-foot and the ball (~the forward half of my foot arch).

The effects were immediately noticeable and much more drastic than I expected them to be. The bike was far more stable, especially through rough/steep, but needed a lot more input to snap through turns. At first I was basically hitting every corner late/wide. I also had to learn to jump differently-- I had to compress and kick with more hamstring and heel than I was used to (because you're basically removing the calf and ankle from the equation).

I would say jumping and sprinting are the two areas where rearward pedal placement is not an advantage, but the overall gains in stability and traction were worth it. You're also much stronger in general pedaling and climbing, I just didn't care as much about those things.



|

2/12/2019 7:45 PM
Edited Date/Time: 2/12/2019 7:52 PM

Photo

Photo

RC length: 452 mm.
FC length: 737mm
Ratio is about 39:61.


Possible build: 79er with a 29" Lyrik 170mm fork with a short offset; slackens both the head angle and seat angle; rear shock will be an M/M tune Super Deluxe

Purpose: Enjurow plough bike

Bad idea? cool
|

2/12/2019 8:54 PM

Verbl Kint,

Yes, and I strongly encourage it! Just be sure to report back on your findings.

|

2/13/2019 2:40 AM

Verbl Kint wrote: Photo

Photo

RC length: 452 mm.
FC length: 737mm
Ratio is about 39:61.


Possible build: 79er with a 29" Lyrik 170mm fork with a short offset; slackens both the head angle and seat angle; rear shock will be an M/M tune Super Deluxe

Purpose: Enjurow plough bike

Bad idea? cool

A 79er? Wow those are big wheels!

|

2/13/2019 3:03 AM

jeff.brines wrote:

Just a fun tip - anyone who wants to try out longer chainstays without buying a new bike, you can.

Just move your cleat as far back on your shoe as possible. Hell, even drill new holes like a certain EWS champion does.

I did this last year and found a noteworthy gain in my lap times. You can actually very the length pretty effectively with this "test".

I’ve not thought about this from the perspective of lengthening the CS but I’ve ridden with this set up and it does help high speed stability and when pushing against the pedals over steep gnar you don’t overstretch ankles on big hits. Just a trade off with ankle flex but that can be fine tuned as well so I’ve taken the view it’s worth tinkering with.

|

2/15/2019 8:33 AM

@Verbal Kint That bike would be immediately crossed off my own list. To balance out a RC of 452mm on an Enduro plow bike, I'd want a FC of 865. To balance out a FC of 737mm, I'd want a RC of 415.

I don't go by FC or RC ratio. Not sure what R-M-R sees in it, but its WB puts it into trail bike territory.

|

2/15/2019 11:50 AM
Edited Date/Time: 2/16/2019 11:36 PM

ninjichor wrote:

@Verbal Kint That bike would be immediately crossed off my own list. To balance out a RC of 452mm on an Enduro plow bike, I'd want a FC of 865. To balance out a FC of 737mm, I'd want a RC of 415.

I don't go by FC or RC ratio. Not sure what R-M-R sees in it, but its WB puts it into trail bike territory.

Regarding the actual bike - turning that short, skinny-chainstayed thing into a chopper with mismatched wheels and suspension - it's going to be awful. The rear will be difficult to manual or flick, the front will dive into oblivion if it bottoms out, the climbing ergonomics will feel like the worst examples from the early 2000s ...

I'm just a fan of weird experiments, especially when they're being done by someone else.

|

2/17/2019 6:36 AM

Photo

https://evolvebikes.ca/collections/nv-carbon/products/alpha-29

Bike looks fine to me. Reviews have all been excellent so far.

Posting it here because it has the longest chainstays of any retail S or M sized enduro bike I've seen.
|

3/10/2019 9:50 PM

Verbl Kint wrote: Photo

https://evolvebikes.ca/collections/nv-carbon/products/alpha-29

Bike looks fine to me. Reviews have all been excellent so far.

Posting it here because it has the longest chainstays of any retail S or M sized enduro bike I've seen.

Which reviews? I can find none so far.

(Although this is a Dengfu open mould frame, and I'm sure I can find a review of that if I look hard enough).

Ninjichor-- I still don't understand what you're actually looking for or where your numbers are coming from, with respect to a balanced bike. The numbers on this bike look great to me. Basically like what I'd expect if Nukeproof made a trail bike.

|

3/11/2019 1:37 AM
Edited Date/Time: 3/11/2019 2:00 AM

Observe:

Photo
A. Predicted Dengfu riding position

Photo
B. Sam Hill on Med Mega 27.5

Photo
C. Modern short CS bike in L

When you are at your limits of traction and stability, you better have your body positioned properly, if you don't want to suffer front or rear wheel traction loss. The CS to WB proportions dictate where the rider needs to be to get a certain weight distro over the wheels...

