Stop crank bolts loosening

Can you post a picture so we can assess the state of the damage.

I tightened the drive side up using my wratchet and socket with alan key thing (sorry non technical terms).

This gave me much more leverage than my normal alan key, unfortunately my chainring ended up against the frame (the chainstays).

If not i suppose i will need a new BB with a different spindle length?

This clearly shows you were tightening it no where near enough in the first place. You will indeed have to move over chainring or get different BB. Make sure you pay attention to chainline when doing so.

I personally tighten up cranks with all my might.

This clearly shows you were tightening it no where near enough in the first place. You will indeed have to move over chainring or get different BB. Make sure you pay attention to chainline when doing so.

I personally tighten up cranks with all my might.

dont worry, he looks nothing like his avatar in real life

http://www.google.co.uk/products?rlz=1C1GGLS_enGB329GB329&sourceid=chrome&q=torque+wrench&um=1&ie=UTF-8&ei=33exSrqfKtGj4gam052tCg&sa=X&oi=product_result_group&ct=image&resnum=1

ftw

any in particular?

Yeah, the ones that suit your torque range. I have two.. one for small stuff 2-10Nm and one for cranks, etc which is maybe 20-70Nm. Having said that I must've been doing pretty well since I never had trouble with my cranks coming loose or any of the shit that effects most people posting in the mech area..

Torque Arms

This clearly shows you were tightening it no where near enough in the first place. You will indeed have to move over chainring or get different BB. Make sure you pay attention to chainline when doing so.

I personally tighten up cranks with all my might.

agreed, thanks for all the info guys, will take the bike off the road for a while for a bit of a rebuild.

i didnt realise that they don't just tighten to their original position when you 'push' them on to the BB spindle. Anyway living and learning.

thanks again

skinnygav

Yeah, the ones that suit your torque range. I have two.. one for small stuff 2-10Nm and one for cranks, etc which is maybe 20-70Nm. Having said that I must've been doing pretty well since I never had trouble with my cranks coming loose or any of the shit that effects most people posting in the mech area..

Torque Arms

i got one for cranks today - i retract my previous statement - there is no way you can get to required torque without a massive lever - thought i was going to strip the threads!

This is why square taper cranks should be banned, and primo powerbites should be mandatory for noobs.

An update

I removed my cranks and noticed a kind of salt build up on the taper of the cranks, not sure if water had got in or if it is an aluminium oxide from pressure contact with the Ti BB spindle.

Have scraped out (gently trying not to scratch the crank taper) the white residue.

Am thinking due to the metals copper slip really ought to be used on the splines, however I have bloody lost my pot of it.

Tightened the fuck out of it as I did the cranks back up. Cranks are much much quieter now and the crank bolt stayed tight on my way to work.

Will probably try to borrow a torque wrench, buy some more copper slip and redo the whole job in a few weeks time.

finally went for this torque wrench

http://www.toolstop.co.uk/norbar-11037-torque-wrench-1/4-ratchet-adjustable-1-20-n.m/10-180-lbf.in-model-sl0-steel-knob-p5334

it will do all the bolts including the 16 Nm for the sugino crank bolts

did loads of reading up, the norbar are also branded as wurth or syntace and seem to be well respected

if buying one be careful they do steel and plastic capped ones, the capped does 4-20 Nm the stell does 1-20 Nm

will now have to find the torque specs for each bolt on my bike

will see what difference copper slip and the correct tension on the crank bolts will do.

happy geek days

I know it can be a stupid question, but are you sure your BB suits your cranks (ie. ISO v. JIS)?

yep, that is not the problem

its that the bb is titanium and it has been interacting with the aluminium of the cranks

hence the dry compacted powder residue on the tapers

I tightened the drive side up using my wratchet and socket with alan key thing (sorry non technical terms).

This gave me much more leverage than my normal alan key, unfortunately my chainring ended up against the frame (the chainstays).

current plan of action is to try the chainring on the outside of the cranks as opposed to the inside but i'm not sure if the extra tightening will give me a straight chainline.

If not i suppose i will need a new BB with a different spindle length?

