New brake job issue

[Mike Guenther]

I'm trying to put new rotors and new Hawk Blues on my 325 and I can not get them on. So I measured the new rotors at .865 and the new pads at a combined 1.370 for a total of 2.235. Even with the old rotor at .856 the total clearance needed is 2.226.

I measured the distance between the caliper and piston with a clamp squeezing in the piston and it was 2.192(max).

I didn't notice any need to install the piston in a certain position to get it fully retracted, so I am assuming that 2.192 is the maximum possible clearance.

Did I miss something or do something wrong in assembling the caliper?
Or do the Hawk Blues need to be shaved to use them?

[JoshS]

I'm trying to put new rotors and new Hawk Blues on my 325 and I can not get them on. So I measured the new rotors at .865 and the new pads at a combined 1.370 for a total of 2.235. Even with the old rotor at .856 the total clearance needed is 2.226.

I measured the distance between the caliper and piston with a clamp squeezing in the piston and it was 2.192(max).

I didn't notice any need to install the piston in a certain position to get it fully retracted, so I am assuming that 2.192 is the maximum possible clearance.

Did I miss something or do something wrong in assembling the caliper?
Or do the Hawk Blues need to be shaved to use them?
Check the Hawk box. Do you have the right part? (I think it's HB136 for your car?)

[Mike Guenther]

I do believe that they are the correct pads. They have the exact shape as the ones I took off and I got them from Bimmer Specialists. The rotor is Brembo. But even using the old rotor the stack is too thick to fit into the caliper.

[CRallo]

wow... that reminds me of a funny story...

did a brake job on my Saturn SL2 street car that my girlfriend was driving at the time. She drove the car to work and then called me freaking out!! the brakes were dragging and smoking!

went down there, found nothing wrong because, once cooled, they freed up. Noticing how lil extra clearance there was and finding no other issues I took out the lil "anti squeal/rattle" plates that were on the backing plates, put the car back together and it was good to go :)

once heated from braking the pads and rotors must have expanded more than and/or before the calipers and closed up the already almost zero clearance...

guess that is somewhat relevant :shrug:

[Eagle7]

Similar thing happened to me at Mid-Ohio last year. After 3/4 of a lap I could hardly make it back to the pits. Once it cooled it rolled free. Evidently I had raised my brake pedal a little too high. Lowered it a couple turns and problem solved. Lost most of a test day getting it figured it out though.

[dj10]

I do believe that they are the correct pads. They have the exact shape as the ones I took off and I got them from Bimmer Specialists. The rotor is Brembo. But even using the old rotor the stack is too thick to fit into the caliper.

Mike, double check the pad #on the brake pads. I've had a similar problem, just bevel the edges of the pads as long as you know they are the right pad for the car.....or return the pads for another set.

[Gary L]

If the part number is HB136.690, the ".690" represents pad thickness in inches (one pad, including the backing plate). You say that the two pads measure 1.370" total, half of that is .685"; it would appear the pads are actually slightly thinner than design intent.

[maynard]

Hey mike we had similar problems with hawk blues on our 325i. I double checked the number on the box and it was right, but when i put the brake pads on a flat surface i saw the one of the band new pads was bent.If not just tell hawk to send you new ones like dan said.

[Mike Guenther]

Thanks guys. I didn't have any problem with the rear, just the front. The piston didn't look like it was all the way down, even with a clamp on it. So I decided that I had to take the calipers apart again to check to see if I had rolled the piston seal out of the groove and it was preventing the piston from traveling all the way to the bottom of the cylinder. I was even more suspicious after I took the caliper off and I couldn't rotate the piston or pull it out by hand.

I popped it out and checked the seal and it was properly in the groove. I measured the depth of the cylinder and the height of the piston and reassembled it. Low and behold if it didn't go in further this time and everything fit back together. I repeated this on the other side with the same result.

I don't know how or why I got the pistons in 95% of the way and then apparently got them both cocked and couldn't push them all the way in. It was a frustrating experience, but I learned a thing or two.

Thank you for your suggestions. Be safe out there.

[Edwin Robinson]

I'm trying to put new rotors and new Hawk Blues on my 325 and I can not get them on. So I measured the new rotors at .865 and the new pads at a combined 1.370 for a total of 2.235. Even with the old rotor at .856 the total clearance needed is 2.226.

I measured the distance between the caliper and piston with a clamp squeezing in the piston and it was 2.192(max).

I didn't notice any need to install the piston in a certain position to get it fully retracted, so I am assuming that 2.192 is the maximum possible clearance.

Did I miss something or do something wrong in assembling the caliper?
Or do the Hawk Blues need to be shaved to use them?

The correct thickness for these pads is .690" - which seems to be what you have there.
The thickness for the front rotor is 21.8mm (new) = .860"
Hope that helps.

Best Regards,
Edwin Robinson.

[Mike Guenther]

Dang Edwin, you're pointing out how sloppy I am with my caliper.:blink:

Thanks for the accurate info. I appreciate it.