Plimogz

Hey,

So, long story short, I installed my new cranks and it doesn't feel like the bearings spin freely enough. I'm thinking excessive lateral pre-load from either over torque, or a slightly too wide BB shell which ends up compressing the stack a little too much, even with otherwise proper installation.

I'm looking for insight from any of you fine folks with experience with outboard BBs in general and ideally experience with RaceFace Atlas (FR) X-Type crankset installation.

Short story long--> I installed a RaceFace Atlas FR crankset into my Karate Monkey, and on account of insisting on doing everything myself, I had to cut a couple of corners which I would have otherwise loved to do by the book, but, lack of tools, you know...

Namely, I would've liked to face the BB shell, but I'd rather not go to an LBS, (and it's not like there are any open at 2 am, anyway), so I just made sure to remove all paint from the mating surfaces and give it a very light touch with a fine tooth file.

Also, I would've loved to torque everything exactly to spec, but I apparently lack the 1/2"->3/8" drive adapter I would've needed for one thing, and my 3/8" drive wrench doesn't go up high enough for the torque I would've needed for another thing.

Anyway, I followed instructions as best I could and now the cranks don't spin as freely as I might expect when I just try to give the a good push with my hand. Like, even though I try to flick them as hard as I can, they only rotate maybe 3/4 turn (edit: actually, upon further flicking, the cranks turn more like 2.5 times before stopping) before friction stops them.

I figure that the bearings may be a little "sticky", seeing as how even when I spun the inner races before installation they felt stiff, albeit every bit as smooth new bearings should be.

My thinking is that either over-torquing the cups could lead to this if the cups slightly deformed and squeezed the bearings somehow; or a wide BB shell (though it measured right around 73 when I checked before installation, but I don't have a Vernier handy at the moment, so I can't be that accurate) could lead to excessive thighness, which could throw the preload out of spec...

And of course, if the BB shell faces aren't parallel enough, that would probably explain it as well, but the build quality of Surly's frame looks pretty good, and eyeballing revealed nothing flagrantly askew. For what little that's worth...

***

And that's why a little reality check would be very warmly welcome are these things normally a little stiff out of the box? can I expect them to loosen up without it meaning that I'm prematurely destroying the bearings?

Thanks

DOS

Pinching bearings is more an issue with loose ball components (hubs, headsets, BB) than cartridge bearings so I doubt that is an issue. Cranks, particularly cranks with new bearings, shouldn't spin really loosely ( as in you give the cranks a spin and they go round and round dozens of times). Put chain on and turn the cranks either with your hand or go for a ride. If they turn smoothly -- no rough or grinding sensation if that makes sense -- I think you're good.

bradtx

Plimogz, New cartridge bottom brackets are often a bit tight. Once the bearings and races function fit to each other it'll spin more freely.

Brad

Kimmo

If you're getting two and a half spins when you flick the cranks it does sound a bit stiff, but since it's fresh out of the box I don't think it's too much to worry about; those big seals make a lot of drag when they're new.

It'll always be stiffer than a square-taper BB, but it should loosen up with use.

tomacropod

The efficiency of outboard bearing systems when unloaded is a little less than square taper systems because of the size of the seals, but when you actually ride the bike, the extra stiffness translates to higher efficiency. 2.5 spins is fine.

- Joel

HillRider

When you slid the spindle through the bearing cups did it slip right through the second cup or did you have to force it to align? If it went through with no force, your bottom bracket shell is probably plenty parallel and the drag you are feeling is just tight seals. If you had to force the spindle alignment to get it though the second cup, you have parallelism problems too.

Looigi

There should be no drag turning the crank beyond that created by the grease and seals. This will tend to decrease a bit with use.

Plimogz

Urgh! I hadn't thought about that simple diagnostic approach... Thank you for that.

And yeah, it was a pretty hard time pushing it through, though I did manage without tools. Unfortunately, I can imagine it going in easier... Although if they designed for a slight interference between the bearing race portions of the spindle and the bore diameter of their bearings... hmmm. Because in any case the parallelism wasn't so bad that the middle of the shaft put up any resistance, only the sections which are machined to fit inside the bearings (i.e, I had to force when I pushed through the first bearing and then push harder when came the time of pressing through both at once and into the final position)

But still, knowing this I really should had tried putting them together outside the bike just to get an idea for how the spindle/bearing interface felt without throwing the BB shell parallelism variable into the mix...

Thanks for the assist, HillRider -- always awesome to learn a little more craft. And many thanks to everybody for the feedback, its been very helpful.

Plimogz

Well, what d'you know, less than 10 miles of breaking in have loosened it up nicely and the cranks now spin a good five or six times rather than the 2.5 of this morning.

And searched for something and came across a page which I only very dimly remembered seeing a while back: https://surlybikes.com/info_hole/spew...ur_steel_frame -- the part about "Since Surly frames are faced prior to painting, it is possible to shave the paint off the head tube and BB shell ends with a carpet knife blade. This usually results in an acceptable result" is looking pretty acceptable indeed. Hopefully I'll be able to splurge on the necessary tools to face tubes in the near-future, although it's going to be a hard one to justify, even if it's just to myself and my own wallet.

But man is this new crankset stiff! The Monkey most definitely feels upgraded. Yippee!