[Commencal-guy]

I'd just like a general feedback about what people like and dislike + views on Downhill Geometry. (HA V.S. Chainstay length + Wheelbase)

Is it more ideal for a frame with a slacker HA, have a shorter chainstay = shorter wheelbase? OR a slacker frame with a longer chainstay = Longer wheelbase?


What do you prefer?

 

[JCL]

It's track dependent which is why bikes like with lots of adjustability like the Summum make so much sense.

IMO.

 

[buckoW]

I like very slack, low and short chainstays with very firm suspension. I also like adjustable geometry.

 

[gemini2k]

I like very slack, low and short chainstays with very firm suspension. I also like adjustable geometry.

I think he's got the right idea. I find myself running my stuff stiffer and stiffer everyday.

 

[norbar]

The problem with slack vs chainstay length is that on flatter tracks with very flat ha and short stays your weight bias will be a bit too far back and it may cause your front wheel to wash out. Not that you need slack head angle on flatter tracks so - adjustable head angle all the way. Short CS is good, add a 64 ha + cc headset for the steeps and Im happy. An ideal geo for me would be what is on my bashee legend with maybe a bit shorter cs (0.2 inch maybe)

 

[BmxConvert]

If you throw chainstay length into the mix, you're going to be pulling bottom bracket height in there with it..

 

[Kanye West]

I think it depends on height and how the person is built - basically how easy it is for them to get behind the rear wheel or the CG of the bike on steep stuff. Guys with shorter legs seem to always like the super short CS bikes so they can unweight the front end easier on steeps, and taller guys seem to enjoy the longer bikes and the greater stability that results.

Considering that, there is no "ideal" without taking the riders dimensions into account.

 

[weedkilla]

Personally I can find quite a range of geometries work well for me, as long as the chainstay is longer than 17"! I find that the lower and slacker a bike is, the faster it is - although I haven't tried sub 13.6bb and sub 63*. However I find chainstay length quite critical IMO, I can ride 2 bikes with the similar geo but the one with the shortest chainstays is the one that will put me on my arse when I make a mistake, the one with the longer chainstays seems to be the most forgiving of cack handed riding. The grip benefits of short cs bikes does make them fast when I get it right though. I just cant stay on them. This, however is probably just me.

 

[Pslide]

I think it's also a matter of preference and riding style...

Is racing your #1 priority? Then I would got slack, low, long for stability, speed, and forgiveness. Allows you to really push your limits with a little more security. Also great for riding steep stuff.

Is having fun your #1 priority? Then I would go slightly steeper and shorter, as I feel this makes the bike more responsive and sensitive to rider inputs, but not as forgiving. You might not be able to push the bike quite as hard, and therefore the limit is a little lower.

Just my opinion...

 

[Commencal-guy]

Well for a bike with a slack HA, the wheelbase is already longer, So I'd think a shorter chainstay would be appropriate, however Ive been fiddling around with idea, and always find longer chainstays to be the most comfortable. If you look at many bikes in the World Cup circuit many bikes nowadays are slack with short chainstays.

 

[Pip3r]

Hwang you fool just find a good lap to do and try out the 4 options your bike has. there is no right or wrong answer its whatever you feel most comfortable on. Sure, chances are a world cup rider is going to want their bike as slack and long as possible, but they are riding in an entirely different manner than you will be.

 

[Commencal-guy]

Hwang you fool just find a good lap to do and try out the 4 options your bike has. there is no right or wrong answer its whatever you feel most comfortable on. Sure, chances are a world cup rider is going to want their bike as slack and long as possible, but they are riding in an entirely different manner than you will be.

Piper go suck a duck. No way will I EVER clean your bike again!

Im not saying I will ever be a World Cup racer who wants every little detail about their Geometry. I'd just like a general feedback from us "Normal People" on what they thought about HA, Chainstay + Wheelbase ratio's.

 

[marshalolson]

6'2''

63.5-64 HA
sub 14 BB
46.5 wb
17.25-17.5 CS

dunno if this is long or short. pretty average i would say.

 

[Slater]

Been riding my Demo for 3 plus years and have riden a lot of other DH bikes. My finings is that slack long front end paired with short stays makes for a back end that doesn't track well. I suppose it has to do with the ratio of front center : rear center. It is my opinion that wheelbase is an overrated number and that there are many other geometry figures which are more important.

I think its safe to say though that most everyone these days (or soon in the future) will agree that for going fast low and slack are beneficial characteristics. Stay length is more debatable it would seem.

