Caliper Stripped Thread - Advice please

C

Cliff

Member
Upon removing the Guide Pins for the brake calipers 3 of the 4 threaded holes have stripped out of the Hub Carriers. I have put a Re-Coil in one to see how it worked but the Guide Pin will not 'engage' in the new thread. I have stopped all work to think about it as replacing both Hub Carriers will probably financially write the car off. It occured to me that possibly the thread in the Re-coil is incorrect. I have put in a M9 x 1.25 insert which fitted perfectly when I tried it 'dry' with a Guide pin out of the box. I have spoken to the Audi main dealer (Cheltenham), who were unable to tell me what the Guide Pin thread is.
Can any body tell me what the Guide Pin thread spec is please.
I may just drill and tap the existing holes out to M10 or M11 and have some new Guide Pins turned up by an engineering company, at least then all the threads would match.
I am sure that I can't be the first this has happened to especially as I was just undoing them and have not stripped these by overtightening !!
Thanks,
Cliff.
 
Seems to be a common problem. M9x1.25 is the correct thread size but I guess it's very tricky to drill and tap the stripped thread 'dead square' to ensure the perfect alignment needed.

Brake Caliper Carrier and Slide pins

Having recently replaced the brake discs on my A2, when putting them back together i found that one of the slide pins threads was in very poor condition and wouldn't tighten up. Now i'm after a new slide pin or pair of plus a caliper carrier as the threads could well be damaged in that also...
www.a2oc.net

Cheers Spike

PS. You obviously know how to do the repair but here's another more detailed guide for others who may encounter the same problem -

Caliper sliding tube / bolt thread repair . Heli coil thread repair

I was changing front brakes on Audi A2, threads on calliper bolts / sliders are disintegrated and rusted on hub carrier. I have re-cut the threads and install a Heli coil to repair this, you need M9 Heli coil kit (M9 Thread pitch 1.25 coil length about 13mm long), kit comes with drill but and...
www.a2oc.net
 
Are you sure the threads are not 9mm x 1mm? I once managed to break off one on my Lupo 3L. I drilled out the centre and re-tapped with a 9mm tap (which I am trying to find). The tap picked out the remains of the pin and the new guide pin fitted perfectly. I am not sure I would use a Helicoil given the safety aspect and the difficulty of getting the correct angle - the caliper will seize if the angle is wrong.

Use heat and releasing agent to remove old guide pins. They break very easily. Patience required!

RAB
 
M9X1.25 is the correct thread size, however i have used this kit before

51951
 
Yes, just found a new guide sleeve for a 1.2Tdi - 9mm x 1.25mm.

RAB
 
Cliff said:
Upon removing the Guide Pins for the brake calipers 3 of the 4 threaded holes have stripped out of the Hub Carriers. I have put a Re-Coil in one to see how it worked but the Guide Pin will not 'engage' in the new thread. I have stopped all work to think about it as replacing both Hub Carriers will probably financially write the car off. It occured to me that possibly the thread in the Re-coil is incorrect. I have put in a M9 x 1.25 insert which fitted perfectly when I tried it 'dry' with a Guide pin out of the box. I have spoken to the Audi main dealer (Cheltenham), who were unable to tell me what the Guide Pin thread is.
Can any body tell me what the Guide Pin thread spec is please.
I may just drill and tap the existing holes out to M10 or M11 and have some new Guide Pins turned up by an engineering company, at least then all the threads would match.
I am sure that I can't be the first this has happened to especially as I was just undoing them and have not stripped these by overtightening !!
Thanks,
Cliff.
Click to expand...
I assume that you drilled the hole and tapped it to suit the helicoil insert and did not just insert the helicoil into the existing thread (stupid question but I have seen it done before :))
 
You can buy new hub uprights from Autodoc. They are Bugiad make, which I had never heard of, but the price was very good so I took a gamble on a pair when I did my front end rebuild last year. I bought them for the same reason as the OP - damaged threads for the brake slider pins.

