Ok Math guy's- Tire diameter vs Revolutions per mile.

[HammerDown]

Ray has 255/85R16 on his truck since new.
The odometer now reads 165K.
The revolutions per mile for a 255/85R16 = 655 R/M
The revolutions per mile for a oe tire 235/85R16 = 627 R/M
So, how many actual miles are on Rays truck...?

PS. 235= 31.7" tall
255=33.1" tall

 

[BJS]

Ray has 255/85R16 on his truck since new.
The odometer now reads 165K.
The revolutions per mile for a 255/85R16 = 655 R/M
The revolutions per mile for a oe tire 235/85R16 = 627 R/M
So, how many actual miles are on Rays truck...?

PS. 235= 31.7" tall
255=33.1" tall

Ray has 157 K on is truck for real his spedo is aprox 5% off (4.4657097289% to be exact)

 

[pafixitman]

Miles

Ray has 157 K on is truck for real his spedo is aprox 5% off (4.4657097289% to be exact)

Yep

157,946 if he has 165,000

 

[Mikes91]

Yep

157,946 if he has 165,000

Wait!!! That assumes he started with the oversized tires when the truck was first driven and stayed with them up till now...

Oh... you're also not including the extra revolutions due to peeling out or loss of traction while accelerating on wet surfaces!

... just trying to help with accuracy...

Mike

 

[timntools]

also left out the fact that the tire expands at higher speeds, and also leaves out that is shrinks during tire wear...

 

[Mikes91]

also left out the fact that the tire expands at higher speeds, and also leaves out that is shrinks during tire wear...

Ah, yes... but the tire contracts on cold days.

 

[Mike]

Is Ray travelling East~West or North~South and what time does he have to meet the train?

 

[F350camper]

Now Ray is really P.O.ed!! Based on the calculations here, he just found out he has over 7,000 miles left to reach his destination.

 

[argve]

Plus how many times did Ray change the air in the tires - old air travels less miles... Plus did Ray install helium in the tires - this will result in a lighter tire and will cause it to float down the road resulting in less miles registered on odo but will cause Ray to make up the 7k miles...


Ray you should know not to ask us questions like this....

Great post I love it!

 

[LUCKY_LARUE60]

How many times did he back up on my speedo it shows more miles......... Btw you shold change the air in the tires once a year as it get wore and causes adnormal tire ware, dirty side walls............... Jim

 

[Agnem]

Don't forget too, that in Pennsylvania, there are a lot of pot holes. There's a high probability that the tire actual free wheels in space for a few milliseconds, increasing driveshaft revolutions without adding to forward motion. Who knows how many miles, that may have added! :Sly

 

[flatlander]

Keep in mind also that different tires will have variations in sidewall flex at differing rpms. If he used a stiffer sidewall it would have lower flex to revolution ratios which would influence tire wear. However, if the stiffer sidewall was used in conjunction with a softer compound the flex to wear ratio would be negligible, but if a harder tire compound was used with a stiffer sidewall there would be less wear. However a harder tire will spin easier on lower friction surfaces negating any possibly advantage in the wear arena.

Mostly one must keep in mind the number of flapjacks stacked on the top of the doghouse, while counting the back flips flawlessly executed by grasshoppers in the nearby area.

 

[HammerDown]

good stuff...
and yes I alway's change my winter time tire air to summer time air, doesn't everyone

 

[dozer]

uhhmm....but I think everyone got the actual -answer- wrong!

Or did I just have too long a day??

I didn't run the calc for the % error, but the 4.*** sounds right to me. But I think he's got MORE miles, not less...

If I read the question right, the Odo -says- 165K.....but is geared for the -smaller- oem tire, correct? So each revolution of the tire that the odo has counted is actually covering -more- ground than the odo thinks. So the truck has actually gone MORE miles than the odo sez; not less...

 

[beretzs]

Yup, I agree, good catch, if you start with smaller tires and move to bigger tires, your speedo will be slow for given MPH, I have dealt with this alot since I was young, add big tires and a lift, your speedo says 65, but with a mild tire like a 33-35, you are likely to be running over 70 and probably closer to 75, so therefore, you will actaully have less miles on your truck.. Scotty