dia. of tires

Does any one know the difference in dia. of 14.9-24 and 13.6-24.

I don't know of any standard for the OUTSIDE DIAMETER of tires. For example, a new 14.9-24 tire is often sized differently by different companies and may be sized differently in the same brand. All else being equal, the lowest priced tires are often the smaller, of course. I would suggest going to the web site of the brand you are considering and looking at the specifications of the tires with the tread, construction (bias ply or radial), and quality you are looking for.

Well the reason I'm asking is there is a set of used 14.9s advertised in the shopper and I run 13.6 on my fwa Case. He is asking cheap to free so I'm wondering if they will work for me. Tractor is used mainly on road without fwa locked in so I suppose differance would be neglagible.

(quoted from post at 08:06:06 09/22/10) Well the reason I'm asking is there is a set of used 14.9s advertised in the shopper and I run 13.6 on my fwa Case. He is asking cheap to free so I'm wondering if they will work for me. Tractor is used mainly on road without fwa locked in so I suppose differance would be neglagible.

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The 14.9s are considered to be an upgrade to the 13.6, and are made to fit on the same rim. Those tires should work out just fine for you, but in my opinion, the 14.9 and the 13.6 should not be matched up on the same tractor.

If I were in that situation, I would be thinking the same as you.

Should work OK...until you lock the front axle in.

It depends... 13.6's were something of a compromise tire on MFWD's because many times the front did not lead sufficiently however... a change to 14.9's will put the front lead just slightly over the acceptable range. It should fall in the 1-5% range. Depending on the transfer box your tractor has... it will probably hit just under 1% with the 13.6's and just over 6% with the 14.9's. At least that's the numbers I get on my Ford... but the Case may use a different ratio.
Another thing to consider is that many, if not all ZF transfer boxes were simple multiplate clutch setups rather than a dog clutch that was used by other manufacturers... and these multiplate setups always have ~some~ drag in them, even when released... so you're always going to have a considerable whine about it when going down the road... and that will be worse with larger fronts.
So... you may want to consult the tire data book that's found on the tire manufacturer's website (for that exact tire) and then get the drive ratios and calculate what the lead is now and what it will be with a change before you decide.

I've been thinking about the same changeover on mine but I'm a little reluctant to buy 2 grand worth of Michelin rubber when I don't know how well it will work.
I know a guy that has made this change and it works fine for him... BUT the tractor hardly ever sees asphalt.

Rod