The old Magna has developed a new, and kinda frightening, problem. On HARD braking, from 100kmph to 60kmph or less, the car shakes violently. The steering wheel practically tries to shakes its self out of my hand(s). :eeek: In normal braking conditions its fine.

I'm taking it in to the local tyre and brake center, but wanted to get a feel for what the issue may be. If its a simple matter of a day on the tools I'd have a go at fixing it myself.

In recent history the car hasn't had any major bumps/knocks - nothing to bend anything up front. Its wheel balance and alignment was only 1500km ago - no reports back about any damaged parts or failing components. Though the issue may have been around prior to its last alignment... just not as bad. No modifications done to the suspension or brakes. Shocks/springs/bushes are all original to the best of my knowledge. Car has just cracked the 150,000km mark.

Tyres are good - even wear and holding pressure (38 to 40 psi). Cant feel anything through the brake pedal when it starts shaking itself up on re-entry. There are some knocks/clunks/rattles up front, but no more than a standard Magna. CV boots/joints/shafts all seem good - no leaks and no "clackity clackity" on turns. :hmm:

I did have the steering rack replaced a while ago... 10,000km more ago. But would assume the guys doing the alignment would've spotted it then if there were an issue in that area. Steering feels positive and smooth - no free play or delay.

My drivers side engine mount is looking a little shady, but generally intact.

Rear wheels/tyres/brakes in good condition also. Only odd thing might be that the drivers side rear seems to collect a lot of brake dust. More than the other three anyway.

Any ideas/pointers etc. much appreciated.

Have you driven through a puddle after using the brakes and warming them up, or braked all the way down a long hill, or braked hard recently? It sounds like the discs could be warped. I forgot which way is which, but I think its the front brakes are felt through the steering wheel and problems with the rear ones can be felt through the pedal.

Warped rotors. Get them replaced if very bad.

+1 for sounding like rotors are warped.... if they are warped, machine or replace.

To machine shouldn't be more then $50-60 per disk, make sure dont get ripped of.. Chances are if you never replaced your brake rotors is that they are too thin to machine so you will need new ones.

At 150,000 km the rotors should be fine to skim. I did mine (TS) at 240,000 km and they were fine, $50 for the pair. Use a torque wrench to do up the wheel nuts to the right torque, uneven wheel nut tension can warp rotors (IMHO). If the shimmy is still there after, look at steering components like tie rods, tie rod ends, ball joints, sloppy wheel bearings, play in cv joints, etc.

Check prices on Ebay for discs - my rears were $60 for the pair and fronts are under $100 a pair. This usually includes delivery. New discs avoid the problem of removing the discs and somehow getting them to a workshop, waiting for them to skim then and then re-fitting.

Groovy. I'll jack her up on the weekend, bust the wheels off and check the discs for run out and such, and go from there. Thanks for the help.

Rotors wouldn't have been my first stop actually. Front brakes where serviced early last year - rotors machined and new pads.

Might check for anything else obvious while I'm under there.

Use a torque wrench to do up the wheel nuts to the right torque, uneven wheel nut tension can warp rotors (IMHO).

Has a tyre shop done them all up with a rattle gun recently? Could contribute to rotors warping.

Has a tyre shop done them all up with a rattle gun recently? Could contribute to rotors warping.

Good point. I'll check them tomorrow, and let the tyre place know.

I did take it for a drive tonight. This problem is only from higher speeds and hard braking. In every other way its a normal "non vibrating" car. At sub 100kmph speeds, regardless of the road surface and degree of braking applied, it wont shake up. At 100kmph, or over, sinking the boot into the brakes turns my car into a cheesy vibrating hotel bed. Same speed and firm braking = fine.

Anyway, its wheels of tomorrow after work for a look at the rotors and all the connecting parts.

My Ralliart does this, i'm just too lazy to machine them despite the machining... Machine standing roughly 10m from where i generally work all day.

Check how thick the rotors are before you take them off. If they're thin, just grab new ones and chuck them on yourself.

I think I just fixed it. I HOPE I just fixed it anyway.

Simple fix I think. Had the wheels off, couldnt spot any run out in the rotor or the disc surface. All of the tie rods, bearings, steering rack seemed to be bolted down and free of movement.

All I did was wire brush the surfaces where the wheel mounts - the rotor face (not the actual disc surface) and the inside of the wheel where it meets the rotor face. Then, I torqued the wheel nuts down to 75ftlbs.

Test drive so far tells me its fixed, or at the very least barely noticeable. Bearing in mind I haven't pushed the car far enough past 100kmph to really test it. The four of five emergency stops I did to (from 100-110kmph down to 50kmph) were vibration free.

Still needs a little further testing of course. Going to go do the rear wheels the same now.

You can only accurately check for disc runout with the wheels still on.....this is because the wheel nuts clamp the disc to the hub....remove the wheel and it's all free to move. You can also use spacers and the wheel nuts to clamp the disc to the hub, but it's better with the wheels mounted IMHO. Same with checking for wear in steering components - leaving the wheel on allows you to use more leverage on components.