 

[W4S]

Personally, I like a shorter stack-reach with longer CS's and average WB. Feels like I'm more in the center of the bike (and over the pivot location) making it handle more neutral, imo. Bike is an '08 Turner DHR w/ 2010 Boxxer and CCDB

 

[descente]

i like a slack head angle, shorter chainstay and long top tube so i can "flatten" myself out over the bike. i'm 6'2" but i have fairly short legs. i like how the new demos are long and slack but with very short chainstays, it takes some getting used to but is a lot stabler than you would think...

 

[Schneidie]

Long, low and slack is the way for me. Looking for 62 or 63 degree head angle, 13.5 bb or lower, and mid length chainstays. I'm on the shorter side(5'9" FWIW)

 

[Uncle Cliffy]

Personally I can find quite a range of geometries work well for me, as long as the chainstay is longer than 17"! I find that the lower and slacker a bike is, the faster it is - although I haven't tried sub 13.6bb and sub 63*. However I find chainstay length quite critical IMO, I can ride 2 bikes with the similar geo but the one with the shortest chainstays is the one that will put me on my arse when I make a mistake, the one with the longer chainstays seems to be the most forgiving of cack handed riding. The grip benefits of short cs bikes does make them fast when I get it right though. I just cant stay on them. This, however is probably just me.

I'm gonna agree with this. I've been playing with the chainstay adjustment on my 951 and prefer it in the long setting for the way I'm riding it... Just feels more planted at speed.

 

[norbar]

Well for a bike with a slack HA, the wheelbase is already longer, So I'd think a shorter chainstay would be appropriate, however Ive been fiddling around with idea, and always find longer chainstays to be the most comfortable. If you look at many bikes in the World Cup circuit many bikes nowadays are slack with short chainstays.

Completly opposite sir. With the TT staying the same length your body and with it the weight bias stays with the same place but as the head angle slackens the front axle moves away from it shifting the weight bias to the back (just draw it if you cant get it)
As for short cs - the only short cs bike without adjustable geo i know is Demo.

 

[weedkilla]

Been riding my Demo for 3 plus years and have riden a lot of other DH bikes. My finings is that slack long front end paired with short stays makes for a back end that doesn't track well. I suppose it has to do with the ratio of front center : rear center.

I'm not sure I agree with this, but I want to check that you mean what I think you do! Not track well as in skips out from under you on a rough, fast off camber chute? Or get kicked sideays in rough straights? Or sort of the bike gets caught in a line and seems to follow it all on its own?
I always found that the demos had fantastic rear grip and when I got my body weight right they held a line beautifully in off camber.
It was easy though to have not enough weight over the front and have it push away on its own little choose your own adventure ride!
In rough, square edged sort of stuff I could never get the damping balanced low and high speed and it could just blow through its travel and kick around like a mule, I always felt that some combination of vertical wheel movement and poor damper tune just wouldn't let it absorb fast, square hits properly, never thought that was due to the length of the stays particuarly.
However I gave up on that bike and moved on well before I got it sorted.

 

[Tootrikky]

I think that you have to take into consideration the axle path of the rear wheel, and the leverage curve of the suspension when talking about how the CS length affects a longer travel bike's ride characteristics.

 

[mattmatt86]

I don't even have a clue what the geometry of DH bike is. I just throw my leg over it and pedal, never really had a problem with it. I found in years past that if I spent too much time measuring, tweaking, adjusting, analyzing etc. I spent more time off the bike than actually riding.

 

[Tootrikky]

I don't even have a clue what the geometry of DH bike is. I just throw my leg over it and pedal, never really had a problem with it. I found in years past that if I spent too much time measuring, tweaking, adjusting, analyzing etc. I spent more time off the bike than actually riding.

Cool.

 

[mattmatt86]

Cool.

Thanks, I needed a pick-me-up tonight

 

[buckoW]

I have my bike set up right now with a 62° HA, 13.5" BB, 16.7" CS, 23.6" ETT and my fork high with my bars low. I love it on flat turns and steep trails. I ride over the front a lot and don't have problems with too short CS or too slack HA.

 

[Slater]

weedkilla: it doesn't seem to have the cornering "biting" feeling in the back end and doesn't track all that well on off camber stuff either. You have to really over-exaggerate your leaning of the bike to get it to really dig in on any corner that is less than fully berm'd. It also has very little ramp in shock rate so the it'll blow through travel on the harsher hits pretty easily. And if you try and remedy this with more HSC, it ends up tracking even worse and skips around. Axle path is also very weak on the Demos which doesn't help much.

Anyways, as it relates to this topic, I have talked with some other people who have felt the same in the Demo and believe it to be the very long front end combined with a short rear end that gives you a very rearward weight bias.

