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Discussion Starter #1
Anybody have pictures of a 26x10.5x15 tire fitting on a 99-04 that's lowered on H&R SS lowering springs without isolators? I have a set of Weld RT-S71 15" wheels that I'd like to slap a bias ply on for use at the track and am wondering what fitment is like.
 

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I run 26x11.5x15 slicks without any issues whatsoever. I'm on the stock springs with a coil and a half cut off with isolators still installed. My quad shocks are gone as well.

 

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I did some measuring on my car and compared to an online tire size comparison tool. My car sitting on the ground with a 17x10 wheel and 315/35/17's measures a tire height of about 24.7" tall from the ground. With those wheels and tires mounted on the car, the rear fender is right at 26" from the ground, maybe just a tad above at like 26 1/16".... The tire size comparison tool online says that my 315/35/17's should be 25.7" tall (they're not... it's an inch less) and says that a 26x10.5x15 is 26" tall (just like it should be)... According to MT's website, their ET Street R would be 26.3". I don't know whether to believe there will be a 1/4" difference, 1/2" difference or more than an inch difference at this point. All I know is that I currently have about 1.3" of room before I'm on the fender.

I also got to thinking that the centers of the 2 different wheels and tires should be different in height. Whatever the difference between the 2 tires while they're NOT mounted should be half that difference when they ARE mounted, right?? I think I should be fine to clear the fender without the isolators, but I would think I can always throw some in if it doesn't fit and for sure be okay. At any rate, I suppose I'll be doing a test fit in the near future and doing some more measuring while the wheel is on. Then, I'll just be figuring out if I want a 10.5" or 11.5" wide tire on my 15x10 weld wheels. Input on what width to go with is welcome. 7.5" backspacing.

In the meantime, if anybody has some more pictures, please post them with details on your lowering springs, if you have isolators or not, and your wheel/tire combo. Thanks!

---------- Post added at 07:18 PM ---------- Previous post was at 07:16 PM ----------

I run 26x11.5x15 slicks without any issues whatsoever. I'm on the stock springs with a coil and a half cut off with isolators still installed. My quad shocks are gone as well.

Did you get rid of the quad shocks due to clearance issues or just to get rid of them? Thanks.
 

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Did you get rid of the quad shocks due to clearance issues or just to get rid of them? Thanks.
Upper and lower control arms have been upgraded for a while so the quad shocks were removed to save weight. Never tried the bigger tire with them on. I've heard of people flipping them to get more clearance if needed.

If you have aftermarket LCA's, you shouldn't need them any longer.
 

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Discussion Starter #5
Upper and lower control arms have been upgraded for a while so the quad shocks were removed to save weight. Never tried the bigger tire with them on. I've heard of people flipping them to get more clearance if needed.

If you have aftermarket LCA's, you shouldn't need them any longer.
I gotchya. I have Team Z adjustable upper/lower control arms, I just never bothered to take the quad shocks out. It's funny because my car is setup with awesome parts to launch but I'm over here with a slammed stance and worthless tires haha ... My stock rear gears don't help either, but building my rear end and 3.73's is next on the list.

I've also installed MM FLSFC's and welded in torque box reinforcements. This car should be ready for some serious 60' times - I hope. Until then, I'm sitting here with 2.1 60' times lol
 

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I did some measuring on my car and compared to an online tire size comparison tool. My car sitting on the ground with a 17x10 wheel and 315/35/17's measures a tire height of about 24.7" tall from the ground. With those wheels and tires mounted on the car, the rear fender is right at 26" from the ground, maybe just a tad above at like 26 1/16".... The tire size comparison tool online says that my 315/35/17's should be 25.7" tall (they're not... it's an inch less) and says that a 26x10.5x15 is 26" tall (just like it should be)... According to MT's website, their ET Street R would be 26.3". I don't know whether to believe there will be a 1/4" difference, 1/2" difference or more than an inch difference at this point. All I know is that I currently have about 1.3" of room before I'm on the fender.
The stock 245/45-17 has a 110.25 mm sidewall. That is tire width times the aspect ratio (245 x .45). A 275/40-17 has a 110 mm sidewall. A 315/35-17 has a 110.25 mm sidewall. The only difference is the width. A 110 mm sidewall is 4.34" tall (110/25.4). Two sidewalls and the 17" wheel make the tire 25.68" tall. (8.68" + 17") They are all the same except for the width. A tire on the ground with the weight of the car on it has a flat spot on the bottom. That is why ground up measurements are a little less. How much less depends upon the tire's air pressure.

