Z/28: Let's Talk Tires!

[Norm Peterson]

Originally Posted by kramard

305 98Y Sport Cup 2 $1,472 - not sure what the difference is between the 102Y but has the same treadwear rating.

Rated load @ pressures above 35 psi, 102XL vs 98SL.

Directly from an engineer currently (or at least formerly) employed by a major tire mfr (he won't say which one). Hope it helps.

Extra Load tires have the same physical dimensions as Standard Load tires (commonly abbreviated "SL"), but have higher load carrying capacities due to the higher pressures, and are constructed with slightly stronger materials to accommodate the additional stress caused by both the additional load and pressure. I should point out that Extra Load tires (commonly abbreviated "XL") have the same load carrying capacity as SL tires at the same pressure. It is a common misconception that XL tires must therefore have better performance than an SL tire, but in fact they would perform worse because they are thicker and would hold in more of the heat generated. But this difference is so very slight that it really doesn't make much difference. (What I am trying to say is if you don't need XL tires, then don't pay the extra money for them.)

Norm

[kramard]

I decided to try the 295 r888r. I think they look great for 295s - the rims are fuller than the 305 conti DWs by a fair bit. I just took them out for a 30 min street drive - initial impressions as follows:

- Steering is razor sharp, more feel than the trofeos for sure. I do have a track alignment (-1.6 upfront)
- cold grip - absolutely more than a cold trofeo
- tramming - doesn't appear to be any - felt a few grabs at low speeds around town but no issues on the highway. Can easily drive with one hand.
- loaded up - I loaded it up 7 - 8/10ths on a uphill slightly cambered onramp and they felt great. Started to feel a little bit of slip angle (2 - 3 degrees?) and the rear didn't feel twitchy at all. I'll be able to compare my lap times from the trofeos, conti DWs and R888rs this weekend to provide more data on grip. I don't want to screw around with going for high lat gs on the street.
- Diff - oddly my diff is much quieter with these tires. My diff was very noisy with the trofeos, somewhat noisy with the Conti DWs and almost no noise with the R888R. No popping sounds in my short drive around town in locations I normally get some popping with the DWs and noticeable noises with the Trofeos.
- Stickyness - it doesn't appear to throw rocks like the trofeos; it'll still absolutely destroy and unprotected quarter but in street driving it didn't seem to be as bad as the trofeo. Can't comment on how they are when hot yet. BUT, and this is a big but - I did a few small slides on u-turns to see how the rear behaves and this tire doesn't leave rubber on the road like a trofeo. I'm sure they will be slower on track, without question.
- Ride harshness - it is firm; as firm or firmer than the Trofeos
- Tire noise - it's loud, the road noise itself is very quiet but the whirl of the tread blocks becomes obvious at 60, loud at 70 and as much loudness as I can tolerate at 75. This tire may not be the best choice if noise bothers you. Tires are surprisingly loud under braking around town as well (whirl increases 1.5 - 2x under normal braking).

I can post a few pictures of the front and rear. We'll see how the wear goes and see if this is an acceptable solution for "cheap" track work. I was out the door at 1311 with mounting balance shipping and tax. Its an experiment... we'll see how it goes! With respect to look, I'm not put off at all but I also don't really "see" stance. I can tell when something's uber stretched or full but the in between stuff I just don't see as well as other folks.

[POINTBY]

I tried to find a reference to someone using Sport Cup 2 tires in here, but didn't see it. Has anyone? If so, is the 98Y load rating tire okay to use for track use?

Furthermore, the load rating sticker inside the driver door just lists "Y" and does not state 102.

102 load rating is 1,874 per tire for a total load capacity of 7,496 lbs! Why on earth would we need that kind of load rating?? Does the Z create that much load on track? If so, damn this car is a monster! :-)

The 98 load rating is 1,653 per tire for a total load capacity of 6,612. And according to our GVWR inside the driver door we are only carrying 4,581 (but track loads definitely increase this!).

P.S. - as a side note, my Z just arrived earlier this week and only had 20 miles on it. And I plan to break it in per the book (1,500 miles). I just purchased a set of Michelin Super Sports in 305/30/19 in the 102Y load rating. This should be a great street tire to enjoy the car at low speed while breaking it in. Then I plan to take the car to the track with these and "finish them off" then switch back to the Trofeo Rs. I just feel it's a waste of a top shelf tire to leave the Trofeo on for break in miles.

[s.hammer]

I do know someone that is using them on track, he picked up a set over the winter when Tirerack had a sale on them. They seem to handle track duty ok, and seem to handle more heat cycles than the Trofeos, however, he is going to try NT01s next.

[Norm Peterson]

Originally Posted by POINTBY

I tried to find a reference to someone using Sport Cup 2 tires in here, but didn't see it. Has anyone? If so, is the 98Y load rating tire okay to use for track use?

Furthermore, the load rating sticker inside the driver door just lists "Y" and does not state 102.

102 load rating is 1,874 per tire for a total load capacity of 7,496 lbs! Why on earth would we need that kind of load rating?? Does the Z create that much load on track? If so, damn this car is a monster! :-)

That 1874 lb load rating is good only at 42 psi (the maximum pressure in the table for load vs inflation pressure for XL tires). At 35 psi a 102 XL tire is rated at only 1609 lbs.

