Cobb 155mm crank.. should there be play when installed?

C

cpml123

Zen MBB Master
That's quite an accomplishment that you got the wave washer on the spindle. :) I gave up after 10 min.

I am guessing you should leave the washer on the drive side but take the spacers off. Then tighten the crank arm in steps as we did... Tighten it to 35 ft lb. If there is play, loosen by a few turns and re -tighten to 35 ftlb. If there is play, loosen and tighten again.

Mine is still tight so far and spins fine when no chain is attached.
 
ReklinedRider

ReklinedRider

Zen MBB Master
ccf said:
I put a 145mm Cobb crank on my V20 a few months ago, and I had the same issue. I "solved" it by using the spacers. But the crank keeps coming loose. If I really tighten it tight, then the bearings feel way too tight; the cranks don't spin much when the chain is off. I have the RWC BB with ceramic, angular bearings. Should I take the cranks off, torque it unreasonably tight, then re-install it without the spacers? BTW, I have the wave washer on the drive side.

-Cliff
Click to expand...
Cliff, what spacers did you use(how thick are they)? Some spacers are meant for use with MTB BB shells and shouldn’t be used with road bikes.
I’m still perplexed by this prb with the Cobb cranks.
Like cpml123, I’m impressed that you got that Cobb-supplied wave washer over the spindle!
 
ccf

ccf

Guru
I had two spacers in each side, between the frame and the BB cups. Two of them are 0.100" and the other two are 0.038". I removed all four, put everything back together, and torqued the crank down with every ounce of strength that I have. My wife had to hold the back end of the Vendetta down. I was able to get the crank screwed in so that there is no longer any side-to-side play without the spacers. And the cranks spin super easily, just like Ratz' video of the XD-15 BB. I did find some metal shavings on the sleeve between the cups. I couldn't figure out where they came from. The bearings turn smoothly, the BB threads are not stripped, and the crank threads were not stripped, either. So I just cleaned them up and re-greased everything before doing the super unreasonably tight torquing. The wave washer is installed on the outside of the BB cup on the drive side. It fits easily over the axle of the crank, so they must have sent us different sizes.

I rode the bike hard in a TT yesterday. It held up fine and didn't come loose, so hopefully I'm good to go.
 
C

cpml123

Zen MBB Master
Congrats!
Good to know about the wave washer. I will keep that in mind if I need to change the BB in the future.
Michael
 
jond

jond

Zen MBB Master
Just got my 155 mm crankset Cobb. Could only fit wave washer on non drive side.

It must go there. Flattening it out won’t make it fit ......

So I’ll see. Using Cobb supplied B.B. not as easy turning as ultegra 6800. But it’s early days. Sorry for flash.

2E3688D1-164F-479A-81E7-CE2ECF61CBAE.jpeg D104ACEA-3A81-401B-87AA-BB9EC4AB4F4C.jpeg

After a one trainer ride the B.B. loosened up quite a bit.

I did not adjust boom but will likely try a slight leg extension.

I could feel the reduced pedal circle. I had 170 mm ultegra crankset on.

So indications are good but I need to take it out on road once rain stops.
 
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