 

[weedkilla]

Slater- yep that pretty much is everything I felt about my demo. I'm still unsure of which charecteristic were due to the imbalanced front/rear lengths and which were due to shock/suspension design. My marin trailbike has a similarly short chainstay and long TT but doesn't have anywhere near the amount of weird handling issues, in some situations it makes its 5" of travel feel like more than the demo's 8" and tracks beautifully. Still needs to be countersteered/excessively leaned to get the most out of it in corners though. (I know it is pointless to compare geo on a smaller travel bike to a dh bike - just trying to get my head around why I hated my demo so much and how to never buy a bike that feels like it again.)
Hopeing to try a Canfield soon which has very short chainstays but takes a completely different tack on bump absorption to specialized so that may give me a bit more insight.

 

[Slater]

I doubt much of it is shock related. It gets better with a nicer shock, but doesn't go away. I put a CCDB on it and spent tons and tons of time tuning, thinking it would be the solution to my problem. Wrong. (for the rest of you reading this, my Demo7's BB is 13.5", so that's not the problem)

Also, it will be hard to compare it to the Jedi because the stays lengthen signifcantly throughout travel, among other things.

I just find it interesting that even though the demo has short stays, that it still handles funny. The interwebs thinks that shorter stays handle better, but at least as far as I can tell, all they do is make the bike "snappier". Which incidentally does not always coincide with a bike that actually corners better.

 

[buckoW]

It depends a lot on riding styles and the rider's center of mass. Some people ride off the back of the bike and some ride off the front. The riding style needs to correspond with the geometry. Hill and Fairclough get along fine with short chain stays.

 

[Slater]

It depends a lot on riding styles and the rider's center of mass. Some people ride off the back of the bike and some ride off the front. The riding style needs to correspond with the geometry. Hill and Fairclough get along fine with short chain stays.

I agree that your riding style and body positioning are important factors. However, you can only do so much with body positioning. The vast majority of your weight is being supported by your feet, so putting more weight on the bars only does so much. You cannot transfer a very large amount of weight to the front that way. It certainly helps, but you cannot obtain the same results as if the bike had longer stays and shorter front end ala many other bikes. At least not in my experience.

Also, it doesn't matter what bike you put a pro on, they will be fast, and win. That's what they do. And if you really want to make that argument, Sam has had one of his worst seasons in years, since switching to the Demo.

Its been fun having a demo before Sam was added to the Big S's payroll, and now. It went from "cool bike, but its only good for hucking" to "man sick race sled bro, that thing must rip".

At any rate, short stays have their pros and cons.

 

[Tdubb]

I second that.

 

[buckoW]

I agree that your riding style and body positioning are important factors. However, you can only do so much with body positioning. The vast majority of your weight is being supported by your feet, so putting more weight on the bars only does so much. You cannot transfer a very large amount of weight to the front that way. It certainly helps, but you cannot obtain the same results as if the bike had longer stays and shorter front end ala many other bikes. At least not in my experience.

Also, it doesn't matter what bike you put a pro on, they will be fast, and win. That's what they do. And if you really want to make that argument, Sam has had one of his worst seasons in years, since switching to the Demo.

Its been fun having a demo before Sam was added to the Big S's payroll, and now. It went from "cool bike, but its only good for hucking" to "man sick race sled bro, that thing must rip".

At any rate, short stays have their pros and cons.

I should have added body type, suspension and steepness of the trails as well to the mix. Some people get along fine with short stays but there are a lot of other factors that make or break the deal. I am not defending the Demo by the way. I just think it is possible to set up a fast bike with short stays but there are many other factors that must correspond as well. I like adjustable CS length anyways.

 

[freeridefool]

weedkilla: it doesn't seem to have the cornering "biting" feeling in the back end and doesn't track all that well on off camber stuff either. You have to really over-exaggerate your leaning of the bike to get it to really dig in on any corner that is less than fully berm'd. It also has very little ramp in shock rate so the it'll blow through travel on the harsher hits pretty easily. And if you try and remedy this with more HSC, it ends up tracking even worse and skips around. Axle path is also very weak on the Demos which doesn't help much.

Anyways, as it relates to this topic, I have talked with some other people who have felt the same in the Demo and believe it to be the very long front end combined with a short rear end that gives you a very rearward weight bias.

Slater- yep that pretty much is everything I felt about my demo. I'm still unsure of which charecteristic were due to the imbalanced front/rear lengths and which were due to shock/suspension design. My marin trailbike has a similarly short chainstay and long TT but doesn't have anywhere near the amount of weird handling issues, in some situations it makes its 5" of travel feel like more than the demo's 8" and tracks beautifully. Still needs to be countersteered/excessively leaned to get the most out of it in corners though. (I know it is pointless to compare geo on a smaller travel bike to a dh bike - just trying to get my head around why I hated my demo so much and how to never buy a bike that feels like it again.)
Hopeing to try a Canfield soon which has very short chainstays but takes a completely different tack on bump absorption to specialized so that may give me a bit more insight.

