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I wonder where your center of gravity lies on the wheelbase with that set up compared to a bike with a more conservative geo. The high stack and shorter reach would move it backwards and higher since you're going to be very upright while riding it.
my feeling is that where we are loading the bike makes all the difference. CoG might be lower with lower stack and longer reach, but if you have to weight the bars you are loading a part of the bike that is very high relative to the pedals. With longer RC numbers we can push into the pedals, which is loading a much lower part of the bike. I guess it is about leverage, but I think tht pushing into the pedals is the same as loading more weight into the BB area, where pushing into the bars is the same as loading more weight onto the headset. Which one sounds better to you?
Too many of the physics interpretations I have seen applied to this problem assume static loads and a static CoG. I just can't believe this is true when dynamically speaking the longer RC allows us to really load up the pedals, with this input dramatically changing the forces distributed through the bike. pushing down on the bars seems like the least ideal way to manufacture front wheel grip when we are looking at leverage and balance and dynamic loading.
That bike must be fun navigating in tight turns and switchbacks.
Tight switchbacks, on the way down, can be done with ease with nose turns. On the way up you can always wheelie turn like on a motorbike
Tell me you ride the euro Alps without telling me...
Is biking supposed to be fun on tight switchbacks going down? I prefer geo for good trails.
Yeah, that’s about the response I expected. Everyone sees the chainstay length and has a knee jerk “omg long bike bad corners” response, rather than looking at the wheelbase and asking about rider height. The wheelbase of a bike determines its turning radius, but the wheelbase of a bike also has to be proportional to the rider.
I’m 6’4”. The wheelbase of my bike is almost exactly the same as an XXL Santa Cruz Hightower, which is what I’d be riding if I didn’t have this bike. But no one says “omg XXL bad corners why not ride a medium” because they understand human size differences much better than bike geometry. I’ve been riding mountain bikes since the early 90s and a ~1300mm wheelbase bike is so much more fun to ride than shorter ones on actual trails.
Yeah, it’s tough on some switchbacks. It’s also tough buying shorts and long-sleeved shirts and being comfortable in airplane seats. But I can see the band at concerts and the top of everyone’s refrigerators so it works out.
The cool thing about this bike is that the long chainstays provide the length I need but the short reach makes it incredibly nimble for its length.
Glad to see this thread here! Ive become a big believer in longer chainstays since I got my V3.2 Banshee Prime. Two things I have noticed when geometry becomes more centered is, the sensation you get when tire are approaching the limits of grip is more linear, and two, I find that I can rotate around the front tire much better than before. Basically my ability to drift through corners is much more controllable, and I can sense it coming earlier. Jessie Melamed recently said he always rides medium frames because they are often the most balanced, and he sets his bikes up to prioritize flat corners, which I think is smart. I just ordered the longer drop outs for my Banshee, so ill be rocking the 460 chainstay soon. Very excited to try it out.
I am also very intrigued by Isak Leivsson's bikes. They all have super long chainstays and really short reaches, but the wheelbases are inline with a lot of modern bikes. Somewhat similar philosophy to the Mistress bikes, but quite a bit slacker. https://www.skogsykkel.com/enduro
😂Touché, touché my friend
Does anyone have experience with MX vs 29 on ling rear centers?
Are you stood literally upright on this? I'd love to see some pics of body position on your contraption lol
Nah, bars are about even with the saddle. Instead of maxing out spacers and running a 50mm riser bar, I've got a single 5mm spacer and 20mm bars.
How does the short reach affect your arm position? A lot of riding is done in an "attack position" where you are in a good strong place to absorb impacts with your arms. Does having your hands closer to your feet push you back over the rear wheel when in that attack position?
Thought this was an interesting screen grab of Reece Wilson’s body position riding a short stem and longer chainstays (no idea what they actually are since they have been testing proto stuff, but stock geo says static 445-460mm). Looks like he’s riding a moto.
Looking like Chase Sexton with that body position. I'm assuming he is quite comfortable given how much time he spends riding motocross.
