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Wondering what people think would be fastest on my NC.
My current track set is 17x9 235x40 NT01’s but I’ve spotted a set of 16x8 215x45 Khumo V710 twin groove semi slicks.

The V710's should still be faster.

In my experience compound is worth far more than tyre width on these cars.

Dan wrote:The V710's should still be faster.

In my experience compound is worth far more than tyre width on these cars.

With the low power I was thinking the wider rubber probably creates a fair bit of unwanted drag too?

Custardtart wrote:With the low power I was thinking the wider rubber probably creates a fair bit of unwanted drag too?

It does but 235 I think is a sweet spot.

On my previous NC which was setup exclusively for the track I ran through a few sets of Hankook Z221's and the 235 sets were consistantly faster than the 215 sets throughout their life but only by a couple of tenths. A bunch of the fast NC's moved up to 235 as well and found success with that size as well.

If you want to go fast you'll find a ton of time moving to A050's or Z221's.

I am running 2 wheel sets for track both on 16x8 FD wheels.

1) A050 225/45/16 - these have been my go to tire so far and have recorded good times.
2) Khumo V710 215/55/16 - I have done one session on Easter Creek south circuit but only their bed in run. They recommend with these tires to do the first session at less than full pace and then set aside for a minimum of 24 hours.
So I aim to do one of the sessions on Sunday at Eastern Creek on this tire so I will have a direct comparison to the A050.

At the price I paid for them, if they are with in a few tenths I will be pretty happy.

Dan wrote:

Custardtart wrote:With the low power I was thinking the wider rubber probably creates a fair bit of unwanted drag too?

It does but 235 I think is a sweet spot.

On my previous NC which was setup exclusively for the track I ran through a few sets of Hankook Z221's and the 235 sets were consistantly faster than the 215 sets throughout their life but only by a couple of tenths. A bunch of the fast NC's moved up to 235 as well and found success with that size as well.

If you want to go fast you'll find a ton of time moving to A050's or Z221's.

Thanks dan, great feedback

Snowmotion wrote:I am running 2 wheel sets for track both on 16x8 FD wheels.

1) A050 225/45/16 - these have been my go to tire so far and have recorded good times.
2) Khumo V710 215/55/16 - I have done one session on Easter Creek south circuit but only their bed in run. They recommend with these tires to do the first session at less than full pace and then set aside for a minimum of 24 hours.
So I aim to do one of the sessions on Sunday at Eastern Creek on this tire so I will have a direct comparison to the A050.

At the price I paid for them, if they are with in a few tenths I will be pretty happy.

Keen to hear how you go on the Khumo’s?

The lightest weight possible for your given wheel size. Also try and increase track width by changing offset.

For me 200/580R15 on 15x8 +20 are faster than 225/45/15 on 15x8 +25. BUT.... what are the rim/tyre weights...

Carcass weights - kg
200/580R15 - 6.46 (used)
205/50/15 AD08R - 8.44 (used)
205/50/15 AR-1 - 9.07 (used)
225/45/15 AR-1 - 10.79 (new) & 9.77 (used)

Wheel weights


So the 15x8 +20 combo = 15.21kg and 14kg for the 15x8 +25.

Interestingly I used a durometer on 2 sets of tyres. I need some more experience using this tool, but confident on the following readings.
200/580R15 - 65, 64, 60, 67
205/50/15 (AR-1) - 62, 68, 68, 65

Interesting the durometer readings aren't that different between the slick and the AR1s. Are they a hard compound slick?

I'm currently tossing up between going with another set of 205/50/15 AD08Rs (9.1kgs) va 225/45/15 RS4s (9.5kgs), on my 15x8 Advanti Storm S1 rims. Even being a slightly heavier tyre, I think the compound of the RS4 and the slight increase in width will make is slightly quicker.

SKYHI wrote:Interesting the durometer readings aren't that different between the slick and the AR1s. Are they a hard compound slick?

This made me think, as when I was taking the reading in the slicks it the value would very quickly decrease, a lot faster than in the AR-1's.

Looking at how to use the durometer....

Hold the durometer in a near-vertical position and press the foot of the gauge firmly against the specimen, (but not so firmly as to imbed the foot into the surface of the material). The dial hand gives the reading in durometer points. Creep or cold-flow of the specimen, if present, will be evident by receding action of the dial hand. Note initial reading, and again, the reading after a given time delay while maintaining firm contact of the foot
against the specimen. An example of a properly noted durometer reading: “Durometer A 61, Creep 7 at 15 seconds

Durometer readings can either be taken instantaneously or after a specified delay – typically on the order of 5 to 10 sec. Instantaneous readings typically give higher (or harder) results than delayed readings. But delayed readings are more representative of hardness and resiliency. Weak, less-elastomeric materials creep more than higher strength, more resilient materials.

Seems like I will need to record the creep value as well. I guess the question is now when people give durometer readings are they instant or after a certain duration?

Magpie wrote:For me 200/580R15 on 15x8 +20 are faster than 225/45/15 on 15x8 +25.

I'm guessing the 200/580's are slicks whereas the 225/45 are AR1s. You cant use different construction & compounds and then deduce an answer of lighter/skinnier is faster.
You'd need to have same tyres to remove that factor to make any valid assumptions.

I think 949 proved that so long as you weren't over-tyred, that width was more important than weight to laptimes. ie wider even if heavier was quicker than narrower but lighter.

rascal wrote:I'm guessing the 200/580's are slicks whereas the 225/45 are AR1s. You cant use different construction & compounds and then deduce an answer of lighter/skinnier is faster.

That was not my intention, I would expect slicks to be faster even if they are skinnier due to the slicks construction. Not to mention lighter!

I have new AD08R's on +20 15x8 rims and a slightly used set of AD08R's on +36 15x6.5 rims so can do a test with these.

SKYHI wrote:Interesting the durometer readings aren't that different between the slick and the AR1s. Are they a hard compound slick?

I'm currently tossing up between going with another set of 205/50/15 AD08Rs (9.1kgs) va 225/45/15 RS4s (9.5kgs), on my 15x8 Advanti Storm S1 rims. Even being a slightly heavier tyre, I think the compound of the RS4 and the slight increase in width will make is slightly quicker.

I’m sure one of the guys on here had some times showing the RS4 was quicker than the A008? What other choices can you run?

Custardtart wrote:What other choices can you run?

I generally have 3 tyres AD08R's in 205/50/15, AR-1 in 225/45/15 and Dunlop slicks in 200/580R15. Too much money to have any more tyres.

Sorry, no data on the V710 today.

Eastern Creek was not the gippiest today with Power Cruise on last night so a combination of rubber and oil laid down over the whole track. Then topped off today with lots of rain. Even the Medium A050's struggled fro grip.