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Grinding front brakes after rim and tire swap

5K views 14 replies 7 participants last post by  GSBuilder 
#1 · (Edited)
Just changed from A/S on 16" wheels to M/S on 15" wheels for winter. On first trip around town there's quite a bit of grinding/groaning noise coming from the front wheels, but maybe more on the right side (passenger). This noise wasn't there on the A/S tires and wheels. This is at all speeds, and also maybe in reverse...

The M/S have noticeable cupping. 205/65/15 (1 of 4 brand new)

The A/S are 205/55, which is approx. 3% smaller diameter than OEM specs... Shorty after installing it snowed, and I noticed that the brakes lock-up when the brake pedal is fully depressed when trying to slide to a stop (causes judders). However, it seems that in snowless/iceless conditions, the lock-up doesn't occur.

The M/S rims were very dusty (old mud?) and had some rust before I put them on. Should I take them off and clean them? And also clean my rotors while I'm there?

Maybe the cupping of the M/S is causing this, or the ~3% difference in the 205/55's caused some permanent damage? It seems like a caliper is sticking... Maybe the change of tires wore out whatever amount of pads that I thought I had left.... :roll:?

Any ideas?

Thanks :)
 
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#4 · (Edited)
Regular 2.3l turbo sedan. The tires should be within my specs, but they are mud/snows and the specs call for snows only with 195/65/15. So not sure if this matters so much?

Maybe someone installed non-oem parts or calipers?

I was using the star pattern, but I may have them over-torqued, as I made about 3 passes at the bolts. The tires have quite a bit of cupping... Thinking I may go back to the A/S in hopes of having functioning brakes. :lol:
 
#5 ·
15" is recommended for non-aeros like yours for winter wheels. I would take off the front wheels and inspect the rims for damage and also the calipers and rotors. Look at the pads as well, perhaps you sheared a pad and the fact it started when you switched tires is coincidental. Also look for uneven pad wear that would indicate caliper bushing wear. Your tire and wheels should not be making contact, this is an acceptable size combination for your car.
 
G
#6 ·
The small difference in tire size shouldn't be causing any problems. Are the winter wheels original Saab wheels? Have you had these on your car before?

Take the wheels off and check to see if there is any wear on the outside of the calipers or inside of the wheels.
 
#8 ·
Not sure why, but the front pads are locked onto the front rotors. I put the wheels up and they spin, but the pads are grinding away :confused:....

Going to switch back to the 16" 205/55's up front to see if it helps.

The 15" tires were on the car last winter, but I don't know if the wheels are Saab or not...
 
#9 ·
If you can spin it fairly easily by hand, they are normal. The hydraulics in the caliper cannot pull the pad completely from the rotor face, so when spun by hand they will sound to be dragging.

This is why old drag racers prefer drum brakes. They don't care much about repeated stopping power, and drums have springs to pull the shoes from the drum, eliminating friction.

The way you described juddering on ice/snow but not dry roads during hard braking sounds like ABS activation to me, not anything bad. This will make a buzzing noise and shivers in the brake pedal.

Check for contact wear on the system, and ensure the dust shields are not bent onto the caliper as others have said already. I doubt the wheel change will solve your issue.
 
#12 ·
The rotor set screw isnt necessary, however it makes life easier. THat's an easy fix. Im more converned w/ the cupping as it may lead to a number of suspension problems. Is there cupping on the 16" tires also? If you are just seeing it on the 15" then I would measure the rims because you may not have 15" rims (common cupping reason rim/tire mismatch). If the cupping is happening on more than 1 tire and ONLY on the 15's than you probably have the wrong rim on there. If the rims are smaller than thought (say 14.5/14, then you could have easily damaged your breaking system. If it is happening on both, then there may be need for suspension parts, wheel bearings, and/or alignment.

The tire size diff of 3% shouldn't matter. I do that on mine too. Make sure when turning that they arent rubbing in the wheel well.

I would check that first.
 
#14 · (Edited)
The rotor set screw isnt necessary, however it makes life easier. THat's an easy fix. Im more converned w/ the cupping as it may lead to a number of suspension problems. Is there cupping on the 16" tires also? If you are just seeing it on the 15" then I would measure the rims because you may not have 15" rims (common cupping reason rim/tire mismatch). If the cupping is happening on more than 1 tire and ONLY on the 15's than you probably have the wrong rim on there. If the rims are smaller than thought (say 14.5/14, then you could have easily damaged your breaking system. If it is happening on both, then there may be need for suspension parts, wheel bearings, and/or alignment.
I'll have to check the 15" wheels for the exact diameter. The cupping occurs on all four tires, and on both the 15" and 16" wheels. It's also worn very unevenly, seeming to be that every foot or so around the circumference--in addition to cupping--there has occurred wide swath of bald spot.

My best option right now is probably to bring it to a local mechanic, as I don't have much experience is diagnosing steering, suspension, alignment and brake issues...

However....

The right front side drags and pulls the steering to the right. Occasionally, the dragging in the steering in the right side will subside, and as it does this, it will shift to dragging on the left front side. This doesn't last too long and then it's back to dragging on the front ride side. (It feels like the steering is a ships mast, and it never it standing up straight, and instead is always leaning to one side or the other).

The parking brake seems to be OK. At the beginning of winter the parking brake froze up, and it took some hot water and rags to get it to release (since then I've had a chance to test the parking brake and it seems to work OK, and to be fully released).

Is there any way to reset the MPG and miles traveled on the SID? Pressing the Clear button does the job of resetting the MPG, however, the miles traveled still remains (although fluctuating around at 130-190 miles). My MPG is drastically low, something like 15 MPG, and after resetting it seems to keep going back to, and hovering back and forth around 14-15.

Right now my plans are for bleeding (using a syringe to pull out the fluid) the brakes and clutch hydraulics asap. (Although the max temp. tomorrow is forecast at 16F :suprised;)... And while the wheels are off, the pad life should be visible (there is a soft grinding even with the old tires back on, but it disappears when applying the brakes... My hopes are that the pads are worn and it's the wear indicator that's been grinding?) BTW, is there a good way to check the inner pads without having to remove the calipers?

Cheers :)
 
#13 ·
After I posted, I thought for a minute, and ran this on powerdog:

Specification Sidewall Radius Diameter Circumference Revolutions Speedometer Odometer Difference 205/55-15 4.4" 11.9" 23.9" 75.0" 845/mi 60MPH 10000mi N/A 205/65-15 5.2" 12.7" 25.5" 80.1" 791/mi 56MPH 9367mi 6.8% 195/65-15 5.0" 12.5" 25.0" 78.5" 807/mi 57MPH 9559mi 4.6%

WIS says rim offset should be:49 mm

So it appears that the tires you have on there (205/55) are outside of the recommended sizing by a good deal.

So please check the rim size and offset.
 
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