P275/40R17 rim size

[GotTorque?]

Hey BadAndy- I checked on that rims size for you and according to T&RA (Tire and Rim Association), a P275/40R17 tire fits on 9 to 11 inch J rim.

So it doesn't look like those would fit on your stock 8" rims.  But that size is the same exact diameter as the P245/45R17 and the P225/55R16 tires, so you wouldn't have to change a speedo gear or anything.

Cara

[doogz]

The diameter is the same, yes, but I wouldn't put these on an 8" rim. A 9" rim is a perfect match for a 275 width tire. Unless it's the Nitto 555 Drag Radials, in which case, they will fit just about perfectly on an 8" rim. A 315 is a good match on a 10.5" and a 295 is about perfect on a 9.5". Hope this helps!

[GotTorque?]

The diameter is the same, yes, but I wouldn't put these on an 8" rim.

LOL, you're right.  I should have made that next sentence a new paragraph- he was thinking about buying 9" wheels!

[BadAndy]

Well, I had '95 Cobra Rs with 275-40s and swapped with a friend for his stock '96 wheels. I got a couple hundred bucks out of it and helped a friend save almost $1k in wheels and tires. I like the Rs but they are too common for me...besides, with these stockers it gives me good incentive to save up for better wheels!!

[GotTorque?]

I think long ago you sent me a pic of the 95 (when it had flames) with 99GT rims.  I'd love to see a pic og the 95 with the 275's.  Thanks!!!

[GotTorque?]

Thanks for the pics- I'm sold on that size, they'll go on my nice new 17x9s perfectly!

[BadBlk95GT]

I gotta locate a set of stocker cobra rims...  94-98...  Or some Prostars.  I'm tired of the cobra R look and now I'm back on stock tri-bars...  blah

[Mr. Black]

I'd pay money to see someone try and put a 275 on an 11" rim. I don't even think you could get the bead seated.

[Bwhitty799]

I'd pay money to see someone try and put a 275 on an 11" rim. I don't even think you could get the bead seated.

bwhahah

[Dan]

Boo! BFG drag's! Boo! lol. I loved them, but they didn't last for s***.

[nophonypony]

 i have 275/40/17 on 10.5 rim and it fits fine but doesn't look as good as it should, because the side wall curves inward. i need to get 295 or 315 for that rim size.

[Mr. Black]

i have 275/40/17 on 10.5 rim and it fits fine but doesn't look as good as it should, because the side wall curves inward.

This is about as contradictory as it gets.

[GotTorque?]

i have 275/40/17 on 10.5 rim and it fits fine but doesn't look as good as it should, because the side wall curves inward.

This is about as contradictory as it gets.

[nophonypony]

i have 275/40/17 on 10.5 rim and it fits fine but doesn't look as good as it should, because the side wall curves inward.

This is about as contradictory as it gets.

Your right , I  guess the point I was trying to make was use a 9 or 9.5 wheel and don't make the mistake I made.  

[GotTorque?]

i have 275/40/17 on 10.5 rim and it fits fine but doesn't look as good as it should, because the side wall curves inward.

This is about as contradictory as it gets.

Your right , I guess the point I was trying to make was use a 9 or 9.5 wheel and don't make the mistake I made.

I think the point Mr. Black was trying to make was that if you put the tire on a rim that is larger than the measuring rim width (9.5 in this case), it will appear as the sidewall curves more outward than inward, because of the larger width rim. 

[Chowder Head]

I gotta ask this because I have no idea...

P275/40R17, and all of those other weird symbols.  What do they stand for?  I have not a clue.

[Dan]

P275= tire width
40R= R-speed rated tire with a 40(i believe it's centimeter) sidewall
17=rim size

So you can get something like a P295/35ZR-18 and it means the tire is 295cm wide, has a Z-speed rating, had a 35cm sidwall and fits on an 18" rim.

Someone correct me if I'm wrong. I don't know if the cm part is correct.

[Chowder Head]

Cool man, thanks.

2 more things.  Why is there a P behind the 275?  Why not just leave it 275?
And what exactly is a z speed and r speed rated tire?  Or do those letters act as variables?

[Dan]

A common Trade-Off for higher Speed-Rating is reduced Ride Comfort. An "S" Speed-Rated tire will give a more comfortable Ride compared to "H" Speed-Rated tire, and a "H" Speed-Rated tire will give a more comfortable Ride compared to a "Z" Speed-Rated tire. The Ride Comfort Characteristics can be attributed to the tire's Overall Stiffness. A tire capable of running at High Speeds requires a more stiff construction, in order to provide the necessary high speed stability & durability.

Tire Speed Rating Symbols:

S -- 180km/h or 112mph

T -- 190km/h or 118mph

U -- 200km/h or 125mph

H -- 210km/h or 130mph

V -- 240km/h or 149mph

W(ZR) -- 270km/h or 168mph

Y(ZR) -- 300km/h or 186mph

ZR -- Above 300km/h or 186mph

A Z-Speed Rated tire without a Service Description means that the customer must consult the Tire Manufacturer to obtain the tire's Maximum Speed Capability.

[Chowder Head]

Alright, that helps out a lot, thanks Dan.

So what to look for when you're shopping for a tire is to guess the maximun speed you will do and get the next highest tire to ensure maximum ride comfort?  Something like that?

And what if you have an S rated tire and you go beyond 112mph?  Will it shred or something?
Sorry for all these questions, I'm finally trying to learn about tires, lol.

[Dan]

You own a Mustang dude. Don't worry about ride comfort.

Most any respectable tire that will go on your rims should be at least H rated. I think the factory rubber from 87-93 was H-rated 255's. If you're going to spend the money, get yourself a nice set of Z-rated tires. They won't hook like drag radials or help your car corner like a Porsche, but you will notice a huge difference over your factory meats.

If you go over the speed rating, you're not going to die. But the reason the rating system came about was because of the Autobahn. If you were going to be cruising at 140mph for 50 miles, you don't want S-rated tires. So if you have H-rated tires, you can do a 70-140 blast down the freeway, back down to 70, and finish out your trip without worrying about your tires blowing to bits. But it's recommended that you don't STAY at 140 the entire trip.

[GotTorque?]

Why is there a P behind the 275? Why not just leave it 275?
And what exactly is a z speed and r speed rated tire? Or do those letters act as variables?

Michael-

To answer your question, the prefix letter (s) indicate the service conditions as part of the T&RA (Tire and Rim Assoc- based in Ohio) size designations.  It's purpose is to differentiate between service types to give you the different load and inflation conditions.

P stands for 'Passenger', and is a tire primarily intended as a passenger tire

LT is a 'Light Truck' tire

And T is a 'Temporary' Spare tire.

If the tires have these (and a couple other) prefixes, they are designed per T&RA standards.  If not, they are designed by a european or japanese design standard (something other than T&RA).

As for speed ratings, you should never use a tire that is less than what your OE load and speed rating was.  See Dan's chart for equivalent speeds. 

For example, if your original equipment tire is a 95W, you should only use a tire with a 95 or higher load rating, and a W, Y, or Z rated tire. 

Also, the 'R' in the size just denotes it is a radial tire (as opposed to a bias ply).

[doogz]

The middle number is a percentage of the width of the tire. A 295/35/17 is 295 wide, 35% of that 295 is sidewall, and the 17" at the end is obvious.

[GotTorque?]

The middle number is a percentage of the width of the tire. A 295/35/17 is 295 wide, 35% of that 295 is sidewall, and the 17" at the end is obvious.

Good call- I didn't read that part.  Also, tire width is in mm.

[Dan]

Ya learn sumfin every day!