This is not my strongest subject, but I will give this a try. In the beginning Mustangs came with 14 and 15 inch wheel sizes. For about a year Michelin built a 15.5 tire for FORD that are un-obtanium.
Yep, they are metric tires, at one time produced by Michelin, I believe the size was 220/55r390 (I think????) You can probably still get them from Coker (thats the guys Michelin sold the molds to), Ford and BMW used these. unlucky souls
16, 17, 18, and 20 inch tires are built mostly for extreme performance. The idea is to reduce the sidewall's influence upon the suspension in order to gain high speed cornering ability. That is why you see 35, 40, 45 ratios so commonly.
Depends, big brakes, and styles drive this alot in OE and aftermarket situtations. There are a few luxury hi-perf tires out there.
It used to be that all street tires were 75 or 70 ratio tires. That means if the tire was 5 inches wide, it was 3.5 to 3.7 inches tall from rim to tread.
Here you go, this how the service description breaks down.
eg; P245/50r16 XXZ
P = Passenger
245 = Section width in milimeters (not tread width)
50 = 1 of the tires aspect ratios, in this case it refers to the height of the sidewall in relation to the section width. As it pertains to this size, it means the sidewall is 50% of the section width.
r = radial construction
16 = rim diameter.
XX = This would actually be a numeric designation and refers to the maximum load the tire can carry at the maximum tire pressure branded on the side wall (alot of people confuse this with what air pressure the tire needs.)
Z = speed rating (in this case it refers to tires designed for 149+, for passenger use you will see;
S = 112
T = 118
H = 135
V = upto 149
Z = 149 +
W = 178 (??)
Y = 183 (??)
ZR = Doesn't have a maximum speed listed.
The speed rating refers to the tires ability to withstands sustained operation at those speeds for upto 8 hours without failure. In truth it does not denote the actual performance capabilities of the tire beyond its ability to withstand a sustained speed in a defined amount of time.
HOWEVER certain generalizations can be made as to the way the tire affects handling and performance. It
IS unwise to go to a lower speed rated tire than the one originally equipped on the vehicle.
IF you do, the vehicles maximum speed is limited to the specification listed on the tire
AND it will effect vehicle braking and handling.
The most important thing when it comes to selecting a tire is rim fitment and load carrying capability. Tires have approved rim widths which should be observed. As for load carrying capability. You need to figure your gross weight. (ie; You like to cruise with 5 fat chicks in your car with a full tank of gas and an all iron 460 under the hood with the killer S/C set-up. The bass death machine in the back, and over the top hydraulics, plus a trailer hitch and your boat). Bad things will happen if you just throw what looks kewl to you on there.
With an 18" 35 ratio tire a 7 inch wide tire is just 2.45 inches from rim to tread. So when cornering at 100 mph, the sidewalls produce less distortion to the suspension, allowing the car to groove.
Heres how you do this;
SECTION WIDTH x ASPECT RATIO (expressed as a decimal) / 25.4 = height of the sidewall.
SW x AR / 25.4 x 2 + RIM DIA = Nominal unloaded tire dia. (this is useful for making broad comparisons)
As you go up in rim size, you can retain ride comfort by going a 45 ratio if available. When you get to 18 inch tires, you are going to primarily find 35 and 40 ratio tires. But in 17 rims you will find 45 and sometimes 50 ratio tires.
Generally speaking, as you retain sidewall height the tire will ride better (the sidewall is a sort of shock absorber), However it depends on how the sidewall is constructed. There are tires on the market which have very pliable s/w with excellent cornering and turn-in capabilities.
A ZR rated tire has lots of stick, but don't expect it to last more than 25-28,000 miles. I prefer Z-X rated tires, which go between 35,000 to 40,000 miles. They are a little harder rubber, A GOOD THING ON THE STREET, but will not give you the great stickiness of a ZR.
Generally speaking, yep. However there are variations in here. For example BF Goodrich produces a line of ZR tires. The GForce tire line has three models.
KD (Key Design) = there big dog dry handling tire
KDW (Key Design Wet) = excellent wet tire
KDWS (Key Design Wet & Snow) = all season hi-pef tire.
Its interesting to note that there are some Z-rated tires out there with Tread Life ratings approaching 400. Big whoop you say, however a few years ago in the same brand of tire a manufaturer introduced an 80,000 mile warranty on a 400 treadwear tire.
Heck on the 02, my Goodyears are gonna go 40k.
Maintenece, suspension design, vehicle weight in relation to tire size, road conditions, and driving style are a few things that can effect tire life (Honda fits there vehicles for the most part with H and V rated tires which routinely go 40-70k before replacement)
As you move down the line you give up ulitmate handling capability for more balanced tire performance.
By the way, if you go 17 inch rims, the tires will be much less expensive. If you want to go ZR tires, then 17 inches will be much less expensive over the years.
Yep