emptnest

I do intermediate to advance (depending on the track) HPDE, driving a 1993 Z07 C4, with stock engine. The car has J55 heavy duty brakes, brake cooling ducts, heat shields on the brake pads, and Motul 600 fluid.

I have been driving on 275 wide Nitto NT05's.

Tires are currently my limiting factor, and I take them to their limit. That's why I am planning larger and/or stickier tires.

I am pretty patient in terms of progressing to new levels of performance. That's why my engine remains stock. The car still has more speed to be found through tires, brakes, suspension, new driver skill, etc.

Plus, I don't want all the stress, wear, and tear that ultra sticky tires will cause.

I know that I would have more tires to choose from if I used 18 inch tires, but I have about 5 sets of 17 inch wheels, so 17 inch square is what I'm using this year. So my choices are Nitto NT05 in 200 twr, or Nitto NT01 and Toyo 888 in 100 twr.

I plan to start the season on 315 NT05.

Or would 275 NT01 be a better (more gradual ) step, instead of a 315 NT05 to start the year?

My choice of the 315 NT05 is based on this:

I expect similar grip from the 275 NT01 vs 315 NT05, but longer life out of the 05's. Do you agree?

I'm not racing, so if the 05's are a couple seconds slower, but last longer that's fine with me.

TrackAire

I think one question that needs to be answered is what width are the wheels you have available? Regardless if you go NT-05's or NT-01's, using too wide of a tire on too skinny of a rim will give you very disappointing performance. Steering feel and at the limit handling can be compromised and actually make the car slower. Also, limited horsepower means that a bigger tire will weigh more and make the cars acceleration more sluggish.

I know on my track Mustang which ran 17" x 9" wheels square, the car was faster with 255 NT-01's than with 275 NT-01's.....but it did look better with the 275's, lol.

On my C5 Z06 with 18" x 10.5's square, the car feels more responsive with 295's vs 315's square.

Your car is pretty light, so without added HP, upgraded suspension & brakes and possible aero upgrades, not sure the super big tire is going to make that much of a noticeable difference.

It'll be interesting to see what the more hardcore track rats and racers think when dealing with a car as stock as yours.

emptnest

Wheel size will be correctly matched to tire size:
9.5 for 275
11.0 for 315

i have already test driven the 11/315 combo to confirm proper clearance. I was surprised by how much more responsive the steering felt. Steering pump and rack are currently being rebuilt and upgraded by Turn One, so they will be ready for the extra load if I go with 315.

For brake pads, with the 275 NT05 I ran Carbo tech XP 10 and XP 8 front and rear respectively. With either of the new tire choices, I will step up to XP 12 front, and XP 10 rear.

FASTFATBOY

Try the Falken RT 615K, better than the NT05 but not as good as the NT-01.

Also PSC is a good place to have steering pumps revalved, usually $100.

I ran the 275 NT-05 for 3 years on a z28 for track duty and loved them.

The 315 should be quicker in the NT-05.

Tomswheels

The 275 NT-01 is much much much faster than the 315 NT-05 not just because of compound, but because of sidewall stiffness. The two really aren't even in the same league. Expect to pickup a full 3-5 seconds a lap using the NT-01. I think you will find your driving improves as well when your sidewalls stop squirming beneath you.

emptnest

what is your experience with their relative durability? Will the NT01 last only half as long as the NT05?

Tomswheels

I honestly don't know because I took the NT-05s off and sold them way before they were worn out.

brkntrxn

I suggest going to the NT01 or the r888 in a 275. Not only will the tires corner, brake, and drive off the corner better than an NT05, but your straight line speed will not suffer because the tire will weigh similar to the 275 NT05 versus a 315.

ponycar

I was under the impression that the C4 wheel bearings will not handle many track days on street tires without failing. I would think the R Comps would put undue stress on the bearings. One of the guys I run with,( very fast racer), went through a set of wheel bearings every weekend or two. Any of you folks have an opinion on the potential issues with this move?

brkntrxn

On C5s and C6s, we use SKF hubs with ARP studs. SKFs last several years of hard racing on Hoosiers before starting to go bad.

Are SKFs, or something similar, not an option on C4s?


-Kevin

SunnydayDILYSI

275 R888s and NT-01s will noticeably outperform any NT-05 you put on your wheels. The NT-05 simply cannot handle the heat when driving at the limit. As you progress, you'll find that even the R888s can only last about 10 min before they get greasy... and then you're looking at Hoosiers. That said, each of these steps will impact "all the stress, wear, and tear that ultra sticky tires will cause." No way around it. If you want noticeable additional grip from a new tire, your car will notice it as well in terms of more wear and tear.

As a side note, I actually have more fun over driving, sliding, and fishtailing my C5 around the track on "greasy" spent tires than I do setting personal bests on fresh Hoosiers...

Rob31

Go get some 315 r7 or A7 scuffs on 11 inch wheels , you will never go back to a street tire .

emptnest

Can anyone quantify (even anecdotally) how the NT01 will wear vs the NT05?

i know the simple answer: the 01 will wear faster.

But how much faster ?

strano@stranoparts.com

There is a solution to C4 hub issues (rebuildable and serviceable too). Hoosier Performance Engineering makes a hub kit for those with real bearings. I carry it.

Tires. Wider vs. more sticky. Uh, both. Depends on the tire if you get crazy about it but I'd typically prefer a sticky 275 over a not sticky 315. Think of it like basketball shoes. If you made guy with size 13's play in some not great shoe his grip and traction will be less than the dude wearing size 9's but real basketball shoes.

Personally I don't really think any of those tires are great choices, but understand you are somewhat limited by 17". The really good sticky street tires don't come in anything over 255 in 17". If you moved to 18's there is a lot more to choose from. I wouldn't give you crap for a Falken RT615k, they suck in comparison to most, well, everything.

Given your need to run 17", I think I'd do R888's over the others by a mile.

FASTFATBOY

Depends on the track, how well you "hit" the alignment to get the wear right and air pressures.

Define "last"....treadwear or grip?

The NT-05 will heat cycle out before you wear it out(but not by much). The key to the NT-05 life is session start pressures, the NT-05 likes low pressures, 26 ish PSI. Most people start them out to high because it's a "street tire" and they get greasy quick if you start pressures over 30psi.

If you are worried about wear I'd stick with the NT-05. The stickier the tire the shorter the life. I'd guess and say if you were getting 4 weekends out of the NT-05 you'd get 2.5 to 3 out of the NT-01 or R888.

emptnest

Good info to know, on all points.
I will be sure to check the HP hubs.

emptnest

Touche - I didn't ask the question clearly. I was referring to tread wear.

I got 12 track days out of my NT05's. But their grip was greatly reduced in the last 6 days. Even then though, they gave me a decent 10 minutes per session before getting greasy.

Will the tread wear of the NT01 last similarly (once the optimal grip is gone)?

strano@stranoparts.com

http://www.stranoparts.com/partdetai...D=0&ModelID=23