For the Suspension Guru's ... steering wheel shake (not as simple as it seems)

[AL91GTR]

I know, this seems simple enough but I've been chasing a steering wheel shake for around 2 years now with limited success. My tires have around 5k on them, wheels have been checked for true and I had my front tires re-balanced with the road-force machine.

Last winter I had the steering rack rebuilt, replaced CV boots (4 front), inner and outer ball joints and rear Hicas ball joints. New poly bushings and bar links front and rear and just recently popped in some new coilovers. Also using AMS fuca's, ruca's and T-Rods. The shake was there before and still there after.

Right around 95 - 110 km/h I have noticeable and annoying shake in the steering wheel. When driving slower, sometimes the front end almost feels 'loose' after hitting a larger pothole or bump.

Nissan had no trouble doing an alignment on it and said everything underneath appeared to be mint.

I really don't want to throw any more parts at this but I'm putting a stash together for winter building and need to get this issue sorted before upping the power any more.

Wheel bearings? Rotor? Tie-rod ends (they feel pretty good).

I had something similar in my old Z31 and it turned out to be an out of balance driveshaft but that wouldn't explain the loose feeling. Could it be one of the front drive shafts out of balance?

Anybody else have a similar issue with their BNR32?

Thanks!

Al

[bobbo]

This always happens at that speed? What happens under braking?

[AL91GTR]

I haven't really noticed any major brake shake but always around the same speed.

One thing to note that the shake is worse when driving straight and gets considerably less when cornering at highway speeds.

I borrowed a very fine dial gauge from my dad (marine engineer) so we will check out all rotors and wheels to see if something has been missed previously.

[caliber676]

Tie rods and wheel bearings are possibilities. Make sure you check all your bushings. Check your steering column dampener. I know you road forced and balanced wheels but from experience even a road force balancer can't pick up tread seperation or other tire anomolies. Best to swap wheels with another set and see just to rule it out and avoid costly guessing.

[Skym]

Wheelbearings can be checked by jacking up front of car and grabbing top and bottom of wheel and see if there is any play. Do the same with hands on left, right side of wheel. That's how they check wheelbearings, steering with inspections.

I agree with tyres, they actually have an expiration date and can get bumps in the tire, flat spots which the balancing machine can't pickup on.

If have HICAS, check HICAS ECU (water can enter the breather holes on top from a leaking rear window or boot / trunk lid and stuff the HICAS ECU), as it can throw an eppy when in diagnostic mode.

Front half shaft's can have play on wheel side (where they usually fail). Also check G sensor, speedo cable (ECU's on the car can do weird things when speedo cable is loose behind dash).

[Bossman]

Does it shake beyond 110 km or just between 85-110?

[h4X6]

are you running spacers at all? if they are not the proper spacer then they could be throwing everything out... also if you are running wheels, maybe some hubcentric rings might help...

[caliber676]

Just to note, if your wheel bearings are gone to the point of steering shake you will almost definitely have a terrible noise associated with it. Honestly, try swapping wheels with someone for a drive. Back in my apprentice/tire days, id say every month we'd get back at least a couple wheel shimmy related concerns due to the tires, and they were top end high performance tires that would cost upwards of $800 a tire. Unless suspension checks show noticeable signs which can be checked in a matter of minutes, swap the wheels before proceeding is what I would stress

[AL91GTR]

Okay, some more data from today. I went out for a drive and clocked miles at 90, 100, 110, 120, 130, 140 straight and on some nice curves. Tonight I removed all 4 wheels and rotated front to back and corner height balanced to within 0.5 mm at all four corners. I checked everything over. I have a/m wheels and hubcentric rings so not worried there.

Wheel shake starts around 95 -100 and continues most noticeably to around 125. Then it is still there lightly to around 140 +/-. In the curves it all but disappears at all speeds.

No wheel bearing noise at all and they check out fine when wheels off the ground. Rotors seem fine also. The steering is tight and even a slight move to one wheel transfers to the other one with no play that I can feel at all.