Sounds like its FUCKED. When the chain ing is fouling the chin stays you've generally had it. The only chance that you might have had would have been if you had an adjustable threads on your BB but it doesn't sound like it.

http://www.google.co.uk/products?rlz=1C1GGLS_enGB329GB329&sourceid=chrome&q=torque+wrench&um=1&ie=UTF-8&ei=33exSrqfKtGj4gam052tCg&sa=X&oi=product_result_group&ct=image&resnum=1

ftw

^^All/mainly gash. You should spend decent money as the cheaper options will be inaccurate. A good one will have precision certificates in the packaging. As I've mentioned before I've got a really good roebuck with a torque meter on it if anyone needs one.

An update

I removed my cranks and noticed a kind of salt build up on the taper of the cranks, not sure if water had got in or if it is an aluminium oxide from pressure contact with the Ti BB spindle.

Have scraped out (gently trying not to scratch the crank taper) the white residue.

Am thinking due to the metals copper slip really ought to be used on the splines, however I have bloody lost my pot of it.

Tightened the fuck out of it as I did the cranks back up. Cranks are much much quieter now and the crank bolt stayed tight on my way to work.

Will probably try to borrow a torque wrench, buy some more copper slip and redo the whole job in a few weeks time.

This is the issue with Ti BB spindles that black stuff is Al oxide that make that fucking annoying creaking. As long as you use paper between 800-1200 you'll be fine. Just be careful if you are using something with a flat edge to remove the crap. Also when you've done this get an old rag soaked with methylated spirit and force the rag through the taper on the crank as well as the spindle you're good to go.

finally went for this torque wrench

http://www.toolstop.co.uk/norbar-11037-torque-wrench-1/4-ratchet-adjustable-1-20-n.m/10-180-lbf.in-model-sl0-steel-knob-p5334

it will do all the bolts including the 16 Nm for the sugino crank bolts

did loads of reading up, the norbar are also branded as wurth or syntace and seem to be well respected

if buying one be careful they do steel and plastic capped ones, the capped does 4-20 Nm the stell does 1-20 Nm

will now have to find the torque specs for each bolt on my bike

will see what difference copper slip and the correct tension on the crank bolts will do.

happy geek days

looks good.

is there any way i can stop my crank bolts from loosening?

Thanks

Skinnygav

Grease and a torque wrench.

Grease will allow you to tighten the bolts more than a dry interface will allow - and a torque wrench will allow you to correctly set the torque.

The best way to get a good fit is this:

1. Put the cranks on
   
2. tighten to the stated torque
   
3. take an easy ride for about 100 yards
   
4. then re-tighten to the stated torque
   
5. repeat parts 3 & 4 but increasing the intensity of each subsequent ride until the bolt/crank on longer moves up the taper.
   
   
   

NEVER DO THIS !

NEVER !

Ask a metallurgist about metal 'bruising' - this method is a really bad idea and an often repeated crank mounting myth (for want of a better phrase).

^^Tell it to Cliff Poulton@ Royce

@ Tynan:
classic debate as to whether to grease taper or not. I don't as it could aid the crank riding higher up the taper than is correct.

finally went for this torque wrench

http://www.toolstop.co.uk/norbar-11037-torque-wrench-1/4-ratchet-adjustable-1-20-n.m/10-180-lbf.in-model-sl0-steel-knob-p5334

20Nm is very very low for a crank mounting bolt !

I use my 1-20 Nm for all the smaller bolts (stem, headset, seatpost binder, saddle . . . and so on) and use a 20-110Nm for heavier stuff - set at 40Nm for Sugino 75 crank bolts.

Even something as small and light as an alloy (not even steel) chainring bolts take 8Nm - that's why I say a 1-20Nm wrench is too low for mounting cranks.

and so can repeatedly tightening cranks like you suggest.

lil grease and torque wrench and your golden.

grease or no, repeated tightening leads to fucked up tapers and cranks and then you might cry if they are half decent.

But if the correct torque is used the cranks should not move up the splines.

Talking to jimbilly he reckoned that is sigino say to grease that they should be greased.

Other makes say no grease. So probably best to see installation guide fo different cranks.

