Titan offers an online lead/lag calculator to assist in the selection of tires. https://www.titan-intl.com/en/resources/Lead-Lag-Calculator, Recommended Wheel WIDTH = BEST Performance, Michelin Offers Additional Sizes to AG Spreader Line, Michelin Introduces New Agricultural Trailer Tire, You have an older Ford-New Holland 8970 equipped with 16.9R30 front tires and 480/80R46 rear tires, All tires are worn out & customer wants to replace them with Michelin Agribib 2, You look in the owner’s manual and find the tractor has a Mechanical Ratio = 1.35. Lastly, seek out all the options to really determine which makes most sense. 2. The transmission must be geared so that both fronts and rears turn at basically the same speed, since the fronts will turn more revolutions. Even if the MFWD is switched off on road normally, many tractors engage MFWD while braking, so high lead values may create high tension in the drive line. The first selected/entered tire size in the Tire Size Calculator is the base tire for a comparision to the other tires. It takes a certain amount of weight for a tractor to transfer one horsepower of energy from the engine to the ground — figure 130-140 pounds per PTO horsepower for front-wheel assist (MFWD) tractors and 95-110 pounds per PTO horsepower for 4WD tractors. Ken Brodbeck, VP of Technology. The following ratios are possible: 1.347; 1.392; Determine Tire Rolling Circumferences: This information must be obtained from the tire manufacturer's manual. Multiply this number by the rolling circumference "RC" (get from published tire data) of the front tire size. There is not a tire combination that is a “one size fits all” situation and often different operations would require different sets of tires for the same equipment. If you are looking for wider options, simply move to the right of the RCI 48 480/80R50 for rear tire options, then move to the right of RCI 43 420/85R34 for front tire options. If your tractor manufacturer alternatively allows you to increase to RCI 47 tires on the rear axle, the front axle should then also increase to 42 to keep the difference of 5 RCIs constant. The gear ratio on the typical MFWD ranges from 1.2 to 1.5; therefore, the proper setup should allow . Harm-Hendrik Lange: Customer Solutions Engineer for Continental Commercial Specialty Tires (CST). Tire Combination Guidelines, Up To 40 km/h (25 mph) The size ratio of front wheels to rear wheels must produce a 1 % to 6 % on tractors with PowrQuad and PowrQuad PLUS transmissions. The purpose of this would be to increase flotation, reduce soil compaction, lower fuel consumption or improve productivity. There are several situations when a farmer should consider converting his current wheel/tire setup to an alternative configuration. Most tractor manufacturers impose a mechanical lead of between 0% and 6%. Michelin Ag Important: whenever you change sizes on MFWD units, you must maintain the correct lead/lag by keeping in mind the RCI—the Rolling Circumference Index, which factors in the length on the ground of one full rotation and the height of the tire (don’t worry, it’s on a chart from your tire manufacturer). RCI 48 – 42 = 4 Step difference between front and rear tires. Some conversions are done to increase traction, reducing slip and thereby saving on fuel. What do a lot of people do? If the ratio between the front and rear tires change, it can cause damage to the driveline or reduce the wear life of the tire. Inflate Your Tires to the Correct Tire Air Pressure Overinflation Crushes Traction Performance. And what if the 360 hp Mechanical Front Wheel Drive (MFWD) machine is the big horse on the farm? Of course, more tire width and more section height normally mean more air volume = load capacity at the same inflation pressure. The MAXAM Ag tire catalog provides our tires’ RC, RCI and diameter specifications, to assist growers in determining any technical information necessary to support their equipment needs or potential tire size evolution. When selecting a new size or type of tire for your MFWD tractor, you must choose a front Solve for your Crawl Ratio. Who really knows until after the fact so consider the most flotation you can justify. 4) Load and inflation pressure – the RC specified for each tire size and model in the Tire Manufacturer Databook is measured when the tire is set at nominal inflation pressure and under nominal load. In this situation, a person may have to change wheels and tires when converting to radial tires. The tire circumference difference can theoretically be calculated by the RCIs or the RCI difference: For example, if the transmission ratio is 1.27 and the tire circumference ratio is 1.30, this would mean 2.36% lead for all tire combinations with 5 RCIs difference (1.30/1.27 = 1.0236) on this machine. The next higher RCI is always ~5.4% higher (+/- .2 % Tolerance), which means a factor of ~1.054.”, ALLIANCE, “If you are working with the Rolling Circumference Index group system, most MFWD tractors need to have fronts and rears that are 5 steps apart in the RCI, like a 50 Group in the rear and a 45 Group for the fronts.”, MAXAM, “If you have too much positive slip ratio (above 5%) you will have “excessive” work by the front tires pulling the rear tires equates to a loss of efficiency and higher fuel consumption. Adding tractor tire fluids to tires can negatively impact your tractor’s ride quality, especially when loading the rear tires, according to John Deere. The smaller front tires must travel faster to stay in the same ratio or time that the larger rear tires travel as they roll. Requirements for different tractors are individual due to the variation of technical data of a specific tire size produced by different manufacturers. For traction and soil compaction (and maybe also for optics), it’s recommended to always choose