Ultimate tire fitment chart

Re: Ultimate tire fitmant chart

Ridgeline Racing said:

...Also wheel width and offset play a role in fitment and clearance.

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That's something I'd also like to tackle, but I will need some help collecting the data. I can find the stock offset and some popular offsets for wider rims, but I just haven't had the time to dig any deeper yet. If people want to submit info on the rims they have tried and product links, I can make a similar chart that also acts like a shopping catalog. That's where I was headed with the tire chart (PDF and XLS versions), but just ran out of time. I also don't know what kind of conflicts there are since I began linking to TireRack, but Discount Tire is an official sponsor. Neither company carries every size in the chart, and I'd prefer not to have any gaps.

More inpuuut!

Re: Ultimate tire fitmant chart

Sabot said:

Great job! I am crossed eyed after spending the better part of today figuring out the tire industry...

I really like Tire Rack's survey system. Not sure how accurate it is but so far it seems like one of the best thing for me to use...?

I am searching for the widest tire with the most height I can get but one which excels in wet conditions. So far... using Tire Rack's survey... narrowed it down to the Yokohama Parada Spec X. Funny thing about the survey, it's the same on 265/50-20 and 275/45-20. Is this possible or are they cheating (via cut/paste)? What would I gain by going either with a 265/50 vs 275/45? My main concern is the sidewall's height. I use my Ridgeline as a truck and pull my 16' alum boat (800-1000lbs??).

Click to expand...

The reason they are showing them being the "same" is because of their overall diameter. They are taking a rather broad view of calling them equal. According to our chart, the 265/50-20 is 30.4” tall. The 275/45-20 is 29.7” tall. At least according to the numbers, the 265/50 is 7/10" taller than the other.

Here's the simple math. Metric tire sizes are mathematical formulas. A 265/50-20 is a tire that is 265mm wide (measured at the sidewall, not the tread). It's sidewall height is 50% of that width from the edge of the rim to the tread, or in this case 132.5mm. 20 is the diameter of the rim in inches.
So it is a 265mm wide, 132.5mm "tall" section of rubber. The other tire would be a 275mm wide, 123.75mm tall section. The 265/50 is roughly 1% narrower, and .9% taller.

As for the pros and cons, generally a taller narrower tire gives better cushion, protects the rim better, and provides a smoother ride but has slightly less traction. A wider, shorter tire will give greater traction, resist sidewall flexing and will corner better, but will get (slightly) worse mileage due to to higher friction. There are also varying degrees of difference in the way wide versus narrow tires perform on wet or slippery surfaces due to the difference of weight distribution over the tread.

All that said, I think you'd have a hard time noticing any difference in these two tires given how close they really are to each other. This would be a much different story if you were debating a 245/70-17 (30.5" tall) versus the 265/50-20 (30.4" tall). Same overall ride height, but 3 more inches of rubber instead of metal and 20mm difference in width.