Tires on 71-72 Roadrunner

Technical Question and Answer - On topic to 71-74 Plymouth B-bodies only.

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72bluNblu
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My Cars: 1971 383 SSP

Re: Tires on 71-72 Roadrunner

Post by 72bluNblu » Fri Mar 07, 2014 9:21 pm

So I finally got the chance to mount up the wheels from my Challenger onto my '71 SSP. The rims are 17x9" with a 5" backspace, and have 275/40/17's on them. Based on what I saw, which was a TON of space pretty much everywhere, I think that if you wanted you could easily run 295's on all 4 corners of a stock 71/72 Satellite.

In the front, I checked the wheels at full lock. The clearance to the frame in the rear at full lock was almost 1", which is pretty decent. At full lock in the other direction there wasn't anything even close to being in the way, so I didn't even take a picture. At the fender, I had nearly 2" to the tire. On my Challenger that's the tightest spot, I only have 3/4" there, and nothing rubs. My SSP is also VERY low in the front, it literally sits on the bumpstops. They aren't fully compressed, but you wouldn't be able to go much lower, maybe only a 1/2". So, these shots are very close to showing the clearance with the suspension fully compressed. Basically, there's a ton of room left to the fender, and a little to the frame.

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In the back, with the 8.25" rear I have just under 1" to the quarters (the angle of the pic is a little deceiving) and about 1 3/8" to the springs.

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So, the conclusion I came to is that in the front, ideally you'd want an 18x10 with about 5" to 5.5" of backspace. At 5.5" you might need a small spacer to keep it off the frame in the back at full lock with a 295, anything narrower would be fine. The REALLY good news here is for all the drop spindle and 17" wheel users out there, because you can run a 17x10, or drop spindles, and 5 to 5.25" of backspace and still run a 295 because the "extra" room is to the fender. I think with a 17x10 or drop spindles 5.5" of backspace would probably hit the outer tie rod, but there was more than a 1/4" of clearance to the tie rod with the 275s and 17x9's.

In the back, a 10" wide rim with 5.5" to 6" of backspace would be about ideal with a 295. 6" would be better, because that would allow you to use a small spacer if things were too close the springs. 5.5" of backspace will leave the wheel pretty much at the max for clearance on the quarter.

If you wanted to go square, say, 17x10 or 18x10 all the way around, 5.5" of backspace would probably be the way to go (0 offset). You could use a small spacer in the front if needed, and in the back you should be fine, maybe a slight roll on the quarter lip if your car sits low.
'71 SSP GA4
'71 DartGT EL5 (#65 in the GT registry)
'71 DartGT GK6 ( #69 in the GT registry)
'74 Duster/71 demon tribute- primary driver
'72 Challenger-secondary driver

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dangina
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Re: Tires on 71-72 Roadrunner

Post by dangina » Fri Mar 07, 2014 11:02 pm

this is awesome news! this thread should be a stickied!

just to clarify when you say we can run 295's, is that 295/50/40/60?

Based on your calculations, With my hub being 3/4" longer looking at your pic with the extension tape to the front fender , If I put the same rim on right now I'd still have 1 1/4" to the fender lip, be 1 3/4" away from the frame at full one lock, and at the other lock there's so much room that its not worth mentioning. And to hit the tie rod I would need a 17x10 with 6.25" before I'd be hitting the tie rod. This is very good news as I have been looking at aftermarket rims and all the 17x10's are usually anything from +15 to +35mm offset. I'm looking at 17x10's with about +30mm or less offset on all 4 corners because I like the idea of rotating tires and if you get a flat, regardless of which tire, your spare will match...

Seems like with some clever spacing you could fit bigger rims in there :)

also I have been curious, in the front fenders you can see in your pic we have that metal brace that goes up over the tires, how close are we to hitting it? I thought about cutting it out...

I appreciate immensely the time it took for you to do this. :beer:
400 stroked to 470ci, 3:55 Eaton true trac, slightly upgraded suspension lol

BUILD THREAD!!!! http://www.protouringmopar.com/showthread.php?796-1971-Speedipus-Rex&highlight=speedipus

72bluNblu
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Posts: 39
Joined: Mon Jul 15, 2013 7:28 pm
My Cars: 1971 383 SSP

Re: Tires on 71-72 Roadrunner

Post by 72bluNblu » Sat Mar 08, 2014 12:23 am

I don't see the inner brace being a problem. It's curved, which provides good clearance for suspension travel. The E-body brace was flat, so it had to go. On the Satellite I don't see the brace being a problem unless you were all the way out at the very edge of the fender with the tire.

As far as the tire, it would be 295 with a profile to get it to about 26" tall. That would be a 295/40/17 for a 17 or a 295/35/18 for an 18. That's actually bad news, because what I haven't been able to find is a 295/40/17 tire. There's a few in race compounds, but nothing so far for the street. Closest for a 17 I could find is 285/40/17, there's a decent selection in that size.

295/35/18's are a available with a pretty decent selection.
'71 SSP GA4
'71 DartGT EL5 (#65 in the GT registry)
'71 DartGT GK6 ( #69 in the GT registry)
'74 Duster/71 demon tribute- primary driver
'72 Challenger-secondary driver

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dangina
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Re: Tires on 71-72 Roadrunner

Post by dangina » Sat Mar 08, 2014 11:22 pm

ok, again I really appreciate this :) now I can go wheel hunting. Its hard to find a set of aftermarket wheels that look good with something other than huge positive offsets. I hate HATE big chrome wheels on muscle cars, leave those for the hot rod guys
400 stroked to 470ci, 3:55 Eaton true trac, slightly upgraded suspension lol

BUILD THREAD!!!! http://www.protouringmopar.com/showthread.php?796-1971-Speedipus-Rex&highlight=speedipus

71Satellite98661
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Re: Tires on 71-72 Roadrunner

Post by 71Satellite98661 » Tue Mar 18, 2014 3:24 am

Seems like most of the conversation is regarding radial tires. If anyone is curious, I run G60-15 on all (4) wheels. The fronts rub slightly on the front frame rails at full lock. This is with 1.03" torsion bars and all new bushings, tie-rod ends, ball joints and idler arm. This is with a 440 and at stock height. Obviously there is still a ton of room to spare in the rear. I am curious as to what bias ply tires others run on theirs and what size. I wonder now if an F60 for the front would have been better at 1/2" narrower and 1/2" shorter.

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Eric
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Re: Tires on 71-72 Roadrunner

Post by Eric » Tue Mar 18, 2014 12:09 pm

71Satellite98661 wrote:Seems like most of the conversation is regarding radial tires. If anyone is curious, I run G60-15 on all (4) wheels. The fronts rub slightly on the front frame rails at full lock. This is with 1.03" torsion bars and all new bushings, tie-rod ends, ball joints and idler arm. This is with a 440 and at stock height. Obviously there is still a ton of room to spare in the rear. I am curious as to what bias ply tires others run on theirs and what size. I wonder now if an F60 for the front would have been better at 1/2" narrower and 1/2" shorter.
G60-15 was an optional tire size from the factory. The rubbing is likely an issue of the wheels being a different offset than factory.
AKA Butterscotch71....the road runner nest is out to win you over this year!Image

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