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Old 10-22-2015, 07:24 PM   #1
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Default Tires and axle ratios... what I learned about towing

Some time back, oh about 30,000 miles ago or so, I bought a nice set of Cooper 265/70 r70 LT tires for the F150. At the time I could not afford Michelins. I saved some money and got a slightly taller tire at 31.6 inches as opposed to the 30.1 inch 255/65 r17 factory originals.

The ride was a bit truckish, but this is a truck, these are truck tires, the load rating is 3100 pounds (up from 2200) and the highway MPG seem a little better.

Until it's time to tow the 5th wheel. After a few trips I begin to ponder what happened to my adequate tow vehicle which had become such a gutless wonder.

Much time and miles pass, and noting the wear on the Coopers, I begin to shop for tires and come across one of those tire size vs axle ratio calculators. Plugging in the numbers I feel sick. What was a 3.55 axle (adequate but not miraculous) was performing about 3.35.

Just from going from 30.1 to 31.6 inches. 1.5 inch taller. That's all.

What I learned about towing... You can build a truck for mileage, for comfort, daily driver. You can make a mudder truck with 3 feet of ground clearance and 36" rims. And you can compromise between any of these.

But if you are going to optimize for towing at or near your rated capacity, as in towing campers with 1/2 ton trucks, you have to optimize for towing alone and let the rest of it slide.

So in February my employer has promised a large profit sharing check. Last year was 2 months pay. This year is supposed to be bigger. So I'm going to do some stuff to the truck...

Cold air intake
Bigger exhaust
Deeper tranny pan (coolers are already installed)
Bilstein shocks
Switching to 3.73 gears

and back to the 255/65 r70 Michelins that came on it in the first place. The ride and towing should both improve.

I learn slow sometimes, but I learn.

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Old 10-22-2015, 09:50 PM   #2
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Many years (decades) ago, when I was in college, I was the proud owner of a 1957 Pontiac. I replaced the original-size tires (whatever they were) with bigger ones and thought I was hot stuff. No one told me that this would make the speedometer read low. The speeding ticket cost me more than the tires did.

Perhaps your pickup didn't get quite so gutless as you thought it did. Maybe the speedometer was just reading low.

If you change to a lower rear end, you may need to do something to the speedometer too; and maybe not, since many modern vehicles read the actual tire RPM for vehicle speed.
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Old 10-24-2015, 11:13 AM   #3
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Your first mistake is F-150 for an F-250 or 350 job. But yes.. You need to optimize for towing.

Also LT (light truck) tires might not be the best choice pulling a 5ER, at least not on the rear.
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Old 10-24-2015, 11:38 AM   #4
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Quote:
Originally Posted by wa8yxm View Post
Also LT (light truck) tires might not be the best choice pulling a 5ER, at least not on the rear.
Why? Not saying it isn't so, just that I don't know enough to know why.
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Old 10-24-2015, 06:53 PM   #5
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Your first mistake is F-150 for an F-250 or 350 job. But yes.. You need to optimize for towing.
Yeah a bigger truck would be nice. The truck is adequate for this particular 5ver at only 7800 pounds per the scale. At least it used to be before I screwed with the tires. I would have gotten an F-250 but unfortunately I have an F-150 budget. A few tweeks and it will be better than new.

Quote:
Originally Posted by wa8yxm View Post
Also LT (light truck) tires might not be the best choice pulling a 5ER, at least not on the rear.
If not light truck tires, as it is a light truck, then what would you suggest, as I obviously know nothing about tires.

This is the next generation of what came on the truck from the factory and what I am considering returning to:
http://www.michelinman.com/US/en/tir...r-ltx-m-s.html
http://www.walmart.com/ip/Michelin-D...-110T/46425595

They have a 2337 pound load rating.
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Old 10-25-2015, 12:57 PM   #6
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The larger diameter tire has a large circumference which means for each revolution of the wheel it will travel farther. The larger diameter tire is basically changing you final drive ratio to a lower numerically (higher) drive ratio and it is now geared for lower RPMs at the engine and better fuel economy. If you go to a larger diameter tire, yo need to change to a lower ratio (Higher numerical ratio).

