Question on hub center bore height?

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Adrian Thompson
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Question on hub center bore height?

Postby Adrian Thompson » Tue Feb 18, 2014 1:00 pm

What is the height (out from the main hub flange) of the center bore on 88 up hubs? I’m buying some Ford Focus wheels with Snow tires on them cheap to start rallycrossing this year. I know the Ford is 35mm offset not 30mm for the SAAB and the center bore is 63.3 Vs. 65.1mm. What I’m wondering is if I throw in some 3.35mm (1/4”) spacers will I clear the hub flange or am I going to have to find a mill to open it up. The car is currently buried on its wheels so measuring myself is not easy right now. I figure the wealth of knowledge on here, someone probably knows it off the top of their head complete with original tolerance spec :lol: hehe
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Adrian Thompson
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Re: Question on hub center bore height?

Postby Adrian Thompson » Tue Feb 18, 2014 1:02 pm

P.S. I assume spacers are OK for rally cross? I used to run them in Solo no issues and cornering loads are much lower in rallycross, although peak side loading could be higher hitting burms, ridges etc.

Thanks hive mind in advance.
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Adrian Thompson
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Re: Question on hub center bore height?

Postby Adrian Thompson » Wed Feb 19, 2014 10:29 am

OK some more thoughts. As everyone here knows 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.
Image

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.
As I said above, the SAAB has a hub diameter of 65.1mm, the Ford wheels are 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.
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 cheap ass 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?
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DrewP
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Re: Question on hub center bore height?

Postby DrewP » Wed Feb 19, 2014 12:33 pm

Adrian Thompson wrote: Is it OK to use wheel spacers in Rallycross. This is a cheap ass 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.



LOL. I feel you.

Yes, cornering loads are less, as long as you don't hit a rut or a berm or buried rocks or anything like then - then the side loads are much higher. That's part of how people routinely de-bead tires on Rally-X courses. (You'll want to bump your tire pressure up a fair bit to help keep the beads seated on the rims - 40-45 psi is pretty common from talking to people out here.

Spacers aren't necessarily bad as long as they actually center on the hub and the inside of the wheel so that the load goes thru the spacers as much as possibly without letting the wheel mounting face slide on the hub and put more load into the lug bolts.

You also need to make sure you use appropriately longer lug bolts (or switch to studs if you need to) in order to make sure the lug bolts have all the threads in the hub fully engaged.

Lastly, depending on rules, for a beginning entry using snow tires will likely be advantageous. Out here you can use any non-race/rally tire and still run in stock class. So snows are what everyone runs.

Running rally tires on an otherwise completely stock car out here bumps you automatically into rally class, where you're competing against fully prepped rally cars most of the time. Check your local rules.

Those are good looking wheels tho!
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Geoff
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Re: Question on hub center bore height?

Postby Geoff » Wed Feb 19, 2014 12:56 pm

Sorry but in my opinion those wheels are way to big for a 900 rallycross car. 16" wheels on a 900 are big and result in people running low profile tires. The 6.5" width is so-so but I usually run a 5" or 5.5" and skinny tires to dig in. What size are those tires? I'm guessing too wide. I wouldn't run wider than 185s.

I don't think you'll have too much of an issue with running spacers and bolts. I've never done much/any suspension type damage rallycrossing. I milled out some wheels and over bored some by accident. I've never had a problem with the wheel studs rallycrossing or rallying them (wheel doesn't contact hub flange). I'd try to mill them out if you could but if that isn't an option then the spacers and bolts probably won't be too bad, at least to try out the wheels and tires. Maybe you can spend some time with a dremel and open up those wheels :-)
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Adrian Thompson
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Re: Question on hub center bore height?

Postby Adrian Thompson » Wed Feb 19, 2014 3:09 pm

Geoff wrote:Sorry but in my opinion those wheels are way to big for a 900 rallycross car. 16" wheels on a 900 are big and result in people running low profile tires. The 6.5" width is so-so but I usually run a 5" or 5.5" and skinny tires to dig in. What size are those tires? I'm guessing too wide. I wouldn't run wider than 185s.

I don't think you'll have too much of an issue with running spacers and bolts. I've never done much/any suspension type damage rallycrossing. I milled out some wheels and over bored some by accident. I've never had a problem with the wheel studs rallycrossing or rallying them (wheel doesn't contact hub flange). I'd try to mill them out if you could but if that isn't an option then the spacers and bolts probably won't be too bad, at least to try out the wheels and tires. Maybe you can spend some time with a dremel and open up those wheels :-)


Agreed that they are a bit big. The tires are 205's. I was looking wheels for street/track so I could use the stock 15" wheels for rallycross. The just happened to come with almost new snow tires. Detroit region tends to run well groomed courses I believe so I hope these will do to start with. Long term I'd like to get some cast of rally tires, but right now I want to get out and try rallycross. Everything I've done in the past has been on sealed surfaces.

How much space is there in board of the stock wheels? Will my offset be an issue?

Thanks
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