Reddy Kilowatt

Has anybody stuffed a 255/35-18 in the front position yet? This would be on a 9" wheel w/ ET51 offset. I had a 245/35-18 on there before, but that's a hard size to find, at least in the same tire as the 285/30-18 I've got on the back (10.5" wheel w/ ET57 offset). Any thoughts? If I can get away with the 255 in the front, I can use Yokohama AD08 and other selections (Bridgestone RE050, Hankook, etc) up front. Any other ideas on sizing?

EDIT: FYI, this is obviously not for the MY02 wheels shown in my avatar, nor related to my recent tire inquiry, although brand/tire recommendations there are obviously helpful for my other wheels.

kjr914

I've got 245/35-18 on stock 993 turbo hollow spoke wheels (8" front). I believe I get a little rub at times (could be those times spinning on AX track....), but I'm REALLY low (at/below RS). Not exact answer you're after, but at least a data point.

trophy

I have a 255 35r18 on the front of mine with a 9" rim, have to check the offset though. I am at below RS ride height and with about 3 degrees of camber and have no rubbing issues. When I first put them on I was at RS +10mm and about 2 degrees of camber and still no rubbing.

Edward

Wow, that's a lot of rubber on the front, especially on a NB!!! Not sure why you'd want to, but to each his own.

Edward

trophy

big rubber = ZERO under steer.....

Paul902

Neg three!??! Trophy, you don't mess around!

Reddy Kilowatt

Yeah, the PO worked with a racer buddy and custom-specified the wheels to match up. Here's what they did:

Front
9" wheel ET51
245/35-18 Toyo T1R has a max wheel width of 9"

Rear
10.5" wheel ET57
285/30-18 Toyo T1R has a max wheel width of 10.5"

They wanted to increase the rubber width to the max, particularly at the front to reduce understeer. They also wanted the tires "stretched" as much as possible relative to the wheel width to stiffen them up. The 255 width gives up some of that stretch and might push the limits of the wheel well.

I'm open to suggestions.

EDIT: It looks like some 235s (depending on brand/tire) might be a reasonable front option, though I need to watch tire diameter. Is there an envelope of tire diameter (or revolutions/mile) that I need to stay inside of?

Bill Verburg

The PO was a very smart cookie!

What o/s is used on the 10.5's?

I've used 8", 8.5" & 9" fronts w/ 10" rears, always w/ 225/265 tires

currently 8.5, which I like best

to reduce the 993 push
first choose spring rates that lower the f/r spring ratio down into the .6range
second use adjustable sways
third use 8.5 or 9" wheels in front & 10s w/ 245/35 & 285/30 tires(but even w/ 225/265 push is mostly gone)
fourth use monoball tie rods
fifth get a good track alignment
sixth firm up all the bushes a lot of push comes from bushing deflection, particularly in front

Reddy Kilowatt

ET51 up front
ET57 in back

race911

Sure, you CAN stuff as-wide-as-possible up in there. But until you're on lap record pace, it kinda gets to "what's the point"? And funny how sometimes not running the widest possible is quicker. Very tire manufacturer/model dependent, though.

This is where data gathering, and serious interpretation, pays off.

trophy

It is what the tire data is asking for, with temperatures, pressures and wear patterns...

At the moment the 255 is an experiment, we are using the traqmate data and temps etc to determine if this is a viable option... Cornering speeds and g-forces are slightly higher, however I am loosing top speed.... More data, more analysis...

Edward

Ummm, ok.

FWIW, I have ZERO understeer with 225 and 255 17s (stock Cup IIs). But I chose to get there through suspension/alignment. Silly me...


Edward

race911

What lap times/where? Only thing I have to compare was Willow with the '92 C4 that worked OK on those tires with the setup I had. ~1:33. Buttonwillow (usual config w/ sweeper) was about 2:05. Would have had to run non-streetable springs if I wanted to run 245/275.

Edward

Hey Ken,

Please bear in mind you addressing a rank middlin driver here! And to that point, your previous post WRT lap data is, of course, indisputable since data is the real deal; "feel" deceives. And finally, I was being a bit of a smarta** ...mea culpa

But in truth, I did go to some lengths many, many moons ago to get my 993 neutral on the track, albeit still remain a good daily driver. I ended up with PSS9s, good alignment, cornerweighted, and an RoW rear swaybar (21mm, IIRC) which alone made a world of difference. The car is, in truth, neutral and easily coaxable into under/over steer ...or correct fast driving
I even had a pro driver (ex-Indy guy, yeaow!!) drive me in my car and he liked how "such a heavy car" (lol!!) felt and felt very intuitive, even with modest R-comps ...this at Streets of Willow which as you know is rife with turns with nary a straight. As for me, I won't share my WSIR or Buttonwillow times as that would be publishing truly embarrassing data that could haunt me forever
...lol!!!

Edward

Martin S.

You weren't THAT slow. I remember running Buttonwillow with you in the fog..now that was a trip!