eage8

iTrader: (9)

I realize... but his sidewalls are going to be quite a bit softer than a set of Victoracers. driving around on your sidewalls isn't terribly fun... He's not running pretty common track tires.

My intention was simply to help him in the right direction and recommend that he starts off chalking his tires.

(PS, my pressures were hot)

silverTRD

iTrader: (37)

the federal rsr's are not recommended for street use even though they are dot approved and do have a tread rating which is 140. just an fyi, that being said im still interested in them even for street use. lol

Valkyrie

^that's crap, they're street tires. I've been using them for most of a year, and I have put about 7-8 track days on them. I do need new rears though (it's an MR-2).

Valkyrie

Having the biggest possible contact patch is more important than having absolutely no sidewall flex.

Which is why using a pyrometer is something actual race teams do and why chalking tires is something that amateur autocrossers do.

eage8

iTrader: (9)

so your suggestions is for him to get a $100 pyrometer for his street tires?

unless you're checking your tire temps in pit lane, it's not terribly helpful. They cool down a good bit by the time you get back to where you're parked.

I have a pyrometer and didn't even bother using it, because they're street tires and it's not worth the hassle.

Here is a picture of my tire almost debeading at 30psi...
http://www.catesracing.com/flp/nasa/...1/IMG_6756.JPG

Josh18_2k

iTrader: (3)

you really cant just issue a blanket statement like "FD's want 30psi." Totally depends on the tire and camber. If you don't have enough camber, you will need more pressure. And every tire is different and requires different pressures. eg: V710's need 5-10psi less than A6's.

Most high performance street tires (140-200TW) need 32-38 (hot) with proper camber. If you have less than 2* up front, chances are that will be up over 40.

Mahjik

iTrader: (1)

And no one did. The statement was: "A good place to start is around 30 PSI."

Granted, should have added "cold" but seeing as the person posted the question is just learning, introducing hot verses cold didn't seem appropriate. I still contend that for the FD, 30 PSI is the place to start and adjust up/down based on whatever reading being used (pyrometer, chalk, butt, etc).

FWIW, on my M3 I use much higher pressures when it does hit the track. I wouldn't dream of running 30 PSI for anything on that car. As Josh mentions, there will be different settings for different cars, tires, suspension setups, etc.

rx7dreamweaver

iTrader: (2)

I had a set on my 350z, and hands down the most incredible tire i've owned. Incredible grip, very quiet, handled all the weather i threw at it, including tremendous amounts of snow. plus, stacked meaty look... i'll see if i have a pic or two. Had the guy I bought my FD from not just put on brand new tires, i'd be rolling a set again. Will when I put new rims on for sure.

lOOkatme

iTrader: (19)

Actually you are wrong here.

Its more important to have wide wheels with a stretched tire than it is to have wider tires.

Look at any car racing. They are fitting tires with a stretch in them. 245's on 9.5" width, 255's on 10", 265 on 10.5" and 295 on 11" width.

The stretch is the most important thing when it comes to handling of the car. They have noticed that running wider wheels regardless of weight drops times. Each 1" width increase has shown second faster lap times on minute-2 minute tracks. They have seen multiple second increased when going up inches in width.

Some people say that the wheel width should match the tread width or so, which is also a pretty good rule of thumb.

Here are a couple of articles to ponder.

URGE designs

http://www.cb-racing.com/PilotCup_Presentation.PPT (look at slide 34 and the few after)


Wheel Specs on a cup car for 2013


18x9.5 front, tire is 237MM or 9.3 wide
18x12 rear, tire is 292MM or 11.5 wide

set ups

Sierra Sierra EVO
Wheels/Tires 18x10.5 +22 Rays Engineering Volk Racing CE28N; 295/30/18 Ventus TD (C71 compound)

tread width = 10.5" on the 295" tire.

Revolution RX7
Wheels/Tires: Volk Racing RE30 18x9.5 (front) 18x10.5 (rear) wheels; Hankook Ventus RSS 265/35 (front) 285/30 (rear) tires
Tread width of the hankook TD below
265 = 9.5"
285 = 10.3"


I can't find a single team that races or sports car that handles well that puts a tire on the wheel which has a larger tread width then wheel width.

So the largest tire fitted to a wheel does NOT perform better. otherwise you would see it all over racing.

