Max tire size - 68 dart

SRT_DSTR15 said:

I wish I could fit 275 all the way around like on a duster

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You can, you just need a 1/2" spring offset.

MuuMuu101 said:

Yeah, I want more grip than these 255's can handle. Lol.

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If you're still running michelin super sports that's a 300 treadwear tire, you could keep the 255 size and go down to a 200 treadwear tire like a set of falken azenis rt615's or bridgestone potenza re-71r's. That would add some grip.

72bluNblu said:

You can, you just need a 1/2" spring offset.



If you're still running michelin super sports that's a 300 treadwear tire, you could keep the 255 size and go down to a 200 treadwear tire like a set of falken azenis rt615's or bridgestone potenza re-71r's. That would add some grip.

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I can run 275 on 18s up front on a 69 dart?

SRT_DSTR15 said:

I can run 275 on 18s up front on a 69 dart?

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Don't see why not. The front fender clearance isn't any different than other model year Darts unless maybe you consider the trim studs that MuuMuu is having issues with. That's what I have on my Duster now and it has '71 Dart fenders. You need an 18" rim to clear the tie rods, for a 275/35/18 you need an 18x9" with about 6" to 6.2" of backspace (25 to 27mm offset) assuming you've got 73+ BBP disks. Most likely tubular UCA's as well to clear that deep of a backspace at full steering lock and suspension extension.

72bluNblu said:

Don't see why not. The front fender clearance isn't any different than other model year Darts unless maybe you consider the trim studs that MuuMuu is having issues with. That's what I have on my Duster now and it has '71 Dart fenders. You need an 18" rim to clear the tie rods, for a 275/35/18 you need an 18x9" with about 6" to 6.2" of backspace (25 to 27mm offset) assuming you've got 73+ BBP disks. Most likely tubular UCA's as well to clear that deep of a backspace at full steering lock and suspension extension.

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Shoot was hoping to stay stock uppers and lowers hmmm. Good to know. I'll stay 255 then go 275 later

72bluNblu said:

If you're still running michelin super sports that's a 300 treadwear tire, you could keep the 255 size and go down to a 200 treadwear tire like a set of falken azenis rt615's or bridgestone potenza re-71r's. That would add some grip.

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I'm still running the Michelin SS's. They're a decent tires, great on the road, but have their limitations on the autocross and road course (especially with 500+ hp). Once I lock down the fix for the tire rub issue, I'd like to switch tires. I'm thinking about offset shackles soon and if that's the case, I may even get new wheels so I have the same offset front and back so I can actually rotate tires. After this year, it's been pretty evident that I don't drive my car as much as I was projecting too during the build, so going down to a 200TW tire would also be in the cards with a 275/35/18.

SRT_DSTR15 said:

Shoot was hoping to stay stock uppers and lowers hmmm. Good to know. I'll stay 255 then go 275 later

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Stock lowers aren't a problem. The UCA's will be rim dependent. I know that on my Duster the 18x9's I have just touched the stock UCA and full steering lock and suspension extension. But there's a couple things going on there. Rim design will play a factor, and so will the size of the steering stops on the lower ball joints. After comparing a few it's pretty clear the tolerances aren't super tight on the steering stops, so, a smaller steering stop will mean more steering range to lock and less room for the rim. And alignment of course is in there too. I tested mine before I added the 3mm spacers to keep my tires from rubbing my frame at full lock.

So what I'm saying is that you have to check that clearance, but depending on your set up tubular UCA's might not be absolutely necessary. And there's always your comfort level too, the odds of you having the suspension fully unloaded while at full steering lock while actually driving are pretty darn small.

MuuMuu101 said:

I'm still running the Michelin SS's. They're a decent tires, great on the road, but have their limitations on the autocross and road course (especially with 500+ hp). Once I lock down the fix for the tire rub issue, I'd like to switch tires. I'm thinking about offset shackles soon and if that's the case, I may even get new wheels so I have the same offset front and back so I can actually rotate tires. After this year, it's been pretty evident that I don't drive my car as much as I was projecting too during the build, so going down to a 200TW tire would also be in the cards with a 275/35/18.

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And there's a few more options for tires in 275/35/18 too. I know on my car I'm pretty close to having the same offset front and rear, but the B-body rear axle, body style, and brake choices play a role there. My rims are actually a +35 in the front and a +38 in the rear, and I'd be better off with a +35 in the rear. The 13" brakes and a 3mm spacer make my front offset 27mm effectively if you compare to a stock 73+ disk set up. It's certainly doable with the right combination especially if you're willing to consider a small spacer to make up any difference.

72bluNblu said:

And there's a few more options for tires in 275/35/18 too. I know on my car I'm pretty close to having the same offset front and rear, but the B-body rear axle, body style, and brake choices play a role there. My rims are actually a +35 in the front and a +38 in the rear, and I'd be better off with a +35 in the rear. The 13" brakes and a 3mm spacer make my front offset 27mm effectively if you compare to a stock 73+ disk set up. It's certainly doable with the right combination especially if you're willing to consider a small spacer to make up any difference.

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I think I have a plan, it's just when to pull the trigger. I want a couple hard runs, possibly through the local hills, to feel out the fronts and rears to see if they're still rubbing after it's bfh treatment. But if I pawn off my MP shackles and buy the Dr Diff shackle, I'll have offset shackles that will accept the aftermarket leaf springs and retain my 1" drop. Not only that, but it will center my 8 3/4 as mine favors the passenger side about 0.25". I was going to also borrow a buddies helper springs he had on his '72 Charger to help reduce compression. On the fronts, while it would be in the shop, I was thinking about upgrading torsion bars to something thicker than the 1.06" bars I have right now.

At that point, I could just remove my rear +5mm spacers and run the car as is. The only problem is I wouldn't really pass tech at any racing events as the front tires are cut up and the rear tires had their sidewalls rubbed away. But I could run the tires as is on the streets and just have fun.

Luckily, when I go to the tire upgrade, I don't think I'll be paying a pretty penny in wheels. I found out Summit still offers the offset I have up front. So, I could just buy 2 wheels for less than $400 and I have all 4 corners matching. The only thing I'm worried about is the section width. The Michelin's on an 18 x 9" are 10.2" wide. The Bridgestone RE-71R's are 10.9" on an 18 x 9.5" wheel. So, I'm hoping by having a wheel that's .5" shorter it would bring the section width down to about 10.6-7". Looking at RimsnTires.com, with my +5mm spacer on the back, I'll be the exact same distance to the fender as I am now and I think I'll be able to clear the springs. The loss in 0.4" in tire height may help me.

On fitting 275 tires and useing inboard shackles are the leaf springs stock? Or are you running the super stock springs? They may give that extra room needed as they lift the rear of car up a bit.