v8eater

who is in favor of putting 275/40/17 in the rear of my 93 rx7 . I have 225/45/17 in the front and I have 255/40/17 my rim size is 17.9 in the front and 17.10 in the rear. whatcha think?????????

rx7even

I say go for it. When/IF I ever find my rims, I'll have 17x9 or 17x10 in the rear, and I'll put a 275/40/17 on there (should be a tight squeeze on the 17x9, but it can be done). On the front 17x8 or 17x9's, I'll probably put on a 235/40/17 or 245/40/17, not sure which yet. With a 225/45/17 in the front and a 275/40/17 in the rear, you will have a decent amount of understeer.

SleepR1

I'm against it for many reasons:

275/40-17 is ~1 inch taller in overall diameter (compared with stock (25.7 vs. 24.8 inches OD). Not only will your acceleration suffer from an overall taller rear-end gear (due to the taller tires), but your speedometer will underestimate your speed (resulting in higher speeds than your speedometer indicates). The only way to compensate for this is to install a 4.33 ring and pinion gear. Very expensive to do!

Consider the weight of a 275-40-17 tire. Unless you get Pirelli P-Zero Asimmetricos (available in 265-40-17 and very light for the size), most tires in the size you're considering will weigh in at 30 lbs+. Add that weight to the weight of a 10 x 17 wheel (25 lbs+), and you're talking 55 to 60 lbs of wheel and tire! Compare that weight with a stock 225/50-16 tire on the stock 8 x 16 wheel for a combined weight of <40 lbs!

So you lose acceleration from the taller gear AND the greater rotational inertia the motor has to deal with, in turning 60 lbs of wheel and tire.

The other bad part about your setup is the extreme understeer you will have. The general rule is no more than 30 mm difference between fr/rr tire section widths, lest ye dial in too much understeer. Understeer is not a bad thing, but certainly too much of it, takes out much of the fun in driving a high performance car like our FD Rx7s. With 50 mm wider in back, your car will push like a NASCAR pig!

Also your 9 x 17 up front will be too wide for a 225/45-17. Ideally you could run 245/40-17 or perhaps a 255/40-17 on the 9 x 17s as long your offset is 45 mm or greater. I would choose 10 x 18s in back and install 285/30-18s on them. You get the width you want, you stay within the stock overall tire diameter (24.7 inches); and the lower profile tires in back compared with the fronts, compensate for the increased understeer from a 40 mm wider rear tire. This is because the decreased tire profile in back increases the overall spring rate, which increases oversteer (thereby decreasing understeer--get it?).

Now if you don't care about all that stuff, fine. You're motivated by looks, and that's your perogative. Just don't be surprised if you get blown away by a "sleeper" Rx7 running on stock sized wheels tires.

v8eater

just showing a picture of my current rims and tires 225/45/17 in the front and 255/40/17 in the rear

SleepR1

The car looks great! If I had this setup, I'd go with 235/45-17s up front on the 9 x 17s and 265/40-17s in back on the 10 x 17s. The overall diameters for both sizes will be a shade over 25 inches, which is close enough to stock. The tires I'd choose would be Pirelli P-Zero Asimmetricos. Those sizes will come with P-Zero Asimmetrico in yellow lettering (very cool on a black car). The Pirellis are incredibly sticky and are light for their sizes.

I plan to go with this very same tire setup except my wheels will be 0.5 inches narrower than yours--8.5 and 9.5 x 17 SSR Competitions. The 8.5 x 17s weigh 14.5 lbs and the 9.5 x 17s weigh 15 lbs. Both are lighter than the stock 8 x 16 which varies in weight between 15.5 and 16 lbs.

Dreamin

Nice... Work Roar? Those are some damn light wheels. If you're ever selling, lemme know.

rx7eaven

Beautiful car!! Those are very nice wheels. What kind of suspension package do you have on your car? Just curious because sitting on stock wheels it appears, in the rear, to have a rather large gap. Thanks
94 rx7 blk r2

v8eater

If I told you all you might just laugh. well I have gabs in the back one gab on the right front and one stock on the left. I don't drive my car much so iam taking my time fixing this mess. I had both gabs in the front but it made my car to low and my tire rubbed so I tried to take them off. I had such a hard time trying to change one I just left the other gab shock on until I find the right struts for the front. I might just use R1 or R2 front struts because its just for the streets. or if something comes along at a good price I might jump on it.

spyfish007

v8eater . . . I thought you had the 4.33 gears?

SleepR1

The shocks should have no bearing on ride height, unless you have threaded shock bodies, ie aftermarket coil-over setup. The Koni FD shocks do have adjustable ride heights, but the adjustment is very slight.

The choice of aftermarket springs do affect ride height. H&R, Pettit, and Racing Beats sport springs lower the FD between 1.25 and 1.5 inches. The Eibach springs lower between 0.75 and 1 inch.

If you plan to run your FD on the street only, then, you'd do well to have the R2 shocks instead of the R1 shocks. The R2 shock is slightly softer than the R1 shock, but the R2s are much firmer than either the Touring/PEP or Base shocks.

Ideally you should have the same brand shocks all around. If you're finances don't allow that, you should at least go with the same brand at each end of the car, ie--GAB in back and R2 shocks up front.

v8eater

No Spyfish I don't have the 4.33 gears give me information on that!!

spyfish007

Oh well, I thought from one of our previous conversations that you had the 4.33 gears. Ari runs them in his car and later J-spec versions came stock with the 4.33 gear. They cost a little under $500 and they help with acceleration. They take a couple tenths off your 1/4 mile time and definately make the car feel faster. You are basically trading top speed for acceleration, but your top speed will only drop about 10 mph . . down to 173 from 182 @ 7500 rpm (info via RPs web site) . . Call RP and get some more info/additional opinion.

So how is the car running?

95R2-89TII Ground Zero

I don't like the idea of putting that size tire on the rear. The whole weight thing is a little scary. Actually I like the way it looks now. I do agree with the fact that the stock FD does look like it has some scary rear wheel gap, but nothing some springs can't cure. Oh well, good luck, but I like what you got now.