25.4 bars, 26 inch stem, soda can?
I have a four bolt 26mm stem and 25.4mm bars. I put the bars on without a shim and it didn't appear that there was any sizing issue. But .6mms is pretty significant, so I want to get this right. I cut some shims out of an aluminum soda can. Two, one for each face of the stem that comes in contact with the bar. I don't have a micrometer, so I can't measure the actual thickness of the metal (and I'm far too cheap to pay $10+shipping for a shim). Anyone know what the thickness is? I googled aluminum can wall thickness and got a range of average thickness from .009 inches to .013 inches. If my can falls within that range I should be pretty close to the .6 mms I need. When do I just call it good enough?
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Personally, I sprung for the Nitto shims. But I thought I read somewhere on BF that the Jumex juice cans are the perfect thickness.
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usually the energy drink cans have thicker walls, but I don't know how thick.
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If it's a pop-top stem (as opposed to a quill) I don't even worry about it.
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Originally Posted by dobber
(Post 5458716)
If it's a pop-top stem (as opposed to a quill) I don't even worry about it.
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read your post, grabbed a soda can,cut it, and measured it at .13 mm or .005 inches. Tomarrow I will experiment with some stuff, as I have the same issue. I used 100 grit sand paper as my shim, it sorta works ?
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I got a couple of google hits that agree with .005. This would mean I'm half way there, no? I suppose I should double up the shims then.
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A strip of Diet Coke can has been keeping my handlebars secure for about 3 years. And if it was good for Greg Lemond in the Tour De France time trial... I figure it's good enough for all us mere mortals.
DanO |
This is great!
Yea, I have the same issue. Want to try the soma noha's arc bar with a 26mm quill stem. Part of the charm of reviving a vintage bike is to make the most of what you've got and not spend spend spend. I love the idea of a coke can rather than a rivendell shim. gonna try it! :D
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ive run 25.4 bars in 26 stems and vice versa (!) with no negative effects except scraped up bars. it just depends on your stem and bars since neither are generally 100% perfect. if it feels snug and you can't move it with all your strength, you shouldn't worry about it.
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Try using some 2 liter soda bottle material. I put a Ritchey 26.0 stem on my mtn bike by doing this. It's the right thickness but was a bit of a pain to install.
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Originally Posted by illwafer
(Post 10248863)
ive run 25.4 bars in 26 stems and vice versa (!) with no negative effects except scraped up bars. it just depends on your stem and bars since neither are generally 100% perfect. if it feels snug and you can't move it with all your strength, you shouldn't worry about it.
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Originally Posted by operator
(Post 10249215)
This is the singlehandedly most dangerous piece of advice i've read all month.
At very least, use the correct shim: http://www.velo-orange.com/nittoshim.html The right parts are cheap. New teeth are not. |
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I've had great success with soda cans, but I've also had failures. There is nothing quite so frightening as jumping a pothole, only to have the handlebars rotate out from under you when you land. I very nearly almost lost some teeth, or at least some skin.
What I learned? Soda cans work ok, but for a good strong shim, you need beah http://bikeforums.net/attachment.php...hmentid=132418 the wider can allows you to make a longer one piece shim, that in my experience has been more durable. |
Originally Posted by operator
(Post 10249215)
This is the singlehandedly most dangerous piece of advice i've read all month.
Originally Posted by Jeff Wills
(Post 10249248)
Ditto. Even if it "feels snug" and you can't move it, the handlebar can still rotate under enough impact force. If you're on a drop bar or mountain handlebar with extensions, this can dump you on your face.
At very least, use the correct shim: http://www.velo-orange.com/nittoshim.html The right parts are cheap. New teeth are not.
Originally Posted by fuzz2050
(Post 10249380)
I've had great success with soda cans, but I've also had failures. There is nothing quite so frightening as jumping a pothole, only to have the handlebars rotate out from under you when you land. I very nearly almost lost some teeth, or at least some skin.
What I learned? Soda cans work ok, but for a good strong shim, you need beah http://bikeforums.net/attachment.php...hmentid=132418 the wider can allows you to make a longer one piece shim, that in my experience has been more durable. |
Originally Posted by illwafer
(Post 10251576)
Thanks. Care to share your evidence or experience why, instead of this canned response?
