fleming23

Need some advice on tires for my 71 that is beginning to see more track time.

Quick run down on the car.

GMPP 525hp LS3
TKO600
VB&P Performance Plus full suspension
Don't know the actual weight, but should be low 3k.
Will always be a street car first, and a track "toy" second.

I had 17x8" Vintage Wheel Works V40s with 255/40-17 Dunlop Direzza ZII Star Specs and felt the traction was lacking at a track day a few months ago. I upgraded, in a sense, to 18x10 American Racing Torq Thrust IIs with 295/35-18 Nitto NT05s on all 4 corners. I know the NT-05 is not the best track tire by any stretch, but it is inexpensive and I wanted to give them a try as I am not competitively driving or trying to squeeze every tenth of a second out of a lap. Well, traction was MUCH improved at Road Atlanta yesterday BUT I have a major rub in the rear suspension when the car settles into turn 1, smoking rubbing melting, etc. I already put a 1/8" wheel spacer on as it rubbed on the street when I got the wheels which seemed to cure my problem temporarily. However, on the track the rub was pretty significant, to the point where I could not get a sign off to move up to the next run group (even though I had been running it and monitoring the rub all weekend). I plan to stiffen the rear suspension by adjusting the monoleaf and already ordered a 1/4" spacer to see if that helps. I don't want to push the wheels outside the wheel-well or start rubbing too much on the fiberglass.

So, my question is, would a 255/40-17 R comp tire, or more specifically the Toyo RR (which I can get pretty cheap as take-offs) give me as much traction, or more, than the significantly wider 200 tread wear Nitto. I can fit the 17x8" wheel without spacers or modifications but I hate giving up so much bite from the added tire.

My current thought it to run the 17" wheels for track days only and keep the 18s for the street IF I can get as much traction out of the 17s. I was able to push the car harder than I would have thought possible on the Nittos. Even with the 295s, I found myself wishing for a bit more traction in turns 1 and 7 at Road Atlanta so I am hesitant to take 20mm of tire away, even if on a much sticker compound.

Thoughts, advice?

This is with the 295/35-18s

fleming23

I appreciate the comment but I am struggling to dissect what you said.

Where did a 275/35-19 come from??? I don't have 19" wheels.

I could put a 275/35-18 on the car to narrow the contact patch a bit and possibly cure some of the rubbing issues, RA1s come to mind. However, the 18" wheel is my every day, cruise around wheel and I don't want to over heat cycle RA1s on the street, not to mention picking up all the road crap. Remember my comment, "Will always be a street car first, and a track "toy" second." Your next point about offset and wheel flares. I have the wheels I have....they fit (mostly at least) and I don't intend to buy another set any time soon so I am stuck with trying to best work with what I have. Same goes for flares, not cutting up this car to put flares on it - back to street car first.

When I ran the ZIIs I was only using a single set of tires for street/track duty. I did not intend to have a dedicated track tire as this isn't that kind of car. However, now that I have the 17" wheels available and unused, I could have a dedicated track tire but am limited to a 255 width tread.

My question then goes back to, is a 255 r-comp tire on an 8" wheel (Toyo RA1, RR, Continental Challenge, Hoosier R6/7) going to be as grippy as a much wider 10" wheel and a 295 extreme street tire (NT-05, 888, etc.)?

Sure I could just try it and find out but that is one hell of an expensive test with not just tire cost but track day fees, etc. An event with Chin this last weekend was probably $1000 once I factor in the depreciated cost of tires, hotel, travel fuel, track fuel, and the various other consumables.

I appreciate the feedback, just trying to dig through the details.

fleming23

These are the 18" wheels on the car currently.

http://www.wheelsforless.com/VN8158161

These are the 17" wheels I am discussing putting a r-comp tire on.

I believe the 17s were ordered with a 4" backspace, IIRC.
http://www.vintagewheelworks.com/pro...heels/v40/17x8

That's it. Don't think I am putting 19s on a C3 corvette.... A C6, sure all day long, but not a C3.

B Stead

The 275/40-18 R888 will be okay at -12mm wheel offset. Not perfect but okay. The 295's would need fender flares.

So a 6mm spacer with the 0mm wheel offset will be -6mm offset and a 12mm spacer will be -12mm offset. Get the tires and two sets of spacers.

Oh, I hope we didn't forget about offset trailing arms for the rear

fleming23

Again, thank you but that really wasn't my initial question....I don't think.....

The question revolved around fitting 17" 255 width 40-100 UTQG tires, compared to 18" 295 200 UTQG and if the softer tire can more than make up the 20mm size difference for better clearance.
I like how the 295 felt on the track, and would like even more bite, but not sure if I can get the same from a 255 tire without killing it.

