FRONT Brake Caliper Bolts: To replace or not to replace?

Whenever I replace a rotor in any of my cars for the last 20 years (1991 Volvo 240, 1998 Volvo V70, 1983 BMW 735i etc. etc.), I always re-used the 2 BOLTS that hold the brake caliper to the steering knuckle, and have never had problem.

I just happened to read the service manual for my 1998 Volvo V70, it says:
"whenever removing the brake caliper, use new bolts."

We re-use wheel lug bolts/nuts all the time, and why replace the brake caliper bolts? I understand the brake system is important for safety but isn't it a bit paranoid to change the brake bolts every time you change the rotor? I guess it does not hurt to do that but I just want to understand the logistics behind it.

So the obvious question: do you guys replace your brake caliper BOLTS when changing rotors at all?

I didn't...

Look at it this way:
If it *WAS* dangerous to re-use the bolts, then wouldn`t you have to replace the calipers, too ? Why one without the other ? "Highly illogical, Mr. Spock"....

If it was dangerous to re-use the bolts, shouldn't BMW include them with the pads, a la Oil Filter Kit?

I just changed 4 pads and reused all four caliper bolts. I have never seen it written anywhere (Bentleys, BMW TIS, DIYs, Zeckhausen, etc.) that these bolts need to be replaced. The loading on these bolts is in shear. You would need a lot of force to shear one of those bolts. As long as you torque it properly, it should not loosen and you should be fine. Relax...

I would always replace bolts that the manual calls for. Sometimes they are "stretch" bolts that are only good for one use. I would hate to find out that i should have replaced them after the fact

I didn't and would'nt. I mean they are not too expensive but when it came to the front wheel bearings they say replace them. And the wheel bearings come with new bolts. I dont think the calipers come with new bolts when you buy them.

I just checked on BMW's website and it says nothing about replacing the bolts. Just torque them down and you're fine.

Originally Posted by d geek

I would always replace bolts that the manual calls for. Sometimes they are "stretch" bolts that are only good for one use. I would hate to find out that i should have replaced them after the fact

Flywheel bolts, head bolts, rod bolts,and several others meet this criteria....caliper bolts do not, AFAIK....

Originally Posted by Fast Bob

Flywheel bolts, head bolts, rod bolts,and several others meet this criteria....caliper bolts do not, AFAIK....

I advocate following the manual. My VW manual also calls for the bolts to be replaced. If the BMW manual does not call for it, then there must be a good reason for it (as in the bolts that were picked for this application are good for multiple uses).

I think I can tell you why they suggest it. I did a brake job a few years ago on my son's 318i and the caliper bolts almost seized due to the age and corrosion. I don't think it was tightened too much but the age and corrosion caused it to be very tough to remove. I had to put so much force on the bolts to get them off I was afraid that the head of the bolt would shear off. It didn't but I know I weakened the bolt and would be concerned if I put that much force on it again. Hopefully, I'll never have to find out but in retrospect, I probably should have changed the bolt, especially now that the car is nearly 20 years old.

Originally Posted by mhughett

I think I can tell you why they suggest it. I did a brake job a few years ago on my son's 318i and the caliper bolts almost seized due to the age and corrosion. I don't think it was tightened too much but the age and corrosion caused it to be very tough to remove. I had to put so much force on the bolts to get them off I was afraid that the head of the bolt would shear off. It didn't but I know I weakened the bolt and would be concerned if I put that much force on it again. Hopefully, I'll never have to find out but in retrospect, I probably should have changed the bolt, especially now that the car is nearly 20 years old.

Very good. Common sense.

i dont see those bolts failing, they are pretty darn thick. i wouldnt worry about it too much. if you are up north and have an issue threading the bolt back in cleanly due to corrosion, then i can see changing it out.

