Max rim backspace with no mods?
Thread Starter
The ORIGINAL and bestest
Joined: Oct 2000
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From: Toronto Ontario
Toronto Events Coordinator
Max rim backspace with no mods?
I am thinking about getting new rims; I currently run 17" x 8" Torq Thrust II's with 4" backspacing and 255/50/17 tires. I don't have fender flares, so with a wider rim, the extra width has to go in. How far in can I go before hitting either the frame or suspension?
TIA
TIA
Burning Brakes
Joined: May 2007
Posts: 1,042
Likes: 1
From: Greensboro NC
First thing? You would pretty much need to go with 18's.
18x9.5 with a 5.031 back spacing and 275/40-18's is all that my 69 could stand (Boss 338's). And that was with me moving the parking brake cable to the top of the trailing arm.
5.5" backspacing would never have worked.
Also, on mine, a 285/40-18 tire would most likely have been too close to the trailing arm, as the 275's only have about 3/8" clearance as is.
Not a lot of room under there...
18x9.5 with a 5.031 back spacing and 275/40-18's is all that my 69 could stand (Boss 338's). And that was with me moving the parking brake cable to the top of the trailing arm.
5.5" backspacing would never have worked.
Also, on mine, a 285/40-18 tire would most likely have been too close to the trailing arm, as the 275's only have about 3/8" clearance as is.
Not a lot of room under there...
Team Owner
Joined: Apr 1999
Posts: 21,953
Likes: 1,445
From: Reno Nevada
2024 C3 of the Year Finalist- Modified
4 inch front BS is max because you get tire rub at lock to lock with 255/50/17 The 255/45/17 work better because of less dia. I have both 9 and 10 inch front 17 wheels. 9 inch is a good rim width for 255 tires and the 10 inch I use 275 kumhos for street and 295 slicks for track days.
Thread Starter
The ORIGINAL and bestest
Joined: Oct 2000
Posts: 10,009
Likes: 240
From: Toronto Ontario
Toronto Events Coordinator
First thing? You would pretty much need to go with 18's.
18x9.5 with a 5.031 back spacing and 275/40-18's is all that my 69 could stand (Boss 338's). And that was with me moving the parking brake cable to the top of the trailing arm.
5.5" backspacing would never have worked.
Also, on mine, a 285/40-18 tire would most likely have been too close to the trailing arm, as the 275's only have about 3/8" clearance as is.
Not a lot of room under there...
18x9.5 with a 5.031 back spacing and 275/40-18's is all that my 69 could stand (Boss 338's). And that was with me moving the parking brake cable to the top of the trailing arm.
5.5" backspacing would never have worked.
Also, on mine, a 285/40-18 tire would most likely have been too close to the trailing arm, as the 275's only have about 3/8" clearance as is.
Not a lot of room under there...
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
The 5.5 backspace fits just fine. I did move the parking brake bracket. The 18 inch wheel you really do not need a shorter spring because it goes inside the wheel. The sway bar will definitly not fit. Although someone here did modifly the sway bar to fit. I run a dual mount spring so it was not needed.
Thread Starter
The ORIGINAL and bestest
Joined: Oct 2000
Posts: 10,009
Likes: 240
From: Toronto Ontario
Toronto Events Coordinator
The 5.5 backspace fits just fine. I did move the parking brake bracket. The 18 inch wheel you really do not need a shorter spring because it goes inside the wheel. The sway bar will definitly not fit. Although someone here did modifly the sway bar to fit. I run a dual mount spring so it was not needed.
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Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Oh yea, let me find them.
Took a while but this shows the clearance. I had the trailing arm out at the time but it is bolted up exactly the way it is on the car. Like I said it is tight but in 4 years of hard driving and many an autoX run it has never rubbed.
Here is the original setup about 4 years ago. This was with a mono spring that was reduced 1/2 inch both sides. The new spring is about the same just a dual mount spring.
This is a little later version with the dual mount spring. It has changed a little but the spring is the same.
Last edited by Gordonm; Sep 8, 2010 at 10:12 PM.
Burning Brakes
Joined: May 2007
Posts: 1,042
Likes: 1
From: Greensboro NC
