Hey quick question. I’ve greased my splines with anti sieze on my isis hubs, do I need to on my square tapers? Got some square taper cranks that I want to put on my 36, and not sure if I should anti sieze the square tapers.
Thanks.
Anyone? I’ve read to grease them, and I’ve read not to grease them. Anybody know anything definitive?
I’ve greased mine for years with no adverse conditions. I use loctite on bolt.
Well, nothing definitive, but I can say that in the machinists world, where taper fits are very common, nothing but coat of light oil is ever used. Personally I put mine together with a little WD 40, torque with a torque wrench to 35 ft lbs, ride for a day, then retorque to 20 ft lbs. It seems to stay right there after that.
Sam
Alright. Thanks guys!
Grease is fine. When I put cranks on I grease the tapers, tighten them, ride for about 100 meters, re-tighten, ride for about a mile, then tighten them a final time. Grease, oil, or anti-seize helps prevent corrosion at the interface so they will actually come off when you want them to. Never ride with a loose crank. They get rounded in no time.
Using anti-seize is particularly important when attaching an aluminum part (like many cranks) to a steel shaft. Bare steel will gall bare aluminum. It also allows you to get an accurate torque setting. I realize some (many?) guys don’t do this (see recent thread regarding pedal washers) with apparently no adverse effects, but this is basic metallurgy and engine mechanics. Talk to a race car mechanic. Every bolt gets torqued, and the only way to insure an accurate torque application is by using anti-seize. So take it for what it’s worth, you’re doing the right thing. Most commercial anti-seize is a molybdenum disulfide compound, but as mentioned above, other lubricants also work. (I use white lithium grease most of the time myself.)
Got r’ dun. Thanks guys. Decided to use anti sieze, and now just have to remember to tighten my crank bolts every mile or so on my next ride. Seems like during the initial tightening, they take forever to get real tight.
Anyway, love the 150’s over my 114’s. Big steep hills, here I come!
With a few rare exceptions like rods and cylinder heads, bolt torques are always specified as used on clean, dry threads. Lubricating or greasing a thread and then tightening to dry torque specs is a very common way of ruining expensive mag wheels on cars - most, if all wheel manufacturers are explicit about using only dry, clean bolts tightened to factory torques. Using dry torque values on lubricated bolts has ruined a lot of aluminum wheels, cases, covers, threads, and probably square taper cranks too.
Anti seize of some sort is a very good idea, but a bit of light oil is plenty. Grease is specifically designed to keep things moving under extreme load/pressure. I’m sure it is an effective anti seize too, but its EP characteristics aren’t ideal for keeping tapers from moving. That said, I’m absolutely certain its fine; tons of people grease square cranks with no problem. I’d just be careful with using too much tightening torque.
Sam
I always thought you wanted them as tight as possible?
Well, you can break bolts. It would be a real pain to get it out if it broke off inside your hub.
I think 30 ft/lbs is the typical value, using a torque wrench. If you’re just using a hex wrench, then yes, in my (limited) experience, this translates into about as tight as you can get it without injuring your hand.
As we’ve seen, there is a variety of opinion regarding how, when, where, and if the use of anti-seize is recommended. Do a web search on the subject, you’ll find this subject debated at length on the bicycle forums as well.
In the end, one’s personal experience is the best teacher, in my view.
Why do you need to tighten to higher torque, then retorque to a lower value?
I’m not using a 3 foot long allen wrench, just a run-of-the-mill 4-5 inch one, so I don’t think I’ll break the bolts…
Thanks for the info guys.
Yeah - with a wrench like that go ahead and grease all you want, you’re not going to get enough torque to over tighten. But I would check it after every ride for a while.
The reason I tghten to a high torque initially (30-35 ft lb) is to solidly bed the cranks on the taper. But I’ve found that if I continue to retorque at that value after riding it never stops tightening, which means the metal is getting distorted. If I back it off to 20 ft lbs it seems to stay there indefinitely.
As LanceB noted, there is a lot of discussion on this on the web. That’s a sign that there are a lot of perfectly good ways to do this but somehow it can be screwed up too. Don’t lubricate everything and then repeatedly retorque to 30+ ft lbs - you’ll eventually split the cranks. Don’t let them get loose. Other than that everything is good.
Don’t do that. Tighten properly once and then leave alone. That’s how I’ve always installed cranks (I use a torque wrench and 35ft lb for square taper) and I’ve never had one come loose - I’ve done a lot of them.
The myth of retightening arises because the tightening torque on the bolt will decrease with riding - people imagine that the bolt is coming undone and so needs retightening. It isn’t and doesn’t - the crank is simply squirming up the taper to the point where the elastic tension from the bolt is equalled by the elastic tension from the taper. No need to retighten the bolt as the remaining elastic tension is quite sufficient to prevent it unscrewing.
This balance isn’t achieved in the first place because of friction, which is why using grease is a good idea - as discussed previously, grease helps to provide a more consistent initial fit by decreasing the effect of friction. If you install on dry tapers then you will get a much larger variation in the installation due to friction.
I wonder which parts the torque values are most critical for…
If torques are specified for dry threads then it’s only because companies are pandering to the myth. As mentioned above, it’s impossible to get a consistent tension with a dry thread. Not that I’m convinced most people who think they’re installing with a dry thread actually are - I’ve certainly never seen a mechanic degrease a thread before attaching a nut. If wheels are getting ruined due to too much torque then I’d suggest it’s far more likely that garages are simply setting the torque too high on their tools (from experience of trying to undo wheelnuts after taking my car to the garage). That or simply not using a tool without a torque setting. I’d estimate the number of square taper cranks which have been ruined due to greasing the tapers and bolt threads to be approximately zero - though plenty have been ruined by continual tightening, which is often attributed to having coincidentally lubricated the interface.
In proper industry mating parts and threads are always lubricated.
I don’t picture it this way when tightening the tapered interface between a soft metal (crank) and a hard metal (hub). I don’t imagine that the bolt is loosening. Instead, I picture the irregularities in the soft surfaces compressing as the cranks are torqued back and forth on the axle. I see it as the soft surface conforming to the hard surface. It acts as if the tapered hole expands as the surfaces mate more closely but it’s just the soft, raised areas compressing.
Of course, I picture a lot of things incorrectly.
Yup, I think that method is perfectly sound. If you indeed did retorque your greased taper to 35 ft lb regurly you’d slowly drive the taper through, probably cracking the crank arms. But getting that initial distortion that Harper imagines is probably a good thing. I’d venture that my retorquing to 20 ft lbs is overkill.
Unless otherwise stated, it is standard mechanical engineering practice to specify torques as used on dry compoments or specify what kind of lubricant or thread locking media is to be used. The reason for this is that the amount of force generated by tightening a lubricated thread to a given torque can be 2-3x the force generated by tightening the same threads when dry, and selection of the lubricant can put that force anywhere in between.
So - if you’re going to use grease, or even light oil, be careful not to over tighten. Its probably a lot harder to over tighten a dry joint, but then you have a greater risk of it coming loose. Pick your poison.
Sam
Wow. This thread has gone a direction I never thought it would. I’ve never worried about over tightening cranks, but now I’m waiting for my 36er to catch on fire and crumble into ashes. :o
In all seriousness though, yesterday I tightened them down as tight as I could, rode a hundred yards, and retightened. That’s it, so hopefully the damage hasn’t been done 
. I’ll definitely stay away from tightening them any more…
I’ll be sure to use better discretion next time…
Heh…it has gone a little crazy. Are you going to use better discretion on how you tighten things or what you dare ask about? 
I’m sure you’re fine, regardless.