handling with new 335 on the rear
06-21-2004, 11:31 AM
#1
Melting Slicks
Thread Starter
handling with new 335 on the rear
After the use of my new 335 on the rear (I used ZR1 rims) on first impression it seems to be OVERSTEER..
This made me crazy because i was expecting to be now with some UNDERSTEER problem! (bigger tires rear = understeer)
Now that I made some additional miles I can feel the car much more on the Oversteer side as expected.
I have to say that my car was handle very good before to swich to rear bigger tires... Since I made this mod for look and for better off the line
acceleration, I was thinking that now with better and NEW tires my car would turns better too.
WRONG! It turns worst and much slowly than before.
There is an explanation: When the "tire man" installed the new tires I said to do an alignment as in VETTEBRAKE web site in the "ADVANCED street"
config. When he finished the job he said:" How You was able to go straight with the setting you used before???" your alignement was completely OUT of specs!"
He reported that I was with an EXAGGErated TOE OUT on front (front tires "opened") and with an exaggerated negative camber both on front and and rear.
In effect I weared out the tires in 5,000 miles all in the interiors side.
With this alignment specs only touching the steering wheel was needed to have the head against the lateral window! It was like to go on train rails.
I was able to do a left right left ang again right with ISTANTANEOUS change of direction.
The bad side of this fantastic handling comportment was that in a very sharp corner I was not able to use a good amount of throttle.
Why? Oversteering and a 180° on hard drivig situations was the ticket to pay.
Now I have a good conservative alignement more close to a street setting.
Now I can loose the front before the rear, and I have much margin to play with the throttle during a turn.
But,... if i try to do a quick left right left righ in a quick sequence (do you know when the F1 racers are going to a "ZIG-ZAG" way in
order to have the tires in good temp?)
Ok , now when Im turning for the second time the right direction the car is still gong to the opposite side...with an eccessive side lean (roll)
If you add that I had to rise the rear of the car due to clearance problems from rear tires and fender flare... The car seems with softer
shoulders on the tire structure. This restored height (highr than before) does not help on maintain the car glue to the road...
What I want:
I want the same (or near ) responsiveness like before without sacrifing too much the normal tire life.
I want the car lower like before with LESS roll during corners (avoiding the contact between the tire and the fender flares).
I want again to enjoy my car like it was before, maintaining the new fantastic traction I gained with these new Bigger tires.
My 0-60 mph mesured with Gtech pro is now 5.48 sec (my very best was 5.79 sec ...)
Which is the righ direction in order to fight the body roll?
It's good to change the rear sway bar to a bigger one?
My car has a 22mm (measured) rear sway bar and a 26mm (measured) front sway bar. I don't know if the old owner ugraded to polyurthane
bushings (they looks like new and they are RED - I don't think the stock rubber ones are RED from the factory...-)
Ecklers sells a front sway bar in the 28 mm diameter and a rear sway bar in the 26 mm diameter. Could be this the cure to minimize the lateral roll during
turns? In this way I think I can lower again the rear of my car as I like....
Stiffenig more the rear than the front (26mm vs. 22mm stock on rear and "only" 28mm vs. 26 on front) could I expect to cure also
the understeer tendency?
I have KYB gas shocks (I think they are very hard) and a FE1 rear leaf spring taken from a 96 (I think is the softer production ever made)
I have to upgrade also to stiffer spring? (a Z51 spring with bigger sway bar diameter with poly bushing will be too much??)
Thanks
-beppe-
This made me crazy because i was expecting to be now with some UNDERSTEER problem! (bigger tires rear = understeer)
Now that I made some additional miles I can feel the car much more on the Oversteer side as expected.
I have to say that my car was handle very good before to swich to rear bigger tires... Since I made this mod for look and for better off the line
acceleration, I was thinking that now with better and NEW tires my car would turns better too.
WRONG! It turns worst and much slowly than before.
There is an explanation: When the "tire man" installed the new tires I said to do an alignment as in VETTEBRAKE web site in the "ADVANCED street"
config. When he finished the job he said:" How You was able to go straight with the setting you used before???" your alignement was completely OUT of specs!"
He reported that I was with an EXAGGErated TOE OUT on front (front tires "opened") and with an exaggerated negative camber both on front and and rear.
In effect I weared out the tires in 5,000 miles all in the interiors side.
With this alignment specs only touching the steering wheel was needed to have the head against the lateral window! It was like to go on train rails.
I was able to do a left right left ang again right with ISTANTANEOUS change of direction.
The bad side of this fantastic handling comportment was that in a very sharp corner I was not able to use a good amount of throttle.
Why? Oversteering and a 180° on hard drivig situations was the ticket to pay.
