melon

i recently removed my cranks using this park tool: https://www.parktool.com/products/det...6&item=CCP%2D2

i have the type of spindle with a threaded rod on the end where a nut sits to hold the cranks.


i dont really understand how i re-install the cranks back onto the spindle. how do i press it back onto the tapered spindle?

im guessing i dont just push it on tight and do up the nut, as i had to use quite a bit of pressure to undo them with the removeing tool.




ive done some searches but i only ever find info on how to remove the cranks.

many thanks

sfclearwater

You just place the arm back on and tighten the nut (or more commonly a bolt) to set the press fit. It is best to use a torque wrench for this so you get it right, although lots of people just do it by feel.

Park tools has some torque recommendations on their site:

https://www.parktool.com/repair/readhowto.asp?id=88

JanMM

Yep, that's right, you "....just push it on tight and do up the nut." Pretty much the same drill for axles with nuts or with bolts. Agree a torque wrench is ideal. Or, just a socket wrench if you don't put way too much juice to it.

San Rensho 

Make sure the spindle and mating surface of the crank arm are perfectly clean and greased. Then use a torque wrench at around 20 lbs-ft. The less torque you use the better as every time you take it off and put it on, it stretches the soft aluminum of the crank arm, which makes the crank arm fit closer and closer to the BB, changing the chainline, among other ills.

HillRider

Agree so far.

Here I have to disagree. Too little installation torque will guarantee the arm comes loose and the crank will be ruined. Torque the nuts or bolts to the manufacturers full recommended value and do it ONCE. I.e. don't go back and retorque them every few rides.

I've remove and reinstalled the same square taper crank a dozen times and the chainline never changes if done properly. What does stretch aluminum arms is retorquing at frequent intervals after the initial installation.

rmfnla

I'm waiting for the inevitable onslaught of contrasting opinions...

krems81 

Many people believe there should be no grease on spindle, it makes the taper of the cranks slide on too easily and deform under torque. I'd be interested to hear contrasting opinions on this.

Anyhow, with or without grease (if you use it, just a tiny bit), just slide the crank onto the taper, and tighten down pretty hard. You don't want to whale away and use all your stength, but you want to put a good 100 pounds of torque on it, if not more. There's the vague possibility of overtightening, but its way better than undertightening and having your crank arms come loose and start jiggling around, and being deformed beyond use.

Berre

Right. Let's start a flame war close to Xmas

I have mounted many crancks with and without grease. Both ways, they stayed on and ran fine. I always take great care about cleaning the square holes with an old tooth brush prior to mounting them.

When it comes to removing the cranks again, I found it easier to take them off when they had been greased. I noticed less corrosion marks on the spindle and in the square hole. The grease keeps water out. I guess, mounting paste would do the same.

JanMM

No grease on the tapers.....................Merry Christmas!

Shimagnolo

Call me crazy, but how about following the MANUFACTURER'S instructions?
I have the Shimano instructions for an XT crank in front of me: 305-435 inch-pounds, that is 25-36 foot-pounds.

Grand Bois

DannoXYZ 

Where are you getting your 100-lb*ft torque numbers? You certainly haven't done it yourself or you'll find that the bolt will snap at about 50-60 lb*ft.

For the OP, yes, 25-36 lb*ft torque is A LOT. That's why it was so difficult to remove with the puller tool. Slipping a 12" pipe over the handle of the extractor makes it MUCH much easier to pull a crank. You'll want to make sure you re-install it to that torque-spec or else you'll run the risk of having the bolt coming loose and the crankarm will bugger itself on the hard steel spindle. Just do a search on here for "loose crankarm" and see how common this problem is.

You'll need an automotive-style torque-wrench with at least 10" handle to generate the required torque. Itty-bitty L-shaped allen-keys or the short 14/15mm Park Tool won't do it.

BTW, the cylinder-head bolts on my car require 80 lb*ft of torque.

