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Old 02-22-2012, 10:49 AM   #21
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Re: Best tire choice??

Being new to 4 X 4s and with a Sportsmobile on order, I could use a little advice. Does increasing the width and/or height of the tires impact highway fuel mileage?

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Old 02-22-2012, 11:45 AM   #22
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Re: Best tire choice??

Quote:
Originally Posted by Tammy
Being new to 4 X 4s and with a Sportsmobile on order, I could use a little advice. Does increasing the width and/or height of the tires impact highway fuel mileage?
There's several on this forum that are tire savvy and will hopefully chime it but going from 33 to 35" is not that big a jump in size. I have no data with which to compare but going to 35" will result in greater rotating mass but also less revolutions per tire to the same distance. I suspect that the mpg is not changed much. You'll have more legs for the freeway and slightly lower engine rpm's.

I've been researching tires and have read every thread on the forum. The bigger issue IMO is the lack of E rated 315/75 tires available for 16 or 17" rims. Unless you go with a mud terrain the only E option appears to be a Goodyear Wrangler Duratrac. Lots of SMBs are on the road with D rated 315 BFG ATs but there are also an alarming number of reported failures. Just my 2 cents but the more I've looked into it, the more I'm convinced that sticking with an E rating is the way to go with a 10,000 lb vehicle hurtling down the highway at 75mph.
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Old 02-22-2012, 11:50 AM   #23
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Re: Best tire choice??

I'm thinking that as a general theory (I have no data), ANYTHING on the vehicle that increases in dimension will have a negative impact on mileage. That said, others may have found some positive effects from gearing v. tire size ratio

EDIT: JoeH said it better while I was typing.
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Old 02-22-2012, 12:16 PM   #24
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Re: Best tire choice??

Anybody ever tried the Cooper discoverer ST MAXX?? I think they come in an E rating, just wanted to check with the
forum.
Cheers,
C7
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Old 02-22-2012, 08:38 PM   #25
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Re: Best tire choice??

Quote:
Originally Posted by JoeH
Quote:
Originally Posted by Tammy
Being new to 4 X 4s and with a Sportsmobile on order, I could use a little advice. Does increasing the width and/or height of the tires impact highway fuel mileage?
There's several on this forum that are tire savvy and will hopefully chime it but going from 33 to 35" is not that big a jump in size. I have no data with which to compare but going to 35" will result in greater rotating mass but also less revolutions per tire to the same distance. I suspect that the mpg is not changed much. You'll have more legs for the freeway and slightly lower engine rpm's.

I've been researching tires and have read every thread on the forum. The bigger issue IMO is the lack of E rated 315/75 tires available for 16 or 17" rims. Unless you go with a mud terrain the only E option appears to be a Goodyear Wrangler Duratrac. Lots of SMBs are on the road with D rated 315 BFG ATs but there are also an alarming number of reported failures. Just my 2 cents but the more I've looked into it, the more I'm convinced that sticking with an E rating is the way to go with a 10,000 lb vehicle hurtling down the highway at 75mph.
Toyo and Nitto offer a reasonable selection of E load rated tires for 16 and 17 inch wheels.

I went from BFG to Toyo ATs a year ago and am sold on the Toyos.

R
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Old 02-22-2012, 10:08 PM   #26
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Re: Best tire choice??

Quote:
Originally Posted by EMrider
Toyo and Nitto offer a reasonable selection of E load rated tires for 16 and 17 inch wheels.

I went from BFG to Toyo ATs a year ago and am sold on the Toyos.

R
True but with the exception of mud terrains the selection goes to zip if you want a larger diameter tire than 285/75/16 or 17 with an E rating.
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Old 02-22-2012, 10:45 PM   #27
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Re: Best tire choice??

Asking "What's the best tire?" is kind of like asking "What's the best religion?".
I put my faith in the Hankook DynaPro MT 315/75-16 E.
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Old 02-22-2012, 11:17 PM   #28
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Re: Best tire choice??

Quote:
Originally Posted by Viejo
Asking "What's the best tire?" is kind of like asking "What's the best religion?".
I put my faith in the Hankook DynaPro MT 315/75-16 E.
A truism if ever there was one. I was simply responding to Tammy's post inquiring about the effects of a diameter and height increase of the tires on her SMB being built.

I'm all ears on a MT that doesn't sound like a banshee on the highway and lasts longer than 20,000 miles.
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Old 02-23-2012, 09:40 AM   #29
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Re: Best tire choice??

JoeH - My wife says that the MTs are a little louder. I don't know because I drive with my hearing aids in my pocket and the rest of the rig is pretty loud anyway. I'm hoping for better than 20K miles. They are at about 8K now and look pretty good. I had them siped for better ice traction when they were new and they ran all summer on rock with no chunking. Haven't found any ice yet this winter to see how much better the traction is.

Tammy - Added width will increase your rolling friction and cut gas mileage just slightly. Added height will throw off your speedometer and odometer causing your indicated speed to be lower that it actually is and causing the odometer to under report miles traveled. This will look like an increase in gas mileage but the opposite is true. You'll be speeding, getting worse mileage and risking tickets. Check your speedometer against a GPS if you change tire size.

Overall, the tires won't have a great effect on mileage. It's pushing 4 or 5 tons of van up and down the hills and pushing a big steel box through the air at faster that 60mph that eats the gas.
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Old 03-03-2012, 09:19 PM   #30
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Re: Best tire choice??

I took my 2005 rig with a SMB 4x4 conversion down to Discount today to have them test a 315/75/16 Goodyear Duratrac. Pic attached but it didn't fit very well which I found surprising since lots of folks are running 35" Toyo MTs or D-rated BFGs. I had them take it off while I mull over how bad I want a taller tire. I was surprised since the Toyo MT is 34.9 x 12.9" whereas the Duratrack is slightly smaller at 34.6 x 12.3. The BFG is 34.6 x 12.2.

I forgot my camera so I didn't get a pic of the Duratrac that was test fitted but here's a pic with 33" BFGs. It would be easy to trim the nerf board but with the tire turned there was less than an inch of space between the tire and the bushwhacker. Anyone else have that small a margin and is not rubbing with articulation? Short of re-arching the springs has anyone had to alter or trim the bushwhackers installed by SMB to create more space?
Attached Thumbnails
BFG 33s.jpg  
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