How much backspace/offset on a rim?

I'm looking at a different set of rims for 'The Toy'. They're 17"X9" with an offset of 50mm (assuming positive). I know my stock ralleys have a 4" backspace so my question is: what is the maximum backspace a stock suspension setup will handle?

If the number is smaller in the rear than the front, will using spacers on the rear cause short or long term damage to the bearings? Or any other drivetrain/suspension parts?

I haven't had the car up off the ground to check the measurements myself but hopefully will get to that yet this weekend. The eBay auctions end soon so I need to figure this out quick. If you're curious what they look like click here for a 5 spoke version or click here for a 10 spoke version.

Thanks Gang!

|UPDATED|7/25/2004 8:06:06 PM (AZT)|/UPDATED|

Hey Jim...

I don't know what the price is on the eBay rims but I just saw these in the latest Corvette Central catalog...17" X 8" ZR1 style rims made specifically for Sharks with proper backspacing, new lug nuts and center caps for $719.95 a set.

Silver

Hyper Black


Matt

|UPDATED|7/25/2004 11:26:30 AM (AZT)|/UPDATED|

Thanks Matt - those are sharp wheels! But the eBay auctions I've been watching (and several have ended already) have been $400 or less.

I didn't get a chance to get 'The Toy' up in the air to check space availability, but would someone check my math please.

9" width equals a 4.5 inch centerline.
+50mm offset (approximately 2") makes for a 6.5 inch backspace.
add an 1.5 inch spacer and that brings the backspace down to 5".

That makes it an inch more than my stock ralleys, right? There should be that much room on a stock suspension setup shouldn't there? I'm more worried about clearance for the rear wheels than the front. Adding the spacer up front may cause some rubbing when turning tight.
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Jim O.
Save the Wave...!!!

I wouldnt think there would be room

there isnt an inch between the ends of my leaf spring and my tires.

Jim, on my 78/79's with 8inch rims, 4inch backset, I cannot get my fingers between the parking brake cable bracket on the trailing arm and the tire. It's that close. The exhaust, probably different from yours tho, is even closer. 5 inch backset might be a bit much.
Mike

Thanks Mike! I guess I really need to crawl under the car to see for sure. I would have thought that the larger diameter wheel would have some extra clearance over a 15" with the same backspace.
I'll keep ya posted!
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Jim O.
Save the Wave...!!!

While I haven't had the opportunity to get the car up in the air to fully check out clearances, I did crawl under it abit to see what I could see.

It seems like there would be enough room for a larger rim to clear the caliper and plenty of clearance from the exhaust system. What concerns me though is the spring end. There was less that 2 inches between my current tires (P215/70s) and the end of the spring. That might rule out going to the 17" wheels that I REALLY like as I'm sure that the new tires (whatever size they would be) wouldn't clear that minor suspension point.

Any other thoughts or comments?
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Jim O.
Save the Wave...!!!

are the wheels you really like available with a different offset..

most of the modern wheel places allow you to pick your offset.. they make em how you want them.

takes a little longer to get them.. but I did some looking last night and just about every wheel i looked at had offset options

You can go outward a bit, but never closer. My stock wheels and 255/60/15 clear the spring and park cable by a max of one inch.

cthulhu said: are the wheels you really like available with a different offset.. ...

I'm sure they are if I were buying new ones. The budget for wheels AND tires would get blown bigtime if I bought new wheels. So far I've just been browsing the eBay auctions and the norm for the offset has been +56mm. (btw - they're late model Camaro wheels)
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Jim O.
Save the Wave...!!!

|UPDATED|8/5/2004 9:50:25 AM (AZT)|/UPDATED|