I am researching 18" wheels for purchase, and I am getting different recommendations from different local tire shops. One says that putting 9" wide wheels on the front will decrease performance. The other says they will make the car more stable and actually increase performance. Anyone have any personal experience?

 

if you ultimately want more grip get as wide as you can get on the front... and do the same on the rear...you will get a lot more road feel and will feel like your car is not aligned....i think its all personal pref. though and what size tire you want/have...if you have your 9 in the front with a 225 tire...itll feel like crap for sure...i have 9.5 front with 265/35/18..not a bad fit...but im more into motorsports so i give up comfort...if i wanted to make it more suitable and easy driving i would get same as stock... what do you want it for..? want performance get wide as you can...thats what i do...

-Gene-

 

you can go up to 18X9.5 with 275-35-18 tires :D ( with the right offset )

 

So what *is* the proper offset for the 9.5 wide wheel? I know Mazda was generous enough to allow some more room in these wheel wells and I'm looking personally for some 9.5s or 10s for auto-x possibly next year (and 275s will probably be the size run).

Links to existing threads would help too if you have them, because search doesn't allow two digit numbers... and searching on offset leads to general questions about the stock wheels or what's the right offset for thinner wheels.

--kC

 

18x.9.5, 45mm offset will fit front and back.
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Contact Goodwin Racing in San Diego, that is the setup they run.

 

Yes, see this thread: http://www.good-win-racing.com/mazda...topic.php?t=53

 

All I gota say to this thread is W:D W!
9.5" x 18 wheels @17.2lbs + 275/35/18 RT-615s @26.9lbs = 44.1lbs

That's 4 lbs lighter + 2.5" w-i-d-e-r than stock - OMG what this must be like on the track...
Thank you Goodwin Racing for trying and discovering this combo

Now I need to upgrade my measily (but awesome) 235/40/18s RT-615s w/stock wheels to these!

 

Get your name on the list...the last bunch of rims sold out before they got here....and this batch surely will too :D

 

Stock rims are 8", that would be 1.5" wider, not 2.5."

 

Keep in mind that 17X9.5 with 275-40-17 will weigh about the same and would also cost less.

Using Tire Rack info:
Kumho Ecsta MX, this tires has won STS at tht solo2 natls and is on many of the fastest cars.
275-40-17 28 lbs $166.00
275-35-18 27 lbs $232.00

For wheels nothing beats an SSR on weight:
17x9.5 Comp 15.5-16.7 lbs $429.00
18X9.5 Comp 17.5-18 lbs $499.00

So the 17 tire weighs a bit more, the 17 wheel is a bit lighter, call it even.
However you are looking at $1716.00 VS $2495.00 for the wheels.

Then $664.00 VS $928.00 for tires. The wheels you only buy once, but if you go with 18s you are looking at $264.00 extra each time you buy tires. You can buy four sets of 17 for the price of 3 sets of 18s. Some of the ST class racers will use that many in a year.

I have a hard time with the weight Goodwin list for the Enkei. On the Enkei website they do not have a weight for that wheel but the smaller 18X8.5 is over 18 lbs, you dont get lighter as you go bigger....

http://www.enkei.com/RacingSeriesSpecs/RPF1.html

 

Forget the wheel size! I comparing the TREAD WIDTH and it is THAT MUCH wider.

RE040 225/45/18 tread width = 7.5"
RT-615 275/35/18 tread width = 10.0"

That's 2.5" in my book and that rubber on the ground! :D 33.3% more to be EXACT!

And it's markedly better rubber at that (Grassroots Motorsports 9/05 issue). I have no concept of Auto-X performance gain, but that is HUGE on a race track I would only imagine.

 

I'll have to call them, but the web site says "Lighter and less expensive than SSRs in this size at only 17.2 pounds for 9.5 inches wide and this special order from Enkei in the 45mm offset FITS all four corners of your RX8. "

...so at 1st blush they are apparently not the ones listed on the Enkei web site, which are heavier than they quote.

Yes the 17 are cheaper by a bunch - $101 per wheel/tire combo, but they are also about 4 lbs HEAVIER than the 18" combo as both the wheels & tires weigh more! Use pays your money and you get what you get... if in fact the 18s are as light as they say.

 

I don't believe the SSR Comps had the correct offset in 18x9.5 in order to fit. The Enkei is a special order since they don't normally make them in this offset either.
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nice...i always thought 17's would look to small for the car...but i guess you can just get a bigger sidewall....i just run my size also.. becasue the feed track rx8 runs the same size i have 18x9.5 with +35 offset....with 265 all around...sitcks out a lot buh i tend to want to run massive camber...right now im saving for my 18x10's or maybe 17x10's seemed to have found the right size and offset...maybe some 295's or 305's just to be the person to run the widest tire...now that i think of it tho..i reall see no point to run super wide tires if there is no power to behind the 8..i dont know tho....that rx8 looks hella nice tho..


gene