Won't Turn Right?

[coop]

:ermm:Recently ran the car in Vintage at Laguna Seca and the thing wouldn't turn right. It just wanted to push straight off the track. This happens under light throttle application just after turning into the corner. The race before, the car was perfect. I've tried tightening everything and have found nothing wrong. Sway bars are snug. The alignment looks good too. I even tried rebuilding all four shock absorbers and the car still pushes in right hand turns. The thing is, the car turns left great. Now don't tell me to start running NASCAR, as that joke is getting very old.

Has anyone seen this behavior in a Z? I've been running a Z for over 20 years and have never come across this. Your thoughts?

Thanks, Coop

Edited May 3, 2009 by coop
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[Nigel1943]

You running a LSD?

[coop]

Yes, a Quaife.

[jmortensen]

Sway bar preload eliminated?

[preith]

Very weird! My immediate thought is the corner weights are off. Have you scaled it? I have heard of coil over spring perches loosening (and moving) on a few occasions, but I'm sure you would have found that. I find it very hard to beleive a suspension spring yielded but just throwing it out there... Maybe it's something as simple as a defective tire, perhaps try another set of skins?

I assume you haven't made any changes to the car since the last race, and no off course excursions either? Speaking from experience, I did make changes which affected weight bias and mistakenly did not scale the car as well... sure enough it went loose on left turns.

On a side note, you're running a Quaife without cooler? That baby must get toasty! Maybe it's a bad thing, ignorance is bliss, but I finally installed a temp gauge on mine (R200 w/Quaife) last season. I was in the last race session of the day (plenty cooled) and it still hit 290 with Amsoil severe gear racing lube too. A diff cooler went on after that, but I hear it's not legal in ITS.

Edited May 4, 2009 by preith

[coop]

It's weird alright. Corner weights are perfect as I scaled the car again when I got back home and again after changing the shocks(I always remove preload when corner weighing). At the track, I even corner jacked the car to get it to change behavior in both directions and went to a full soft rain setup. No mater what I did, same result, a bad push in right turns. This even occurred at Fernley during testing. I've had people turn the steering wheel while I'm under the thing and no notable slop.

Perhaps the rear end is taking some sort of toe change when the left rear is loaded? I also thought about the Quaife. Could it be acting up in only one direction and I can't feel it in the seat of my pants? It's only a set of gears since there are no clutches back there. Quaifes are supposed to be bullet proof. Also, I used to run a locker and that led to under steer only on slow corners. If the Quaife was locking up, the rear should be stepping out on fast corners just like my old locker and you think I'd feel it let go. Same result on multiple sets of tires with consistent tire pressures.

Possibilities?

-Crack in steering linkage/rack/coupler

-ball joints

-toe changing

-bad spring

-diff

-cracked frame or TC rod/mount - then why does the car brake in a straight line?

-sway bar failure

Maybe I should move everything on the left that is transferable and move it to the right or just replace everything. I sure wish there was a smoking gun here.

Do steering racks ever act up?

Edited May 4, 2009 by coop
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[jmortensen]

Sway bar preload eliminated?

[preith]

Perhaps the rear end is taking some sort of toe change when the left rear is loaded? I also thought about the Quaife. Could it be acting up in only one direction and I can't feel it in the seat of my pants? It's only a set of gears since there are no clutches back there. Quaifes are supposed to be bullet proof. Also, I used to run a locker and that led to under steer only on slow corners. If the Quaife was locking up, the rear should be stepping out on fast corners just like my old locker and you think I'd feel it let go. Same result on multiple sets of tires with consistent tire pressures.

Possibilities?

-Crack in steering linkage/rack/coupler

-ball joints

-toe changing

-bad spring

-diff

-cracked frame or TC rod/mount - then why does the car brake in a straight line?

-sway bar failure

Maybe I should move everything on the left that is transferable and move it to the right or just replace everything. I sure wish there was a smoking gun here.

Do steering racks ever act up?

The Quaife crossed my mind too but I'm with you, they're pretty much bullet proof. You could remove it and send to Quaife for inspection, but I'd think it would go open, not locked, if worn and of course not cause a push. I toasted a diff pretty good with the Quaife installed and it came out of the carnage completely intact.

I'd think any loose ball joints or tie rods would jump out at you.

A fellow club member has Wayne's old ITS Z (mountain motorsports) and I do recall him saying Wayne mentioned the rear uprights (the 1/8" plates) had a tendency to crack.

The swaybar mount captured nuts pulling out of the frame rails is a common problem too. Aside from that, I'm at a loss. Good luck and please keep us posted.

[jmortensen]

Swaybar mounts are going to affect the car turning either direction, just as adjusting an adjustable bar on one side only affects the car's response in either direction. The bar attaches to the suspension on both sides, so it shouldn't react differently in one direction or the other, unless it has some preload. Preloading the swaybar makes it act differently in one direction than the other. That's why I kept bringing it up. You did mention removing preload when corner-weighting and I missed it. How are you removing the preload? Shims? Heims jointed end links?

[coop]

To relieve the preload, I reach under the car while the suspension is fully settled on the scales. I loosen the adjustable slide that attaches to the bar just a little and only at one corner. Then I loosen the lock nut from the down rod at that same corner. I then turn the down rod bolt which is threaded into a heim joint. I turn the bolt back and forth until the slide starts to become real loose. At this point, there is no preload. I just tighten everything back up and I'm good to go. Any difference in preload that has been relieved can be measured on the scales.

Any way, the weird thing about all this is that the car was perfect the last time it raced and I haven't made a single change since then. Something has to be broken.

Also, the upper spring perch is in good shape as it was inspected when I replaced the shocks.

[jmortensen]

To relieve the preload, I reach under the car while the suspension is fully settled on the scales. I loosen the adjustable slide that attaches to the bar just a little and only at one corner. Then I loosen the lock nut from the down rod at that same corner. I then turn the down rod bolt which is threaded into a heim joint. I turn the bolt back and forth until the slide starts to become real loose. At this point, there is no preload. I just tighten everything back up and I'm good to go. Any difference in preload that has been relieved can be measured on the scales.

Who is sitting in the car? You need to sit in the car when you set corner weights (with the swaybars disconnected preferably) and then you need to have the preload removed with you in the driver's seat.

Any way, the weird thing about all this is that the car was perfect the last time it raced and I haven't made a single change since then. Something has to be broken.

Also, the upper spring perch is in good shape as it was inspected when I replaced the shocks.

That doesn't sound like preload, but what it could be is a bit of a mystery. You're sure your alignment didn't change? What kind of bushings?

[coop]

Well, this is an area where I've compromised over the years. I sit in the car when I do the corner weighing but I don't when I remove the preload. Yeah, I know, not as accurate as it could be. I should get 165Lbs of weight and place it in the seat while I do all the adjusting and measuring. That way the preload would be guaranteed to be zero. I like it though, good idea. Now, where can I find that much dead weight around the house? Might have to take a trip by the ex wife's house.

I use aluminum eccentric bushings all around. The left rear might be toeing in as trail braking ends and power is applied. I'll be checking that soon. Sounds too easy! Static toe looks good, however. Again, there may be a broken mount, etc.

What about a problem in the steering rack?