Question for Kumho Ecsta 712 owners

[Blackdimonds]

I have been using the same BFG TA ZRs for 2 years now and been fairly happy with the grip they offer. I did have to change over the rears this spring because of a flat in one of my BFGs. I bought a set of Kumho Ecsta 712 255-45-17s for the rear, and had them mounted last week. I put only a few miles (less than 10) on the car before last weekends Autocross. I found myself sliding the back end of the car quite a bit more during this event than in previous years. I had great times (down about 10 sec per run over last year) due to the major suspension upgrades I did this winter. My question is, if you have used the Kumho Ecsta 712s in the past, do they get better with a few miles on them, or will I find the same level of grip from here on out? I know that the suspension changes have a bit to do with the oversteer that I am getting this year (thats what I want), but I feel like the rear tires are just not gripping quite as well as the BFGs.

Thanks,

[APKhaos]

Paul,
The first couple of track sessions [20 minute runs] with new AVS Intermediates were exciting for me - new rubber can be extremely greasy. Once they had been heat cycled and scrubbed they were like different tires - plenty of grip and plenty of warning approaching the breakaway.

Kumos may be the same?

[jay castriotta]

The tires should grip better after they have a more mile on them although I'm not sure they'll be as grippy as the other tires even so. Usually you really want a few miles (1000) on most tires- other than the DOT approved race tires- to prevent the tread from chunking off. Keep in mind that different tires need different tire pressures due to different side wall stiffness- radials are very effective springs and changing the tire pressure can affect this greatly. The NASCAR guys are experts at this since they now use radials and they can't vary stagger like they used to with the old bias plys

[zuffenhausen]

I have Kumho 712s on my Focus ZX3 and they are not real sticky. I am happy with them as they were cheap and they do very well in the rain, but I wish the dry performance was a little better. In fact, I had more overall dry grip with the stock Goodyears after the tread wore down. I've got over 10K miles on the Kumhos so far and the performance hasn't changed much. Neither has the tread depth, so they're also good wearing tires. If you're looking for a street tire to compete on, you really should be running Yokohama's AVS Sport or a similar Ultra High Performance tire. The Kumho isn't it.

-zuff

[cmsteed]

Interesting that you chose 255/45/17's. My S/C came with 255/40/17's which on paper are the same outside diameter as the original tires, therefore I have recently replaced them with the same in Kumho 712's. 45 series tires should be about 1 inch bigger diameter than stock or the 40 series tire. Have you noticed that your back end sits higher than usual? Could this be the difference to your handling?


Chuck

[jay castriotta]

Good point. a one inch increase in diameter is a half inch increase in the radius so the ride height goes up 0.5 inches.

[adamnitti]

just got a set, myself. i've only put 1 autocross and about 200 miles on them, though... maybe i'm crazy, but it almost seemed as if my dunlop sp sports felt a little stickier...

regardless, i love my kumhos. i can't believe i outfitted my car for $326 bucks, shipping included. for that price, they are plenty sticky!!!

[Blackdimonds]

One correction I need to make, the tires are 255-40-17s not 45s. I know that the suspension changes I made are partly responsable for the change in feel (I had the flat tire before I could really get an idea of what the suspension changes had done to the cars handling), but I will try to play with air pressures next weekend at the autocross, I think I may try a little bit of drag racing style burnouts in a parking lot to see if I can scrub them in a bit as well (I will have to be very carefull with the tranny ect.. to do this).

[LeeH]

I agree with Adam. They're not as sticky as some tires, but for half the price they're OK with me.

I don't think I would have picked the 712s if I was going to do a lot of autocrossing, but keep us updated as you put more miles on.

The roads here in Phoenix are so rediculously straight that I don't get much chance to push my car's handling. I did have some 4 door Dodge product crawling up my tail pipe as I entered hard right hander yesterday. My car felt about the same as it did in that curve with its six year old dry rotted SO2s. The Dodge was .5 car lengths behind me going in and 5 car lengths (and understeering toward the curb) behind me coming out. My 2 year old daughter never looked up from her book.

[Blackdimonds]

If I had the money, I would have just ordered Kumho Victoracers 700s for both the front and rears. I mainly do autocross and DE with the car, and it is pretty interesting tring to keep up with the other M class racers on there R rated tires. I do take some pride in the fact that I am only 1 or 2 sec. out of first on these hard tires. You may ask why I compete in M class with others that have race tires. Well, I may go to R compound tires at some point this year, and if you move classes during a season, you will only get to transfer 1 partisipation point per event (not your points for finishing 1st - 5th). Thanks for all the replies, and I will post further info on what I find during the next event.

[Reg]

From experience I'd say to all of you out there on street tires is to buy a second set of wheels for DE and autocross and keep your street tires for their intended use.

You will get the beneifit of the extra grip of the R compound tires, and you will not punish your street tires on the lot or track.

This way you could get get two seasons from your street 712's, and buy one set of Victoracers to have fun with.

The only downside is the feel when the 712's go back on!

I have never driven the 911 at autocross yet. There just happens to be one at a 1/2 mile oval this sunday , but with the concrete walls there I am a little hesitant of sudden oversteer into a hard substance, and I do not have the R tires mounted yet.

[gr8fl4porsche]

What would you put on an 87 Targa that is used on the street for spirited sunday drives and possibly a DE event this summer?

I am looking for a sticky street tire - I do not drive in the rain if I can help it and wearability is not a big deal as the car rarely goes over 2000 miles a year.

[Reg]

If I were you , Id but the yoko ao32R's, or the kumho ecsta 700s. You can see both at tire rack. You will get more of a blast from your car with the extra grip you will have, plus your brakes will last longer as you will not be slowing as much for the corners!

I think tires are almost as important as the driver in an autocross. Nothing else can make such a prolific difference in a car. Not 300 HP , and not fancy coil over suspension components.