Maybe to some extent this big load rating is an artifact caused by today's bigger wheels (meaning anything bigger than about 17), some need for width (appearance and durability at higher performance), and also for sidewall height (ride considerations, and perhaps there's some need to keep the outside wheels from scraping on the ground if the tire was to roll under in an extreme cornering situation).

On edit - I think that Camaros in general having this much tire load capacity was one of JusticePete's beefs a few years ago.

The 98 load rating is 1,653 per tire for a total load capacity of 6,612. And according to our GVWR inside the driver door we are only carrying 4,581 (but track loads definitely increase this!).

Any cornering load will. A 1g corner will add something like 1300 lbs to the outside pair of tires (assuming a 20" CG height and a 64" track). So take half of 2100 lbs and half of 1300 lbs and you've got occasional loading up around 1700 lbs. This isn't sustained for long, but it does last longer than momentary loads like hitting a small bump in the road. Guessing that 1.5g isn't impossible for a Z/28 on Trofeos . . . not when MPSS peaks at over 1.25g once fully warmed up on the track . . .

P.S. - as a side note, my Z just arrived earlier this week and only had 20 miles on it. And I plan to break it in per the book (1,500 miles). I just purchased a set of Michelin Super Sports in 305/30/19 in the 102Y load rating. This should be a great street tire to enjoy the car at low speed while breaking it in. Then I plan to take the car to the track with these and "finish them off" then switch back to the Trofeo Rs. I just feel it's a waste of a top shelf tire to leave the Trofeo on for break in miles.

I'd seriously consider keeping the PSS for the majority of your street driving and dedicate the Trofeos to track & autocross level activities. No sense heat-cycling the goodness out of them even slowly by using them at no more than barely a quarter of their potential.

Never mind the possibility of getting caught out in the rain, where the MPSS is one of the best choices you could make if it's raining on your track day.


Norm

[POINTBY]

Thanks for the reply, Norm!

[tylerio]

I've run Yokohama ADO8R, Bridgestone RE-11, Michelin PSC2 and Nitto Nt-01s. I DD and track my car. The Nittos and the PSC2s are superior on the track. The Re-11s are good for street, decent in rain and cold. The Yokos were slightly better on the track then the Re-11s, but no match for the PSC2s and Nitto Nt-01s. I have two sets of rims. On one set I have the track tires (PSC2s now) and on the other set I have the Re-11s for the street. The RE-11s are quiet and there is little to no tramlining.

[JusticePete]

Originally Posted by Norm Peterson

That 1874 lb load rating is good only at 42 psi (the maximum pressure in the table for load vs inflation pressure for XL tires). At 35 psi a 102 XL tire is rated at only 1609 lbs.

Maybe to some extent this big load rating is an artifact caused by today's bigger wheels (meaning anything bigger than about 17), some need for width (appearance and durability at higher performance), and also for sidewall height (ride considerations, and perhaps there's some need to keep the outside wheels from scraping on the ground if the tire was to roll under in an extreme cornering situation).

On edit - I think that Camaros in general having this much tire load capacity was one of JusticePete's beefs a few years ago.

Any cornering load will. A 1g corner will add something like 1300 lbs to the outside pair of tires (assuming a 20" CG height and a 64" track). So take half of 2100 lbs and half of 1300 lbs and you've got occasional loading up around 1700 lbs. This isn't sustained for long, but it does last longer than momentary loads like hitting a small bump in the road. Guessing that 1.5g isn't impossible for a Z/18 on Trofeos . . . not when MPSS peaks at over 1.25g once fully warmed up on the track . . .


I'd seriously consider keeping the PSS for the majority of your street driving and dedicate the Trofeos to track & autocross level activities. No sense heat-cycling the goodness out of them even slowly by using them at no more than barely a quarter of their potential.

Never mind the possibility of getting caught out in the rain, where the MPSS is one of the best choices you could make if it's raining on your track day.


Norm

Norm,

I am convinced that the tire size created the load rating. By that I mean the load rating on a tire of the size used on the Camaro is very high, reflective of the tire size and not based on need.

Off the record, every tire company I spoke with thought the load rating on the door sticker was 'artificial' being politically correct.

[DavidCorsaro]

Originally Posted by JusticePete

Norm,

I am convinced that the tire size created the load rating. By that I mean the load rating on a tire of the size used on the Camaro is very high, reflective of the tire size and not based on need.

Off the record, every tire company I spoke with thought the load rating on the door sticker was 'artificial' being politically correct.

This. The size and construction of the tire itself is rated for a maximum load capacity, not inherently dictated by or for a specific vehicle application.

[JusticePete]

Originally Posted by DavidCorsaro

This. The size and construction of the tire itself is rated for a maximum load capacity, not inherently dictated by or for a specific vehicle application.

Correct. In this case, it appears the door sticker for tire specifications transferred the information from the tire to the vehicle creating an artificially high tire load rating for the 5th gen Camaro.

[POINTBY]

Originally Posted by JusticePete

Correct. In this case, it appears the door sticker for tire specifications transferred the information from the tire to the vehicle creating an artificially high tire load rating for the 5th gen Camaro.

With this said, would you hesitate to buy the cheaper Sport Cup 2 tire at a 98Y load rating? It's $380 per tire ($100 cheaper than the Trofeo) vs $520 for the 102Y version.