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2005 gmc envoy_slt
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21 Posts
Discussion Starter #1 (Edited)
This may be a dumb question but I'm going to ask anyway... So a month ago I went in the ditch and blew the R/front tire off the wheel, this was the point I finally said "time for new tires" which was a little late, (I know, I know) I learned my lesson. Anyway got it towed, could only afford 2 new tires at the time, had them take the 2 best remaining tires and put on front, had the 2 new put on back. I hadn't put much thought into what the new tires were going to be, and the shop just ordered and mounted what they thought best. They put on 2 Mastercraft Courser STR 245/65R17.
After shopping around I decided I want some Falken Wildpeak A/T3W 255/65R17. Now I'm fairly certain they will fit my stock 05 Envoy if this info with some of my research I've found on the forums. https://tiresize.com/tiresizes/255-65R17.htm If I were to put 2 of these on the rear and put the 245/65 on the front would I have any serious issues? Or did I make a mistake and will have to buy a whole set? I know I could just buy 2 new Falkens at the stock OEM size but I really want the bigger ones. Any input is appreciated!
I haven't had any luck yet with trying to sell the month old Mastercrafts, but I wish I could find someone to buy them to recoup some of the cost and put toward the Falkens.
 

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2004 gmc envoy_slt
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2,194 Posts
Difference in tire size really only affects 4WD mode. I believe the general rule of thumb is to maintain a less than 1/4" diameter difference between tires. Go to tirerack.com, they have dimensions for most tires.
 

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2005 gmc envoy_slt
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Discussion Starter #3 (Edited)
I seldom if ever use 4WD unless I'm getting unstuck. The difference between 245/65 and 255/65 is only 1/2". I don't know maybe I'll just have to get 4 Falken 255/65s. I'm kicking myself for not bothering to shop around, it was a time factor mostly.
 

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2007 chevy trailblazer_ls
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340 Posts
The difference is also going to cause a problem with anti-lock brakes, stability control, and traction control. Here is a tire size calculator.https://www.discounttiredirect.com/learn/tire-size-calculator To keep the computers happy you just need all 4 wheels to have the same circumference ratio as the originals within a few percent. To keep the speedometer happy it needs to be the same circumference. This is a computer controlled vehicle, not a '53 Buick where size doesn't matter. :p

Going from 245 to 255 is probably close enough until you go to highway speeds and slam on the brakes or turn sharply.
 

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2007 chevy trailblazer_ls
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340 Posts
I wouldn't be worried about 1mph either. I would be more concerned about emergency maneuvers with the computers taking over. But it will PROBABLY be OK. I wouldn't because I tend to drive aggressively but you are close enough that I'm not going to say it will definitely be a problem. But if the traction control light starts flashing you know what the problem is.
 
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