Wi | This is something that's always bothered me from many perspectives. There is a reason for both ways, but I feel there's not enough people basing their decisions in tire choices based on data and rather "I heard/Was Told".
Before I type another novel, I'll point out some of the annoyances that cause confusion among others and lead to fights about nothing more than confusion of terms with tires.
1st, there are no "metric" tires. Every tire has an ISO size which includes a metric section width followed by the aspect ratio followed by a designation (ex: R=Radial) followed by the rim size in inches. Special factors may follow or precede that data but it is the core of it. I know i'm just the young guy, but the sooner people start talking ISO terms, the sooner things will make more sense to some people. Especially the numerous size questions posted on here, followed by two people arguing than an 18.4-34 worked for them why shouldn't the 18.4-34 work for the other guy, etc. Old school terms are great for history books, but if you walk into a truck shop asking for a 10.00-20 (ten hundred twenty) they are going to give you a tube type bias tire or ask if you are sure thats what you want. If you want a 10R20 you will get a radial tube type or get asked if you are sure thats what you want (again the confusion). If you ask for an 11R22.5 you will get a standard profile 22.5, if you ask for a 22.5 low Pro you will either get a 275/80R22.5 or be asked more specifically what you need as there are other options. Walking in an asking exactly for what you need will avoid confusion and get you going fast. Who knows maybe the guy at the counter is new and afraid to ask, you may go home with the wrong size. It's always best to know what you are buying no matter how much you "trust" someone, never hurts to double check.
I know its easier to just type 18R34 but the reason this causes confusion and issues on here often is due to the influx of lower profile tires. Many of these are from Europe as they were popular there before here. When you say 18.4R34 it implies you are talking about a standard profile radial which has an aspect ratio of 80-90%. These are referred to often as 85 series tires due to 85 being the average aspect ratio. That's great if every 18.4R34 is a standard profile tire, but they are not. In this specific case there are many 70 series tires which are one RCI group smaller. This is an issue in this size due to many people using it as an MFWD tire and needing to keep the size ratio the same to avoid issues.
It's more of a convenience thing than anything, it will save you and those around you time and headaches if you take an extra second to say the entire tire's ISO code just like you would getting car/truck tires, versus using older terms that may or may not be correct for your tire. Say it out loud to your wife, 480/80R46 (6 syllables). Now say 18.4R46(6 syllable if you say point, 5 without), did it take any extra oxygen? Was it harder? No. It does take a few more keystrokes, but saves many in the end. 25.4mm=inch, most know this but that can help you if you are ever lost. If you know a tires section width, diameter and rim size you can find the aspect ratio. No different than any other equation, you can always find the missing component.
Sorry for the algebra lesson, but I put this in a lot of threads where people are trying to compare tires with confusion.
2(Section Width*Aspect Ratio)/25.4+Rim Diameter=Tire Theoretical Diameter. You don't need to divide by 25.4 if you use inches for the section width.
Broken down for those who thought Algebra was a waste of time in school.
2(480*0.80)/25.4+46=76.2"
2(384)/25.4+46=76.2"
768/25.4+46=76.2"
30.2+46=76.2"
Enough of that, the reason I put all of that in here again about proper terminology is due to the variations among tires. If you put a "-" or an "L", I as well as others are going to assume its a Bias tire unless its on something new. If you put an R then it will be assumed to be a radial. If you do not put an aspect ratio it will be assumed to be standard tall. When people say "row crop" tires I assume 380-480 for rear and 320-420 for front as that is what most use. When people say "metrics" I assume 710-900. Something in between would not be a decent replacement for a set of duals on a row crop.
Obviously Row Cropping is a reason for using row crop tires. If you need to fit between rows then that's what you have to do. You can raise some good arguments about planting though, more on ground pressures later in my post.