I run 245s on an 8" wheel, 275s on a 9" wheel, and 315s on a 10.5" wheel. I have run 245s on a 9" wheel and didn't like it. They look very stretched and provide absolute no curb rash protection. In the winter I run ultra high performance all seasons all the way around. In the summer I run drag radials on the back. I can run 32 psi in the 245s and 275s and get decent tire wear by rotating them. I cannot run 32 psi in the 315s. There is not enough weight on the back to fit the tire flat on the pavement. 32 psi wears the centers out. I run 20-22 psi in the 315s so that I can get mostly even tire wear.
 

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Discussion Starter #7
Thanks Eagle. Your input is always good. I knew they were the same height as a factory size tire. I was also thinking the same thing about the weight of the car bringing the height down, I just didn’t think it’d be a whole inch! I have my rear street tires at 32psi.

I’m planning on trying on my skinnies in the front this weekend and will see what the rear wheels look like on the car without a tire. I’ll play with the tape measure from there and maybe capture a few pictures while I’m at it.
 

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Discussion Starter #8
Going from what I believe a 6.25” to 7.5” backspacing wheel is going to make things tight! Fingers crossed lol
 

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Discussion Starter #10
It’s super close. I am hoping to find somebody that will let me try on their rears before I go buy the rear tires.
 

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Discussion Starter #11
Had to just buy the tires and hope they fit. I can bring the car up (if I have to) by adding isolators. Otherwise, it’s just the exhaust I am afraid of rubbing but we will see. These pictures are of the wheel and tire just sitting next to the car. When it’s mounted, it should look better.
 

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Discussion Starter #13
If it helps I have 295/50/15 on the rear with 5.5 backspace. No quads
Mine are more like a 275/50/15 (they are labeled as a 26x10.5x15). So mine are slightly smaller than yours. I don't remember what you have for suspension but I'm on H&R SS lowering springs with no isolators - pretty much the lowest you can get these cars with an unmodified manufactured spring. If you wanted to be lower, you would have to run cut springs or coilovers.

I've learned recently that I'm most concerned about the backspacing. My wheels have a 7.5" backspace! That snugs 'em right up inside the wheel well. I should have no problem getting it to clear the stuff I can't move though based on my previous pictures. It's the exhaust that starts to get in the way it looks like. I think (I hope) I'm going to get away with it, especially since I stretched the tire over a 10" wide wheel (an 8" wheel is recommended for this tire). I believe that will bring the tire height down a bit and keep the tires from bulging/overhanging the outside/inside of the wheels. The sidewalls sit almost perfectly flush with the sides of the wheel. I plan to mount them up soon and take a bunch more pictures now that I have the tires mounted on the wheels. Hopefully this post can help people in the future since I couldn't find a lot of help on the internet with the lowering springs I have.
 

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I have Team Z 99-04 drag springs and J&M weight jacker lower control arms that are almost bottomed out to get the angle I needed for the instant center to be where it theoretically should be. Sorry Mine are 6.5 backspace. My exhaust is dumped so I have no help to give there.
 

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Discussion Starter #15
Here are some pictures of the tires mounted on the wheel. They are stretched past Mickey Thompson’s recommendation. I think they fit just fine and should give the tire a little better stability.
 

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Discussion Starter #16
I have Team Z 99-04 drag springs and J&M weight jacker lower control arms that are almost bottomed out to get the angle I needed for the instant center to be where it theoretically should be. Sorry Mine are 6.5 backspace. My exhaust is dumped so I have no help to give there.
Yeah, 6.5" backspace seems to be the norm for 99-04 cars. That makes me feel a little better that there's only an inch difference in our backspacing. Your wider tires probably make up some of that 1" difference in our backspacing. Fingers crossed they bolt on and I don't have to do ****!

Well.... except rebuild my rear end that is currently f'ed. HAHA
 

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I believe the backspacing on my 17x10.5s is 6.81. That is the backspacing on similar wheels. They fit but I have stock springs and I've taken off my quad shocks.
 
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Discussion Starter #18 (Edited)
Barely fits without touching the exhaust. Since it’s tucked in so far, I’ll never have to worry about the tire touching the fender. It almost looks minitubbed by how far inside the wheel sits. Not much space between the ebrake cable and the rim. Might bend the tab holding it over a bit or something. I’m glad I didn’t get a wider tire for these wheels. Maybe I’ll get a different set of wheels down the road that have 6.5” backspacing or just run a spacer to run a wider tire - if it’s even needed.
 

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