Third gear in my 3 speed auto transaxle is too low for even semi-fast highway driving, so I have been using P165/80 R13 tires which allow driving at 66.5 mph with the same rpm that 65 used for the stock 155 mm wide tires. They are also .63 inches taller than stock. Now, I would like to go to P175/80 R13 tires to give a similar increase in speed. Does anyone know if they will fit? It looks like they will, but one local tire store said they cannot legally install that size on my car. I have access to a tire changing machine and can install them myself. If they do fit, is it possible that they are less safe because of the 1.25 inch height increase over stock? I wouldn't think it would matter much myself.

I also want the wider tires to give increased traction in the wet. I am looking at Firestone FR380 tires which have a traction rating of A.

Thanks for any advice. Barry.

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Third gear in my 3 speed auto transaxle is too low for even semi-fast highway driving, so I have been using P165/80 R13 tires which allow driving at 66.5 mph with the same rpm that 65 used for the stock 155 mm wide tires. They are also .63 inches taller than stock. Now, I would like to go to P175/80 R13 tires to give a similar increase in speed. Does anyone know if they will fit? It looks like they will, but one local tire store said they cannot legally install that size on my car. I have access to a tire changing machine and can install them myself. If they do fit, is it possible that they are less safe because of the 1.25 inch height increase over stock? I wouldn't think it would matter much myself.

I also want the wider tires to give increased traction in the wet. I am looking at Firestone FR380 tires which have a traction rating of A.

Thanks for any advice. Barry.

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Too wide a tire on too narrow a wheel = danger for the person mounting the tire onto the rim, uneven distribution of load across the tread (resulting in center-worn tires, and unstable handling), and excessive heat build-up in the sidewalls causing premature failure which down the line may manifest as buldges, cracks or blowouts. Too tall a tire will only multiply the problems of having a tire that is too wide. Traction ratings are not standardized ratings, they are merely relative ratings within the spectrum of that manufacturer. From a specifications point of view, the most accurate way to predict a tire's performance are the treadwear and speed ratings. A lower treadwear indicates a stickier tread while a higher treadwear indicates a stiffer compound - end of story, regardless of traction rating, period. Likewise, a higher speed rating such as H or V indicates stiffer sidewalls and carcass nessecary to prevent distortion at high speed but perhaps more importantly it tells you that it will be a better handling tire for turning and braking as well, when compared to a lower speed rating such as S or T, which will have a floppier sidewall and less rigid carcass. When the professionals tell you the tire is too wide or tall, it's because they're covering their rear. The reason they're covering their rear is because installing a tire that is too wide or tall can be a safety concern, causing vehicle control problems that you do not expect, and when you lose control of your car unpredictably, they don't want YOU suing THEM. So ultimately it is in YOUR best interest to listen to them when they tell you there is a LAW prohibiting them from your wishes, and think about WHY that law exists. It would behoove you to go with a larger wheel (width and diameter) in order to properly take advantage of having a larger tire diameter. Goodluck and be safe.

-mechanicmatt

Mechanicmatt, thanks a lot for all of the valuable information. I found out that the Firestone P175/80R13 tires I want to use will fit 4.5-6 inch wide rims. Mine are 5 inch, so that is not the problem. It must be a handling or clearance issue. Also I found a website that seemed to say that the UTQG (Uniform Tire Quality Grading) relates tires across the manufacturing spectrum, not just within a manufacturer's own tires. I have been using LeMans Champion P165/80R13 tires which are rated traction grade A and wear grade 400. They are supposed to last 40,000 miles but will be lucky to make it to 30,000. This goes along with what you said about softer tires wearing faster.

One last comment about my Metro: It would have been great if the transaxle had been a four speed. As it is the first two gears are too tall and the third is too low.

Also, in case anyone is interested, the LeMans tires are only $18 each.
Barry.

Well I stand corrected and better educated. You have obviously done your research. Go forth and prosper! I agree that the automatics could have used an overdrive, probably a compensation to keep costs and drivetrain power loss to a minimum. Goodluck, and let us know how those taller tires work for ya.

-mechanicmatt