Rotor grinding against caliper bracket!
Thread Starter
TECH Enthusiast
iTrader: (4)
Joined: Sep 2009
Posts: 534
Likes: 0
From: West TN/KY border
Rotor grinding against caliper bracket! I started a new thread because I figured out the issue! My rear brake rotor/rotors is/are grinding against the brake caliper mounting bracket. They are barely touching, but it's enough the get annoying at speed. I guess the new rotors I put on are just thick enough to make this problem show up. I have heard of two ways to fix it.
1. getting the shims and tearing everything apart.
2. grinding a bit on the mounting bracket.
Personally, I would rather just grind a couple thousandths off the mounting bracket, but I wanted to hear everybody else's opinion before I do anything drastic.
The situation: Installed new pads and rotors, now my back brakes grind. It seems like they make be grinding against the mounting bracket. When you push the wheel in and spin it while the car is in the air, the caliper just barely touches the bracket.
1. getting the shims and tearing everything apart.
2. grinding a bit on the mounting bracket.
Personally, I would rather just grind a couple thousandths off the mounting bracket, but I wanted to hear everybody else's opinion before I do anything drastic.
The situation: Installed new pads and rotors, now my back brakes grind. It seems like they make be grinding against the mounting bracket. When you push the wheel in and spin it while the car is in the air, the caliper just barely touches the bracket.
Seeing I'm a tool & die maker the correct way is to shim out the bracket. Grinding any metal from it will weaken the bracket, even though you say it's a few thousands (which I don't believe to be true since that's the thickness of paper). Deflection of the rotor during braking plus any bearing deflection will amount to more than a few thousands. To be safe shim them out about 1/16 of an inch if it won't cause any interference with the wheel.
I figured those that know nothing about the structural strength of steel and stress factors would say to grind it. Let him do that to his car, this is your car and your safety is on the line so fix it the proper way. Brakes are one of the most important things on a car, don't butcher them up because someone thinks it's ok to do that.
I figured those that know nothing about the structural strength of steel and stress factors would say to grind it. Let him do that to his car, this is your car and your safety is on the line so fix it the proper way. Brakes are one of the most important things on a car, don't butcher them up because someone thinks it's ok to do that.
Do you think the caliper is magically held in place dum-dum?
No the caliper bracket holds it in place while it clamps the brake pads down on the rotor to stop 3500 pounds of mass thats in motion. When you learn about cars open your mouth, otherwise keep it shut because you don't have a clue about the forces involved in braking! That's why the caliper bracket is held in place with grade 8 bolts, which are hardened and so much stronger than a standard bolt which would break off from the tremendous force placed on the brake components.
Besides the caliper floats side to side because of the movement of the caliper pistons so the rotor isn't pushed to one side. The caliper bracket secures it from moving in a circular motion with the rotor.
No the caliper bracket holds it in place while it clamps the brake pads down on the rotor to stop 3500 pounds of mass thats in motion. When you learn about cars open your mouth, otherwise keep it shut because you don't have a clue about the forces involved in braking! That's why the caliper bracket is held in place with grade 8 bolts, which are hardened and so much stronger than a standard bolt which would break off from the tremendous force placed on the brake components.
Besides the caliper floats side to side because of the movement of the caliper pistons so the rotor isn't pushed to one side. The caliper bracket secures it from moving in a circular motion with the rotor.
Last edited by RedHotG8; Mar 31, 2014 at 12:51 AM.
Trending Topics
If it were my car I would seek professional advice, not the opinion of a bunch of amateurs. I've been a tool & die maker for 35 years and work with machining and modifying steel on a daily basis, so I leave the choice for you to decide.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo Thread Starter
TECH Enthusiast
iTrader: (4)
Joined: Sep 2009
Posts: 534
Likes: 0
From: West TN/KY border
It looks like the brakes are pushed out too far compared to the axle. So the shims would actually make the problem worse.
My options now:
1. Put some very thin washers/shims between the rotor and axle.
2. Take a small bit off the inner part of the backing plate from the backing plate.
3. Get a machine shop to shave a few thousandths off the area that actually mounts to the axle housing. Which would effectively move my brakes slightly inward and wouldn't mess with structural rigidity.
My options now:
1. Put some very thin washers/shims between the rotor and axle.
2. Take a small bit off the inner part of the backing plate from the backing plate.
3. Get a machine shop to shave a few thousandths off the area that actually mounts to the axle housing. Which would effectively move my brakes slightly inward and wouldn't mess with structural rigidity.
If i was going to do anything. Would mic the rotor and resurface them rather than the bracket. But before rim companys made front runners with the proper inside diameter we had to grind on the caliper for clearance. I never seen or heard of an issue doing this but theres always a possibility of failure if too much is grinded.
The real question is why does the rotor hit. Have installed many upgraded kits over the years and only had an issue when the part itself was incorrect
The real question is why does the rotor hit. Have installed many upgraded kits over the years and only had an issue when the part itself was incorrect
Thread Starter
TECH Enthusiast
iTrader: (4)
Joined: Sep 2009
Posts: 534
Likes: 0
From: West TN/KY border
It looks like it's been a problem in the past, but my old rotors were just worn down enough to give it enough clearance. But I may get the rotor ground down a bit.
