Wheel Question

[Jeeper31]

I have the opportunity to get a set of 17" rims to replace my 16" 968 rims. Will there be any benifit to me using the 17" over the 16"s on street or track? they are Porsche OEM 17" rims.

[Dantilla]

A larger diameter will increase sidewall stiffness. A bit more responsive steering, at the expense of ride quality.

A relatively small change from 16 to 17 will not be a big difference.

Changing wheel & tire widths is where it's easy to screw up a 944's handling.

[DMRK]

"Changing wheel & tire widths is where it's easy to screw up a 944's handling."

What to avoid?

[Dantilla]

The factory did it's homework when engineering the 944 chassis. Beautiful neutral handling. The later cars went with a slightly wider rear tire to induce a bit of understeer, which is considered safer for the average (clueless) driver.

Some like the looks of really wide rear tires on a 944. Yeah, it looks cool, but it will understeer like a pig. Too much grip in the rear plants the tail firmly while the nose gets squirrely. A 944 is most fun to drive with equal sized tires front and rear.

Of course, the problems can be masked by swapping suspension pieces- different springs, T-bars and sway bars. but what is happening is masking problems, not maximizing performance.

[Razorback1980]

According to the tech bulletins (thanks Jon and Alex for that info), when you put 17" wheels on a 944, you should switch to 968 caster blocks and slightly change the alignment. They posted the actual bulletin on here somewhere. If you can't find it with a search, let me know and I'll look for it.

[DMRK]

I found the bulletin, Thanks.

TECHNICAL SERVICE BULLETIN : 17 INCH APPROVED WHEELS & TIRES

Model(s):
1987-On Porsche 944 (with M30 option) 1987-On Porsche 944S (with M30 option)
1987-On Porsche 944 T (with M30 option)
1988 Porsche 944 Turbo S
1989 Porsche 944 Turbo
1989-On Porsche 944 S2

Group: 4
Bulletin No.: 9303

Date: September 28, 1993

SERVICE INFORMATION

Concern: Installing 17" Porsche wheels on vehicles previously equipped with 16" wheels.

SERVICE PROCEDURE

Installation Information

1. Front and rear fender well lips must be reworked and/or checked for adequate tire clearance. See Fig. 1.

2. Suspension travel must also be checked. Parts such as brake lines, hoses and brackets must have adequate clearance.

3. New caster eccentrics, rear mounts and nuts must be installed in the front control arms. This change is necessary due to a change in caster specification on vehicles equipped with Porsche 17" wheels. The specification for vehicles equipped with 17" wheels is 3'-15'-45. See Fig. 2.

4. Vehicles must have a rear stabilizer bar.

5. When adjusting vehicles to new caster specification, all alignment values should be checked at that time.

6. When summer tires are used on vehicles with 17" Porsche wheels, snow chains cannot be used. If winter tires are used, only snow chains with Porsche Part Number 911 361 924 00 may be used.

7. Tire pressures for front and rear 17" Porsche wheels is to be set at 2.5 bar (36 PSI) at approximately 20'C (68'F).

8. When using this rim and tire combination, a 17mm spacer plate must be installed on the rear wheel hub. The customer must be informed that if the emergency wheel is needed, the spacer must be removed.

9. Not for Cabriolet vehicles.

APPROVED WHEEL & TIRE TABLE

Tire size Rim size Offset Position Note

225/45 ZR 17 7,t Jxl7 AH 65mm Front Summer tires
255/40 ZR 17 9 Jxl7 AH 55mm Rear (See installation information A through G.)
225/45 ZR 17 8 Jxl7 AH 52mm Front Summer tires
255/40 ZR 17 94.@ JX17 AH 68nm Rear (See installation information A through I.)
205/50 R 17 7;-i Jxl7 AH 65mm Front Winter tires
225/45 R 17 8 Jxl7 AH 52mm Rear (See installation information A through G.)

NOTE: When using this rim and tire combination, a 17mm spacer plate must be installed on the rear wheel hub. The customer must be informed that if the emergency wheel is needed, the spacer must be removed.


PARTS INFORMATION TABLE

Description Part Number Quantity

Spacer Ring 951 331 611 02 2
Wheel Bolt 904 341 671 00 10
Wheel Nut 999 1 82 003 36 10


APPROVED WHEEL PART NUMBER TABLE

Size Offset Part Number

7;-i Jxl7 AH 65mm 96536212405
8 Jxl7 AH 52mm 96536212601
9 Jxl7 AH 55mm 96536212800
91.@ Jxl7 AH 68mm 96536212805


APPROVED TIRES AND SIZES (SUMMER VERSIONS) TABLE

Size Makes

225/45 ZR 17 Front Bridgestone Expedia S-01 Nl
255/40 ZR 17 Rear Continental Sport Contact CZ 91 NO
Pirelli P700-Z NO
Yokohama A 008P NO
Michelin MXX 3 NO or MXX NO Pilot SX


APPROVED TIRES AND SIZES (WINTER VERSIONS) TABLE

Size Makes

205/50 R 17 89 H M&S Front Bridgestone WT05
225/45 R 17 90 H M&S Rear Continental TS 750
Pirelli winter 210 Performance


SUSPENSION PART NUMBER TABLE

Suspension Parts

1. Rear Mount

Part Number Quantity Required
951 341 023 00 2 each

2. Eccentric 951 341 431 02 2 each

3. Nut (torque to 100 Nm) 900 910 115 02 4 each

END OF ARTICLE
------------------------------

[Jeeper31]

Dos this mean taht the caster blocks do not need to be changed on the 5 models listed on the top of the bulletin?