Evening all.
Looking some thoughts and opinions on a recent tech issue I've had.
I was out cranking through the KMs on my carbon hardtail, it's a Vitus Rapide, with a press fit BB and Shimano MT501 crank set. Everything was checked prior to the ride & showed no play. Half way through the ride, without warning I went to throw down the watts on a climb, ya know, cause I'm riding a carbon hardtail so obviously watts are flying, I could power a small village with the wattage... Sorry, I digress. Anyway, I went to pedal up this climb and my foot slipped. Weird, right?! That's what I thought as to the best of my knowledge I'm clipped in. I look down & I'm still clipped in, just to the pedal & crank arm but no longer to the bike.
After a second of wondering am I hallucinating from all the wattage burning I'm doing, I realise that it's kinda fucked. So I hop off, struggle to unclip my foot & the crank & have a look. It's somehow managed push the entire half of the BB out of the frame, bearing & cup. Obvioulsy that put pay to the ride & without the very friendly couple that passed me as I'm stood there scratching my head as to what has happened, I would have had a long push back home cursing every part of the bike.
I've subsequently checked the frame since getting home, doesn't seem to be cracked or damaged. Pressed the cup & bearing back in & thought I was sweet. But next ride out, within 5 minutes, the same thing has happened again. Crank off, bearing & cup out and me stood there wondering if the bike gods hate me much?!
Any suggestions or thoughts as to how or why it's pushing the entire non-drive side of the BB out of the frame?
Thanks for getting this far & any help offered.
Trying to picture this; so the NDS arm and pedal are coming off the crank spindle? Is there a bolt that's supposed to hold them on and if so is it installed and torqued correctly?
The BB cup coming out sounds like the BB shell may be out of spec, I haven't used a PF BB in years but I remember them taking substantial effort (and tools) to install remove.
Sounds like all those watts rioted.
The bb might be trashed but that isn’t causing your cranks to come off. Try taking the pinch bolts out all the way and clean every thing, grease them up and tighten the plastic cinch bolt just enough to eliminate play. Then tighten the two bolts one at a time then repeat. Torque spec is like 14 I would go closer to 20. That is all assuming your spindle is long enough to engage the crank arm fully
Yup this is the first thing I would check, if the pinch bolts are loose it will allow the crank to walk off the spindle and possibly then the cup out of the frame. That torque is pretty critical.
Also is the BB cup a proper pressfit still?
First off, please forgive my ignorance in all of this, as I may not know even the correct terminology. I am building a bike on an old GT avalanche frame with components that I think are expensive, but I'm sure that none of you all would. I am trying to determine what headset size I need to buy..... this is proved much more complicated than I had ever. using calipers both upper and lower part of the steering tube measure at 40 mm but I cannot find any headsets that say that they're 40 mm can you help me figure this out and maybe recommend a mid-level or inexpensive but good headset?
It's gonna depend on how old the frame is (a pic would be helpful if you aren't sure).
(Depending on the headset type you may need a press to install it snd unless you have one it will probably be more cost-effective to but the headset from a local shop and have them install it).
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