B Stead

The Star Spec has about the same traction as an R-comp. The tires have different handling characteristics but about the same traction. Star Specs with a traction problem are just burned-up
.

E-Emmons

For HPDE I personally like the width over the treadwear rating. An aggressive skinnier tire might be just as fast, but i found the feel of the wider tire gave more confidence and was overall more enjoyable to drive.

When running TT I used a Hoosier on the smaller tire ( smaller size was much cheaper ) and ran faster.

fleming23

Thank you, that is the sort of feedback I was looking for and unfortunately what I was afraid of hearing. I have a set of 255/40 Toyo RR take-offs that have 75% tread left so I might get them mounted on the 17x8s and carry them with me to the track next time. I certainly don't want to take my handling the other direction though, if anything I need to find more traction.

LateBreak

Personally I think that you could go just as fast on 255 Z2*'s as you did in the video on the bigger tire. I don't know for sure what your experience level is, but the narrower tire will teach you more about your car and how it handles at the limit, while saving you about $100 per tire vs a wider 18. HPDE's are about going fast, but for my dollar I prefer to see them as a place to learn and improve skills that can be used competitively in sanctioned events. So, since it's not a competition car, I'd default to the narrower tire and spend more time learning to go faster with a lower grip threshold. I assure you there are still seconds to be found.

fleming23

I have not tried Road Atlanta on the Z2* but did do Atlanta Motorsports Park. It had some pretty bad understeer through the carousel, and turn 6, to the point where I was loosing lots of time, as well as other places on track. This wasn't just dive bombing a corner and wondering why it wouldn't stick but a gradual easing onto the throttle trying to power out of the apex to track out.

I absolutely know what you are saying and agree, learning to drive within the confines of the car's abilities can certainly help improve overall driving ability. There is no doubt that I have much to learn behind the wheel. At the same time, I don't want to be out tooling around in a Miata either. At this point, I have no intention of doing any competitive racing or time trial events. I go to HPDE events to have a good time and push both my car and my own abilities. Each time I go, I feel myself get a bit better and a bit faster as I learn how to get the car around the track. There are many things I still need to work on such as threshold braking right to the point of turn-in, with a slight trail brake. Driving this 1971 around the track hard is such a different experience than hopping into a C6 and doing the same thing. The car vibrates and moves around so much more that it makes consistency that much more difficult to achieve. The video was shot from a RamMount suction cupped to the front window. If you look at the same style set up in a C5/C6, the video is smooth as glass. At the end of the day, I think this will make me a better driver. I am just trying to overcome some handling characteristics of this car, without doing extensive modifications, to bring it to a closer playing field with some of the modern vehicles on track with me. Not discounting your comments or opinions, just sharing where I am coming from in debating changes to the car to make it more capable.

0SpeedFreaksUSA

If you liked the grip levels and characteristics of the 295 nt05 but were having running issues you cold always try a slightly shorter, wide tire in the rear. But this would of course depend on where the tire was rubbing. We have a few remaining sets of the 285/35R18 Hankook R-S3 V2 left in stock that we have been selling at a great price- Hankook R-S3 V2 285/35R18 (Set of 4)

The toyo RR is a fast and sticky tire when new (significantly faster than an NT01/R888 but slower than a hoosier R6/7 or BFG R1) However be aware that competition tires are very sensitive to heat cycles, age and storage. Buying takeoffs is a bit like playing roulette unless you know all the info about them.

Almost more important than outright grip levels is the characteristics of the tire, especially for newer drivers. Some competition tires like the BFG R1 are very peaky, meaning when they start to slide the grip levels fall off a cliff and you have to be quick to catch it or you will spin. This trait is magnified as the tire ages and more heat cycles are put on it. I have no firsthand experience with the RR so I can't comment on how they are in those regards but its something I would consider. Conversely street tires tend to be more progressive and easier to drive. I have tested every EHP street tire available since 2009 on my S2000 (my class requires them) and so far the R-S3 and the AD08R are by far the most progressive and "easiest" tires to drive on since they tolerate large slip angles very well. This is on road courses not autocross, BTW.

-Matt M.

Bill Dearborn

I used to have a 71 many moons ago. Where are you getting the rear rub? I know when I upgraded my 71 from the OEM sized tires of the early 70s to the OEM sized tires of the early 80s (255/60/18s) I had a serious tire rub where the clip that held the P Brake line in place was making a groove in the rear tire sidewalls. The only solution was changing to GM's way of mounting the P Brake Cable in the early 80s which provided more room for the tire.

Bill