New truck tires question

[JamesCoste]

I have a 2002 Chevy 1500 5.2 liter V8 extended cab truck. My truck has 50,000 miles on it and I just bought new tires.<br /><br />The tires that were on it came as original tires and were smaller tires like 235 "something". The tires I had put on it were Kelly Pathfinder SUV 265 75 16s.<br /><br />How do these larger tires affect my spedometer? Are there other factors to consider?<br /><br />I love the new tires and the look that the larger tires have.

 

[NYMINUTE]

Re: New truck tires question

It should show slower than actual, but not by much. 2-5 MPH. I put larger on my Mountaineer same as yours and I show a difference of 4 MPH comapred to my GPS. I hear that the tire size may effect Anti-Lock brakes on some models, but nothing to support that.

 

[JB]

Re: New truck tires question

Non-boating Tech topic

 

[Bob_VT]

Re: New truck tires question

You can hit the dealership and ask to have the computer re-calibrated for the tire size. It is about a 5 minute job. <br /><br />Bob

 

[chuckz]

Re: New truck tires question

The difference between 235 and 265 is the width of the tread. The next two numbers are important. For instance 23570R16 means 235mm wide, 70mm sidewall height, 16" rim. If the profile of the tire changed (the 2nd number) recalibration may be necessary.

 

[dolluper]

Re: New truck tires question

Naa your fine your truck came with 235/75/16 all you did is went widder so you can race around town if you went to 70 you might have an issue a replacement for stock is a 225/70/16 for the hot rod look

 

[QC]

Re: New truck tires question

BTW, this data is usually available on the tire manufacturers website. The important spec is revolutions per mile, and it can actually differ between manufacturers of the same size. I would guess that Dealers can input just about any revs per mile spec. I know you can on Heavy-duty trucks.

 

[TenE307]

Re: New truck tires question

just for an FYI!<br />had a friend with extended warranty and got different that factory sized tires (next size bigger). went to go get some work done, and they said he modified the vehicle and no longer held up the extended warranty. i also have a banker friend and something like this happened when refinacing where they said odomoter reading was incorrect. no refinance!

 

[Bob_VT]

Re: New truck tires question

Update - it will not void the warranty unless it is on a GM vehicle with an allison transmission. I spoke to a tech in the shop and he stated it will have an effect on the speedometer but the serious side effect will be with the ABS.<br /><br />The ABS will not activate properly (either too soon or too late) but the computer is tied to the ABS. Having it re-calibrated is an easy job and even though it takes 5 minutes the customers get charged for a 1/2 hour labor. There are many customers who don't mind what it is doing to the vehicle and just leave well enough alone.<br /><br />It comes full circle to being an insurance issue if the re-calibration was done and the ABS works right no problem. If it fails to engage properly due to no calibration then the truck owner is responsible.<br /><br />Bob

 

[dolluper]

Re: New truck tires question

5 tons have allisons [auto's] not yours

 

[Mark42]

Re: New truck tires question

Actually, the second number is a RATIO of tread to sidewall. So a 235 70 16 is taller than a 225 70 16. It reads that the side wall is 70% of the tread width. <br /><br />So: <br /><br />A 235-70-r16 is 28.95 inches tall.<br />A 265-75-r16 is 31.64 inches tall.<br /><br />At 60 mph speedo reading, the actual speed will be 65.6mph. That is significant. At 70, it will be 76.6, at 75 it will be 82.

 

[dolluper]

Re: New truck tires question

Wrong way Mark Bigger is SLOWER in speed

 

[QC]

Re: New truck tires question

No, Mark is right. A taller tire (lower number of revs per mile) will be faster than the speedo reads (if it is not reset, obviously). If the revs per miles are 10% less (taller tire example) then the speedo will read 10% slower than actual vehicle speed.

 

[Mark42]

Re: New truck tires question

And as if those number I posted are not making an impression on you, think of this:<br /><br />At speedo reading of 1000 mph, your actual speed will be a whopping 1096 mph.

 

[chuckz]

Re: New truck tires question

Thanks for the correction on the tire sizing. My fellow workers say all I hear is blah, blah, blah, BOAT. I guess it's showing up here.

 

[TilliamWe]

Re: New truck tires question

Chuck, I forgive your error. You live in Patchogue, you can't be all bad!<br />(one of my favorite cousins grew up there)

 

[dolluper]

Re: New truck tires question

It's just not that easy as a bigger tire will be slower in speed on the speedo but the vehicles speed will be higher than the speedo reading there are factors that determine the amount difference between speedo and actual speed like trannie gear and rear-end gear depending on the ratio's you could be out 3 miles per hour at 85,so speedo would read 82 when your going 85 or could read 80 when acually going 88 You have to calculate all the factors Most tire shops have programs for this purpose so the tire will match the recomended about of error in speedo to actual speed

 

[JamesCoste]

Re: New truck tires question

Thanks all for the advice.<br /><br />I honestly believe that the truck is driving faster than the spedometer reads as several stated. When I'm in town, I'm not too worried about the speed difference. I do some interstate driving and that is where I am concerned.<br /><br />Sometimes I drive 4-5 mph over the speed limit on the interstate. I would then be driving 12 mph over. <br /><br />I'll call my Chevy Dealer to get a quote for the recalibration.<br /><br />I just called my dealer. They can only calibrate for up to one size tire increase and it will cost about $75. <br /><br />He said that the things that the larger tires will affect are: emissions, the transmission will shift differently, the spedometer, and the ABS.<br /><br />His recommendation was to get an "after-market" computer "thingy" that will do the calibration for the 3 tire size jump. I'll do some research. He said it was very easy to do the calibration. Hmmm.<br /><br />I don't want to mess up my truck, but I don't want to mess it up by leaving it alone either.<br />It's amazing that tire size can make that big of a difference!<br /><br />He recommended me look at some aftermarket

 

[QC]

Re: New truck tires question

Dolluper dude,<br /><br />You are right, all of those factors are part of the equation. Engine RPM, trans gear ratio(s), rear end ratio and finally tire size, but . . . if the others are left alone all that matters is the difference in revs per mile between the two tires that you are comparing. Once you know that difference as a percentage it stays consistent across all speeds with the only variable being that of the speedo's semi-flakiness by being a needle vs. a digital read-out.<br /><br />Trust me on this, I have been specin'g heavy trucks with as many as 24 forward gears and mutliple tire size options for over 25 years. Same rules apply to our little ole tow vehicles.

 

[dolluper]

Re: New truck tires question

Here you go at 60 you will be going actual 63.6 that is changing from 235/75/16 to 265/75/16 try this tire calculator from tire company<br /> http://www.discountpartcenter.com/tirecalc.html