Guys, I can partially see why they say to replace the bolts. The shear force of getting the bolts off made he ones I took off weak. Not know when I went to put it all back together the bolt popped well below the 81 torque specs that was posted in the manual. I had to use some others to hold me down tell I get to the dealer. Just my 2 cents to change them but I will not change them all the time though

if you can find out the bolt grade, that would be a good indication of strength. metric bolts have numbers on them. higher numbers indicate higher strength.

if you feel the tensile the strength of the bolt is not up to par, then replace them. other than that, if the manufacture does not require you to replace them, then they must be rather strong bolts. your volvo they must have a good reason for replacing them.

I replace every bolt I remove every time.

Originally Posted by My39

if you can find out the bolt grade, that would be a good indication of strength. metric bolts have numbers on them. higher numbers indicate higher strength.

if you feel the tensile the strength of the bolt is not up to par, then replace them. other than that, if the manufacture does not require you to replace them, then they must be rather strong bolts. your volvo they must have a good reason for replacing them.

Old hot rodding adage: "When in doubt, go stronger"
With that in mind, these are the bolts you want for high-strength applications....(Grade 8)

I think BMW uses grade 10.9.

Originally Posted by Fudman

I just changed 4 pads and reused all four caliper bolts. I have never seen it written anywhere (Bentleys, BMW TIS, DIYs, Zeckhausen, etc.) that these bolts need to be replaced. The loading on these bolts is in shear. You would need a lot of force to shear one of those bolts. As long as you torque it properly, it should not loosen and you should be fine. Relax...

Unless you're changing the rotor, you should not have to remove the caliper bolts. To be sure we're all talking about the same thing, the caliper bolts are the 18mm bolts (in front) that attach the caliper carrier (bracket) to the steering knuckle. BMW does not call for these to be replaced each time they are removed for a rotor change. We're not talking about the 7mm Allen bolts that retain the caliper to the caliper carrier. THOSE are removed in order to replace the pads. And those also do not have to be replaced unless they are damaged.

The lack of explicit instructions to replace a bolt does not replace common sense. If you're working on a BMW that's 20 years old and has been sitting outside in Massachusetts (they use the most caustic ice melting chemicals around) , and the bolts look like they're in bad shape, then it's not a bad idea to replace them.

Ironically, I was removing these bolts today as I upgraded my front StopTech ST-40 big brake kit to ST-60 calipers.

"If you're working on a BMW that's 20 years old and has been sitting outside in Massachusetts (they use the most caustic ice melting chemicals around) , and the bolts look like they're in bad shape, then it's not a bad idea to replace them."

+1, living in the People's Republic is not conducive to long term BMW ownership!

When I replaced my front rotors/pads last year one of my bolts was clearly bent and it had to be replaced. I have no idea how it became damaged.

Originally Posted by DavidZ

When I replaced my front rotors/pads last year one of my bolts was clearly bent and it had to be replaced. I have no idea how it became damaged.

If the bolt that is removed is distorted, then replace it. Otherwise, claen them up and make sure to use a caliper pin/bolt grease before installing.
This is the thick green pasty stuff that has a brush applicator on the lid.

stlbmw

Originally Posted by stlbmw

If the bolt that is removed is distorted, then replace it. Otherwise, claen them up and make sure to use a caliper pin/bolt grease before installing.
This is the thick green pasty stuff that has a brush applicator on the lid.

You do NOT want to apply any grease to the caliper guide bolts. Grease will cause the rubber bushings the caliper slides back and forth on to swell and the caliper will stick, causing excessive outboard pad wear.

Originally Posted by DZeckhausen

You do NOT want to apply any grease to the caliper guide bolts. Grease will cause the rubber bushings the caliper slides back and forth on to swell and the caliper will stick, causing excessive outboard pad wear.

I see in this case, no grease in called for.
There are some assemblies that do require it.
I guess thats why it exists.

stlbmw

Well,

Regarding greasing guide pins: I have done it for 20 years in all of my cars, not a problem.
I do this every 2 years during brake fluid flush: I take the guide pins out for inspection, clean it and put a very slight dab of grease.

That topic of To Lube or not to Lube Brake Guide Pin ha been discussed before:
http://www.bimmerfest.com/forums/sho....php?p=4523566

I think BMW is being anal-paranoid about it, many other car mfgs use a bit of grease on guide pins FYI.