245/75 vs. 255/70

LibertyCRD · **Posted:** Thu Jun 24, 2010 8:21 pm

This comparison is not 100% fair because each tire runs a little different, and Firestone tires are well known to run a little small.

But.. just for giggles today I mounted a 245/75-16 Firestone Destination AT on the driver's front ..... and left one of my 255/70-16 General Grabber AT2s on the passenger's front to see how they compared.

Visually, the 255 is bigger. The 245 looked small and almost "tiny" compared to the side with the 255 on it. With the tape measure, both tires were EXACTLY the same height...measuring near 29.5" tall from ground to top of tread with 37 psi of air in them. I guess it is the narrower width of the 245 combined with the milder tread pattern of the Firestone that made the 245 look so much smaller. It didn't seem to fill the wheel well up as nicely.

Audibly, the Firestone destroyed the General. The Destination was VERY quiet on the highway at 55 MPH...while I could still hear the "wawawawawawawa" roar coming from the General. Both tires ride as smooth as glass. It's just that the General emits noise that the Firestone does not.

Other things I noticed... the Firestone is MUCH lighter weight. Lifting the General after handling the Firestone revealed a noticable difference in weight. Also, this may be my imagination....but I could swear that I could "feel" less rolling resistance after mounting the Firestone up front. It was as if the Jeep would coast easier and it just felt like it floated over the roadway whereas the Generals have to be "pushed" along...if that makes any sense.

I would guess that with a set of 4 of these Firestones...my fuel economy would increase and the ride would be "light" and quieter. But the Generals simply look better and the tread pattern will obviously hook up better on and off road. So they really are two different tires that will excel at different purposes.

I was just surprised that the 245 looked so small visually. I expected it to rub worse...but it rubbed less than the 255.

InCommando · **Posted:** Thu Jun 24, 2010 8:51 pm

Only a 10 mm width difference...so it must be the visual "heaviness" of the different tread patterns, as you mentioned. Perception is not reality... :mrgreen:

LibertyCRD · **Posted:** Thu Jun 24, 2010 9:01 pm

InCommando wrote:

Only a 10 mm width difference...so it must be the visual "heaviness" of the different tread patterns, as you mentioned. Perception is not reality... :mrgreen:

I just went out and actually measured the tread width.

Firestone = 7.75"
General = 8.5"

that's .75" difference in tread width alone...which is more than 10mm.

ATXKJ · **Posted:** Thu Jun 24, 2010 9:51 pm

The 10mm difference is the Section width - widest part of the tire - not the Tread
lots of companies don't even report a tread width.
and of those that do - you can have 1/2 - 3/4" difference for the same section width

InCommando · **Posted:** Fri Jun 25, 2010 1:43 am

Metric tire measurement:

245, etc... = section width in MILLIMETERS

75,etc... = pereantage of section width for sidewall height (double this figure and add rim diameter to get height of tire)

16, etc... = rim diameter

tire firestone general

Tread Depth 13/32" 17/32"

tire Weight 36lbs. 41lbs.

Width Sect. 9.8" 10.2"

Width Tread 7.5" 7.5"

diameter 30.5" 30.1"

Perception vs. reality.

LibertyCRD · **Posted:** Fri Jun 25, 2010 7:36 am

InCommando wrote:

Metric tire measurement:

245, etc... = section width in MILLIMETERS

75,etc... = pereantage of section width for sidewall height (double this figure and add rim diameter to get height of tire)

16, etc... = rim diameter

tire firestone general

Tread Depth 13/32" 17/32"

tire Weight 36lbs. 41lbs.

Width Sect. 9.8" 10.2"

Width Tread 7.5" 7.5"

diameter 30.5" 30.1"

Perception vs. reality.

Reality is what happens when you actually get out a tape measure and get numbers off the tires in the real world. And the numbers above are wrong.

Which, now that I think about it, is the specific reason for this post.

InCommando · **Posted:** Fri Jun 25, 2010 8:30 am

Not getting huffy: this is common as to what people "see." Certainly people have their visual cues fooled daily. Measuremnets will vary with air pressure, rim type, and weight of the vehicle that the tires are on. That, and the numbers posted are representaional as provided by the manufacturer: as mentioned, some companies are notorious for their tires being less then what they are claimed to be.

I think a big point in the Grabbers appearng larger is the depth of their tread when compared to the somewhat shallow Firestones.

245/75 vs. 255/70

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