How long is long? I've owned a GG Gnarvana 29er (450 CS) and a few MX bikes that have CS from 440-447. I feel like in MX setup, the bike rides like the CS is about 5mm shorter while cornering. The 447 bike was an overforked Levo S3, so it was really close to having CS = reach, but the reach was about 8mm or so shorter than my SC bikes which have 440ish CS. So even though CS/reach were balanced on the Levo, I felt like I had less front end grip because the reach was kinda short and pushing me rearward. I guess my point there would be that I wouldn't want a bike with shorter reach just to match the CS length. The Gnarvana felt like I was driving a fire ladder truck, rear wheel felt WAY out behind me. Mega stable though. I briefly rode it as a mullet but not extensively because the BB got mega low, and it got crazy slack... can't remember how it cornered. I'm 5'8" and ride mediums FWIW.
It’s helpful to think in terms of rear center and front center. When you overforked your Levo you decreased reach, but you increased front center (and stack.) When I overforked my SteVo I lost a ton of front wheel grip because of the increased front center and the increased slack leading to less weight naturally placed on the bars.
When we talk about longer rear centers, or ratios, we aren’t talking about reach, though we might be talking about decreasing front centers (see: slightly steeper HTA over the last couple years.) we can still make bikes that ride the same from the cockpit, but provide different ride dynamics from those points.
Matt Beers on riding a bike with a longer rear center:
“Putting the bike into steep, switchbacks takes some commitment to trust the front wheel won’t tuck underneath you. It’s not the most inviting if you’re not on your A-game and certainly not how I expected a 170 mm-travel enduro bike to respond in those scenarios. With that said, I do ride further forward on the bike than most. Compared to a ganglier rider, like Amaury Pierron, he tends to ride with his hips lower and further back over the saddle. I found myself mimicking his riding style on this bike. Only then did it start to click. If you expect a super-slack head angle to erase your mistakes, this isn’t the bike for you.”
If you don’t understand why every brand hasn’t adopted the geo that some of us are espousing, here is your answer. That instant shift in riding style is not possible for every rider. If Beers had trouble, what hope do the bumblers have? Why do we expect product managers to be able to make this shift?
Yeah, I looked at that. GG Megatrail MX (trail) 1.85 FC:RC. GG Gnarvana 1.74. My Levo ended up with 1.77. My Nomad 6 (hi) is 1.82, Heckler SL (lo) 1.79, & Vala (lo) 1.82. Of all of those, the best all around handling for me (front end grip, stability, tracking in corners, & confidence in steeps) are the 3 Santa Cruz bikes. I mentioned reach because I feel like there's a sweet spot on it particular to each rider, especially on MX setups, that affects front tire grip - the FC:RC ratio is meaningless if reach is too short. Too short (especially paired with short rear end) and you end up with more weight on rear tire and not enough front grip. I had more front tire washouts on the Levo than any of the other bikes, and the Megatrail was the squirreliest in corners (wanted to square off / inside line everything).
I grew up riding cross country and most of that time was on 26" wheels, and I used to ride trials in college. I owned an Ozonys Curve 24" (gorgeous piece of art) and got decent at the basic trials maneuvers (once did a 10ft drop. That was surreal). The bike was a 17lb no-seat feather. Given the posture of the bike how many hours I spend on it, and how small the thing was, it felt like an extension of my body.
Little did I know that in the future when I pursued trail and enduro riding, that all of the trials riding would carry over into how I ride MTBs: far back or far forward. Is it improper posture? For a coach teaching a beginner, probably.
But... I'm 6' 2" with a +4" ape index and 34" inseam. Last year when I purchased a Spartan HP, I had to test a bike with almost identical geo (Spesh Enduro S2 and S3) and discovered there was NO WAY I could ever go over a 470 reach. I went with a size M Spartan, and I feel so at-home and comfortable on it. Even riding my shorter brother's fat bike and Giant Trance I feel very welcome on.
