sprocket3

Hello,

Car: 1978 911 SC Rolled Fenders up front.


I'm trying to purchase a set of Kumho tires for Autocross events and can't decide which tire size to go with. The new V710 look like the best bet in the Kumho line.

I run 205/55/16 front and 245/45/16 rear on Fuch 7/8 inch wide rims for street tires. Kumho doesn't make either of these size tires in the 710.

Can anyone tell me what whould be a good alternative?

Also I have read a lot about people using 15" rims for autocross. Is this a better idea than the 16" rims?

Thanks

earlyapex

I also have a 78SC and I am planning on going to a 15 inch wheel with 225/50 sized tires all around. This gives you lower overall gearing. Kumho makes the Victoracer and V-710 in this size. You can also go with the Hoosier A3SO4 if your budget allows for it.

Rod.

I just bought a '77 911 set up for autocrossing that came with a set of Yokohama Advan 032R in the backseat. I haven't tried them yet so can't comment on how they are. I think they're 225/50/15 so maybe something to also consider.

sprocket3

That seems to be the popular size. I would think that it would change the balance of the car to have the same size tire on all four wheels though. This may be the point of doing it!

2002M3Drew

Kumho has kinda screwed us over by not offering a 245 size. Surprisingly, this is also the size that original S2000 Hondas need...they have to be coming eventually. Until then, the 265 rear is too large IMHO, and throws gearing off. V700s are in our sizes, as are the new Hoosier A3S05 (which is also supposed to be stickier than the V710). For a good all-around R Comp, hard to beat the RA-1 Toyo.

redidrum

I have 17" Kumho 712 --- 205/50/17 and 245/45/17 on my 82' Targa. They barely fit and I like the price of Kumho's vs. the Yokohamas I had. I eat up tires quickly these days since getting extra horsepower. Bought them at Discount Tire.

earlyapex

sprocket3,

Yes, I do wish we could get a wider rear tire for 15 inch wheels, cut manufacturers are focussing on the larger more popular wheel sizes. You can adjust your sway bars to compensate for less rear tire. The real benefit of the smaller tire/wheel combination is lower effective gearing. This is very important getting out of the tight turns that all autocrosses have. What's the trade off? This may not be the optimum tire/wheel combination for open track use/competition where most SC/Carrera's are running 16x7,8, or 9's or 17's. I guess I'll need more garage space.

fixnprsh

Kumho, spend money on better tires

sprocket3

Clockwork,

Which tires would you have me spend my money on?

The Hoosier A3S04 seems to wear out real quick. I have read that some people have only had them last 5-6 events!

fixnprsh

I'm not exactly sure of what you're needs are, tires are important, but if you need to run a DOT legal tire I would recomend Michelen Pilot sport cups, the aren't the stickiest, but wear extremely well. But victor racers are good too, Im not a fan of Kumho street tires though, toyo RA1's we use on the spec cars with good results

sprocket3

What about the Avon Tec-R tires?

I want something that is a little easier to deal with than the Hoosier A3SO4 tires and last longer. I’m not trying to win nationals or anything. I’ve been running on street tires (Dunlop SP9000), and would like more stick on dry pavement.

I would also give up a little time on the autocross for the ability to drive 2-4 miles on the street to our local events.

My car is setup real well with stiffer t-bars, lowered, and corner balanced. I also have adjustable Smart Racing bars so I think I can tweak the cornering a little if it will not do what it needs to.

What about this combo so I can keep the balance similar to my street tires and still be able to use them for DE days:

Tec-R 205/50/15 Front and 225/45/15 Rear.

fixnprsh

Personaly we havent run Avon's yet, but the buzz is they are a good tire. If you do auto X you will need a set that has a soft compound so they will heat up quicker, but if you are going to be doing DE and track events and are a fair shoe, you might need a harder compound depending on ambient temps and track conditions. you're in the Pacific NW so you can be hot or cold. but not too hard as you aren't trying to lug a #3400lb, 400hp mustang around willow springs in 100 degree heat. I wouldn't be apposed to driving on any such a tire for a few miles to the event (I know people that cruise Victor racers on the street daily and have made 200+ mile road trips on them) the best thing is to find out which one YOU like best, Kumhos are a good COMPETITION tire and they are cheap, you can buy them shaved and heat cycled from TireRack.

I'm going to try a set of Yoko A032R's for street tires, I live in SoCal and hate wheel swaping and I do a lot of canyon running (weekly) and they are cheap. I have currently AVS ES100's that have worn like iron and have excellent grip all the way up to the end, so I figure I'll push the envelope a little.

sprocket3

What do you think about these sizes:

205/50/15 Front and 225/45/15 Rear


They should be similar in width to my 205/55/16 front and 245/45/16 rears that I'm running on 16s now. But just a little smaller in diamater according to the charts that i've read.

fixnprsh

the front would seem ok, but the rear are narrower and will have a smaller sidewall which will help with side wall flex, but also since a smaller diamater, it will have an effect on acceleration, but will also have a tendency to give a harsher ride, and with a narrower width, will have a reduced contact patch. Its all about trial and error