Tire size question

[GP John]

I have an 86 Grand Prix with the original turbo style rims. I am unsure of their width I will have to look into that. The original size is 195/75/R14.

Currently I have T/A radials that are 205/70R14. I want something just a little wider and thought I would get 205/60/R14. Now a mechanic was telling me to get 215/70R14. His explanation is that they are a little taller but will spread the side wall out due to rim width and be a little wider and the higth will come down due to the tire spreading the sidwall. Hope that didn't confuse you. I want to get it right what do you think?

 

[supercrackerbox]

A 205/60/14 won't be any wider than a 205/70/14, just shorter. Metric tire sizes are broken down as follows:

Width / Aspect Ratio / Rim diameter

Width is measured at the widest section of the tire (Not necessarily the tread) in millimeters for a specified rim width.

Aspect Ratio is the height of the sidewall in relation to the width. That means if the measured width is 205mm, the sidewall height will be 70% of the width for a 70-series tire.

Rim diameter is of course the size of the rim that the tire will fit.

So, if we use the specs listed for BFG Radial T/As, your current 205/70/14 tires will have an overall diameter of 25.4". If you choose a 215/70/14, you will have an overall diameter of 25.9", or half an inch taller and 10mm wider. You could also try a 235/60/14 which will be 30mm wider, but 3/10" shorter than your current size.

http://www.tirerack.com/tires/Spec.jsp? ... 4RADTARWL2

Your factory wheels are (most likely) only 6" wide, and anything wider than a 235 is not recommended. You "can" fit a 245/60/14 on, but you will wear out the center of the tread very quickly even if you run dangerously low air preassure. Been there, done that.

 

[GP John]

Thank you that is the information I was looking for. Sounds like the information backs up what I was told so I feel good enough to go with the 215/70 . I will be just a little wider and not enough extra higth to throw the speedomoter off, or at least not too much if at all.

 

[dogsht]

Adam I had a friend that ran 205/70/14s (25.4") in the front and 245/60/14 (25.6") in the rear with like 28lbs air in the back. His seemed to wear pretty well.

 

[supercrackerbox]

That's the combo that's currently on my Regal, and I've taken them as low as 26psi with no extra weight in the trunk. Cheap tires, yes, but they're pretty thin in the middle.