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Old 07-20-2018, 10:18 AM   #1 (permalink)
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truck tires...

The time is coming for me to swap tires on my Ram (2005 4x4 QC diesel, manual trans, 370k miles) and a question has come to mind which I need some expert input on...

RE: Current tires... I have currently 285-70-17's (33" tall) on there and can easily get 21's for mpg. This is to & from work, to & from trailheads (dirt roads) and minimal city driving. If I put a % on it, I'd say 90% hiway is what I do. Living in the Seattle area, nothing is flat, I get to leverage the hills quite a bit coasting in neutral.


Possible future tires...From past experience with a 285-75-17 (34" tall) on long road trips 22's were easily had. City mpg however suffered when mixed. I'd have to go back and dig up receipts but 18's come to mind for combined mpg during the warm months.

Currently my commute miles with all the cold starts, rush hour traffic and many trips, I can out perform straight hiway miles for mpg. Seems if I get on the longer road trips I'm down ~.5-.75 mpg vs commute mpg. I know if I go to the taller tire, the commute mpg may drop because of the added load on all of the take off events. But, the question is...

If I have a taller tire (+5# over shorter tire) vs a shorter tire, whats going to happen to the coasting performance going down hills? I will be going with the same tire which is an Toyo Open Country AT2. I know going up will suffer because of the taller tire and the added weight but can that be made up on the backside of the hills?


edit: adding mpg data from before and after tire swap.
https://ecomodder.com/forum/showthre...tml#post583520


Toyo Open Country AT2's 110k miles on them (speedo was within +/- 0.5 mph)
09/1/52018 425.0 18.432 23.05772569 100% eco
09/22/2018 453.3 19.624 23.0992662 100% eco
09/23/2018 216.0 10.366 20.83735288 DGAS tank
09/29/2018 491.7 21.142 23.25702393 100% eco
10/08/2018 263.4 13.004 20.25530606 DGAS tank
10/13/2018 400.8 17.87 22.42865137 100% eco
Totals 2250.2 mi 100.438 gal 22.40387104 mpg average



Mazama Tires (speedo updated to within +/- 0.5 mph)
10/18/2018 535.1 25.471 21.00820541 100% eco
10/21/2018 519.5 27.768 18.70858542 DGAS tank
10/26/2018 492.1 25.792 19.07955955 DGAS tank, test & tune
10/28/2018 496.4 25.279 19.63685272 100% eco
11/04/2018 406.3 20.693 19.63465906 100% eco
11/10/2018 357.2 17.832 20.03140422 100% eco tune change, went to previous best performer with 33's on there
Totals 2806.6 mi 142.835 ga 19.64924563 mpg <-Average


Last edited by steve05ram360; 11-10-2018 at 06:19 PM..
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Old 07-20-2018, 11:20 AM   #2 (permalink)
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Do you really need the AT tread design? My Excursion is our dedicated TT tow rig, sees no off roading and I try to keep it off the road for Winter to avoid the salt and rust. I run the Nitto Dura Grapplers that are the rib style highway tread and am seeing a little better mileage than most others with similar size vehicles and tow combo weights. It's 6.8 liter V-10 gasser and sees 8 to 9.5 MPG on highway towing trips at 65/68 MPH with a combined weight of 19,500 lbs. I feel that these super quiet LTs are part of that result, these are the quietest truck tire I have ever used, you just don't hear them. The tires are oversized at 305/70R18 (35.28"X12.8") being turned by 4.88 gears on a 4" lifted EX. My daily driver is a '94 Metro XFi, so that's helps to soften the blow of the fuel cost from the long towing trips.
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Old 07-20-2018, 12:32 PM   #3 (permalink)
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I bought a 8000 mile used set of takeoffs of a 2015 Ram LT275/70/18 Firestone transforce mounted and balanced on chrome rims for $350. Those new truck guys often right away want a unique set of rims and big mud tires and almost just give away the stockers once they get tired of tripping over them in the garage or beside the shed. So I get taller tires which put the rpm at 1900 at 65, a nice quite highway ride, they still work just fine on the dirt mountain roads I go on including one particularly narly one in the prior mountains. $350 was probably a $500 savings compared to getting new taller tires for my 2004 17" factory wheels which buys a lot of diesel.
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Old 07-20-2018, 09:36 PM   #4 (permalink)
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Quote:
Originally Posted by WE3ZS View Post
Do you really need the AT tread design? My Excursion is our dedicated TT tow rig, sees no off roading and I try to keep it off the road for Winter to avoid the salt and rust. I run the Nitto Dura Grapplers that are the rib style highway tread and am seeing a little better mileage than most others with similar size vehicles and tow combo weights. It's 6.8 liter V-10 gasser and sees 8 to 9.5 MPG on highway towing trips at 65/68 MPH with a combined weight of 19,500 lbs. I feel that these super quiet LTs are part of that result, these are the quietest truck tire I have ever used, you just don't hear them. The tires are oversized at 305/70R18 (35.28"X12.8") being turned by 4.88 gears on a 4" lifted EX. My daily driver is a '94 Metro XFi, so that's helps to soften the blow of the fuel cost from the long towing trips.
Yup, need them. Thats pretty damn good mpg for towing that much with the V10.
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Old 07-20-2018, 10:02 PM   #5 (permalink)
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If I remember correctly once you get above about a 31 inch tire the weight increase for up sizing seems disproportionate for the size increase.
Thats something to look out for.
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Old 07-20-2018, 11:32 PM   #6 (permalink)
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New tire is 5# heavier than current one. I guess i will bite the bullet and go for it.
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Old 07-21-2018, 07:05 AM   #7 (permalink)
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What kind of miles/life are you seeing with this tire? (What is the CPM?).

