nocab72

Looking to (reduce wheel spin & improve grip) both off the launch (on the street) and from a roll.

What is the real answer, I'm sure there are several things, probably all the below...

Is it wider tires?
Is it stickier tires?
Is it suspension setup?

Currently running a 18x9 SSR w/Toyo Proxy T1's. I got about 7k miles out of them and my rears are shot, little traction until I shift into 4th gear... Yes, 3rd breaks loose as boost builds from a roll...

I'm open to new rims (wider), tire suggestions, suspension suggestions, etc...

The car is an evening/weekend car, I don't take it out in the rain, but have been caught in it before. Put about 12,000 miles on it in the past year, so I definately get it out frequently and enjoy driving it (who doesn't)!!!

K

ptrhahn

iTrader: (9)

I recomend (and i'll likely be disagreed with) that you go a bit wider in the rear. If you want 18", try for an 18x9.5" to 18x10" minimum with a 275/35/18. Based on personal experience and that of my friend w/ 725 RWHP supra, DO NOT use the 285/30/18 most people recommend. I know the extra 10 mm is tempting, but the TINY sidewalls that might feel great while cornering will likely hurt your straight-line grip (you need a little flex!)... This was graphically demontrated to me on the above mentioned Supra... With 285/30/18 rears, the car slid around like it was on urathane skateboard wheels... a switch to 275/35/18 tires of the same brand made a WORLD of difference.

IF you are not married to 18" wheels, you could try 17x10" rears with 275/40/17 A032Rs... they're bearable on a weekend car from what i gather, and will be STICKY

I'd complement that with a 17x9" front w/ 255/40/17.

EricM

get 3.9 rear end and HKS Drag Suspension.

Or soft shock/spring in the rear.

RX7 RAGE

iTrader: (22)

Howcome you didn't go for an 18x10 setup in the beginning kyle?

nocab72

My car went from bone stock to 500rwhp+ in 10 months.

Back when I ordered these 18x9's from Rishie, I never expected to need more rubber than what would fit on them... (at the time I was barely putting down 300rwhp)

I went mod crazy this summer...

K

rynberg

I think ptrhahn has the best advice regarding the sidewall rigidity. Going 17x10 with 275/40 in the rears is probably the best option. Your speedo will be off a little bit but the taller final drive ratio from the taller than stock wheel+tires will also help with traction.

You should also talk with Jimlab to investigate rear end options. Your car would do much better with a taller rear end.

BTW, your car is simply a beast Kyle.

SleepR1

Kyle you need 10.5 x 18 rears with 295/30-18s, and 9.5 x 18 fronts with 265/35-18s.

Go with Fikse http://www.fikse.com/offsets.html Their offsets are ideal for FD Rx7 with 2.5-inch coil springs and M2 rear trailing arms...Offset for both will be 50.4-mm They look great in FM-10 or Mach V (Mach Vs are my personal faves)

Your ONLY TWO CHOICEs in tires will be Pirelli P-Zero Asimmetricos, and Continental Sport Contact 2s--both are Porsche original equipment N2 (OE rears for 996 Carrera and Carrera S). I've had experience with Pirelli Asimmetricos, and they are probably THE stickiest road tires available, and rival Kumho Victoracer/Ecsta V700, Yokohama A032R. I have no experience with Sport Contact 2s--they're new.

With 295/30-18s in back mounted on 10.5 wide, you'll put down nearly 12 inches of width (2-more than you have now). The 295/30-18 aspect ratio is slightly taller than 285/30-18, and the overall tire diameter is 25.1 inches, just about stock.

