I posted originally in the brake section but turns out it may be suspension related?

I have a pulse during braking at certain speeds. Its not really noticeable around town only on the highway. Limited research suggests that its not warped rotors but potentially worn lower control arm bushings. Its more noticable through the steering wheel with only slight pulsing through the brake pedal.

Car is a 2003 MCS with 75,000 miles. The LCA bushings were replaced under warranty at about 41,000 miles in 2007.

New rotors (Napa Ultrapremium) with Carbotech bobcats were put on at 60,100 miles in October of 2008.

Car has original struts/springs. Where should I begin trouble shooting? Rotors first or Lower control arm bushings? Should the car be getting new struts as routine maintenance for an 8 year old Mini?

An interesting observation was during some really spirited driving last week with some hard braking the pulsation got much worse and then back to normal after cooling off.

Thanks,
Kenny
__________________

2003 MCS - 15% pulley, DDM Intake, M7 strut re-inforcement plates, H-sport competition rear sway bar, 17" Team Dynamics Motorsport wheels

 

I would say it's likely a combination of brakes and suspension, lca bushings will help, but if the rotors and pads are 3 years old I'd say they're likely part of the problem.

If the "pulsing" isn't ABS then it's got to originate in the brakes themselves, blown out lca bushings alone wouldn't cause pulsing, just make it more pronounced.

Also as brakes heat up they should be laying down new transfer onto the rotors, sounds like there is uneven transfer to the rotor or the pad compound is going bad due to age or heat cycling life or whatever...

New struts are a good idea.

 

If it is the bushing, it's fairly normal. It's especially prominent on Honda Civics who's bushing are made of this bad grade rubber. The best bet would be go to a local mechanic, explain the problem to him, and have him give you a qualified guess.

To me, it sounds like warped rotors. The faster you go and the hotter they get, the more the pedal with pulse. You can warp your rotors easily if you get a car wash after driving a lot. If your brakes are really hot and you spray them with cold water, they'll warp pretty quickly.

 

Vented rotors don't warp, they get uneven pad transfer...

The idea or rotors warping comes from solid rotors(like our rears), but any decent quality even solid rotor, won't warp, it only feels like it due to some glazing or part of it has pad material baked onto it... When I ran a more metallic pad I could heat them up and slam on the brakes at speed and literally resurface the rotors, any vibration was gone...

 

My pads are barely worn. They have a lot of thickness to them. I may first by a set of new front rotors and see if that helps.

How can you tell if there is excessive movement in the LCA bushing? I jacked the car up and put a crow bar between the subframe and control arm but did not get a lot of movement. Tring to shake the wheel back and forth gets nothing.

 

Ugh. I must have fallen asleep. There were no responses when I started typing.

I'm no expert, but I think what you describe could be due to one (or more) of several different things. In general, I'd be looking for something worn or loose that could produce a vibration through both the steering wheel and the brake pedal.

First, I'd check that the front rotors are smooth, with no uneven deposits from the brake pads. Given the info you supplied, that's not my #1 suspect, but that was the culprit once with my car on track, and it's fairly easy to check.

Second, a tire badly/unevenly worn or out of balance can also produce vibrations felt through the steering wheel and brake pedal.

Third, any of several suspension components could produce the vibrations you describe if they're badly worn; that certainly includes the bushings you mentioned. Once solidly connected parts produce more free play as they wear. You can do an initial check for worn bushings fairly easily.

If you haven't found the culprit yet, you probably need to remove the wheel(s) to continue looking for sources of vibration (something worn or loose) that might reasonably be felt through both the steering wheel and the brake pedal. Check brake calipers and pads, control arms, etc.

I think I'm about at the limits of my non-expertise now, if not somewhat beyond. If I hadn't found anything by this time, I'd just hand it over to the same expert who'd be fixing it anyway.

 

I've seen this before from NAPA rotors. I'd start there.

 

Way,

What rotors do you recommend other than OEM?

I sent you an email a while ago. I will
Be up in Indy another time this summer. Any chance to
Coordinate for you to do some work on the car? I'll do new rotors first but I am sure bushings and suspension work would be good on an 03


Kenny

 

New Zimmerman rotors fixed the problem. Easy fix for $150 shipped on all for rotors. The braking feel is also much improved. I would have never thought a rotor would effect braking feel but it definitely did.

 

Good outcome, and thanks for providing an update.

 

Yes it is amazing. It just shows why there is such a price difference, but totally worth the extra for the zimmermans.