bdcheung

My Ultegra Hollowtech-II bottom bracket is pretty new but seems sluggish. With the chain off, the BB seems to be causing some frictional resistance when I try to turn the cranks. Is this normal? Is there something wrong with the BB?

HillRider

There will be a slight amount of resistance caused by the grease and seals on any new bottom bracket so some resistance is normal. Without seeing your actual bb, I can only guess if the resistance you are experiencing is in the normal range.

bdcheung

Ok, the best I can describe it is such:

When I spin the cranks with the chain off, they will rotate freely but certainly not to the extent that, say, my front and rear wheels do. It's not like I have to struggle to spin the cranks, but it doesn't spin forever. I guess it's not supposed to.

HillRider

Your bb sounds perfectly normal. Almost no crank will "spin forever" the way a well adjusted wheel will if for no other reason than the "flywheel" effect isn't as large.

bdcheung

k, i feel better now. thanks!

Rowan

Well, don't feel too much better.

From what I gather, there is now a greater need for the BB shell to be faced prior to fitting the new Hollowtech II external bearings because these bearings mate up to these surfaces, and rely on these surfaces for spindle alignment, unlike the internal cartridge types that are independent of this alignment (my reference is the Park Tool site).

It also seems we are getting more and more questions about the lack of free spin on these types of bearings compared with previous types. Misalignment of the two bearings through misalignment of the BB shell faces may be a cause of this "binding" or lack of freespin.

It seems that in order to go "forward" with the new external bearings, we need to go backwards to requiring accurate facing of the BB. Marvellous what marketing spin can do... and everyone falls for it.

Anyway, to the OP: Who fitted the new crankset, and was a facing job done on the BB beforehand?

And yes, I agree that new seals might cause some lack of freespin compared with unsealed ball-and-cup bearings... but surely not to this extent where the friction is so evident.

bdcheung

my LBS fitted the crank and BB; previously I had a square-taper cartridge BB. I don't know if it was faced, but I'll take it back to get reemed (sp?) and faced.

HillRider

If the spindle and crank turn freely with no binding at any point in the rotation, you are fine. As noted, no bottom bracket, particularly a new one, turns with the effortless ease of a wheel.

Rowan is correct that external bearing bbs (like the Hollowtech II) are more demanding of bottom bracket shell alignment than earlier designs but it doesn't sound like you have that problem.

Whatsisname

If you have only the drive side crank arm on, and you set it off center somewhat, how high can the bottom bracket hold it up before it falls back to the center? I had an old bottom bracket that was toast, and if I turned the crank so it was sideways the friction of the bottom bracket could hold it in place. When I got a new one, it had a fair amount of resistance in it, however once I put a crank on it could only hold it up about 1.5 cm's to the side of center before it would fall back to the center.

Rowan

No, not reamed. That's only for seat tubes to remove burrs. Just facing for bottom brackets.

leejb2

I think the OP might have meant chased instead of reamed, which wouldn't hurt. But, if the cups went on without trouble the first time, there is probably no need.