Brake pull after new front shocks, rear rotors and tire rotation

Tiny
HADLEY WESTVILLE
  • MEMBER
  • 2007 SAAB 9-7X
  • 5.3L
  • V8
  • AWD
  • AUTOMATIC
  • 212,000 MILES
Requested dealer to replace front shocks with OEM Bilsteins (front suspension is a strut comprised of various GM parts permitting specific parts to be replaced vs entire assembly). Had mentioned shudder upon braking as well. Chevrolet dealer replaced shocks and related wear items, replaced rear rotors and rotated tires. Noticeable right pull when brakes applied, returned to dealer today after a four hundred mile trip. They cleaned the slides). Brakes still pull right and seem inadequate compared to two recent loaner vehicles. Could the vehicle need an alignment after the shocks were replaced? I get 80,000 miles from a set of tires so it holds an alignment. Thank you.
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Monday, July 3rd, 2017 AT 6:20 PM

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Tiny
CARADIODOC
  • EXPERT
Your front struts are of an uncommon design that does not incorporate the "camber" alignment adjustment. Assuming neither old strut was bent, replacing them will not change the camber setting. Camber refers to the wheel tipped in or out on top as viewed from in front of the car. Camber also has the biggest affect on pulling to one side. Tires want to roll in the direction they are leaning.

One thing to consider is your springs sit on a rubber isolator on the strut's mounting plate. That part is about half an thick. There is usually no way to easily tell if the metal frame inside it is rusted away until the assembly is taken apart to replace the strut. Then, once it is apart, the rubber crumbles and can't be reused. The problem I ran into when working at the dealership was they didn't stock that part because the sales history showed "0". Why stock a part no one buys? Now that I am sitting there with the assembly in pieces, I am not going to put it all back together and tell the customer they have to come back once the parts come in. Instead, everything can be reassembled without reusing those isolators. Once I convinced the people in the parts department to stock a pair of those isoators, they were able to sell them when they were needed, then the sales history showed those sales, so they kept them in stock.

Your dealer might have the same problem, or the mechanic may have reused the old isolators that were badly deteriorated. That could leave one front corner of the car sitting lower than the other side. The first thing you can do is measure both sides to see if the car is leaning. After that, every tire and alignment shop has a book that lists the ride height specifications for every year and model, and where those measurements must be taken. We get pretty excited when the car is in for an alignment and ride height is not at specs. We can make the numbers look perfect on the alignment computer, but that only applies to a car that is standing still, not one that is bouncing up and down while going down the road.

The more common cause of a brake pull is a tire pull. An easy way to identify that on a front-wheel-drive car is the pull will be to one side under moderate-to-hard acceleration, and the other way when braking. On rear-wheel-drive cars, the fastest way to identify this is to switch the two left tires front to rear, then drive the car to see if the pull changed. If it did not, switch the two right tires. I have had a lot of tires that caused a pull. I have never been one to rotate my tires, so I just put the pulling tire on the rear, and leave it there.

Worn and sloppy control arm bushings allow the alignment to change between braking and cruising. That is a real common cause today of a brake pull. Those bushings used to last the life of the car, but they are made of softer rubber now, so they can be expected to fall apart. I doubt that is the cause for your problem since this appears to have started right after the other service work.

After the tire pull, the next best suspect is the new rotors. There is a whole different problem related to rotors that are machined to different thicknesses, but with new rotors, that is not a concern. What you should be aware of though is you never mentioned anything about the break-in period. That is the job of the service writer to explain what to do and what to expect. It can take a good one hundred miles to wear the pads to match the microscopic grooves in the rotors, and four hundred miles of highway driving is not going to do that. Until the pads are seated, braking power is going to be seriously reduced, as you observed. That can easily be bad enough that you need to push so hard on the brake pedal that the linings overheat and you get one scary form of brake fade. The pedal is high and solid, but the car keeps going. The proper fix for that is to let the car sit for an hour for the linings to cool down, then drive it like normal.

I prefer to machine old rotors rather than replace them to avoid a common problem of the new ones warping. The majority of new rotors are made in China. There is nothing wrong with their quality, but when we make parts fro cast iron, we set them aside for ninety days to "age" before they get their final machining. The Chinese cast them, machine them, pack them, and ship them, then they age on your car. It is real common for them to warp and cause a pedal pulsation. If a customer demands replacements under warranty, the same thing will happen in about three months. The better solution is to take a light cut on those rotors, then put them back on the car. At that point they are done warping and the problem won't occur again.

The problem today is replacement rotors are so incredibly inexpensive, it costs the repair shop more in labor and equipment maintenance to machine old rotors, and therefore it costs the customer more. It is cheaper to just replace them. The other problem is there is always a published legal minimum thickness a rotor can be machined to, and unlike a few decades ago, rotors today do not have much material that can be removed without exceeding that limit. Most mechanics do not want to risk wasting your time and money machining the old rotors, and then have to tell you they need to be replaced.

My recommendation is to drive the car for another one hundred miles to include plenty of stop-and-go city driving, then see that your normal braking power has returned. If the pull is still there, switch the tires around to see how that affects it.
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Monday, July 3rd, 2017 AT 8:50 PM
Tiny
HADLEY WESTVILLE
  • MEMBER
Thank you CARADIODOC! Great ideas and although this vehicle has had many parts replaced, some at my request based on my own research, a lot of the front end parts are original. You have given me excellent ideas and I will heed your advice and suggestions.
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Tuesday, July 4th, 2017 AT 2:33 AM
Tiny
CARADIODOC
  • EXPERT
Keep me informed of your progress.

I will be out of town at the Lola Old Car Show swap meet until Saturday night, so do not panic if I do not get back to you right away. Internet access is real poor there because over 100,000 people are trying to use it at night.
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Tuesday, July 4th, 2017 AT 6:04 PM
Tiny
HADLEY WESTVILLE
  • MEMBER
Hi, at long last they "discovered " the problem today - worn lower control arm bushings! Original parts so it's time. Kind of surprised the alignment shop didn't detect it before they aligned it but it doesn't matter - problem solved (well I should reserve judgment until I drive it. Thank you again!
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Friday, August 4th, 2017 AT 3:25 PM
Tiny
KEN
  • ADMIN
Good to hear, please use 2CarPros anytime we are here to help.

Cheers, Ken
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Sunday, August 6th, 2017 AT 8:34 PM

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