Spld cyclist

I have this triple Sugino square taper crankset on a bike. I was recently trying to figure out the source of a creak when I checked to see if the bolts were tight. They felt surprisingly loose, so I snugged them up a little bit. Now I'm wondering about the next step. I would like to torque them correctly, but I've heard that you shouldn't do this repeatedly (i.e. tighten them, ride, then tighten them some more). Should I take them off completely and start over? What torque should I use for these?



This crankset originally came on a 2005 Bianchi Volpe. The only markings are "Sugino" on the front and "C-10" on the back.

Andrew R Stewart 

The usual torque range for retaining arm bolts is 25-30 foot pounds.

But I'll take issue with your comment that one shouldn't retighten these bolts. "(i.e. tighten them, ride, then tighten them some more)." This is done all the time. After the initial build up test ride, after the 30-90 day new bike service and during virtually every tune up That I (and my coworkers) have done. I will further say that failure to retighten crank arms is why so many round out and need replacing. Andy.

sreten

Hi,

Many argue abut this, and contradict each other.

My take on the subject :

The right crank needs to be tight, as tight as you
can go with a normal ratchet using your hands.

The left crank needs to be tighter, standing
on the crank and ratchet, bouncing tight.

rgds, sreten.

cny-bikeman

Yes, there is some disagreement about retightening, some saying that the best route is to tighten properly to the spec'd torque, and that very little is needed after that. Others say that one will inevitably need to retighten with at least some cranks, depending especially on the rider's weight, habits, etc. But no professional mechanic, who has seen hundreds, even thousands of bikes and generally has had to retighten relatively few of those, would recommend that kind of procedure. It's certainly irresponsible to advise such in a public forum, as opposed to choosing to do so on one's own equipment. If such extreme torque was necessary or advisable the manufacturer would specify such.

p.s. I am not saying the advocate is irresponsible, just the particular advice.

ThermionicScott 

I'm glad I do the work on my bikes... torque wrenches and specs are much better than "bounce on the cheater bar until you get tired."

Also (speaking generally here), it's important to keep in mind why a crank bolt would lose torque -- it's because the crank is moving up the taper (away from the bolt) and actually forming a tighter fit. So the only reason to re-tighten the bolt is to make sure it doesn't come loose completely and fall off. You don't need a lot of effort at that point.

bradtx

Spld cyclist, With square tape the key is to not over tighten. If the bolts are tight, they don't need to be tighter.

Brad

zukahn1 

+1 Checking that these bolts are tight should part of basic servicing, riding with them loose is can round them out and cause drive line problems.

Spld cyclist

I'll have to tighten them with the torque wrench and then see what happens. I wonder if they were loose like that when I brought the bike home from the LBS, or if they loosened up through use afterward.

I have little confidence in the mechanic at that LBS due to other issues I have had with the bike, so I wouldn't be surprised if they weren't properly tightened in the first place. Hopefully the cranks aren't ruined at this point.

davidad

It may be done all of the time, but it is not a good idea. The tapers should be greased and the bolts properly torqued on installation.
https://www.sheldonbrown.com/brandt/i...ng-cranks.html

Andrew R Stewart 

I will respectively dissagree. At most the axle flats should have only "skin oil" on them. Too much lube allows the arm to travel up the taper too far before the bolt's torque level is reached. This is a commonly known issue.

Also, my 40 years of shop work has seen many hundreds of crank arms that have "rounded out" because they came loose. This year alone we have probably replaced 3 dozen, and the shop I currentlly am at is not the service focused style that I have spent most of my professional life in. I have followed the same procedure (that i discribed before, proper initial torquing of the retaining bolt and a few checks/retightening in the initial weeks following) with my personal and the client bikes for all my years. The number of crank arms that have been problematic using this procedure, that I can truely track with service records, have been virtually nil. The ones that I have had to replace due to "rounding out" have been orders of magnitude more. What this says to me is that when well torqued during the assembly and checked/retorqued again after some riding the tapered cranks are very reliable. But when torqued only once (and with bikes built/sold by others the amount is a variable) and then never redone the likehood of problems is MUCH HIGHER.

Perhaps some of the misunderstanding of the retightening step is in what/how much this means. In an ideal world the bolt would be loosened then retightened using a torque wrench. In the real world of shop service this means that the bolt is just checked for tightness using the experience of the mechanic's feel as the torque judging. After years and thousands of procedures I have a good feel of what is the reasonable amount of torque. My history has proved this, and doing this over and over has tought me this level. Can i tighten a crank bolt and say it's at X.Y pounds of torque, no. Can I say the bolt is well tightened and within working industry range, yes.

With my personal bikes this retightening produces minimual amount of end of wrench movement, perhaps 1/4"-1/2" for a Park CCW. Over the year (I tend to dissasemble my bikes once a year + or-) my checks and retightening amounts to 1" (or slightly more) of wrench end travel. You do the math as to the torque increase. I have cranks I have done this cycle for over a decade so I am conifident that it works.

I will agree that when a ham fisted "mechanic" goes at it all bets are off. But i teach my coworkers my method and there are dozens of wrenches in shops that learned my methods well and those I keep in touch with don't "correct" me. After so many years of doing the same methods I would think there would be a trail of VERY unhappy shop owners (these are the people that are at the spot that the buck stops, the end of the system we call the bike shop world). Many of my employees and coworkers have stayed in the business for decades.

I have had this discussion before. I agree that whatever method works for you is good. But I will advise my customers and coworkers to my methods untill i see first hand the wrongs of them. Andy.