OK so i am brand new here and have been reading posts. I have a 08 Tahoe Hybrid that i love and just put 20" rims on it. Has anyone had problems with doing this? I see that the 2010 has a 20" option so i just had them put on. I did notice the mileage went down, but i expected that. Any other problems known to anyone? How about getting the mileage back, anyone know how to get better milegage? I spent a good amount of money fixing the outside, guess I should have thought about the mileage adn other problems before I get the rims.

 

Did you get a value for revs per mile for your new tires and wheels? You can look up these rev/mile differences on interactive charts from Discount Tire. So plug in your old 265, 65R, 18 and compare to xxx, yyR, 20. The rev/mile may be very close. The chart will also give you an idea as to how much your speedometer is off now.

http://www.discounttire.com/dtcs/infoTireMath.dos

The rev/mile relates to a tire's loaded rolling radius. If all four are the same size the
hybrid probably won't know the difference.

Now about mileage. A wider tire presents a higher wind drag. Different tires have different rolling resistance. Lastly. If the new tire raised the vehicle, more air gets underneath to drag off the suspension.

 

Don't forget rotating mass. The mass times the arm (length the center of mass is from the center of the wheel. The larger the rotating mass, the lower the MPG.

 

Other than looks I do not think you gain anything other than losing milage.

 

So i just talked to the dealership and they told me that i could have transmission or drivability issues with 20" rims. is this true? has anyone had problems or heard of this?

 

I have heard that Escalade are having some issues in transmission, maybe that could be the reason!!

 

Buck; there is a guy out here with 26" wheels. I can't remember the name. Physics is all that matters.

1) Tire and wheel radius. If equal the hybrid will never know the difference.
What size are the tires? 315, 45R ????? etc? Use that on-line calculator.

2) Offset. Us "old School" guys remember Chome Reversed wheels. If your wheels change the track width the offset may impart extra bending forces into the axle shafts that they were not designed for. Wide offsets can screw up your front alignment too.

3) The "K" factor or springy factor of the specific tire side wall. Taller wheels have stiffer side walls many times. Most modern vehicles have a sophisticated enough powertrain control system to tune out body/chassis resonance and keep the drive train from making frequencies that excite the chassis.

4) The "un sprung" mass. FJ's comment on the mass of your new tires and wheels. Again your suspension bushings, spring rates, and schock absorber damping rates are tuned to the stock configuration.

3 and 4 probably won't hurt the truck. But they may create a "funny" feeling that you may or may not like.

 

that must be the 2006 and earlier escalades. as I am a member of the biggest escalade forum worldwide and there is no mention of any tranny issues. that applies to the regular escalade with fulltime awd as well as the selectable 4wd hybrid. there was a tsb however on the tranny ecu that the dealer just have to flash for updates.

 

old tires were 265, 65R, 18. new tires are 275 55r 20. the calculator doesent show much difference. would I be right to assume the dealership is just giving me a FYI? i just spent 150 bucks installing them and the TPS, I dont want to have to get rid of them.

 

Buck: I wouldn't worry about it. Most dealers are going to be very cautious. It looks like you may have about a 1% slower reading speedometer based on rev/mile difference.

This could change to 0 or 2% based on how hard you run the tire pressure.

And it is nelsontx that has the 26" on his.