Tire Size Advice

[skovensky]

Hey everyone getting to the the tire stage on our build and having some trouble finding what would be best. We hallibrand replica wheels 17x9 in the front and 17x10.5 in the back. The car will mostly be used for road driving in good dry conditions and not planning to take it to a track. I have found a few good options from theses posts and I was wondering If you guys had any suggestions on tire size or brand. I was looking at either the Toyo R888 or the Nitto 555R in with the fronts being 255/40 and the back 315/35. Thanks for the help everyone.

[BEAR-AvHistory]

Have NITTO 555 255/40R17 94Z in front & 555R 315X35 out back. It is NOT recommended to run 555R on the fronts by NITTO. That said if you are interested in s 555R for the front have a unused set of 245's available. Were for my 335is which was sold before I got to use them.

[Avalanche325]

Most people are running 245/45 front and 315/35 rear. Some do 255 or even up to 275 in the front. Over 245 then may stick out and / or rub. Generally the 45 in front and 35 in the rear gives you very close to the same diameter. Manufacturers vary.

The Toyo R888s are autocross / track tires. Notice the "R". The tread wear rating is 100. The SCCA considers anything under 200 (was 180) to be a "track tire". That doesn't mean a real race tire, BTW.

The Nitto 555R is a drag radial and meant for rears only with the 555S on the front. I , personally, would not run drag radials on the street. They are meant for one thing, and turning is not it. Which is exactly what a Cobra is designed for.

Popular choices right now are Khumo Ecsta XS, Nitto NT05 are also popular. The Khumos are 180 on the tread wear, so right on the street / track border. Not sure of the numbers on the Nittos.

I am DEFINATELY NOT trying to talk you out of sticky tires. You need every bit of traction you can get in one of these. But, you don't want to buy new tires every 4000 miles either.

[Jeff Kleiner]

I've always used 255/40-17 in front on both my own as well as roadsters that I've built for others. IMO the 245/45 is a little stretched on a 9" rim. Given your stated use I'd recommend the Kumho XS if you can get them (they have been out of stock/backordered much of the past 24 months). I ran 3 sets and like 'em (currently on Nitto NT-01s). A couple things to know and keep in mind regarding the XS which will be applicable to many of the ultra high performance tires; they don't grip especially well below ~50 degrees or in heavy rain. Be conscious of these limitations and drive accordingly. If the XS is unavailable the Nitto NT-05 is a viable option with slightly less dry grip and next down the ladder is the Nitto 555.

Good luck,
Jeff

[nsxtasy]

Yup. You definitely don't want to use drag radials like the 555R. Drag radials are super expensive and wear out VERY fast. They are designed for going in a straight line at the dragstrip. In addition to supersticky soft rubber, their design features include reinforced sidewalls, enabling them to deform so that drag racers can use low tire pressures, maximizing the "contact patch" (the area of the tire in contact with the ground).

You also don't want to use track tires like the R888 or NT01 for the street. As noted above, they wear out VERY fast. They're also usually very expensive. They're great for the racetrack, for experienced racers who can take advantage of their capabilities. But some of their characteristics make them less suitable for street use. They give very little warning before losing traction. And they're designed so they reach maximum traction when they get hot, which they do on the racetrack but won't do on the street.

Fortunately, tire makers now make very very sticky street tires, with excellent traction for street use; the Tire Rack calls them "extreme performance summer tires". The Kumho Ecsta XS, mentioned above, is one of these, and is available in 315/35-17 for the rear as well as 255/40-17 (or 245/45-17) for the front. That would be an excellent choice for a street-driven Factory Five, for anyone interested primarily in the maximum performance from their tires. One downside, the Kumho XS is only so-so on wet pavement, so take it easy when it's wet. And like all summer tires, it shouldn't be used in snow or in frigid temperatures.

HTH

[CraigS]

The kumho XS is an excellent tire but their availability over the last 3 years has been a real problem. I wouldn't buy them just for that reason. Re: size. I wouldn't even consider 245. I prefer 275 myself but can maybe see 255 although I have never bought any.

[skovensky]

Hey Guys, this is really helpful advice and I am so glad I reached out. We are going to try to find the Kumho XS and if that doesnt work we will look for the NITTO's.

Thanks so much for the help!!

Stuart

[BEAR-AvHistory]

The NITTO 555R in 315 are $205 each with a wear rating of 100. They will wear quicker than an XS with a Price of $280 & a wear rating of 180, but they are available all the time & not outrageously priced. Think tire wear is a non event on cars which don't have a roof for 365 day driving or on any brand summer tires that don't do well when it gets cold. The 555R is DOT approved for the street with a semi-racing construction.

Can be a debate on drag radials for a street driven sports car but I have been happy with them. If anything 99% of the street driven replicas will easily overpower their tires in a straight line. Could be wrong but the fact that they are carrying well under their designed weight may help moderate the sidewall issue. YouTube has a lot of high powered short wheel base cars doing very bad things on launch & 1/2 shifts when they break traction.



Think this kind of problem is more likely than a sidewall problem.

IIRC Tire Rack has a few XS in stock right now $170/255 & $280/315 Were long time backordered when I needed tires.

[skovensky]

Kevin, thanks for the advice. Heading to Tire Rack website now to see what they have.

Stuart