Bicycle Mechanics - Crush the chain stay

Folk Lore or fact? Is it true that a rear-mount kick stand will crush a carbon chain stay under just regular use?

Carbon tubes are not designed to be clamped by anything. Do so at your own peril.

kickstand? i've heard of those ;-)

The thing with carbon fibers is that they are very stong in tension only. this high strength allows frame designers to make a frame strong where it needs to be and pare away all the rest, giving nice light frames. your carbon chainstays were designed to be strong as tubes, and resist bending and twisting, not crushing from a clamped on kickstand. Chainstays could be designed out of carbon to hold a kickstand and it would be fine, but they are not designed for it. Also, carbon tubes arent very tough, they would scratch and mar easily which would compromise the strength of the fibers and structure.
Nowadays, bike tubing is very optimized and specialized, so I would advise against kickstands in most cases, especially on light alum frames. Steel is real and stands a better chance because it is a tougher material. Maybe try some thin rubber between the clamps and the frame if you have to do it.

my .02

~Steve

Sounds bad but sometimes I take my bike over to the islands for 60milers and at times there's nothing to lean the bike against.

Hmmm that explains why my LBS recommended a stand that attaches to both the seat stay AND the chain stay. Are these any better?

i lay my bike on the ground sometimes.

Do they make strong plastic ones?

i too sometimes lay my bike down on the grass, always on the left side.

Would this also apply to the 'round-the-tube clamps on upright roof rack mounts, a la Saris? How do CF frames handle minor-to-moderate external, lateral impacts, say, a low-speed rear-ender while the bike is on a trunk rack? Or, say you're leaning it on a pole and it slips?

I'd much rather lay a bike on it's non-drivetrain side than stand it up in open space on a kickstand. Once it's on the ground, it can't fall over.

Sounds bad but sometimes I take my bike over to the islands for 60milers and at times there's nothing to lean the bike against.

Damage is caused by energy transfer. When a bike falls, the amount of damage it sustains is proportional to the potential energy being realised. One of the lowest potential energy states for a bike is to have it laying on its side on the ground.



Hmmm that explains why my LBS recommended a stand that attaches to both the seat stay AND the chain stay. Are these any better?

Not really... now you have the chance to crush both stays instead of one.

Aside from laying the bike on the ground you have other options such as using the pedal trick.

http://www.neebu.net/~khuon/albums/2003STP-2/PICT0026.jpg

It also works on random rocks and stumps too...

http://www.neebu.net/~khuon/albums/rattlesnake_lake/PICT0046.jpg
http://www.neebu.net/~khuon/albums/visual_tao_of_cycling/PICT0013.jpg

"Precarious," you say? Sure but not any moreso than a kickstand and probably less.

My vote is to either lay it down or if it has to be upright, turn it upside down.

A Kickstand on a carbon stay that isn't reinforced for that purpose? Hello Voided warranty

Well since the chainstay's are in tension, however little elastic deformation that forms ought to relieve some of the clamping stresses if carbon fiber adheres to poisson's ratio since the diameter would ever so slightly decrease. I'll venture a guess and say it's not as bad as the chainstays being in compression since that would very easily buckle if something is clamped onto it deforming it.
Either way, I won't do it to CF, besides a kickstand on a high end road bike just doesn't look right. :)

Well since the chainstay's are in tension, however little elastic deformation that forms ought to relieve some of the clamping stresses if carbon fiber adheres to poisson's ratio since the diameter would ever so slightly decrease. I'll venture a guess and say it's not as bad as the chainstays being in compression since that would very easily buckle if something is clamped onto it deforming it.
Either way, I won't do it to CF, besides a kickstand on a high end road bike just doesn't look right. :)
I look at it this way: They reinforce flat carbon handlebars to allow for bar ends as it's an expected use and therefore they make allotments for it. No frame maker would reasonably expect someone who's enough of a weight weenie as to by a carbon bike to even consider putting on a kickstand.

Well since the chainstay's are in tension, however little elastic deformation that forms ought to relieve some of the clamping stresses if carbon fiber adheres to poisson's ratio since the diameter would ever so slightly decrease. I'll venture a guess and say it's not as bad as the chainstays being in compression since that would very easily buckle if something is clamped onto it deforming it.

