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      09-28-2019, 10:35 PM   #1
asbrr
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135i Calipers - Bolt Torque Specs Please!

Doing the front brakes tomorrow, after a bunch of reasearch/watching videos I concluded I would not be touching the torx T40 bolts that help retain the pads.

Plan was to only remove the 10mm hex bolts and try to get the pads out like that. I opened the stoptech sport brake pad box and realized they ship with brand new T40 bolts and pad retaining clips. So I figure I'll swap those to the new ones.

The 10mm hex bolts after a lot of digging look like they need to be tightened to 80 ft.lb

Does any one know the torque spec of the T40 "guide pin" bolts please??? See part #4 in the RealOEM diagram attached.

Thanks in advance
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      09-28-2019, 11:21 PM   #2
asbrr
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Hmm....just read the monster thread on caliper bolt part number here:
https://www.1addicts.com/forums/show...er+bolt+torque

Seems the correct way to remove the calipers is using the #2 carrier bolt instead of the 10mm hex bolt.

So having said that, anyone know the torque for the #2 bolt AND the #4 bolt please? Pretty please??
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      09-28-2019, 11:43 PM   #3
bchalks
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The T40 Torx bolts for the guide pins will just bottom out. I never torque mine...

I've swapped pads several times. And here is my process:
1. Loosen Torx bolts (#4)
2. Remove mounting bolts on back of caliper (#2)
3. Remove pads
4. Install new pads by pushing up on retaining clip (#3) and sliding new pad onto torx guide pin (#4)

Last edited by bchalks; 09-28-2019 at 11:51 PM..
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      09-29-2019, 08:39 AM   #4
asbrr
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Quote:
Originally Posted by bchalks View Post
The T40 Torx bolts for the guide pins will just bottom out. I never torque mine...

I've swapped pads several times. And here is my process:
1. Loosen Torx bolts (#4)
2. Remove mounting bolts on back of caliper (#2)
3. Remove pads
4. Install new pads by pushing up on retaining clip (#3) and sliding new pad onto torx guide pin (#4)
Thanks - I ended up finding the specs in this thread:

https://www.1addicts.com/forums/showthread.php?t=956074

So the caliper carrier bolts (#2) are 81 ft.lbs and the T40 guide pins are 22 ft.lbs.

Also - don't know why I haven't seen this before - found this site that has a ton of info:

https://www.newtis.info/

Front brakes procedure:
https://www.newtis.info/tisv2/a/en/e...brakes/GT4BRds

Torque Specs:
https://www.newtis.info/tisv2/a/en/e...brakes/5VN2mEL
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      09-30-2019, 09:42 AM   #5
asbrr
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As an update - I had all the right intentions and planned to remove the calipers by removing the bracket from the steering knuckle. Now I understand why nobody does it that way when you're working on your car on a jack, and no access to quality air tools that fit "behind" the rotor/caliper lol. There was no way to get enough leverage to break the bolts free....so I had a choice to make and I decided to "cheat" and went for the 10mm Hex bolts.

My god that is a pants-shittingly terrifying experience breaking them loose for the first time. I used a 24" breaker bar and they came out ok on driver's side, the weird sensation is that the tension doesn't ease the first 5-10 turns because of the factory thread locker that's applied. I kept thinking I'm gonna break them lol. The passenger side is another story - they were gunked up way more and there was a lot of horrible screeching noises....I thought for sure I broke them at several points, after much sweating and hand wringing I kept going and they finally came out.

THinking I was home free, had the caliper ready to go cleaned up with new pads, I failed at the rotor set screw - f*@cking thing partially stripped as it's so hard to apply force while holding the rotor still -

How do people do this/what is the right technique???

It was late with no stores open and I didn't have spares (I forgot, I'm an idiot). So I put the new pads on the old rotor and took it to my mechanic this morning who had it all sorted in 15 minutes lol - helps to be a pro and have a lift and the right tools

Anyway - glad I'm done with this for a while - brakes feel great, my ego is mostly intact and I still have a sense of satisfaction that I got 90% of the job done myself!

I ended up torquing the 10mm hex bolts to 80 ft.lbs seemed plenty tight and in line with everyone else. Don't think I'd do this myself again, but glad I did it once for the experience.