I can guarantee, that with a nice warm burnout, you'll launch nicely with 295s. The upshot is the above setup will work beautifully for road course work too

Act quickly, because, I've already given this advice to Ramon Ceron, who's hot on a set of Fikse FM-10s. He ALSO has a silver FD with a ported KD Rotary motor, and serious mods. Ramon doesn't have 500 rwhp, but he has PLENTY, and KNOWS how to handle that power too...(I know first hand--I rode with him at Road America as an instructor ) We did ~145 mph 3 times per lap, until his stock brakes finally gave up

Brad

I've searched and searched but can't seem to find the thread...but I remember reading an article about some engineer with a turbo charged 60's mustang. He was running the stock size tires...some **** like P215's. Ran 10.xx if I remember correctly. If not he was atleast in the 11's.

Anyhow, that thread had some information on how increased tire width gives negligible traction improvement. Only real thing that improves traction is tire compund. I do believe that article had hard test data to back up their claims too.

Not that it wouldn't help at all...but the difference between 255 and 275 isn't going to be much. And I wouldn't really want to go with the 295's, simply because the smaller sidewall. A taller sidewall will yield better grip than a tire of the same width and a smaller sidewall, not to mention ride quality is comprimised with a smaller sidewall. Not that we care about ride quality though

nocab72

oh...Rishie...can you hook me up?

K

jimlab

I'm going to take Manny's advice and get a set of 18 x 9.5s and 18 x 10.5s made with 7.25" and 7.75" backspacing, respectively. I'll go with the Continentals in P265/35-18 and P295/30-18, I think. $1,028 from the Tire Rack, shipped.

The Pirellis probably have a little better dry grip, but higher noise and lower wear, and less grip in the wet, just in case I get caught out. I also don't want to take the risk of sand blasting my new paint. The Kumhos I ran on my Supra were like glue. They picked up everything I drove over... sand... rocks... manhole covers... and bounced it off the side of the car.

SleepR1

Dude, get the AROs for the extra bling bling factor

http://www.fikse.com/images/aro.gif

My first choice is Mach V, but I'm more conservative than you, Kyle

http://www.fikse.com/images/machv.gif

ARO! ARO! ARO! ARO! ARO! ARO!

SleepR1

Although one-off Boyd's wheels will be pretty special

We need pics of these babies when you get them built, and slapped on the V8 monstrosity

vosko

iTrader: (4)

i need to switch tires soon too. 255/40/17 kumho 712's on my 17x9.5 do nothing.... lol.... need something a bit stickier. i will be checking this thread

Badog

Fikse, Kyle, Fikse! You know love my (5 year old) wheels!

<Click on the links in the sig>

lane_change

iTrader: (20)

Kumho 712's are like racing on buttered glass. Those tires are a nice cheap tire, nothing more.

Get some S-03 Poles and you will hook up much better.

ptrhahn

iTrader: (9)

I've heard mention of this as well. I'm not going to debate anyones science (I have enough engineer friends that i've learned not to), BUT, in reality (the only thing that matters to me) I can tell you that I switched from 17x8" SSRs w/ 245/40/17's all around to 17x9" w/ 275/40/17 rears of the same tire model and the difference was ENORMOUS. Some of it surely is the diameter but the result was unquestionably better straight-line traction. I changed the fronts at the same time to 235/45/17. I did not cause massive understeer as i hear suggested so often, nor did it royally screw up my gearing or speedo accuracy. I just wish integrals were available in 17x10" as the 9" isn't optimal for a 275.

Nocab, if you're gonna spend money replacing your SSRs, do yourself a favor and get large rear tires on properly-sized wheels. I don't think Vipers and Diablos and such would be equiped w/ 345-series rear tires if larger didn't help something; just like horsepower, every little bit helps IMHO.

houseofboost

I will agree that tire size can make a difference, but a guy has to take into consideration all the guys with the Outlaw 10.5" tire cars. They are running 4.80s in the 1/8th mile. Some even run DOT tires like ET Streets just for the 50 pound weight break.

maxcooper

I read that, too. It was a guy that works at Banks Engineering, and it was posted by RICE RACING (I think) in the single turbo section. However, the article says that you might gain 10% of traction from wide tires, which is certainly less than "double the traction for double the width" or anything like that, but it is still a 10% improvement. Going from 255 to 295 probably isn't going to give you more than a few percent, but it is still a few percent. The added inertia may reduce the "whoosh, there goes the tires" experience as well, even though that isn't a change in traction, per se.

