Bicycle Mechanics - BB cup too thick?
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Purchased a GUB external type BB on ebay,supposedly OK with 68 or 73mm shell--came with spacers for the bigger sz
My problem is that the cups are not bevelled and therefore stick out too much,even though the total ht of the BB is correct
The net effect is that the spindle (7800) is now not fully engaging the ND side crank arm --about 3mm of spline left over
I shall try for a refund,but otherwise would this matter?
03-27-11, 09:15 PM
3mm of engagement is not a lot, but on the other hand I've seen the damage caused by not fully engaged splines, and it's not pretty. In this case it was an isis right crank that worked loose, causing strippage of about half the depth of the splines. There was enough spline left that I could reattach the crank after aligning what was left of the splines to the spindle, so the guy could ride home very carefully.
More important, though, is the 3mm less engagement by the left crank end bolt, possible trouble caused by the pinch bolts clamping down on it in its partially engaged state, and how that might lead to a loose crank arm and stripped splines.
The whole thing smells fishy to me. I'd try for a refund and get a BB sized correctly for Shimano.
03-28-11, 11:25 PM
Is the cup screwing in enough to touching the frame's edge? Or is that the problem when you say sticking out? If that's the problem you might need the frame threaded in further so the cup can screw in far enough to touch the frame?
Maybe you are using a spacer that is pushing the cup too far out and causing the crank's spindle to not have enough spline to tighten to? Im just taking a stab in the dark here. Pictures maybe, or a picture online that represents the problem?
Tx for replys guys---cups are all the way in,no spacer used, snug to the frame---I think that the lack of bevelling is the prob as the BB shell has a matching bevel which would mate with the bevel used on a DA BB---would probably be good for about 1-1.5mm each side
The GUB is dead flat and does not engage the bevelled shell
03-29-11, 09:14 AM
Looking at the BB design, yes that appears to be thicker than the equivalent Shimano.
If it won't fit, don't force it, as you will damage someting; but would not ride if could not get it to fit.
Guessing you got this from HK, would be supprised if after postage it is worth returning.
FYI I enclose pics--I think this is a design flaw
03-30-11, 02:27 AM
Wouldn't call it a design flaw, just not desiged for that frame
Haven`t seen this unit myself so looked it up and think you should have contacted the seller for clarification before buying.
The description for compatability reads "FITS MOST ....."
And also specifies "Aluminum frame" (although 68mm should be 68mm)
The other item I don`t follow is the spec that "2 spacers 3mm thick" are included. Spacers are normally 2.5mm, 1.8mm and 0.7mm for Shimano and you`d normally only use the 2 x 2.5mm`s.
Personally I think dealing with HK is a pain. There seem to be so many issues with translation and transportation that half the time you don`t know what you`re really buying and its very expensive to return if you end up with the wrong item.
Probably,but I thought 68mm external BB --should be fine
I even stripped another bike ---same problem,this is a design flaw for sure.
The unit and bearings seems quite good though,--2mm narrower and it would be perfect.
I carefully filed 1.5mm off each cup and all is well now,but quite a PIA
03-31-11, 03:31 PM
shimano mtb and road cups are not the same. your cups are prob the mtn spec
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