If you had a original truck rear axle ratio of say 3.42, the larger diameter tires would go toward a 3.08 ratio.

This is why I tell people that are towing and RV to not bother putting on larger diameter tires. It may look "cool" or whatever, but it is not the thing to do to help towing performance.

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Old 10-26-2015, 07:41 PM   #7
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Default michelin LTX

I have used the LTX M/S version of tires on my last 3 tow vehicles.
Very satisfied, but pricey.
As the saying goes, you get what you pay for.

PS- first full size (1500) truck had a 3.42 rear end. Got great gas mileage, but I actually had to trade up to a 2500 to pull the trailer i bought to replace the popup.

Now that I'm pulling a 9900 lb 5er, I definitely want the best tires I can afford.

Thankfully Chevy made the 2014 2500's to have a 6 speed AT and a 4.rear end, which helps.
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Old 10-26-2015, 07:53 PM   #8
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Quote:
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Thankfully Chevy made the 2014 2500's to have a 6 speed AT and a 4.rear end, which helps.
Yeah the newest F-150, if properly equipped, can drag your house down the street. However, the current truck has the no-payment option, which I like. And the new ones are over-priced and ugly.

With the reversion back to the right tires and the gear swap up to 3.73 the tow rating goes from 8600 to 9500 or so. The trailer per the CAT scales is 7800 pounds.

It'll pull better, ride better, make more noise and the payment plan doesn't change!

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Old 11-02-2015, 06:42 PM   #9
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Yes, the gear swap will change the tow rating according to the tow charts, but, what about the wheel bearings, can they take it? And the brakes?
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Old 11-03-2015, 02:55 PM   #10
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Yes, the gear swap will change the tow rating according to the tow charts, but, what about the wheel bearings, can they take it? And the brakes?
In short, yes and yes.

The truck was available from the factory with either a 3.55 or a 3.73 axle. In both cases the brakes, springs, bearings, shocks and everything else were identical.

And since I am not changing trailers, the loaded weight remains 7800 pounds (at the scale) while 5th wheel tow capacity increases from 8600 to 9500.

Pin stays at 900 pounds.
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Old 11-09-2015, 01:40 PM   #11
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Hello Wade & Friends,

My first post here, so, First let me thank-you for operating this website for Ham radio & RV for 8 years!

Tow Vehicle Weight, Truck Size , Tire Sizes and Rear End Gear Ratios are always a trade-off with Transmission Gearing, Gas Mileage & Power.

The F250 would pull much easier, but I'd bet a loss of 3-6mpg would occur vs. the F150, in most cases. I am going to sell my 2006 F250 soon, and downsize to a Tacoma size pickup. But, we are only towing an Eggcamper (2000# empty). The best highway mpg on the F250 is 15.

My F250, and some F150's have a Tow setting for the transmission, which should, somewhat, make up for the taller tires by automatically shifting to a lower gear when needed. That makes the effective axle ratio when using tires of a different size, less of a factor.

We towed the Egg with our 4 cyl. Subaru Outback and you wouldn't be wrong to say it was kind of "gutless". But it did the job from Massachusetts to Florida and Texas and back just fine. Got only about 17 towing, while 30+ without the camper. The F250 gets about 10-12 towing the Egg.

While Gas is fairly low right now, it could go past $4 a gallon at any time. So, I don't mind putting up with a little bit of "gutless" in order to go where we want to and save on gas expense.

There are 2 advantages to larger tires, first is (usually) not having to replace them as often, and second, stability is usually just be a bit better also. Maybe the solution for you is to buy a larger, that is, wider, tire, but not a higher nor a lower height tire. If I am regularly carrying some weight in any vehicle, I like to go up just one size in tires if possible, and again, not usually much taller, but a bit wider.

We monitor 146.520 FM and 144.200 usb while traveling and use a Kenwood TS2000. I have hooked up an HF antenna at times, but don't have one on any of our vehicles right now.

I hope we can get to the Orlando, FL, Hamcation again next Feb., as we have for the last few years. The Florida Weak Signal Society has a meeting there and a bunch of the members have tables in the tailgate area, and that is where we usually meet-up. Look for Down East Microwave and you can find us, and stop by for an eyeball.

