Worth the wait

Having an issue I have never encountered before...

Decided it was time to throw my 19" forged rims back on the beast.
I bought a set of slightly used Michelin PSS tires form a local member here.

On the first drive I had a VERY noticeable pull to the left under heavy acceleration. Once I jump off the gas the car "floats" back on track.

It honestly feels like the car is on ice! Punch the gas, darts left, lift off the gas, floats back in line straight. It is very disconcerting/scary.

I took the wheels/tires to a reputable shop by my house (Curry's) and had them mounted and road force balanced. Bought brand new conical seat lug bolts from RAD. The wheels were mounted and the lugs were torqued to spec by hand.
The car was aligned about a month ago, and I never noticed this trait with the 18" Conti DWS's.

Anybody have any thoughts as to what might be the issue?????

Thanks!

Brian

GregMB

Supposedly the toe changes under hard acceleration with these cars can make it feel unstable. Factory toe links have rubber ends (IIRC) and the aftermarket stuff replaces them with monoballs (heims).

Obviously this doesn't explain anything if you never experienced the issue before... unless maybe your old tires were so rock-hard that they would never hook in the first place.

I was enjoying some wet pavement driving over the weekend, and did some 30MPH bursts. The rear tires (PSS's) would break loose and spin but I was also getting quite a bit of wheelhop which I think is also toe-in/toe-out related.

Subscribed to see what you end up finding out.


-G

Worth the wait

Thanks for the info, that helps.

Yes it may just be the change in tires, as the DSW are a hard, all season tire. I have experienced somewhat similar issues on other cars when upgrading tires/wheels, but nothing like this.

In fairness the issue is most prevelant on the highway when I pull hard in third...so there is over 550 ft lbs of torque to deal with at that point.

Do you guys think this might be exageratted by an improper alignment and if I get it re-aligned it will be minimized?

Who would have thought a vastly better and bigger tire would cause poor handling in any aspect of preformance....weird

cij911

Actually bigger is not always better....the fact that it is pulling under acceleration and you installed new rims and used tires, would lead me to believe it is tire related....

Are you sure the rims and tires are perfectly true ? How about tire pressure - if the left tire is slightly lower in pressure, your car will pull under acceleration.

What happens when you brake hard (with little to no grip on the steering wheel) ?

Forrest Gump 9

Also, is your car lower?

I recently swap a set of 18" back on my car and experience some loose feeling in the rear. My car is lowered thru the elm, so raising the rear just one notch make the car feel a lot better.

cij911

When you change the ride height you are changing the alignment....Your car may have been too low with a lot of negative camber when combined with narrower tires (guessing you had wider tires on your 19s or 20s) gave you poor tire patch contact.

Changing just tires and rims should not make a properly aligned car pull.

Forrest Gump 9

Both my 18 and 19 have 285 in the rears.

I blame all the alignment ant tire wear problems on the airmatic system.

Worth the wait

The wheels were checked for run out by a repair shop before I mounted them and were good.

The car is lowered slightly with an elm.

I will check the air pressure, that's a good suggestion.

GregMB

Another obvious one worth checking... make sure the tires were mounted with the direction arrows pointing the correct way.

Shame on any installer who was that careless, but it's possible I suppose.


-G

Worth the wait

Thanks, I thought of that. But I can't for the life of me find a directional arrow on the tires.

Worth the wait

Ok I gathered some additional info....

Take your hands off the wheel when coasting and the car tracks dead straight.*

No vibration in the steering wheel at highway speeds

The right tire has 30psi and the left 32...probably not enough to have such a drastic effect.*

Honestly this feels like the torque steer I experienced driving a 500whp fwd Mazda I built. We nicknamed that car "the tree seeking missile" because when the big turbo spooled the power jerked the wheel towards the trees on the side of the road.*

One thing I did notice is that there is some vibration in the steering wheel under hard braking. Maybe the rotors are warped.????

Could the vibration under braking be something other than the rotors? Possibly leading to this problem?

I am stumped guys, so any help would be GREAT!

Thanks, Brian.*

bstudey01

PSS are not directional tires. They are asymmetrical, which means they have an outside sidewall and an inside sidewall. You should see outside or inside on the sidewall, but no arrows. So an asymmetrical tire can rotate in either direction, but only one sidewall can face out. Many people get confused over this.

GregMB

Did the shop that installed the wheels use an impact gun?

Sometimes the shop goons will crank those lugnuts on WAAAY tighter than the normal spec (what is the correct spec for our wheels anyway....100Lb/Ft?) and can warp cause distortion in the rotor... maybe enough to cause a slight vibration like you described.

bstudey01: Good catch! Yes, I knew there was something to watch out for on the PSS (outside vs inside). I've been conditioned to look for the arrows for so many years, that advice became second-nature.

-G

cij911

My guess is the tire pressure delta is the culprit for your acceleration pull....How does the car brake (does it pull to the same side as when you are accelerating) ??

e55amgrocket

doubt 2 PSI would cause that. I had the same problem when changing my tires but put the drag radials on and forgot about it. The airmatic changes the alignment in the rear by alot and when doing the alignment after the quaife install i went from normal to sport 2 and watched all the settings go crazy and say it was off again.

Worth the wait

Thanks for the info, helpful as always.

Worth the wait

I am **** about the torque wrench so I made sure I stood there and watch them do it.....lol.

I will adjust the pressure and see if that helps. I will also return to the shop for there input and advice.

I seriously hope I can get this resolved, because the car looks great!

93RX7LSX

Camber will not affect the pull on the steering wheel, toe will. You should install your wheels/tires, and go to a reputable alignment shop.

Bramage

Tires will wear into an alignment issue, and when you go to new tread, the existing issue becomes more prominent.

I think you need an alignment. I had mine done once, and they put the rears at zero toe-in. It felt like I was on ice when under heavy load.

Without LSD, the two side are fighting for control, and if you are at zero to toe out, the car will feel very unstable. I went back and explained this to the guy. He said: My computer shows zero toe is the correct alignment setting. I said get in.

After a quick run up onto the freeway, he gladly added .5 degree of toe in. Car is planted as before.

timeToy

I had the issue you described in the OP (pull on one side under hard acceleration and floating car when let go the gas) when I lowered my car with STAR.

I tracked it down to the rear toe setting of my alignment, I had to use the MB Arts toe links to remedy the issue AND make sure your alignment thrust angle is perfect (as in 0.00 degrees).

Worth the wait

Thanks for all the input....you guys rock!

93RX7LSX

+1 toe-in for the rear helps with high speed stability. Usually for race applications we encourage .25 toe-in in the rear. If you do a 0 toe-in for the rear, that is also sometimes used in race cars but with properly setup suspensions running solid bushings and race slicks.

Worth the wait

OK here is an update.

I have been down with a tough leg infection the last week and have just got to resolving this isssue.

It turns out I should have checked the rear tire pressure as well (MORON!).
The drivers side rear valve stem was leaking. came out last Tuesday night after work and the tire was flat.

Replaced the stem. verified air pressure and VOILA...she is back to normal!
Still a very slight pull on hard acceleration, but nothing I cant live with until I get it realligned. May still do the camber arms and toe links, but at $1200 plus install I think I will try an alignment first.

Thanks again for all your hepl guys!

Brian

lowprofile

Being that the tires were used, they might have a slight wear issue. I would swap them from left to right just to see if the pull follows the swap. Easy enough to do.

As for the vibration under braking, rotors, ball joints, and front torque thrust arms should be checked out.