JKlad

OK, so I understand how different aspect ratios affect on-road performance on street tires for cars, however was wondering the implications for A/T & M/T tyres offroad.

On car wheels for example, and keeping the rim size and width constant and without altering suspension settings or tire pressures, lower profile tires (eg: 205/50/16) will generally give better cornering ability on the blacktop than higher profile tires (eg: 205/70/16), with the trade-off being an increased firmness in ride and of course the effect on the vehicle's gearing of a smaller diameter tire unless a wider tire is chosen.

Many people here use tires of different aspect ratios from the stock ones (ie:255/75/17 for a stock '09 Rubi tire for example) when they change out wheels and tires and get a lift in order to increase their tire diameter or width (or both), and I was wondering what are the costs & benefits of higher or lower profile tires offroad, as obviously high-speed cornering isn't a concern.

genesbro

By getting taller tires you get more ground clearance and better breakover angles. Taller lets you air down and still have height and lets the tires grab onto rocks and ruts for traction. And airing down give you a much bigger footprint kind of like a tank tread.

Agassizii

Also consider this: while a wider tire has a larger contact patch than a narrower tire of the same diameter, when aired down (the same percentage of normal running pressure) the contact patch grows faster fore-and-aft (length, as in a tank tread) than side-to-side (width, due to bulge of the sidewall).

Practical effect; the difference in size between the two contact patches while aired down, is less significant than when fully inflated. Naturally, the wider tire will always have the larger contact patch (for a given percent of normal running pressure). But when both are aired down, the "skinny" tire has a larger percentage of the "wider" tires flotation.

Many would maximize both width and diameter -- mud, very loose sand, deep snow require the best flotation you can afford. If your need is versatility in all types of terrain, you get the most bang for your buck with increasing the diameter as a first priority.

glennco

The real benefits for having a higher aspect ratio are the following:

1: Sidewall flex- more Sidewall can flex instead of tear when you are scraping a rock or tree root

2: airdown- A tire with more Sidewall can be aired down for better flotation.

This doesn't necessarily mean getting a taller tire, just not such a tall wheel.