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Old 11-09-2015, 06:02 PM   #12
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Mark,

Welcome aboard! Unlike some forums we actually like new folks. Jump in and join the fun...
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Old 12-05-2015, 08:32 PM   #13
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Digging up this tired thread...

OK, want to go back to the OEM sized tire so I can get my OEM axle performance back, just before I kick it up to 1:3.83 (from 1:3.55)

And I'd really like to have a load range E tire, except that, wait for it... wait... wait...
nobody makes a load range E tire in 255/65r17 the size which comes standard on most 1/2 tons with 17" rims.

Dang it. Now I have to figure out what size "E" tire is closest to the same diameter as the 30.1" OEM tires I used to have.

So after several days of asking questions at my favorite tire store (where the 75 year old owner is a friend of mine but tends to be a bit old school) and doing research online I figure out the closest diameter is a 245/70r17 that comes in a service range of 119/116 and is a load range "E" tire. Unless you ask "Mr. Old-School-Tire-Guy" who swears it's not a real "E" unless it's a 10 ply tire.

The OEM 255/70r17 is 30.1" tall and the 245/70r17 is 30.5. This changes the axle from 3.55 to 3.50. I can deal with it. And the tire is rated at 3000 pounds. And doesn't have 10 plies therefore it rides sort of nice, to be a truck tire.

So after much fumbling around, the winner is: Michelin LTX M/S2 245/70r17 119/116 rE

http://www.tirerack.com/tires/tires....S2V2&tab=Specs

Now the only problem is getting a tire that seems to be made entirely of unobtainium. Calls to the Michelin distributor indicate they don't have them in stock, might not even have heard of them, and don't have an idea when they will have an idea until after January 1st.

Cooper, Firestone and Bridgestone all make a competing tire, and cheaper, too. But noisier, rougher riding and warranty at only 50K not 70K.

Fortunately I have time (and some tread) left. I'll go with Cooper if I need to. But at least I know there are tires out there that will do the job I want them to do. When I started looking I didn't think I could get a usable (right diameter) "E" tire for my F150.

All I have to do now is wait.
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Old 12-06-2015, 08:02 AM   #14
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Quote:
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... Cooper, Firestone and Bridgestone all make a competing tire, and cheaper, too. But noisier, rougher riding and warranty at only 50K not 70K.

Fortunately I have time (and some tread) ... All I have to do now is wait.
Waiting isn't so bad -- January isn't far off.

Nowadays, and for the last 30 years or so, I spend a little more and wait as long as necessary for Michelin tires. Why is that? It's because I have had premature tire failures with every other brand I ever bought. Every other brand. But, in the thirty years I've used Michelin exclusively, not one tire has failed. Not one. No tread separations, no blowouts, no leakers, no nuthin.

Once, in my foolish youth (1965 or so), I bought five new Firestone Wide Ovals for an Olds convertible. Within months, every one of them, and four warranty replacements, failed with tread separations. Good old Firestone! Lucky I never crashed. Finally I smartened up, bought another brand, and had no more problems. Expensive lesson! I wouldn't drive across the parking lot on a blankety-blank Firestone tire.

I've had wheels fail, valves leak, all sorts of things in that time -- a very-hard-to-find crack in a Corvette wheel was a really difficult leak to diagnose -- but no Michelin tire, itself, has ever given me a surprise.

I buy'em at Discount Tire, sizes that they carry anyway, and have been totally pleased with their service everywhere (in the Western USA they're called American Tire). Any of their stores, anywhere in the country, can look up every tire I ever bought from them, and smilingly give me the free rotation and balance when it's due. Free repair if I pick up a nail. And like that. They know how to keep my business.

Alas, Discount Tire doesn't carry my 225/80R22.5 motor home tires.
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Old 12-06-2015, 10:16 PM   #15
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Default Michelin tires

I too have jumped on the Michelin LTX M/S bandwagon.

Just excellent tires, and always good service from Discount Tires (maybe when they see the large volume I have bought in the last 5 years they know I'm a good customer).

There are other good tires out there, I just like The LTX series.
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