I've been having issues with my crank bolts frequently coming loose with my Dura Ace FC-7600 square taper cranks. I was told its because I've been using a Shimano UN-55 bottom bracket. That's a 2 degree bottom bracket on a fine taper Dura Ace crank. I was told to either go with the Dura Ace bottom bracket made for these cranks or a Phil. I bought a Phil and had it installed today, hoping that will solve the problem.

Looking online, I'm reading that riding loose square taper cranks just once, will wear down the square taper and ruin the crank arms, regardless as to WHY they are coming loose in the first place. FML.

Gonna take the crank arms off tomorrow while the loctite on this Phil bb dries.

So just to get this straight, if the taper is rounded AT ALL, toss em' in the garbage?

Seeing that I'd want another set of FC-7600's and I will be waiting for 2-3 weeks for them to arrive from Japan, am I going to ruin the taper on the Phil if I ride the rounded out cranks in the meantime?

I hate bikes.

The BB taper is nearly bombproof when compared to a crankarm.
Don't sweat about the BB at all; leave that for your poor poor non - budget crankset that you possibly* ruined with a economy BB. Who knows, depending on the taper of the UN55; your original DA arms could still be salvageable.

Thanks. I was just thinking of this situation:

Cranks are ruined.
I ride them anyway til new cranks come.
New cranks come.
Damaged phil bottom bracket ruins 2nd set of dura ace cranks.

At that point I'd probably just sell my bike and go to Mexico.

Also, can someone please post a picture of a square taper crank arm that is slightly worn?
I've found photos of ones that are noticeably destroyed. But when I'm borrowing a crank puller at the shop tomorrow I need to be sure.

I don't think that the Dura Ace crankset used a taper that was anything different than the rest of the Shimano line-up. In fact, as far as I remember, there are only two tapers, ISO and JIS, and Shimano has always been JIS.

That being said, I've played fast and loose, put an ISO crank on a JIS taper and suffered no consequences at all. I know I'm not the only person to have done this; in fact I'm fairly sure Sheldon Brown even reported success himself.

More likely, you didn't tighten down your crank bolts enough and they just came loose. The taper could be messed up, but you might be able to make due by just really tightening them down something fierce. Use a torque wrench this time so you know what's enough, and then maybe exceed it by just a little.

And there is nothing you can do that will mess up the taper on your bottom bracket. Well, ok, there are things, but nothing that doesn't require extraordinary effort. Your Phil is safe, and will be for years to come.

Thank you so much for the info.

I'll be able to tell if the taper is messed up by looking at it? I've seen extreme examples that are obvious.. but what about something like this..
Here's photos of a used pair that are constantly being sold in Japan




Could these tapers be worn and messed up? Or is it real easy to spot by looking at them?
If the naked eye can't really see it spot-on and my cranks look like that (theoretically, lets say those crank arms are toast) this would explain why the mechanic didn't say anything today. I told him the crank bolts had been coming loose so he recommended some Sugino 8mm hex crank bolts.

And you go judge by the inside of the crank arm, not the outside?

Those look fine. You'd know by looking if it was stripped bad enough to worry about it.

phil wood is always the best and always worth the money!

Even adriano agrees without even a smidgen of sarcasm. That's when you know it's good for you.

Invest in a torque wrench or have a shop do it because it is clear you're not doing it right

BB spindles are hardened steel; crank arms are soft aluminum. The chances that your crank damaged the BB spindle are vanishingly small.

Your cranks are fine. Your BB spindle is also fine.

You can ruin a set of crank arms if you ride them when they're loose but often it doesn't happen so quickly. As long as you catch the within a few dozen miles of being loose and don't mash up any hills you'll generally be alright. Next time you install them make sure all mating surfaces are free of lubrication, grease the crank bolts and use proper torque and they won't come loose unless something is wrong.

Buy a torque wrench. Read this. And hate the player not the game, son.

You can also ruin the cranks if you over tighten them. Grease the bolts, grease the bb cups and use a torque wrench.

I think greasing square taper BB spindles is frowned upon.. mine always creak when i do that

Yeah, wasn't thinking. Fixed.

There have been a few good religious war threads about greasing spindles. I never do it personally.

As for your cranks being good, erpdat, I'm with Spoonrobot - good chance they're still good. Depends on how loose you let them get, how long you rode 'em loose, how much you stood to pedal, etc.

I'm 50/50 on re-torquing cranks I rode loose. Wasted an old Suntour that I put too many loose miles on. Still running Suginos that I didn't torque enough upon install and creaked out on me a few times.

Suginos were the first I installed with allen crank bolts so I wasn't getting near enough torque with the little L-shaped wrench, gotta get an allen socket and put it in a ratchet to get the leverage. Torque wrench even better, but...

It depends on what you personally think is best. I find not greasing the spindle works best for installation of crank arms that have already come loose due to insufficient torque during prior assembly. Inevitably these crank arms will click or creak after some use and require a lubricant to be sprayed into the union so it's been a wash for me anyway.

During initial assembly, I have done both and for my purposes (road riding of rolling terrain in generally dry to moderately wet roadways, no rain) I find it makes no difference. Setting the right torque has shown to be more important.

Jobst Brandt says lubricate during assembly, Campagnolo says do it dry. So it's really up to you.

https://en.wikipedia.org/wiki/Bottom_...tapered_cranks

https://sheldonbrown.com/brandt/installing-cranks.html

Its hard to say how many miles I've logged on them loose. I wasn't checking everyday and the first time I noticed they were loose.. well.. I think they were loose for quite a while.

I'll know for sure tomorrow. The good news is DA 7600 cranks are widely available on ebay used. $150-$250 shipped from Japan.

Although I'm not sure if its worth it at this point to spend an extra ~$100 to buy a brand new pair. I mean, as long as the taper is square, who cares right?

Hopefully I am fine and can keep riding these ones I've got.

Thanks for all of the help. Very, very appreciated.

I believe that was sarcasm.

/you'vebeenduped

Or maybe you have.

Adriano's sarcasm of philwood and my sarcasm of adriano liking philwood.

i n c e p t i o n

The snow fortress is at my workplace. 'just sayin.... it's more of an academic prison of a library for students through.

Alright, both of the crank arms were coming loose pretty frequently. And I've read NDS crank arms are the first to go.
Just stopped by my friend's and popped off the NDS crank arm. Looks absolutely perfect. Didn't even feel the need to check Drive-side as there would be no reason for the NDS to be perfect and the Drive Side to be destroyed.

Must've been that Shimano bottom bracket.. or the old crank bolts I just replaced with 8MM Hex Shimano ones.. Weird.

Either way, stoked.

This makes very little sense.

adriano...we need to talk. I'm LATE.