I read a review on FourWheeler that made them sound nice (best of their kind), but the warranty is only 50k miles.

Versus a true highway tire the warranty above is half the life expectancy and a permanent 1.5-2.0/mpg penalty to the annual average.

In other words, that 10% off pavement is genuinely expensive. Where tire life is one-half (50k: $1,000) and fuel burn for those miles is penalized, it’s another $1,500 on top; or $2500.

At 370k I would be purchasing the third set of replacement tires with the way I use my similar truck. At 50k per set, it would be the seventh set.

Just in tires the spread is up to $4000.

Seems like a dedicated set of off-pavement is worth consideration. A set of takeoffs every so often.

.
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Old 07-21-2018, 09:54 AM   #8 (permalink)
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There's an awful lot to unpack here.

First, do you have a 1500 or a 2500? The 1500 took P type tires and the 2500 takes LT type tires. Neither of those came with 285's, so it is a larger than stock tire.

What tire pressure?

And what is going to happen I think depends on the truck's gearing. It's clear that the highway fuel consumption will go down, but the commute is another story. If you can keep your foot off the accelerator and not try to compensate for the slower acceleration that taller tire will give you, I think you can get better MPG's - but that urge will be hard to resist.
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Old 07-21-2018, 11:24 AM   #9 (permalink)
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Quote:
Originally Posted by slowmover View Post
What kind of miles/life are you seeing with this tire? (What is the CPM?).

I read a review on FourWheeler that made them sound nice (best of their kind), but the warranty is only 50k miles.

Versus a true highway tire the warranty above is half the life expectancy and a permanent 1.5-2.0/mpg penalty to the annual average.

In other words, that 10% off pavement is genuinely expensive. Where tire life is one-half (50k: $1,000) and fuel burn for those miles is penalized, it’s another $1,500 on top; or $2500.

At 370k I would be purchasing the third set of replacement tires with the way I use my similar truck. At 50k per set, it would be the seventh set.

Just in tires the spread is up to $4000.

Seems like a dedicated set of off-pavement is worth consideration. A set of takeoffs every so often.

.

They are up over 100k... go to pg 3 of this thread for pics...

https://www.cumminsforum.com/forum/t...er-report.html

My son thinks they have a lot of life left... I'm thinking they will get yanked on the next OCI (9k from now). No place to store a second set of tires/wheels so the dedicated set is a nogo. This is the 2nd set I've taken to 95k mi or more. Others got swapped out for various reasons, wear not being one of them.

Last edited by steve05ram360; 07-21-2018 at 11:35 AM..
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Old 07-21-2018, 11:34 AM   #10 (permalink)
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Quote:
Originally Posted by CapriRacer View Post
There's an awful lot to unpack here.

First, do you have a 1500 or a 2500? The 1500 took P type tires and the 2500 takes LT type tires. Neither of those came with 285's, so it is a larger than stock tire.

What tire pressure?

And what is going to happen I think depends on the truck's gearing. It's clear that the highway fuel consumption will go down, but the commute is another story. If you can keep your foot off the accelerator and not try to compensate for the slower acceleration that taller tire will give you, I think you can get better MPG's - but that urge will be hard to resist.
Truck is a 2500, tire pressures are at 52/50 F/R. Gearing is 3.73 with 33" on there now.

Your take is 180* from mine, I think the commute is going to suffer a bit with all the takeoff events that come with it. Currently the commute mpg is a tad bit better than straight hiway.

Back in 2014/15 I had Nitto TG's on there, 285-75-17's and was easily able to get into the 21-22 mpg range on the hiway. Wheels at the time were the heavier H2's that weighed 9# more vs the current OEM wheel (36# drop across 4 wheels). With the current tire, doing the math it looks like I've dropped 14# per corner, 9# wheel + 5# tire. I'd be gaining back the +5 from the taller tire.

Question still remains, what's going to happen coasting downhill with the heavier tire? Adds drag cause of the weight?

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