Changed Rear Tires........
Thread Starter
Racer
Joined: Sep 2004
Posts: 389
Likes: 0
From: Sayreville New Jersey
Changed Rear Tires........
Changed only the rear tires (Firestone Indy 500 Firehawks 255/60/15)on my '78 Daily Driver and the handling has gotten really loose. Could it be because of mis-matched tires? The fronts (Hoosier's also 255/60/15's) are not too bad and I am planning on installing (4) new shocks this weekend and then getting the front tires and alignment. Even though I know my current shocks are bad the car still handled good until now. 
Drifting
Joined: Feb 2003
Posts: 1,461
Likes: 2
From: Allen TX
I doubt its from running mis-matched tires. I have run mis-matched tires numerous times and it doesn't really have an affect on the handling. Now if you had a super tacky tire on the front and a set of worn crappy tires on the rear then I am sure you would have a problem, but it doesn't sound like that. I would check tire pressures all around and make sure everything is torqued to spec.
How does it feel loose?
How does it feel loose?
Thread Starter
Racer
Joined: Sep 2004
Posts: 389
Likes: 0
From: Sayreville New Jersey
"How does it feel loose?"
Mostly when changing lanes at highway speed feels like the rear kicks over further than it should, also on rough or choppy road it's all over the place and requires two hands to keep it pointed straight. It was fine 'til I had the rear tires put on!
Mostly when changing lanes at highway speed feels like the rear kicks over further than it should, also on rough or choppy road it's all over the place and requires two hands to keep it pointed straight. It was fine 'til I had the rear tires put on!
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
I would change the shocks on all four, and put on the new fronts and do a four wheel alignment see what happens... If it needs it anyway do it. Its not like your guessing or throwing money a problem.
Racer
Joined: Mar 2003
Posts: 268
Likes: 0
From: Mechanicsville VA
my bet is it is the tires. while i have no direct experience with either the Hoosiers or the Firehawks, i did have a '78 Grand Prix company car about 20 years back that had some decent performance tires and I'd come smoking into the toll booths, cram on the brakes, toss in my dime (yes, it was that long ago!), and mash the gas coming thru the gate. they gave me a newer car, and were going to send the GP to a sales guy who freaked at the raised white letter tires and wanted whitewalls )(go figure...). So i had this thing with pimpmobile tires for about a week before my new car came in, and i learned that my normal toll booth procedure became downright dangerous...I nearly slid thru the gate and couldnt gain traction (with a very very weak small v-8) once i accelerated away from the gate that narrowly escaped being sheared off.
all this to say that tires do make a difference. i bet if you tried swapping front and rears (hey, they're the same size, right?) that you'd go from loose to tight in a hurry.
all this to say that tires do make a difference. i bet if you tried swapping front and rears (hey, they're the same size, right?) that you'd go from loose to tight in a hurry.
Pro
Joined: Sep 2003
Posts: 511
Likes: 4
From: Phoenix AZ
If it's not the tires, I'd say when the car was jacked up to change the tires it may have over stessed some already deteriorting bushings. That might change the geometery a little and that you might feel.
So what shape are the bushings in?
So what shape are the bushings in?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Melting Slicks
Joined: Sep 2004
Posts: 2,412
Likes: 3
I'm casting my vote for 'too much' tire pressure. If your old tires were underinflated, they'd be less likely to slide out (oversteer). I'm assuming that's what you mean by "loose." Try dropping the tire pressure down 5psi in the rear and see if it helps. 
Melting Slicks
Joined: Feb 2003
Posts: 3,053
Likes: 4
St. Jude Donor '03,'11
swap front to rear and see if there is any difference.
hoosers??? ain't that a racing tire? they are probably more sticky than the firestones with 500 treadwear which would cause the car to get loose.
hoosers??? ain't that a racing tire? they are probably more sticky than the firestones with 500 treadwear which would cause the car to get loose.
Thread Starter
Racer
Joined: Sep 2004
Posts: 389
Likes: 0
From: Sayreville New Jersey
Checked the pressure this afternoon on the rears when I got home from work. After 27 miles they were at 38psi DS and 40psi PS. I don't usually check them warm so I'm not sure what they should be at then. I've alway kept the Hoosier's (yes they made street tires a while back tried to compete with Goodyear and Firestone, they were on the car when I bought it 3 years ago) at 32 psi when cold. I'll check tomorrow when cold and adjust to 32 to see if that helps. I'm guessing it will.....
Le Mans Master
Joined: Nov 2004
Posts: 6,434
Likes: 0
St. Jude Donor '07
Originally Posted by turtlevette
swap front to rear and see if there is any difference.
hoosers??? ain't that a racing tire? they are probably more sticky than the firestones with 500 treadwear which would cause the car to get loose.
hoosers??? ain't that a racing tire? they are probably more sticky than the firestones with 500 treadwear which would cause the car to get loose.
Drifting
Joined: Feb 2003
Posts: 1,461
Likes: 2
From: Allen TX
Originally Posted by Hwy St*r
Checked the pressure this afternoon on the rears when I got home from work. After 27 miles they were at 38psi DS and 40psi PS. I don't usually check them warm so I'm not sure what they should be at then. I've alway kept the Hoosier's (yes they made street tires a while back tried to compete with Goodyear and Firestone, they were on the car when I bought it 3 years ago) at 32 psi when cold. I'll check tomorrow when cold and adjust to 32 to see if that helps. I'm guessing it will.....
Thread Starter
Racer
Joined: Sep 2004
Posts: 389
Likes: 0
From: Sayreville New Jersey
Lowered the rear tire cold psi to 32 and now all is well. At least back to where it was. Can't wait to get the KYB Gas-Adjusts shocks on this weekend, the new front tires on Monday and get the alignment done to see the results.....