The MTB thread

[yorkie_chris]

Threads are OK but the bodging, useless git at the place I bought it off appeared to have fitted the cheapest bearings he could find (or maybe overtightened them). Hence after 2 months of use one of the balls had broken in half, one was dust and others were showing surface galling. If you want it doing right, do it your bloody self...

It was threaded cup in frame on outside, cone on shaft through middle. Square taper drive.
Seems like a daft idea when most of the stress is going to be radial due to bending moment of crank. Why fit that sort of bearing when it doesn't need to support axial loads?

New one does not use threads in frame, it screws in from either side and clamps in like that. Uses normal 2RS bearings like a motorcycle wheel bearing pressed into middle.

[Jayneflakes]

Sounds like it will do the job. The old cup and cone types are fading away now. Sealed units are almost the norm now, with cartridge bearings.

Good luck and happy times.

[yorkie_chris]

Yeah only worry is if it comes loose and moves around it will distort the frame. Steel vs ally... only one winner there...

Are there a lot of different sizes of bottom bracket threads etc?

[Jayneflakes]

There are a couple of common common sizes for Bottom Brackets on mountain bikes, Shell Width comes in 68mm or 73mm, but I am sure that there are others out there that have been forgotten.

Once you look at the threads, the common standard in this country is to have a right hand and left hand thread in the shells so that if the cups comes loose, they self tighten with crank motion.

Other options here are Italian thread, where both threads are right hand, so if the adjustable cup comes loose, the crank motion will cause it to unscrew. This option is usually only found on Italian road Bike exotica though, but there is always some one out there who will prove me wrong.

Originally Posted by yorkie_chris

What is your opinion of threadless bottom bracket unit?

WANK........ simples!

[yorkie_chris]

Care to elaborate...

Originally Posted by yorkie_chris

Care to elaborate...

Ok so in my personall experience threadless bb's are used either for 1)
Bmx's or 2) cheap 1piece steel bb's as seen on kids bikes and budget bmx's.

When you press such a bearing cup into a mtb frame the chances are unless the mechanic has properly faced the bb shell the cup won't sit in even as most frames come from the factory with paint around the bb shell itself ( as did my specialized enduro ).

Now as the cup itself is the cone to the bearing 99% of the time either cup will be wonky no doubt, so when the bearings and the c/arm is fittednthe bearings are put under uneaven loads causing heat build up and the decay of the greased used ( again 99% of mtb bearings sold Seperatly come with Shute grease that decay's over time naturally let alone with excess heat) and once the grease is razzed the bearings go byby!

The wonky shell will also cause uneaven wear on the bearings causing the shell to pit and again do damage to the bearings.

With a sealed bearing cartridge system or hollowtech (external) these forces and miss hap's are greatly reduced asbege bearings has it's own housing away from the shell of the bb, these bearings can be replaced/serviced for allot cheaper than those scummy cup and cone things!!


P.s. Writtten on my phone so sorry for spelling/grammer mistakes, I can't be arsed to proof read!

[yorkie_chris]

Are we on about the same thing? This BB did not require a press, and does not use a cone and cup, it uses 2 (that you can see) normal radial ball bearings with rubber seals.

Hmmm no were not.

To me that looks rather bodge... It would wor iIf a bb had no threads and was designed that way but surely if you insert something like into something that had/has threads the forces acting upon such a bb from what a 175mm crank arm would turn any frame into putty!

I've been a bike mechanic for around 4yrs now and I've never seen anything like that, I have dealt with those products before but only for cheap ass square taper stuff.

Unless that bb is for a bmx they had some crazy bb stuff like (euro/Spanish and American sizes...)

I'll check for sure tomorrow at work.

[yorkie_chris]

Yes it is cheap ass square drive. I can't justify spending 1000s of pounds to save 10 grams, especially on a device which sole purpose in life is to get me fit! There are proper bikes to build!

My mate who works in local bike shop swears by the things. Probably any decent type of sealed modern bearing is going to be better than some antiquated cone and cup.

If it is likely to cause issues I will strip it and fit a better one that retains the threads.