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Topic: How much backspace/offset on a rim?

in Forum: C3 Engines, Driveline and Handling


How much backspace/offset on a rim?

Posted: 7/25/04 11:12am Message 1 of 22
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Burke, VT - USA
Joined: 1/23/2002
Posts: 7313
Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
SOLD - "BLKBRRD" - '78 Pontiac Trans Am
"BLUBYU" - '04 Coupe
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|



Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

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How much backspace/offset on a rim?

Posted: 7/25/04 11:26am Message 2 of 22
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Fountain Valley, CA - USA
Joined: 9/11/2003
Posts: 407
Vette(s): 1969 Daytona Yellow Coupe - ZZ4/4 speed, Hurst shifter, Griffin aluminum radiator w/ Dual Spals, March Serpentine Pulley kit, Hookers with STS Racing Baffles, VB&P Suspension bits, 17" AR Hopsters, L-88 Hood
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|



How much backspace/offset on a rim?

Posted: 7/25/04 6:23pm Message 3 of 22
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Burke, VT - USA
Joined: 1/23/2002
Posts: 7313
Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
SOLD - "BLKBRRD" - '78 Pontiac Trans Am
"BLUBYU" - '04 Coupe
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.
_________________________________

Jim O.
Save the Wave...!!!
|wavey|


Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

How much backspace/offset on a rim?

Posted: 7/25/04 8:41pm Message 4 of 22
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Hot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
I wouldnt think there would be room

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


How much backspace/offset on a rim?

Posted: 7/25/04 8:44pm Message 5 of 22
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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


How much backspace/offset on a rim?

Posted: 7/26/04 9:45am Message 6 of 22
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Burke, VT - USA
Joined: 1/23/2002
Posts: 7313
Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
SOLD - "BLKBRRD" - '78 Pontiac Trans Am
"BLUBYU" - '04 Coupe
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! |thumb|
____________________________________

Jim O.
Save the Wave...!!!
|wavey|


Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

How much backspace/offset on a rim?

Posted: 8/4/04 9:08pm Message 7 of 22
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Burke, VT - USA
Joined: 1/23/2002
Posts: 7313
Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
SOLD - "BLKBRRD" - '78 Pontiac Trans Am
"BLUBYU" - '04 Coupe
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. |sad|

Any other thoughts or comments?
____________________________________

Jim O.
Save the Wave...!!!
|wavey|


Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

How much backspace/offset on a rim?

Posted: 8/4/04 9:55pm Message 8 of 22
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Hot Springs, AR - USA
Joined: 4/24/2004
Posts: 3236
Vette(s): 69 Conv #'s match 427, TKO-600/.64, 3.36HD-Posi, HT, T/T, PS, PB, PW, SP, Leather, Comp XE264HR & Roller Rockers & Lifters, Air-Gap RPM intake, Holley St Av 770 VS, MSD 6AL+Dist+Blaster SS, K&N, Jet-Hot Hooker Side-Pipes, Steeroids, Al Rad, Spal Fans
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


How much backspace/offset on a rim?

Posted: 8/5/04 7:38am Message 9 of 22
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CUYAHOGA FALLS, OH - USA
Joined: 12/2/2003
Posts: 6424
Vette(s): 1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!
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.


How much backspace/offset on a rim?

Posted: 8/5/04 9:50am Message 10 of 22
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Burke, VT - USA
Joined: 1/23/2002
Posts: 7313
Vette(s):
SOLD - "The Toy" - '70 Convertible
SOLD - "The Beast" - '90 ZR-1 (#682)
SOLD - "Betty" - '28 Ford Model A Tudor
SOLD - "BLKBRRD" - '78 Pontiac Trans Am
"BLUBYU" - '04 Coupe
 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)
____________________________________

Jim O.
Save the Wave...!!!
|wavey|

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



Jim Olson 

"The Toys"...!!!  Save the Wave!

Where I've been in a Corvette...!!!

in Forum: C3 Engines, Driveline and Handling


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