TJ993

WIDER FRONT WHEELS ON A 993? How will this affect handling? Before I buy two more sets of rubber!

2nd Question? Has anyone tried the square set up?

Question # 3: has anyone tried INSTALLING an OEM P car Rear 8.5x17 width On the Front of a 993?

996 Carrera 2 or Boxster 987 - 8.5 inch ET50

History 97 NB Carrera. I have turbo nb wheels – look pretty but the city ride deplorable

OK Tired of driving on 18’s on our lowsy streets! Nice on track / highways but too valuable to abuse for De, ok yes want to keep purdy lol.

This year I switched tire size for one last stab – think these wheels are going 4 sale shortly, but changed tire sizes to 225/45zr18 and 265/40zr18 to increase sidewall for comfort driving city streets.

In anticipation of driving De and not happy with street ride, I have purchased two sets of cup II wheels.

Hopeful for a smoother ride on Cup II 17's
Next ? > How will these proposed tire size changes affect handling?


With the stock tire size if I understand correctly using 205/50 17 on 7 inch front with 255/40-17 on 9 inch rears = lots of understeer.

The Recommended size using 7 inch front cup II wheels to reduce understeer is install a 225/45 – 17 tire.



Tire rack states a Michelin 4S 225/45-17 requires a minimum 7 inch width to max 8.5 inch wide wheel.

Based upon a (Bill V) recommendation of widest wheel and skinniest tire to improve turn in, I am thinking buy or install 8.5x17 oem wheel and go with 225/45 tire width and largest rear on 9 inch for more bite say 275/40 instead of 255/40-17

So, in conclusion, if you agree with the 8.5 front? should I go one up again for balance/turn-in with a 235/45 front with 275/40 rear for DE?

Square set up 9 and 9 ? Thoughts?

Thanks for reading

paulkromz

..

Mark in Baltimore

I would go with a 235/40-18 up front and either a 285 or a 295 in the rear. Hopefully, you have adjustable sways and shocks and can adjust them as you prefer to deal with any understeer. I've managed to stuff a 245/40 Hoosier R6 up front.

TJ993

Hi Mark
I did run the turbo 18's with 235 40 & 265/35. Car handled well imho as a newbie DE guy.
It made me realize I have to do a suspension refresh and some tweeking.
I think turn in needs help but started at the back - as I have been led to believe these arms wear out first or sooner than front end.

Second I realized need suspension adjustability. I have HD b6 front and B8 rears w row springs and M030 sways.
While working on acquiring suspension arms and bushings I figured check out the 17's.
Get a few DE rides in before the season passes me by. Plus the 17's should make city rides less harsh, hopefully more pleasant than the 18's
If cost were no issue I would just do it all but parts costs continually rise so its gradual changes to find what I like
Thanks Tom

Bill Verburg

wider front wheels w/o any other change reduce under-steer.

don't know why you would want a square setup on a tail heavy car, that will increase over-steer, the faster you go the more over-steer, for A/X maybe, but for any thing else nope

8.5x17 front want ET54 +/-, I've never seen a rear 964 or 993 8.5 but id the 996/Boxster wheel is 8.5ET50 it is aggressive for a front, I did use 9ET50 for a while but the width & ET made fitment of a tire bugger that 225/40 impossible unless ride height was compromised.




When choosing tires you need to balance the needs of each end wrt width and aspect ratio and also balance tire height f/r a 993 will want a spread of around 40+/- and close to equal height

in 17
8.5 w/ 225/45 & 9 or 9-10 w/ 255/40 is a good setup, on the same wheels 235/40 front 255/40 rear reduces under-steer a bit 235/45 front will be undesirably tall but 235/40 & 275/40 is ok again on 8.5 & 9.5 or 10 here the issue is that though the tires match in height there is a pretty steep inertial cost mostly due to the taller height and an additional pretty steep gearing cost on top of that. All in all I'd avoid that setup

for ride quality you want the narrowest wheel for a given tire and for performance you want the widest

all the above 17s will suffer performance wise wrt 225/40 & 265/35 x18 on 8 or 8.5 & 10 but will have a nicer street ride

TJ993

Hi Bill
I have looked at all stock wheels. There are a number of nice designs for the 18 inch wheels. Next I considered tires. The combined weight for De, imho put them off the table of consideration at 56 pounds each Unless I go with Turbo wheels. I would prefer the solids or something else for DE abuse.

That’s why I thought lets try 17 cups. I am losing 10 pounds a corner. Bonus! Miles of fun at an affordable cost for wheels and reduces rubber costs.