Now I have a good conservative alignement more close to a street setting.
Now I can loose the front before the rear, and I have much margin to play with the throttle during a turn.
But,... if i try to do a quick left right left righ in a quick sequence (do you know when the F1 racers are going to a "ZIG-ZAG" way in
order to have the tires in good temp?)
Ok , now when Im turning for the second time the right direction the car is still gong to the opposite side...with an eccessive side lean (roll)
If you add that I had to rise the rear of the car due to clearance problems from rear tires and fender flare... The car seems with softer
shoulders on the tire structure. This restored height (highr than before) does not help on maintain the car glue to the road...
What I want:
I want the same (or near ) responsiveness like before without sacrifing too much the normal tire life.
I want the car lower like before with LESS roll during corners (avoiding the contact between the tire and the fender flares).
I want again to enjoy my car like it was before, maintaining the new fantastic traction I gained with these new Bigger tires.
My 0-60 mph mesured with Gtech pro is now 5.48 sec (my very best was 5.79 sec ...)
Which is the righ direction in order to fight the body roll?
It's good to change the rear sway bar to a bigger one?
My car has a 22mm (measured) rear sway bar and a 26mm (measured) front sway bar. I don't know if the old owner ugraded to polyurthane
bushings (they looks like new and they are RED - I don't think the stock rubber ones are RED from the factory...-)
Ecklers sells a front sway bar in the 28 mm diameter and a rear sway bar in the 26 mm diameter. Could be this the cure to minimize the lateral roll during
turns? In this way I think I can lower again the rear of my car as I like....
Stiffenig more the rear than the front (26mm vs. 22mm stock on rear and "only" 28mm vs. 26 on front) could I expect to cure also
the understeer tendency?
I have KYB gas shocks (I think they are very hard) and a FE1 rear leaf spring taken from a 96 (I think is the softer production ever made)
I have to upgrade also to stiffer spring? (a Z51 spring with bigger sway bar diameter with poly bushing will be too much??)
Thanks
-beppe-
06-21-2004, 12:23 PM
#2
Safety Car
Re: handling with new 335 on the rear (conv90)
You are getting just exactly what would be expected from running a wider than normal tire on those rims.
If you run the tires at the 'normal' air pressure the contact patch is reduced because the sidewalls are bulging. If you run the pressure down enough to keep the maximum contact patch some tires don't have a sufficiently hard enough sidewall to keep the tire from rolling over.
If you run the tires at the 'normal' air pressure the contact patch is reduced because the sidewalls are bulging. If you run the pressure down enough to keep the maximum contact patch some tires don't have a sufficiently hard enough sidewall to keep the tire from rolling over.
06-21-2004, 05:52 PM
#3
Heel & Toe
Member Since: Jun 2004
Location: Frewsburg NY
Posts: 16
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Re: handling with new 335 on the rear (conv90)
Wouldnt a larger sway bar increase oversteer?
I can't remember for sure, but I think that toe increases a car's twitchiness, which is what you seem to be missing. Maybe read up on some simple suspension tech and learn what things such as positive camber, toe in, toe out, etc etc translate to the car's feel.
Probably a bit of toe in on the rear would help acceleration, since wheels have a tendency to toe out on heavy acceleration. I _think_ a small amount of toe out on the front would make the car more responsive and some negative camber should help the car sit down into the corners better...probably have it more negative in the rear and less in the front.
Other than that, the last poster is pretty much right about either having the sidewalls flex or having the tires over-inflated.
I can't remember for sure, but I think that toe increases a car's twitchiness, which is what you seem to be missing. Maybe read up on some simple suspension tech and learn what things such as positive camber, toe in, toe out, etc etc translate to the car's feel.
Probably a bit of toe in on the rear would help acceleration, since wheels have a tendency to toe out on heavy acceleration. I _think_ a small amount of toe out on the front would make the car more responsive and some negative camber should help the car sit down into the corners better...probably have it more negative in the rear and less in the front.
Other than that, the last poster is pretty much right about either having the sidewalls flex or having the tires over-inflated.
06-22-2004, 03:36 AM
#4
Melting Slicks
Thread Starter
Re: handling with new 335 on the rear (brent_strong)
Wouldnt a larger sway bar increase oversteer?
I can't remember for sure, but I think that toe increases a car's twitchiness, which is what you seem to be missing. Maybe read up on some simple suspension tech and learn what things such as positive camber, toe in, toe out, etc etc translate to the car's feel.
Probably a bit of toe in on the rear would help acceleration, since wheels have a tendency to toe out on heavy acceleration. I _think_ a small amount of toe out on the front would make the car more responsive and some negative camber should help the car sit down into the corners better...probably have it more negative in the rear and less in the front.
