crai6m4ck

Does anyone have any experience with these sizes on a 3rd gen? I want to lower my car and still TRY to retain some of whatever ride quality the rx7 has. I don't want to be bouncing or slamming on tiny pot holes and cracks. I am going to get either 18's or 19's and at this point I am set on 18's, but want to see if anyone can bring me to go the extra inch. The rims I'm getting are mostly for show but will be on the car during the summer months when it is a daily driver (any other time it is in storage). I realize 18's will hurt acceleration but will 19's make much more of a difference? Both sizes are almost exactly the same weight. Please reply soon because I have money in hand and will probably spend it within a few days.

MakeShift

19's are to big and are hard to fit, plus you could crack a rim.

maxcooper

I have a set of 18"s that I run on the track. I used them on the street for a day (to heat-cycle the track tires) and they felt pretty rough over the pot-holes. I have heard others complain that 18s are troublesome on the street, so I ordered some 17" wheels for that. If ride quality is a major concern for you, 19" should be out of the question, and 18" is probably pushing it, too.

Acceleration:
Big, heavy wheels will hurt acceleration because of the increase in rotational inertia. Rotational inertial is a function of both static weight and diameter. I did some rough calculations comparing 275/40-17" with 285/30-18" wheels and tires. I compared CCW wheels (http://www.ccwheel.com/) in both 17" (18.5 lbs) and 18" (~20 lbs) sizes (both 10" wide), and my SWAG is that the 18" wheels have 20% more rotational inertia. However, the 275/40-17 tires are about an inch bigger than the 18"s, weigh more, and obviously have a bigger diameter than the wheel. So, my estimation turned out that the 18" wheel/tire combo had about 5% less overall rotational inertia than the 17" combo I was considering. So, the lesson I learned here is that tire weight, and especially tire diameter play a major role in inertia, and should not be overlooked when considering a wheel/tire package.

Also, there is a wide variation in tire weights that may help make up some weight if you have heavy wheels. Bridgestone and Toyo tend to make light tires. The Tire Rack spec sheets and manufacturer's web sites sometimes list weights for tires.

I was delighted to find that my 18x10" wheels with 285/30-18 tires (all four corners) did not rub anywhere. I've got coil-overs (550F/450R), have less than 1/2" drop in ride height, and I removed the fasteners holding the fender liner in place on the front wheel arches. The wheels have exactly 7.5" of backspacing (I measured) and the total rim width is actually about 11.25" (so don't just calculate your offset using 10" width and 7.5" backspacing).

However, I think that 8.5" front width and 9.5" or 10" rear width is a much easier fit with common offsets. Also, I have heard it said that tire diameter seems to be the biggest factor in determining if they're going to rub.

-Max

AARotary

I have a set of 19x9 front and 19x10 in the rear with 2" drop with the coilovers and the ride is stiff and bumpy. If you are going for show then 19" is the way to go but for street and daily driving I would recommend to get the 18" wheels max for street.