This is a long post to ask a simple question. If you don’t want to read my musings and thoughts the question is ‘Is it OK to use wheels spacers in rally cross’. Now read on or skip it as you wish!
OK, if I ever get my fat lazy ass back into the garage I want to finish up my SAAB 900 for rally cross, to whit wheels.
The 88+ SAAB 900’s have the very common in Europe 4x108 bolt circle, but that is far less common over here. Thankfully Ford has sold millions of FWD cars with the 4x108 to choose from. I’ve just picked up a cheap set of what I think are some of the best look stock Ford wheel of the last 15 years. The 16x6.5 6 spoke Cougar wheel. This is the pic from the ad on eBay.
After they didn’t sell I contacted the seller and got them for $200 with almost new Toyo snow tires (I didn’t even know Toyo made snow tires). Now I know snow tires aren’t ideal for rallycross, but I couldn’t find any used rally tires and didn’t want to spring big bucks on tires for something I’ve never tried. I need tires no matter what so these seemed to be a good compromise. Enough of that. Let’s make these things fit.
OK, the big issue is the SAAB has a massive center bore of 65.1mm, the Ford wheels have a still large 63.9mm so hub centric rings won’t work. My first thought was to open up the center bore on a mill, time consuming but possible. Then I started thinking of offset.
Warning gross rounding in the next couple of paragraphs to keep # in simple increments.
The stock SAAB 5.5” wheels have an offset of 39mm, SAAB 9000’s have 33, so not a great deal. Theoretically that puts the distance from the mounting face to inside edge of approx.. 109mm. Allow another 5mm for a flange etc. and let’s call it 115mm.
The Ford wheels have an offset of 48mm and are 6.5 vs. 5.5” wide. So a theoretical offset off131mm, add 5mmish for a lip and we’re talking 135mm. That’s 20mm more on the inside which is quite significant. I’m not sure of the clearance, but I’m guessing a spacer will be needed. Standard off the shelf chepo universal spacers (that I happen to have from autocrossing) are ¼” or approx.. 6.5mm that would reduce the increased space on the rear from 20mm to around 13.5mm which I assume will give me clearance.
So assuming the hub ring is less than 6.5mm I think I can just use the spacers and not have to machine the wheels.
I never used to worry about spacers when autocrossing, even on R comps. Everyone did it to take advantage of the + ¼” allowance in the stock rules. But with rallycross while the cornering loads are much less, the peak loading for hitting berms or ridges, ruts etc. is much higher. Is it OK to use wheel spacers in Rallycross. This is a typical cheap ass GRM project funded by $25 per month from the family kitty and whatever I can raise by selling old car parts from past projects, so custom made spacers with hub centric adaptors are out of the question.
Thoughts?