Other than that, the last poster is pretty much right about either having the sidewalls flex or having the tires over-inflated.
I can't remember for sure, but I think that toe increases a car's twitchiness, which is what you seem to be missing. Maybe read up on some simple suspension tech and learn what things such as positive camber, toe in, toe out, etc etc translate to the car's feel.
Probably a bit of toe in on the rear would help acceleration, since wheels have a tendency to toe out on heavy acceleration. I _think_ a small amount of toe out on the front would make the car more responsive and some negative camber should help the car sit down into the corners better...probably have it more negative in the rear and less in the front.
Other than that, the last poster is pretty much right about either having the sidewalls flex or having the tires over-inflated.
A bigger FRONT sway bar increase UNDERSTEER ( or if you prefere it reduce oversteer).
Since it seems that I have a NOT NEUTRAL car now, (it is on the UNDERsteer side), I think I have to increase the REA sway bar more than the front.
Maybe (before the swap to larger rear tires), the car was so responsive because the exaggerated Toe OUT. Now, (with the new alignement specs and new tires) the front toe in is near to 0.
About the "smaller rim" compared to the tires I'm not so sure this only 11" rim is so undersized.
Yes I have the rear tires slightly underinflated, bu In any case, even with the "right" pressure I have ALL the contact pach available and the traction is Awesome. I'm not with a 335 tire on a 8" rim.. I'm with a 335 tire (with suggested 11 to 13 rim) with a 11" rim.
Thanks.
-Beppe-
06-28-2004, 08:49 AM
#5
Melting Slicks
Thread Starter
Re: handling with new 335 on the rear (conv90)
:mad :mad 
:mad 
The situation becomes worst and worst.
It seems I have a weak pudding on the rear!
Every time I go into a turn it seems I have the rear tires flat. Do you know the sensation when you have a flat tire? well, think to have TWO rear flat tires!
Going straight or starting from a dead stop the car is good. When I go to a turn I have this sensation on the rear. The car is able to turn, but I have not the complete control of the car, I have not the "feeling" on the rear. The rear is not going outer or external (tipical oversteer), it bounces left and right (not up and down) like a flat tire situation.
I tried all the inflation pressure available: From 24 psi to 50 psi. Even at 50 psi (I tried just to try...) with the tire solid as a rock and with side of the tire very stiff, I have the same "pudding" sensation. :mad
Maybe the additional gained traction is able to flex the sway bar and the frame more than before resulting in this bad sensation?
I can't say if I have more body roll or only a "skating" sensation.
I have to verify with someone that can see the car from the rear when I'm driving a turn.
The contact pach is perfect even at 50 psi. It's not essential requirement to go with less than suggested inflation pressure to have a good contact to the ground. Even at 50 psi I'm NOT absolutely able to break traction even doing a TOTAL WOT from a dead stop!
I checked the rear antiswaybar and the bushing seems good.
I tried (going under the car) to hold the total rusted bar with two hands and tried to shake it with a good level of force. Well, the 22 mm bar can flex with a noticeable evidence. A rear sway bar should flex with evidence under solicitation?
Please help me help me help me help me to find a sulution..
Thanks
-Beppe-
:mad The situation becomes worst and worst.
It seems I have a weak pudding on the rear!
Every time I go into a turn it seems I have the rear tires flat. Do you know the sensation when you have a flat tire? well, think to have TWO rear flat tires!
Going straight or starting from a dead stop the car is good. When I go to a turn I have this sensation on the rear. The car is able to turn, but I have not the complete control of the car, I have not the "feeling" on the rear. The rear is not going outer or external (tipical oversteer), it bounces left and right (not up and down) like a flat tire situation.
I tried all the inflation pressure available: From 24 psi to 50 psi. Even at 50 psi (I tried just to try...) with the tire solid as a rock and with side of the tire very stiff, I have the same "pudding" sensation. :mad
Maybe the additional gained traction is able to flex the sway bar and the frame more than before resulting in this bad sensation?
I can't say if I have more body roll or only a "skating" sensation.
I have to verify with someone that can see the car from the rear when I'm driving a turn.
The contact pach is perfect even at 50 psi. It's not essential requirement to go with less than suggested inflation pressure to have a good contact to the ground. Even at 50 psi I'm NOT absolutely able to break traction even doing a TOTAL WOT from a dead stop!
I checked the rear antiswaybar and the bushing seems good.
I tried (going under the car) to hold the total rusted bar with two hands and tried to shake it with a good level of force. Well, the 22 mm bar can flex with a noticeable evidence. A rear sway bar should flex with evidence under solicitation?
Please help me help me help me help me to find a sulution..
Thanks
-Beppe-
