Driving Characteristics After Changes

[Track Junky]

Most you guys know that recently I have made a few changes on my car. I have been going back and forth with Blake on this but I decided to start a thread to see if anyone else has similar feeling in the driveability of your cars.

My car ran 17x9.5 torque thrusts with 275 R888's all around. Car drove great and was very predictable.

I added 17x9.5 and 18x10.5 vette wheels. 275's up front with 2" hubcentric spacer, 315's out back with 1 1/2"" hubcentric spacer. I also installed a Fays 2 watts link.

Now when I jump on the throttle from a 30 mph roll the car dips in the passenger side rear and veers to the left.

Anybody else getting this with larger 100 tread wear tires in the rear?

[Mean 69]

You made two changes simultaneously, so why do you think that the tires are the issue, and not the addition of the Watt's?

[70rs]

I'm only taking a shot in the dark here, but did ANY rear geometry change with the addition of the watts link? Was the rear centered before the tire swap?
Maybe there was already some kind of issue that the watts link or wider tires is magnifying?
All else being equal, a tire change alone shouldn't CAUSE a problem should it?

[Track Junky]

You made two changes simultaneously, so why do you think that the tires are the issue, and not the addition of the Watt's?

I'm not discounting the watts. I would like to know if anybody else's car has similar characteristics though.

I'm only taking a shot in the dark here, but did ANY rear geometry change with the addition of the watts link? Was the rear centered before the tire swap?
Maybe there was already some kind of issue that the watts link or wider tires is magnifying?
All else being equal, a tire change alone shouldn't CAUSE a problem should it?

Good point. Rear is centered but we did bring the top of the shocks inboard just outside the frame rails and the bottom of the shocks are still in stock location.

I dont think there was a previous problem and the car felt great before the changes aside from being a bit loose in the rear and the differential shifting from side to side in the corners hence the watts and wider tires.

[70rs]

A mystery.....
Heres a thought, if you have a GoPro camera, mount it under the rear of the body. Try to get as much suspension as you can in the cameras field of view. Take it for a spin, make it present the handling problem, review the footage and see whats moving around on you.
Are you running leaf springs? Maybe the mount point at the front of the spring or link on that side is loose or worn (bad bushings?)
It doesn't take much movement to cause a noticable diff in handlng.

[69sponge]

Try putting the TT2s back on to eliminate the diffrent rim and tire combo.

[Track Junky]

A mystery.....
Heres a thought, if you have a GoPro camera, mount it under the rear of the body. Try to get as much suspension as you can in the cameras field of view. Take it for a spin, make it present the handling problem, review the footage and see whats moving around on you.
Are you running leaf springs? Maybe the mount point at the front of the spring or link on that side is loose or worn (bad bushings?)
It doesn't take much movement to cause a noticable diff in handlng.

The camera thing is a good idea. I have a GoPro so I will see if I can make this happen. It does have Global West leaf springs.


Try putting the TT2s back on to eliminate the diffrent rim and tire combo.

Good idea. I will probably try that after the adjustment phase has been exhausted.

Do you guy's think their might be an issue with my posi unit? It's been in for 9 years.

[70rs]

Wider tire getting better traction could be pulling it to one side, but I would think only if the differential and suspension were moving around. Double check all of your mounting oints and suspension bushings. Try the camera deal and see what comes up.
At least that way you don't go buying new parts guessing at whats wrong.

[wmhjr]

What tires are on the new combo? Are they also R888s?

I agree - put the TT2s and original rubber back on and test first. Do that BEFORE any other adjustments.

[Track Junky]

What tires are on the new combo? Are they also R888s?

I agree - put the TT2s and original rubber back on and test first. Do that BEFORE any other adjustments.

Yeah, all R888's. Makes perfect sense. I've got a buddy coming up to help, hopefully he hasn't left his house yet and I can get him to pull his tires and wheels off of his car.

[Track Junky]

Wider tire getting better traction could be pulling it to one side, but I would think only if the differential and suspension were moving around. Double check all of your mounting oints and suspension bushings. Try the camera deal and see what comes up.
At least that way you don't go buying new parts guessing at whats wrong.

I'm heading down to the garage now. I'll see if I could find a spot to mount the GoPro.

[70rs]

Now you have me very curious what it could be. Please keep us posted on what you find out.

As the other guys said, try swapping the old tire & wheel package back on. That eliminates one possibility. Try the GoPro with both sets. Maybe you'll see a difference.

Good luck!:thumbsup:

[Mean 69]

Just take one of the Watt's link bars off (don't even need to take off the other, but probably good so it doesn't get lodged somewhere). My bet is on Watt's influence rather than tire.

[Track Junky]

I'm waiting for my buddy to show up with his wheels. In the mean time, if you guys never saw my previous thread on the Fays 2 watts link install, here are some pics to give you an idea of what it looks like.

