Racing Imps - upping tire temps?

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knutspeed
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Racing Imps - upping tire temps?

Post by knutspeed » Tue Aug 17, 2010 10:38 am

Anyone with tricks for getting wide boots up to temp? The Avons we are running now didn't get very hot, considering it was as hot a day as they come over here. After the cooling down lap, the fronts were only at 40deg C. We started with 24/27psi cold, and they didn't increase more than 4-5psi in the race.

Anyone with inside info from back in the days of slicks?
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
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benwick3
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Re: Racing Imps - upping tire temps?

Post by benwick3 » Tue Aug 17, 2010 12:20 pm

Although I'm using modern Michelin radial slicks an a lighter car I woul have thought your problems could be due to the high pressures you are using in the front. I'd try reducing to say 16-18 psi and see what happens.

Pete Richards
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colin rooney
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Re: Racing Imps - upping tire temps?

Post by colin rooney » Tue Aug 17, 2010 12:41 pm

I run avon slicks on my imp A11 compound and the optium preasure that avon say is 20psi when hot

col
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Re: Racing Imps - upping tire temps?

Post by ImpManiac » Tue Aug 17, 2010 12:51 pm

I wondered whether or not reducing the tyre pressures would help. Having no experience of setting up race cars, though, I thought it best to leave it to Pete and Colin above! :D

Good luck with it! What a fabulous little race car! And the engine sounds really great too. :wink:

IM 8)
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Re: Racing Imps - upping tire temps?

Post by knutspeed » Tue Aug 17, 2010 1:08 pm

Thanks all, we'll just have to see how low we need to go. These are Avon street-legal tires - not slicks.
Matthew Birger Patrick (Knutsen)
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benwick3
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Re: Racing Imps - upping tire temps?

Post by benwick3 » Tue Aug 17, 2010 1:20 pm

Even with street legal tyres I think your tyre pressure are too high. I also run Avon CR28 Sports and Yoko 048 and use the same tyre pressures as for the slicks with good results. I'll stick by my suggestion of 16-18 psi with 16 probably being favourable.

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Re: Racing Imps - upping tire temps?

Post by bks974c » Wed Aug 18, 2010 6:38 pm

Reading an interesting thread last night that maybe helpful. Challenges normal wisdom.

http://www.trackscotland.co.uk/forums/v ... php?t=2128

Scott
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knutspeed
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Re: Racing Imps - upping tire temps?

Post by knutspeed » Wed Aug 18, 2010 7:06 pm

I dunno - of course there is a limit to how wide one can go before it's pointless....and it's all about driveability.

I think we're pioneering the Avons on the Imp in "modern" racing - haven't seen anyone else do so yet - but my initial feeling was that there definitely was more grip under braking and cornering (we tried the conventiional 048rs in a session too).
But we've got tons of fun coming up; the wider tires require different suspension settings, pressures, ride height, rake, gear ratios etc etc. We'll do more testing underway. I can only compare to Doc's Imp I tested at the same circuit last year, and it's difficult because the circumstances (and gear ratios..!) were completely different. I'd say that the car was easier to toss about on the Yokos (with me coming from Minis and CR65 tyres), but the initial impression is that the car is faster on the Avons, and rewards smooth driving. I could not believe the stopping power I had, even on cold tires, and next to nil rear brakes (The fluid boiled after 4,5 laps). There are more options as well; we could run the same wheels at the rear as the fronts to change the final drive somewhat, and I think I'll stick to the yokos when wet (unless I get some wet back-to-back testing). The yokos are excellent in the wet imo.

We'll drop pressures as recommended here for the next session, along with softening the front ARB and stiffening the shocks all round even more. Possibly also lower the front of the car as far as allowed. It also needs front camber as it is lifting the inside wheel, classic Imp-style. I'm sure Doc has some tricks up his sleeve as well.

Can't wait to do it all again!
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
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Re: Racing Imps - upping tire temps?

Post by benwick3 » Thu Aug 19, 2010 9:43 am

If you think the Yoko's are great in the wet you should try and get hold of a set of Avon CR28 Sports. They are about 10 times better!

I toyed with the idea of ACB 10's on the Clan several years ago as a fellow competitor was using them on his Spitfire. In the end I didn't due to cost and the fact that Yokohama came out with the A048R which did not require the extensive changes to the suspension that the Avon required.

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Re: Racing Imps - upping tire temps?

Post by knutspeed » Thu Aug 19, 2010 10:18 am

Thanks for the tip, Pete. We'll definitely check out the CR28s!
Matthew Birger Patrick (Knutsen)
Sarpsborg, Norway
FIA App K Historic Racing Imp - Bevan Tribute - www.shag.no
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