Compared to 18’s I can buy Two sets of 17 inch rears plus One pair of Fronts vs one set of 18’s for same $.

Specification Sidewall WIDTH Diameter Revs/Mile Difference Weight

205-50ZR17 Pirelli R 4.04” 8.4W 25.4 828 19 LB
7 INCH ET 55 # FRONT 7 INCH CUP ii Part # 993 362 124 00 WEIGHS 9 KG 19.8416 POUNDS

WEIGHT 38.84 POUNDS

More Oversteer



225/45ZR17 Mps 4S 3.54 07.5w 25.0 833 21 LB

225/45ZR17 Conti Ex S 07.6 W 25.0 OD 831 21 LB

FRONT 7 INCH CUP ii Part # 993 362 124 00 ET55 WEIGHS 9 KG 19.8416 POUNDS

Total weight ABS Issue w/ Michelins 40.84 w/ Continentals



235/45ZR17 Mps 4s 07.8 W 25.4 821 22 LB

FRONT 7 INCH CUP ii Part # 993 362 124 00 ET55 WEIGHS 9 KG OR 19.8416 POUNDS

Total weight Fitment on 7 inch ?issue? 40.84

Rear Wheel

255-40ZR17 Mps 4S 8.7 26.0 799 25 LB

255/40ZR17 Conti. Ex S 8.8 25.0 831 23 Lb

REAR 9 INCH WHEEL Part # 993 362 128 00 ET55 WEIGHS 10.15 KG OR 22.38 POUNDS

Total Weight 45.38 w/ Conti’s

Making the ABS 5.2 work with the Michelins appears to be a concern considering overall diameter and therefore Revolutions per mile.

Whereas the Continental Extreme Sport matches Revolutions at 831 per mile > Looks like optimum ABS!
It would appear I have found an affordable Fun street tire for DE solution.

Consider durability
Do you think the Cup II design can stand up for awhile?
I anticipate they will last awhile and that buys me time to shop for 8.5 x 18 wheels and unload the NB Turbo wheels.

TJ993

For the 18 inch wheels: Street Conti Ex S

235/40/18 08.1 wide Diameter 25.4 Revolutions RPer Mile 818 Weight 22 LB Conti = Less UNDERSTEER

265/35/18 09.4 wide 25.3 NOSE UP R p m 821 Wt 24 LB RUNS COOL

BEST TRACK SET-UP

245/35/18 08.6Wide 24.8 R p m 838 Wt 21 Lb on 8.5 x 18

285/30/18 10.1W 24.7 R p m 841 Wt 24 LB on 10 x 18

I see it now Bill.
Thanks Very Much! I greatly Appreciate your ongoing support
TJ

ps Need to get this down on chart format - Excel.
I will send it via pm to those interested

Bill Verburg

Michelin does not offer a 4s in 255/40x17

Cup2 is as durable as any other factory wheel

Here's a comparison of going from Speedlines 8 & 10 in 17 to Cup 1 in 17, there is no Cup2 in 10 so I used the widest alternate which is similar Cup1 in 9.5, all the tires are RE71

You do gain ~8lbft of torque available for accelerating the car w/ the 17s, you also get a better ride due to the bigger sidewalls(Cup2s in 9 would be even better in this area) you lose in lateral grip and turn in.


Here's a comparison w/ lighter 8.5 fronts of 225/265 & 245/285. The 245/40 & 285/30 is the best setup for 993 performance



and here is a comparison on 225/265 & 235/275 all 18s, the 235/275 will also give a little better ride that 225/265 but w/ an inertial & gearing cost

aircooledpurist

I bought 17 inch cup II 's to use as my standard OEM set up while I figured out what I was going to do for an upgrade. I'll tell you what.... the ride/handing balance is about perfect.

Im running Yokohama tires now. I'm going to have the cups refinished OEM color and clear, get silver centers, and fit Michelin Pilot sport tires. May call it done right there

pp000830

Why?

TJ993

Hi Andy
Front Turn In
TJ

TJ993

Stock 7 and 9 wheels/ Tire size?
Thanks TJ

Madturk

Amazing information here.
Some of guys are a wonder to this from. I totally appreciate the input.

im going for a new set of RE71Rs in 18 MY02 wheels
235/40/18 upfront. I had understeer I can live with a tiny oversteer.
275/35/18 in the rears. I was afraid I might run with 285s in the back.

I also have a 17 Cup2 wheels
Nitto NT01s
225/40/17 upfront
255/40/17 in the rears.
This is I think the perfect setup

How much air would be optimal for these tires?

32 or 34 all around?

SwayBar

31 psi front
32/33 psi rear

Madturk

I’ll try that. Thanks