Best Wheel Size?

[Razinni]

I have a stock 2003 4x2 1500 suburban and I'm noticing that most newer suburbans have larger wheel sizes. Anyone have a strong opinion about increasing the wheel size to fill out the fender well a bit better? I'm not interested in anything radically low profile. Input on brakes and speedometer changes would also be appreciated. According to Chevrolet the new 2014 wheel sizes are as follows.

Front Tire Size P275/55R20
Rear Tire Size P275/55R20
Spare Tire Size P265/70R17 (???)

 

[SWHouston]

Effects of a Larger Tire:

Differential in your Speedometer Reading...
Your speedometer will read a slower mph than what you're actually going.

A Reduction in perceived Braking Power...
From some to a great extent, you will have to apply more pressure to the Pedal, to get your vehicle to stop.

A Reduction of Engine Power...
You will have to apply more throttle to get things going.
That being said, I cannot tell you that you will absolutely realize a reduction in Gas Mileage, but, 99% of the time, that usually is the case. The reason for these negative effects, is an increased distance/fulcrum between the Center Line of the Axel, and the Surface of the Road. Your individual Driving Habit, can influence the effect to a large extent.

A Reduction in control on Wet Surfaces:
Two things contribute to Wet Traction, those being, the weight of your Vehicle, and the Speed you are driving. Increasing the width of your Tires, may cause an excessive Bow Wave to be created, which will seriously effect control of your vehicle.

But, there are some positive tradeoffs...
More Rubber on the Road, generally means Better Dry Traction...
Again, your ability to apply the Brakes notwithstanding, and this "traction" mostly applying to when it is Dry. But, often times as stated above, a larger tire will cause Hydroplaning to some extent. So the traction is selective, and has a lot to do with the Tread on the Tires as well.

Increase in the Load Carrying Capacity (proper width Rims required)...
With a larger Tire, greater Loads can usually be applied/carried. But having correctly sized Rims, are vital to this. The sidewalls of a Tire were intended to operate in a Vertical line, and varying the rim width (either narrower or wider) can negate, and seriously detract from this. And, the Loading capability may be reduced, when a lower Profile Tire is installed.

Functionality...
When encountering Sand, Mud, Rock, Snow or Ice, having the right set of Tires on your vehicle can mean getting home or NOT ! Oftentimes, when the operator is aware of the scope of problems which a large Tire causes, and compensates for those, having a "dedicated" set of tires can be a great advantage.

The Appearance (usually the most popular reason)...
What can I say, having a nice gnarly set of tires on your ride, does have an appealing effect !

Use the proper rated Tires...
One needs to keep in mind, that Suburban's and Tahoe's are Trucks, not Passenger Cars !
The "LT" Type Tire is recommended for our rides. There's a considerable difference in the way these two type Tires are made, and given the weight of our vehicles, the "P" just doesn't cut it, and have failed when placed under stressful circumstances.

 

[Razinni]

So the last thing I want to be is a guy who answers his own question but I took the reply above. Which I agreed with 100% and went to see a Tire and Wheel Specialist here in Atlanta GA. Here is what he said.

1. The total diameter of the wheel is a combination of the rim size plus the height of the profile of the tire.
2. He says that is around 32.5" Diameter.
3. He says that if I increase the stock wheel size from 16 to 18" we'd balance that out with a thinner profile tire. In other words he wouldn't ever want to put tires and wheels on my vehicle that increased the total diameter by more than 1".

This explains why the 2014 spare tire is a different wheel size from the rest. Even though the wheel itself is less diameter than the 20" the spare tire is taller compensating for that and therefore you wouldn't be going down the road leaning towards the spare.

So what I'd like to do is hear from someone that has increased from a 16" wheel size to something larger and with the shorter profile tires were there any noteworthy experiences.

Thanks!

Raz

 

[SWHouston]

1.
The total diameter of the wheel is a combination of the rim size plus the height of the profile of the tire.

2.
He says that is around 32.5" Diameter.

3.
a/He says that if I increase the stock wheel size from 16 to 18" we'd balance that out with a thinner profile tire.

b/In other words he wouldn't ever want to put tires and wheels on my vehicle that increased the total diameter by more than 1".

1:
That's true.

2:
Actually, the size you quoted runs from 31.8 to 31.9". The diameter which you should attempt to maintain, is the diameter of the Tire which is listed on the Placard/Sticker on the Drivers Door. That's the original intended size.

3:
a/Adjusting the profile is exactly the way to maintain diameter when changing Rim Diameters. However, using lower profile Tires, present their own advantages and disadvantages.

b/I'm not sure if I agree with that statement...
Not that he's incorrect, but, people upsize their Tires well more than 1" all the time for various reasons. But true, keeping it at/under 1" would limit the effects as I mentioned to literally imperceptible. One of the more important issues in doing this, is to select a set of Rims, which match the width of the larger tire. Having the Tire width and the Rim width the same, considerably increases several aspects of performance.

For Instance...
The LT275/55R/20 are 8.7" wide, so, you'd want to use a 8.5 x 20" Rim with those.
(not just any 8.5x20, but ones specifically designed to be used on your vehicle)

But, if you're willing to deal with those issues, don't let going larger get in your way. Just do it and enjoy