Part of the chainstay is in tension. Another part could be in compression. it's all relative anyhow since the structure is being loaded as if it were a cantilever beam. The top will be more in compression and the bottom will be more in tension. As far as chance of failure, I think it all depends on the fibre layup. If the chainstays were layed up using unidirectional fibres all aligned in a longitudinal fashion then the clamping forces from the kickstand could fail the top of the chainstay. With a bidirectional or multidirectional fibre layup, you may be able to redistribute the loading more evenly across the mesh. Another thing to note is that CF is a composite material thus its properties are often quoted with respect as a composite structure being loaded but point loading on the surface acts locally on the epoxy and you may invalidate integrity of the surface before ever reaching the yield of the entire material. This will eventually cause a stress riser and lead to structural failure as the stress at the cracks will be more than sufficient to exceed yield strength.

I look at it this way: They reinforce flat carbon handlebars to allow for bar ends as it's an expected use and therefore they make allotments for it. No frame maker would reasonably expect someone who's enough of a weight weenie as to by a carbon bike to even consider putting on a kickstand.

I think Easton not only reinforces the handle but also shapes the clamp to reduce stress risers.

I think Easton not only reinforces the handle but also shapes the clamp to reduce stress risers.
I believe you're right.

I don't have a kick stand on mine but I'm guessing that just kicking the stand up so you can resume riding would probably have twist and lateral stress on the clamp.

Good thread!

I believe you're right.

Easton also has some very specific recommendations for clamp designs of things like barends. In addition to reinforcing in the handlebars, Easton also does some tricks with the shaping around the clamp area for some of its other components such as their seatposts. They call it RAD (Relief Area Design) which is basically a flat section on the front and back. Notice that Easton carbon posts have both minimum and maximum insertion lines that correspond to the section of the carbon with the flat spots.

Easton also has some very specific recommendations for clamp designs of things like barends. In addition to reinforcing in the handlebars, Easton also does some tricks with the shaping around the clamp area for some of its other components such as their seatposts. They call it RAD (Relief Area Design) which is basically a flat section on the front and back. Notice that Easton carbon posts have both minimum and maximum insertion lines that correspond to the section of the carbon with the flat spots.
I'm won't be using a carbon post this lifetime. Reinforced or not they just aren't designed for my kind of force

The only thing I want carbon on my dream bike is me. Hehe.

I don't think the prong on the kickstand and the spring has enough power to damage the stay by flicking it up. I'd be more worried about the force used to tighten the clamp around the stay and the forces generated as the stand's holding up the bike and wind or some careless person pivots it over.

If you want to rest the bike against the rails of a ferry, the you can try using an elastic strap, eg an old inner tube or bunji chord, to stop the bike falling over.
If you are really intent on fitting a kick-stand, then the only "sensible" way with carbon is to glue it on.

If you want to rest the bike against the rails of a ferry, the you can try using an elastic strap, eg an old inner tube or bunji chord, to stop the bike falling over.
If you are really intent on fitting a kick-stand, then the only "sensible" way with carbon is to glue it on.

The strap just might work. To give an example of this frustrating double-std:

My LBS said what? a kick stand? You don't need that! Later, when I walked up to cashier, there was no place to lean that bike! AT ALL. While trying to put it in my car, there was no place to safely lay it down. The side of the building was 30' away full of merchandise and customers.

Pissed me off...I needed that stand less than 1 minute after walking away from that smug mechanic. Guess I could have leaned against that Firebird!

While trying to put it in my car, there was no place to safely lay it down.

Lean it (usually the saddle) against your car. Done properly you won't scratch the paint (and I'm anal about scratches on my car).

If you're loading the bike into the car then the first thing you should do is remove the front wheel and lean it against the bumper... now you can stand the bike on the fork tips while you fold down the car seats, etc.

Lean it against the smug mechanic's car.

Lean it (usually the saddle) against your car. Done properly you won't scratch the paint (and I'm anal about scratches on my car).

If you're loading the bike into the car then the first thing you should do is remove the front wheel and lean it against the bumper... now you can stand the bike on the fork tips while you fold down the car seats, etc.
If there is little space, il park my roadbike upside down!!

If there is little space, il park my roadbike upside down!!

I do this often... especially for changing a flat. Other things you can do is to hang the bike from the handlebar drops. You can do this against a lateral crosspole or logitudinally against one side. Also you can hang the bikes from the saddle from a crosspole if you can find one. Here's an example of that at a velodrome.

http://www.neebu.net/~khuon/albums/bothell_skibike-afterwork_ride/PICT0004.jpg

i could see maybe if you ride a road bike or something carbon or whatever.....but if its just a normal bike....a say just DROP it on the ground ( or place ) ....bikes are meant to be ridden...so ride them hard