HillRider

The highest torque value I ever had to deal with was in graduate school the mid-'60's when I was using a 10,000 psi autoclave for high pressure hydrogenation reactions. There were 10 1" Grade 8 bolts holding the lid on and they had to be cross-pattern tightened, in stages, to 275 pounds-ft. I had a 3/4" square drive clicker-type torque wrench about 3' long and had to put one foot on the walls to get to the required torque. Those things were TIGHT!

rmfnla

Crazy? How about delusional!?

rmfnla

I think I'm going to allow you to reply to all the "stuck seatpost" threads; you obviously have the experience!

DieselDan

Never grease a square taper. You could easily split the crank arm.

HillRider

No you can't. If you follow the manufacturer's recommended torque, or even come close, the crank arm's square hole won't distort or break.

I do grease the spindle on square taper bb's, torque the cranks as recommended and have never damaged one in 25 years of working on them. In fact, many of these cranks have been removed and reinstalled numerous times and always remain tight but the chainlines do not vary at all after a removal/replacement cycle.

I know Campy firmly recommends the spindles remain dry but they have never given an explanation as to why. I've discussed this with several mechanical engineers and they have no idea why either but think Campy's recommendation is a bad idea. They tell me greased tapered fits are far more uniform.

rmfnla

That's a new one to me.

khearn

I've heard both ways recommended, greased or ungreased. I've also read that some manufacturers design with greasing in mind, but most design with dry in mind. But I don't remember which manufacturers want which. I found it pretty easily via a google search last time I put cranks on (which was just a couple of weeks ago). I lightly greased mine, then wiped it off.

One thing you should definitely do is lightly grease the threads, either of the spindle or the crank bolt, depending on what type of spindle you have. You should also rub just a bit of grease on the side of the nut that pushes against the crank, or the underside of the bolt head where it pushes against the crank.

And finally, if you're going to use a torque wrench anywhere on a bike, this is the place to use it. Most threaded fasteners need to be torqued correctly just to make sure they stay in place. But that crank bolt/nut needs to be torqued correctly to make sure the crank is pushed onto the spindle far enough to have a good mechanical connection, but not so far as to damage the crank. Sliding an aluminum crank onto a tapered steel spindle makes a lot of pressure, and it is very possible to split the crank arm if you overdo it. But if you underdo it, you'll end up with a loose crank halfway through your next long ride, probably 20 miles from home or the nearest bike shop, leaving you with three options: walk home, ride home using just one leg, or ride home destroying the loose crank in the process.

(Hmmm, my spell checker thinks "overdo" is OK, but objects to "underdo"... It also seems to dislike Scooby Doo)

Silent Otto

I always find it curious when talk turns to torque wrenches in the bike shop...we're fixing bicycles here, not space-shuttles.

An experienced mechanic will know that bolts either need to be tight, or really tight. Crank bolts should be really tight. Caution should be used if you have forearms like Popeye, otherwise, have at 'er.

The anti-corrosive properties of the grease is most beneficial to the steel axle.

HillRider

Well, it's here! Your wish is our command.

Correct, but the key word here is "experienced". Mechanics who work on bikes every day can develop a good feel for the correct torque without a torque wrench. Those of us who work only part of the time or newbies, need quantified measurement. The alternative is a learning curve that includes a bunch of excessively loose parts and/or broken bolts.

Sheldon Brown had the same disdain for torque wrenches but he had something like 40 years of daily experience. Most of us don't.

rmfnla

Not so much a wish as an expectation.

Happy holidays, HR; I always enjoy reading your contributions!

xpc316e

I am entering into the grease/no grease debate, but the bit about the chainline altering is bunkum. Consider how much the chainline changes when you shift from the smallest ring to the largest on a trple set-up, and that doesn't cause problems. Therefore the couple of thousandths of an inch that may happen when you re-install a crank isn't going to matter one jot.

San Rensho 

Well it does matter when the crank arm goes all the way in, the bolt bottoms against the spindle, not the crank arm and the small chain ring now interferes with the frame. All this can happen if you overtighten the crank bolt. Ask me how I know.

tmh657

ummmmmm, how? I find that annoying