The Kumho tires are quiet but squirmy

[Dale_K]

Haven't done an alignment yet. I have some hope these tires might improve a little as they wear. Skinny tread blocks and full depth tread can create squirm. I think racers shave most of the tread off tires to improve handling.

Still looking for tire pressure advice to reduce understeer.

[Topless]

Ok Dale, we can probably help you sort this out. Start at the beginning. Are these the tires you just put on the front?
http://www.tirerack.com/tires/tires.jsp?tireMake=Kumho&tireModel=Ecsta+LX+Platinum&partnum=245WR7ELX&vehicleSearch=false&fromCompare1=yes

What tires are on the rear (exact make model and size)?

As long as the tires are very similar in type, temperature, traction, and wear ratings, even different brands, they should work together pretty well. If there is a big mismatch in tire compound no amount of air pressure or alignment changes will get them to work well together.

[Flavor 987S]

Originally Posted by Topless

As long as the tires are very similar in type, temperature, traction, and wear ratings, even different brands, they should work together pretty well.

I disagree. This is horrible advice. Especially for a performance sports car and a Porsche.

[Flavor 987S]

Dale, what are the code dates on the front tires? What about the dates on the rears? This will tell you a lot too.

[MikenOH]

Tire compounds harden with age. What you have now is a newer tire in the front with rubber as soft as it gets from the factory and tire on the rear which has probably hardened over the years. Not very conducive to balanced handling, besides the differences in how the tires are designed.

I understand everybody's financial situation is different, but mixing tires, in my experience, isn't going to get you where you want to go with the Boxster.

[Dale_K]

The rear tires are part of a matched set of very inexpensive ($300 for all 4) Sumitomo tires the previous owner put on in July 2010. I understand the risk vs reward question about mismatched tires and was willing to accept it. The new tires are listed as "grand touring" tires rather than max performance and I was willing to accept that too. The most I'm out if I junk them is $230 so it's not the end of the world.

Seeing as how I'm not getting much tire pressure advice I'll try out some different pressures and report back. I like the nice quiet ride and the ablility to rotate tires from side to side. No so good for responsiveness though.

[Topless]

Originally Posted by Dale_K

The rear tires are part of a matched set of very inexpensive ($300 for all 4) Sumitomo tires the previous owner put on in July 2010. I understand the risk vs reward question about mismatched tires and was willing to accept it. The new tires are listed as "grand touring" tires rather than max performance and I was willing to accept that too. The most I'm out if I junk them is $230 so it's not the end of the world.

Seeing as how I'm not getting much tire pressure advice I'll try out some different pressures and report back. I like the nice quiet ride and the ablility to rotate tires from side to side. No so good for responsiveness though.

Dale,
I am sad to say that tire pressure advice wont fix this. Grand Touring All season tires are just far too different from Max performance Sumis to ever be a good match. Your car will feel like it is on banana peels until you resolve this. If you like the Grand Touring A/S tires, put em on all four corners. You will get a nice quiet comfortable ride good in all weather conditions and sacrifice some grip. Maybe a good tradeoff depending on your driving style.

[Topless]

Originally Posted by Flavor 987S

I disagree. This is horrible advice. Especially for a performance sports car and a Porsche.

Sorry Flav,
I guess we will just have to agree to disagree. Been doing this for 5 years, street and track. Michelin PS2, Mich Pilot Sport, Sumitomo, Goodyear, Nitto, and Hankook. I currently have 5 sets of tires in various states of shred and 3 sets of wheels.