I honestly thought it was just me that didnt like the way my demo handled in alot of situations. Coming off a large giant dh comp that was short shocked I feel like my demo is everywhere through rock and especially in off camber. I hate my dhx paired with the demo too.

Good through rocks with the right spring rate, but bottoms out like a bitch. Go up 50 pounds and it is all over the place and it doesnt bottom as bad, but bucks me on jumps.

 

[norbar]

I honestly thought it was just me that didnt like the way my demo handled in alot of situations. Coming off a large giant dh comp that was short shocked I feel like my demo is everywhere through rock and especially in off camber. I hate my dhx paired with the demo too.

Good through rocks with the right spring rate, but bottoms out like a bitch. Go up 50 pounds and it is all over the place and it doesnt bottom as bad, but bucks me on jumps.

Isnt demo slightly progressive? It is strange that it bottoms you all the time. Also - dhx has the bottom out adjuster. Doesnt it help?

 

[weedkilla]

I may be clutching at straws but I wonder if when we talk about front/rear balance there is a significant difference in where you stand on the pedals. I ride clipped, with the clips under the balls of my feet. Thats got to put me 1 1/2" - 2" further back than someone who rides flats with the pedal in the middle of their feet, then to argue about a chainstay that might vary 3/4" between super short and pretty long makes me wonder if this is a significant factor. The opposite side of this is you can change the front centre with HA adjustments by an inch or more and adjust quite easily... F-ed if I know, wish I did though!

 

[SuboptimusPrime]

^^ I don't think your foot position should matter just because all that force is transfered to the frame at the bottom bracket regardless...of course if moving your feet back is accompanied by hanging your weight back, then its a different story.

As for me, I think 64 would the the sweetspot for me, sub-14 BB, and 17.25-17.5chainstays. Rode a demo at whistler and liked it in some ways but just could not get used to how short the rear end rode when cornering. I'm a taller guy and wonder if there is truth to whoever proposed that taller people like longer bikes...it's kinda a similar idea to ski sizing.

Also agree w/ stiffer suspension settings...the "faster" I get (I'm slow) the more I find that suspension is not for comfort, but to maintain control and the attitude of the bike. Hence stiffer and stiffer set ups for me.

 

[weedkilla]

Dont want to sound like a smart arse but try thinking centre of gravity rather than point that force is transmitted through. Moving your feet back an inch would move your c of g back as well, if you stand over the pedals the same way in both positions.
I'm still not sure that this has any relevance......but I think it might. Just too many variables in my own position on the bike to work it out, let alone when talking about other people as well.

I still believe that bikes with short stays are fast - I just find them unforgiving of poor riding, and watching the youngest of the big S riders ripping it up back at a local state race reminded me of just how big the gap is from ok vet rider to top 20 WC rider pace, and I'm sure the gap would have only gotten bigger on a more technical track.

I should also add that I dont want to be seen to be bashing bikes with short chainstays - I'm just trying to work out what works for me and why. Plenty of guys, short and tall, on clips and flats, go plenty fast on all manner of different setups. I distinctly remember the dirt article from a year or two back when Commencal was testing the previous frame with the Athertons. CG and the Athertons liked a completely different chainstay lengths.

 

[Gridds]

For me, long, low and slack, with short CS and rearward axle path.

I'm 6'3". I had my bike built to these specifications:

HA: 64* (but with my current fork set up its actually 63.5*)
CS: 16.75" (Static, with rearward axle path)
BB: 14"
WB: 47"

Its fricken mint and needs no adjustments! Perfect on all tracks from steep, tight, tech, rocky, flat out fast Alpine and twisty UK backyard tracks.


Also, are people forgetting the Demo has just won 2 golds/rainbows at the Worlds?

 

[freeridefool]

Also, are people forgetting the Demo has just won 2 golds/rainbows at the Worlds?

Do you realize that nobody but sponsered riders are actually on those demos?

 

[freeridefool]

Isnt demo slightly progressive? It is strange that it bottoms you all the time. Also - dhx has the bottom out adjuster. Doesnt it help?

My bottom out is ramped way up. The more I think about it the more I may just be way off on my settings. Im having a horrible time getting the kinda "ride" I want out of it compared to how it was on my dh comp. That and paired with a dhx that is in desperate need of being rebuilt.