what's the torque on Campag 11s chairing bolts?

on-yer-bike

Anybody know?

ugo.santalucia

very little, I believe these are alloy ones, they won't take a lot

cycleclinic

Till they are tight enough that they won't unscrew. Given they are Torx bolts and silly money better to have them done a bit too loose and have to tighten rather than mess up the bolts and drill out and replace.

neeb

8 Nm officially. The newer one-piece ones are easy to torque up precisely. With the older two-piece ones I used to think that you had to hold the rear of the bolt with a screwdriver while torquing up the front part (which is fiddly), but in fact once they are tightened a little bit the rear part usually holds and you can tighten them up with just a torque wrench from the front.

gfk_velo

Dry torque is 8nm.

Contrary to the note from thecycleclinic above, the torque does matter insofar as loss of a chainring bolt on the carbon chainsets *can* lead to not only failure of the chainring but also that of the spider - it's rare, we've seen it only twice in 5 years as Campagnolo's main Service Centre in the UK ... but if it does happen, it's expensive and not covered by the warranty if the user has replaced their own chairings or bolts.

Not that it's a dry torque, lubricating the threads with a grease or copperslip material is not recommended.

All such technical information is in the Campagnolo technical manuals, available on the Campagnolo website at http://www.campagnolo.com/jsp/en/docstec/doccatid_8.jsp

HTH
Graeme
Velotech Cycling Ltd
Campagnolo Main UK Service Centre
www.velotech-cycling.ltd.uk

ugo.santalucia

gfk_velo wrote:

Not that it's a dry torque, lubricating the threads with a grease or copperslip material is not recommended.

HTH
Graeme
Velotech Cycling Ltd
Campagnolo Main UK Service Centre
http://www.velotech-cycling.ltd.uk

But that's a recipe for disaster with alloy bolts, no? Don't they get seized?

Velonutter

I always fit the Chainring bolts dry and have never had an issue with them coming undone or coming loose.

on-yer-bike

I have now replaced the outer chainring with a Miche ring as its on my winter bike and it was £30.00 cheaper. There were no packing shims under the old rings and it seemed pretty straightforward. I cant understand why this would be a Service Centre only job? The chainset is out of warranty anyway so that wasn't a concern. I did grease the bolt that goes into the crank so maybe Ill take it out and degrease it. The ring runs true and works, although I had chain suck once which may have been due to going through a flood and not using thick enough lube. If it happens again I'll wish I'd bought Campag ring.

gfk_velo

on-yer-bike wrote:

I have now replaced the outer chainring with a Miche ring as its on my winter bike and it was £30.00 cheaper. There were no packing shims under the old rings and it seemed pretty straightforward. I cant understand why this would be a Service Centre only job? The chainset is out of warranty anyway so that wasn't a concern. I did grease the bolt that goes into the crank so maybe Ill take it out and degrease it. The ring runs true and works, although I had chain suck once which may have been due to going through a flood and not using thick enough lube. If it happens again I'll wish I'd bought Campag ring.

As I mentioned in my post, it's recommended as a SC only job as the shims are not *always* present & when they are, they will be of a thickness & in a position unique to that spider - the composite spiders are individually checked and shimmed. It's a bit late to wonder where each shim goes when you have both the rings off & a heap of shims on the bench & you won't necessarily even know if you have "all" the shims ...

velonutter wrote:

I always fit the Chainring bolts dry and have never had an issue with them coming undone or coming loose.

Yep, this is the correct practice although I should have said (apologies to on-yer-bike) that the bolt into the back of the crank is generally Loctited with 247. Campagnolo do not recommend grease or Loctite on the main chainring bolts and if you release one of them, you will find it dry. Occasionally a smidge of Loctite 243 can be used if the bolt has been repeatedly released and re-tightened.

A general point & maybe worth saying something about here as I have mentioned "dry" and therefore by association, the idea of "wet" torque settings ...

The general issue of torque is widely misunderstood - it is only an analogue for what is actually going on in a thread, which is elongation. A bolt only stays tight because the threads are in effect "stretched" against one another, producing a compressive force at the head. We measure how great the elongation is, and therefore how much friction is generated along the length of the thread (that what keeps it "done up") and the compression at the head (useful in the context of, say, a handlebar stem faceplate bolt) as a function of how much turning force we apply at the head. An alloy bolt stretches more than, say, a mild steel bolt, so the torques required to produce a known elongation and force at the head vary, and will vary again depending on whether a steel female or an alloy female is concerned.

Lubrication, be it from oil, grease, a more-or-less fluid locking compound will change how easy it is to turn the bolt in the thread and so influence how the torque applied translates into elongation / compression at the head. As a (very) broad rule of thumb, if elongation / compression "x" is required and attained by a specific torque on a dry assembly, 25% less torque would give the same result on a "wet" assembly. There are other factors though - fit of the thread, cleanliness of the thread and whether the bolt is bottoming out, for instance, all influence whether the desired result is obtained.

Most cycle manufacturers do not specify "wet" or "dry" torque. The user or mechanic is generally left to work it out for themselves - in the automotive trade, torques are usually specified as "dry" or "wet" as meets the case - in our industry it is often only by the recommendation for (say) grease or Loctite that we can determine what measure is being applied (and even then, we have seen some horrendous errors ...)

As ever, HTH.

BTW, velonutter, thanks for the PM, unfortunately something odd is going on with either my UCP or my local machine, so I can't access you latest - please feel free to email me at velotechcycling "at" aim "dot" com.

on-yer-bike

Thanks Graeme. I was very careful when dismantling and looked out for any shims. I also put the bolts back in the same holes. What is the plastic thing inside the torx hole of the bolt that screws into the crank?