Bicycle Mechanics - A simple question about handlebars
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10-23-06, 07:08 PM
So, the question is probably an easy one, but better safe...
I recently purchased a new set of handlebars, size 25.4 to go into my 26.0 sized stem. I also purchased the necessary shims for the process. Yet, while piecing it all together, I found that the handlebars fit perfectly without the shims. Is this cause for worry or should I just shrug my shoulders and keep riding?
Well, I'd have to say there may be a difference between the experienced mechanic's version of "fits perfectly", and the average person's. Is there any play at all when you have the stem on, not tightened, without the shims? Can you get the shims in at all without forcing? Generally speaking, yes to both questions means you need the shims.
If you are using one of the newer type stems with removeable front plate, it's easy to see why it looks like the bars fit without the shims, but they won't be clamped evenly around.
10-24-06, 07:55 PM
If you're using a 2 bolt stem, I noticed there's always a gap between the two pieces, which in some cases could be enough to allow a smaller bar.
It is reasonable to expect that you could tighten the play out of the .6 mm difference without the need for shims.
10-25-06, 09:18 PM
It's like buying jeans.......one manufacturer's 25.4 may not quite be another's.
10-25-06, 11:43 PM
Relevant data: do you have a stem with 2-bolt clamp and removable faceplate? These can be more forgiving, but shims are still good to ensure that the curvature of the faceplate and stem interface cleanly match the bar.
I don't think the comparison to buying jeans is apt at all - these are high-tolerance measurements, and nearly all 25.4's I've seen line up with nearly all 25.4 bars, and don't line up with 26.0 bars. These surprisingly small differences matter - my Cinelli XA stem (with a 26.4mm clamp) wouldn't clamp down on a 26.0mm bar.
I'd use the shims anyway, unless it's possible that the stem was mislabeled. I bought a "Zoom" stem from Nashbar that was marketed as a "road" stem with 26.0mm clamp, but it's clearly a 25.4mm clamp, and I'm using it with 25.4mm bars. It'll work with 26.0 b/c the removable 2-bolt faceplate, but the curvature of the faceplate and the stem clamp end line up cleanly with a 25.4mm bar and not with a 26.0mm bar.
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