Performance Changes from Changing Tire Size/Diameter

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by wmkess, May 8, 2013.

  1. wmkess

    wmkess New Member

    I'm shopping around for new tires for my car right now and it got me thinking about what tires I will be putting on my truck in the near future.

    I have a stock 2005 Silverado 1500 ex cab. It is 4x4 with the Z71 package and 4.10 gears. I plan on leveling it and getting a set of A/T's or possibly moderate M/T's. I'm perfectly fine with running stock size tires and just leveling out the truck but, like a lot of 4x4 truck owners, I would like to run 33"s. I assume most 285's would fit fine with just an extra 1" tall block in the rear and a torsion key kit set to 2.5-3" in the front, or whatever it takes to level it and maybe keep a slight rake. The thing I'm really curios about though is how 33" tires will change the performance (if even noticeable) of my truck given my gearing...theoretically it would improve mpg's as well as lose a little towing power. While I seriously doubt either impact would be significant enough to result in making a case that either size is more or less efficient I'd like to hear some opinions or facts.

    On a side note, is it typical or possible to get your computer programed to the new tire size for things like transmission shift points? And if so, is it recommended? TIA.
  2. j cat

    j cat Active Member

    my 2000 Silverado LT EXT CAB 4X4 3.73 diff just got 18.5 MPG on a recent 1000 mi trip. I use regular 87 octane 5.3L engine 4l60 . the tire type are the same that came with the vehicle in 2000. 245 75 R16 AT . I still have good tread on the current tires which are the only set of 4 that I purchased 8 years ago .

    going with a larger dia. tire you will have traction problems in snow . where I live these tires [OEM] give me no problems with snow or pulling the 20 ft boat out of the water at the boat ramp. With the larger tires and the type tread you will get better MPG by a small amount according to those that did the swap. I doubt you will see any loss in tow/haul with the larger dia. with 4.10 rear diff.
  3. wmkess

    wmkess New Member

    Appreciate it j cat.
  4. dsfloyd

    dsfloyd New Member

    with the 4.10's in the truck, going to 33" should not effect much of anything noticeable. Your speedo will be off though so without calibration could slightly change shift points.
  5. SurrealOne

    SurrealOne Former Member

    What he said, times two. And to add to it, if you want to tweak your shift points consider a DiabloSport InTune and a custom tune from DiabLew aka Lew aka [MENTION=32828]06MonteSS[/MENTION] on this site. Lew bundles tuners and his custom tuning, so you might PM him about the tweaks you want. He should absolutely be able to help you with tire size (which you can do via the InTune, yourself) and the shift points. If you've not done this kind of thing before, fear not, he's worked with people who can barely operate a computer, before.
  6. 06MonteSS

    06MonteSS New Member

    ;) what he said ^ ^ ^
  7. zogg

    zogg New Member

    I had an 06 2500 6.0 gas truck with the 4.10 gears. I went to larger a/t tires on Hummer h2 wheels......

    The added unsprung weight along with the reduced final drive dropped my mpg from 14 to 11 and really caused power problems when pulling my 5th wheel....i swapped back to the original tires and wheels so I could tow....hated it.

    Actually, on pulling hills with the 5th wheel, it would shift down to 2nd gear on hills where it only shifted to 3rd prior to the tire swap....awful! But, they looked neat....haha
  8. wmkess

    wmkess New Member

    Ah, I totally forgot to consider the extra weight that comes with larger tires! Were the wheels also bulkier as well? I plan to keep my factory wheels.

    - - - Updated - - -

    Awesome! I'll look into that for sure.
  9. walmart player

    walmart player New Member

    So if you go to 33 inch tires what's the average mpg drop? Or like so of you said there really ist any? Im alittle confused I guess ;)
  10. j cat

    j cat Active Member

    the more you increase the height the more the MPG drops. the bigger and heavier the tire the load increases and MPG drops.

    a tire with low rolling resistance will increase the MPG. AT tires you get better traction but loose some MPG when compared to the passenger tires that have the low rolling resistance , but you loose traction in difficult road conditions.

    with the AT tires I have I have never had any problems in the snow . I know if I switch to the low profile low rolling resistance tires I could get a little more MPG but I got a truck to get me to work in the snow so the AT tires will stay . depends what your looking for in performance with a truck .
  11. reggiecab2000

    reggiecab2000 Member

    you really wont notice much unless you are coming from the 4.3 v6 with 3.43 gears like me lol i upgraded to 4.10s and am theoretically left with a little bit more power than stock according to my tire size to gear ratio.

    I hear this all the time when people talk about getting bigger tires and wheels. more than likely 99% of people getting aftermarket tires and wheels will be getting aluminum wheels which is always significantly lighter than the factory steel wheels, regardless, the only thing thats going to affect your mpg is tire size AND tire width...

    weight of a tire??? unless each tire is about 200 pounds heavier than you will never notice a single difference simply because of the weight of the tire...

    thats like saying you lose 2 mpg just because you have a person in the passenger seat...

    a simple 10-15 pounds extra to each tire on a truck is like adding a tank top on your body, it aint gonna change anything about your power...
  12. dsfloyd

    dsfloyd New Member

    agreed as there is alot that goes into it.

    Using my truck as an example I went from 3.73 (31" tires) to 4.10 (35" tires) when I lifted it. I did the 4.10 (which is taller than a stock effective gear ratio) because the truck was my daily driver and mostly highway mileage. The 4.10 kept the rpms low on the highway and I actually lost no mpg after lifting (an oh so awesome 12mpg). In all honesty if I were to do more towing or lived in an area in the mountains again the 4.56 would be a much better option for me. Now to the tires part. My stock wheels were actually very light and I used those for a while with the 35" tires (and they were all terrain tires). I later switched rims and tires (still 315/75/16), once again rims were not very heavy but I went to a hybrid AT/MT tire and I lost about 1 mpg with that change. I only had highway tires in the stock form for 10 days (truck was then stolen and when I got it back I put all terrain tires on it as the smugglers put a beat up set of off road tires on it), and with the 1 or 2 tanks of gas on those I had maybe a 1-2 mpg increase over the all terrains. Unfortunately lots of factors go into mpg like the 10% ethanol in gas or the summer and winter blends here in CA.

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