Powertap maintenance & servicing

[rpedro]

Can anyone please let me know what the code is for the R129 bearings from Bearing Man? I would prefer buying them before taking my wheel apart :-)

 

"Bearing man have two version of the cartridge bearing - one for R69 and one for R129"

[Johan Bornman]

Can anyone please let me know what the code is for the R129 bearings from Bearing Man? I would prefer buying them before taking my wheel apart :-)

 

"Bearing man have two version of the cartridge bearing - one for R69 and one for R129"

 

It takes 4 x 6091 bearings. However, not all 6091s are created equal and on the Powertap it matters. The two bearings in the freehub are separated by a stupid soft aluminium spacer. It is so soft that it may even be Lithium, not aluminium (chuck water on and see what happens). Therein lies the problem. if the bearing's inside race isn't exacty as thick as the spacer, the spacer will deform around it and effectively become shorter, allowing the two bearings to drift and assume the wrong preload and; deform enough to "flow" over the race into the plastic seal and jam the whole kaboodle.

 

Many standard 6091 bearings have a stepped design on the inside race's outside cirumference which has to do with the seal design. Bearings that don't work here include Enduro.

 

Therefore I suggest you take a sample to the bearing shop and inspect the replacements for compatibility. Don't let them tell you it is only the ID, OD and thickness that counts. In this case there is more.

 

Further, PowerTap uses a generic freehub that I've seen on many other wheels. I can't remember right now which, but it is very common. This freehub is of poor quality in the alu version (a steel version also exists that performs better). The quality shows in the pawl cavity wear. The cavities where the pawls live wear backwards, deforming the seat and messing up the pawl performance. The way to check for wear is to remove the freehub body, remove the pawl springs, clean it properly. Now lay the pawl flat into its recess and see if it fits perfectly. If the recess is longer than the pawl itself, replace the body.

[Johan Bornman]

One more thing. When purchasing bearings, be a snob. Never ever under any circumstances buy a bearing made in India or China. I'm not saying they are all rubbish, but I haven't seen a good one yet.

 

And one last, last thing. Freehub body bearings are kinda special. There's usually two of them in there and they have considerable drag - enough to let the freehub not "free" perfectly and push the chain forward. This is not a fault, just a matter of bearing spec. Cartridge bearings can have super tight seals and lots of grease, or soft, poofter seals with very little grease inside. You actually want the latter.Better is not always better.

[rpedro]

One more thing. When purchasing bearings, be a snob. Never ever under any circumstances buy a bearing made in India or China. I'm not saying they are all rubbish, but I haven't seen a good one yet.

 

And one last, last thing. Freehub body bearings are kinda special. There's usually two of them in there and they have considerable drag - enough to let the freehub not "free" perfectly and push the chain forward. This is not a fault, just a matter of bearing spec. Cartridge bearings can have super tight seals and lots of grease, or soft, poofter seals with very little grease inside. You actually want the latter.Better is not always better.

 

Thanks Johan for all the usefull info. Can you recommend an excact 6091 bearing that I can ask for? Is there an additional code/make that will make sure that I get the correct replacement bearing?