The balance I'm looking for is closer to C. Your numbers say you want A, but your mind says you want B. Richie Rude on a M SB150 is somewhere between B and C. I'm guessing that those on XL are beyond C, and are needing to stick their foot out on turns, wanting to dial it back to something more like B.

Rider more rearward vs rider slightly rearward vs rider more central (vs rider forward/aggro, head forward of the bars).

|

3/11/2019 1:52 PM
Edited Date/Time: 3/11/2019 2:03 PM

ninjichor wrote:

Observe:

Photo
A. Predicted Dengfu riding position

Photo
B. Sam Hill on Med Mega 27.5

Photo
C. Modern short CS bike in L

When you are at your limits of traction and stability, you better have your body positioned properly, if you don't want to suffer front or rear wheel traction loss. The CS to WB proportions dictate where the rider needs to be to get a certain weight distro over the wheels...

The balance I'm looking for is closer to C. Your numbers say you want A, but your mind says you want B. Richie Rude on a M SB150 is somewhere between B and C. I'm guessing that those on XL are beyond C, and are needing to stick their foot out on turns, wanting to dial it back to something more like B.

Rider more rearward vs rider slightly rearward vs rider more central (vs rider forward/aggro, head forward of the bars).

Ah, now I get it. You just want the bike that we're all saying we don't want.

Good news for you: every single bike being made is closer to 'C' than it is to 'B', in your examples.

I think you're still wrong in telling me what I want, however:

- The Nukeproof bikes do have the balance I'm looking for. I don't want 170mm of travel. I am eyeing a used SB5.5 and a Stumpjumper 29 to test ride soon, as both of these bikes are longish in the stays (437) and short in the front-center. They're too short in the front, but I want to learn how much that matters vs working less for more front wheel traction. I'd rather have a progressive, long bike with an even longer chainstay, so that Dengfu looks interesting, although I bet I'd hate it for other reasons.

- Why on earth would a long CS trail bike put you in the position of that rider during a lean? She's doing 30-40mph in a wind tuck, hiding behind a dual crown fork with a stack height of probably 620mm, and not turning a corner. Whatever point you're trying to make, that was a bad example.

- What numbers suggest I want a DH bike? almost no DH bike is balanced front to rear in the way we've discussed here, due mostly to the head angle and long fork. Some are just designed that way (Devinci, Demo) and most are just getting longer and slacker in the front, like everything else. That trend is worsening due to higher speeds/lower technicality of DH racing at tractor built bike parks in the past 5-10 years.



|

3/11/2019 2:53 PM

I'm confused by how my post could be read so different from its literal wording. Pay attention to the caption under A, and relate it to the last line in the post. It's all about rider positioning, and why it must adapt that way to the geo.

This thread has answered the question regarding why the Dengfu geo will put you into the position of A in a corner, repeatedly. Simply put, it's because the wheels are essentially being moved rearward relative to the BB, compared to a modern bike. The "balance/stable" point of the bike also goes rearward. If you don't also shift body weight rearward, you're going to have a lot of weight on the front, making the front wheel risk stalling out if it hits an obstacle it can't roll over, possibly leading to an OTB.

How about this picture:

Photo

|

3/11/2019 3:13 PM
Edited Date/Time: 3/11/2019 3:14 PM

I can say with full confidence that what is happening in photo example 'C' has absolutely nothing to do with whether or not the front or rear center of the bike is or isn't X dimension.

What's happening in that picture was done purely for the sake of the photo, and 100% intentional. The photographer was positioned in precisely the spot he is due to the rider knowing what the photo needed to look like and how the rider should be positioned on the bike.

I say this in full confidence because it's me.

wink

|

3/11/2019 3:36 PM

Can you confirm what bike it is and what size? I presumed it was a SBG transition patrol in size L.

I'll find a replacement that shows central positioning I guess. Hard to find examples...

Here's one that shows behind-the-saddle positioning: https://bikerumor.com/2018/09/27/2019-norco-fluid-fs-an-all-new-affordable-aluminum-trail-bike/

The Dengfu resembles the 2014 Intense Carbine: https://www.vitalmtb.com/photos/features/2014-Intense-Carbine-29,6782/2014-Intense-Carbine-29,70481/sspomer,2

The screengrab in my last example was from a Nate Hills Best of Followcam friday '16 video.

