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

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.

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.

Yup, need them. Thats pretty damn good mpg for towing that much with the V10.

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.

New tire is 5# heavier than current one. I guess i will bite the bullet and go for it.

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.

.

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.

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.

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?

Well the time is here, I will be finding out the impact of 5# rotational mass added to the tire. 110k on the tires, 380k on the truck. Going to be looking at downhill coasting as well as takeoff & uphill loads. My expectation is takeoff & uphill are going to hurt mpg while steady state throttle on flats or downhill it may improve.

My experience on a regular passenger car is rather negative, even when using "eco / aero" wheels that, unfortunately, were also a lot heavier.

Looking fwd to your results

I think that's my next tire purchase for the 3500.
I have 3 sets of rims. Dedicated studded snows on steelies, some Michelin highway tires on the 2012 light aluminum wheels, and a worn set on the 2012's to change out.

What did you ever end up with after tuning for mpg? Its been a while but last time we talked you were just diving into efi iirc... I have my tune dialed in pretty good now where it seemingly runs the same from 60-100*... Going to work next on the baro correction table for rail pressure. 23.3* is my best.

I most often use the truck for towing the 5th wheel. My best highway runs to Portland and back were in the mid-24s, but I have the 3.42 gear set also. typical mixed use commute is in the ~19s, mixed meaning stop and go for part of it in Seattle :(
Towing the trailer MPG is very much trip dependent. Mountains are going to get me 12, a run down I-5, 15-ish.
My DD is still the beetle in the mid 40s combined with the train and my bike.

Tires done, added weight of new tires very noticeable (expected), coasting down the same hill as this morning... Before, speed maintained, after, speed drop by 1.5 mph accordi g to what i see on the gps.

Readjusting speedo, will see how it does next week. Before the swap, 22.4 mpg

I'm thinking 275/70 for my truck with the tall gears I have.

OK, here is what I know... before with the old tires, 285-70-17's, worn but still had tread left (can post pics if needed), I was able to coast down all of the "flatter hills" between Tacoma & Tukwilla on I5 with a 2~3 mph drop in speeds. Now with the new tire, 285-75-17's, there is no way. Even the steeper drops have lost a noticeable amount of coasting capabilities. Being that the tires are new, heavier (5# comparing new old size tire to new tire according to my son who works at the shop and had access to the #'s) and taller (by 1", same width). The new tires have a noticeable increase in grip (also expected) but to me feel like they are better suited for snowy conditions. The rubber is pretty grippy and I already see a good sized drop in the number of miles driven vs what the fuel gauge says (speedometer corrected). FWIW to anyone, I will post mpg #'s for this tank at the end of the week, last tank was 22.4 mpg.

I did see an approx 75~85 rpm drop from the bump in size. Also, tune needs to be tweeked... Not mentioned on this forum but when I did the driveshaft swap I had to adjust the timing to get the turbo spooled back down around 1000~1100 rpms. Now with the tire swap, I will need to re-tweek it again as I now have some timing rattle (mpg killer) in certain area's of the tune.


Look for a weight reduction from your current tire. I think your problem with the lower mpg on the Seattle trip is the hill climbs. Next time you take that trip, pop it in neutral on all the down hill area's on I5 (if you dont take I5, take it) and report back how well it did on the downslopes... Our trucks are near identical so you should be able to coast down most of them with minimal drop in speed.

Also, did you do an aluminum DS? If not, do it... its worth it.

Tires do take some time to break-in. One tons, especially among civilian vehicles.

On a Ckass 8, more than 10,000-miles before squirm stops. Break-in continues for about 40k.

5-7k is my expectation on my TurboDiesel.

Update + question...
These tires have a 2 ply sidewall, 75 series tire, new to the market. Any issue running this tire with a heavy load? It is a 10 ply E rated tire. The alternate has a 3 ply sidewall.

Rolling resistance has dropped quite a bit, mpg appears to be making a comeback, 420+ miles on them. Still squirrelly .

I'd get a commuter car, unless you're commuting to a construction site.

Might consider getting dedicated highway tires on some cheapo wheels and swap between traction/efficiency. That would get old real fast if you needed to do that often though.

WHAT???? what kinda talk is that? lol Getting into the 23's was awesome, 22 all winter would also be awesome. That is my current goal, to keep mpg's up there. If my truck was getting the mid teens... then yeah I'd get a commuter.

It's not just the cost of fuel, it's also the ongoing maintenance of everything else that needs attention due to putting miles on the chassis. When I bought my 1998.5 from DOT auction, I requested and received the full service history, which was nearly a ream of paper.

When do (quality) cars need front end rebuilds, U-joint greasing, $1000+ tire replacements, 12 quart oil changes, fuel filter changes, etc, etc.

Whenever I spend a lot of time in my sedan, it feels neat to be up high looking over traffic in the truck... and whenever I spend a lot of time in the truck, it feels neat to be down low in what feels like my sports sedan.

I'm saying that long distance commuting in a truck and asking about truck tires (still don't know if that's what you're doing, just sayin') is like asking how to better hammer nails with a shovel. It's worthwhile learning how best to hammer nails with a shovel if you're determined to do so, but it's not the prudent way to do the job.

If you're a single guy, then I get the appeal of a truck. Especially bench seats ;)

Its not the cost... its the challenge of it all and what I learn from it... If it were all about $, I would not keep it.

It's 10 ply Load range E. I would not hesitate to load it up, if aired up properly.

“Plies” became a meaningless term several decades ago as to load rating. Same for several other designators.

“Load Index” is what to check.

