wheels and tires

[Dennis]

My kit is scheduled to be finished on 13 June and I am getting ready to order my wheels. The company making the wheel I have picked (American Racing) does not make a 18x9 rim. It makes an 18x8 and an 18x9.5. The front tire recommended by FFR is a 255/35. American Racing told me that tire would fit on with the 8” or the 9.5” rim. Is there any reason for choosing one over the other? If they both take the same tire, the issue will not be fender clearance but hub and brake clearance. Maybe there will be no issue at all as long as the tire is a 255. But the salesman also said that if I bought the 9.5 I would want the backspace to be 6.25. FFR specs a 6 inch backspace for the front tire. Increasing it will put more tire inside the car. I’m a little concerned about 1) getting a 9.5” rim when FFR specs a 9, and 2) changing the backspace from 6 to 6.25. Any thoughts?

[CraigS]

I think the 9.5 will work fine. By increasing the BS to 6.25, you are placing the extra .5 inch of overall width 50% on the outside and 50% on the inside. MkIVs until a couple months ago sometimes had a fit problem at the front of the tire when the steering was turned. As I understand it the recent (3 months ago?) re-do of the body has fixed that. Hopefully someone w/ the latest body will comment.

[Jeff Kleiner]

As Craig said that extra 1/2" of width is being split both directions hence the .25" increase in backspace. I have done a 25th Anniversary body and honestly can't tell any difference in the front wheel openings. Note that I always trim back the excess flange in the wheelwells and the only times that clearance has become an issue has been when the cars were not aligned properly (i.e. not enough positive caster &/or negative camber) or had the wider 1996 and up donor spindles or used a taller than usual tire such as 255/45 rather than 255/40.

Jeff

[Dennis]

Thanks guys. I appreciate getting some feedback from someone who isn't selling the wheels. Your confirmation is comforting. It sounds like the concern is with fender fit rather than hub and brake fit (as I supposed). So then I'm guessing the 8" rim instead of the 9.5" rim would provide no benefit? Just keep it aligned and don't use a tall tire. I think I'll get a 35 or 30.

[rich grsc]

The 8" rim will not look as nice, I think the tire will look 'squeezed' once mounted. A 1/2" wider will look better than an 1" narrower. JMO

[Papa]

I'm running a 245/35/18 in the front with FFR's 18" Halibrand style wheels. I would expect no issue size-wise going with an 18x9.5 and a 255/35/18 tire. Just keep in mind that wheel center designs can also come into play with brakes. The FFR wheels center design is pretty flat, but some wheel designs are not. Ask about brake clearance before you buy.

Dave

[Dennis]

You guys are great. More helpful tips. I will opt for the 9.5 and ask about brake fit. Dave when you say the Halibrands are flat, you don't just mean the back of the wheel where it attaches to the hub right? You're talking about the whole wheel. If you take a cut away of a wheel from the side, the spokes at the outside of the rim are no further from center than the spokes at the center of the wheel. I'm getting what I call a Mag wheel. It's a 5 spoke design that came out back in the 60s I think. There is a cutaway view of the wheel and it is pretty flat. But I will ask about brake fitment. Thanks.

[Papa]

You guys are great. More helpful tips. I will opt for the 9.5 and ask about brake fit. Dave when you say the Halibrands are flat, you don't just mean the back of the wheel where it attaches to the hub right? You're talking about the whole wheel. If you take a cut away of a wheel from the side, the spokes at the outside of the rim are no further from center than the spokes at the center of the wheel. I'm getting what I call a Mag wheel. It's a 5 spoke design that came out back in the 60s I think. There is a cutaway view of the wheel and it is pretty flat. But I will ask about brake fitment. Thanks.

You've got it. The Halibrands are a flat plane from the hub all the way out to where the spokes tie into the barrels. The shape of the barrels can also play in as some wheels can be smaller diameter near the center than at the edges.

https://thefactoryfiveforum.com/attachment.php?attachmentid=128654&d=1589986014

To get the deeper dish on negative offset wheel designs, sometimes the spoke designs can push further toward the rear edge of the wheel where they contact the barrel.

Dave

Update: Here is a good link to review for you

http://www.vacmotorsports.com/measuring-brake-clearance.html

[Dennis]

Great!! Thanks everyone for taking the time to help. You area the best. I believe I am ready to order.