I own an '01 B2500 van with 5.2 and 4.10 rear end. The van has 152K on it. I have owned it for 6 months and put about 5K miles on it so far. It needs tires. The stock tire size is LT225/75X16. I get about 14-15 MPG in this van and it has plenty of power, but I would like to increase the MPG's. I do pull either a small 1,000# popup camper, or a 1,400# aluminum boat trailer on occasion. With either I don't even know they are behind me. My question for anyone out there is if I CAN think about getting larger tires mounted. I am thinking at least 235/75 or maybe 245/75 tires. The 245 tires would give me about 0.6 inches of increased height and would most certainly not be a problem for the wheel wells, as both front and back have lots of room. This is the jacked up B3500 frame under here.

If anyone can shed some light on going with a larger than stock tire on this setup I would certainly appreciate hearing from you. I hope to do some long distance traveling in the next few years, and if I can increase 1MPG on average it would be worth it.

 

I'm not really into tire mods, but just a heads up...with the larger tire you will be going faster than your speedometer will indicate.

 

my 03 1500 came stock with 245/75 16's. there is not much room left over.

upping the tire size wont increase the fuel economy.

 

I went from 235/75/15 to 30x9.5x15. A Minor size upgrade.

I Might be actually be travelling slightly further and faster than my Speedo/odometer indicated previously, but my mpgs took a hit, especially in my around town driving.

Highway MPG's are all about slowing down. Taller tires wont do it as it takes more torque to spin them.

 

thanks everyone all for the input... maybe my thinking is incorrect here, so please help me out... let me address each of the concerns above...

I went to a site that gave me tire circumference, based on 225 (stock size) and 235 or 245 tire sizes... this gave me the amount of distance that each tire would roll per revolution http://www.csgnetwork.com/tiresizescalc.html
225=92 inches
245= 97.6 inches
or I calculated this was about 6% longer distance using 245 tires over 225 stock tires for every revolution of the tire.
So I figured I might get 6% better MPG and my speedo would be off by 6% so I might be going 68.5 MPH when the speedo said 65 MPH

I know I am going to lose acceleration and a bit of towing capacity, but this B2500 is the 1 ton version with the B3500 frame (much more room around the tire wells than a B1500) and a 4.10 rear end according to the sticker on the door... I think that 4.10 rear end is really a high ratio... geared to pull big loads, which this van is capable of, but I won't be doing as long as I still own this vehicle.

NOTE- I used to own a '94 (new style) B250 and upped those tires from stock 215 to 235X15 tires... that change took up most of the wheel well and frt tires sometimes dragged on mud flap when turning and hitting a bump at the same time... my speedo was wrong, and I think I saw about 0.5 MPG increase, but the gearing on that van was much different then this one and I had the 5.9 and towed 1500# trailer all the time... Of course gas was much cheaper then and the MPG increase did not really matter to me

I know also I could change rear ends to something lower, but since I needed tires anyway I thought I could accomplish this same task by getting larger tires installed... and I am not up to changing rear ends these days... (just got off rotator cuff surgery 7 weeks ago)

So again I ask for your opinions... will going up to 245/75 OR 235/75x16 tires instead of stock 225/75 be asking for a lot of trouble? Or will it get me a little better MPG if I can live with a little speedo (to the low side) error and less off-the-line get up?

I do appreciate any comments, as I am trying to think this through before making a $1,000 tire investment for LT load range E (that three tire stores said I have to have on this vehicle).

thanks for the input!

 

I've always had 31 x 10.50-15's on my van and they did increase mpgs for me, I had my front lifted with spings by about two inches for clearence since the stock ones were kaput from the factory. The strange thing is, whenever I drive by one of those City Owned MPH trailers, my speedo always shows right on the money. I've also had my wife driving next to me to verify my speedo is correct. I've always wondered how that's possible. One other note, I don't use overdrive unless im one the freeway, and never when towing. Our habit here is when we get in our van we turn the overdrive off, that little tailshaft overdrive assembly costs one thousand dollars to rebuild, and the rest of the basically 727 is only 800.00, so I take it easy on mine as much as possible.

 

OK, let's first get things defined here ...

The Ram Van for your year came with a 3.92 rear. So, you are already ahead of the game for the rear ratio over a 4.10.

Next, drain our the rear OEM oil and replace with Redline synthetic 75W90 per the Chrysler TSB. This helps with wear life and MPG.

About the tires, size wise will NOT help all that much. BUT, upgrading the tires to a load "E" will. I had done the 225 to the 235. The tires actually got worse MPG and the towing rating got worse as well. The 235 side walls are not a strong as the 225 size. Also, the wider the tires, the more drag and friction of the van is transferred to the ground. A tire with XL rating or D rating for a Ram Van B200 using the B3500 HD frame actually needs the load "E" tire rating. Again, Chrysler has issued a TSB about this. This offers better handling, better sway control and better MPG. The stronger tire side wall does not bow much, thus the MPG gain is there. The tire I went with is the BFGoodrich Commercial T/A 225/75R15.