GoodfellaFD3S

iTrader: (213)

They're quality tires for daily driver duty.....but if you think they have incredible grip, you just haven't sampled the top tier of street tires that are out there---AD08, Star Spec, RE-11, and I'll even throw in the RS3 for the Hankook fanboys

Valkyrie

Durrr, I was talking about tire pressure, not wheel size.

lOOkatme

iTrader: (19)

Ok. my bad. I thought you were talking about having the widest tires possible.

The best set up I have seen in anything I have read, seen, felt is widest wheels with tires that are slightly stretched on the wheels.

BLUE TII

iTrader: (9)

Dollar for dollar, the Federal RS-R is an even better deal, and the performance is almost as good as any similar tire that costs twice as much.

the federal rsr's are not recommended for street use even though they are dot approved and do have a tread rating which is 140. just an fyi, that being said im still interested in them even for street use. lol

Dollar for dollar, the Federal RS-R is an even better deal, and the performance is almost as good as any similar tire that costs twice as much.

I want to post my experiences with the Federal 595RS-R since it has been brought up a couple times.

I put 265/35-18 RS-Rs on my FDs 18x10.5 wheels for my clubs first autocross points event 9 months ago.

I won the street tire award every single event.

I was in the top 5 for pax and overall points against miatas, Stis, EvoXs on autocross slicks (Hoosiers A6, Kumho V710, Hankook Z214 C71.)

They are $140 for the 265/35-18- very cheap for that size.

They are the longest lasting tire I have used for mixed autocross and street driving. They are now near the wear bars, but I am starting this years pre-season event this weekend on them.

They are my favorite tire I have used on the street. For a max performance summer tire they are predictable as they work reasonably in cooler temperatures and don't go to super hero grip when warmed.

They are not however a refined tire.

The tread splice always separates some leaving what looks like a gash across the tires surface.

They require lots of weights when new because they are so out of round/off weight. Once they wear down the weight is off. Its probably best to run these without balancing or rebalance once they are worn in.

They are loud.

They don't grip very well when the pavement is below 50 degrees, but much better than the Hankook RS-3 I used before.

Valkyrie

I don't disagree. OTOH, simply using low-profile tires with light wheels gives the same affect.

The difference in response and feel of stability between my 17" RS-Rs and my 15" snow tires is massive. And it's not just a matter of grip. It's all from sidewall flex.

lOOkatme

iTrader: (19)

I see a lot of people putting very wide tires on not as wide wheels, which doesn't give you the performance they think they are getting.

I see a lot of people putting 285's on 10" wide wheels. Most 285 tires are too wide for a 10" wheel.

If you want a stretch to the tire you want the tread width to be around the wheel width.

here are some tire tread widths off tirerack

255/35/18
RE-11 9.4" (9.5 or 10" wheel)
R-S3 9.5" (0.5" or 10" wheel)
R1R 9.3" (9.5" wheel)
AD08 9.9" (10" wheel)

265/35/18
RE-11 9.6" (10" wheel)
R-S3 9.4" (9.5" wheel)
AD08 10.3" (10.5" wheel)

285/30/18
AD08 11" (11" wheel)
Hankook TD 10.3" (10.5" wheel)
595 RSR 10.2" (10.5" wheel)

I just want to point out some tire sizes in 265 are wider/as wide as 285's. So people need to be careful when selecting tire widths and wheel widths not to overdo it. Just because you have a wider tire might not mean you have better grip and handling.

ringo_rx7

bumppppppppppp

Valkyrie

You might not have better handling (balance!!!), but for the most part you will almost always get more grip. Of course, if you use too small of a wheel your tire shop will either tell you to **** off, or they will HATE you for it.

That's assuming you are going fast enough to get and keep heat in the tires, of course.

But other than weighing too much and having too much drag for your power level, the only reason not to use wider tires and wheels is the rules, your fenders, and your budget.

lOOkatme

iTrader: (19)

Wrong, you will not have more grip fitting a larger tire on a wheel width that is too small. The mechanical grip goes down and so does the traction. If you do this on the front of the car you will end up with understeer, if you drop a tire size so you have a slight stretch, your mechanical grip goes up and the understeer will go away.

Grip goes down when you put a larger tire on a skinny wheel.

