Time for new wheels and tires

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It's not really that there's necessarily a big handling difference between having 14" and 15" wheels up front, it's the tire selection. There are very few tire sizes, and very few brand and compound options for 14" rims. Selection for 15" rims is still better, although the tire selection for 15" rims is pretty limited too nowadays. Pretty much down to whether or not your want to run BFG T/A's or Cooper Cobra's. Both are all season tires with a pretty hard rubber compound, and are pretty mediocre compared to modern tire performance standards. But unless you're willing to go to 17" or 18" rims they're about the best you'll do for a street tire, and they have the "classic look" with blackwalls and white lettering.

In the front with 73+ disks you should be able to run up to a 225/60/15 on a 15x7" rim with a 4.25" backspace without any trouble. You might have to make a slight adjustment to the lower front fender to bumper brace depending on your ride height. With manual steering that still shouldn't be too difficult to manage, especially if you have the standard 24:1 manual ratio. Even the fast ratio 16:1 shouldn't be an issue with 225's and the typical caster you can run up front with the stock suspension, and the car should feel much better planted in the front. More importantly you'll have better stopping power with more traction up front, and the front end will be less likely to understeer or "plow" with a rapid steering input than it would be with the 4" skinnies you've got up front now.

In the back you haven't mentioned yet what rear axle you have, it makes a difference. Factory A-body axles are not all the same width, the BBP 7.25" and 8.25" rear axles are 56 3/4" wide at the wheel mounting surface (also sometimes called drum to drum). 8 3/4" axles are 57 1/8" if they're still SBP, if they've been upgraded to BBP axles they're more like 57 13/16". Which makes a difference in the amount of backspace you'll need, especially if you run wider tires.

Measuring your car in the back is fairly simple, all you need is a tape measure and some kind of straight edge. A carpenter's square if you have one large enough works as well. Put the straight edge across the wheel mounting surface (the face of the drum at the studs, not on the center register) and then measure back the spring. Repeat and measure out to the quarter lip. You'll have to rearrange the straight edge in between as you want to keep the tape perpendicular to the spring and then the quarter for an accurate measurement. On a Demon with the stock spring locations and uncut quarters you should end up with about 12" from spring to quarter lip. How that's split will depend on the axle width, but with the right backspace fitting a 275/60/15 is usually no problem at all. For reference, a 275/60/15 is 11" wide at the section width. Which means, properly centered in the wheel well, there should be a 1/2" to the springs and a 1/2" to the uncut quarter, which is more than enough even on a car that has been lowered from stock. A 255/60/15 is a piece of cake, leaving ample clearance everywhere assuming you run the right backspace.

If you happen to have an A-body 8 3/4 with BBP axles, the typical set up is a 15x8 with 4.5" of backspace, which typically works well with a 275/60/15. That axle should give a WMS to spring distance of ~6", which also means the WMS to quarter should be ~6". Tire is 11" wide, so 1" of tire hangs over the edge of the rim. Backspace is 4.5", so add 1", you get 5.5" of wheel which gives you a 1/2" clearance. Front space on the wheel is also 4.5", so you guessed it, 1/2" clearance on the quarters.

Here's a post I wrote awhile back, in response to TF360, showing 12 different members' cars, with pictures of their cars and links to their threads, showing how they run 275's on uncut and unmodified Demons/Dusters/Dart Sports. I didn't even include my own car in that list, it fit 275's just fine when it was stock. I know there's more, but I only listed examples that specifically mentioned being unmodified.

Demon Rear Wheels



Funny, that's the same exact thing you'll be saying if you get caught out in the rain with those replica PolyGlas tires.

They do look pretty though.

That’s awesome, thank you for taking the time to write that out and explain that a little more to me as I need all the guidance I can get from knowledgeable members who have the know how. As for the rear end it’s an 8 3/4 with the 5x4.5 BBP.
Side bar, I called Mickey Thompson tech support directly and they said fear not, you can drive the car on the street just fine with the wheels and tires that are currently on there. So now I know I can at least enjoy the car for a few weeks while I get a new set of wheels and tires all worked out for it
 
A couple things after reading 72nblu's post, which is phenomenal info.

Always error on the side of too much back spacing you can always use spacers. You can't add backspacing.

A 1/2 inch to springs is tight, but ok. Mine have scrubbed there a little. But a 1/2 on both sides is tight. In my opinion when ordering wheels and tires, too tight. you should also know that the inner fender flare inboard above the lip.

take your ride final ride height into consideration when taking your measurements.
 
Sorry to revive an old thread, just wanted to leave an update. I ended up getting wheel vintique rallyes with cooper cobras, 215/65/15 up front and 275/60/15 in the rear and they fit great. Thanks again all
 
shoot, my wife nags when I do the dishes, too much water, too much soap, not enough rinsing, not enough soap. I swear they pull them aside in healthclass and teach them how to torture their future husbands

I`d tell her , ''if she doesn`t like it , do it ur self''> like I`M DOING DISHES , YEAH RIGHT !
 
A couple things after reading 72nblu's post, which is phenomenal info.

Always error on the side of too much back spacing you can always use spacers. You can't add backspacing.

A 1/2 inch to springs is tight, but ok. Mine have scrubbed there a little. But a 1/2 on both sides is tight. In my opinion when ordering wheels and tires, too tight. you should also know that the inner fender flare inboard above the lip.

take your ride final ride height into consideration when taking your measurements.

15'' tire selection is still pretty good around here ------------
 
Sorry to revive an old thread, just wanted to leave an update. I ended up getting wheel vintique rallyes with cooper cobras, 215/65/15 up front and 275/60/15 in the rear and they fit great. Thanks again all
Pics or it didn’t happen! :mob:
 
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