All

Getting ready to put some new tires on my 2006 LR3 with stock factory wheels. Replacing stock 255/60/18 with 265/60/18. Just happened to check my spare for air pressure and noticed it is a 175/80/19. How is that?

 

The non-HD package LR3s, which is the vast majority, came with a temporary spare.

 

Obviously just a temp spare and diameters aren't necessarily same as wheel dia. as it's designed to work on all the size choices of the model/year.

......

 

First, your Rover doesn't care how wide the tires are, only that they're the same diameter side to side. Though you may not realize it, your spare is the same diameter as your stock tires.

Pay attention now class!

Tire diameter = section width * aspect ratio *2 + wheel diameter.

• Section width is the first number (255). It's always given in mm, so we'll have to convert that to inches.
• Aspect ratio is how tall the sidewall is as a percintage of the section width. (60%) Since you have to have both the top and bottom sidewalls to get the full height, we'll double that.
• Wheel diameter is always given in inches (18)

(keep in mind this is the theoretical tire size and in reality each tire model will measure out slightly differently, but without physically measuring each tire this is as close as you can get)

Let's do the maths!
So....

255/60-18 = 30.05"

255mm=10.04" (255/25.4)
10.04 * .6 = 6.024
6.024*2 = 12.048
12.048 + 18 = 30.048. We'll call that 30.05", or really let's just say a 30" tire.

Run the numbers for your spare and you'll see it's basically the same diameter despite being much narrower.
175/80-19 works out to 30.02". Also a 30" tire.

Your new 265/60-18 works out to 30.5"

Will you be OK running a .5" smaller tire in an emergency? Probably. Certainly on soft surfaces like gravel or dirt. On pavement I'm not sure how far you can push the LR diff. I would not do it any more than necessary, but my guess is you'd be OK for short emergency runs.

The correct answer or course is to buy a used full-size spare wheel and mount a proper matching spare tire. If you're ever out in the bush and have a flat you'll suddenly think it's money well spent. Of course there's significant expense, but it's somewhat offset by being able to do a 5 tire rotation so you'll get a bit more life out of a set of tires.

 

yeah people part out sets of wheels here all the time. Just match your set. If you have the 10-spokes, you're lucky since that's the most common style.