Mike Kone wrote:
>A couple of rear wheel spacing thoughts...
>
>1) Sheldon Brown comments that most 6sp axles are 137mm which will work
>for 130mm space frames. I don't believe that this is quite correct.
>Campagnolo original 6sp hubsets were often supplied with 134mm axles.
"Most" hubs are not Campagnolo. 137 is the standard Wheels, Inc. size sold for 126 mm spacing, and I believe this is the length of common Shimano axles.
Cheaper/older hubs intended for bikes with thin stamped dropouts
would have less axle protrusion so the QR wouldn't bottom out.
>134mm axles will not work for 130mm space unless one believes that 2mm on
>either side of the locknuts is OK - I don't know anybody who is comfortable
>with this risk.
[raises hand] I'm not aware of any "risk" involved in this. Indeed, on one of my fixed-gears I've cut the axle of flush with the dropoouts, to allow more room for chain tension adjustment in the vertical dropouts.
Axles are held in place by the cone locknuts' grip on the surface of
the dropout, not necessarily by the protruding axle bumping up
against the edge of the dropout. If this were not the case,
horizontal dropouts wouldn't work, since the chain pull makes a
greater stress on the axle/dropout contact than the rider's weight
does.
>Later Campy 6sp hubsets went to 136mm (not sure 137mm
>comes in, perhaps some 136's were a tad long but I haven't noticed that).
>136mm axles leave 3mm on either side of the locknut on a 130 space frame -
>still not the 4.5mm - 6mm that Campy seems to gravitate towards! The
>unshot is that for true 130mm space frames a Campy 140mm axle is really
>what the patient needs.
Wheels goes with 137, 141.
>
>Regarding frame squeezing issues, there is no question that running
>non-exact spacing results in non parallel drop outs and the risk of a drop
>out failure - the question, though, is what is the realistic tolerance? In
>reality, few builders can peg alignment to the millimeter - and the extra
>tweaks it takes to try to do so might perhaps be more damaging than the non
>parallel dropouts. Also, Campagnolo could never seem to get there hub
>tolerances down to a science either. Hub spacing of various configurations
>seems to vary by 1mm or so.
>
>My suspicion, and others will certainly disagree, is that 2-3mm of "error"
>is perhaps acceptable, although 3mm would be somewhat risky. If 2mm is
>"acceptable", then one could could for instance have a 128mm rear and run
>either 126mm or 130mm space wheels. The degree of mis-alignment at the
>locknuts by a frame mis-spaced by 2mm is pretty negligable (but it is, of
>course, still there) If I'm not mistaken, I beleive that Rivendell might
>do something similar - as have other builders over the years.
That's correct. RB-1s came in at 128, and a number of newer
cross/touring frames come with 132.5.
>One should
>always inspect axles and if a bent one is discovered, it should be replaced
>in order to minimize the drop out failure risk.
Bent/broken axles are, indeed, probably a much greater cause of dropout crackage than re-spaced frames.
Actually, when going to a _wider_ spacing, which is the more common change, the direction of the slight non-parallelism introduced into the dropouts applies a slight stress to the axle in the _opposite_ direction of the chain forces. Arguably, this slight misalignment might actually act as a prophylactic against axle bending/breaking.
Sheldon "'H' Tool" Brown Newtonville, Massachusetts +-----------------------------+ | Razors pain you; | | Rivers are damp; | | Acids stain you; | | And drugs cause cramp; | | Guns aren't lawful; | | Nooses give; | | Gas smells awful; | | You might as well live. | | --Dorothy Parker | +-----------------------------+
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