An LR-E tire is about 121 on LI scale.

If the Load Index is right, then construction isn’t a concern per se

DESCRIPTION of service is how I’d concern myself. A tire with open shoulders and widely-spaced tread blocks won’t be ideal for highway service. Not enough tread to spread the heat, so to speak. The total amount of tread versus a proper highway tire is reduced. Greater stresses over a comparable area.

This is before handling or braking. Just rolling along at speed.

Under load, increase it again.

But let’s use perspective. First off, there is no such thing as a pickup safe to drive above 65-mph. That’s already a real stretch from speeds where rollover tendencies can be dealt with. Only fools drink moonshine and fumble with firearms.

A truck crippled for highway work by off-road tires should be even slower. Work with vehicle spec, not against it.

If the dummies whose selfishness denies the above had any working knowledge about personal vehicle travel (Average MPH) they’d likely be more reasonable. A trip somewhere has many aspects. A plan that works all pieces is the successful one.

Meaning, it’s more than cruise control set speed.

Drive as if tires won’t ever again be available. And it’s THIS pickup that has to someday get family to safety.

Improve the suspension & steering. Super Steer Rear Panhard Rod, plus smallest Helwig rear anti-roll bar (and upsize front smallest amount with same brand is necessary). Better than entry-level shock absorbers.

Zero steering play. So long as ANY is present your truck will always be “off”. Tire design only adds to that problem. It’s not the same any day as any other, and it never a constant. It’s a changing variable.

If you drove my 2WD you’d see. You’ve driven cars that had worse steering/handling. As you’re familiar with the man trans, what you can then do widens the envelope.

It’d be an eye-opener to you how fast my overhead MPG readout climbs into the low thirties and stays there on level terrain after a reset. I know the correction factor, and it isn’t much. Can stay right there when all other conditions are favorable.

Can you reach over to backseat while underway to pour coffee? Truck doesn’t wander away from lane center? That’s not a huge exaggeration, given how bad some Dodge 4WD trucks are to be found.


.

How bad are 4WD pickups?

My 13’ tall, 20,400-lb 579 Peterbilt semi tractor (13L Paccar with 10-speed Eaton AMT UltraShift) can hit in high 13’s to low 14-mpg while bobtail at 64-mph. Very first test I gave it.

I can let go of the steering wheel for extended periods (where periods can be fractions of seconds). Even several seconds. A vehicle that on a three-count is headed into the ditch is dangerous.

You’d (anyone) best believe that tire design, pressure and no-fault steering are huge contributors to MPG

You've already received some replies that are ….. uh ….. let's say "a bit off the mark."

Since different materials can be used to make tires, the number of plies is irrelevant. So much so that the old way of defining things (Ply Rating: 8 PR, 10 PR, etc.) was replaced long ago (in the 1960's!) by Load Range (LR D, LR E, etc.). And then the Europeans came up with Load Index (117, 121, etc.) - except they still like to use PR!, which confuses things further, since LI varies with size.

You are using a larger than stock tire (more load carrying capacity), but at a lower inflation pressure (less load carrying capacity), so the answer to your question is "Probably OK!"

Yeah the concern is the sidewall flex. It stinks. If I stick with this size, going to go over to the Toyo Open Country AT2, 3 ply sidewall. If not, going back to a 70 series tire. These tires are not fun under hard braking and I often get the feeling of driving a boat behind another boat & crossing a wake. Weird feeling.

MPG wise it also is not that great... took an approx 2 mpg hit. The 5+ # per tire takes its toll on the hills on the front side. The back side does not offer enough coasting speed to make up for the front side loss.

As I mentioned earlier (I think) the last time I ran this size tire with crappy programming I was getting 21~22 all day long on the hiway. Not seeing that with this one and I feel the tread is sticky more so than the other tire for its 3 peak snow rating.

A winter time goal was to keep the mpg up there in the ~22 mpg range regardless of temps. Looking at adding a secondary fuel heater with some sort of automated control to get temps up into the 85~90ish range. Additionally, the oil filter heater on cold starts only with the goal to get oil temps up faster & reduce the overall warmup time. Commute is 30ish miles in the morning. I still have some aero mods to play with that I did not get to over the summer.

Update: Rolling resistance has dropped to a point where I can now coast down most if not all of those flatter hills. MPG still in the 20~21 mpg range, going to go after the tune this weekend and attempt to get it dialed in for the added load. Where I believe the issue is, is in the uphill climbs, the added 5# of rotational mass & the slight gear change with the 1" taller tire has big enough effect on throttle response to cause the drop in mpg.

These tires are still coming off in the coming weeks...

Tire swap comes to an end. Swapped back in the Toyo Open Country AT2's this morning, did the math and thought I'd share the results. Take if for what its worth, 100% eco = best effort, DGAS tank = "Dont give a smores" tank

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 2806.6 142.835 19.64924563 <-Average

Coasting significantly improved, even on brand new tires, I expect average will jump back up into the upper 21's, low 22's.

I will update this post after 6 more tanks...

Edit:
Toyos...
11/15/2018 461.0 miles 22.158 gal 20.805 mpg Fresh tires, 100% eco
11/17/2018 570.3 miles 27.924 gal 20.416 mpg 100% eco drive, 1 round trip work plus Tacoma-Boise miles
11/19/2018 321.7 miles 18.706 gal 17.197 mpg DGAS tank, lots of off road and steeper dirt road hill climbs, 4000' elev change
11/20/2018 338.7 miles 16.793 gal 20.169 mpg DGAS tank, more off road & another 4000' climb.