What is the biggest 18" tire you can run on the front with the car lowered? I have a friend that just put his OEM 225/40/18 on a 8.5 wheel and I think they are too narrow for that size wheel. I was looking at going to a 235/40 or a 245/40, 235's are only .3" taller and the 245's are .6 taller. Anybody got an opinion here? Also I'm in the market for a couple Michelin PS2's in the sizes above if anyone has a pair they are willing to part with. I'm not getting what I'm looking for out of my 255/35/19's so I think I'm just going to have them mounted back on my OEM's when my new wheels come in and just leave the 225/40/18's on the front OEM rims and get another pair, but bigger for the new wheels.

 

okay, maybe this will help.

when i changed my wheels to 20's, i got them at a width of 8.5. well the wheel dealer wanted to keep a stock width of 225. so they put on the 225 and everything was fine, except for the fact that the rim was hanging out. so i had them put on 235's. after that, when i turned to max rotation, there is a little rub in the fender wall. its not that bad, but it can be a little alarming. it only rubs when im getting out of my drive way or making a u-turn.

the wheel size has nothing to do with it, because the overall diameter of tire and wheel, is still exactly the same as stock.

 

Keep in mind that if you go to 235 or 245 width tires without lowering the profile you will probably begin rubbing/cutting into your tire with the upper ball joint bolt and nut.

If you lower your profile to 35, you should gain the extra space to clear the upper ball joint bolt and nut.

Compare for yourself... (Handy wheel / tire size comparer found here).

 

There's a lot of variables in your question... The OEM wheel, or your new wheels ? And how much have you lowered the car from OEM spec ? What's the offset of your new wheels ? These are very key to answering your question...

There are three clearance issues to deal with on the front wheels / tires (1) the upper "A" frame bolt that MMZ mentioned. This is the most critical because it can't be changed (cheaply) and if you mount a tire that is too wide on a small offset wheel, the bolt will slice through the inside shoulder of the tire before you drive out of the shop. But, this clearance will always remain constant +/- a few mm when the tire flexes and the wheel turns. (2) The inside fender well which has a knife edge and retaining bolts for the wheel well liners that protrude into the well. This is a variable because of how much you lowered the car and what the offset of your new wheels are. The compression of the front suspension during turning and braking will vary the distance between these. So if you're sitting nice and pretty in a parking lot and you have a few mm clearance, that clearance may not be enough when you're driving, especially driving hard. The fenders can be rolled by a good shop and you can trim the ends of the bolts that hold your well liners. but you won't really know what the suspensions compression is going to do unless you have a couple a fat guys sit on your fender while you turn the wheels back and forth.

So, that being said what's the offset of your new wheels ? How much have you dropped the car ?

 

The offset of the new wheels are 35mm and they are 8.5X18's. The front of the car lowered around 1-1/4" to 1-1/2". If I thinking right, if both wheels are the same offset, that would mean that the inside of the wheel would be 1.5" farther in than the 7" OEM. So with that being said, last night I took a mirror and a flashlight, stuck it in above the tire to see how much clearance there was between the tire and the top A frame bolt. There was only 1/4" to 1/2", I couldn't believe it was that close. I also got some tire height measurements together yesterday 225/40 = 25.1, 235/40 = 25.4, 245/40 = 25.7, of course these heights would be split in half from the rim to the outside of the tire and the width should be split between the inner and outer sides if the rim. I really don't want to go to a 35 series, but a 255/35 is 25" witch is basically the same as the 225/40 in height, I feel I would be safe to go with a 235/40, but I would rather go with a 245/40. I may end up having to go with some spacers, I did find some that have the hub centric rings made on the spacer itself. Thanks for the input HDDP.

Steve

 

Is your car lowered any from OEM height and is it an SRT6?

 

Yeah, that bolt was my main worry. I was using this calculator yesterday and scratching my head, the wheel are suppose to be delivered on the 10th. I still have to order lug bolts and possibly some spacers with hub centric rings, I figured I would wait till I get the wheels to see what kind of issues I'm going to run into. Like how long of a lug bolt I'm going to need, ball seat or conical, hub centric rings & or spacers.