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questions re slicks fitment, and swap for yoko a048's
daniel mason - 5/4/13 at 06:52 PM

hi all,currently have 205/60/13 rears 185/60/13 fronts on 6j rims on the fury but as im going to be running modified specialist prod class i need to run on slicks really (and they are cheap) so have a couple of questions!
1; what width can i get on the rear of a 6j rim? i want somewhere near the 185 width on the front,but would a 220 go on the rear? or would it be to big?
2;if anyone has some decent slicks with around 185 width for the front and slightly wider for the rear i would swap for my 2x 205/60/13 yoko a0488 reasrs which have not done much at all. (aprox 60 mins race use)

phelpsa - 5/4/13 at 07:09 PM

If you're planning hillclimbs, you won't go any faster on circuit slicks than on A048Rs, and you'll also need to buy a set of wets.

Try and get hold of 7.0/21-13 front and 8.0/22-13 rear crossply A15 compound avon slicks. They are extremely common sizes and even when a few seasons old and past their best they will be 100 times better than circuit slicks. Put a wanted post on Uphillracers.

Honestly, it's not worth moving from a set of good A048Rs to old circuit slicks.

daniel mason - 5/4/13 at 07:12 PM

im after a soft compound hillclimb/sprint slick adam,thanks.but was un sure of sizes on a 6j rim
also,thanks to danny keenan for the u2u help. much appreciated mate,and thanks for your time

phelpsa - 5/4/13 at 07:19 PM

quote:
Originally posted by daniel mason
im after a soft compound hillclimb/sprint slick adam,thanks.but was un sure of sizes on a 6j rim
also,thanks to danny keenan for the u2u help. much appreciated mate,and thanks for your time


I run a 7.2/20-13 on a 6 inch rim on the front

I'd be interested to hear Danny's advice, I'm debating changing tyre size for the next set at the moment.

[Edited on 5-4-13 by phelpsa]

daniel mason - 5/4/13 at 07:31 PM

what do you run on the rear mate?

phelpsa - 5/4/13 at 07:43 PM

quote:
Originally posted by daniel mason
what do you run on the rear mate?


8.2/20-13

General rules of thumb for hillclimb kit cars seem to be: for bike engined and light car engines 7" front is fine, 8" front if heavier. Same front and rear for upto 140ish bhp, +1" rear for upto 200bhp, +2" rear for more than that.

Obviously this depends on your driving style and where the majority of your events are, but that's what I've learned from observing the fast cars.

I'm considering dropping down to a 6.2/20-13 on the front as I never really get any heat into the fronts!

daniel mason - 5/4/13 at 07:53 PM

are you running 6" rear rim?

phelpsa - 5/4/13 at 08:00 PM

quote:
Originally posted by daniel mason
are you running 6" rear rim?


I'm currently running 6" front and 8" rear.

Dopdog - 5/4/13 at 08:40 PM

you could also go for a A92 compound

[Edited on 5/4/13 by Dopdog]

CNHSS1 - 5/4/13 at 08:59 PM

quote:
Originally posted by phelpsa
If you're planning hillclimbs, you won't go any faster on circuit slicks than on A048Rs, and you'll also need to buy a set of wets.

Try and get hold of 7.0/21-13 front and 8.0/22-13 rear crossply A15 compound avon slicks. They are extremely common sizes and even when a few seasons old and past their best they will be 100 times better than circuit slicks. Put a wanted post on Uphillracers.

Honestly, it's not worth moving from a set of good A048Rs to old circuit slicks.



abov is great advice

as for as hillclimbing concerned, A048Rs arent even great as List 1B tyres and circuit slicks, even a soft circuit slick will be poor at best.
hillclimb compounds such as A15, A92 etc are a semi cured rubber product, the usage (heat cycles) actually hardens them, hence why hillclimbers often move them on after a seaosn or half a season if really keen, as they will be 1 or 2 10ths slower than fresh.

at say Loton Park hillclimb, fresh A15s are worth .7-1s on my car, and the bestList 1Bs (ultra soft Kumho V 70s 2.5-3s slower. A048s probably 1.5s slower again

as for rim widths on Avon hill slicks, its a bit misleading as the designation isnt always the same as youd think.

you need their tech sheet (downloadable).

from memory so may not be 100, around 8" tyres you have 8, 8.2, 8.7.
if you check the tread width they arent .2, and .5 differing in widths and also have a slightly differing rolling radius, usually quoted in mm/rev or revs per mile.

by careful choice of tyre, for a given width you can alter the gearing or the shape of the carcass. this is useful if you have a controlled width wheel (control class or nowt else will fit), so you can have a rounded shoulder tyre on front and. a squarer profile in rear with a tad more rubber to the track, but both on same rim width.

personally for hills i would always go for a rim nominally 1" wider than the tyre ie 7" tyre = 8" rim. i run 10" tyres on 11" rim.

the reason is that a slight stretch to yhe tyre carcass gives more mechanical grip. You tend to run the tyres a tad underinflated cold, and the stretch stops the tyre going. parallogram

CNHSS1 - 5/4/13 at 09:02 PM

this puts all the load energy into the tyre surface creating heat where you want it, not the sidewall. This gives a nicer feel to the steering, the car feels sharper on turn in, bearing in mind, on a hillclimb the first couple of corners will be on cold tyres and relying on the compound only.

its different on a circuit car where you weave to flex the sidewalls to geberate heat to bring the tyres upto temp and more importantly pressure.

CNHSS1 - 5/4/13 at 09:06 PM

id go to your local hillclimb and tap up the 1100 class single seater boys for their cast offs. whilst too hard for a sub 300kg car, they will be spot on for. 7 type. Most run nominally 7" f and 8" r or 8.2 & 10 rear.

also worth looking at sidewall height, some run 20" diameter, others 21 or 22. using inch bigger rear gives a tad of chassis rake which can be helfpul with weight transfer and front tyre heating

HTH
craig

ps posting from not-so-smart phone hence poor spellings and punctuation, big thumbs-small screen!

[Edited on 5/4/13 by CNHSS1]

daniel mason - 5/4/13 at 09:34 PM

im wanting to keep the 6" wheels as they are compomotive cxrs. so need soft slicks to suit. running a freelander diff with quaife atb!

CNHSS1 - 5/4/13 at 10:19 PM

if you have to retain 6" rims then id go 6" fronts and 7" rears. You may have to speak nicley to some of the Jedi and other 600cc drivers for cast off front.

even at those widths they will give significantly more grip than the a048rs

TimC - 6/4/13 at 06:43 AM

I've got four Avon CR500s that I've just removed from 6" wheels. Would they be any help?