Tire Sizes

[mohok]

Currently running LT265/75/16E Mich M/S. Dodge recommended LT245/75/16E. Poor fuel mileage towing 8000lb Tag Along Travel Trailer. How much in safety am I giving up if I go to LT235/85/16E A/T in hopes of improving fuel MPHs? 2001 Ram 2500HD Diesel 4sp A/T. Have done the Banks Power Pack deal and A/B Cold Air Filter with no increase in MPHs.

[flagmanruss]

OK, first off I think you have a typo. I presume you mean MPG, not MPH. Your "overhead" console MPG is estimated for stock gear ratio & tire sizes. On my STOCK (signature) truck it is right on. Guys who change tire sizes or gear ratios often have a correction that can be appied to a programmer box. The overhead will not read right. You'll see notations that MPGs are "hand-calculated" & that is why.

The CTD has plenty of power, even as stock. A programmer can improve it some (if you keep your foot out of it) & have it set for best mileage.

Now as to changing the tire size, a 245 is a smaller (shorter tire, smaller circumfrence) will turn more RPMs to go the same distance. It would give the effect of a slightly lower gear ratio. That is going the wrong way, you need a taller tire (larger circumfrence) to go further per rovolution. HOWEVER, the overhead will not recogonize the change in tire size, although you will physically be going further. You could figure out the correction mathmetically and then do the MPG math.

You don't state your gear ratio or the MPGs you are getting. It's helpful if you describe your truck in the signature space under "my profile".

Before the days of electronic speedometers, we used to change the speedometer drive gears in the tranny... gosh do I feel old. I last did that on an 84 GMC that came with 3.08 ratio... horrible to drive... my buddy put in the most reduction we could put in that housing. 3.55 I think.

Russ

[mohok]

My primary concern in switching to the 235/85 vice the 265/75 is saferty. I understand that I will lose 33mm/1 1/2 " of surfacecontact. I tow my 8K Pull Behind Travel Trailer 3/5K miles annually primarily on Interstates. Also, I can bring 4 Yokohama 285's for less than $500 and it would cost me $900 plus to replace with 265 Michelan's. ThanksMohok

[flagmanruss]

Sorry,I missed the switch to 85 series. I don't know if the smaller tire in the taller profile would have a larger or smaller circumfrence. I don't have the load ratings of these tires available... A more aggressive tread pattern may cost you some on the MPG because of increased rolling resistance.

[dorkweed]

I'd say go with the LT235 85/16E's........they're rated for the same weight carrying as the others. I really don't think you'll notice much, if any, difference in ride or handling.All that said, I wish there was a tall, narrow tire available in 17" for my 3rd gen. I like the "pizza cutter" look versus the "wide tire out past the fender look"!!!! The narrow tires are better in snow and mud also!!

[Mopar1973Man]

LOL I've got the 235/85 R16 on mine now and pulling 25.2 MPG on my last trip to Stanley, ID... Skinny tire do perform just fine for highway use and tend to be just a bit slick in the gravel but if you keep a level head you can do just fine...

[guesswho512]

on my ranger i run larger tires than factory specs2 benefits: more ground clearance and less miles on odometer

[Dave3500]

I have a set of Firestone on mine LT215/85R 16 that do just fine for me. Except when I was pulling my Jet Ski's out of the lake, couldn't get over the slick sea weed from the previous nights storm & slid into the dock hit a nail that was sticking out & sliced the tire causing a slow leak. I had trouble trying to find another used one to use as a spare. Tire guys said it was an oddball size, true?My milege is better than a 4 cyl. 5 speed 1989 Dodge Dakota that I was using as a full time driver. Bought it almost new. I had to downshift that thing on every hill almost. Best I ever got on that was on a trip out West, like 25.Dave

[flagmanruss]

I an unhappy with the current trend to lower profile tires, even on trucks! In my experience, these lower profiles have crossed a line. Originally for high performance cars... now they are offered in the extreme. In my family vehicles, these lower profiles are IMHO more susceptible to impact damage... even on a light auto. The slight increase in sidewall height on truck tires can do no harm, so long as they can support the weight. I agree that narrower profile can be superior under certain circumstances... like in snow.Russ

[Mopar1973Man]

For over 15 years I ran 235/85 R16 on my old 72 Power Wagon Dpdge in winter time ice and snow with no problem. Now with the diesel its a different story... I tend to have to be light on the throttle to keep it from slipping in the gravel... But come winter I can control TQ with the Edge Comp but selecting a lower sublevel...

