Backspacing for custom 17" tru design wheels
 

I just purchased a set of fuch cores that were sent to Jim@ TruDesign. I'm having him do 17x8 fronts and 17x9.5 rears. I know there are a few Pelican members here who have done the same. I'm hoping you can share some info on backspacing specs. They are going on a 1983 911SC Targa.

Maybe 1986911 and or Jakester can chime in. I've read they had Jim fab some up for them. Thanks.

Butch

I have 16x9.5 and the offset was -8. I got them from a friend and fellow Pelican who was using them on his backdated 911sc. The lip of the rim was right at his fender so he decided not to use them. I put them on my turbo and ha to use 7mm spaces to clear my brake calipers.

TruDesign did mine which are the same widths as yours but the backspacing for a spacer-less widebody is way different so unfortunately I can't help on the dimensions.

Jim does VERY nice work, you won't be disappointed!

http://forums.pelicanparts.com/uploa...1317154476.jpg

I did 7s on the front with a 4.73 BS. I think 8s will be too wide and have a tire look non-rice. 225 -45-17 fit the front with a rolled lip. I used stock BS on the rears and had to grind the eccentric nuts some to clear. I run 275-40-17 back there on 9" wheels.

Here's a huge topic on Lindsey vs. TruDesign

http://forums.pelicanparts.com/porsche-911-technical-forum/389304-trudesign-wheels-lindseys.html

Ryan Williams had a really nice set done by TruDesign.

http://forums.pelicanparts.com/porsche-911-technical-forum/430176-tre-elephant-racing-pelican-parts-thank-you.html

My 9.5" wheels have ET19.05 and backspace is 6", these wheels are as close to the trailing arm as can be w/ a 275 tire
http://forums.pelicanparts.com/uploa...1317159358.jpg

Thanks for the replies. Jim wasn't too concerned with the rear wheels. He thinks he knows what offset will work for the rear. It's the 8" fronts he's not 100 percent sure about. When I mentioned that he made sets for at least a couple of guys here, he asked for offsets of what was asked of him to make and if they worked out fine. He'd settle for the customer's name so he can look up the specs. I have neither. Any help will be greatly appreciated.

Butch

I have a set of 8x16s in the front and they like 5.75" of backspacing. They were "incorrectly manufactured" with a backspacing of 6.125", so I was afforded the wonderful opportunity of trying different spacers to get them to fit perfectly. A .375" spacer worked best, so that would equate to a backspacing of 5.75". I run a 245/45-16 tire on these wheels.

Hope this helps.

Edit: FWIW, I have 9x17s in the rear running 275/40s and they have a backspacing of 5.5".

Thanks for sharing that info Mike. Now I have something to go by.

Butch

Front 8s want an ET of ~25-31, I'm more comfortable at the upper end of this range

ET25 corresponds to a backspace of ~139mm(5.5") ET30 ~145mm(5.56") but this is dependant on the flange width too. BBS and Fuchs have narrower flanges than Fikse/Forgeline etc. Flanges vary from ~.35" to .5", flange variation is one of the things that makes ET a lot easier to use when fitting wheels.

Bottom line front 8s want ET 25-31

Bill, wouldn't ET30 of about 145mm be closer to 5.71"? Would ET31 equate to 146mm of backspacing or about 5.75"? 5.75" works really well for me. 5.875" works, but the wheel is very close to the dust can on the strut.

As I said it depends on the flange width, which varies fro, .35"(Fuchs0 to .5"9most aftermarket wheels)

http://members.rennlist.com/1976c38/...AQ-diagram.gif

here is an old compilation of actual measured wheels, it needs to be updated and a few corrections done but is mostly accurate

Wheels

Ryan Williams (surflvr911sc) is the red car in one of the links I shared. I traded messages with Ryan about his wheels a few years back and he said he was really pleased with the wheels and Jim. Incidentally, I recall one pair of wheels were spaced not quite right at first and had to be redone? I don't mention that to slam Jim. I mention it to point out that Jim is a standup guy and made things right.

I agree the 8 in. fronts should have an offset that is upper 20's or 30 tops. I have run 16x8 BBS RS fronts on my '87 for years. They are a somewhat rare offset of +28mm. This offset clears the fenders better than the typical +23mm of the 951 16x8 Fuchs wheel or equivalent 16x8 BBS RS wheel with the same +23mm offset. But the +28mm puts the inner rim edge or tire sidewall very close to the strut's shock absorber metal protection "can." You can remove the can and replace it with a rubber accordion bellows. Bilstein makes one that is a perfect fit. The part number is VW# 357 413 175A and is commonly found on 1997-2000 Golf III and Jetta III.

Gentlemen,

Thanks again for all the replies. 'Can't wait for these wheels to be built.

Butch