The
Info for Sports Purposes document 4890.20-200-03-72 (see page 33-35) shows the 914/6 (on all 4, not staggered) 6"x15 for rallye, with tires spec 185/70-15;
and
7"x15 wheels for racing with racing tires spec 4.75/10.00-15 (same as on 917 www.flickr.com/photos/wbaiv/6252749070)
Info Sports Purposes to 1972 -
https://www.dropbox.com/home/914-6-GT%20his...972_english.pdf (on my dropbox pages)
- the 914/6 (flared GT) was spec'd for 21mm spacers with the 6's, and 27F/35mmR for the 7's (... also spec'd long studs & steel lugnuts for racing)
as a general rule - 7x15's were the FIA homologation spec as seen in the "factory docs"
let's also remember that the "Porsche spec performance tire" of 1970 was a 185/70xVR15 for both the 911 & 914/6
Wow, thats a lot of nice information larrym. Thanks for sharing. Mark
- IIRC the Sunoco GT used wider non-Fuchs (minilite?) rear wheels 'cuz ther was no 8" Fuchs then (the French car Ranson Webster now owns & races 9140430457 - had them when i saw it in his showroom a few yrs ago; at RRV it had fuchs on back!
http://www.914-6-club.de/PorscheClubs/pc_9...nt&tabnr=2)SCCA GCR up to 1972, generally allowed 1" wider than FIA spec; so 8x15 would have been period OK; in the 1972 GCR they went
up to 1.5" wider, but limited overall track width in both cases ... "1971 GCR stock 914/6 spec was 6x15" .... 53.58 frt, 54.41 rear track width" - on some cars, careful selection of width/backspace can yield wider wheels &
slightly more contact patch
- so that's
probably why most vintage/historic groups & PCA allow up to 8x15's - but
no x16 dia
HMSA (& other Steve Earle venues) upon petition, allowed 914/6's pure slicks on x15s (see Jon Wactor 9140430375 and Eddie Arrowsmith both running Goodyear cantilevers) because the 4.75/10's were allowed per factory 4890.20-200-03-72
the 1972 m471 "USA dealer option" only suggested 6x15's (pic) below
fwiw - to corroborate a comment above: circa 1993 Ken Mack founder of Sportech in Campbell who was a credible 914/6 racer for some yrs, said "7x16 with 225/50 frt, 8x16 rear with 245/45" so i b'ot a set of 16" BBS-RA from him to that end - obviously not "period correct" -he aligned my car to comp'tn spec & i have never changed that
(still have the wheels) - dunno if it made a diff since i never ran anything else after that (ran 8x15/9x15 BBS before that - also vintage incorrect, but scca scrutineers never looked at 'em except to see if the steel lugnuts were tight) & i also converted my frt-susp to 911 SC with underslung swayvbar on advise of another P-car guru
i currently run 4 7x16 fuchs with A/S3s all around - (let's me cross rotate for better street tire wear cuz the comp'tn negative camber is an issue, as another above post suggests) - i briefly tried 8x16 rear fuchs with 245/45 last yr, it "felt different" but the like-new Fusions were 10yrs old, so my seat-of-pants opinion is irrelevant; (i dismounted 'em & you can have 'em for free at my gate zip 95635)
- back to the original question - do any of us have experience that suggests wider rear wheels & fatter-lower-profile tires make any difference on (any) 914?
yes - i have copies of all this historic stuff - but am finding it is difficult to scan & convert some of 'em to something i can post -
Click to view attachment