EDIT: The stoptech sport pads came with nice new guide pin bolts....so taking the old ones out was on the cards and I'm glad I did. I highly recommend everyone change these whenever you swap old/crusty pads out. Deposits build up on the pins and I know my inner pads were worn down way more than outers - likely due to a combo of build up on the guide pins as well as the caliper surfaces where the pad has to "slide" against in and out. They are cheap and available at rockauto.com for example....
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      10-01-2019, 04:48 PM   #6
fe1rx
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Quote:
Originally Posted by asbrr View Post
As an update - I had all the right intentions and planned to remove the calipers by removing the bracket from the steering knuckle. Now I understand why nobody does it that way when you're working on your car on a jack, and no access to quality air tools that fit "behind" the rotor/caliper lol. There was no way to get enough leverage to break the bolts free....so I had a choice to make and I decided to "cheat" and went for the 10mm Hex bolts..
You mean a jack AND jackstands don't you?

Turn the wheel fully and you get good access to the bolts. I have never had a problem getting the correct 18 mm hex head M12 bolts out or torqueing them properly when working from jackstands, and I have done it more times than I can count.

As for the socket head cap screws you call 10 mm - I thought that horse had been beaten dead years ago. They aren't supposed to come out - ever. And the implications of breaking one are much more expensive than starting out with the right tools. Absent an impact gun you need a suitable 1/2" drive breaker bar and 1/2" drive ratchet and a small assortment of extensions to go with your 18 mm socket. 3/8" drive is inadequate for this job. And you need those jackstands because you will be under the car. And a 1/2" drive torque wrench too, of course.
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      10-01-2019, 04:52 PM   #7
fe1rx
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Quote:
Originally Posted by asbrr View Post
THinking I was home free, had the caliper ready to go cleaned up with new pads, I failed at the rotor set screw - f*@cking thing partially stripped as it's so hard to apply force while holding the rotor still -

How do people do this/what is the right technique???.
Put a screwdriver into the rotor vents and turn the rotor ccw until the screwdriver contacts the caliper. Put a bit of wood between the screwdriver and the caliper. This will stop it rotating while you remove that rotor set screw.
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      10-01-2019, 05:13 PM   #8
asbrr
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Quote:
Originally Posted by fe1rx View Post
Put a screwdriver into the rotor vents and turn the rotor ccw until the screwdriver contacts the caliper. Put a bit of wood between the screwdriver and the caliper. This will stop it rotating while you remove that rotor set screw.
Ok that makes a lot of sense, I was tired and frustrated so couldn't think of any creative ways to do this lol.
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      10-01-2019, 05:39 PM   #9
asbrr
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Quote:
Originally Posted by fe1rx View Post
You mean a jack AND jackstands don't you?

Turn the wheel fully and you get good access to the bolts. I have never had a problem getting the correct 18 mm hex head M12 bolts out or torqueing them properly when working from jackstands, and I have done it more times than I can count.

As for the socket head cap screws you call 10 mm - I thought that horse had been beaten dead years ago. They aren't supposed to come out - ever. And the implications of breaking one are much more expensive than starting out with the right tools. Absent an impact gun you need a suitable 1/2" drive breaker bar and 1/2" drive ratchet and a small assortment of extensions to go with your 18 mm socket. 3/8" drive is inadequate for this job. And you need those jackstands because you will be under the car. And a 1/2" drive torque wrench too, of course.

Yes absolutely - my jack is a locking design, it effectively becomes a jack stand because it has a metal bar that inserts through pre-formed holes in the jack arm (two pre-set height positions) to hold the arm up with no hydraulic tension. Haven't seen too many jacks like this but for the minimal work I do this turned out nicely.

And on the socket cap head screws - I know, the consensus was after all the reading to never take them out. I went ahead against better judgement, accepting the risk of breaking them (hence my sweating). Won't be doing that again. I inspected all of them closely, cleaned them off and cleaned the caliper bracket threads as well. Added a small tiny of loctite on the threads when I put them back. Will not touch them again.

For the 18mm Hex - Definitely have the 1/2" breaker bar and ratchet and even impact socket. Couldn't fit my shitty impact gun behind the turned wheel. I think it's because I wasn't on jack stands and the jack height I had set (and locked into) was not that high. Also as I raised one side of the car with the wheel turned fully, it naturally turned back slightly the higher I went. I can see how on jack stands it would be easier....ah well, live and learn.
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