Tandem Cycling - Burley Bongo BB Question
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07-16-07, 12:38 PM
I am a new member looking to get help on an issue with my 15 year old Burley Bongo. I am the original owner, but my wife and I haven't used the bike all that much over the years. I am in the process of freshening it up with the intention of really finding out if tandemming is for us. If so we'll replace this bike with something newer, but first I need to repair a few items. The rear BB is a press in bearing arrangement using I believe 6903 sealed bearings. These need to be removed due to wear and for painting. Is there a secret to getting them out after removing the circlips? I have a really big hammer, but I think that is last on the list of techniques. Any help would be appreciated.
Pressed into the BB shell, or cartridge type with BB cups?
If hollow axle, then a length of all thread through the axle
with washers and nut on one end and a suitably sized cylinder that
restrains the outer housing with a larger washer on the end
of it will allow you to extrude the axle and more than likely
one of the bearings out of the housing. Usually a shift of
a bit more than one bearing width will suffice. The other
bearing can be pushed out with tapping or a dowel.
Reassemble in reverse. What you need are cylinders/pipes
holes in wood, of a size just larger than the bearing outer
diameter, but smaller than the housing outer diameter
to dissassemble and another pipe/cylinder/hole in wood a
bit larger than the axle diameter but smaller than the inner
race diameter of the bearing to press the bearing on the axle.
BFH will work tapping on a piece of wood on the end of the
axle, but you might damage the bearings, which presumably
you plan to replace. You still need the cylinder for the bearing
housing to keep it from moving as you tap the axle through.
Shouldn't need an awful lot of force unless obviously rusted
Finally mark which end of the axle is which so just in case the
R extension is not quite the same as the L side extension you
don't inadvertently put the thing back reversed. Might do to
measure and record how far out from the bearing the ends of the
(axle) taper protrude in case there is no bearing stop on the axle.
My White Brothers axle is like that on my recumbent (no bearing stop).
07-16-07, 03:14 PM
Thanks for the info, I was able to get them out after allowing the bearings to soak in WD-40, then applying some heat. A few blows with a dead blow and a suitably sized drift did the job. I was concerned that they might have been secured in a fashion I couldn't see. The ace mechanic at the LBS was off today and I really wanted to get it to the painter.
07-16-07, 04:43 PM
To facilitate re-inserting that BB, put it in the freezer overnite. Much easier to re-install.
07-17-07, 11:47 AM
The freezer trick is one I'd forgotten. It makes allot of sense given the tolerances.
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