I've used Nitto 555R for many years and now it's time to replace the back tires (well, it's been time for a looong time).
So, I am looking at the options, what's new on the market, etc and I just do not get it:


let's look at the Nitto NT-01:
http://www.discounttire.com/dtcs/fin...r=50&tc=NITHZ8

Treadwear : 100
Traction : A
Temperature : A
Speed Rating : WR

and look at Riken Raptor ZR
http://www.discounttire.com/dtcs/fin...MPBHZ2&rf=true

Treadwear : 300
Traction : A
Temperature : A
Speed Rating: ZR

I don't even know anything about the second ones, but on paper, the last longer, are rated for a higher speed and have the same traction and this is the case for many many tires I see on the web.

So, saturday, I went to a local shop and talked with the guy there and we looked at his database, and, sure enough, in the db many thing seem much better than the nittos.
now, having tried quite a few different ones in the past, I haven't found anything remotly close when it comes to dry traction (for the street), so is the rating system flawed (by rating with A, B, C, etc) or is there something I don't get?

 

http://www.driveandstayalive.com/art...t_feb-2004.htm

 

This page explains the speed rating confusion.

http://www.tirerack.com/tires/tirete....jsp?techid=35


I don't go too closely in with traction and temperature ratings listed on the tire.. They are made for common tires.. I can't imagine any half decent performance tire(or any tire I'd put on any street/daily driver vehicle of mine) without a rating of A.. But there still is a huge difference between all of them.

 

I understand the basics of the rating system, but it seems to me that A, B and C is kind of pointless, while a number would make more sense.

For example if there was a standardized system where tires are rolled on a surface with a given weight/speed/pressure on the same surface and we'd know how much force it takes to loose traction, then it would be useful. Not so much as an absolute number but rather as a comparison mean.

That system means that anything that is acceptable would be rated the same way. If I say objects 'A' fit in the box, but objects 'B' don't fit in a box, I still don't know if object 1 is bigger than 2 if they are both 'A'.

So, in the end, I am looking to get same / equivalent / better than the Nitto 555R when it comes to traction, but the current rating system doesn't provide much meaningful information.

So, now to be more constructive:
does anyone have experience with the Nitto NT-01, the 555R2 or anything similar that they would recommend over the 555R ?

 

First, the traction rating it WET traction. This is off Tirerack, " UTQG Traction Grades are based on the tire's straight line wet coefficient of traction as the tire skids across the specified test surfaces. The UTQG traction test does not evaluate dry braking, dry cornering, wet cornering, or high speed hydroplaning resistance.

The Traction Grade is determined by installing properly inflated test tires on the instrumented axle of a "skid trailer." The skid trailer is pulled behind a truck at a constant 40 mph over wet asphalt and wet concrete test surfaces. Its brakes are momentarily locked and the axle sensors measure the tire's coefficient of friction (braking g forces) as it slides. Since this test evaluates a sliding tire at a constant 40 mph, it places more emphasis on the tire's tread compound and less emphasis on its tread design."

Want numbers? Well, there are number ranges assigned to the letters.
Traction
Grades Asphalt
g force Concrete
g force
AA Above 0.54 0.41
A Above 0.47 0.35
B Above 0.38 0.26
C Less Than 0.38 0.26

Temperature
Grades Speeds
in mph
A Over 115
B Between 100 to 115
C Between 85 to 100


It is just a matter of it taking less space for an "AA A" on a sidewall compared to stamping a range "Above 0.54 0.41 and Over 115."


Those Rikens aren't impressive as a street radial with an A wet traction rating which is the same as the Nt-01 which is a track tire. IMO, if I'm going to run an A wet traction rating then it better have a lot of soft rubber contacting the ground for excellent dry performance.

You also need to look at the tire characteristics. The NT-01 while it may not last as long, it will hook much better, handle much better, and improve braking. Yes tires affect your stopping distance too. In short, it will basicly take anything you throw at it performance wise. Thats not to say they'd make good daily driver tires either because they won't like the cold and most likely the rain either.

Now consider the Riken, it will be a hard tire that will spin relatively easy, the wet traction isn't impressive as discussed earlier, and it will be a limiting feature to your car's performance. You will never see your car's full potential with those hard tires.

So it comes down to a choice. A great performing tire that won't last as long and probably shouldn't be driven in adverse conditions or a hard tire that will wear well, and give mediocre performance at best. Or a comprimise of both learnig toward wich ever side think more important.

 

I did not realize (= I did not read carefully enough ) that these were wet ratings.

The Rikens were not an option, but rather to illustrate.

So it looks like I'll be sticking with Nittos again then (7 straight year!). Wet weather and cold are not a concern as I live in Southern California.

I am not sure what are the differences between 555R and 555R2; I had never seen/heard of the 'version 2' before. I think I'm going to go ahead and try the NT-01 and report to the board my experiences with them!

 

the r2 is a road racing tire while the r is for drag.

 

The "ratings" assigned to the tires are determined only by the manufacturer. There is very little monitoring of the ratings by any agency, so there tends to be an element of fiction in them.

Moving to "Wheels and Tires"......

 

Theres a local guy that runs NT-01s on hsi procharged c5 z06, he loves them to death, says their super sticky for a straight line, and can cut corners good too. Ive been wanting to pick up a set as well, but funding doesnt quite allow for that right now