the highest RCI option the OE permits for the vehicle type, if there are not specific reasons to divert from this theory. For example, a front RCI 38 and rear RCI 43 (43-38=5) should have the same ratio as a front RCI 43 and rear RCI 48 (48-43=5). If the lead is very low, a tractor tends to go straight even with turned steering wheels, like it does when diff lock is engaged. This could change some due to the type of implements used. If both tires on an axle is changed, there should be no problems. The RCI is the rolling circumference or the distance a tire travels in one revolution. By entering the published rolling circumference of the front, rear or both and the gear ratio of the tractor it will tell you the target rolling circumferences of the tires that are needed to make the combination work. This is the method I used. This calculator will get you back to a ratio that's closer to your original. Although most tire manufacturers list rolling circumference for "larger" tires, few smaller rear turfs, and no smaller sized front turfs have a rolling circumference listed in any literature I have seen, (Firestone farm tire data book). You need to keep the change the same or at least within 2%. Going to a smaller diameter front and rear will work as well by selecting any tire from RCI 47 rear – 42 = 5 Steps. According to the RC, each tire is then placed in a RCI group. Determine if you already have the correct size, load index and type of tread on the unit before you move to make major changes. Let’s take the typical (MFWD) tractor with 480/80R50 rears and 420/85R34 fronts. This is the value referred to by some OEMs when they mention that the ratio between the front and rear axles is 5 steps. RCI is a good initial guidance when changing tire sizes but always check to have the right interaxle lead percentage to avoid transmission damage. Each RCI group has a logical, even progression of RC where each RC is 5.4% larger than previous one. Required fields are marked *, Designed by Elegant Themes | Powered by WordPress. Be careful: “close” may not be close enough, and it will be an expensive lesson. Smaller tires on a steering axle would allow for sharper steering angles. Each OEM publishes their recommended Gear Ratio for each model MFWD or MFWA tractor they manufacture. Whenever changing the fitment it is best to do the research and understanding what is currently on the tractor and what the RCI drop is from rear to front. Below is the MAXAM example of tires having similar diameters but different widths within the same RC or RCI to determine what is the best tire size suited to meet their field or crop production needs. By Joel L Nicoll in forum New Holland Owning/Operating, Family and Friends (Announcements & Notices), Changing tire size on a four wheel drive tractor, Trying to understand tire size and ratios, Tire pressure and front wheel drive lever for YM1601D. The front tire mark should be slightly past one revolution. An action plan to correct the compaction problem needs to be developed and implemented. Your email address will not be published. Growing the footprint in length will increase traction. In the above example, we took off rears that had a rolling circumference of 240.7 inches and replaced them with tires with rolling circumferences of 256.6 inches, a difference of 6%. This ratio will vary based on the downforce the implement exerts on the tractor’s rear axle. 3. Summary: When wheel/tire conversions are needed or wanted, you need to consider the best options that will help accomplish your goals. In addition to this “faster” front tire rotation (depending on the interaxle ratio), the front tires rotational speed needs to be 1 to 4% higher than the rears to assure the grip and to help with steering. At Alliance Tire, we prefer to provide the actual number of inches in the rolling circumference so you can be extremely accurate about your choices. The tire industry has developed the RCI (Rolling Circumference Index) system based on the OD of tires to assist manufacturers in the proper of selection of tire size combinations that will work. One of the key tools that is used to adapt or convert tires from crop to crop or grower to grower is the RCI or rolling circumference index. If you are running radials you may want to consider changing to an “IF” or “VF” type of tire of the same size. It’s suggested not to mix tread patterns. $45. In order to be able to consider all tires (including the ones out of the RCI spread) and to assure we have correct front axle lead; we need to use the actual Rolling Circumference (RC) of both tires and the interaxle ratio for that specific tractor model for our calculations. In other words, the front tires will turn more times as the tractors moves forward for every rear tire full revolution. MFWD tractors are 4-wheel drive vehicles with different sizes of tires on the front and the rear. order to select the tires that will adequately match the tractor’s front-to-rear gear ratio. Continental Agriculture North America That's the right concept....and the method that you are describing works for a 4wd car or truck or for anything where the front and rear tires are identical, inflated the same, and assuming that the loading of the front axle is the same as the rear. On a final note, when moving to a larger OD tire on a  tractor although the lead/lag is correct, it is important to verify that the tires will clear all the fenders, frames, fuel tanks and toolboxes to ensure the new tire will fit into that particular envelope on the machine. We may need wider tires, not those wimpy 480 mm wide things! A general recommendation is a 60-40% split, with 60% of the weight in the front. Is there another way that might be less costly for those small windows of need, like leasing another unit for short periods? If converting