40x15.50 will fit into the fender arches, but expect some body changes if you decide to turn too far or cycle the suspension too much. 38x15.50 will probably have similar results.
A 38x13.50 might work with slight rubbing approaching full lock and/or the most extreme articulation, since some people report that with 37x13.50 too.
I'm in the "If it rubs at all in any situation, then it doesn't fit" camp.
I ran 37" 13.50 with a 6" lift no problem. But then I switched to a Toyo Open Country MT same measurement 37x13.50 and had to trim a small amount of plastic on my bumper. Couldn't really tell to much so I was ok with it. Well after paying for the tires I really had no choice but to be ok lol. Moral of the story some work some don't. But I really don't see a 38.5" working at all???
I put a set of 38x15.50's on mine with a 6.5" lift. It rubbed. But I only had to trim a little off of the back of the fender. Then I added a 2.5" leveling kit and it didn't rub anymore.
This doesn't work in all situations, due to the differences in tire manufacturer, and wheel offset....
.....but it is the closest to a perfect "rule" on tire fitment WITHOUT ANY OTHER MODIFICATIONS(IE, no trimming, no shimming, no cutting, no leveling kit, and no spacing).
Another exception to the rule is who's springs. Deaver moves the center pin foreward 1" on a 6" spring and 2" on a 8" spring. A lot of coompanys just leave it in the stock location. This will change how much tire will fit also.
Are you talking about the rear springs....if you are...I haven't seen too many issues with tire not fitting because of the rear...normally rubbing issues happen up front.
Thanks Tank, I'm so tempted to cut my fenders and put flares on them, your truck looks absolutely SICK !!!! I'm sooo tempted to do it and put 40's with my 6" lift...ostwhore:
Not trying to rain on your party but I would ask Tank about bumper cutting. I had to trim the plastic on the back of my bumper for 37's it wasn't very much. I have an offset of -19 don't remember what the backspacing was. But it was the most I could get with the BMF Novakanes. I notice that Tank has a aftermarket bumper that allows for a lot of clearence. Like I said not trying to bring any bad news but I would think with 40's and a 6" lift it you would need to trim more than just plastic on the bumper but I could be wrong, have been before. But on the good side I also like the look of any truck that has its fender welds filled with tire. Including the lowered trucks they look sharp like that.
I know...I read his truck description and looked at his pics...rebuilding engines, transmissions, electrical or suspension work is my game...I don't do body work and I'm petrified to cut my fenders....lol I even suck at spray painting...haha
Ask Tank a one handed blind monkey would have trouble screwing up the cut outs install. You are given generous tolerance to cut in. The main cutting is to the rear of the front wheel well on the fender. I wish they offered a rear that did not require cutting at all to match up with the front as up to 38-39 you do not need to cut for them to fit. Maybe a cutout meant for a different vehicle or year could be made to fit the rear. I will have to mod mine anyways as its an Excursion. Looking at 40x14.5x20 SS-M16s on 20x12 4.5" backspacing If I did not have to cut the back to fit the flares I would be willing to drop down to 38s but if I have to cut anyways I want to fill up that space and get the extra axle clearance. I have seen 37s and the cut outs seem to swallow them up.
What was the wheels backspacing. Where did it rub?
Has anyone ever had the fenders cut like that for cut outs but instead have the edges rolled back for a factory looking lip but with a larger wheel well opening? I saw a guy with that on Pirate 4x4 and it looked good.
I've seen a 06' F350 with a 6" lift and 40's with no fender flares....the lips looked factory rolled...it didn't look bad but I think it looks better with the fender flares...just gives it a wider stance look with the bigger tires...the guy said it cost him a pretty penny to have his wheel wells rolled, said that 3 body shops wouldn't even touch that project because apparently it's more involved that what it looks like.
With a stock bumper you absolutely have to cut it to make those big tires fit with low lifts and cut out flares.
Here is a pic of it. It really is not hard to do and you can get a black end cap to cover the cut edge and give it a nice clean look. Follow the curve of the cut out flares thru the bumper and it will give you nice lines. My avatar pic is 38x14.5 and you can see the fender cut.
I have another question....I've measured different size tires while on the vehicles and this is what I come up with...35" tire actually measures 34" from the ground to the top of the tire when mounted on the vehicle, 37" tire actually measures 35.5 and a 38" tire actually measures 36.25....these were all Toyo M/T tires....with that being said you would think that a 38" tire would fit fine where a 35" has plenty of room...just speculating...
Have you ever paid any attention to where the discrepancy arises from? If you measure the radii at 4 locations arround the tire (12,3,6, and 9 oclock) you will see that the the 6 oclock measurement is is lower than the the other 3 (which will all be equal). For tire fitment, the 3,9, 12 numbers are the important measurements. If you don't know how to convert radius from diameter, formula is as follows.
That's what I thought also, but for a 38" tire which measures 36.25 from the ground up ( these are new tires so tread depth isn't a factor ) to grow 1.75" is alot....as long as they shrink back down when trying turn into a parking lot it's all good...lol
I'm just worried about clearance when turning, I know you can stuff a big tire inside your fenders and drive straight, it's when you go to turn that the rubbing issues show up...
i fit 37 ss-m16s on a 4 inch superlift an i had to do some minor bumper an inner fender cutting to get them not to rub.. now all they do is rub on the springs at full lock.
I would also assume that the size of the rim would have a lot to do with tire growth and expansion as well, a 35" tire on a 16" rim would have way more flex than a 35" tire on a 20" rim due to the amount of rubber on the sidewall...but I could be wrong...I currently run Toyo M/T's 35x12.50 20's and can turn lock to lock with about 4 inches to spare before anything touches...I took the advice of a 4x4 shop when ordering my rims for back spacing purposes, according to them I can go as wide as 15.50 without any rubbing issues with these wheels...Measuring my wheels and tires now and doing some simple math it seems to me that a 38x15.50 will fit, but maybe I should stay on the safe side and go with 37x13.50...I know they will fit, but just trying to stuff as much meat under this beast as I can...
when figuring what size tire,...you also have to figure in tire deflection, centrifugal force, side flex, axle travel angle, etc, etc, etc, etc.
Just because it looks like it will fit sitting in a parking spot while cranking the wheel,...damn sure doesn't mean it will fit when you are taking a turn, while entering a shopping center that has a small bump at the entrance.
stick with 37's....and even then...you'll still probably have to trim a little and shim the bumper.
If you go with the 15.50 you need a 12" wide rim. The extra width of the tires changes clearances as do the rims with same backspacing. Some squeeze 15.50" onto 10" wide rims. ( which by the way is beow the tire manf recommendations for min rim width.) This tends to swell the tires outward. This can cause it to hit in areas if on a wider rim with the same backspacing it would not hit. Also narrow rims tend to make wider tires squirmy.
The rub points I found that went away with a wider rim were the hits on suspension i.e. leaf spring, radius arm at full lock out. Which backspacing staying the same it moves what would normally be bulging past the side of the rim outward . If you have a leaf hit with a narrower rim by going to a wider rim with same BS moves mass outward. If you do not have the extra clearance at the fenders then that will become an issue. Its a balance for sure. Cut outs will end up being the answer for me. I just wish they would offer a rear cut out that did not need trimming fender to fit as you can clear 38-39 with out trimming in the rear. That is also the cut that causes the most issue.
I ran 37-13.50's with a 6'' procomp lift & never rubbed at all. Had to trim the bottom plastic on bumper. Now I run 38-15.50's with a 8'' lift and have no rubbing except on the springs at full turn.
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