Information on wheels, weights and offsets at the bottom!
Click here for TIRE FITTMENT CHART
Click here for Wheel Fittment and Offset
Chart
ABOUT WHEELS AND WEIGHTS:
You can only put newer 53mm offset wheels on yor turbo if you use 1" spacers.
Offsets as follows:
911 -89 10.8 in 7 or 8", 23mm 9" (extra 1/2" to inside),
23mm fits well
944 -86 23mm
944 87- 53mm except 9", which may be 53 or 60mm
928 all 60mm
964 (C2/4) 968, 993 narrow, 993tt/C4S/C2S front 53mm, Rear 53mm or
70mm (9x16" only)
993 tt/C2S/C4S Rear 40mm
Factory 993 16" wheels are 70mm rear, and look silly on anything!
Must have been a marketing
ploy to encourage upgrade to 17" Cup wheels.
Spacing difference
911 -> Widebody flares, 1" front, 2" rear with 930 factory flares,
stock suspension
911/944 early -> late wheels 1" all around works well.
CAREFUL ON 944turbos - most 911 fuchs will not clear front calipers!
Weights:
I ued a fairly accurate bathroom scale for the following weights.
They may be off but they wre all double checked and off the same scale.
Here's a sampling of wheel weights, in lbs:
7x16" 951 phone dial pcast 18.5#
8x16" 951 phone dial pcast 20#
7x16" "dish" Forged 18,5#
8x16" "dish" forged 20#
7x16" 951S FORGED 18.5
8x16" 928 CS FORGED 19
9x16" 951S/928CS FORGED 20
6x16" 911 fuchs 17
7x16" 911/951 fuchs 18
8x16" 911/951 fuchs 19
9x16" 911 fuchs 20
7.5x18" HRE 504 cast ctr 3-piece 16.5
9.5x17" " " 18
11x17" 19.5
7.5x17 Factory 993 pcast 18
9x17" Factory 993 pcast 19.5
7.5x17" Mille Miglia C2t style (late) 24
9x17" " " " 26
7.5x17" Mille Miglia C2T style EARLY 25
9x17" Mille Miglia " " 28
7.5x17" Borbet C2t style (EARLY) 28
9x17" Borbet C2t style (EARLY) 30
7x9" FACTORY C2T pcast 22
9x17" Factory C2T pcast 23.5
Interestingly:
951 Aluminum spare -w- tire 26
911/944 steel spare -w- tire 34
The aftermarket wheels weigh 6-10 lbs more than similar factory
wheels.
That is ALOT!
I was also surprized at how light the HRE wheels are even with cast
centers.
Phone dials are also much lighter than I expected.
Speedo Error and Plus Sizing
Speedo error is easily calculated. You can use the following TIRE FITTMENT CHART or calculate it yourself
Examples:
Wheel dia + 2* SectionWidth * Aspect / 25.4 (mm per in) = dia in inches.
Circumference = 2*pi*Dia, so diameter will suffice.
205/55/16 diameter = 16" + 205*0.55*2/25.4 mm/(mm/in) = 24.87"
225/50/16 = 24.86
245/45/16 = 24.68
255/40/17 = 17" + 255*0.40*2/25.4 = 25.03 (+1%)
275/40/17 = 25.66 (+3%)
315/35/17= 25.68 (+3%)
335/35/17 = 26.23 (+5.3%)
225/40/18 = 25.09 (+1.5%)
285/30/18 = 24.73 (-0.7%)
335/30/18 = 25.91 (+4%)
Dr. Steven J. Timmins
Instant-G Inc.
Newark, DE 19713
(302)456-0630 evenings/weekends.