Kumho v70 soft compound on R500

[London GT3]

I have a K Series R500 and I am thinking of doing the Birkett relay race in October. Does anyone have experience of the soft compound Kumho V70 or should I stick with medium compound? I will have to run for 1 hour.

Thanks for any help.

[sam919]

Medium, might even be worth considering K90 if your pushing hard it for one hour.

[Aeroscreens]

Bear in mind that the Caterham sprint guys are using soft (and some super soft, I think) then I can't see them lasting for an hour. Just a thought.

[DaveK-S1]

Stick with the mediums , we use them in the CSCC mag 7 40 min races and they are fine, we tried softs but they they went off after about 30mins if it was too warm.

The mediums take a lap or too longer to get up to temp

[London GT3]

Thank you Dave K - just the kind of experience based advice I was looking for.

[sam919]

London GT3 said:

Thank you Dave K - just the kind of experience based advice I was looking for.

As apose to the other guff suggestions you were given?

[James.S]

Agreed,

We have to put V70's on the CSR in Mag7's due to sizing issues. The softs went of around 15 mins and at 30 mins they were hopeless.

The mediums are ok for 40 mins but i would suggest testing a set of hard compounds aswell.

All that said - your running an R500, so i would use Avon ZZR's, better all round than the V70's in any compound. They are also much lighter on the front end than the Kumhos.

J

[London GT3]

sam919 said:

London GT3 said:

Thank you Dave K - just the kind of experience based advice I was looking for.

As apose to the other guff suggestions you were given?

It wasn't supposed to read like that! Thanks to you too Sam.

By the way, I have ordered up the med compound V70's

[London GT3]

James.S said:

Agreed,

We have to put V70's on the CSR in Mag7's due to sizing issues. The softs went of around 15 mins and at 30 mins they were hopeless.

The mediums are ok for 40 mins but i would suggest testing a set of hard compounds aswell.

All that said - your running an R500, so i would use Avon ZZR's, better all round than the V70's in any compound. They are also much lighter on the front end than the Kumhos.

J

Thanks James, I looked at the Avon ZZR's but I have 8 inch rears and 6 inch fronts and the ZZR sizing didn't seem to work in the sizes available for the 13 inch rim.

[James.S]

You have standard R300/400/500 rears - you can get the 215 ZZR no problem for them.

The reason we are forced down the Kuhmo route on the CSR is beacuse the rears are 9". They destroy the feel of the car.

Only my 2p but if i could get your order swapped out i would.

J

[mickrick]

James, I know Avon don't recommend a 9" rim for the 215 ZZR's but I was told they work well on a 9" rim, and the 185's work on a 7 1/2" rim. That's only 1/2" on front and rear beyond what Avon recommend.
Have you tried themon a 9" rim? If so I'd be interested in your findings, and why you say it won't work.

Cheers,
Mick.

[James.S]

Avon not recommending them is enough for me really.

However, i have run the ZZR's on 8" rims on the CSR when it was around the 250hp mark, they where just ok, ultimately struggling with the power. I don't see the point in stretching them over 9" rims, you might aswell run 6" fronts and 8" rears.

[mickrick]

Hi James thanks for the reply.

When I had my rims made up, I had intended to fit the 245/50 13, so I had them made up as 9", then Avon brought out the ZZR's, and I read they are quite a bit better on grip.
So I was considering giving them a go.
That was why I asked your opinion. But then again my car is de-dion and not IRS, so on reflection I guess it's a whole different ball game.
I'm using JPE 2 degree ears by the way.
My car will be road use, so I think I'll stick with the CR500's, especially as it can get damp on the mountain roads here.

Cheers,
Mick.

[James.S]

For road use i doubt you would notice the difference between ZZR's and CR500's. The ZZR is hopeless in the wet so CR500's is the way to go.

Avon also make a massive 245/13 CR500 ISTR.

[mickrick]

Yes, it was the 245 CR500 I was refering to. I'll stick with that then, as I worked out all my gearing calcs on the CR500's.

[sam919]

James.S said:

You have standard R300/400/500 rears - you can get the 215 ZZR no problem for them.

The reason we are forced down the Kuhmo route on the CSR is beacuse the rears are 9". They destroy the feel of the car.

Only my 2p but if i could get your order swapped out i would.

J

I found the csr to have its feeling destroyed already with stiffness of the chassis.

[sam919]

London GT3 said:

It wasn't supposed to read like that! Thanks to you too Sam.

By the way, I have ordered up the med compound V70's

I dont think you'll be dissapointed, i just had a weekend on a new set and they are excellent, a little heavy...

The reason i had to get a new set was the last one 'i thought' had, had it.....they were 2.5 years old and had done around 10 hours track time. There wasnt any difference in time although the track was a little slower than usual with the front runners around 1 sec down on the usual times.