Stop crank bolts loosening

I found this from Sugino

*
it was on here http://www.bikeforums.net/archive/index.php/t-396322.html *

i was surprised that they suggest such a low force

• Dear Mr. --
  
  

Thank you very much for your e-mail.
*
*
The torque is 12-16N.m.
However, this torque specification is appropriate
under the condition that the SG75 cranks are used with the NJS parts.

We recommend to grease the BB spindle slightly
to prevent seizing and rust on the spindle.

We also recommend to do maintenance periodically.

Best regads,
Yuki Iwai
SUGINO CYCLE INDUSTRIES
, LTD.*
iwai@suginoltd.co.jp
TEL. +81-(0)742-62-5311
FAX.+81-(0)742-62-5320
287-1 Tohkujo-cho, Nara, Japan 630-8144

actually he did say that you can use a tiny bit of grease.

Maaa baaad

mine (miche) said no grease, i dont think you can go wrong following the manufacturers instructions.

Read my post above (the big one).

"The admonition not to grease the spindle finds life mainly in the bicycle trade. When I discussed the "dry assembly" rule with crank manufacturers, I discovered that they had warranty claims from customers who split cranks. However, cranks cannot be split by overtightening them. This can be proven by attemting to do so. An M8x1 bolt is not strong enough to split a major brand crank."

remember that for the most part you're using tapers/cranks from different manufacturers and are hoping that their interpretation of either ISO or JIS is accurate. This is why you tighten to the recommended setting ride a little then retighten and repeat this until there's no more movement- hence no grease.

so - tighten to say 30Nm, cycle a bit - tighten more than 30Nm? 30Nm is pretty fucking tight - any more you will strip threads or crack cranks or fuck the spindle.

sorry but you're talking shit.

Read my post above (the big one).

"The admonition not to grease the spindle finds life mainly in the bicycle trade. When I discussed the "dry assembly" rule with crank manufacturers, I discovered that they had warranty claims from customers who split cranks. However, cranks cannot be split by overtightening them. This can be proven by attemting to do so. An M8x1 bolt is not strong enough to split a major brand crank."

yeah no i've read that on sheldon - but still, doing what the makers recommend and you aren't going to go wrong.

i may grease them when i take apart or may not.

so how far off njs spec would a phil wood Ti BB actually be and what tension would people suggest in the face of Sugino's own suggestion?

i was surprised that they suggest such a low force

• Dear Mr. --
  
  

Thank you very much for your e-mail.
*
[I]
The torque is 12-16N.m . . . .

Wow ! That is crazy low !!

I have seatpost bolts that are (manufacturer recommended) rated at 28Nm !!

I have stems (the bar end) that are rated at 12Nm . . . . when in use with carbon bars !!

I could go on.

yep, hence why i thought the 1-20Nm wrench would be sufficient

is it because for njs spec the bike is going to be taken apart for each race?

so - tighten to say 30Nm, cycle a bit - tighten more than 30Nm? 30Nm is pretty fucking tight - any more you will strip threads or crack cranks or fuck the spindle.

I torque my Suginos to 40Nm - and most other (Square tapered) cranks onto BBs at 45Nm - never stripped a bolt.

One thing I do though - is when using Ti-cranks bolts (like Tune's stretch T-bolts) - is that I torque to 45Nm using a steel bolt then remove the bolt once the cranks are locked onto the taper and then put on the Ti bolt (or alloy if you are feeling a bit risky).

i don't think that would be the case - i would have thought tighter would be better as loose on a track they would fuck spline. i personally think go with what sugino said.

park website says that seatpost bolts should only be done enough to stop seat slipping down which is way off 28

so - tighten to say 30Nm, cycle a bit - tighten more than 30Nm? 30Nm is pretty fucking tight - any more you will strip threads or crack cranks or fuck the spindle.

sorry but you're talking shit.

who said anything about tightening above the manufacturer's stated value, nonce?!?
YOU TIGHTEN TO WHAT THEY SAY. RIDE A LITTLE. THEN RETIGHTEN TO THE SAME VALUE. REPEAT UNTIL THERE IS NO MORE MOVEMENT.

yeah no i've read that on sheldon - but still, doing what the makers recommend and you aren't going to go wrong.

Not necessarily so.

On square taper to crank interfaces some manufacturers say grease, some say no grease.

Application of the law of the excluded middle suggests they are not both right, following one recommendation means you can 'go wrong' - which one is correct is up for debate, but the idea that doing what the makers recommend will necessarily give you the right result is not right.

have found more discussion on

http://www.fixedgearfever.com/modules.php?name=Forums&file=viewtopic&printertopic=1&t=4639&start=15&postdays=0&postorder=asc&vote=viewresult&popup=1

*
Dear Shady

We have never tested the SG 75 with the Phil Wood BB.
So, we cannot make a comment on this.

