maxum1989
Vancouver Canada
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Joined: 03/29/2006
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I have a 05 2500hd 6 liter gasser with 4.10 gears and am in need of new tires. I pull a fifth wheel that loaded is about 9000+/- pounds. I have found the stock tires that came with truck a little small for my liking visually. They are 245/75r16. I would like to get tires that are a little bigger with the same rims for cosmetic reasons and am wondering if it will affect my towing ability much. I know I am at the top level of towing capacity of this vehicle and don't want to make it any worse. But, if someone has changed the tire size on their truck and hasn't felt a noticeable difference I would love to hear from you.
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kaydeejay
SE Michigan, USA
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Joined: 07/26/2004
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Be careful putting bigger tires on the stock rims. You may be OK with 265/70s but not any bigger. (The rolling diameter of the 70's is almost the same as your current 65s so gearing and speedo will not be affected)
If you go for wider rims make sure they have the load capacity you need - at least as good as the tires you put on them.
Bigger tires WILL reduce your pulling ability (although that should not be an issue with a 9000# trailer) but will certainly affect the speedometer/odometer readings.
Keith J, Retired from GM Engineering
1999 Sunnybrook 27RKFS Fiver
2005 GMC Sierra 2500HD SLE 2WD/CC/SB/DA, 52 gal Titan tank, Bilsteins, Line-X, Westin steps, Prodigy, Retrax, 16K Superglide, 5th-Airborne pin box, Multi-vex mirrors, TST TPMS.
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Golden_HVAC
Fulltime, CA, USA
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Joined: 08/19/2003
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Hi,
If you go with a all steel tire, then you will have a stiffer sidewall, and this will enhance towing stability. The 235/85R16E is rated at 3,042 pounds and a little taller than your 70 series tire. It will not change the gear ratio much. There is a load inflation chart that Goodyear puts out with the revolutions per mile (RPM) for different tires. If you stick with a nearly identical rev per mile, it will not change the speedometer reading, or you will at least know by how much.
So if you change from a 700 RPM tire to a 670 RPM tire, then know that when the speedometer says 67 you will actually be going 70.
The 700 Rev per mile tire will be a smaller diameter than the 670 RPM tire.
Also do you understand what the 70 or 85 means? The tire width is in millimeters, so 235 / 85 R 16 is a 235 MM wide tire, and the 85 means the tire height from the rim to the outside diameter is 85% of that width.
So by changing from a 245 mm wide and 70% tall tire to a 265 mm wide and 70% tall tire you will gain about 15 mm more height. By changing to a 235/85 tire you will get 85% of 235 instead of 70% or 245, so it should be slightly taller. You could also get a 245/85R16 tire, but I am not sure if that is available in all steel configuration.
When I changed from all steel Michelins that came with my motorhome to a polyester sidewall tire (web site said quiet ride) I had to replace the tires within 400 miles back to a all steel design. The ride was scary downhill, with the tiny car pushing the back of the RV side to side into the curves. Going straight or uphill was not a problem, freeway seemed normal, but you can tell on the downhill.
Good Luck,
Fred.
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skipnchar
Topeka Kansas USA
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Joined: 12/17/2003
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Bigger tires means higher gear ratio and yes it will have an effect on towing. The AMOUNT of effect depends on what your final gear ratio becomes with the new tires.
2004 F-250 SCREW Long Bed (new)
OR 2004 F-150 HD (85,000 towing miles)
Rockwood 8314SS 34' travel trailer
We have enough YOUTH...how about a fountain of SMART
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surveyorjp
Missouri
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Joined: 09/05/2005
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Here is a link to a cool tire size calculator which will give you some important info about speedometer readings and other info when changing tire sizes.
http://www.miata.net/garage/tirecalc.html
2005 Surveyor SV-291
1995 Dodge Ram 1500 Laramie SLT 4x4 5.9L V8
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Sundowner1
Chesapeake, VA
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Joined: 11/21/2006
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I changed my truck tires over to 265/75R/16E at 40,000 miles and I now have 131,000 miles. I will never go back to 245's.
Really makes a difference.
Sundowner
04 Chevy2500HD, Duramax, ext cab, short bed, 4x4
08 fleetwood Quantum 325rkts
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JJBIRISH
Butler, PA, USA
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Joined: 10/06/2002
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Good Sam RV Club
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Tire comparison and speedometer calculator…
tire size comparison charts
Love my mass produced, entry level, built by Lazy American Workers, Hornet
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