Mickey Thompson tire size chart

ROMM · #1 (**permalink**) 08-11-2007, 01:09 AM

Hey fellas, I have been wanting to buy a set of drag radials for my back tires. The Mickey Thompsons have been getting good comments on this board. I have seen alot of guys going to a bigger rim to get the 325 size tires on the back. Well on the tire size chart on the website it says that the P325/50R15 measured on a 10 inch rim has a tread width of 11.6.
For the P315/60R15 measured on a 9.5 inch rim it says the measured tread width is 11.9!!!
Can someone explain this to me? Why the heck does a wider tire on a wider rim not have MORE tread width? Also, what if you went with a 10.5 inch rim with the 325 size tire. Would that give you any more tread width? Why is a 10 inch rim the measuring rim size anyway? Is it because that is the optimal size rim for that tire? And if a bigger rim would give you more tread width, why wouldn't they use a bigger rim size to measure with on their advertising chart?

According to this chart, I can save money by not buying a new set of bigger rims and even get more tread width! WTF?

Silverback51 · #2 (**permalink**) 08-11-2007, 01:28 AM

I can provide two possible explainations.

First, it may be a misprint.

Second is that the 315 and 325 designations represent the cross section width of the tire, not the tread width. Depending on the tire construction it is possible for as smaller size tire to have a greater tread width.

It's not unusual to see different makes of tires for the same size to vary in tread width. Pirelli tires are quite often amoung the widest as they tend to be a square shoulder design.

Hope that helps.

fsstnotch · #3 (**permalink**) 08-11-2007, 02:15 AM

My guess... 10mm is less than 1/2 inch. The specs just aren't accurate.

All the sites i looked at said they were almost identical. Comparitively equal on a 10" wheel they measured

325/50-15
11" tread width
13" section width
weighs 36lbs
overall diameter equal to 28"x13.50"-15

315/60-15
11" tread width
13.4" section width (due to larger sidewall)
weighs 40lbs
overall diameter equal to 30"x13.50"-15

SO... depending on what you plan to use the tire for, a taller/heavier tire could hurt quite a bit.

greg schroeder · #4 (**permalink**) 08-11-2007, 09:40 AM

Sidewall height is the given % of sidewall width.

I have the 325/50 15 on 15 x 9.5 wheels with 4 inch backspace. The driver side on my car had an extra hunk of fiberglass on the inner wheel well that I had to fix so the tire didn't rub. The passenger side has plenty of clearance. I would like to see the wheels wider and the tires inward about another .5 inches.

I don't think I'd want a tire that's taller. At a time I thought my tires were 27 inches tall because I was measuring them on the car, but I recently removed the tires. They are in fact real close to 28 inches tall. A 315/60 15 of 30 inches tall would look a bit off in my opinion.

I have a 3.73 rear gear.

Tire chart
http://www.mickeythompsontires.com/s...ETStreetRadial

RedBarchetta · #5 (**permalink**) 08-11-2007, 01:49 PM

What Greg said. You can also look in my gallery to see what the 325's look like on a 10.5" wide rim with 4.5" offset (corrected...was 3.5" stock but I added 1" to the inner side). Ideal height would be 27", but off the car they will measure a bit taller. On the car mine are right at 27" (28psi...I run between 28-30 psi to keep the sidewalls stiff for better cornering). But even at 27" they are tall on the car...I had to set my springs down to make it look correct and mean.

-Dean

ROMM · #6 (**permalink**) 08-11-2007, 05:38 PM

Ok well thanks for all the replies. This morning when I went home from work I checked my rear tire sizes. I have the Goodyear Eagle GT 2. For some reason I thought they were 295/60's, which would be a taller tire. Well they are actually 295/50's. I measured the tire and its roughly 26.5 inches tall. There is no way I am putting a taller tire like the Mickey Thompson 315/60 on my car. Looks like my options are either to do like Greg and put the 325/50 on my stock 15 X 9.5 rims, or go with some 17" rims with some 325's. Both these options are roughly the same height as my current rear wheel, so no need to mess with gearing and stuff.

Anyone have any experience with the trade offs of going with a bigger rim, like going form a 15" to a 17"? Logic says that straight line performance could suffer, but cornering would improve. Would that 2 inches and shorter sidewall really make that big of a difference? I really wouldn't want my straight line performance to suffer a whole lot. And then there is the whole thing with the drag radials. Say you go with the 17" rims. However, you are putting drag radials on them. Well there goes your cornering improvement! Too much unexplored ground

Also, where do you get the proper backspacers??

fsstnotch · #7 (**permalink**) 08-11-2007, 09:22 PM

Honestly... i don't think your straight line would suffer at all. Maybe a normal car, but you are running a cobra with a 427R! You've got more than enough power to overpower the 17's and the 15's. In a straight line, I would seriously doubt you are using up all your 427R power. Where if you have a 300hp mustang, it's using all it's power to run a straight line. Add larger wheels and you lose like .1 in a 1/4.

On the other side of the spectrum, you will handle MUUUCH better!

Slojo · #8 (**permalink**) 08-12-2007, 07:17 PM

Hey Greg, there is a photo in your gallery, page 1 on the left hand side with a caption about "17's". Your post above here in this thread indicated that you are running 15's. Just curious which is which because I admire your performance and I really like the look of you car in that particuar photo.

greg schroeder · #9 (**permalink**) 08-12-2007, 09:03 PM

Quote:

Originally Posted by Slojo

Hey Greg, there is a photo in your gallery, page 1 on the left hand side with a caption about "17's". Your post above here in this thread indicated that you are running 15's. Just curious which is which because I admire your performance and I really like the look of you car in that particuar photo.

These are the 15s on 4 inch backspace 9.5 wide wheels with Mickey Thompson ET Street Drag radials. I lowered the rear a little bit. I think they look a whole lot better on Red Barchetta's 10.5 rims. I drive around with about 20 lbs and they handle ok.

These are the 17s with 315/35 17 Yokohama Ao32R soft compound tires on the rear. They aren't real good for hooking up because they're a track tire which generally won't get hot enough to work on city driving. I did notice they make a Mickey Thompson ET Street drag radial in a 315/35 17. I'd like a set of those.