Torque on caliper bolts?

[tdskip]

I may just be search challenged today, but I cannot seem to find the torque spec for the bolts that hold the calipers together (not to the car, but side to side after splitting them).

I know Porsche spec calipers use 70, but wanted to check before assuming that was close to correct.

Thanks!

[lotusfan]

tdskip

You are unlikely to find a value because splitting of calipers is not recommended, but, in the WSM I think there are generic torque values for various bolt sizes and if all else fails - 2 or 3 white knuckles should be enough!!

[bitsobrits]

The diameter and grade of the bolt needs to be considered, so comparing one make of car to another is not suitable unless they are using the same size fastener. When I rebuild calipers, if I can't find factory specs, I look up the diameter in one of the many online charts and assume a grade 8 (or 10.9 metric) to get the torque value.

You are using the factory caliper bolt or a known high tensile strength aftermarket (like ARP), yes?

And it's time for my periodic reccomendation: anyone doing their own work really should read Carrol Smith's "Nuts, Bolts, Fasterners, and Plumbing" handbook. Essential for safe, secure practice.

[tdskip]

tdskip

You are unlikely to find a value because splitting of calipers is not recommended, but, in the WSM I think there are generic torque values for various bolt sizes and if all else fails - 2 or 3 white knuckles should be enough!!

My brakes sat with fluid in them since 1993 so I really didn't have a choice when it came to getting the pistons out.

I'll be using the factory bolts, will snug them up tight.

[tdskip]

The diameter and grade of the bolt needs to be considered, so comparing one make of car to another is not suitable unless they are using the same size fastener. When I rebuild calipers, if I can't find factory specs, I look up the diameter in one of the many online charts and assume a grade 8 (or 10.9 metric) to get the torque value.

You are using the factory caliper bolt or a known high tensile strength aftermarket (like ARP), yes?

And it's time for my periodic reccomendation: anyone doing their own work really should read Carrol Smith's "Nuts, Bolts, Fasterners, and Plumbing" handbook. Essential for safe, secure practice.

Good point, and will track that down.

[Bombay Racing Green]

It’s in this video, towards the end.

https://youtu.be/UUJuW6Ho2LY

All the best.

[englishmaninwales]

Apart from detail for torque setting and replacement of the cross feed seal, are there any other reasons for not splitting a caliper when refurbishing?
Malcolm

[pharriso]

It’s in this video, towards the end.

https://youtu.be/UUJuW6Ho2LY

All the best.

"17 FtLbs, hopefully that will be enough"

Very confidence inspiring

[tdskip]

Apart from detail for torque setting and replacement of the cross feed seal, are there any other reasons for not splitting a caliper when refurbishing?
Malcolm

Good morning Malcolm - I was taught that this was a major no-no but now having done it I honestly don't see what the big deal is. Maybe I'll have issues but this is close to stone age tech - basically two slabs of metal with a passageway in them. Unless you bugger up the faces or misplace the seal I'm not sure what can do that wrong simply by splitting them.

I could be all wrong, hopefully more experienced people will share their knowledge.

[derek uk]

Like you TD I've always been told not to do it. Reference back then was that makers bolted them together with stretch bolts selected to do the job once. Finding similar bolts impossible or difficult. Using standard bolts would be at your own risk. Calliper makers didn't quote torque for that reason. What the companies that refurb them use not known. Maybe they would be willing to fess up, but doubtful.

[tdskip]

Got this back from a VERY Lotus knowledgeable source;

“ OK to reuse bolts. TQ--5/16 bolt 15-18Ft/lbs---3/8 bolt 25-28 ft/lbs”

[h20hamelan]

And like any bolts, stretch is of concern.
15 for first torque, 15.1 next...
When one re-torques, 15.2. Thus, the limit is 18(?) on said 5/16

[tdskip]

Thank you for the follow up consideration.

Look at these resembled later today and pass along anything else that comes up or I find.

On a sidenote – it is encouraging to be just about out of things that I need to refresh on the car, hopefully next week will see the drivetrain fitted.