18.4-30 vs 16.9-34

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There is an industry accepted dimension for an 18.4-30 tire with a +/- tolerance allowed. If there wasn't one manufacture could make an 18.4-30 tire that's 40" tall and another could be 72" tall. That is NOT how it works.

That same +/- tolerance also applies to metric size tractor tires. I have 3 tractors here with different brand 520/85r38s on them and spec for all 3 brands is within 1.5" in height. I also have 3 tractors with 20.8r38s of various brands and there is 1.3" in height variation between them.

If what you believe was true all 3 of my metric tires should spec the same height.... but they don't.
With over 20 years of daily hands on experience and training from multiple different tire manufacturers you are not correct.
Ag manufacturers as well as tire manufacturers own printed materials also say you are wrong. There is no accepted side wall spec . In the old tire sizes . Doubt this check the height of a 14.9-24 pivot tire compared to a 14.9-24 tire for a rear wheel drive tractor to a 14.9-24 front fwd tire to a 14.9-24 backhoe tire.
Here is John Deere document on tire sizes and why they went to the metric system for ag tires.
Please note the following text that is within the above ducument


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There most certainly is an "accepted dimension" for the "old" tire sizing. If there wasn't it would be impossible to ever buy a different tire as there could be nearly unlimited difference in height. I've never seen a 9.5-24 that's 30" tall or one that is 80" tall, everyone is between 41 and 42" tall because that is what the "accepted dimension" is for that tire.

To use your example of a 14.9-24 I looked thru 20 different tire specs everything from pivot tires, R4 industrials, turf tires, Nokia snow tires, to multiple R1s and there was 3.3% difference in the height.

I also did the same for about 10 different 520/85R38 tires and there was 3.1% variation.

I dont care how much of an expert you think you are. The numbers and % of variation tell me that metric size tires aren't very much closer to their "actual" size.

On that now I'll bow out of this cluster. I'll still take the 18.4 tire any day of the week.
Believe what you will. I will continue to believe the training and knowledge I have gained for over 20 years of daily first hand knowledge and training by many different tire and vehicle manufacturers.
I have seen in person first hand over a 6 inch height difference between a 14.9-24 irrigation special and a four ply rating 14.9-24 r1 also have seen additional 2 inch difference between a that and a 14.9-24 8ply rating fwd tire.
Believe what you want . I will believe the training and personal experience I have received and the written documentation from tire and ag manufactures including some I posted here.
And I will believe the information provided by the tire manufacturers to me when I buy them and install them for customers.

My supplier lists over 40 14.9x24 tires in all flavors of ply ratings and tread patterns. Out of all 40 of those tires the smallest is 47.5" and the biggest is 49.2". Guess I'll stick with a reputable supplier who supplies tires that are held to the industry standard.

Anyways have a good day. Ha
So that must mean Firestone must be one of those non reputable manufacturers?who don’t build tires to your non existing “industry standard”
Directly from their spec book.
Put a 47.5 inch tires on one side and the 51.9 inch Firestone on the other and let me know what happens.
John Deere must be as unreputable as Firestone since they are one of many who have publicly stated and in this case put in their documents the reason that ag went to metric sizing is to increase consistency that is required on newer fwd ect equipment.
Guess Titan who also manufactures Goodyear branded ag tires isn’t reputable either. Both their hi-power lug and their hi-traction lug are both in excess of 50 inches and one exceeds 50.5 inches and the other is 50.4 if you combine both their good year line and their Titian line they list at least five different tires in excess of 49.5 inches.
I don’t know about anyone else but I consider Firestone and Titan/Goodyear Near the top of my list of reputable ag tire manufacturers. But to each their own
R-2 Deep tread spade grip rice tires share the same carcass but the increased tread depth gives them height. All manufactures I've ever seen don't recommend mixing R2 deep treads with other tires. R2s are in a class of their own.

In my 18 years of wrenching on tractors and buying and installing tires I've never seen a set of R2.

Manufactures can publish anything they want. My experience and the data from those manufactures shows clearing there is a nearly the same variation in tire heights in the metric / "old" style. I have 3 sets of metric rubber in my shop same size but different manufacture and they are ALL DIFFERENT dimensions.
Manufactures can publish anything they want.
So from the GY book is that .3" higher going to be noticeable? I'll still go with the 18.4 footprint for any sort of stability, only take a 16.9 of I needed to cultivate or spray row crops.

Metric sizing doesn't change anything. Actual tire dimensions vary a bit between manufactures. There is no set standard dimebsionsfor any given tire size.
So wich is it you quote directly from numerous cherry pict data from manufacturers to support your claims and act as if published manufacturer data is the be all and end all. But when that same published manufacturer data is used to prove you are wrong suddenly manufactures can print what they want.
At one point you claim there is no set standard dimensions for any given tire size. Then you argue that there is infact a set standard and any manufacturer that doesn’t use it is not reputable . Then when with documentation from some of the the top manufacturers own data that shows there is wide variation in old sizes and documentation from John Deere that says the reason for metric sizes in ag was to increase consistency in sizes . You argue there isn’t a set standard size.
You have flip flopped your opinion in this thread more than a stack of pancakes.
Cant be both

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