Tire size question 285 or 305 for my power level?

[CammyTheCobra]

Currently I have 285/35/18 in the back with Sumitomo tires. Not sure which ones, but they suck and are awful. Shifting from 1-2 it'll spin, 2-3 spinsish, if I make a run I leave traction on, slows me down, but I'm a bit scared of this car. First Cobra, it also drives like its skating on ice, as I get into 80+MPH under hard acceleration. I'm switching to the bilstein HD front struts, rear shocks. Still need tires. I'm probably grabbing NT-05r. This car doesn't see rain, winter, only sunny, dry pavement. So rain isn't an issue with tires. I have 4.10's in my garage waiting to be installed, with a full H-Piped exhaust and when money permits mail order tune.

Basically, will 285/35/18 NT-05r's be enough to plant the power I have, without spinning and scaring me shitless? Or should I go to 305/35/18? I'm just curious if the 305 is overkill for my power level or not. Thoughts and opinions and thoughts? I'm still getting adjusted to this power level, and it's just factory with soon to be gears and mail tune. I guess I don't wanna be worried about shifting from 2-3 under hard acceleration and spinning into a crash. Maybe I'm being over worried, maybe I'm still new to this car or power levels. I also over worry at times. Any help advice is very greatly appreciated.

 

[01yellercobra]

Going with a real tire will make a world of difference. The Sumitomos are horrible. I had sumis when I put my Vortech on and under acceleration my car would change lanes.

As for tire width, get the correct width for whatever rims you're running. I'm only on 17's, but I run 315s on a 10.5" wide rim.

 

[soccerman002]

285's will be fine - as said, it's more important to get a good tire that is sized properly, rather than just throwing wide meat on for the hell of it.

 

[CammyTheCobra]

They're 10" deep dish FR500 for the rear. I believe 285 are the max, is that true? Or can I fit wider? I've looked up lots of different opinions some say max 285 on 10" wide, others say they run 305 and even 315 no problems.

Do you guys think the Nitto NT-05r tires at 285 will be good enough to plan power for gears, exhaust and tune?

Side note, these sumitomos are seriously awful. Hard acceleration is bad, just pulls and is scary. I guess once I toss on real tires it should be better. I just don't want to buy 285 regretting going to 305

 

[Dirks9901]

So this is a stock 01 Cobra?

I can understand spinning a little from the 1-2 shift but 2-3 should be a chirp at best.. If this car is stock, you are making 280-285 rwhp at best. When my car was stock, i had 0 issues on the street/track and that was on crappy 245 fuzion tires.

 

[CammyTheCobra]

Yeah as far as I know. It has a full exhaust, with o/r H pipe. I picked it up from a guy 5 months back. He couldn't tell me anything, which is fine, I wasn't worried. But he said its 100% stock, yet I find out it has a full exhaust when I had it on the lift inspecting it, before purchase. I didn't even tell him about the exhaust, this dude was clueless, late 50's, had a vette too. Now, keep in mind, I have 4.10s waiting to go in, haven't had time to install them, due to work. I do think the suspension is shot though and is part of my hard acceleration issues, coupled with the shitty tires, so that could play into it a bit. I know what they come with stock for power, that's why I'm a bit thrown off. Maybe these sumitomos are that bad?

 

[JCP281]

Sounds like youve never had a car with any grunt at all. These Cobras in stock form are pretty tame. Choose any 285 width tire from a reputable tire company and you will have plenty of grip. I have 4.30s and 275's square stanced on some 03-04 cobra wheels and it is plenty of tire for the car. Your going to spin the tires with 4.10s, but you have to drive the car smart. Dont just hammer the pedal down and expect it not to spin.

 

[01yellercobra]

Maybe these sumitomos are that bad?

Yes.

 

[CammyTheCobra]

@JCP, yes prior car was a 96GT with tune, full exhaust, gears. So I haven't had a car with this much grunt, you're 100% accurate.

I've decided upon the NT-05 non radials. I was going to go with 555r, but after searching on these forums, I concluded for 10$ more a tire, the non radial NT-05 grips better than the 555r will. I think NT-05r will be overkill for what I'll be putting down come next year. Unless someone think the NT-05 isn't a good move over the 555r, but reading through these forums, the census was, that the NT-05 grips better than a 555r and the NT-05r is probably best suited for when I've got more than just bolt ons.

It's sort of funny, because I know a great deal about cars, but that knowledge is worthless to me, when it comes to driving an actual higher powered car, with little to no experience, and crappy tires to boot.

 

[01yellercobra]

I think you would be ok with a decent street tire. The NT-05 should be fine. I haven't run them, but know people that have and they like them. I've run the 555R on two vehicles including my current 04. The 555R "should" grip better going by the tread wear rating. But you don't need a drag radial at your power level. When I had a bolt on 01 I ran BFG KDW's with no issue. I would've stuck with them, but they couldn't hold the power with the Procharger.

 

[CammyTheCobra]

Good to know. I didn't think I needed a radial, but I play on the safer side of everything. However, just going through this forum and a few others, the general opinion from people was that the NT-05 (not the radial 05r), grips better than the 555r, which is a radial. People's opinion were pretty much the same after a good couple of days of browsing, that the 555r is not as good for grip, as the non radial NT-05, better compound apparently. Which I guess makes sense, since it is more pricey than a 555r. But is a bit contradicting to me, being that the 555r is a radial and the NT-05 is not. However, everyone says the same about the wear rate in the 555r, in which is a solid tire for the money and what it is. But if people think the NT-05 grips better, who all have way higher powered cars than I, I am gonna give them a whirl.

Thank you for the input all around guys. Definitely helped me figure out what to get, and sizing accurately for what my car would need for its power level currently.

 

[01yellercobra]

Quick FYI, all tires are radials. It's in the construction. I'm assuming when you say radial you mean drag radials. Since slicks are usually a bias ply design. So both of the NT-05's are radials. But one is a softer drag radial and the other is a normal street radial. Like I said, I've never ran the NT-05 in either variations. But my 555R's gripped just fine with my old set up. And that was around 650ishrwhp. They still spin a little on my 04 when they're cold.

 

[CammyTheCobra]

Yeah I know they're all radial tires. I work on cars, to be go honest, I just didn't feel like typing drag radial each time, and figured people would understand what I was saying (when I mentioned the 555r), which you did, thankfully. Appreciate the heads up nonetheless, better to inform and educate than assume otherwise. But yes, I am very aware all tires are radials.

I have been reading up about slicks, and their bias-ply design. A mechanic doesn't tend to come across that stuff, unless you're in a specialized area, which I am not. I do all types of car repairs, electrical diagnosis & repair, motor rebuilds, some driveline replacement and diagnosis , except transmission rebuilds. I don't mess with transmissions, my knowledge of them isn't good.

Let me ask you something, if you were me, what would you buy? The 285/35/18 555r or the NT-05? Rain isn't an issue for me, I have another vehicle. But, if you researched and found most guys thought the regular NT-05 was rated better among people, over the 555r would you buy it, or just grab the 555r because it is an actual drag radial?

 

[01yellercobra]

I'd run the regular NT-05. I only run the DR because I have to. I've had bad experiences with boost and regular street radials. I still remember looking out the passenger side window when getting on the freeway after installing my D1.