Kerry and Motohaus, a very bad situation made good.

[Ixion]

Well, last weekend I fitted my heads and barrels. Torqued the head bolts down as per manual, 20lb ft, sequential, with the torque wrench . Went round again , retorqued, repeat until every bolt is 20 lb ft.

Started bike today, rode it round the block until it reached operating temperature. Cool down, checked the bolts. Same torque wrench. Gee, they're loose as . Retorqued them.

Guess I only thought I tightened them the first time, I better sack myself.

Maybe though I'll repeat the ride , cool, check cycle until they're stable. Kind of hard to do though when it's not your own bike.

[Big Dave]

No problem, I don't really turn spanners anymore, and your type is not welcome in any shop I run. I bet you drive a euro car.....Mr Perfect.

Heeeyyy! I just got a new Euro car.

[TLDV8]

I have purchased tyres off Kerry in the past (great service)


This is just thinking out loud.
One thing i always do when working on the brakes of other peoples motorcycles is to add a drop of blue loctite to the fasteners.
The reason i do that is simple (to me) I do not know the history of the bike,therefore i do not know who has worked on it previously and have witnessed on quite a few occasions folk doing up fasteners (way to tight) without using a torque wench.
If everything is fine the loctite is simple insurance.

Most bikes use bolts in the 8mm/10mm range to fix the calipers (10mm only go to around 16.5 ft/lbs)
What can happen when folk crank bolts up to tight (the threaded lug on calipers is quite often only 12mm and in alloy) is the threads are stretched,this can then mean even with the correct torque (without a locking agent) the fastener will not remain captive and back out.
Calipers are not spigoted so once there is a lack of friction at the mounts (low bolt tension) the caliper can then move with the bolt hole clearance.

Sure, mistakes can be made (and remedied as in this case ) but things are not always that simple or clear with things of a mechanical nature.

[Patch]

but things are not always that simple or clear with things of a mechanical nature.

exactly


For those that think bolts, rivets etc don't work loose over time - go back to doing what you are paid to do, shut your mouth and learn from those that know what the fuck they are talking about.

[Ixion]

But they are bolting into cast alloy, usually.

[CookMySock]

But they are bolting into cast alloy, usually.

The bole is supposed to be torque-turned into its elastic region.

http://www.hexagon.de/tasignat.htm

DB

[CookMySock]

but things are not always that simple or clear with things of a mechanical nature.

Sure they are, but tyre-fitters don't have a mechanical engineering degree.

DB

[DEATH_INC.]

The bole is supposed to be torque-turned into its elastic region.

http://www.hexagon.de/tasignat.htm

DB

What has this to do with it being wound into cast alloy? It's not the bolt elasticity that is affected by what it's bolted into.....

[Ixion]

A caliper bolt on a bike usually has to be much stronger than a pure clamping load would indicate, because of the heavy sideways forces it must resist as the disk tries to drap the caliper along with it.

F'instance , a quick check of the manual for the arszhole(just coz it's handy) shows a manufacturers torque of only 25 lbft for the caliper bolts. Much less than the bolt could take. But if you tightened the bolt down to its elastic limit, before you got there you'd have stripped the alloy threads on the fork leg.

The practical reality is, as anyone who has worked on bikes for a bit, especially old bikes, sometimes a bolt which is properly done up WILL slacken off in service. Vibration , expansion and contraction, all sorts of funny effects.