HOHN

Because I really want the M55s is why. I'd get the M/Ts because Toyo doesn't offer any really tough E-rated 315s other than the M'Ts (sorry, the A/Ts aren't what I want).

Another thing in favor of the M55s is that in the 285 size, they are EIGHT pounds lighter per tire! That's a huge amount of unsprung weight, directly bearing on mpg and ride quality.

Longer treadlife of the M55s, lighter weight (and still rated for high loads), and a tread pattern more appropriate for my needs have me leaning about 70/30 to the M55s.

I off-road rarely, but I tow even less often. I can't afford to buy anything to pull

MSquare

OK then, so we both get M55's then!

I'm leaning 80/20 towards them. My brain say's that is the right choice, based on performance. My "little brain" say's MT's based on looks.

CRAP!

xtoyz17

From what you said right there, I don't see anything other than more and more reasons to get the M55. Personally, I couldn't/wouldn't justify the 315 if I were you. The only thing going for them is the "cool" factor, and the "cost" factor is hands down M55 winner.

If I had known about the M55, I'd be driving on those instead of my Wranglers.

Buckshotram

I love the way 315's w a leveling kit look I dont understand why dodge made the rear big enough for 37's and but 245's on from the factory. Ive had 285's, 305's and now 315's My milage has deff dropped with the 315's I guess Im going back to 305's which handled the best on my truck next time since fuel is $3.30 a gal here. However If I had 4:10's I think the 315's would be a nice combo.

HOHN

For clarity, the 285 M/Ts are 8# heavier than the SAME SIZE M55!

The 315s M/Ts are a beastly heavy tire at over 70# each

Heck, maybe I'll just stick with the homely little 265s. With non-oem tread, they work very well, even if the look isn't my favorite.

Those michelins got me stuck in wet grass a couple times and had to use 4wd

Philabuster

Yep, 315's (load range E) on the stock 8" alloys. I uploaded a few pics to my member gallery awaiting approval. I have a flat contact patch with 55 psi front and 40 psi rears. No noticeable wear yet, but I have only 2K miles on them. Funny thing is I can actually accelerate faster from a stoplight with them vs the 255s. Reason being, I ran out of gear in 2nd quickly and it would take 3rd gear to really load the motor and build boost. 2nd gear has longer legs now and I can get on it from a standstill then hit 3rd and keep pulling. I'm not slipping the clutch very much at all, but I can't just dump it without any skinny pedal like I used to do. However, from 55 MPH on up in 6th gear, the 255s accelerated quicker because the tires were lighter in weight, had lower rolling resistance, but the main reason, the engine was closer to peak torque.

Yesterday was that time of the year for me *cough* smog check *cough* and the Smarty was put back to stock. Big tires and stock fueling sucks. The ECM was back on Kung Fu later that day.

I remember reading a Cummins pdf file about fuel economy and it mentioned worn out tires get 13% better fuel effiency than new lugged tires of the same size (pdf file talking about OTR trucks, but most of the tire and windspeed examples are valid for us too).

In the same pdf file, it also mentions the Cummins PowerSpec gear calculator.Regardless of my input parameters, it reads not to run the engine lower than 1,900 RPM at cruise speed. With 400hp on tap in a 7,000lb truck, I'm not sure it applies to your situation.

Buy the M55 in 285's. You don't need us to convince you it's the right decision for you. You've done your homework.

Picking tires is easy compared to picking a turbo--remember?

chainzaw

Check out www.tirerack.com . That's where i bought my tires. You can compare different tires and their overall performance. I settled on the pirelli scorpion ATRs. I can't remember the size! and it's to late and cold to go look.

HOHN i know you don't want an AT. These tires have been a great compromise across the board. Class E still have great towing. No annoying tire noise. Good tread life. And most importantly i haven't got stuck yet! ... but then i have warn winches so it doesn't matter if i get stuck!

IMO they look good. All my picture file sizes are to big to load on DTR. I can try to take some smaller ones tomorrow if your interested.

HOHN

We ran the Pirellis on the missile field trucks that the ICBM crews drove. They didn't impress me that much. About 30K and they were gone. The Cooper ATRs are what we converted them to with better results.

