10 replies to this topic

[Willpill20]

Hi I have a set of metro 4 pot calipers and I need new bolts that bolt the half’s together as I don’t have them .
I am sure that they are 7/16 unf but I don’t know the length but I do know that they have got to use grade 8 bolts . Just need to know the length .
Please someone help me
Thanks

[Kaj]

Measure the length by using a screwdriver into the hole and taking the measurement, plus the length of the other side. However you may have problems with them sealing properly and not leaking.

[Ethel]

I know all the other threads on them are metric, so it'd worth checking they aren't Metric fine pitch.

[Willpill20]

Ok thanks guys I will let you know if anything happens about this so it would help other in future
Thanks

[Carlos W]

I'm sure they are metric. I sourced some a few years ago

[Spider]

They are a weird odd ball thing, half metric, half imperial. I had a few made a while back, I'll try and remember to measure one later.

[Spider]

They are based it seems on an M8 Bolt, 2" long with a 5/16" UNF Thread. You could possibly get away using 5/16" Bolts, but that can lead to misalignment of the halfs on assembly. The Bolts I had made were in a Grade 12. I seem to recall the originals were a Grade 8.

[lildeucecoop72]

They are based it seems on an M8 Bolt, 2" long with a 5/16" UNF Thread. You could possibly get away using 5/16" Bolts, but that can lead to misalignment of the halfs on assembly. The Bolts I had made were in a Grade 12. I seem to recall the originals were a Grade 8.

Thanks for the info, this is very interesting. I bought my mini in 2007 wth 4-pot metro solid type (non vented) calipers already on the car.


I have decided to overhaul them and I am about to put the calipers together again, and offer up to the car.

I have new pistons with seals, bridge seals and bleed nipples.( will be careful to put together in a clean environment)
I have have new mounting bolts (ERA bolts from Mini Spares that are correct to mate the metro calipers to the mini hub)
I have new metro solid discs on the way and already have the metro flanges that were used before.

I have the original caliper bolts, but would like to replace these - its the final piece of the puzzle.

There seems to be alot of info about not using the old bolts again, as these are stretch bolts.(The ones I have look fine, but I understand that with brakes you can't take chances)
There doesn't seem to be much on where to get replacements.

My questions are:

1) If these bolts arent 'off the shelf' parts and have to be made, what process did you go through to do this (who made them)?

2) What is the 'correct torque', and where did this info come from - AP the manufacturer? (There seems to be divided opintion on this too).

3) Should loctite 270 be used? (Again, much opinion on this here!)


Thanks again! :)

Edited by lildeucecoop72, 06 May 2022 - 08:32 AM.

[Spider]

My questions are:

1) If these bolts arent 'off the shelf' parts and have to be made, what process did you go through to do this (who made them)?

2) What is the 'correct torque', and where did this info come from - AP the manufacturer? (There seems to be divided opintion on this too).

3) Should loctite 270 be used? (Again, much opinion on this here!)


Thanks again! :)

 

This was quite a while back when I went through this exercise.

 

1) There was a small fastener manufacturer near to a client of mine who I got to know, when I found what I did on the Bolts I had, I asked them to confirm what I found which they did and then they offered to make me a couple of sets. They had the gear for rolling threads and being a small shop, it seemed easy for them to do such a small run. I can't even recall if he charged me for them. Sadly, they have since closed up. If I had to do this again, I'd possibly approach ARP or use Unbrako 5/16" UNF Cap Head Bolts, which are Grade 12.

Looking at the Mini Spares and KAD Calipers, they appear to use either a 5/16" or M8 Plated Cap Head Fastener, which would be a minimum of Grade 8 and more likely 10's or even 12's.

 

2) In the absence of any info from AP, I just used standard tables for the size and grade of the original bolts.

 

3) I didn't use any loctite here, just a single drop of light oil on the threads and under the heads.
 

[Ethel]

I have some Minispares 4 pots by my PC (as you do). They are grade 12s, least I hope they are as only 2 have markings.

 

https://www.minispar.../C-AJJ4021.aspx

[lildeucecoop72]

Right....After some research, looks like I have found the bolt values for the Metro caliper (Bolts that hold the two halves of a solid, non vented caliper together, not the caliper to the hub). These bolts are Metric.

 

Head: size 6 umbraco (Allen) or 13mm hex (spanner)

Grade: 12.9

Thread: M8 1.0 (fine) 

Length: 50mm

Shank (ca.)  28mm
Tightening torque (untreated bolts): 45nm / 33ft.lb

Quantity needed per caliper: 4

 

Tightening torque: https://www.fastener...ten_torques.pdf

 

Example: https://www.fixaball...ant=21109948487

 

I have also spoken quite a few who are in the 'use the old bolts again' camp.

I guess it comes down to how well you know the car (where did th calipers come from?), what happened when you undid them, and that they have not been over tightened.

Edited by lildeucecoop72, 09 May 2022 - 07:53 PM.