Tyres for hill climbing
Discussion
Avon Radials.
F - 195/530 R13
R - 250/570 R13
Use A15 compound on the rears.
The compound for the front depends on the sorts of hill you're doing, the depth of your pockets and how committed you are.
A15 is reasonably durable and gives good grip while A91 gives a bit more ultimate grip but is less durable and more sensitive to heat build up. At Shelsley, A91 works well (but you will probably need 1 set for practice and 1 set for competition runs) whilst Harewood, for instance, eats A91 compound particularly on the FL. The choice is yours but the safe bet is A15 all round while you learn the game.
If in doubt, speak to BMTR they will keep you right - 0121 331 1122.
F - 195/530 R13
R - 250/570 R13
Use A15 compound on the rears.
The compound for the front depends on the sorts of hill you're doing, the depth of your pockets and how committed you are.
A15 is reasonably durable and gives good grip while A91 gives a bit more ultimate grip but is less durable and more sensitive to heat build up. At Shelsley, A91 works well (but you will probably need 1 set for practice and 1 set for competition runs) whilst Harewood, for instance, eats A91 compound particularly on the FL. The choice is yours but the safe bet is A15 all round while you learn the game.
If in doubt, speak to BMTR they will keep you right - 0121 331 1122.
Xply tyres work best on lighter cars, are able to sustain greater slip angles with greater consistency than radials but yield less ultimate grip.
I have never tried Xplies on my Prosport but BMTR and Avon's advice was that it was too heavy and powerful to get the best results from them.
What is significant is that a Prosport can and normally does generate significant downforce (to give you an idea, mine consistently generates 2.2g lateral acceleration and, if I've had double "brave pills" for lunch, has seen 2.8g). To do this it needs to be meeting the freestream air at 0deg. So, anything other than trivial yaw angles is anathema to good performance. At the extreme (ie speeds which are beyond a Prosport on the hills) it is now generally accepted that quite modest yaw and roll angles can together generate the loads that cause sports prototypes to blow over.
Darren's Caterham would not have generated downforce (indeed, if its aero characteristics were anything like mine, lift was the order of the day) and would have relied solely on mechanical/chemical grip, so yaw could actually be a positive attribute. But interestingly, IIRC Darren did run his Force single seater with radials on the front and Xplies on the rear for a time. Perhaps he'll come back and share his experiences. We need to remember that the Force was around 200kg lighter than a Prosport, had an 1100 engine and relied on its wings rather than ground effects for downforce.
And finally! Always save your best until last, my Father taught me. You will not be able to buy wishbones from Radical to enable you to run the correct suspension settings for Xplies!
X plies need to run around 0deg camber, Avon Radials need around -1.5 deg, compared with more like -4deg or more for circuit slicks. We are kind of fussy here and even with -1.5deg were not happy with the ratio of rod end shank inside and outside the wishbone so fabricated our own wishbones specifically to run Avon Radials.
Do not be misled by Radical's "low camber" wishbones. These seem to be the same as their old "hi camber" standard wihbones while their new standard sets are "even higher". Good for the circuit racers but no so good for us.
Doctordave has recently switched to Avon radials and may be able to shed some light on his approach to wishbones. Perhaps Angus will also stop by and tell us what he does.
I have never tried Xplies on my Prosport but BMTR and Avon's advice was that it was too heavy and powerful to get the best results from them.
What is significant is that a Prosport can and normally does generate significant downforce (to give you an idea, mine consistently generates 2.2g lateral acceleration and, if I've had double "brave pills" for lunch, has seen 2.8g). To do this it needs to be meeting the freestream air at 0deg. So, anything other than trivial yaw angles is anathema to good performance. At the extreme (ie speeds which are beyond a Prosport on the hills) it is now generally accepted that quite modest yaw and roll angles can together generate the loads that cause sports prototypes to blow over.
Darren's Caterham would not have generated downforce (indeed, if its aero characteristics were anything like mine, lift was the order of the day) and would have relied solely on mechanical/chemical grip, so yaw could actually be a positive attribute. But interestingly, IIRC Darren did run his Force single seater with radials on the front and Xplies on the rear for a time. Perhaps he'll come back and share his experiences. We need to remember that the Force was around 200kg lighter than a Prosport, had an 1100 engine and relied on its wings rather than ground effects for downforce.
And finally! Always save your best until last, my Father taught me. You will not be able to buy wishbones from Radical to enable you to run the correct suspension settings for Xplies!