Going on memory here. My LT1 brakes did the same thing. The rotor rubs a some small flat features on the bracket especially when turning. The evidence is clear if you look at the bracket. This started after I changed ring and pinion. When the carrier was re-shimmed, the carrier moved a bit more to the left side and allowed the axle to slightly move with it. This caused the rotor to become a bit closer to the caliper bracket.
These said features on the bracket being contacted do nothing for the structural integrity of the bracket and can be ground down enough to resolve the problem with no ill effect IMO. I ground about .06" off IIRC and it completely resolved the problem.
Bottom line is that GM did not allow enough manufacturing range for this critical dimension and the slightest thing causes the contact to occur. Also bead berings cont squeal or squeak, they rumble and you can feel it in the seat.
As already well said.
Grind that bish.
These said features on the bracket being contacted do nothing for the structural integrity of the bracket and can be ground down enough to resolve the problem with no ill effect IMO. I ground about .06" off IIRC and it completely resolved the problem.
Bottom line is that GM did not allow enough manufacturing range for this critical dimension and the slightest thing causes the contact to occur. Also bead berings cont squeal or squeak, they rumble and you can feel it in the seat.
As already well said.
Grind that bish.
Thread Starter
TECH Enthusiast
iTrader: (4)
Joined: Sep 2009
Posts: 534
Likes: 0
From: West TN/KY border
Going on memory here. My LT1 brakes did the same thing. The rotor rubs a some small flat features on the bracket especially when turning. The evidence is clear if you look at the bracket. This started after I changed ring and pinion. When the carrier was re-shimmed, the carrier moved a bit more to the left side and allowed the axle to slightly move with it. This caused the rotor to become a bit closer to the caliper bracket.
These said features on the bracket being contacted do nothing for the structural integrity of the bracket and can be ground down enough to resolve the problem with no ill effect IMO. I ground about .06" off IIRC and it completely resolved the problem.
Bottom line is that GM did not allow enough manufacturing range for this critical dimension and the slightest thing causes the contact to occur. Also bead berings cont squeal or squeak, they rumble and you can feel it in the seat.
As already well said.
Grind that bish.
These said features on the bracket being contacted do nothing for the structural integrity of the bracket and can be ground down enough to resolve the problem with no ill effect IMO. I ground about .06" off IIRC and it completely resolved the problem.
Bottom line is that GM did not allow enough manufacturing range for this critical dimension and the slightest thing causes the contact to occur. Also bead berings cont squeal or squeak, they rumble and you can feel it in the seat.
As already well said.
Grind that bish.
TECH Addict
Joined: Feb 2012
Posts: 2,103
Likes: 21
Wow RedHot you got pretty fired up over this....
Based on your very passionate response about your vast knowledge of stresses involved in slowing down a 3900lb car, can you shed some light in an analytical manner on the following:
1)What is the clamping force of the caliper on the rotor during say 100% braking?
2)Given said force, what is the friction coefficient and therefore the amount of heat generated/dissipated during this situation?
3)From said force/friction coefficient/heat relationship, how does this play a role in the amount of rotational/torsional stress applied to the caliper bracket and therefore what are the shearing stresses on the bolt we are dealing with?
Aaaand GO!
Based on your very passionate response about your vast knowledge of stresses involved in slowing down a 3900lb car, can you shed some light in an analytical manner on the following:
1)What is the clamping force of the caliper on the rotor during say 100% braking?
2)Given said force, what is the friction coefficient and therefore the amount of heat generated/dissipated during this situation?
3)From said force/friction coefficient/heat relationship, how does this play a role in the amount of rotational/torsional stress applied to the caliper bracket and therefore what are the shearing stresses on the bolt we are dealing with?
Aaaand GO!
TECH Addict
Joined: Feb 2012
Posts: 2,103
Likes: 21
RedHot brought it up in his post acting like a bit of an a$$ making it seem like everyone is dumb and he is smarter/better than everyone.
IMO, evaluate WHY it is rubbing. If you can simply toss a washer in there to "space" the bracket away then I would do that. But...a picture is worth 1000 words.
IMO, evaluate WHY it is rubbing. If you can simply toss a washer in there to "space" the bracket away then I would do that. But...a picture is worth 1000 words.
Thread Starter
TECH Enthusiast
iTrader: (4)
Joined: Sep 2009
Posts: 534
Likes: 0
From: West TN/KY border
RedHot brought it up in his post acting like a bit of an a$$ making it seem like everyone is dumb and he is smarter/better than everyone.
IMO, evaluate WHY it is rubbing. If you can simply toss a washer in there to "space" the bracket away then I would do that. But...a picture is worth 1000 words.
IMO, evaluate WHY it is rubbing. If you can simply toss a washer in there to "space" the bracket away then I would do that. But...a picture is worth 1000 words.
Anyway! I'm going through and looking at everything right now, and checking for clearances. I will post up a pic if I can manage to take one with my god awful cell camera!
