Bigger tires/mileage

01Sierra · July 10, 2005

I just wanted to get some opinions from those who've switched to bigger tires for their trucks. I just ordered a set of 285/75/16 Revo's. I've got a 4.10 rear and have figured the new tires will effectively change that to a 3.79. I'm assuming that will translate in better overall mileage. Although I'm sure it's not a huge difference though.

What about accelerating from a dead stop? Isn't going to take more RPM's to get the truck going? Won't this translate into more fuel usage while accelerating?

I'm also having green keys, and KYB shocks installed at the same time.

I'd really like to hear what others have experienced.

mmmikkke · July 10, 2005

I just wanted to get some opinions from those who've switched to bigger tires for their trucks. I just ordered a set of 285/75/16 Revo's. I've got a 4.10 rear and have figured the new tires will effectively change that to a 3.79. I'm assuming that will translate in better overall mileage. Although I'm sure it's not a huge difference though.

What about accelerating from a dead stop? Isn't going to take more RPM's to get the truck going? Won't this translate into more fuel usage while accelerating?

I'm also having green keys, and KYB shocks installed at the same time.

I'd really like to hear what others have experienced.

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I have 285/75-16 Toyo Open Countrys on factory aluminum 8-lug rims. With 9000 miles on my truck now, I get roughly 12 mpg around town, and my best results from an extended 70 mph cruise is 15 mpg driving into the wind on EB I-80 through Ohio. (6.0L, 4L80E, ext. cab)

The 285's cause my speedometer to be off by between 4 and 5 mph at 70 mph. So it reads 65, but is actually 70. Likewise, if the trip odometer reads that I travelled 300 miles, I actually travelled 320 miles. Both of these "errors" were corrected in my computation of mpg above. I suspect that some who have reported mpg drops did not bother to do any speedometer error correction.

I can still break 'em loose, with just a factory tune, so I actually didn't notice any difference in accelerating from a dead stop.

2004GMC2500HD · July 12, 2005

I have 285/70/17's BFG AT's on my 2004 GMC 2500HD reg cab 4x4 with the 8.1 / Ally and 3.73 G80 rear combo. The gas mileage still sucks (about 11 avg per tank) but there was not any noticeable power loss. I can still smoke 'em if I want to. I can still pull my 12,000 lb pound boat faster then I ever should.

Final word - They look MUCH better so get and don't worry about it.

2004GMC2500HD · July 12, 2005

One more thing, your speedo will be off. At an indicated 70 I am actually going 76. Just be aware of that. I normally drive about 78 in a 70 and if I put set the cruise at an indicated 78 I am really doing 85 because now its off by 7. If I am not careful a nice Officer might get lucky enough to get my autograph.....

BADGERMAN · July 12, 2005

When I put the 285's on my truck the milage went down a little, but I put on a more aggresive tread design. In order to get the speedometer reading right I purchased the diablo programmer and that fixed the speedometer and also brought my milage back up. But the milage still sucks I get around 11.5mpg.

It would probably get better, but I can't keep my foot out it.

Daubs · July 12, 2005

Put the 285's on, get yourself a Westers and be done with it.

Freyguy · July 12, 2005

I lost 1mpg when I went from the 245's to the 285's. I had to multiply my mileage by 1.067 to get the correct mileage, and then I could find out my true mpg when my speedo was off. I figured out that number by comparing speed by a gps at several points on the speedo and finding out the average difference. Now my computer is redone, so no more compicated math for me!

silverado3500 · July 13, 2005

Just wondering, if anyone has ever compared the fuel mileaged in a 285/75R16 vs a 255/85R16. The tire is very close in height, with the 255/85R16 being slightly taller, but a lot narrower. I was just curious if the width might have any affect on mileage?

GMSVCMGR99801 · July 13, 2005

With the torque of the 8.1's and the 6.0's small changes in tire sizes are not going to affect mileage enough to worry about. I am surprised to see all the effort going into adjusting for speedo discrepancy after tire size change. Why not take your truck to your dealer and have the new tire size programmed. They will probably charge you half an hour at flate rate and almost all sizes are able to be programmed by GM's Tech II. Your speedo and shift points will be correct afterwards. For the same $40-50 they will probably check for updates to your vehicle and install them.

Wingnut · July 13, 2005

With the torque of the 8.1's and the 6.0's small changes in tire sizes are not going to affect mileage enough to worry about. I am surprised to see all the effort going into adjusting for speedo discrepancy after tire size change. Why not take your truck to your dealer and have the new tire size programmed. They will probably charge you half an hour at flate rate and almost all sizes are able to be programmed by GM's Tech II. Your speedo and shift points will be correct afterwards. For the same $40-50 they will probably check for updates to your vehicle and install them.

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As far as I know, the dealer still can't reprogram for 285/75/r16s on the HD trucks.

But that may have changed.