However, the torque is specified by NJS
in order to install it securely and to make a proper chainline.

As we told you, we recommend to do maintenance periodically and retighten it often.

Yuki Iwai
SUGINO CYCLE INDUSTRIES, LTD.
iwai@suginoltd.co.jp
TEL. +81-(0)742-62-5311
FAX.+81-(0)742-62-5320
287-1 Tohkujo-cho, Nara, Japan 630-8144

    ----- Original Message ----- 
    From: Shady F. Hakim 
    To: Yuki Iwai 
    Cc: <suginoltd@pop16.odn.ne.jp> 
    Sent: Thursday, March 13, 2008 9:33 PM 
    Subject: Re: Fw: FW:Crank Bolt Torque for Sugino 75 

    Dear Yuki, 

Thank you very much for your reply. I am surprised because this sounds like a VERY LOW torque number. Most of the estimates for other manufacturers are 32+ N.m. Why is this so low?

I was using this with SG75 NJS bottom bracket, but am switching to Phil Wood ISO taper BB. Also, this is for street use, not track. Does this make a difference in torque specifications?

    Could you please doublecheck the torque number under these conditions? Again, thank you very much for your reply. *

is it because for njs spec the bike is going to be taken apart for each race?

That might be a good point, perhaps that is even for a single race - not sure why they wouldn't go all the way ??

who said anything about tightening above the manufacturer's stated value, nonce?!?
YOU TIGHTEN TO WHAT THEY SAY. RIDE A LITTLE. THEN RETIGHTEN TO THE SAME VALUE. REPEAT UNTIL THERE IS NO MORE MOVEMENT.

Please don't do this !

You are deforming the leading edges of the taper.

after i made my post about stripping bikes for njs i found similar stuff on the fixedgearfever thread as well

so am still none the wiser

just more confused and pissed of i have just ordered a torque wrench that may not be sufficient

I had a brand new 75 on a Royce BB greased it, then slightly over torqued the bolts and the crank moved too far up the spinle rendering BB useless.

Please don't do this !

You are deforming the leading edges of the taper.

If you've tighten to the numbers quoted by the manufacturer how can this deform the taper?

I torque my Suginos to 40Nm - and most other (Square tapered) cranks onto BBs at 45Nm - never stripped a bolt.

One thing I do though - is when using Ti-cranks bolts (like Tune's stretch T-bolts) - is that I torque to 45Nm using a steel bolt then remove the bolt once the cranks are locked onto the taper and then put on the Ti bolt (or alloy if you are feeling a bit risky).

ok, when i was doing it to recommended value it felt like it was about to go "pop!"

I torque my Suginos to 40Nm - and most other (Square tapered) cranks onto BBs at 45Nm - never stripped a bolt.

One thing I do though - is when using Ti-cranks bolts (like Tune's stretch T-bolts) - is that I torque to 45Nm using a steel bolt then remove the bolt once the cranks are locked onto the taper and then put on the Ti bolt (or alloy if you are feeling a bit risky).

+1

Aluminium bolts are usually given a much lower torque rating for the same crank/BB set up than for steel or Ti bolts.

Something to bear in mind

after i made my post about stripping bikes for njs i found similar stuff on the fixedgearfever thread as well

so am still none the wiser

just more confused and pissed of i have just ordered a torque wrench that may not be sufficient

I can guarantee 20Nm will not be enough to mount a pair of cranks securely onto a square taper BB.

But don't be pissed off, 1-20Nm is actually really handy (much more so than 20-110Nm).

It divides up like this.

20-110Nm >> Cranks bolts and pedals (crank mount end).

1-20Nm >> Everything else on your bike.

I had a brand new 75 on a Royce BB greased it, then slightly over torqued the bolts and the crank moved too far up the spinle rendering BB useless.

!

Please read my post above (please!) - the big one with lots of words.

If you've tighten to the numbers quoted by the manufacturer how can this deform the taper?

It is the riding of freshly mounted cranks that deforms to taper (or bore) not the tightening.

Metal 'bruises' under high torque.

Under stress it softens - you need to leave it at least an hour after setting a high torque for this 'bruising' to settle and the metal structure to realign/harden.

Riding during this period of bruising will mean you deform the leading edge of the taper (or deform the bore depending on which is the stronger) - which will make the cranks slightly (fractionally) loose - people then go home and tighten again - 'bruising' the metal again - then off for another ride . . . and so on.

Please, please, please just try this:

Grease the spindle . . . mount the cranks to the correct torque . . . leave it for an hour or so . . . ride around for as long as you wish, then take a look at the cranks . . . . they will not be loose !

Try it, you lose nothing, you can still go about the whole tighten / ride on 'bruised' metal / enlarge the bore / retighten / ride on 'bruised' metal / enlarge the bore . . . thing after this test.