to these higher technology type of tires does not satisfy ground pressure reduction goals then you may opt for a wheel/tire conversion to tires with a larger air chamber. These differences could allow, depending on the tire brand and their tolerances, the same tire size from one brand to be included in one RCI group and another brand tire to be included in a different RCI group. Then reference your new tire diameter with your choice of RPM to find the new gear ratio needed to supply you with that RPM. For instance if the front tires are not changed the rear tires OD increases, this will put the tractor into a negative lead/lag meaning the rear tires will be pushing the fronts which could lead to the differential binding up and potentially locking up. You can match a group 49 with a group 44 or group 47 with a group 42 and they will work fine on the tractor. Ag tires are designed by size or footprint to fulfill following specific functions: As the Ag industry has evolved from animal driven to 2WD tractors to mechanical front wheel assist tractors (MFWD / MFWA), tires have also evolved in design, materials, functionality and performance. You have an option to compare two additional tire sizes to the base tire. Model. Combine conversions to a flotation setup is usually a drastic change to maximum flotation. Example: OE allows 1.0 – 3.5% lead. So how do we find the new set of tires and keep the proper front/rear tire gear ratio required by the tractor manufacturer? The thing that the end user needs to consider is the gear ratio of the tractor and the lead/lag ratio. But what about 20” rows or bedded vegetable crops? One of my favorite up-fitment examples for a very popular tractor setup is switching out 480/80R50 and 380/80R38 sets to VF480/95R50 and VF380/95R38 sets. Also be sure you understand the air pressure requirements at different operating loads and speeds and determine if you are going to be able or willing to make changes on air in the field. The Ford 2120 is equipped with a 2.3 L four-cylinder diesel engine and one of two transmissions: gear type transmission with 12 forward and 4 reverse gears or power shuttle transmission with 12 forward and 12 reverse gears. To optimally exploit the four wheel drive of a tractor, the value of the front wheel lead should be between +1% and +5% (ground speed front tyres > ground speed rear tyres). If the lead/lag is not correct there can be issues with the tractors performance. These tractors have the same sizes of tires all the way around like a 4-wheel drive truck. Alliance Tire Americas, James Crouch, National Product Manager — Agriculture. Tire Rack has offered a tire shaving service that has been primarily used for preparing competition tires for racetrack use. Torque is the twisting force that the engine produces. The large majority of tractors in the 100 to 400 hp range are set up to go between 30 inch-wide rows. Every FWA tractor has a "front-to-rear gear ratio" and the manufacturer states this in it's manuals or website info. This additional rotational speed is called front axle lead. A plumb pencil line was marked through the center of the left front and rear rims. Make sure they are built to handle the higher pressures and loads these tires will carry.”, Trelleborg Wheel Systems 4WD front tires must be properly matched to the rear tires (0 percent-5 percent overrun) to prevent excessive front tire wear, unnecessary powertrain loads, and overall poor tractor performance. This is where you have to be careful. The current size is 8-16 Firestones. The footprints are enlarged due to the sidewall deflection which will grow the footprints in length. Then determine if you’re doing all you can with what you have. We recommend the check to confirm the lead and acceptable technical data for each tire change individually. The standard method of size expression is relatively simple, but not as descriptive as metric.An example of tractor tire sizes expressed in the standard format would be “14.9-42”. The Kubota L2500 is a 2WD (L2500F) or 4WD (L2500DT) compact utility tractor from the L series. steiner 410 4wd Articulate tractor, blower ,mower $6,500 (wau > Wisconsin Rapids) pic hide this posting restore restore this posting. The various gears in the transmission and differential multiply the torque and split it up between the wheels. Be careful—even standard R-1 tires of a particular size from two different manufacturers—or different designs from the same manufacturer—may vary slightly on RCI, so double check them all. I'd like to install a little bigger tire since, from what I can see, the 8-16 tire size isn't very popular anymore. You might need to replace worn tires that don’t have enough lug depth left to give you the traction required or you may need to change your tire set-up. If the fronts are too small, the rears will push the fronts (lag). The difference in those two groups is 5. The Rolling Circumference Index (RCI) is a grouping of tires based on the rolling circumferences. Once that is understood it is relatively easy to identify sizes in the appropriate RCI that will work. We now take the rear tire size rolling circumference and divide it by the tractor gear ratio. Fill in all entries except the one you want an answer to (in green section). Titan International, Inc. (Manufacturer of Titan and Goodyear Farm Tires) This ratio is referred to as the gear ratio and, depending on the brand and type of tractor, is normally between 1.20 and 1.50. Find new Gear Ratio with new Tire Size: Now that you have your truck lifted, you want bigger meats. Each MFWD tractor must maintain a balance between “positive slippage” or front tires pulling, and “negative slippage” when the front tires are slower or lagging therefore resisting the push from the rear tires.
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