Some of the statements I see being made make me wonder if people have driven a row crop tractor with large singles. Things like saying the ride on a dualed tractor is nicer, the compaction is lower, and the replacement costs due to wear are lower. IMO the ride on a set of 800s is far nicer than dualed 480s. I think a lot of people drive their tractors around set to 60" rows with the duals off and think "this rides like crap". No argument there, can't stand that, but large singles have a much wider footprint to reduce the rocking. To me the duals make the ride stiff and dont allow the tractor to rock enough when hitting bumps or corners. Our tanker tractor spends its life on the road so road comfort is important as is road wear. The wear thats been seen out of IF800/70R38 Axiobibs on the road versus dualed 480/80R50 Agribibs is the same or better when spending most of its life on the road. Based on Michelin's fleet pricing today I could replace two 800s for $3,200 less than four 480 Agribibs. Yes you can argue a fencepost costs more, but unless you run them over multiple times per year I probably would not base something as important as tires on a simple "what if" scenario. Our fields are littered with old fencelines, we clean them up though when we take them out. Had a pliers in a combine tire a few years ago that was repairable, can't remember the last "object" we've had in one otherwise. Even those we have, were repairable. The compaction issue however is a bit in depth and I'll talk about it later.
Europes road widths are mentioned. A lot of NA farmers like to "pick" on Europe due to their road regs for whatever reason. I personally am much happier driving something 3m wide than taking up 3/4 of a two lane road and needing the ditch. I realize the "I" states farmers and others in the plains have nice big ditches they can bale grass in, but ours are straight drop offs and not useable for our equipment when meeting others on the road. Meeting someone with a corn planter is a little different too, its only out a few weeks out of the year and its only going down the road a little bit, most of its time is in the field. Other things spend more time on the road than they do in the field. Some joke that NA equipment revolves around the grain farm/row crop operation and sometimes that mindset shows its colors on here, but things are changing a bit. You can argue that farmers should use trucks instead because they are better on the road, but then theres the issue of a truck not always been good off road. The bottom line is we are comparing Euro guys with big tires to NA guys stuck on duals. Euro tractors spend more time on the road, even if they didn't have laws I think many of them would still choose a tire option that kept them narrow. Width restrictions are making their way into the US, row crop farmers can laugh all the want but the day may come when they are driving a 3m wide implement as well.
Traction is one that I don't have much info on and can't say I've compared anything in a fair manner. I think the soil types and implement types play a role in the different opinions of traction between the two parties. Europe generally has wet heavy soils with more tillage being done while a lot of NA is hard dry no-till ground. The deep lugs an 45* bars on the larger tires are great for the wetter stuff, nice smooth road wear and ride but on true hard ground they do not always prevail. Evidently its not a significant advantage for enough of the market or someone other than Firestone would try to capitalize on the concept of a straighter bar. They always talked about how deeper tread wasn't as good either but have been discontinuing many of their R1 tires and keeping the R1W versions lately. I think implement type plays a role too. Most of the stuff in NA is trailed and doesn't really put a ton of vertical load onto the tractor to aid with traction. A lot of euro implements are mounted and put a lot of vertical load on the tires when working, this helps traction more than anything else can.
Keeping up with the Jone's is an important integral American tradition that I think fuel's the duals are better than singles idea. Some may get laughed at when at the coffee shop if they didn't have duals, others do it because grandpa did it. Some do it because the salesman says its the only way or they wont get any money for their tractor later on. I understand people wanting a backup tractor maybe to go down the rows, but why does that mean you need 2 or 3 backups? At some point worrying about the what if may not outweigh the advantages now.
Compaction is always a big topic. Planting "pinch rows" versus into the low pressure wheel tracks of a large tire is often debated as well. A lot of the results depend on the soil itself more than anything, but people have had good results both ways.
In regards to footprint, most people look at Gross Flat Plate which simply put with enough tires is the load(lbs)*inflation(psi). It's usually a little smaller than that, but it gets you close. The flat plate is just the amount of tire contacting the ground, it doesn't show where the high pressure points are. This is why even tracks can create as much compaction as tires under certain conditions. Most radials carry the most weight towards the sidewalls though so you can expect the ground pressure to be higher near the edge's of the tire. Knowing that, it makes you wonder about the pinch row situation again. if you plant a row between two 480's but the compaction is concentrated more towards the edges of those wheeltracks, are you maybe better off planting in the middle of an 800? Some on here have seen the results first hand and say it depends. Many speculate it just doesn't work that way, not doubting them but their statements never have anything to back them up really. With the low pressures available on modern IF/VF large volume tires it would be interesting to see something like an IF900/60R42 compared to dual 480/80R50's to see if one or the other offers a substantial yield benefit.
Theres plenty of logical reasons to go either way, but I think many people do not even consider large singles enough in the US. Especially when their tractor may spend its life on the road or never have any use as a row crop tractor. That said though, I don't think they can cure cancer or solve world hunger either. |
Dual Wheels - Why?
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