I read these scare tactics all day long on here. Losing your teeth would have more to do with riding style than a .6mm piece of metal. Do you think a real shim would have prevented this? It is just a tiny piece of metal. Enough force can cause properly fitted bars to move or even break. I don't even need to defend my assertion. Any mechanic who's wrenched on more than 1 bike will know that clamp diameter is non negotiable for quill stems. Especially for something that is such a huge mismatch. And P.S it wasn't a canned response, I wrote it just for your dangerously incorrect advice. |
Originally Posted by illwafer
(Post 10251576)
Do you think a real shim would have prevented this? It is just a tiny piece of metal. Enough force can cause properly fitted bars to move or even break.
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even in a threadless stem, I can make my bars rotate just by putting all my 130lbs of weight on it when the bars are 25.4mm and the clamp is 26.0mm.
and yes, the bolts were tightened down as hard as can be without stripping anything. |
Originally Posted by illwafer
(Post 10251576)
Thanks. Care to share your evidence or experience why, instead of this canned response?
Do you think a real shim would have prevented this? It is just a tiny piece of metal. Enough force can cause properly fitted bars to move or even break. I've removed (and thrown away) "soda can" shims that have distorted over time, allowing the bars to move in the stem clamp. That experience made me very cautious about the handlebar/stem interface. |
Whether or not the bars rotate is NOT a valid test of your stem-bar combination. Mixing parts with different clamp diameters means that the clamping force is being put into a small area where the two different diameters intersect instead of spreading evenly over the whole clamp area. On a nice thick piece of metal, that's probably fine. On a very thin aluminum bar, you are likely to distort the shape of the bar at the clamp area and create stress risers. Rotation will be the least of your worries. Watch out for the bar cracking in half at the clamp. Steel is one thing...don't screw around with light weight parts.
@jds108 - do you mean a plastic soda bottle? That is too soft a material for a shim. Soda/beer can aluminum is very high quality material. It should be fine for shims as long as the thickness is close. But I agree with the posters recommending using one large piece instead of several small ones. |
hardware store has .010" shim stock. .6 mm = .024", so .010" shim would be very close.
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Originally Posted by DLM
(Post 10252220)
Whether or not the bars rotate is NOT a valid test of your stem-bar combination. Mixing parts with different clamp diameters means that the clamping force is being put into a small area where the two different diameters intersect instead of spreading evenly over the whole clamp area. On a nice thick piece of metal, that's probably fine. On a very thin aluminum bar, you are likely to distort the shape of the bar at the clamp area and create stress risers. Rotation will be the least of your worries. Watch out for the bar cracking in half at the clamp. Steel is one thing...don't screw around with light weight parts.
@jds108 - do you mean a plastic soda bottle? That is too soft a material for a shim. Soda/beer can aluminum is very high quality material. It should be fine for shims as long as the thickness is close. But I agree with the posters recommending using one large piece instead of several small ones. I'm all ears if you really think it's a problem. |
Originally Posted by jds108
(Post 10254254)
Regarding the plastic bottle shim - why do you think it's too soft? I've been using it on my mtb for about a year now with no issues. The material is just the right thickness for this application (25.4 into a 26.0). I took a look at it after my first ride and didn't see any permanent marks in the plastic (i.e. plastic deformation).
There's also a big difference between riding with a sturdy cromo bar/stem and some of the really lightwieght stuff. Ironically, the more expensive the bike, usually the more fragile these parts are. Not knowing what the OP has, I just wouldn't recommend something that doesn't seem safe to me. Again, may never give you a problem. But I just wouldn't ride with that much depending on a piece of soda bottle. |
Originally Posted by jds108
(Post 10254254)
Regarding the plastic bottle shim - why do you think it's too soft? I've been using it on my mtb for about a year now with no issues. The material is just the right thickness for this application (25.4 into a 26.0). I took a look at it after my first ride and didn't see any permanent marks in the plastic (i.e. plastic deformation).
I'm all ears if you really think it's a problem. might be different if you added some long bar-ends to the flat bar. |
Originally Posted by illwafer
(Post 10248863)
ive run 25.4 bars in 26 stems and vice versa (!) with no negative effects except scraped up bars. it just depends on your stem and bars since neither are generally 100% perfect. if it feels snug and you can't move it with all your strength, you shouldn't worry about it.
And it WAS just fine for several months, until I hit a pothole when riding on the hoods and the bars rotated. When I got off the bike there was a crack 2/3 of the way through the face of the stem. If I had missed that pothole, and later hit something harder and it broke, who knows what could have happened. Be careful, especially with stems. |
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