Stickier tires to grip the road better, wider tires to put their contact patch down with less force wasted on tire deformation, tall sidewalls to absorb irregularities and further reduce force wasted on tire deformation, heavy wheels and tires with lots of rotational inertia to resist the run-away revs as they go up in smoke, larger diameter tires to make the effective gear ratio taller, etc. will all improve traction (or at least make you less likely to smoke the tires at 70 MPH).

Another way to improve traction: move to a warm, dry place.

-Max

Carl Byck

Best street compound, BFG TAKD, Best value Kumho V700, I may not have a lot of posts, but I've run Pirellis, SO3s, T1Ss, the TAKDs outgrip all of those by a wide margin IMHO. However the TAKDs cost nearly twice what the V700s do, so I run V700s on the street, as they last more than half as long as the KDs. My new set up on my FC will be 275-40-17 on 9.5" rims all the way around. (oh and some flares >) Carl

dclin

iTrader: (4)

No idea on how long these things would last you, and how exactly streetable these DOT 'approved' tires are, but might be worth a look:

Kumho Ecsta V700
http://www.tirerack.com/tires/tires....del=Ecsta+V700

specs:
http://www.tirerack.com/tires/Spec.j...del=Ecsta+V700

Michelin Pilot Sports:
http://www.tirerack.com/tires/tires....ilot+Sport+Cup

specs:
http://www.tirerack.com/tires/Spec.j...ilot+Sport+Cup

Kyle: Notice that 265/35/18s are only .1" and .2" taller then your T1S respectively. Might be an idea to try those on your current SSRs, rather then spring for new wheels and tires.

Jim: While these two do not have 295/30s like Manny suggests, they are available in 285/30. Notice that in the Michelins, the 265/35 (25.2") are shorter then the norm, and the 285/30 (25.1") are a bit taller then the norm - to where they are near identical in height. Greater difference between the two sizes in the Ecsta V700 flavor (25.1" and 24.6" respectively).

Seems the Michelin engineers guessed there may be some who might want to stagger the sizes front to rear.

I'm thinking of the Pirelli PZero Corsas:

http://www.motorsporttyres.com.au/t-club.htm

available in 265/35/18s and 295/30/18s and, which despite the list on this website, is available in 255/35/18s as well.

BTW, Tirerack does carry the PZero Corsas, though no idea as to why they are not listed.

You'll likely not be able to find stickier tires in 19s, as that there does not seem to be DOT comp tires made in these sizes (yet).

jimlab

I have no doubt that the difference was enormous, but not for the reason most people would think. Or would have suspected that I'd ramble on about it at such length...

I posted this very recently in my V8 thread...

"A P295 doesn't really offer any more traction than a P275 of the same tread design and compound, because the increase in contact patch is negligible, and the coefficient of friction doesn't change. In fact, a P295 shoved on too narrow a wheel can actually be worse than a P275 on a properly sized wheel, because the tread surface may cup away from the road surface.

What is often mistaken for increased traction with wider tires and wheels is that the new combination weighs more, and the engine may not have enough torque to break them loose as it did with a lighter, narrower combination."

In '97, I did the same thing that you did. I moved up to a P265/40-17 (same brand and style) on a 9" wheel (same brand and style) from a P245 on an 8, and it cured my traction problem in 1st, 2nd, and sometimes 3rd. The tires were no longer breaking loose at the "top" of gears (higher rpm) where I was making the bulk of my power. At the time, I thought it was because I now had "more rubber" on the road with the wider tires.

However, after reading a few articles along the same lines as what GotBoostd7 posted, and in my research in the last year or so on traction and gearing, I now know that my new-found traction was simply the result of increasing the weight of the tire and wheel combination to the point that the engine was no longer making enough power to break them loose.