Getting desperate finding someone cornering hard with a central position:

Photo
- Going too fast to be caught on film apparently...

|

3/11/2019 4:23 PM

2016 Patrol C size L.

The positioning of the rider has to do with the confidence and aggression the person is riding with. A confident rider is going to achieve this unicorn riding position you're referring to whether they are on a bike with a 420 or 450mm CS.

The geometry of a bicycle helps, but I think what you're referring to has more to do with the rider than the bike.

|

3/11/2019 5:33 PM
Edited Date/Time: 3/11/2019 5:46 PM

ride wrote:

2016 Patrol C size L.

The positioning of the rider has to do with the confidence and aggression the person is riding with. A confident rider is going to achieve this unicorn riding position you're referring to whether they are on a bike with a 420 or 450mm CS.

The geometry of a bicycle helps, but I think what you're referring to has more to do with the rider than the bike.

I think this is correct. Geometry does have an influence on position, but moving the centre of mass an inch isn't going to change a rider's body position as much as the rider's riding style.

Skiers have known this for decades. A high level racer will always have a distinctive body position when carving, whether on race skis with the bindings mounted considerably behind the midpoint or a twintip with a nearly centered mount, while a nervous beginner will be leaning back even if the bindings are mounted on the tail.

I briefly swapped my bike (CS: 440 mm, HT°: 64.5°, reach: 505 mm) with a friend's old-school nightmare (CS: 445 mm, HT°: 67°, reach: ~370 m). I rode a little farther back, but my balance was pretty squarely over my feet on both bikes. The main difference wasn't position, but confidence - so much confidence! Terrain and speeds that were terrifying on his bike were almost boring on mine.


P.S. I'm not convinced the guy in Photo C is actually riding; it looks like a posed photo.
Photo

|

3/11/2019 5:47 PM

What was so terrifying about your friend's bike? What was the risk? Placing the front wheel improperly and going OTB?

|

3/11/2019 6:11 PM

ninjichor wrote:

What was so terrifying about your friend's bike? What was the risk? Placing the front wheel improperly and going OTB?

1. My weight was closer to the front and my arms were a bit more tucked, which was a less strong position. By the time I reacted to poorly anticipated impacts - even fairly minor ones - I was dangerous far forward and in a weak position.

2. The lack of trail created light and twitchy steering.

3. The relationship between steering input and balance correction is dominated by how close your centre of mass is to the front contact point. For example, you ride a tandem at slow speed from the pilot position, but it would be nearly impossible from the stoker position, even if you could set up a steering linkage. Similarly, climbing with a slack seat tube angle places your weight over the rear contact patch; if you need to make a balance correction, the front wheel needs to move considerably to restore your balance on the line between contact points. The combination of my balance being more than half a foot closer to front contact point and the twitchy steering felt unstable and unpleasant.

The bike tracked beautifully on climbs (as long as I sat on the very tip of the saddle ... yikes) and balance corrections required minimal action at the bar. A long rear centre and short front centre is brilliant for that. Point it downhill and the situation is reversed. Terrifying. Although my friend was used to his bike, it took only a few minutes on a modern bike to realize he needed to replace that dinosaur.

I'm not saying a long rear centre is bad - I actually prefer a slightly longer RC. I'm saying a steep seat tube angle, long reach, and moderate to slack head angle form the core of modern geometry; the rear centre and weight distribution on flat ground are secondary considerations.

|

3/11/2019 6:30 PM
Edited Date/Time: 3/11/2019 6:34 PM

Sounds like you convinced yourself that you didn't have to adapt to the bike's geo that much, and felt the negative traits of heavy weight bias up front, which I expected.

Do you usually try to shift hips more forward on climbs or only on your friend's bike? I don't need do such at all, though if the saddle isn't tilted down I might grip harder to not slip backwards.

I'm went through the same case as your friend. The Dengfu uses dinosaur geo. That's why I crossed it off my list. I want something more forward, but I don't want it by simply shortening the CS. I wanted forward geo through massively lengthening the front...

That's a problem for tall guys though, since the front gets longer for each size and makes things too forward for them. The ones that want a longer wheelbase for speed don't want the front shortened, they want the rear lengthened to restore the balance.

I don't know how you guys don't see how we're talking about the same thing. I just tried to explain it through positioning in my last post. You guys are underestimating the effect of geo, and I'm surprised that R-M-R agreed, despite his experience on the dinosaur.

Do I need to make an animation or can I use an analogy like how do experienced surfers know where to stand on their board to optimize stability? What if they want to execute a deep pivot turn?



|