Brake / Suspension issues
 

Hey guys

I have a problem with my car where braking at speeds above 90km/h (55 mph) in a straight line causes the car to dive to one side and become unstable, and it will begin to fishtail (with no steering input, VDC on).

In general the car doesn't feel planted at all at any speed, but is very floaty and unstable at speeds over 90 (55mph) of late. The car has stock suspension, 38, 000kms, 2011 model. I've done basic things, checking wheel nuts are torqued correctly, pressures all set to 38PSI.

I have new(ish) tyres (2 months old on the rear and 5 months old on the front, with 2000km driven this year on the fronts) and newish brake pads (4 months old, Project Mu NS400) on the car.

So I'm not sure if it's a general suspension problem, alignment, joints or a combination of those. What should I be looking at/for under the car this weekend (Mechanical noob)?

Blown shock would leak fluid. Hard to imagine it would have visible damage unless you collided something and straight up smashed the car.

Pulling to one side during braking could be alignment or brakes. Alignment will require a shop. You said the tires look good at all 4 corners?

Its also possible that a fitting or a line has broken at one corner of your brakes. Look for anything obviously hanging off the car (unlikely, unless direct impact or poor work by prior mechanic). Also bleed the brakes and see if there's any issues at one corner.

38k km doesn't seem like enough miles to just be mere wear on a suspension arm or joint

First thing I check would be alignment, guessing Toe angle.

I was going to guess blown damper/s too but your car has very little miles.

Do you have the same model tire on the front and rear? The first thing I would do is bleed the front brakes.

Check the toe. Toe out in the front can cause the car to be very darty under braking.

I would say Alignment as well. If it always darts the same direction, those new brake pads in the front could be grabbing harder towards the pull, than on the side opposite the pull. If that would be the case, it's more than likely just a case of improper lubrication. Regreasing everything would solve that, if that were the case anyway. I'd definitely go with alignment first thought.

Agree with all you guys. My thinking on order of likelyhood...

1) Alignment (Check tire wear. Should still be those little nubbies on the tire if its only a week or two old) They wear off first so it can be a good indicator for alignment)
2) Ball Joints (Lift front, push/pull wheels really hard at 3 & 9 o-clock, should be zero play at the ball joints)
3) Shocks (does car bounce more than once after a bump?)
4) Brakes (tear down and rebuild) http://www.the370z.com/diy-section-d...build-f-r.html
5) Wheel bearings (Lift front, push/pull wheels really hard at 12 & 6 o-clock, should be very little to no play)

Not much left after that...

38k km = 23k miles

Man that would be insane for a shock to blow, bearing to go bad, or brake caliper to start leaking at such low mileage

but wait i think i heard a retailer tell me that australian Z's are completely different than those in the rest of the world

Sorry guys, damn timezones. Thank-you all very much for your responses.

I've booked the car in for alignment. A bit worrying since the toe was adjusted at the start of the year, and alignment was supposedly done after both sets of tyres were fitted.

Some answers:

- Don't have the same tyre model all round. Toyo T1's up front Kumho KU31's at the back. Not knowing a heap about tyres I didn't think it would matter too much.

- Turning the wheel lock to lock sometimes makes a bump noise towards 8-ish o-clock position, and I feel the car jolt occasionally. So ball joints might be shot?

- Car does bounce around a bit, but man it is really floaty. Will get shocks checked. Bump steer is atrocious

- Tire wear wise I see nothing obvious. Both sets are new, and I drive the car a total of 25k a day at most. Guessing the effects would take some time to be seen in that instance

Oh yeah, mismatched tires can cause issue big time. Different compounds, etc. Car will be darty for sure. Been there, done that and won't do it again.

Car drives straight until hitting the brakes. Then pulls to one side. Sounds like a stuck caliper piston. Which brakes do you have? Base or sport?

Australian model only comes in one trim. My quick research says it uses "Akebono" brakes. Not sure what equivalent that would be on a US trim model - Sport perhaps?

Are the front calipers 4 piston?

Yes, they are sport-brakes

For mine, I would get front AND rear alignment checked first and then calipers for seized piston BUT Adelaide where OP lives is warm/dry climate so not all that likely as the car is hardly been used .........

Yep, 4 piston

Booked the alignment for front and rear. It's going to be a process of elimination :tup: