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Old 03-04-2013, 06:05 AM   #1
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Finding Rim Width and Tire Width's effect on towing performance

Hi all. My TV's original manufacture's stock tires were LT265-70-17 (E rated) - from door panel. The owner before me put on LT285-70-17 (D rated) tires (seems weird but I digress). As we just bought a 5th wheel, I am wanting to keep the same rims but buy "E" rated tires (which will handle my GRAW + pin weight). As I bought the truck used, I'm unsure if the current rims are the stock rims, and therefore, unsure of the exact width of the wheel rim. So....I have a few questions:

1) Is there an easy way to determine the rim width without taking off the tire? i.e.) do the rims have numbers on them somewhere?

2) Are there any disadvantages of going with the widest tires possible for the current rims? i.e.) I have read that wider tires are better for stability/decreasing tire squirming, but is there a downside?

3) Does anyone have any recommendations for LT tire brands/models to consider that have firm sidewalls and are "E" rated? They will see primarily highway miles and hopefully no snow.

Thanks in advance for your input....much appreciated
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Old 03-04-2013, 07:17 AM   #2
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I would guess you still have the stock rims since the previous owner stuck with 17" tires. Usually if you get new rims you up the size of the rim. Example: you move up from 17" to 18" or 20" trying to fill the huge wheel well. Since he only went to a bigger 17" tire it is a good bet the rims are original. Go to the dealer and look at other stock 2011 trucks to help determine what you have.

Dis-advantage of wider tires is they are worse on snow/ice.

Not a recommendation but my truck has General Grabber HTS.
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Old 03-04-2013, 07:03 PM   #3
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Most tires will work for a 1.5 to 2" range of rim widths. Width is less of a factor than diameter and sidewall stiffness in control. Having G rated tires the sidewalls should be stiffer than average if you have them at their max rated PSI. A mistake often made if to have less air in the tires with the notion that the full load capacity is not needed. While true in part it will result in more scrubbing of the tires, less even tread wear, and more sway as the loaded tire compresses more on a turn.
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Old 03-04-2013, 10:26 PM   #4
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Wheel width is critical for a load carrying tire for several reasons.

Racers may play with different wheel widths to obtain a desired tire performance however best load carrying ability is achieved when the wheels width equals the tires tread width.

1. I use a roll out tape and slide the end through a slot in the wheel and measure from inside of the wheels tire mount flange to the other inside flange. When the tire is removed is the best time to measure the wheels actual width. A google or a youTube is your friend.

2. Wider tire doesn't always equate to a better load carrying tire. Also, there are downsides to too wide of a tire for the wheel. This from;

Dunlap
RIM WIDTH
Correct rim width ensures flex at the designed flex point in a tire sidewall for optimum tire performance.

If the rim is too narrow, the flex point moves toward the shoulder area, creating heat buildup in the shoulder, which reduces tire life and could result in failure.

If the rim is too wide, the flex point moves towards the rim area, causing heat buildup in the lower sidewall, which reduces tire life and could result in failure.

Within the acceptable range of rim widths, one can select wider or narrower rims than the measuring rim. Selection of a wider rim, from within the approved range, (T & RA tables) stiffens the sidewall and improves handling at the expense of handling. If carried too extreme, either too narrow or too wide of a rim, it can result in uneven tread/pavement contact pressure causing uneven wear and potentially reduced traction, or increased vulnerability to bead dis-lodgement.

3. I'm not a brand cheerleader as I've had good luck with BFG/Uniroyal/Michelin/Cooper/Firestone/Goodyear/Bridgestone LT tires
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Old 03-04-2013, 10:35 PM   #5
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Most 8 bolts rim equates to load range E capacity. There are no more then 3175lbs capacity on any size 17in tires. I went to 18in to increase mine to 3750 with 285-70-18 LT tires.
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Old 03-04-2013, 10:54 PM   #6
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Originally Posted by caissiel View Post
Most 8 bolts rim equates to load range E capacity. There are no more then 3175lbs capacity on any size 17in tires. I went to 18in to increase mine to 3750 with 285-70-18 LT tires.
And then only if the rims will take the maximum pressure the tire will. We had 275/70's on our motorhome, to get max weight capacity took 131 psi, but the rims were only good for 120 psi. Michelin wrote us a letter on their letterhead allowing the weight capacity for 125 psi with only 120 psi. Guess they had a lot of faith in their tires and we ran them that way for 8 years with no trouble.
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Old 03-05-2013, 01:27 AM   #7
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tirerack.com

this has a lot of info, dia. of tires,wheel width specs, weight ratings, all the good stuff.
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Old 03-06-2013, 05:37 AM   #8
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Originally Posted by Oregonbound View Post
... My TV's original manufacture's stock tires were LT265-70-17 (E rated) - from door panel. ...
For maximum towing performance, that's the size you want. Taller tires reduce power, torque, and MPG, plus they mess up the accuracy of your speedometer, odometer, and tripmeter. Wider tires reduce MPG and reduce traction in the slicky stuff.

Quote:
2) Are there any disadvantages of going with the widest tires possible for the current rims?
Increased aerodynamic and mechanical drag = decreased MPG. The wider tires have more frontal area, so they have more wind resistance (aerodynamic drag). And they have a bigger tire patch (where the rubber meets the road) so higher rolling resistance and mechanical drag.

Decreased traction in snow or mud. The wider tires tend to float on top of the slickey stuff instead of biting down to get traction.

Quote:
3) Does anyone have any recommendations for LT tire brands/models to consider that have firm sidewalls and are "E" rated? They will see primarily highway miles and hopefully no snow.
Most major brands probably have similar results when they have the same specs of size, tread pattern, and load range. I have had better luck with Michelin, so I pay a bit more to run Michelins on my tow vehicles. In your size with load range E, Michelin makes the LTX with three different tread patterns, A/S, A/T2, and M/S2. I now have the LTX A/S on mine, but I live in the desert with rare mud and even rarer snow. If I lived in Northwest Montana, I'd probably run LTX M/S2.
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Old 03-14-2013, 03:10 PM   #9
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Well, a little bit of an epiphany today. Even though the current 285-70-17 tires are D rated, they still have a load capacity of 3195 - the same as 265-70-17 tires that are E rated. In speaking with a tech at Tire Rack, he states that the 285s, even though D rated, are able to offer this load capacity because of the increased width. He also states that that the difference in MPG between 285s and 265s is negligible and that going to an 80 psi tire (the 265 E rated) will result in a "stiffer" ride. I think I'm going to stick with the current D rated 285s and save $1000.00. Still, appreciate everyones 2 cents. Please let me know if you have other opinion - still awaiting 5er to be delivered.
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Old 03-14-2013, 09:13 PM   #10
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LT265-70-17 (E rated) - from door panel is what the truck is rated for by the manufacturer and DOT and is what you are supposed to run on the vehicle.
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Old 03-16-2013, 12:25 PM   #11
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LT265-70-17 (E rated) - from door panel is what the truck is rated for by the manufacturer and DOT and is what you are supposed to run on the vehicle.
Thats for weight purposes. The tires need to be rated for the weight of the trucks RAWR. My truck has a 6000lb RAWR and the tires are Michelins that are rated at 3000lbs each. 245/70/17. If I jump up to 265/75/17's then the RAWR jumps to 6200. Same axle just different tires. People upgrade tires everyday and no issues.
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Old 03-16-2013, 09:11 PM   #12
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If I jump up to 265/75/17's then the RAWR jumps to 6200. Same axle just different tires.
Not literally true. Assuming by RAWR you mean the rear GAWR, then the rear GAWR is based on several components - wheels, axle, suspension, wheel bearings, etc. Your rear tire weight rating goes up to 6200 because of the bigger tires, but not your rear GAWR.
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Old 03-17-2013, 04:48 AM   #13
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Do not think that the tires at 60lbs will be equal capacity. I would not take that chance
Stability with softer ride will be affected. It will be like riding on underinflayed tires and the tire will roll side to side. Loading a 5th wheel or any TT trailer on the rear of a truck is far different from loading the truck box. You have a 12 ft high unit wanting to steer the truck and 80 lbs in the tires is required.

DO NOT TRY 60 LBS ITS UNSAFE .

I have seen recommended trucks by dealers with stripped rear studs due to side forces caused by. 5th wheels on 5 bolts rear axles.
In addition if you ever blow a rear tire it will ruin the box. I had 2 rear flats on E range tires and all I got was vibrations. I will never tow with anything else the E's for that reason.
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Old 03-17-2013, 10:37 AM   #14
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Thanks all. I did check the door panel and sure enough, I re-remembered that this is where I initially got the "I need E rated tires" idea...sooo... will be biting the bullet and getting the E rated 265-70-17s (probably the Michelin LXT M/S2s which have 3 steel belts). Will save the 285-70-17 D rated for when we are situated and not pulling the 5er. Last thing we want is to have a tire blow out pulling our brand new Redwood:(
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