X plies need to run around 0deg camber, Avon Radials need around -1.5 deg, compared with more like -4deg or more for circuit slicks. We are kind of fussy here and even with -1.5deg were not happy with the ratio of rod end shank inside and outside the wishbone so fabricated our own wishbones specifically to run Avon Radials.
Do not be misled by Radical's "low camber" wishbones. These seem to be the same as their old "hi camber" standard wihbones while their new standard sets are "even higher". Good for the circuit racers but no so good for us.
Doctordave has recently switched to Avon radials and may be able to shed some light on his approach to wishbones. Perhaps Angus will also stop by and tell us what he does.
Jackard said:
rustybin said:
I think the O/P is campaigning on the french hills so may need something a bit more durable than us n'est pas?
Yes i'm French...Why do you said I need "a bit more durable"?
Our hills are very short compared to yours. In a Prosport we climb them in only 30 - 60 seconds. Therefore we can use very very soft tyre compounds such as A91. But A91 is too soft for a long hill with a lot of corners. So for French hills you will need a harder (more durable) tyre compound. "Doctordave" has recently been to St Goueno and, I think, found Avon A15 worked well.
LCM said:
Jackard said:
rustybin said:
I think the O/P is campaigning on the french hills so may need something a bit more durable than us n'est pas?
Yes i'm French...Why do you said I need "a bit more durable"?
Our hills are very short compared to yours. In a Prosport we climb them in only 30 - 60 seconds. Therefore we can use very very soft tyre compounds such as A91. But A91 is too soft for a long hill with a lot of corners. So for French hills you will need a harder (more durable) tyre compound. "Doctordave" has recently been to St Goueno and, I think, found Avon A15 worked well.
"Doctordave" have a the turbo SR4 or a clubsport?
Jackard said:
LCM said:
Jackard said:
rustybin said:
I think the O/P is campaigning on the french hills so may need something a bit more durable than us n'est pas?
Yes i'm French...Why do you said I need "a bit more durable"?
Our hills are very short compared to yours. In a Prosport we climb them in only 30 - 60 seconds. Therefore we can use very very soft tyre compounds such as A91. But A91 is too soft for a long hill with a lot of corners. So for French hills you will need a harder (more durable) tyre compound. "Doctordave" has recently been to St Goueno and, I think, found Avon A15 worked well.
"Doctordave" have a the turbo SR4 or a clubsport?
Voila!
I have a Prosport:
bonjour jean christophe,yes LCM is right i was at st goueno and mine was the white clubsport,the turbo one belonged to a irishman called rory stevens 450hp on full boost i think,well after taking LMC advice and fitting A15s all round and my first go at st goueno did it in one minute thirty nine seconds not to bad for 135hp engine and a novice so i am told by much faster drivers.yours dave.ps see you next year.
LCM said:
X plies need to run around 0deg camber, Avon Radials need around -1.5 deg, compared with more like -4deg or more for circuit slicks. We are kind of fussy here and even with -1.5deg were not happy with the ratio of rod end shank inside and outside the wishbone so fabricated our own wishbones specifically to run Avon Radials.
Perhaps Angus will also stop by and tell us what he does.
Which is why I run Xplies on the Clubsport. Can't generate enough -ve, with the ends fully screwed in can barely go -ve. Mine is a very early one so would have been designed for Xplies anyway?Perhaps Angus will also stop by and tell us what he does.
I started using A40 (A91) on the front but the radical destroyed these after a couple of events.
I now use A15 front and rear these work well on hills and are durable to last on the sprints.
7.2x20 front
9.0x21 rear (most would go for 22 on the rear but mine goes well on the 21s and are a bit cheaper)
Angus
Edited by SportsLibre on Tuesday 29th June 23:06
Edited by SportsLibre on Tuesday 29th June 23:09
doctordave said:
bonjour jean christophe,yes LCM is right i was at st goueno and mine was the white clubsport,the turbo one belonged to a irishman called rory stevens 450hp on full boost i think,well after taking LMC advice and fitting A15s all round and my first go at st goueno did it in one minute thirty nine seconds not to bad for 135hp engine and a novice so i am told by much faster drivers.yours dave.ps see you next year.
Ok i see, nice to meet you 
...I'm a novice too, at St Gouëno it was my second race.
This year my time was 1'37"803, i'expect to do better with some better tyres (i've old and hard for the moment) and much experience...
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