Sealed Bottom Brackets
- Thread starter wwarnke
- Start date
wwarnke said:
First off, give us some information on the bike; age, model, etc. The width (usually 68 or 70mm) is the width of the bottom bracket shell. "Most" 68s are english threading where the 70s often are Italian threading, not interchangeable. Then you have to fingure out the spindle length. A 68mm x 109.5mm english threading would be an example of all 3 measurements. This example pertains to road bike.
This gives you more detail: http://www.bikepro.com/products/bottom_brackets/bbover.html
wwarnke said:
See this link to Sheldon Brown's site. It probably has what you need to know and also has a diagram that shows where measurements are taken.
http://sheldonbrown.com/bbsize.html
wwarnke said:
having spent most of the summer stripping and repairing these things I do understand your point but sealed bb´s have to be replaced and cannot be worked on or adjusted - with yours you can at least "play " with the width rather than having to buy new units to adjust the chain line etc .
it sounds like it will be easier but in the long run I´d prefer to keep the older system because it can be cleaned and adjusted so easily . If your planning on fitting new cranks then of course the bb´s got to go as most aftermarket stuff seems to be isis or octalink or what ever these days .
wwarnke said:
are the balls loose or in a cage ? does the shaft need to be changed ? when was it last stripped and rebuilt ?
normally these things stay good for quite a while if in good nick but if there´s a bit of wear ........
I was taught that the loose balls tend to be better in hubs but that caged was ok in a bb if the shaft was in good nick .
do you have a work stand ? it does make these jobs so much easier and faster than doing everything at ground leval by feel .
The ball are in cages. I have pulled everything apart and cleaned thoroughly. I greased the bearings and put everything back together. I noticed that adjusting everything can be quite time consuming. I would get it right, then test ride to the end of the driveway and back, and there would be slop. I did that several times till it was staying adjusted. Then I went on a 4 hour ride that was pretty rough to test out my recently rebuilt and modified fork, and noticed that it was hard to back pedal. If it is hard to back pedal, then it is hard to pedal forward and wasting my precious energy while on the trails. I adjusted everything yet again and did not have any trouble last time out.
I find that my bike requires me to check everything pretty much everytime out to make sure that the bearings are adjusted and all the suspension parts are still tight. I would assume that this is pretty normal since i tend to punish my bike solid for 4 hours at a time.
One more question, is there a secret to adjusting spokes? Both of my wheels have a slight wobble that is only really noticable if I watch the brakes while riding, as I can see the brake parts rocking back and forth as the wheel rotates.
I find that my bike requires me to check everything pretty much everytime out to make sure that the bearings are adjusted and all the suspension parts are still tight. I would assume that this is pretty normal since i tend to punish my bike solid for 4 hours at a time.
One more question, is there a secret to adjusting spokes? Both of my wheels have a slight wobble that is only really noticable if I watch the brakes while riding, as I can see the brake parts rocking back and forth as the wheel rotates.
wwarnke said:
So start at the begining ...
Take off the cranks and remove the chianring side ( ie non-adjustable ) retaining piece ( sorry don´t know corect name in english ) and extract the axle and remove the bearings . Now examine the state of the axle and the bearing tracks - any wear and replace . now look at the bearings themselves , ¿ are there any signs of wear or damage to the balls or their cages ? if there is then replace .
re-fitting : first dry fit everything to make sure that you´ve got the axle in the right way , now do it for real - and remember there is no such thing as " too much grease " ; place the bearings on the axle with the cages facing out and using liberal quantities of grease to hold them in place insert the axle and then the drive side retaining piece , tighten completely ( it might be an idea to check that the adjustment is slack for this part of the operation to avoid damage to the bearings )
adjust the tension on the bearings - do this with the bike vertical as otherwise you´ll get funny results , same as wheel bearings - adjust until tou feel resistance then slacken off a bit , but be gentle . refit the cranks and spin the pedals a bit then see how it feels ( helps not to have chain fitted for this ) refit chain and ride it , then recheck adjustment .
never , ever , use a power washer as this removes all the grease - even from " sealed " bearings .
re wheel adjustment : if you don´t have a bike stand that will allow you to spin the wheels freely with the bike vertical then it may be cheaper to pay a pro to do it for you as it´s easy to lose your way and make it worse .
if you have an old bike then you could " play " with that but remember always adjust spokes in pairs tension one and slacken the other .
without a trueing stand it will always be a bit rough and ready .
