Posts: 1131
Joined: 1/30/2008 From: Fort Smith, Arkansas Status: offline
I just recently purchased the Black American Racing Rogue wheels, which only come in 18.5(correct me if I'm wrong). I'm wanting to go staggered, 255/45 in front, 285/40 in back. From what I've read, 285's won't fit with the 18.5. Is this correct? If that's the case, I'll be forced to do 255/45 all the way around, which I didn't really want to do.
Nice looking wheel. I am still deciding what size tires to run on my setup. When I get my wheels, which should be today, I am going to bolt them up, then see how much clearence I have, then decide. I have a good idea what I am going to get, but that is a good way to double check. If you already have the wheels, you could try that method. My situation is completely different from most as I am in a custom setup, not a newer car that has all the fitment guides available. So this is the route I have to go. You may be able to get numbers that are available. 285\25.4=11.22inches. that is how wide the tire will be on the rim.
a 285 40 18 will go on an 18x8.5 wide wheel but due to potential safety concerns its not recommended. The reason is because the rim has a certain shape called the J channel, (on most rims sold in the U.S.) and the tires bead is also that same shape so that when you mount the tire on the wheel the bead of the tire sits properly into the channel of the wheel forming a tight seal. When you use an over or under sized tire on a rim the bead of the tire and the channel of the wheel do not mate up properly. Kinda of like putting a square peg in a round hole but not so extreme of a shape difference. So you get the oversized tire on the rim and it beads up and holds air and you slap it on the car thining its good to go. Then one day you are crusing and low and behold you get into a little street race through some twisty turns and before you even know what happen in the turn you just tried to take at 80mph, you tire blows out, puts you in a spin and next thing you know you are in the middle of a cow pasture upside down. Luckily you had your seatbelt on. You un hook it and climb out and look to see what caused the blow out but you dont see anything wrong with the rim or tire. Then you think back and say to yourself, hmm, i wonder if the stress of the load i put on the rim channel and tire bead was too much to handle and it gave way? well, your answer would be yes. So, to answer your question, sure you can put a 285 40 18 on an 18x8.5 wide wheel, but do you really want to risk your life for the coolness factor of having a 285 40 18 on the back of your stang. Probably not, thats why its not recommended. If you really want it bad enough spend a little more $$$ and get the rims widened. Sure its an extra expense but think about being the only kid on the block with the G.I. Joe with the kung foo grip. "PRICELESS" Hope this helps. Let us know if you have any other questions. I am pretty sure we have the Nittos in stock. However let me make a more cost effective suggestion. The Riken Raptor Z. It a Michelin made tire sold under the Riken name, just like Ford Lincoln Mercury and they are quite a bit less expensive than the Nittos and have better specs. Both have a 300 treadware, both have an A temp. rating but the Riken has an AA traction rating where as the Nitto only has an A traction rating.
Posts: 3426
Joined: 5/21/2005 From: S.burbs Chicago Status: offline
J channel? New one for me. Nothing in the rims structure keeps the bead against the flange. The structure in the tire, and psi are what keep it sealed against the rim. But either way, results would be the same for that well written story, lol.
Keep in mind, you cannot compare tread wear ratings to different manufacturers.
i beg to differ stoenr. the j channel is the shape of the rim flange that the tire bead seats against. back before they were standardized in the U.S. different rim manufacturers used different shapes of rim flanges. Thats why you see on the back side of rims where the size is stamped many of them say 17x8J, J refering to the rim flange style. Very simliar to the way hammer on weights are different shapes depending on the shape of the rim flange on the front of the wheel. you are correct in stating that the PSI keeps it seated but there is a much higher risk of it coming unseated if the bead seat and the rim flange and not flat against one another and the shape of the rim flange being the same shape as the tire bead is what keeps it that way. Imagine if the tire bead was pointed and not the shape that it is, it would never hold air. there are 7 different rim flange styles that i know of, J, JJ, K, JK, B, P, and D. each one of them a different shape. You may not be aware of it since it standardized now but its certainly exists. take a look at this link. A lot of good info. there. You'd be surprised at what all new info. you will find. I had no idea about some of this stuff for years but its true. A lot of it is mainly for European applications but its all good info. definitly makes for some good late night cant sleep, need to find something to bore me to sleep reading.
defininelty true about not comparing treadwares from different mfgs. i wish they would standardize that. what a pain trying to explain to a customer that yes there are numbers, and yes they are govt. mandated but they really dont mean a damn thing.
Printable Version
What's the best/largest tire size for a 18x8.5 rim? - 