Valkyrie

^no it doesn't (as long as you're within the approved rim width range)

GoodfellaFD3S

iTrader: (213)

So a 275mm on an 11 inch yields more than a 275 on a 10? Please cite your sources

eage8

iTrader: (9)

every stock class autocrosser disagrees with you.

lOOkatme

iTrader: (19)

Look at any race team...look at spec miata's. look at the racing world and the wheels/tires they use.

They ALL run wheels wider than the tread width of the tire. The times come down and they run faster lap times.

So racers who have a 10" wheel CHOOSE a 255 or 265 width tire OVER a 275/285 width tire because it produces faster lap times.

Now I am not 100% sure that a 285 on a 10" wheel vrs. a 265 on a 10" wheel doing a skidpad what the actual peak limit result will be. I do know that racers all choose the 265 over the 285 on a 10" wheel.


I will challenge anyone to find me a time attack car, a lemans car, a porsche race car, etc, etc that runs a tire width wider than the wheel width then we can start arguing.

If grip went up by running wider tires than wheel widths and it were controllable, then racers would run that.

lOOkatme

iTrader: (19)

Yes, Where .5" increase in wheel width increases the tread contact patch by .2.


Straight from Yokohama
"The dimension that changes the most is the tire's section width—a change of about 0.2" for every 0.5" change in rim width."

Performance Tire Wheel Relationship | Yokohama Tire Corp.

Tirerack
"The industry rule of thumb is that for every 1/2" change in rim width, the tire's section width will correspondingly change by approximately 2/10"."

Tire Tech Information - Tire Specs Explained: Section Width


Michelin Engineers

"Bigger isn’t always better, both in terms of ease of driving and in terms of lap times.
Frequently, the tire looks “stretched out” on the application wheel, forming what looks to be a “trapezoidal” cross-section, with the tread width close to or less than the width of the tire’s beads. This is because of the simple fact that a “high-tension” tire shape is more efficient, in most cases, than a fat, “low-tension” shape."

www.cb-racing.com/PilotCup_Presentation.PPT


Grip is relative to handling..... and I am talking about grip in corners not straight away.

Valkyrie

You are confusing section width with contact patch size. Section width is how wide the whole tire is, which is relevant...in suspension and fender clearance issues. But it doesn't effect grip or handling. Only the sidewalls and contact patch do.

Bigger isn't always better, but using a wider tire does NOT decrease grip.

285s weight more, cost more, and require more space than 265s. There are plenty of reasons NOT to increase tire size, but there is only one reason to increase it: more grip.

Sometimes in a short race, it's more important for tires to quickly reach their peak operating temperatures and be as light as possible rather than having as much meat as possible.

What Spec Miata does and what F1 does is not relevant. Spec Miata is a tightly-controlled spec class and people will do ANYTHING that they (think) gives them an advantage that is within the rules. F1 is the world's most expensive sport and the tires used are not even in the same galaxy as regular racing tires.

Not to mention that handling is not as simple as weight and grip. The only real advantage that stretching tires gives is more response, which in some cases is advantageous, in some it is not. It's just one variable that can be changed to change how a car handles. In some cases too much response and not enough compliance means you lose grip (the car skates across the track).

The fact of the matter is that you stated that wider tires means less grip, which is false.

lOOkatme

iTrader: (19)

I agree that I mixed up section width and tread width the way I was quoting and reading it.

A wider wheel with a stretch effects the slip angle of the tire. The two largest effects on grip are pressure and slip angle. And from what I have read the carcass regidity increases with a stiffer sidewall effecting the efficiency of the tire and the grip.

The larger tire on a smaller width wheel (think 8.5" 255 width) has less carcuss rigidity and worse slip angles than a (8.5" 225 width). I don't know the exact grip difference between the two tires on let's say a skidpad test or a slalon test, but the times on a race track drop when using the 225 width tire on the 8.5" wheel than a 255 width.

So usable grip goes up. This is definitely seen when using a 255 width and moving from a wheel width from a 8.5" to a 10" wheel. You can get a negative effect if the wheel is too wide as it changes the shape of the tread and less contact will be had with the road.

I can't find any good answers to which has more grip, but I do know that just about all the professionally tuned cars run wider wheel widths than tread widths and have a slight stretch to the tires. I have also experienced this first hand myself when setting up my car.