Contour Enthusiasts Group Archives Forums Modifications Wheels & Tires Tire size: plus size question

I was wondering as I looked at the Tirerack web site at wheels and their recommended tire sizes:

If I buy 16" wheels and go with their recommended tire size, I still end up using a 205-width tire, so, what do I gain? [my current tire size is 205/60-15]

If I buy 17" wheels and use their recommended tire size (215/45-17) now I'm using a wider tire. I can understand how the wider width will help me in corners: more rubber working against lateral acceleration.

Then I played with the tire size calaulator on the Miata web site and I realized that changing to the 17" wheel/tire combo will put my car on tires that have ONE INCH LESS sidewall height.

My question is this: is the smaller sidewall height really much of an advantage on the street? Won't the (probably) heavier wheels have a detrimental affect on the driving dynamics of the car? Does the advantage of a shorter sidewall adequately offset the disadvantage of the heavier wheels?

Thanks for your time.

Mike

You answered the first question, you gain smaller sidewall height which improves handling. The extra weight of larger rims will mostly affect acceleration, but the handling will improve.

I installed new 17 x 7 1/2 rims on my Contour SE(from 15") with 215/45ZR17 Firestone Firehawks. I have noticed no ill effects from the change. What I have noticed with the suspension upgrades I made along with the tire/wheel combo is a car that handles much better than before. I also have room for brake upgrades now if I wish to do so. The shorter, stiffer sidewall on a lower profile tire does help handling by decreasing sidewall flex, but the rubber compound on a tire can increase coefficient of friction. That means the compound is softer and provides greater contact surface with the pavement . . . more contact, more traction and handling. It's also good if the same tire is designed for wet traction as well. Hope this helps.

Okay from what im reading i think you are gettin the measurements wrong , so if im wrong im sorry but here it is for you just in case:

ex: 215/45R17

215 = the width of the tire grips making contact with the road.

45 = the height of the side wall, measured in series, 40series , 45series etc. hince low pros-45 and lower series tire.

R = the speed ratings, i forget all of them off the top of my head, but they are available at any car or tire store

17 = the inside diameter of the tire or in other words the size wheel that this particular tire will fit.

Now i dont know which wheels you were looking at but if they recommended a 215 tire for the 17 and a 205 for the 16 this is prob why, the 17 is a 17x7.5 wheel and the 16 is prob a 16x7 wheel, however also as the lower series tire you go you want a wider tire for the added cushion on your wheel , because if you dont you could easily bent your wheel, like say you hit a pothole, the added pressure can actually bend your wheel if it isnt wide enough to distribute the added force!

hope that helped some

Not quite smothy1995.

ex: 215/45R17

215 = the with of the widest part of tire in millimeters.

45 = is the height of the side wall stated as a percentage of the width. (45 means the side wall height is 45% of the tire width.)

R = Radial tire.

17 = the wheel diameter the tire fits.

V or Z = one or the other would be the speed rating on this size tire. Ths rating is stated on the side wall along with a number like 90 that stands for the maximum waite the tire can carry.

The minimum speed rating I will use is H but then I don't have a hot foot or don't do any kind of racing. Also the higher the speed rating the heigher the price and the faster the tread wears out.

[QUOTE]Originally posted by RWReece:
[QB]Not quite smothy1995.

ex: 215/45R17

215 = the with of the widest part of tire in millimeters.

45 = is the height of the side wall stated as a percentage of the width. (45 means the side wall height is 45% of the tire width.)

R = Radial tire.

17 = the wheel diameter the tire fits.

V or Z = one or the other would be the speed rating on this size tire. Ths rating is stated on the side wall along with a number like 90 that stands for the maximum waite the tire can carry.
QUOTE]

NOT quite RWreece the 90 is the wear expectance of the tire. Not the max weight. A tire with a higher # will last longer.

Nope RWReece is right if you see something like 92V, that is the load and speed rating.

What you are talking about is the UTQG it would look something like 340 AA A where 340 is the wear rating, AA is the traction rating, and the last letter A is the temperature rating.



And to complete the beating of this dead horse, peep here for UTQG information. http://www.tirerack.com/tires/tiretech/general/utqg.htm

FWIW,

TB

Now that this has gotten completely off-topic lets see if I can get it back on track.

I understand that the shorter sidewall is supposed to give my car better handling. What I want to know is if it will make much difference for my daily-driver Contour on the street. [FWIW, I also know some of the trade-offs that are part of the shorter sidewall experience: harsher ride, less forgiving of potholes, etc.]

As for the other information about reading the size and the UTQG ratings, thanks for trying to educate me.

Mike

FWIW 215 is not the widest part of the tire. It is the width of the tread from inside to outside of the tread only, that does not include the side wall of the tire, just the tread.

Actually, both are wrong. The 205 or 215 is the section width, which is the measure of the width of the tire from sidewall to sidewall at the widest part. If you have raised letters, they are not considered part of the section width

Peep here: http://www.tirerack.com/tires/tiretech/general/size.htm

TB