Hi i havent driven my Rx7 for nearly a year beend doing a few mods. Over the last year i installed some brand new Advan 18" wheels with racing semi slick tires. Decided to test drive car today and im not happy about how hard the car is now (before i had standard 16" wheels). With standard wheels the car was firm but still comftable to drive, now pot holes cause the back end of the car to bang pretty hard! (noticed the front doesnt do it?).
What i want to know is this normal , i love the wheels but am not liking the ride quality at all. Car doesnt seem to bang over all pot holes just when there is a ridge or bump in the road, ive noticed the front doesnt bang only the back could it be that my rear suspension wants new bushes, Maybe the racing tires are to firm on the side walls and a different tire may be more comftable. (and now dont laugh if this is the way 18" wheels are,, can i some how soften the suspension to go back to how it was with 16" wheels).
Any and all advice appreciated.

 

You probably lost a good amount of aspect ratio....side-wall width, inorder to get 18" wheels and tires to fit. I'm guessing the thinner and typically stiffer side-wall and possibly wider foot-print of whatever tires you bought are contributing to the harsher ride.

 

stock suspension? maybe you are hitting something, when I went to my 18's I had to install coilovers to raise my ride height to fit the tires.

as for ride comfort, a lot will depend on the tire compound you are using. my hankook v12s are super smooth and quiet on the street vs my old hard s02s which were loud and rough

 

That might have as much to do with tire choice (and size) as wheel size. Semi-slick race tires likely have VERY stiff sidewalls. If you put some true street tires on there, they should be much more comfortable... and some street tires are "plusher" than others.

Also, not sure what sizes you're running, but if you go with 255/35 and 275/35 vs. 285/30 or 245/35, you'll have a little more sidewall for comfort.

 

tire psi what is it?

 

Right tires are 265/35/18 (they are avon ZZR semi slick racing tire),
Stock suspension.
Like i said fronts dont feel that bad,, can someone recommend a nice soft good quality tire for the back. or maybe a dfferent aspect ratio for the back that will restore some of the quality.

 

tire psi is 28

 

When changing wheels, two things affect ride comfort:

1. Tire sidewall height. The more sidewall you have, the more the tire will absorb the road feel and not transmit it to the cockpit.

2. Tire stiffness. Same as above.


You did both at the same time: You made the sidewall shorter and you used a very stiff competition tire. You can alter the tires to something less stiff, but you'll always have rougher ride due to the less sidewall going from 16" to 18" wheels.

 

Mahjik i can cope somewhere in the middle,, think i might buy some normal road tires (softer) for the back and see how much a difference it makes.

 

Road tires will be the ticket.