Taking a note out of Richie Rude's book, sizing down from the manufacturer's recommendations is absolutely the right choice for me. Just sitting on L and XL bikes inside of bike shops makes me feel like a stunted child: why are they so big? My 2017 Felt Decree XL has always felt a little big, and I've put a 35mm stem on it.
I've done some sketchy stuff on bikes in my life, but going full speed down powerline easements, mountain roads, twisty single track, steep techy chunk, never have I felt like my bikes are too small. That may be because of all of the trials riding I've done, but given my proportions, I am just not comfortable riding bikes with reaches above 470. If I was to guess my ideal reach, I'd park it around 457.
I don’t understand that.
our weight rests mainly on our feet, with a small percentage on our hands. You can not change that long term.
Bikes have pedals, on a rotating spindle. So, regardless of foot position, your weight can only ever go through the middle of the pedal. If you don’t compensate with the position of your hips/torso, you would end up with more weight on your hands, which would be very uncomfortable. So, you (subconsciously) adjust. Therefor foot position determines load on your calf muscles, and slightly, your range of motion fore and aft due to your neutral hip/torso being slightly for or aft, but I bet the latter is so small as to be unnoticeable.
Totally agree that long travel fork + 29” front wheel = high stack for a small size. But they should at least be as low as possible, and at a minimum those sizes should come with a flat bar.
And I personally suspect a lot of very small riders would do better on full 27.5” bikes. Sure, a 29er front wheel might roll a bit better over stuff, but having full range of motion and the ability to load the front wheel is worth even more I bet.
It's honestly refreshing to see a review talk about the potential short comings of longer rear ends, even if he didn't call it out specifically. That Comencal he was on had a 1.82 FC RC ratio, not really that out of the ordinary, but he noticed the ammount of weight it was putting on the front wheel for him and his riding style. That's why I'm generally against the idea of "proportional stays", because it's only accounting for a single factor, static weight distribution. I really hope the online crowds stop pushing for them like they are the only way forwards.
Not necessarily.
Think of doing a deadlift:
At the bottom your hands/shoulders are very low. At the top they are very high.
Yet, all the time your CoG stays balanced over your feet.
Basically, as your shoulder mass moves back (and up) your hip mass moves forward (and up), so the net effect is you are able to stay balanced.
What bike/review was that? Google can’t give me an answer.
Beer is also not particularly tall. Most of this discussion on this thread is about more balanced bikes for taller riders, not longer chainstays in a vacuum. Moreover, look at a bunch of his reviews and he like plenty of bikes with that ratio or even more balanced. For example: https://www.pinkbike.com/news/staff-rides-matt-beers-commencal-supreme-2927.html
I think you're way overstating your case
pretty sure the h/a contributed more to beer's observations than the (445mm) rc. to wit:
"If you expect a super-slack head angle to erase your mistakes, this isn’t the bike for you"
New comencal ebike review
Go watch D Nortons interview from sea otter, he talks about how running flats vs clips make a difference - also talks about How your more likely to destroy rear wheels with flats as you're slamming so much weight into the rear wheel & you tend to load the bike alot more.
Clip riders can ride much more aggressively as they can ride more flat footed or even toe down in certain scenarios which in turn moves your COG more forward.
Theo and others were trying to convince matt jones at hardline he needs to get into clips so he doesnt ride off the back so much.
I can easily switch between flats and clips. The changes in riding feel is very different you can make the bike feel light over the rough with clips.
You said it yourself "our weight rests mainly on our feet " which means when you change that you effect the bike alot.
It's not something You change overnight if you ride flats and change to clips, it takes awhile to adjust to the actual ride feel and the way you can ride the bike.
Long chainstays put more weight on the front wheel. On the steeps it makes it necessary to shift your weight a tad further back. Having long chainstays also allows you to run more stack without losing front end grip. I've gone to a taller handlebar since going to 475mm chainstays.
Post a reply to: Modern Geo Talk: Chainstays, Stack, Reach, and Bitching About It