Crank axle too short?

The spirit of Grav-lo-cross. No but seriously, cyclocross and gravel go here!

Moderator: Moderator Team

Post Reply
janberto
Posts: 13
Joined: Fri Aug 05, 2016 10:50 am

by janberto

Hi all,

I have a Merlin Malt G2X frame with a standard 68mm BSA bottom bracket. I have installed a Shimano BB. The Ultegra crank I had installed before worked fine, but now I have a different crank (Senicx GR3) and it looks like the axle is quite short. I would be happier if the axle would have been a couple of mm's longer.

Image

Is there a different BB-type that is narrower that I am not aware of? Would you consider this safe?

Greetings,
Janberto

stalkersk
Posts: 48
Joined: Fri Aug 26, 2016 10:44 pm

by stalkersk

No spacers under BB on driveside?

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



janberto
Posts: 13
Joined: Fri Aug 05, 2016 10:50 am

by janberto

No, no spacers.

joejack951
Posts: 1116
Joined: Fri Feb 18, 2005 6:50 pm
Location: Wilmington, DE
Contact:

by joejack951

Just like a threadless headset, there needs to be a gap to ensure that the bearings can be properly preloaded. Perhaps you already know this but feel that the current gap is still too large? It is hard to tell from the pic but it seems to be not more than 3mm. Accounting for the stack up of tolerances, that doesn't seem excessive but maybe a bit conservative. Does the design of the preload bolt necessitate some of that gap?

janberto
Posts: 13
Joined: Fri Aug 05, 2016 10:50 am

by janberto

Some gap is indeed necessary, like with the standard shimano cranks. However, I just had the feeling the gap is larger then strictly necessary.

User avatar
ms6073
Posts: 4118
Joined: Fri Jul 23, 2004 8:24 pm
Location: Houston, Texas

by ms6073

janberto wrote:
Wed Sep 28, 2022 4:33 pm
Hi all,

The Ultegra crank I had installed before worked fine, but now I have a different crank (Senicx GR3) and it looks like the axle is quite short.
Whats to discuss? If the Ultegra crank worked and that is the only thing that you changed, assuming there is not some kind of o-ring or spacer on the drive side, then your new crank spindle is too short! Are you certain the driveside of the crank is fully seated against the bottom bracket?
- Michael
"Solving problems you didn't know you had in ways you probably won't understand"

joejack951
Posts: 1116
Joined: Fri Feb 18, 2005 6:50 pm
Location: Wilmington, DE
Contact:

by joejack951

janberto wrote:
Wed Sep 28, 2022 7:33 pm
Some gap is indeed necessary, like with the standard shimano cranks. However, I just had the feeling the gap is larger then strictly necessary.
I agree on the 'larger than strictly necessary' just eyeing it up. I don't think it's particularly unsafe, though. Why not measure the actual gap and give that feedback to the company? They can tell you if things are assembled properly or not. All the rest of us can do is speculate.

If this was my bike, I'd mainly want to see that the outer pinch screw's outer diameter was at least even with the edge of the crank spindle, if not offset inward a millimeter or two, so that the clamping force is directed solidly through the spindle. Your off-angle pic appears to show it that way but it is hard to be certain.

by Weenie


Visit starbike.com Online Retailer for HighEnd cycling components
Great Prices ✓    Broad Selection ✓    Worldwide Delivery ✓

www.starbike.com



User avatar
robbosmans
Moderator
Posts: 2245
Joined: Sun Aug 26, 2018 12:40 pm
Location: Central Belgium
Contact:

by robbosmans

Personally I would just get a narrow wide chainring for your Ultegra crank

Post Reply