Tire Sizes....??? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

ashx2 · 09-23-2020, 09:59 AM

The tires that were on my '72 when I purchased it have gone south on me. Tire sizing is not exactly my comfort zone and don't know a lot about it. The current tires I have are P275/60R15. I have a neighbor down the road that has some tires that are P265/70R15..... What will be the difference, the height of the tire? Or how does that work? I'm assuming that the 15 is the size of the wheel itself, so that should be a doable thing.....or am I off base on this? Thanks

**bigmac73** · 09-23-2020, 10:05 AM

https://tiresize.com/converter

try this , I am thinking they will be the same since you are going bigger on the sidewall but less on the width

67C10Step · 09-23-2020, 10:15 AM

Losing not quite half an inch in width and gaining just under and inch in sidewall height.

275 mm width to 265 mm width

The sidewall height is the next number as percentage of width, 275 x 0.6 = 165 mm

For the 265/70-15 the sidewall is 265 x 0.7 = 185 mm

The overall diameter of the 265 tire will be 2x the sidewall difference so that would be (185-165) x 2 = 40 mm about 1.6" bigger diameter.

ashx2 · 09-23-2020, 10:36 AM

thanks guys. I just need these to make it to where I can move the truck while it's being worked on. I'll eventually go with something better once all the important stuff is fixed and running again. I appreciate the info!

**HO455** · 09-23-2020, 01:41 PM

I was going to say the biggest difference between the 2 sizes would be the change in overall rear ratio. But for your current plan that wouldn't matter, unless the front end of the truck has been lowered a bunch.

cj847 · 09-23-2020, 05:50 PM

Here is a tire sidewall chart I built trying to decide what diameter rim and tire size I want. This is the tire sidewall x 2 changed to inches. Add this number to the rim diameter for the overall diameter. The stock tire was about 28.8". Please note that not all diameter tires are available in all these sizes. This is just a guide.

What I haven't been able to find is what is the largest diameter tire you can run with stock suspension......I think it is about 30.5 to 31" but not sure.

I don't know how to upload an Xcel file so it is just a picture.

Name: tire sidewall.jpg
Views: 277
Size: 64.8 KB

Name: tire sidewall.jpg
Views: 277
Size: 64.8 KB

**Pro299** · 09-23-2020, 10:51 PM

cj847 I can tell you the max must be more than 31 because I have 31X10.5X15 on stock height and it fits fine (and looks just right IMHO).

**bigmac73** · 09-24-2020, 05:40 PM

40 years ago in high school I ran a 32 x 11.5 x15 on a 72c10with stock suspension and had no issues

09-23-2020, 09:59 AM	#1
ashx2 Registered User Join Date: Aug 2008 Location: Graham, Texas Posts: 239	Tire Sizes....??? The tires that were on my '72 when I purchased it have gone south on me. Tire sizing is not exactly my comfort zone and don't know a lot about it. The current tires I have are P275/60R15. I have a neighbor down the road that has some tires that are P265/70R15..... What will be the difference, the height of the tire? Or how does that work? I'm assuming that the 15 is the size of the wheel itself, so that should be a doable thing.....or am I off base on this? Thanks

09-23-2020, 10:05 AM	#2
bigmac73 Senior Member Join Date: Mar 2012 Location: Chesapeake, Va Posts: 1,275	Re: Tire Sizes....??? https://tiresize.com/converter try this , I am thinking they will be the same since you are going bigger on the sidewall but less on the width __________________ Mike 72 C-10 Cheyenne off frame resto and Upgraded to 4 wheel disk, Tilt, Dakota Digital Dash / Rear slider. 421 SBC / TH350 3000RPM Stall Progression Ignition /Holley 750 DP/3:73 gear Eaton Limited Slip unit / 2 1/2 exhaust glasspacks

09-23-2020, 10:15 AM	#3
67C10Step Registered User Join Date: Jul 2019 Location: Beebe, AR Posts: 2,401	Re: Tire Sizes....??? Losing not quite half an inch in width and gaining just under and inch in sidewall height. 275 mm width to 265 mm width The sidewall height is the next number as percentage of width, 275 x 0.6 = 165 mm For the 265/70-15 the sidewall is 265 x 0.7 = 185 mm The overall diameter of the 265 tire will be 2x the sidewall difference so that would be (185-165) x 2 = 40 mm about 1.6" bigger diameter. __________________ 1967 C10 1980 Jeep CJ5 2020 Toyota 4Runner 2020 Toyota CH-R 2020 Acura MDX

09-23-2020, 10:36 AM	#4
ashx2 Registered User Join Date: Aug 2008 Location: Graham, Texas Posts: 239	Re: Tire Sizes....??? thanks guys. I just need these to make it to where I can move the truck while it's being worked on. I'll eventually go with something better once all the important stuff is fixed and running again. I appreciate the info!

09-23-2020, 01:41 PM	#5
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 10,786	Re: Tire Sizes....??? I was going to say the biggest difference between the 2 sizes would be the change in overall rear ratio. But for your current plan that wouldn't matter, unless the front end of the truck has been lowered a bunch. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

09-23-2020, 05:50 PM	#6
cj847 Registered User Join Date: Sep 2016 Location: Ft Smith, AR Posts: 541	Re: Tire Sizes....??? Here is a tire sidewall chart I built trying to decide what diameter rim and tire size I want. This is the tire sidewall x 2 changed to inches. Add this number to the rim diameter for the overall diameter. The stock tire was about 28.8". Please note that not all diameter tires are available in all these sizes. This is just a guide. What I haven't been able to find is what is the largest diameter tire you can run with stock suspension......I think it is about 30.5 to 31" but not sure. I don't know how to upload an Xcel file so it is just a picture.

09-23-2020, 10:51 PM	#7
Pro299 Junior Member Join Date: Jul 2014 Location: Huntsville, AL Posts: 75	Re: Tire Sizes....??? cj847 I can tell you the max must be more than 31 because I have 31X10.5X15 on stock height and it fits fine (and looks just right IMHO).

09-24-2020, 05:40 PM	#8
bigmac73 Senior Member Join Date: Mar 2012 Location: Chesapeake, Va Posts: 1,275	Re: Tire Sizes....??? 40 years ago in high school I ran a 32 x 11.5 x15 on a 72c10with stock suspension and had no issues __________________ Mike 72 C-10 Cheyenne off frame resto and Upgraded to 4 wheel disk, Tilt, Dakota Digital Dash / Rear slider. 421 SBC / TH350 3000RPM Stall Progression Ignition /Holley 750 DP/3:73 gear Eaton Limited Slip unit / 2 1/2 exhaust glasspacks



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