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Comparing tire sizes and diameters

O

old

Well-known Member
Location
Camdenton Missouri
So my Oliver S88 has 14.9x38 tires on it. I also have this 15.5X38 on a bad rim and on my Oliver 77 I have 13.6X38 tires. Now granted my measure of them is not super accurate but should be close. The 13.6 and 15.5 both measure around 56-57 inches tall and the 14.9 measures around 61.5 inch tall. But yesterday I was talking with a guy who sells tires and he told me a 13.6 stands at 61.6 inch tall so if that is true why did the tire on my 77 measure out around 56 inches tall?? Or is it maybe each brand does there sizing different??
 
Yes it will some but so will air pressure. The tires on the 77 are on factory rim that came with the tractor. On the S88 the 14.9 tire is one the factory S88 rim and not sure if the 77 rim and S88 rim are the same as being how wide and hard to measure with a tire on them
 
Lift the good tire on the tractor and put a tape around the circumference. Divide that By PI and you will have diameter. Do the same for the other replacement. If they are within 2 inches, it is only a 1 inch tilt, that can be made OK by lower pressure in the tire that is too tall. If the tractor is used modestly, the continuous differential action would be no more, and maybe less than the slippage on the land side compared to the furrow side when plowing. Go for it. Jim
 
All this Oliver S88 is used for is to pull my NH850 round baler on around 14 acres of hay field twice a year in a good year. I'm trying to get by as cheap as I can for now and have a used 15.5X38 that I could put on in place of a bad 14.9X38. But at this time I cannot air up the 15.5 because it is on a bad rim and the rim it self could well fly apart as I was airing up the tire which of course as you know could be deadly. So I could do as you say but it would only be in the ball park so to speak
 
Here's a question for you. If I where to take a piece of rope and wrap it around the 15.5 and also the 14.9 and could use that to compare how close they where ti each other. Right??
 
And if they came out close to each other then it would also be safe to use the 15.5 with the 14.9 on the other side. I'd think as long as the 2 came out say 1-3 inch different it would not be enough to cause rear end problems
 
All this fuss over a couple inches of diameter. The differential is constantly going one way or the other as you turn one way or the other. If you were pulling a plow the upper tire would be spinning all day and under heavy load. Lots of older tractors with mismatched tires working every day, even if they are the same size they won't pull the same creating the same situation. I'm just not buying that it will be an issue. The bigger issue will be rim size because I think the 15.5 needs a wider rim.
 
you measure the circumference not the height. and the tractor has a differential just like any vehicle. that is the spider gears job to let one axle turn faster, same as turning and stepping on the brake and one tire will turn faster than the other. you have nothing to worry about. just an old wives tale it will hurt the differential. and different brands are different heights or circumferences. apples to apples.
 
use a tape measure or dont u have one. whats this rope stuff. like measuring a cyl. bore with a ruler looking for .010.
 
the only problem you will encounter is if you get stuck and let one wheel spin for an hr. with the other one stopped. now thats what hurts differentials. one wheel spinning for a short duration does nothing nor will a different size tire as the spiders are not turning fast enough to do damage that is the whole idea of having a diff. in stock car racing we used to weld the spiders solid so that both wheels turn the same going around the track and compensated with different tires sizes as smaller on the inside of track.
 
A metal tape measure is a whole lot harder to control then a piece of rope would be and I am doing this with one my 2 hands no help from others
 
Rich,

The differential should be fine at low speeds, as it will get enough lubrication. It will create wear on the pin, but no more than you use it, would probably never know the difference. The two tires will have different degrees of traction. The readings the tire guy gave you would be with no weight.
 
Yes after thinking about it a bit I figure since to bale with this baler I am driving like a drunk man as in going side to side over the windrows so the Diff. is always working as I turn back and forth to keep the hay feeding in evenly
 
Old, I'll give my opinion. The 14.9x38 tire has a much higher sidewall than the 15.5x38. I know money is tight, but I would not do it. Better off trying to find a set of used tires that are a match than what you are wanting to do here.
 
dont you have a chalk or marker? or use a heavy fishing line not the nylon stuff with a screw in the lug to tie the line to. do the same with the tape. got to be an injunuityer.
 
My plan is to use what I have on hand and make it easy. I plan to use baling twine and the screw thing will work with the twine but will not work with a tape measure or at least none that I have
 
i sure would do it if i was stuck and had hay to bale. you tell me then what your scared of. it happens every time with this differential posting stuff. lots of hear say repeated and then repeated till people start to believe its true. which is totally false. you read what i posted then think about it. we used to run the tow lift here on the ski hill will a W4 . one wheel was on the ground and the other one only had the rim on it to run the rope. sure did not hurt that tractor either.
 
I bought john deere 70 that had a 14.9 and 13.6 on it. I never really pulled it hard but never had a problem with it besides it looked funny.
 
The hay will get wet while you guys fool around with it. Just put it on and run it. Can change it later. WE had a 15.5 rice tire on against a 12-38 on an MD years ago and used it like that for several years. The same gears are in there now with no problems and we were using it on a 12ft disc at the time. Rice tires are a lot taller than regular rear tractor tires of the same size.
 
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