For better MPG, see my thread titled, MPG IMPROVEMENTS. Amazing that a 2001 B2500 HD suspension 8-lug wheels can hit 19.7MPG on a vacation trip down the interstate.
https://dodgeforum.com/forum/dodge-r...rovements.html

 

Tire diameter changes of less than 1 inch probably aren't going to make too much difference. 225/235/245, these are just load ratings. What Steve is talking about is stiff sidewalls and you get them when you move to LT tires. If I was towing or cared about gas milage I would definitely be using LT tires.

My Dodge van is a lightly loaded conversion van and all these LT tires do for me is make it ride like a bus and slide around in the rain. You have to select the right tire for the application.

 

Stev,

I appreciate your input and I have read your MPG Improvement thread... I published a reply on this thread a few weeks ago and asked you a question about the TBstuff you mentioned... asking for clarification. Perhaps you can comment?

"The Ram Van for your year came with a 3.92 rear. So, you are already ahead of the game"
as far as this comment, I believe you are wrong as the hood sticker indicates a DMF code 4.10 rear end DANA M60/24... this Dodge is extended with 8 lug wheels and a tow step bumper... so I WISH it had a 3.92 rear end... and it is stock with load range E, LT tires, with a GVWR of 7800# according to the Dodge door sticker. It sounds like you have the same van and I strive to get 19+MPG as you have done, but with my higher ratio rear end that might not be doable... HENCE the quest for larger circumference tires to offset this higher ratio rear end without having to swap diff gears!

Supradude,

I have that 31 size tire on a ’96 Tacoma. Those are not pumped up very high… recommended was only 28# on that light truck. With that pressure and the tread width, I like the traction. I use this truck to mainly haul 250 gallons (2100#) of water to my cistern and inground pool in the summer. I don’t have city water, so I have to depend on rain, or the local water vendor. I never travel far with this truck and MPG are not an issue.

blackvan,

I respectfully have to disagree with your assessment of 225/235/245 being load ranges... these numbers I believe represent tire sizes measured in mm of tread across the width with the /75 designation indicating that 75% of that width is in the side wall depth. Therefore increasing the width also increases the tire height (diameter). My van door sticker specifies LT tires at 65#/50# (rear/front) pressure, so I am not changing from P tires to LT tires. I am sticking with LT tires I currently as three different tire stores says that I have to with this weight van. My van actually handles fairly well with the stiff sidewalls.

The only problem that I can see is that the tires are worn fairly thin right down the middle, but have good side tread left. I attribute that to driving the van lightly loaded by the previous owner. Previously this was a work van for a painter, who carried paint and tools and occasionally towed a small trailer, but I doubt ever carried the weight that this van was designed to carry.

THis website http://www.csgnetwork.com/tiresizescalc.html pretty clearly spells out the relationship of tire size to circumference and diameter of various tire sizes. By using LT245 tires instead of LT225 tires, I will increase the circumference of the tire by 4% while also increasing the tread width.

Going through the numbers again…
225 size = 92 inches circumference STOCK tire size
235 size = 93.8 inches circumference or about 2% longer distance travelled per each tire revolution
245 size = 95.7 in circumference or about 4% longer per revolution of the tire… if I multiply a 4.10 ratio by 96% (the amount of revolution that a 245 tire will roll to go the same distance as a 225 size) then I get an effective rear ratio of 3.936…

Dismissing extra rolling resistance of the fatter tire, I am hoping to get UP TO 2% to 4% better MPG with these larger tires. BUT THEN AGAIN I am hoping my assumptions are correct and that is what I am asking for help with using this forum.

At this point I don’t think I can harm anything by going with the larger tire size. I just got off the freeway after attending the KY Derby this weekend, and the van will barely break out of OverDrive when traveling up long hills… only if I slowly accelerate will it drop down out of OD gear. It will usually stay at a steady 65 to 70 if I merely hold on the gas pedal. This tells me I have plenty of power at the rear wheels with the low ratio 4.10 rear end. Reducing this ratio by 2 to 4% probably will not harm a thing IMHO.

Since I am in the market for tires anyway, I think I will experiment with the larger tire size with only a slight increase in the cost of the tires. I am leaning toward Goodyear Silent Armor or Michelin LTX M+S.

Thanks everyone for the input…

 

I have always ran Goodyears because of the traction in the rain, since even cheap tires are decent when it's dry. I ran Goodyear MT's for years, excellent traction on the highway and averaged 18mpg on long trips to the desert towing my little box trailer with my camping gear and dirt bikes. I had Goodyear Silent Armors until just recently when some lame vandal decided to knife tires up and down our street. When I went to buy four new MT's, the cost was just too stiff. So this time I went with Falken Rocky Mountains, I am very pleased with the wet traction, the cost was 630.00 for all four for everything. I did my research and read nothing but great reviews on this newer tire. The cost was certainly the main factor though, otherwise I would have gone with Goodyeay MTs.