I also went through my GoPro stuff and I dont have a suction mount but am going to try and figure something out.

http://i851.photobucket.com/albums/ab73/Gitter_Dun/Watts%20Link/WattsLink101.jpg
http://i851.photobucket.com/albums/ab73/Gitter_Dun/Watts%20Link/WattsLink100.jpg
http://i851.photobucket.com/albums/ab73/Gitter_Dun/Watts%20Link/WattsLink099.jpg
http://i851.photobucket.com/albums/ab73/Gitter_Dun/Watts%20Link/WattsLink098.jpg
http://i851.photobucket.com/albums/ab73/Gitter_Dun/Watts%20Link/WattsLink097.jpg
http://i851.photobucket.com/albums/ab73/Gitter_Dun/Watts%20Link/WattsLink096.jpg

[JKnight]

Are the lengths of your Watt's bars exactly the same? I would tend to agree with Mark that the watt's is likely to be creating the symptom you're describing. Although, that said, I would tend to agree with Mark on all things suspension related....

[Track Junky]

Are the lengths of your Watt's bars exactly the same? I would tend to agree with Mark that the watt's is likely to be creating the symptom you're describing. Although, that said, I would tend to agree with Mark on all things suspension related....

Yes, bars are equal length.

I strapped the Gopro underneath and got some vid but it doesn't say much about the watts. it is still uploading into photo bucket and I will post it later.

What I did though was take 2 clicks out of the shocks and when I stomped on it, it was fine. Could be because the tires might have been a bit cold so I will be trying it again but that will wait till tommorrow.

I'm thinking the posi is about ready to go because it seems I'm getting more passenger side wheel spin.

Next track day is in September so i think that will be the best time to get some watts footage.

[Silver69Camaro]

I'm with Mark. Without the watt's link, the leaf springs were determining the roll center. Now, with a Watts, you are in control of where the RC is. Did you match the watts pivot location to the leaf's RC location? If not, you have two competing RCs that will usually cause some goofy handling issues.

But it sounds like you got it figured out anyway.

[Track Junky]

I'm with Mark. Without the watt's link, the leaf springs were determining the roll center. Now, with a Watts, you are in control of where the RC is. Did you match the watts pivot location to the leaf's RC location? If not, you have two competing RCs that will usually cause some goofy handling issues.

But it sounds like you got it figured out anyway.

I agree. I'll have to figure that out on the track though because I dont like screwing around on the street.

Shock tuning did cure the car from pulling to one side but once I get to the track I will be spending more time with tuning with the watts.

Once I cured the pulling to one side I had to work on an issue I was having with the front left wheel. The Vette wheels changed the scrub radius and also created a wiggle/vibration at the front left wheel. Probably due to the center ring of the wheel being on the outside now. Also, turn in is way, way, faster.

I checked everything two, three and four times. Ball joints going bad? Tie rod going bad? Thought tie rod so ordered one last night, but today I was looking at the alignment and it looked like the front left wheel had to much positive toe. Took an 1/8" out and it changed every thing.

Car is ready to rock and roll now. Thank God!! It was bugging the hell out of me!!

All I have left to do before Buttonwillow is get the new gas gauge reading fixed. Ran out of gas while I was trying to figure everything out and the wife had to come to the rescue. Wouldn't be the first time, lol.

[Track Junky]

So I went on line to figure out how to find leaf spring roll center. Dropped the watts link pivot 2" to match leaf springs and it made a huge difference.

Through new lower Global West control arms in(from original stamped steel ones) and the urethane base that came with the new lower control arms raised the front of the car about an inch and a quarter.

Took the car to Thunderhill and the rear felt great but the front felt like it was working very hard. I think it may have to do with the Z06 wheels and 2" spacers putting more pressure on the spindle, hub and bearings, but it also could have been raised ride height.

Recently chopped the front springs to where normal car ride height up front was(23" from floor to fender lip) and then took one of my CHP buddies out for a ride.

Definitely feels better up front in the corners but then again I was on public roadway and dont like screwing around in that environment so speeds were limited.

Going to try and make Thunderhill on May 7th but my wife will be out of town so I will need to find one of the neighbors to watch the kids.

Trying to set up for Buttonwillow on September 17th and 18th so hopefully I will get one more opportunity to get a track day before then.

Meanwhile, I tried to upload video of my rear suspension but cut it short because I didn't have the patience to wait for a 3 hour upload.

[70rs]

Oh man! I am sadly dissapointed you did not sit through a 3 hour upload for my benefit.
:D
I am just kidding you. I don't blame you at all.

Have you tried running your old wheel package since you installed the W-link?

I would think it's easier to "re tune" the chassis after a single change, not multiple.
Or, just try the old fronts to see if the spacers really are the problem. Having all of that load moved out from the steering "pivot point" will make it feel different.

You put the wieght of the tire and wheel out on the end of a huge lever. The contact patch on the tire is now further away from the pivot point of the spindle.

I know what I am trying to say here. I apologize for not being able to make it clear. I am even confusing myself........lol!

[Track Junky]

You put the wieght of the tire and wheel out on the end of a huge lever. The contact patch on the tire is now further away from the pivot point of the spindle.

Exactly!! Next track day I am going to bring the Torque Thrusts with me to see if I could feel the difference.

The rear Fays 2 Watts set up felt great and the differential never moved from side to side. If it did I would have seen it due to having about 1/4" to the quarter panel and 1/2" to the leaf springs.