V8kilr

hey everyone knows the easy upgrade on stock 13" rx7 rims is 205/60 r 13,but by accident i typed in some wrong numbers and found you can also get 215/50 r 13.

does anyone know if these will fit???

i just bought another set of tires from the tire rack and found them while i was buying some new 205/60 r13 summer tires.

man i hope they dont fit or ill be kicking myself in the *** on that one.

when you convert it over here is what your looking at


185/70 = 7.28" wide and 5.05" sidewall "STOCK"

205/60 = 8.07" wide and 4.8" sidewall

215/50 = 8.46" wide and 4.2" sidewall

that means their lower profile with a wider tread.

madaz07

if they did fit being that wide i thnk they would get alot of tire roll on the stock rim. i have 205 60 13s on my car and they roll a fair bit.

V8kilr

oh but there so wide and low profile,i just cant resist,my car is mainly used for daily driving and straight line performance,so a little roll in the corner dont bother me,

on my girlfreinds 93 ford probe we had aftermarket rims and tires,here was the setup 16 x 7" rims with 245/45 zr16,the tires were 9.64" wide !!!! on 7" wide rims,i think thell fit after remembering that.

peejay

If you care about straight line performance, stay away from low-profile tires... they have worse straight-line traction and higher rolling resistance because of the way the contact patch is shaped, and the stiffness of the sidewalls.

I personally wouldn't try to put 215/50 on anything narrower than a 7" rim.

V8kilr

what are the stock rims 5"???
i wanted more of a contact patch,plus i though they would look great,i could always run them a little under pressure for drag racing.
does this sound like a really bad idea?
should i just be happy with my 205/60 ?

peejay

The only way to get more contact patch is to run less tire pressure. When you put larger tires on, there's less weight to flex them outwards, and you end up with the same size contact patch.

Wider tires, especially wider SHORTER tires, have a wide, short contact patch. This is bad for acceleration. For maximum forward traction you want as long of a contact patch as possible, which means as tall of a tire as you can stand, with the softest sidewall you can stand.

For rolling resistance (not AS important for drag racing but it does matter) you want the narrowest you can use. Rolling resistance is mainly from the tread flexing from round to straight, then straight to round again.

You might find that you get more traction with a 185/70 instead of a 205/60. For cornering, sure get those 215/50s but put them on 13x8 wheels and don't expect to have as much forward traction. Certainly 205/60s will suck for cornering AND acceleration, when on the stock 5.5" rim, because they will flex around a lot and are shorter/stiffer than the stock size tires. On 7"rims they are great for cornering but not so good for acceleration...

yayarx7

I think Tire compound/tread design would be as important if not more important than size selection.

Any arguments?

peejay

Yes.

I tried DOT-R tires (that would corner hard enough to make my arms sore the next day - as in not being able to raise them above shoulder level) in a drag racing environment. They were 205/60, V-rated. No matter what I did with tire pressure, burnout, etc., they simply would not hook up at the starting line. I did notice that the 1-2 shift was more violent, however. Instead of merely chirping the tires, it would also make the whole car jump sideways too. When bracket racing, I ended up just launching VERY conservatively so I could remain consistent.

I put my stock, high treadwear rating, S-rated 185/70s on, and instantly had MORE traction off the line.

Take that how you will... but considering that the 185/70s definitely had a harder/less grippy rubber compound (very driftable tire ) the only other thing that could have made them launch better would be the fact thyat they have a long, narrow contact patch, and deformed easier.

Of course you can have the best of both worlds, we call them "drag slicks" Notice that true drag slicks are pretty tall for their width, and the sidewalls are so soft that they wrinkle. When they launch, the rim actually winds up the sidewall and you get a TON more rubber on the road.