what the biggest tire i can fit? -1999

el patron · #1 03-03-2010, 10:06 AM

1999 gmc sierra crew cab, tow package, no lift.

i have michelin ltx ms (255 65 16)on my truck now, but i need new tires and i have some 17" rims i want to replace the 16" factory rims with.

according to Tire Rack , the diameter of the michelin tires i have now is 29.2"

the tire i am considering is the Kumho Road Venture AT KL78 (265 65 17), but they also make a 265 70 17.... i havent been able to find the diamter info on these tires..so if anyone can help with that, that would be one more piece of the puzzle.

but the basic question is, what is the largest diamter tire i can fit on my truck without any rubbing..and keep in mind my truck is not lifted.

thanks !!

el patron · #2 03-08-2010, 08:35 AM

well, ive been able to answer part of my question regarding the diameter of a tire.

to calculate a tire diameter follow this formula:
Width x Aspect Ratio = Section Height
Section Height x 2 = Combined Section Height
Combined Section Height + Wheel Diameter = Tire Diameter

so for example, my current tire is a 255 65 16

255*(.65)= 165.75mm
165.75mm * 2 = 331.5mm (331.5mm/ 25.4) = 13.05"
13.05"+16"= 29.05" (tire diameter)

the tire i want to buy is a 265 65 17....so,

265*(.65)= 172.25
172.25mm * 2 = 344.5 (344.5mm/25.4) = 13.56"
13.56" + 17" = 30.56" (tire diameter)

so the difference in tire diameters is 1.51", this means that the new tire will be 3/4" of an inch larger in the wheel well. i think this is going to work for me.

Molson02536 · #3 03-08-2010, 08:40 AM

Quote:

Originally Posted by el patron

well, ive been able to answer part of my question regarding the diameter of a tire.

to calculate a tire diameter follow this formula:
Width x Aspect Ratio = Section Height
Section Height x 2 = Combined Section Height
Combined Section Height + Wheel Diameter = Tire Diameter

so for example, my current tire is a 255 65 16

255*(.65)= 165.75mm
165.75mm * 2 = 331.5mm (331.5mm/ 25.4) = 13.05"
13.05"+16"= 29.05" (tire diameter)

the tire i want to buy is a 265 65 17....so,

265*(.65)= 172.25
172.25mm * 2 = 344.5 (344.5mm/25.4) = 13.56"
13.56" + 17" = 30.56" (tire diameter)

so the difference in tire diameters is 1.51", this means that the new tire will be 3/4" of an inch larger in the wheel well. i think this is going to work for me.

Here is a link that should help you get the answer your looking for.
http://readylift.com/t-tire-calculator.aspx

Good luck on your tire size hunting.

el patron · #4 03-08-2010, 09:55 AM

this website just confirmed my calculations..

im interested in the speedometer reading difference though..
good to know that if my speedometer says 80, i would actually be going 76 (caused by the different tire diameter)...

i wonder if there is a website that can tell you what youre difference in MPG's will be?

el patron · #5 03-08-2010, 09:58 AM

Quote:

Originally Posted by Molson02536

Here is a link that should help you get the answer your looking for.
http://readylift.com/t-tire-calculator.aspx

Good luck on your tire size hunting.

thanks, this website just confirmed my calculations..WHEW!! good thing too becuase i just ordered the tires !

im interested in the speedo error thing..
i didnt think about that ,
it says that if im doign 80 with the new tires that i would actually be going 76.

el patron · #6 03-10-2010, 11:20 AM

i saw a chevy with the exact same body style as my gmc with 265 70 17's on...and it did not appear to have any lift on it. so thats encouraging to me.

i did order the 265 65 17 Kumho tire...i havent mounted them yet, so we will see how they look.

my (new to me) rim is black, but i dont have any center caps...i was thinking of painting the original wheel nut cover/center cap with the duplicolor spray paint..black to match..leaving the GMC letters red....

does anyone have any epxerience with the duplicolor spray paint? how durable is it? do you think it will get all scratched up the first time i take it to the car wash and use a brush on it?

Molson02536 · #7 03-10-2010, 02:00 PM

Quote:

Originally Posted by el patron

i saw a chevy with the exact same body style as my gmc with 265 70 17's on...and it did not appear to have any lift on it. so thats encouraging to me.

i did order the 265 65 17 Kumho tire...i havent mounted them yet, so we will see how they look.

my (new to me) rim is black, but i dont have any center caps...i was thinking of painting the original wheel nut cover/center cap with the duplicolor spray paint..black to match..leaving the GMC letters red....

does anyone have any epxerience with the duplicolor spray paint? how durable is it? do you think it will get all scratched up the first time i take it to the car wash and use a brush on it?

Use the Duplicolor for brake calpiers, they last much longer and is more durable. Good luck and we hope to see a picture of your Sierra soon.

el patron · #8 03-15-2010, 01:51 PM

well, i finally had the tires balanced and mounted..

just FYI, the tire shop charged 15 per tire for that..

anyhow, the rims and tires look awesome..and there is no rubbing, i think i stated in my previous post that these new tires i was putting on were only 3/4" of an inch larger...that was correct...

there has not been any rubbing whatsoever and i feel confident in the way this size tire fits in the wheel well.

i hope this thread will be helpful for others looking at new tires. ill be sure to post a few pics of my new wheels and tires..

el patron · #9 03-15-2010, 01:54 PM

ps, i will not be painting the center caps , as previously mentioned..
after putting the new rims on, i prefer to have the lugnuts exposed..
but i do think i will paint the very center (the end of the axle?) where the rim doesnt cover unless there is some other flat center cap i can put on without covering the lugnuts.