ROTRYPWR

Well i know its been brought up before...but lets get all the info and put it into this thread...

How much will 19's on lets say (front) 8.5-235 and (rear) 9.5-255 how much would this effect the overall handling of the rx-8????

If i could go through a sharp turn at 60 m/ph with stock rims and tires, would this new tire set up reduce that by like 5 m/ph or would i maybe be able to go through the turn faster?

Can anybody with expierence in this field answer thid question?

Thx a lot !

AutoBahnRX8

I've got 19s, 8.5-245 front and 9.5-275 rear and the car feels great, personally, I feel tighter going into turns, and more push and less spin going out. Overall, I feel more confident with the 19s on and drive faster in the turns than when I'm on my 18s.

crossbow

19's of the same weight as the stock 18's with the same type of rubber will...

1) Increase braking distance.
2) Decrease acceleration.
3) Increase suspension/brake wear
4) Decrease mileage

Here's an article on unsprung weight and how important it is to the overall handling characteristics of the car.
http://www.mazda6tech.com/index.php?...d=16&Itemid=32

Here's an article on the negative aspects of plus sizing to a larger diameter rim. (The opposite applies if you reduce the rim's diameter).
http://www.mazda6tech.com/index.php?...d=44&Itemid=32

If you wanted maximum performance...I'd imagine some 17x8 SSR comp's with Kumo Mx's would utterly dominate.

Running staggered setups is also not recommended, as it tends to promote understeer...the last thing you want when your trying to drive aggressively around a track or autox course. Looks sweet though.

Generally when most people plus size, they notice an increase in a variety of car performance aspects. This isn't due to the rims...its due to the high performance rubber they just put on.

Had they dropped a significant amount of unsprung weight (say each corner down to 34.2 lbs vs the stocks 47/48) and dropped the diameter to 17 inches...they'd probably **** themselves to death at the difference.

mysql101

I doubt the move to 19's will be noticable from 18's, unless you got some heavy *** rims. My new 19" rims weren't expensive, but they're no heavier than stock.

Also, the rubber is 35 instead of 45 tall, which makes for:
1) Less sidewall, so there isn't as much flex on turns
2) Tire isn't as tall, so the tire+rim is the same size as stock.

crossbow

Remember that due to rotational inertia, a larger rim of the same weight as a smaller rim, will still be slower...as the weight is pushed further out from the center of the wheel. A single inch can effect the overall effect on the car as much as 10%.

Not much? Depends on how much performance your looking for. A 2 lb tire weight difference on a 19 inch rim can have as much as a 100 lbs static weight difference on the overall performance of the vehicle...or 15 hp, or 0.1 in the 1/4.

The biggest disadvantage of running giant wheels is in tire selection...many of the top tire choices by well known and respected performance manufacturers stop at 18 sizes. Then of course, if your running 19's, your probably not racing the car anyway, so I guess that point is rather mute.

WTF no turbo

Please STFU.You have no idea what you are talking about.My 19s are .5" smaller then stock size.Also as far as weight gos,I saved about 2 lbs a corner maybe 3 up front.So your statements above as follows.
1.Wrong
2.Wrong
3.Maybe
4.Added about 100 miles every 10000.
Now for your next post.

mysql101

The centrifugal force will increase the larger the rim.... but one also has to keep in mind the weight and mass of the tire itself. On the stock setup, tire and rim is close to 50 lbs, and the rim itself is half that. So even if your rim is larger, your tires are less so, and because almost half the weight was on the outer edge (Tires), you may well decrease unsprung weight.

My 19" tires and rims are the same diameter as the stock 18" because while my rim is larger, my tire sidewall is smaller.

My point is, not all tires or rims are the same. The weight varies, and the position of the weight varies. It's hard to have a universal truth with so many variables.

I still don't think *MY* setup hurts me much, but your mileage may vary.

crossbow

Nice wtf no turbo. Put 17x8's on your car, and you'd stfu in a second, mr stfu noob .

Use the formula.
http://www.mazda6tech.com/files/rotational.xls

PUR NRG

I must be full of crap then too because I agree with most of crossbow's statements. Put more weight on the outer edge of a circle and it increases the polar inertia. Put the same amount of weight farther out on a bigger circle and that increases polar intertia.

This is one of the reasons why racers use the smallest diameter wheel they can. Aesthetically it doesn't look as good but performance speaks for itself.
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lourx8

WTF No Turbo, now for your reply :D

MazdaManiac

iTrader: (3)

Increasing the diameter of the wheel is a small part of the equation.
As Jason pointed out, you are reducing the load of the tire itself, so at the same weight, you might be reducing the inertial moment of the outer diameter of the wheel.

I had a measured decrease in braking distance (3 to 6 feet) and no measurable change in acceleration when I went to 19" wheels as verified by my G-Tech PRO.

Kel Rx8

rofl thats funny.

Kel Rx8

well i for one have some heavier rims
im running 20x9 front and 20x10 rear
but i think my car handles better in sharper turns and i tend to push the car more
with my maido wheels then oem wheels.

p.s i hate and dont trust the stock tires mazda and nissan gave us crappy tires

Gord96BRG

This is a trick question - as discussed, if the 19s weigh the same or less as the relatively heavy stock 18s, then the wheels do not matter. Yes, crossbow is correct about the implications of unsprung weight and inertia, but (again, if the weight is no greater) these negative effects will be minimal for street use. Disclaimer, the staggered setup (wider rear tires and wheels) will do exactly as crossbow says, increase understeer and degrade handling.

The key is the TIRES - put cheap-*** ricer tires (eg, Nitto, Parada, etc) on the big rims because they're all you can afford, as so many buyers do, and the handling will be worse. The tires will be the key - and tires make a great contribution to unsprung weight as well. Identical size tires from different manufacturers can vary by as much as 4 or 5 pounds per tire, and that's at the key outermost radial location for the most impact on inertia also.

My suggestions:
- forget staggered sizing if you care about keeping neutral, balanced handling
- buy the absolute lightest wheels you can afford. If you can't afford LIGHT 19" wheels, don't buy cheaper heavy 19" wheels.
- buy the best, grippiest tires possible - and get the lightest of the best, grippiest tires for the ultimate improvement.

Regards,
Gordon

PUR NRG

No doubt wheel diameter by itself isn't the total picture. When you went to 19" wheels, did you use the same brand/model tire? Were they at roughly the same amount of wear as the 18" set you measured against?
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MazdaManiac

iTrader: (3)

I measured the particulars of the RX-8 over a long period with the OEM wheel/tire combination. There wasn't much variation (on average) for braking distance as the tires approached the 7000 mark.

Now I am using "cheap tires" (according to Gord96BRG) - Nitto - with about 2000 miles on them.
I bought the Nittos by choice - not because of price.
These are my third set of Nittos on three different cars and they are excellent.

BaronVonBigmeat

You must have missed the very first statement he made:

It isn't really fair to compare 19's with 35 series tires mounted to 17 or 18 inch wheels w/ 45's mounted. In the world of science, an experiment is worthless if you don't keep all the other factors constant--let's compare both wheels w/ 45 or 40 or 35 series tires.

If you do, it is a scientific fact that the best 17's will beat out the best 18's, which will in turn beat out the best 19's, in terms of rotational inertia. Assuming similar tires on each, of course. (Yes, you can probably find a high dollar 19 that will beat a ****-poor bargain basement 18.)

A 17" wheel w/ top-notch 35 or 40 series tires is the ideal performance wheel for our cars. The only problem is the wheel arches on an RX-8 really do look like they were designed for 19's. If it wasn't for the odd look, I'd definitely be getting some 17's.