Swapped Cranks - New Crank Won't Spin Freely

ryan_w-2

Up until 00:30 last night sweating, bleeding and swearing. :roll:

I changed my BB30 SRAM Force cranks (68mm) to BB30 Rotor 3D+ cranks (73mm) on my CX bike with a PF30 BB (SRAM).

The SRAM cranks spin freely when torqued up, the Rotor cranks essentially don't move at all.

I have the correct spacers in, axle is lubed, the pre-load is backed off, BB bearings are silky smooth.

It makes me think the bearing covers / seals are fusing with the bearings when the Rotor cranks are tightened.

Anyone else had this issue before?

Could it be that I just need to try some different (Rotor?) bearing seals?

I literally used everything that was on the bike with the SRAM cranks, so something it up and its pi$$ing me right off.

Cheers in advance!

pilot_pete

Are you sure you have fitted the right spacers? Take a look at this chart https://www.rotor-shop.nl/contents/nl/ROTOR_SPACERS.pdf it looks like an 11.5mm each side plus an additional 0.5mm on the drive side.

PP

sungod

yeah, sounds like wrong spacers

the correct spacers are those which allow the cranks to rotate freely but without play (and distributed such that the cranks are equidistant from the centre line of the bike)

ryan_w-2

Pilot Pete wrote:

Are you sure you have fitted the right spacers? Take a look at this chart https://www.rotor-shop.nl/contents/nl/ROTOR_SPACERS.pdf it looks like an 11.5mm each side plus an additional 0.5mm on the drive side.

PP

That chart is wrong. I’ve just removed the cranks from my S5 (BBright), and it only have 0.5mm spacers each side. There is no way an 11.5mm spacer would fit.

As for my currrent problem. The cranks are spaced correctly. It’s the point that when tightened, it stiffens up.

Having too many spacers wouldn’t cause this, it would only cause the cranks not to tighten up enough. Having too little would just give the cranks play.

Everything is fine until clamping pressure to bearings applied.

I’ll try the bearing cups tomorrow and report back.

pilot_pete

Can’t comment on the chart being wrong for your BB as mine is not the same but I found the chart to be correct for mine. I am assuming your S5 is a rotor crank too?

Once again, I am not sure about your exact setup, but putting too many spacers in on my Rotor 3D+ crank would cause me to be tightening the crank arm against the bearings. In effect they are shortening the crank spindle so as you tighten the crank up the arm will start exerting pressure via the spacers on the bearing inner race before the crank is fully tightened. Side loading the inner race whilst the outer is held firmly in the frame will cause your bearing to lock up and might even damage it.

If you remove all spacers and undo the fine adjuster fully, then fit the crank, once tightened do the cranks spin freely but with side to side play? If so, your problem must be with either too many spacers or your press fit bearings are not pressed fully home properly.

PP

step83

I got this swapping cranks Rival/Quarq on a GXP, make no sense both are as the only thing I changed was the crankset.
Id take the bearings out and try without. My Quarq is meant to be 73mm, fitted it as such and same problem you ad, fitted it as a 68mm an it was fine. There is no logic, just use the wavy washer if you have one.

pilot_pete

Step83 wrote:

I got this swapping cranks Rival/Quarq on a GXP, make no sense both are as the only thing I changed was the crankset.
Id take the bearings out and try without. My Quarq is meant to be 73mm, fitted it as such and same problem you ad, fitted it as a 68mm an it was fine. There is no logic, just use the wavy washer if you have one.

Not sure I understand how taking the bearings out and fitting the crank without will help?

Rotor 3D+ has an adjuster to take up play, so I’d just put the correct spacer on the drive side for correct chain line and then try taking up the play with the adjuster on the opposite side. If it is excessive, back it off and try 0.5mm plastic spacer washer(s) until you get to the point of only needing a small turn of the adjuster to take up the final play.

PP

ryan_w-2

Fixed this is the end...

It was a matter of 2mm too many spacers, once torqued they were loading up on the BB bearings.

Tried a few different combos in the end, torqued up the crank bolt and then used the preload nut to take out the tiny amount of play.

Happy days, now have a power meter on my commuter.

As for the install of the Quarq on the S5, took 5 seconds and went on perfect first time (however, did have to machine down the chain ring for the spider to fit).

pilot_pete

Excellent!

PP