Fikse offset numbers ???

[Bill Verburg]

Originally Posted by wildcat077

Bill,

One question regarding the ET on my 7.5 and 9 inch Fikses.
Since the inner barrel on both wheels is the same with a backspacing of 6 inches would that mean that they are both ET 18.6 ? My front wheels are spaced out 1/2 inch in order to clear my calipers and Steve Timmins modified hubs...
The only difference is the outer lips which are 1.5 for the fronts and 3.0 inches for the rear !

Regards !
Phil

yes, the Fikse 7.5 that I have seen are ET18.6

Back space (mm) Front space (mm) Edge to edge (mm) is


132.84 83.06 215.90

[Jeff Alton]

The Fikses(if they are classics like FM10, FM etc and not the Profil series) 7.5's are generally et37. The 8.0 would be ET30 and the 9.0 would be et18.

All of the 17 inch Fikse classics use the same hub pad height and they just maniplulate the rim shell stack. If anyone needs the rim shell stacks that go with the different widths/offsets let me know.

If you go with the Profil series you have the choice of multiple hub pad heights and can fine tune the offset much better.

Cheers

[Bill Verburg]

there are/were 2 different 7.5x17 Fikse


width(in.) Factory +o/s(mm) Calc +o/s (mm) Back space(mm) Front space(mm) Edge to edge(mm) Edge to edge(in)

7.5	   18.6	        18.6	         132.84	       83.06	       215.90	       8.5

7.5	   31.3	        39.69	         147.64	       68.26	       215.90	       8.5

8.0	   18.6         18.6	         120.20	       83.00	       228.60	       9.0

8.0	   31.3         31.8	         146.05	       82.55	       228.60	       9.0



9.0	   18.6	        18.5	         145.54	       108.55	       254.00	      10.0

how close the calc ET is to the factory ET gives you an indication of the accuracy of the supplied #s

Jeff is correct, backspace of 6" is probably the second wheel, ET31.3

[paulgtr]

not to sound stupid, but how do you interpret those numbers to choose the right wheel?

[Bill Verburg]

Originally Posted by paulgtr

not to sound stupid, but how do you interpret those numbers to choose the right wheel?

You now have
7ET23.3 & 8ET10.6 you don't say what tires but probably 205/55 & 225/50

in front the biggest that you can use are
8ET25-31
and in back
9ET15
or
9.5ET19

for tires in 17
235/45 or 235/40 or 245/40 in front
255/40 or 265/40 or 275/40 in back

for tires in 18
235/40 or 235/35 or 245/35 in front
265/35 or 275/35 in back

the bigger the tire the more work to fit it.

tire height is also a concern, 911s originally cam w / 185/70x15 @~25.7, The shorter the tires the easier to fit, certainly keep it under 25.7"
185/70 x15 25.7
205/50x15 23.1
205/60x15 24.7
205/55x15 23.9
215/60x15 25.2
225/50x15 24.0
205/55x16 25.0
225/50x16 24.7
225/45x16 23.7
245/45x16 24.6
225/45x17 25.0
235/40x17 24.4
235/45x17 25.4
245/40x17 24.7
255/40x17 25.0
275/40x17 25.7
225/40x18 25.1
255/35x18 25.0
265/35x18 25.3
275/35x18 25.6
285/30x18 24.8
275/40x17 25.7
245/45x16 24.6

you also need to be concerned w/ f/r height and width relationships

for performance shorter sidewalls are preferred, ie 30 series is better than 35 is better than 40 etc.

JMO, but for a typical 911
8x17 w/ 235/40 & 9x17 w/ 265/40 is a great compromise and not too difficult to fit

or 8x18 w/235/35 & 9x18 w/ 265/35

back in the day 235/40 on 8x17 & 265/35 on 9.5x17 was a great setup but the 265/35 x17 tires disappeared and I had to go to 235/45 & 275/40 which was ok but I was never as happy w/ as the previous set. Currently use 225/45 & 255/40 because that car isn't tracked anymore

[Jeff Alton]

You are right Bill, the 7.5 could be configured both ways, not listed as a current build but could be done again.

Bill has good tire advice too. We typically go with a 225/45/17 front on an 8.0 and a 255/40/17 rear to keep the heights in check and there is good availablilty in both street and R-compound.

In 18 we run a 225/40/18 on an 8.0 and a 255/35/18 on a 9.0 or 9.5. The problem is this limits you to a hoosier as no one else makes a 255/35/18, yet..... There may be others but we have only specced this out with the Hoosier R6 and not spent much time searching for another tire....

Cheers