Avon tyre sizes

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Dave Woodward
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Re: Avon tyre sizes

Post by Dave Woodward » Sat Mar 26, 2016 7:42 pm

If anybody has an old pair of 295's that are no good for the road any more let me know. Still trying to find something to stand the FIA rears on that fit. The ones that Peter kindly passed on are too narrow.
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clive
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Re: Avon tyre sizes

Post by clive » Sat Mar 26, 2016 8:39 pm

Dave/Peter. How do you manage to make your tyres last 14 years? What is your annual mileage? I average around 10k miles a year and need to replace my rears every other year and fronts probably every three years. Also Peter, how did your car handle with the rears softer than the fronts? Every rear wheel drive car I've ever owned had higher pressures to the rears.
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Re: Avon tyre sizes

Post by agnoraan » Sat Mar 26, 2016 8:40 pm

I've got Pauls old Goodyear rears you can borrow if you want? I won't need them until I get into the scratchbuild car and that's a while off yet.

Nige

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Re: Avon tyre sizes

Post by Dave Woodward » Sat Mar 26, 2016 8:49 pm

Clive,

If I said my car was registered in 2008 and it currently has 14,000 on the clock, that probably answers your question. Don't forget, the tyres were on the car during the build, which took 7 years in itself!
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Roger King
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Re: Avon tyre sizes

Post by Roger King » Sat Mar 26, 2016 11:57 pm

clive wrote:Dave/Peter. How do you manage to make your tyres last 14 years? What is your annual mileage? I average around 10k miles a year and need to replace my rears every other year and fronts probably every three years. Also Peter, how did your car handle with the rears softer than the fronts? Every rear wheel drive car I've ever owned had higher pressures to the rears.
Clive, I've always run either the same pressure all round, or slightly more air in the fronts on Healeys, TRs, Tiger, Jensen, Mustang etc. (on modern-ish radials). These cars are significantly heavier in the nose, and very light at the back. A bit less air helps with rear end grip.
Given the tyre history mentioned in this thread, it may be worth noting that there have been mutterings about introducing a maximum age for tyres to pass an MOT - I believe this was to be 7 years, but nothing's come of it as yet. Don't worry though, we won't get any say in the matter.

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Roger King
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Re: Avon tyre sizes

Post by Roger King » Sat Mar 26, 2016 11:58 pm

Dave Woodward wrote:Don't forget, the tyres were on the car during the build, which took 7 years in itself!
Huh, know the feeling. The SP Sports on my car are now four years old, and have done all of 60 miles...

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Re: Avon tyre sizes

Post by David Large » Sun Mar 27, 2016 7:21 am

I run my tyres at 25 psi all round. It seems fine to me.

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Paul Blore
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Re: Avon tyre sizes

Post by Paul Blore » Sun Mar 27, 2016 9:51 am

Roger,

Have you weighed your car? I can pretty much guarantee that it isn't nose heavy. In fact, it almost certainly has a rear weight bias.

Before I fitted the large fuel tank, mine had a 48/52 front/rear weight distribution and that's with an iron big block up front and we both have the same iron diff.

There is a wide held belief that Cobras and 427's especially, are nose heavy. They aren't. They have pretty much perfect weight distribution i.e. with a slight rearward bias.

Lesson over. :wink:

However, I agree regard tyre pressures. A slightly lower pressure on the back tyres will aid traction and the fronts can be adjusted to get the feel and turn-in response desired. I came to the figure of 28psi all round by measuring the temperature of each tyre with a laser thermometer at three points across the tread i.e. inside, centre and outside after driving on mixed roads. A constant temperature across the tyre is ideal, but the suspension setup may not allow that, so you want a straight line temperature "curve". If the pressure is too high, the tread centre will work harder and therefore heat up more and if too low, the shoulders will take the brunt of the work.

The Goodyears are cross-plys and the side walls are very flexible, whereas the Avons are radials and are much stiffer, which is why I've reduced the pressure very slightly.

Paul

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Re: Avon tyre sizes

Post by Roger King » Sun Mar 27, 2016 10:03 am

Paul Blore wrote:Roger,

Have you weighed your car? I can pretty much guarantee that it isn't nose heavy. In fact, it almost certainly has a rear weight bias.

I've always known my Cobra is around 50/50. That's why it's not on the list of cars I described as nose-heavy...

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Re: Avon tyre sizes

Post by Paul Blore » Sun Mar 27, 2016 10:12 am

Ahh, I see. I misunderstood the meaning of "these". I thought you meant Cobras, but I see now that you're referring to your list. :D
It would be interesting to see what your weight distribution actually is given that it should be identical to a new original 289. I'd hazard a guess at 47/53 with driver and half a tank of fuel.

Paul

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