A simple way to demonstrate this is to tie a small rock to the end of a piece of string and swing it in a circle. It doesn't take much to start it rotating or keep it in motion, right? Now tie a brick to the end of another piece of string of the same length. Assuming the string is thick enough so that it doesn't break, it's not so easy to get the brick started and definitely takes more effort to keep it in motion. How about spinning it even faster? Now increase the length of the piece of string. Has your arm turned into Jello yet?: )

Obviously, it takes a lot more power to get a larger mass at the circumference of rotation moving, to keep it moving, or to accelerate it, especially when you increase the distance of that weight from the centerline of rotation.

This is why "plus-size" aftermarket wheels and tires can effectively kill the acceleration of underpowered cars like a stock Honda Civic. Not that they had a lot in the first place. The engine doesn't make enough power to rapidly accelerate the heavier wheels and tires, and certainly isn't going to be breaking them loose. Try a standing burn out with a combination like this, and you'll probably just burn up your clutch.

The more you increase the weight of the tire and wheel combination and the farther you move that weight from the axle centerline, the more power it takes to accelerate that mass faster than the available traction will allow. However, you can easily have enough power that no increase in tire/wheel weight or width will have a chance of harnessing all of it.

Top Fuel dragsters use an 18.5" wide slick because of class regulations to limit traction. They have to screw the tire to the rim to keep it from flying off, and it can grow to half again its static diameter during the burnout and at the far end of the track, and distort until it's almost square. If a short stomp on the throttle simply annihilates the tires, then how do they get down the quarter mile? Part of it is that they're only transferring about 16-17% of their power on the starting line with an adjustable clutch pack setup, and they don't even reach full lock-up by the end of the quarter mile. But more importantly, the distortion of the wrinkle wall sidewalls of the slicks vastly increases the contact patch of the tire under power. Far more than what any shorter slick could accomplish, and of course an infinitely larger contact patch than any street tire. They're also pretty gooey after the burnout.

Bottom line, if you can't significantly increase the tire's contact patch or find a stickier compound to gain traction, you can increase weight. At some point, though, you can easily overpower any combination of wheel and tire that could fit on the car, and at that point, you'd better get really good at gradually feeding in power (like the adjustable clutch packs mentioned above) and/or invest in traction control.

Wade

iTrader: (1)

I have to disagree with the majority here. You need to keep larger sidewalls and don't go with a low profile 18" tire. You also need to get the best compound possible, and accept that when the road surface is cold you aren't going to get good traction. Our cars squat quite a bit on accel and I'd bet that a really wide, low profile tire loses major contact area when the car squats.

Get 18x10's and I'll bet your traction problems will be worse. My suggestion is to try 17x10's and A032Rs. You might even want to try some friends setups before dumping a bunch of cash and possibly not fixing your problem.

Wade

ptrhahn

iTrader: (9)

Given the above, let me propose a theoretical test to help me understand:

You have two 17x9" SSR rear wheels. Both weight the same, lets assume 18 lbs.

You mount a 235/45/17 S0-3 on one rim. 9" is within the approved range for this tire, and its diameter is 25.3". Weight is 27 lbs for a total of 45 lbs.

On the other wheel you mount a 265/40/17 SO-3. 9" is within its approved range as well. Its diameter is the same: 25.3" Weight is 29 lbs, for a total of 47 lbs.

The only variable that has changed is 4.4% weight increase for the 265 (and of course the width, which supposedly doesn't matter)

Even the fact that the 235 is mounted on the widest approved width wheel (and therefore will likely perform its best), and the 265 is mounted on the narrowest approved width wheel (and will likely not perform optimally), why am I not buying the idea that if you were to mount this combo on the rear of your car, you wouldn't have a serious imbalance, even if you were to add 2 lbs. of tire weights to the 235?

nocab72

This is great stuff guys! I'm really confused now...keep going...eventually I'll catch up...

K

Resource

I dropped my 18's and went with 17's with Nitto 555R'S. I get great traction on the street with a nice warm burnout of course