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Well you say that !!!

I have just looked at the under video - yes it worked video to follow hopefully.

However, I made a rookie error and symptomatic of sprinters. 
I made changes after 1st practice. I had a slippy and tank slapping practice that I put down to tyre pressures too hard. ( rather than a fresh and slippy track) thus looked at tyre pressures - yup harder than my usual set up so lowered them to my usual settings- yup I know you can see what I didn’t at the time !!!

tyres are now warm - dropped to cold settings Doh!!

and I did the timed runs like this !

this is a screen shot of the video off my laptop as a teaser

will try and do an in screen pic or even side by side. 

thats a 55 profile stiff walled tarmac rally tyre !!!!


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Interesting that there is such a flex in 55 race tyre. What pressure was in the tyres? 

congratulations for such a result , all the work pays out.

Edited by Martin
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Cracking. Most excellent in all respects. That looks like a great fun track. The car is now noticeably faster and sounds great.  Like the extra camera position. 1st in class….. :goodjob:

You need to pump the tyres up….. but you know that. I wonder if you might also benefit from a little more negative camber - do you know what you have now?

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That was bloody brilliant Hamish.

Car sounds superb and going very well indeed. Bit of daylight under the tyre at times :biggrin:

It looks like a lot of deflection on that tyre but the there is a LOT of load on the outside front corner and you only have one data point to judge what sort of deflection you should expect. The bit that matters most (with qualifications) is keeping the tyre contact patch flat to the road which it seems to be doing pretty well

They do seem to be doing a good job at that so I suspect that you can't be that far off the right pressure for the conditions.

Best way of checking tyre pressures other than feel is to check the temperature across the width of the tyre immediately after a run. For a correctly inflated tyre the temp of the middle should be very roughly the same as the average of the outside and inside. A lot cooler and the the tyre is underinflated, a lot hotter overinflated.

For camber if the outside of the tyre is running a lot hotter that the inside then more camber is needed. With the caveat that this affects straight line stability. Excessive tyre defection will also affect the inside/outside balance too. Because nothing is simple.

The other thing that will be adding to the defection of the tyre is that it is not on the maximum size rim for the width. A wider rim will give a stiffer sidewall response, if a. the car will take a wider rim and b. if you want to spend the not inconsiderable dosh :blink:

The other thing to bear in mind is that some sidewall flex is also beneficial for 'our' old cars with their less sophisticated suspension geometry both for grip and handling feel where the surface is anything but perfect. Particularly on the road but also for handling track bumps.

And then there are heat effects on short hillclimb/sprint events vs longer ones. Sometimes you have to compromise with a slightly softer setup to compensate for starting from cold off the line even if when the tyre is hot towards the end of the run it's perhaps too low. That first 72 feet from the standing start is - all else being equal - where the race is won or lost in a sprint.

For comparison running 185/55 Avon ZZR super soft or 185/60 A48s softs on the Spitfire (admitedly quite a bit lighter than the TR and with the swing axle rear) of around 23 psi at the front and 19 psi at the back. So a lot lower than you would expect. Photos showed quite a bit of defection but actual grip was better and the standing 72 foot times were significantly better.




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Thanks for your kind words and support as well as the push to get tyre in action footage. 
I know that it was really to get tyre in air footage  

but the at least I now know that I need more air pressure and not to use cold pressures on warm tyres!!

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Bloody hell....!

Where do we start.

Just a year after the catastrophy at the pits

no seatbelt and that great big metal contraption strapped to your chest 6" from the steering wheel!

And all the traffic, on the one hand but also compared to a modern road how little traffic there is.

And it's really just a road with all the hazards if you come off (thinking IoM TT here)

But what a fantastic bit of film, with Hawthorn doing his own comentary.

Thanks Hamish

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