I needn't have worried - the quality seems very good, critical dimensions matched the originals (checked with verniers and a height gauge on my surface plate) and I had no problems at all when assembling them. New FAG wheel bearings seated smoothly and I've had no problems with vibration or warped discs. No problems with wheel alignment. The forgings even carry the VAG part numbers, so could well be the OEM parts. I'm coming up to the time for my annual service soon so I'll give them a good look over and report back on how they are getting on.
 
spike said:
Not seen this kit before so was intrigued to understand how it worked.
Youtube to the rescue -

Cheers Spike
Click to expand...
Very easy to work with,in the youtube video, i would advise not to hammer in the insert as you may crush / squash the insert, damaging the internal thread, must be pressed in ( g-clamp )
 
spike said:
Seems to be a common problem. M9x1.25 is the correct thread size but I guess it's very tricky to drill and tap the stripped thread 'dead square' to ensure the perfect alignment needed.

Brake Caliper Carrier and Slide pins

Having recently replaced the brake discs on my A2, when putting them back together i found that one of the slide pins threads was in very poor condition and wouldn't tighten up. Now i'm after a new slide pin or pair of plus a caliper carrier as the threads could well be damaged in that also...
www.a2oc.net

Cheers Spike

PS. You obviously know how to do the repair but here's another more detailed guide for others who may encounter the same problem -

Caliper sliding tube / bolt thread repair . Heli coil thread repair

I was changing front brakes on Audi A2, threads on calliper bolts / sliders are disintegrated and rusted on hub carrier. I have re-cut the threads and install a Heli coil to repair this, you need M9 Heli coil kit (M9 Thread pitch 1.25 coil length about 13mm long), kit comes with drill but and...
www.a2oc.net
Click to expand...
Spike,
Thanks for the reply, still not decided what to do with it all.
Cliff.
 
TFG said:
You can buy new hub uprights from Autodoc. They are Bugiad make, which I had never heard of, but the price was very good so I took a gamble on a pair when I did my front end rebuild last year. I bought them for the same reason as the OP - damaged threads for the brake slider pins.

I needn't have worried - the quality seems very good, critical dimensions matched the originals (checked with verniers and a height gauge on my surface plate) and I had no problems at all when assembling them. New FAG wheel bearings seated smoothly and I've had no problems with vibration or warped discs. No problems with wheel alignment. The forgings even carry the VAG part numbers, so could well be the OEM parts. I'm coming up to the time for my annual service soon so I'll give them a good look over and report back on how they are getting on.
Click to expand...
Thanks for that I will look them up but I was trying to get away from having to do all that work on the front end
 
spike said:
Not seen this kit before so was intrigued to understand how it worked.
Youtube to the rescue -

Cheers Spike
Click to expand...
Spike,
This u-Tube was brilliant - Thanks. The new inserts look a bit like Rivet Nuts which I did discuss with my local fastening supplier who laughed at me, but I thought at the time was still a good approach as the inserts are slightly splined and should lock in to prevent turning. I may follow this up and go this route. I spoke to the Audi dealer re the cost of new pins and was quoted £22 + VAT for EACH one !!! so I may get a die nut to clean up the original ones.
Thanks for the info much appreciated.
Cliff
 
Kaz said:
why not just get a second hand hub from one of the resident breakers?
Click to expand...
Well, it is a bit of work. The hub you get from the breakers may or may not be in good order. Maybe the wheel bearing in it is bad. Maybe you have a new ish wheel bearing in yours. I suppose you cannot reuse the bearing. Maybe you don't own the special press tool that you need to fit wheel bearings, and also to press the driveshaft free (from what I understand).
 
Cliff said:
Spike,
This u-Tube was brilliant - Thanks. The new inserts look a bit like Rivet Nuts which I did discuss with my local fastening supplier who laughed at me, but I thought at the time was still a good approach as the inserts are slightly splined and should lock in to prevent turning. I may follow this up and go this route. I spoke to the Audi dealer re the cost of new pins and was quoted £22 + VAT for EACH one !!! so I may get a die nut to clean up the original ones.
Thanks for the info much appreciated.
Cliff
Click to expand...
He may not have understood that it's not a riveting nut per se. Riveting nuts are fastened from the front. A rivet nut is stuck in the hole solely because it was crushed/forced wide by the press tool. This caliper mount repair solution may look similar to a rivet nut - but is fastened from the back side. It has a lip and washer, which has to disintegrate for the bush to be allowed to pull through and out of the hole. It is a "heavy duty rustproof high-grade steel threaded bush" (or so we hope). You also use the strongest loctite you can find. And remember, the caliper is not pulling on these pins. It is by design meant to float on them. The braking force is applied 90 degress to the bolts.
 
You must log in or register to reply here.
Back
Top