Bottom bracket seizes when tightening drive-side crank arm bolt. What'd I do wrong?
 

Hey there!

While I've been cycling a long time, I've admittedly only recently taken on trying to do most of my own repair and maintenance.

The current job I'm working on is replacing my square taper bottom bracket, and while I believe I've followed all the instructions (per Phil Wood) and various supporting tutorials properly, am now running into an issue where tightening down the drive-side crank arm bolt also stops the spindle from spinning. If I loosen the bolt, the spindle spins freely again...

I obviously can't ride around with a loose crank arm bolt, so am hoping someone might have an idea of suspect areas I could look at, and potentially redo, as I'm having a hard time figuring out what might be causing this.

The BB is brand new, and is the same taper and size as the two previous ones used. I just had the shell chased and faced, and nothing jumped out as "off" during install (installed dry, measured chain line, reinstalled with blue thread locker). The crank is a few years old, but I'm not sure how that could be responsible for seizing up the BB? Happy to be educated on that possibility though. I just don't know...

Thanks for any thoughts or insight you might be able to share, or any clues as to what I should investigate.

Cheers!

Could you have bottomed out the crank against the BB shell or the cup? Phil BB are adjustable R<->L and the
spindle may be a bit too far to L. Also which crank and which BB are you using, possible taper variance could
allow crank to go to far down taper with same result. Worn DS crank might also do same although usually when
this occurs the crank fixing bolt bottoms out on the spindle end instead of the crank.

You mention you followed Phil's instruction, if this is their style did you put the spindle in backwards? The drive side will typically stick out longer due to the gears and putting it in backwards can result in the chainring bottoming out on the chainstay or even the crank spider bottoming out on the BB shell depending on the crank.

Thanks for the response sch
Bottoming out is a possibility I'll have to look into... would the easiest way to check be adjusting it back to the right, and seeing if it's still an issue?
It is currently adjusted further left, to bring the chain in line with the single rear sprocket @ ~45mm, but is still within protrusion tolerance (less than 5mm beyond the shell).
The cranks are Sugino RD2, and the BB is a Phil Wood JIS 108mm.

Russ Roth , thanks for the reply.
Unless I really had a serious "senior moment", I don't think I installed it backwards, as I believe I followed their instructions about having the "L" of the "Phil" logo facing the drive side.
I suppose anything's possible at this point though?

Send pictures

Sounds like an older crankset that has been removed and re-installed a few (or many) times. Each time, the taper flats of the crank get pushed out a touch farther so the crank has to slide on more to tighten properly.

Or: manufacturing tolerances. Tiny differences in the taper size of the spindle will make noticeable differences in where the crank sits. (I've seen differences in Phil Wood spindles. Probably nobody's exactly perfect here.) Or perhaps both of these are happening. (As I recall, the flats are a 9 degree taper. At that taper, the crank position will change 6 times as much as the variation from spec taper thickness.)

Other possibilities: Any chance you've got the spindle swapped right side for left side? With most that's not possible but it can be done with some. Also there are two different tapers. Shimano uses one (as does Sugino and SR for most of their cranksets). Campagnolo and the high end Suginos use another. The two standards are the same taper so both can work with no harm to the crankset but where they sit relative to the frame is quite different. The Shimano standard is called JIS and the Campagnolo ISO.

For more info see the Sheldon Brown website.

I've always found that until I actually mount a crank, I don't know exactly where it is going to sit. (And I love Phil Wood BBs for the adjustability mentioned above. That and they will make any length and asymmetry for the listed price. You just might have to wait a bit.

Edit: is that crankset still on the bike? Get a headlamp and stick your head behind the seattube and under the frame and see if the crankset is hitting the BB or frame BB shell (or chainring teeth and the chainstay). That the crank won't turn is only a mystery until you find the contact,

Hmmm... So, some findings:
I adjusted the BB toward the drive side, so that there was a near equal protrusion on both sides.
Reinstalled everything, and still had the same issue.
Then I had an idea, and removed the drive side dust cover, re-tightened the crank arm down, and it spun freely.
So... that leads me to suspect that either the spindle length is too short (which would be odd, as it's the same as the two previous), or the crank is worn and seating too far down now?
That seem like reasonable assumptions to you all?
Per Rick's request, I tried to upload a few pics, but am apparently unable to (or external URLs), until I have 10 posts or more.

Giving this a shot for pics (replace "111" with "com": imgur.111/a/yQcIcTJ

Nope https://imgur.com/a/yQcIcT, doesn't come up

numlok , create an album - people can view photos in your profile.

numlok. how much clearance do you have between the left crank and the chainstay? (Crank on properly tight.) You need ~2mm so you don't hit the chainstay even doing massive sprints or hillclimbs. Anything beyond that can be shifted over to the drive side (assuming enough threads are engaged on the BB). If threads are the limiting factor (Phil's instructions suggest how far off-center you can adjust the BB position) call Phil and ask about a spindle/BB with more asymmetry.

In the old days, BB spindles were regularly made asymmetrical. My racing bikes' cranks were close to hitting the chainstay on the non-drive. It is now popular to make BBs symmetrical but it really doesn't have to be. Our bodies cannot feel the difference and the bike simply doesn't care. I've looked into this because my knees are very sensitive to Q-factor (the distance the pedals are apart or how bow-legged they make us). For me, no bike is too narrow and most, too wide. I buy Phil BBs with a spindle length that places the chainrings where they belong with the left crank just missing. (Note that different bikes have different width and thickness chainstays so this is a look and see deal, not something you can find in a spec sheet.)

Maybe you bought a BB with the wrong taper. Or your crank spiker has been pushed on too many times... too far. Can you show a picture of the crank installed tightly torqued on the BB with the bolt removed... to see how far it's pushed on the axle?

You don't have enough spindle on the drive side. You'll either need to adjust it out, or get a longer spindle.

Sorry for the delayed response, I was hamstrung by the restrictions of only 5 posts per 24 hours for new users.

I believe I've found the issue, but if anyone has further interest, I've also added an album of photos to my profile (can't add in thread per those new user restrictions), as well as a YouTube video illustrating the problem: youtu.be/V1qlRswqDrw (can't add urls due to that same "newb" restriction, so you'll need to copy/paste to view).

What I think is going on, is that while my previous BB had a 1mm shorter spindle (107mm vs the new 108mm), and worked great for years, it did not have a dust cap, and thus allowed the crank to go a bit further down the spindle, just slightly beyond the face of the BB cup.

Removing the dust cap on the new BB allows it to work the same way, spinning perfectly fine while fully torqued down, and not making any actual contact with the BB cup.

I think my tolerances were just too close initially, and that I should have taken into consideration that slight push into the hole of the cup, along with the slight added thickness of the dust cover.

I'd rather not ride without that cover, especially as I do ride in wet weather, so I think I'll need to look into getting a BB with a slightly longer spindle. Bummer!

I do appreciate all the time, thought, and suggestions y'all have offered though. Thanks!

Alluminium cranks get hollowed out over time. A new crank might have a snugger fit which in turn would give you the clearance you need.

I've use crank arms that would normally bottom out. I did it by adding a small soda can shim to each of the flats on the spindle. They've lasted for years. I glue the shim to the spindle with a gel type cyanoacrylic glue.

Cheers

I think unless you're married to that Phil Wood BB, the simplest solution would just be to use a different BB that doesn't have an "outie" dust cap system.

For all of $16, I just bought a 107mm (108mm actual) Shimano UN300 that is light, well-sealed, and twists easily and smoothly in the hand. Save the hack-fixes for when they're actually called for! :)

i just put a un300 in.....it sure seems to be an improvement over the un25.... works great