Q45 Steering Wheel Vibration

[emcnack]

My '90 Q45 has 178k miles. The car's been well maintained.

About 3 months ago, noticeable vibration (steering wheel shimmy and foot well vibration) began at any speed above 55 mph.

I did the usual things: 4-wheel alignments, tire rotation, static and dynamic balance. No change.

I've since purchased new tires (Dunlops), wheels, rotors (Brembos) and pads. No change.

Any suggestions.

Note: There's one other thing that started around the time the vibration began and that's a noticeable drift to the right on most roads due to out of spec caster.

The driveshaft, motor mounts and transmission mounts were replaced about 15 months ago.

[szh]

If you have checked everything else, it might be the steering rack.

Z

[Q45tech]

Brake rotors. Loose suspension steering parts. There should be NO play in steering, a sensitive touch driver should feel each side of the pinion engagement.....taking no more than 1/2" in total.Upper links, tension rods, kingpin bearings, tie rod [both inner and outer.

A proper tire should require no more than 7-10 grams per side of wheel-----------no more than 15 grams total balance weight per wheel.

Do tires have any heel/toe feathering?

[emcnack]

Local Infiniti dealer checked out the car yesterday. Found no worn or loose suspension parts.

Suspects the wheels aren't balanced. I find that hard to believe. The wheels have been balanced (static and road force) a couple of times in the last month. As I mentioned, the tires and wheels are low mileage (< 1,500 miles) and good quality.

Has the dealer taken the easy way out?

Could the front rotors cause the steering wheel vibration I'm feeling above 60 mph? They were purchased new about 6 weeks ago. They're not OEM but Powerstops (the rotors on the rear are Brembos)?

I don't have the old rotors. How can you tell if the rotors are the problem?

[Q45tech]

When you installed new rotors were they indexed to oem new specs? 0.0028" or less runout........this is an extra cost proceedure........that usually shows bad wheel bearings or kingpin bearings, rust on hub.

Are the new wheels oem and hubcentric........how much radial force was displayed?

[ardvarkus]

Local Infiniti dealer checked out the car yesterday. Found no worn or loose suspension parts.

How may 1st Gen Qs did this mechanic work on?

How are the upper links? They can look just dandy, but be shot.

How many miles on your suspension? Unless it was completely rebuilt in the last 60k miles, it seems unreasonable to have 'no worn parts'....

[90Q45blue]

I remember Heath having a similar problem. The solution was replacing the U-joint on the steering rack, a much cheaper fix. Just a thought. But like my predecessors said, get that suspension and brakes looked at.

Nick

[emcnack]

After I bought the car, over a 12 month span of time, I had the suspension rebuilt. The upper links have been replaced. New struts, springs, tension rods, etc. All of that was completed less than 50k miles ago.

The car rides/steers like a new car (except for the aforementioned vibration/steering wheel wobble).

I don't think the new rotors were indexed to OEM specs as suggested by the Q45tech.

I'm not a mechanic, so pardon the naivete of my question, but if the new rotors weren't indexed when installed, why would I get the vibration/wobble that I mentioned even though I'm not applying the brakes?

Is indexing the same as having the rotors turned or is it something different?

[maxnix]

50K miles is plenty of mileage and time for the wear and tear to degrade those components. Did you replace all the rubber when you mounted the new shocks?

Indexing refers to the mounting fo the rotors so they meet or exceed OEM runout. That is not the same as turning them, although when turned on the car, the cumulative non-wear factors that cause them to be out of specification are mitigated.

Try a search on index or indexing for a full discussion.

Rotational masses interact and can contribute different harmonic components to any vibrational problem.