JH

HOHN

Phil, thanks for the great post! I've read that Cummins .pdf a couple times when it first surfaced a few years back. I agree with everything it contains; even if the specifics aren't directly applicable to a Dodge truck, the general principles certainly are.

The PowerSpec link interests me. But I also doubt it a little bit myself. First, if you look at the BSFC curves for our engines, they are fairly flat and low up to about 2K rpm, after which they get worse at a progressively faster rate. The engine is most efficient between 1400-2000 rpm according to Cummins' published BSFC data, with 2K being the peak of efficiency.

So I find it odd the Cummins discourages cruising RPMs under 1900, but I think I understand why. First, they assume stock power levels and want to avoid lugging. Second, they assume much higher loads than my always-empty truck can apply to the engine. Thirdly, they are assuming the RV/industrial configuration of the ISB, which redlines at 2600rpm, and not the Dodge application which revs higher (though that seems to favor taller, not shorter gearing)

I can see Cummins point though-- why gear a truck so tall when the Cummins will pull 2700rpm all day everyday with no damage, and the variable fuel ratio of a diesel means that lowering rpm doesn't give much a MPG benefit in return.

When I put in my FACTORY specs into the PowerSpec, Cummins says I am geared way too tall with my factory 265 tires, so I'm suspicious of the direct applicability to to a the bombed CTD-in-a-Dodge scenario.

Now I'm even thinking about staying with 265s, just going to the M55 tires I want to badly. That's the cheapest option for me, and looks like a good one that still preserves the factory gearing.

jh

BarryG

Justin:
I am running the m55's in 285. They have been good so far. Have about 30-35k on them maybe 1/2 worn. My only complaint is the noise. It is not overly loud but for me it is annoying. I personally would prefer Lexus type quiet on the inside of the cab I know that is not the general consensus here but...
The m55's do well dry, snow, mud and are pretty decent in the rain as well as tow great. Previously I had run the Bridgestone Dueler Revos in 265 size and really really liked them. Probably the best tire I have run and would go 60k on a set. They performed great in all conditions except gooey mud. Which is why I switched to the m55's that and I really wanted to go up one size and the revos do not have an E 285. I felt I needed a better tire in the mud for our property.

Mileage wise I can still get over 20 on my trips to our property that is down by Mesa Verde which is the same as I was getting with the 265 Revo's.

Both 265's are the same weight. The m55 285 is 6lbs heavier than either in 265.

You said you dont tow but will say anyway that I did notice the difference in size driving in the mountains. Empty it is of no real consequence. However towing in the mountains it is more noticeable due to lower speed and higher weight. I do have to think about it a bit going up the twisty curveys at lower speed. Going up I-70 to the tunnel no problems but once on the US highways like 50, 160 or 285 where the roads dont lend themselves to quite as much speed it does come into play. With your manual it may be a mute point as you have 6 gears to choose from. My auto I run out of OD more than I did before and there have been times when I have had to drop to 2nd where as with the 265s I didnt. For my driving there is no way I could go with 315's without changing the gearing for towing in the mountains.

Again quite happy with the 55's except for the noise.

Philabuster

Pics are approved!

Toyo M/T 315s on stock 8" alloys. I really like the look and ground clearance they provide. I still think 3.73 gears are perfect for the 315s size tire, which is the same effective ratio as 3.54 gears with 285/75s or 255/85s. I'm still on the fence if I want to change gearing or go to a 285 tire if some Mach 4s don't help as much as I hope they will.

1BAD4X4

Nice truck, makes me want to ditch the parts I have for my 3" lift and go for a 5"! The flares really look photochopped, but I gotta ask... are they real?

gies

3rd Gen Flares??

HOHN

Darn it Phil! Why'd you have to go and do that?? I had almost talked myself out of 315s, and there you go

That's more lift than I'd like, but they look PERFECT on the factory alloys.

Gearing, schmearing--- I'll have plenty of grunt to turn them

MSquare

Hey Phil - Is that a Ridgeback in the lower picture?

Hohn - Dang it! Make up your mind, you had me leaning towards the M55's!