Mine's rated as 27Nm

^^Tell it to Cliff Poulton@ Royce

@ Tynan:
classic debate as to whether to grease taper or not. I don't as it could aid the crank riding higher up the taper than is correct.

:)

I have spoken to Royce on this very subject (Tune BB >> Storck Powerarms) - They agreed with me ! (This was at least three years ago and I counldn't tell you with any accuracy whether I spoke to Cliff or not) - Mount the arms an DO NOT RIDE THEM FOR AT LEAST AN HOUR !!

On the subject of greasing the tapers listen to the wise words of Brandt:

My cranks get loose, quite quickly too; over about 10 miles or so from being solid to flopping about in the breeze. Any suggestions?
One or both of the cranks are ruined! Once ridden in the "floppy" mode, the tapered square bore of the crank has been deformed and can no longer be secured on a spindle. Install and properly tighten new cranks on the spindle after greasing the tapered square ends of the spindle. Proper tightness should be achieved with a torque wrench or by a skilled hand.
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.

Failure from "over-tightening" is caused by repeated re-tightening of properly installed cranks. In use, an aluminum crank squirms on its taper and, because the retaining bolt prevents it from moving off the taper, it elbows itself away from the bolt and up the taper ever so slightly. The resulting loss of preload, after hard riding, can be detected by how easily the bolt can be turned.

Loss of crank bolt preload is greater on left than the right cranks, because left cranks transmit torque and bending simultaneously while right cranks transmit these forces separately. The left crank transmits driving torque through the spindle to the right crank and chainwheel while the right crank drives the chainwheel directly. Besides that, the right crank transmits torque to the spindle only when standing on both pedals. Doing this with the right foot forward (goofy footed) is the only time the spindle transmits reverse torque.

Mechanics, unaware of why crank bolts lose preload (and commensurate crank tightening), have re-tightened bolts until cranks split. No warnings against re-tightening properly installed cranks are evident although it is here where the warning should be directed rather than at lubrication.

Because friction plays no role in torque transmission, preload in the press fit must be great enough to prevent elastic separation between the crank and spindle under torque and bending. This means that no gap should open between crank and spindle facets under forceful pedaling. Crank bore failure occurs when the press fit is loose enough that a gap opens between spindle and crank. Torque is transmitted by both leading and trailing half of each facet, contact pressure increasing and decreasing respectively. In the event of lift-off, the entire force bears only on the leading edge of facets and causes plastic deformation, causing the bore takes on a "pin cushion" shape (loose crank syndrome). Subsequent tightening of the retaining screw cannot correct this because neither the retaining bolt nor crank are strong enough to re-establish the square bore.

The claim that a greased spindle will enlarge the bore of a crank and ultimately reduce chainwheel clearance is also specious, because the crank cannot operate in a plastic stress level that would soon split the crank in use. However, increased engagement depth (hole enlargement) may occur without lubricant, because installation friction could ream the hole.

With or without lubricant, in use, cranks will make metal-to-metal contact with the spindle, causing fretting erosion of the steel spindle for all but the lightest riders. Lubricating the spindle for assembly assures a predictable press fit for a given torque. Without lubrication the press is unknown and galling (aluminum transfer to the steel spindle) may occur during assembly. After substantial use, spindle facets may show rouge and erosion from aluminum oxide from the crank, showing that lubricant was displaced.

Crank "dust caps" have the additional duty to retain loose crank bolts. Because crank bolts lose preload in use, they can become loose enough to subsequently unscrew and fall out if there is no cap. If this occurs, loss of the screw will not be noticed until the crank comes off, after the screw is gone.

But if the correct torque is used the cranks should not move up the splines.

Talking to jimbilly he reckoned that is sigino say to grease that they should be greased.

Other makes say no grease. So probably best to see installation guide fo different cranks.

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

But if the correct torque is used the cranks should not move up the splines.

Talking to jimbilly he reckoned that is sigino say to grease that they should be greased.

Other makes say no grease. So probably best to see installation guide fo different cranks.

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.

lil grease and torque wrench and your golden.

• several million.
  
  

It really it as simple as this, grease + the correct torque = years of solidly mounted cranks.