I have an '06 GT auto and am thinking about purchasing a set of 18x10's for the rear and 18x9's for the front (deep dish bullitts from Mustang Tuning). As for tires, I'm looking at a set of Nitto NT555's - 295/45ZR-18 for the rear, and 255/45ZR-18 for the front. I know the overall diameter will be larger than stock, so I thought I should ask here and make sure I won't have any problems with rubbing, etc. before I make the purchase. I perfer the old school look of the taller sidewalls, thus my slightly taller tire selection. I do have 3.73 gears, and I know I can adjust the revs/mile with my tuner to get the speedo to read correctly with the larger diameter tires. My suspension is stock, and I have no future plans to change it at all. I'm just looking for some confirmation that these wheels/tires will work ok on my GT before I plunk down the cash.

 

285/40's might be a better fit. I have seen some posts here were 295's have been used with success but do the recall what AR or wheel diameter ... usually 19's or 20's though. A lot will depend on the wheel offset.

 

i ran 305/35/18 nitto drag radals on the rear of my '05 with no fitment issues.

 

Throwing 255/45ZR18 upfront and 295/45ZR18 is not a good idea as these will have different overall diameters.

in any case, 255/45ZR18 is the just about as wide as you can go upfront before you should start worrying about your steering angle.

that in mind, following is a list of sizes and their overall diameter:
235/50ZR18 = 27.25" dia
255/45ZR18 = 27.04" dia
285/40ZR18 = 26.98" dia
295/40ZR18 = 27.29" dia

so your best bet is 255/45ZR18 upfront and 285/40ZR18 out back

 

I know the front and back will have different overall diameters, but I'm not sure I understand how that causes an issue? (I don't mean to sound like I'm arguing, just trying to learn.)

 

The rule of thumb states you don't want a difference of more than 3% in tire diameter. To run a 295/45/18 rear tire you would need to run a 255/50/18 or a 275/45/18 on the front. Both tires will then measure approx 28 inchs in diameter.

Since you stated you like the larger side wall, I'd go with a 275/40/18 on the front and a 285/40/18 in the rear. This way both tires will be close to the stock 27 inch diameter and you will have more tires to choose from.

Jim

 

In some applications a dramatic differance can upset the abs under hard brakeing.

I have never heard of the s 197 cars developing abs issues with different tire sizes. Anyone??

If you want the car to corner you should run the same size ft and rear, it helps the balance.

As a side note you cant rotate different size tires, so you will need to buy tires more often.

I run 275/40/18's on 9.5 inch rims

jay

 

well for one, your ride wont sit flat anymore

 

I have that exact same combo w/ nitto 555's and it looks very nice and handles well also.

rotation is out of the question but eh... who cares, I want the most meat available and an agressive stance as well.

 

I'm planning on 275/40/18s on all four. 18x9" wheels.

 

Thanks for your input everyone! I'm not concerned about being able to rotate the tires - when they wear out, I'll buy new ones. Mostly I just wanted to be sure that I wouldn't have any problems with rubbing in the wheel wells. I hadn't thought about having problems with the ABS, but if others aren't seeing problems, I'm not too concerned. I'm encouraged to see that 06GTwJUICE is using this combo with no problems, and I also think MTAS was/is using the same size tires on his car. I feel good enough at this point to go ahead and order the while and tires. I guess if I do run into problems I'll just have to replace the 295/45's with 285/40's - but it's worth it to me to try and get it the way I really want it.

 

how wide tires can be fit on stock 18x8.5 wheels? anyone running wider than 255? exact dimensions and brand??

 

i believe 255 is just about as wide as you can go safely on 8.5" wide rims, before you compromise the sidewall integrity and risk having the tire pop off the rim in some circumstances

 

I've come up with another question ... well 2 actually ...

I've seen a few people mention needing an adjustable panhard bar when putting wider tires on the rear. I can understand that if the rear suspension is changed (new springs) that you would need an adjustable panhard bar, but I don't understand why you need to adjust the panhard bar if only the wheel diameter is changing. Changing only the wheel diameter shouldn't change the relationship (position) of the rear axle with respect to the body. So if I'm only changing the wheel diameter, do I really need and adjustable panhard bar?

Here's the 2nd question ... Do I need spacers with the Mustang Tuning deep dish bullitts (18x10 and 18x9)? I thought I'd seen a message while searching through the forums that someone put on quarter inch spacers to keep the wheel from hitting the break caliper (I'm guessing the front). But if the wheels are made for the 05+ ... wouldn't they make them so you don't need a spacer?

 

To address your 2nd question, you will probably need a spacer for the front. I polished my calipers on the front whhels and didn't need the spacers anymore. Of course, then I bought the tri-bar center caps and had to put them back on because the rubber cap at the end of the wheel was pushing the center cap off. Frustrating but oh well.

The wheels themselves are very nice. The place that mounted the tires and balanced them said they were the best balanced aftermarket wheels he'd ever seen FWIW. The look is just awesome. Good luck.

 

Dude - talk to MTAS

He has the 255/45 and 295/45 Nitto setup on his ride with the Eibach prokit and his Stang has one of the best stances I have seen.

Check it:

 

Well there's a rule that's meant to be broken. I say put the big meats in the back!!

 

I dont think these days the "% diff" means much. Back when suspensions were crap and cars handles like they were accidents waiting to happen, yes it probably made a big difference.

Go for it.

a lot of us have that combo and have suffered no ill affects.

 

Could you explain what you mean when you say you polished your calipers and didn't need spacers anymore?

I have the DD 18X9 bullitts from AM and I haven't put them on yet, I don't want any unexpected problems with needing spacers.

Also hey Burke0011, you have these wheels- do you have spacers?

thanks,

tom

 

I'll give it a crack

No. 1) considering manufacturing tolerance stack up (lowered or stock ride height), its very likely the rear axle housing is offset to one side or the other. If you run wide tires on the rear, with an adjustable panhard bar you can split the difference.

No. 2) When those wide lip 9" Bullits first came out, they made a mistake in the casting design and were selling the 9" for the fronts with a 1/4" inch spacer to make enough clearance for the caliper. Someone mentioned they have retooled and now maybe that is no longer a problem. But that claim needs to be verified.

As for the tire height difference, I have never heard of a 3% rule. I can imagine though that the ABS will be confused by the RPM difference front to rear, but there may be some bandwidth in the programing that will tolerate a certian amount of differential error before it tries to correct for it. A non ABS car would not care as long as the brake proportining front to rear was compensated for.