Tires were replaced by me around 2 years ago to replace some old Ruined Falken's and the shake is basically identical to what it was like before so I think it is suspension related. They are Hankook V12 Evo's

Nothing appears to be bent or twisted (no flaked paint, new paint, wrinkles, signs of repairs, etc...) in the front suspension, crossmember or anything else underneath.

Hicas computer codes came back clean last fall but it has given me the ass end kick on the highway twice this summer so maybe something is going on there ?

The Only thing I did find that may explain is that when I grabbed the front half shafts between the boots you could slide the shaft in and out maybe 1/8" on either side. I figured this is normal to account for some movement when the wheels turn but maybe I'm wrong ? This might explain why it disappears in the corners.

I'll see if my tire rotation has had any affect tomorrow ...

EDIT: need to check out my steering damper too - might explain the cornering thing ...

[Bossman]

That's excellent info you came back. Since you have the same problem with the new tires I would rule that out but you can double check with a tire rotation. When you grabbed the drive shaft see if there's play up and down, what I think is blown cv joints. You mentioned you had the boots replaced last years, were the old one broken?

[Skym]

HICAS rack can have play on inner and outer ball joints. If out ball joint fails, so does inner ball on HICAS rack. HICAS works in the corners above a certain speed.

There might be slight movement in the front halfshaft's because engine moves around on rubber engine mounts and half shaft's are connected to the diffhead that's part of the sump.

[AL91GTR]

Thanks for the replies guys.

Skym, are you suggesting that a bit of play in front half shafts is normal - I would think it needs to have some amount of play so nothing breaks. I had one inner torn boot last year but the CV appeared to be fine. I cleaned all, re-greased and put on 4 new boots.

Think a failing HICAS rack would cause steering wheel shake? Seems reasonable to think so if it is loose and floating around on the straights and then loads up on corners and tightens. I did replace the rear HICAS joints last year and one was pretty messed up (the other not a whole lot beter).

Last night I was out for a rip and have noticed this same situation three times now: After a full throttle run up to say 140 +/- after letting off the gas the rear end kicked like the hicas twitch. I don't want to just rip out the hicas and lock it up but it seems like something is starting to get a little worn out back there.

Only 125,000 km on the odo but it is 23 years old so seems likely that things are just gettign worn out.

[Skym]

You're welcome.

HICAS ECU can do weird things (sometimes has bad solders or water gets into breather holes on the top of HICAS ECU casing, water marks give it away) and you said the problem occurs with speed. HICAS ECU uses speed input to adjust rear wheel angle, powersteering weight.

Also 4wd ECU uses speed input, so it could be another cause.

Usually the speedo cable causes problems on R32's, as my car started doing weird things when the speedo cable was faulty.

If twist the middle of half shaft by hand (usually use a machine to check it) and feel alot of movement, then it needs to be rebuilt or replaced. Replacing shaft's, bushes is part of routine maintenance on Skylines.

Can buy a Tomei HICAS Lock kit that locks HICAS at the rack, electronically (earths some wires).

HICAS is there to prevent understeer on 90 degree+ corners. You don't realise it until you try to take 90 degree+ corner without HICAS and the car doesn't want to turn in (factory suspension). It's a interesting experience.

[AL91GTR]

Some closure:

I 'may' have found the source of my steering wheel shake. I had a worn out FUCA bushing a few years ago (wheel shake then too) and so instead of changing the bushes i put on some adjustable AMS ones and called it a day. My steering wheel shake was pretty much the same so I figured it must be something else. The other night i noticed some scuffs/scratches on one of the locking collars and then found they weren't all that tight and that one of the lock rings had definately moved from it's original position.

I re-aligned the locking collars for clearance and tightened them down and the front end is much more solid and the steering wheel shake seems lighter.

Having said that, my HICAS is definately acting up and getting worse ... I'm going to do total elimination kit and ditch the 23 year old system, ecu, everything over the winter. Will also most likely press some new bushings into the stock upper arms while i'm at it.

BTW, anybody want to buy some AMS adjustable FUCA's haha?

[Cuami]

S14 non-hicas rear subframe swap?