[Dave3500]

I an unhappy with the current trend to lower profile tires, even on trucks! In my experience, these lower profiles have crossed a line. Originally for high performance cars... now they are offered in the extreme. In my family vehicles, these lower profiles are IMHO more susceptible to impact damage... even on a light auto. The slight increase in sidewall height on truck tires can do no harm, so long as they can support the weight. I agree that narrower profile can be superior under certain circumstances... like in snow. Russ

Yep, I hear you Russ. Man guys are running wagon wheel tires, skinny rubber, one has to look for the tire. man, the pot holes in the roads we get around here. My Bro-in-law, had his wife switch his bank because he didn't want to drive his new truck on the road the bank was on. LOL True! The bigger sidewall just needs more tire shine? B) Dave

[keydl]

The 215's were stock for tonners 20 years ago, they replaced 7.50's and 7.00 15. 17.5 and 19.5 were also shipped.A lot of duals will space with 235's with out spacers to keep the tires from kissing when loaded.I have run all 3 - 245, 235, and 265 on the stock 93 steel wheels and the only difference is that the 235's sink in sand as bad as the old iron with 7.50 16 and 8.00 17.5's.The 235's and 265's are very close in diameterkeydl

[Dave3500]

The 215's were stock for tonners 20 years ago, they replaced 7.50's and 7.00 15. 17.5 and 19.5 were also shipped. A lot of duals will space with 235's with out spacers to keep the tires from kissing when loaded. I have run all 3 - 245, 235, and 265 on the stock 93 steel wheels and the only difference is that the 235's sink in sand as bad as the old iron with 7.50 16 and 8.00 17.5's. The 235's and 265's are very close in diameter keydl

Thanks Keydl! So the wider tires displace the weight better in the sand, is that it? I'm going to have to look to see what came stock on my 3500 in 98. Even my spare was a 215 Michelin. :confused:

[keydl]

My '50 Chev came with 7.00 18 tires on 2 piece wheels, the '60 Dodge was 8.00 19.5's, the '69 Ford wore 7.50 16's, the '78 Ford had 7.50 16's and the '84 GMC was on 215x86R16 - all 1 ton. The '93 Dodge is a 3/4 and built the same as all but the '50 and is the first that does not carry carpet pieces to get out of sand with the 245 and 265 width tires, by the same token the 235 width with siping will bite ice well. I prefer siping over studs.keydl

[Dave3500]

Hey Keydl,What a fast assortment of tonners, as you call them. Two of everything! So the 93 your first diesel. Many folks like that 90-93 12v, saying that is the best of the best. You've got a keeper in that one. I've got to check your sig to see if it's stick & what style cab.Yep, ice is a pain in the neck. I usually don't drive mine in the snow if I can help it. Only a few times last year, to get hay or something that was it. A friend of mine gave me a 94 civic just to get it out of his driveway after he bought a new vehicle. Wasn't running, needs a battery & maybe an alternator.Thanks for the tire lesson! :thumbsup

[keydl]

Uh, hadn't thought that way - 2 GM, 2 Ford and 2 Dodges. Not the first light diesel, that was the Isuzu and there were 5 heavy and MD before I quit touristing.I think the best way to size tires would be pounds per square inch on the ground, dry sugar sand will support about the same as mud and the other end is concrete pavement. Tire life generaly improves with less pressure per square inch but wind and heat increase,spending a little for wider will improve the number of miles at the cost of a little fuel. 40k on 7.50 16's v 75k on 8.00 19.5's when they were the standard, 265's seem the 10 year ago standard for shipping 10k capacity trucks with 235's as an alternative. Talking to the fellow that I buy tires from - going to 265 from 235 would cost $30 and maybe 5 gallons of fuel over 80k miles v the 60k miles from the 235's. And the 265's will save a lot of effort getting out of the field 3-4 times a year when it is dry. If you don't leave the hard and the ice and slush are a factor, skinny may be better.Tread design for the highway, my preference is 5 rib with venting to clear water and tread blocks 3/8's wide along the ribs. Tread blocks tilt under change in speed to bite ice and snowpac or wipe water away. They also flex when rolling to cool the tread.The Dodge is a club cab w/autoYour little Honda will make an excellent commuter. My daughters Honda would quit running because of the ground connection on the rocker cover, check the Honda forums on yours.keydl

[Dave3500]

Hi again Keydl,Thanks for the tire lesson. We only had 4 days of 90 degree temps here this summer, so heat is not really an issue in NE Ohio.I'll keep all your info in mind when I buy tires next time. I'll see how much I have to use her this winter. Last year there was salt on the roads here from Thanksgiving to March. Some reprieve in December but not much. If I drove it more I'd would consider those BFGoodrich T/A's for the rears. Had a 76 Dodge 150 that was a daily driver that I never really had any trouble w/ getting stuck even empty.Quite an array of light diesel trucks. Do you run any WVO or biodiesel in any of them. A guy from the Cocoa Beach area gave me a WVO blend formulation that I had some luck w/ running in a 6.9 van. Was sort of based on the diesel secret scam that is going around, especially when the price was up over 4 bucks a gallon.I'm not a stranger to Honda cars & ATV's. I've had plenty. Accord, Prelude, (Wife's summer car) my third Civic, del Sol, (my summer car) Vtec coupe, & now this hatchback VX. I had the coupe parked in the drivway & a teenage kid came up a offered his 71,000 mile Miata for my 185,000 mile Civic. My wife said to do it, so........ Sitting in back garage waiting for paint. resto project! Some rust but mostly dents, dings, new clutch, rear shocks, crack in rear bumper, factory style wing, new top & some door seals. Fun, fun!Still my most favorite vehicle is my Dodge Cummins. I love the seat of the pants feel from my stock truck. I can't imagine what a hopped up one of these would do. If I came into some money, Trans upgrade, Veggie Fass pump, ss twice pipes, new IP, BD steering brace & a repaint. Clear coat popping off in places. I admire the dually fat fender look, looks hot rod to me w/ those deep dish syms. ;) Dave