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I began to draft a hillclimber based on 10 inch slicks based on FSAE tyre data, turns out 10 inch is now cancelled by most manufacturers.
13 has taken its place, but seems to be getting edged out also.
Which leaves us at 15 inch, lots of choices, but a colosal rim around the 10 kilo weight which sucks for a grassroots car.
What is your take on a 'grassroots' tire size?
Will 13 inch still be around in 5 years?

coaster wrote: ↑

24 Aug 2022, 22:02

I began to draft a hillclimber based on 10 inch slicks based on FSAE tyre data, turns out 10 inch is now cancelled by most manufacturers.
13 has taken its place, but seems to be getting edged out also.
Which leaves us at 15 inch, lots of choices, but a colosal rim around the 10 kilo weight which sucks for a grassroots car.
What is your take on a 'grassroots' tire size?
Will 13 inch still be around in 5 years?

CF wheel might mitigate that, is that allowed?

Carbon rims would help, but would be purely for the realm of elite level racing.

Who is making the 10” slicks for the FSAE teams?

Hoosier were, only Avon make 10 inch wets now, no more Avon drys.

Have you thought of looking at Dunlop tyres? They make the tyres for the Mini Miglia series. Search HP tyres in the UK. Size is 160/490-10; available in hard and medium compounds. Ideal rim width of 6”, but will fit 5-7” wide rims. You can get some super-lightweight wheels for these and they fit ‘big’ brakes. The better quality wheels are multi-piece so you can play with offsets.
Not sure how much power you are planning to put through them, but the Minis are running with around 140-150bhp; the cars in the Libre class are up to 160-170. Worth a look, they should last and are not a huge price for racing slicks. They also do a wet version.

Awesome tip Stu, it will take some research with the new brexit laws, it tried to export some bmw m5 throttle bodies for 4 cylinder project but Uk border would not allow export.

coaster wrote: ↑

25 Aug 2022, 20:26

Awesome tip Stu, it will take some research with the new brexit laws, it tried to export some bmw m5 throttle bodies for 4 cylinder project but Uk border would not allow export.

Good luck!
Where will you be exporting them to?

Queensland, im hoping to get a bit of Mt Cotton hillclimb action and Willowbank motorkhana (autotest) in a special, i got a deal on cbr600 engine and the idea of scaled up shifter kart got me going.
Lightness is key.

That sounds awesome, something around the size of a FSAE car?
Are you going for a tube-frame or monocoque?
10” wheels are definitely the way to go!!

The rules for 4H khana state a minimum wheelbase of 1800mm, to upgrade to hillclimb events the roll over bar is upped from 32mm to 45mm which runs the car as a libre class in speed events.
Libre normally cannot run in multi vehicle track event because of the relaxed safety standards, so track time to tune the car in another type of event is important.

That sounds really interesting, there is an oval series in the UK called GP Midgets, not sure whether the rules are still the same, but they had a minimum wheelbase of 82” (2.082m), the class used to be real mix, some front engine, some mid engine, a-series, Ford & VW power units.
Using a motorbike engine was not allowed. I think that given the even shorter wheelbase of your intended class, I would be inclined to offset the driver and mount the engine longitudinally next to the driver (a bit like an old Mallock-style ‘clubman’s’ race-car); this would let you fit either a reverse gear or fit an electric motor & battery for reverse, you would also be able to sit fairly well back.
Does the 45mm roll-hoop allow you into track-days for testing?

I’d be really interested to see the full construction rules for the series and see what I could come up with!!

https://www.google.com/url?sa=t&source= ... LcXUUw8Mar

https://www.google.com/url?sa=t&source= ... 0ImMhuhEFH

Formula libre is a blank slate, one sentence regulation.
The regs for the car design come for the alternate track event class you seek to employ, there are single seaters but the scope of such a build goes into 100,000 plus, i'd like to keep my budget below 10,000 or my wife will kill me.

Edit; the 2082 wheelbase would be a relic regulation from the Austin 7 i bet.