Questions on towing with a lifted truck

milo wrote:

mudfuel07 wrote:

milo wrote:
Quote... what the purpose of lifting a truck is. :h

Looks cool having to put a 4' ladder out for the wife so she can get in & out of the truck. :C

You must not like your wife!!:h For me, it means I get a little action helping her up and down--it's a nice side benefit!

Hmmmmmm... Why would I not like my wife if you have to put a ladder out to get your wife out of your truck. :h Guess for you that kinda action is better than no action at all huh......LMAO

Wow, you're old and using teenage slang. Good comeback. It was meant as a joke, but it must have gone above your head.

mudfuel07 wrote:

milo wrote:
Quote... what the purpose of lifting a truck is. :h

Looks cool having to put a 4' ladder out for the wife so she can get in & out of the truck. :C

You must not like your wife!!:h For me, it means I get a little action helping her up and down--it's a nice side benefit!

Hmmmmmm... Why would I not like my wife if you have to put a ladder out to get your wife out of your truck. :h Guess for you that kinda action is better than no action at all huh......LMAO

My 1996 8.6K GVWR TV with over sized tires can still go into parking garages
that many of the +7K GVWR half ton TV's CAN NOT enter because the OEMs understand
how their buyers want taller trucks with the same ratings of older, but same GVWR's

milo wrote:
Quote... what the purpose of lifting a truck is. :h

Looks cool having to put a 4' ladder out for the wife so she can get in & out of the truck. :C

You must not like your wife!!:h For me, it means I get a little action helping her up and down--it's a nice side benefit!

Quote... what the purpose of lifting a truck is. :h

Looks cool having to put a 4' ladder out for the wife so she can get in & out of the truck. :C

Wow! Lift it and enjoy it. The height you're going to will make little difference. I assume that you are putting on a quality kit, so there shouldn't be a problem. My current truck is the first non-lifted truck that I have towed with and I have never experienced a bad tow from mild 3" lift to a 8" lift. As long as you, the driver, takes into account everything, you'll be good. A 4" on a GM isn't that much. I'm in the camp that if it makes you happy, that's all that matters!

The most accurate for tire vs diff ratio is to use the tires "rev's per mile"

Even if the tuner asks for the tire dia...there is a look up table that it then
converts to "rev's per mile"...as the ECU counts the number of rev's over a time
frame to determine the speed

From stock GM tires (about 31") to 35" you are looking at about a 11% overdrive from stock gearing. If you are close to your towing limits, this may make a difference. My Ford came with tires ranging 31-33" tall. When I bought it, I had the shorter tires and went to the taller ones after they wore. Although My tow rating did not change, I could tell the difference in the shift points when I towed my 11K+ lb trailer through the mountains. Where I was holding a particular gear, the 6% overdrive now had the transmission downshift one gear lower. I did see a slight rise in unloaded highway mileage with the taller tires, but towing was the same. In my case, the change to a slightly taller tire was not detrimental to mileage but it did make the engine and transmission work more.

Ummm...OK...I see that math was not your strongest subject. Let me see if I can clarify.

majorgator wrote:
You referred to the tire WIDTH and referenced that as the tire HEIGHT. The second number in this method of tire sizing gives reference to the height. I never said anything about gear changes.

You are correct, the 245, 265, 285, etc, refer to the width of the tire in millimeters. The second number, the "75", is the aspect ratio, which is the ratio of height to width. So, if you increase the width and keep the aspect ratio the same, the diameter of the tire will increase too. Sorry if I wasn't clear on that.

majorgator wrote:
The calculator you linked to is not accurate. It depends on linear data input and provides linear data outputs. As stock tire size increases, the calculator becomes less accurate, because overall diameter increases become less of a factor. If you increase the diameter of a compact car tire by 2", then you've made a huge change. But when you increase a large heavy duty tire diameter by 2", you've created an almost negligible impact. A straight-line calculator cannot deal with this.

The calculator that I linked to is 100% accurate. You are correct that it is linear, because geometry is linear. If you increase the diameter of a tire by 2" it will have the exact same effect on the gear ratio on any vehicle, whether it is a large truck or a mini cooper. It would be a smaller % change on the large truck, but the numerical change is the same.

majorgator wrote:
Don't be so quick to justify yourself that you fail to read.

I don't need to justify myself, it's just math is all. Sorry if you don't get it.

The FACT is, you reduced your towing power with those taller tires on your truck...but if you are satisfied with how it drives, that's all that matters...it's your truck not mine.

I only posted this info so that the OP could take this into account when lifting the truck he uses to tow a 35' trailer.

BurbMan wrote:

majorgator wrote:

BurbMan wrote:
Also be aware that taller tires will effectively decrease your axle ratio. Formula is the old tire diameter divided by the new tire diameter times the axle ratio. For example, I have 4.10's on my truck, and when I swapped out the factory 245's for 265's, the larger diameter tires reduced my axle ratio to an effective 3.92. I noticed it right away in that the trans wanted to downshift a little sooner on hills, and that's towing 8500 lbs. I wanted a little more ground clearance and traction off road, but didn't go to 285's because I didn't want to decrease highway towing performance that much. So the 265's were a good compromise for me. If I was hiway all the time I would have stayed with the OEM 245's. If I was offroad more of the time, I would have gone with 285's.

The tire size you're referencing is the width, not the height.
FWIW, on my '07 Silverado 1500, I went from 245/70 (stock size) tires to 285/70 tires at my first tire change. The truck improved in every way. Better mileage, better handling, better ride, etc. Nothing changed regarding shifting. The speedo is off by about 3 MPH when it reads 75 MPH. Below that, its negligible.

Absolutely INCORRECT. Overall tire diameter is what affects the rear axle ratio, the width has got nothing to do with that. Do some homework, maybe start here.

Look at Michelin LTX/MS as an example. LT245/75-16 has an overall diameter of 30.5". The same tire in LT285/75-16 has an overall diameter of 32.8". So if you had 4.10 gears in your truck, your new effective axle ratio with the taller tires is 3.81. To maintain the same pulling power with the taller tires, you would need to re-gear to 4.41's...in the GM world 4.56 would be closest.

Fact is, you have reduced the pulling power of your truck with those taller tires. You won't notice it empty, and if you haven't noticed it towing, then your trailer isn't very heavy. Of course in FL your biggest hill is an interstate overpass...

Dude, come on, read my post again. What I said is absolutely CORRECT. You referred to the tire WIDTH and referenced that as the tire HEIGHT. The second number in this method of tire sizing gives reference to the height. I never said anything about gear changes. Don't be so quick to justify yourself that you fail to read.

I'll stick with what I said about my truck. With over 200K miles on it, mixed with highway driving and towing of up to about 6K or 7K pounds, I beleive I can be an accurate judge of its performance. The calculator you linked to is not accurate. It depends on linear data input and provides linear data outputs. As stock tire size increases, the calculator becomes less accurate, because overall diameter increases become less of a factor. If you increase the diameter of a compact car tire by 2", then you've made a huge change. But when you increase a large heavy duty tire diameter by 2", you've created an almost negligible impact. A straight-line calculator cannot deal with this.