Can I use 285 65 20
What is the stock size? You can compare tires with this handy tire size calculator ---- https://tiresize.com/calculator/
What is a stock size if you mean what is on now it's 17
Stock is 16". To get even close to your original gear ratios, use the calculator FoR suggested. You will have to go to an extremely low profile tire, causing poor ride, and stupid looking
https://www.google.com/search?q=2005+GMC+Yukon+XL+1500+SLT+&ie=utf-8&oe=utf-8 == Wheel size: 16″ diameter,
Your speedometer will read 65 mph at a true 73.5mph. Changing wheel/tire sizes is not so bad, but you are decreasing your gear ratios all the way through the spectrum it will tax your transmission. You NEED those lower gears to get going
Big wheels and tires are heavy and will increase stopping distances considerably. Heavier wheels and tires will also reduce ride quality as well. You could use the extra room that 20" wheels provide to install some monster Brembo brakes though.
FordNut is right. Big tires will reduce your towing and hauling capacity especially in the hills. It will also reduce acceleration and increase passing distances.
I am running 285/65/18 on my Yukon, it dropped my average mileage to 12.5 it was getting right at 14. It did change the way it shifts under normal driving but with the trailer tow setting that really isn't a problem for me, there was no noticeable difference with the ride or stopping distance but there is a lot of tire squealing noise when making slow turns like in a parking lot. I did recalabrate the speedo to accommodate the tire/wheel change. When they worn out I won't but anything that big back on it, just too much of a tire. HTH
One thing I can say with absolute certainty is you can trust tennisshoes advice.
I run 285's on my Ford F-150 which increases my ground clearance 1/2" and improves handling and off road capability quite a bit over the stock 265's.
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