When it comes to a tire/wheel conversion, step one is to determine the goal or the need of the equipment. The large majority of tractors in the 100 to 400 hp range are set up to go between 30 inch-wide rows. When moving from a standard size tire to an IF/VF tire, manufacturers recommend a wider wheel to maximize the benefit these tires offer for weight carrying capacity and lower air pressures. This is the method I used. Your email address will not be published. See the following calculation: It is very important you keep this in mind when are converting one size of tire to another, or in some cases, even between tire manufacturers. A yellow crayon mark was placed on the top of the tires for easy revolution counting while driving. The current size is 8-16 Firestones. 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. Front: 9.5-20 (6PR), Rear 13.6-28 (6PR) U60. More torque can be sent to the wheels in first gear than in fifth gear because first gear has a larger gear-ratio by which to multiply the torque. 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. The chart below has popular 5 Step MFWD tractor RCI 48 480/80R50 rears and RCI 43 420/85R34 fronts, showing alternate wider and narrower rear and front sizes highlighted below. But what about 20” rows or bedded vegetable crops? The rolling circumference is the distance in inches that a tire travels in one revolution. David Graden: Operational Market Manager – Agriculture. The front tires must always turn faster than the rear tires as they are smaller and need more revolutions to cover the same distance. Changing tire sizes on 2-wheel drive tractors is straightforward. Requirements for different tractors are individual due to the variation of technical data of a specific tire size produced by different manufacturers. 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. If both tires on an axle is changed, there should be no problems. The transmission must be geared so that both fronts and rears turn at basically the same speed, since the fronts will turn more revolutions. If the fronts are too small, the rears will push the fronts (lag). For four-wheel drive tractors, dual tires increased the pull/weight ratio at a given slip level when compared to singles. Of course, more tire width and more section height normally mean more air volume = load capacity at the same inflation pressure. Many tractors have special requirements. favorite this post Jan 6 Case International 685 Tractor $24,500 (wau > Iola) pic hide this posting restore restore this posting. 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. When selecting tires for your MFWD tractors, you want to make sure to maintain the proper ratio of rolling circumference for your tractor. Ken Brodbeck, VP of Technology. Remember, tires are considered part of the tractor transmission. Tire sizes can be changed on full time 4-wheel drive tractors. For the front tires to pull successfully and produce the right amount of pulling power with the right “slip” to stay within the tractor gear ratio, the proper tire slip needs to be between 1% to 5% = “positive slip”. 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. The RCIs in the tractor´s handbook can give 2 different kinds of information: Example: The RCI ratio between 41 on the front and 46 on the rear is 5 (46 – 41= 5). It can be worth every penny you invest, and then some. Either I didn't explain myself correctly or you didn't read what I wrote. 4. Insufficient overall tractor weight for the horsepower is one of the major causes of power hop. However, with front wheel drive tractors (MFWD) the relationship between the front and the rear axle, called interaxle ratio, must be maintained in order to have the best traction performance and to avoid transmission issues. Tire/wheel conversions for traction reasons is not very common since these conversions would likely be to a narrower tire that will increase traction but also increases ground pressure along with compaction potential. 1) Tire size – Each standardized tire size has theoretical calculated dimensions called nominal values. 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. Failing to find anything in print for the YM1401D front to rear gear ratio, I decided to take Scotty's advice and just measure it. Lastly, seek out all the options to really determine which makes most sense. If you can’t harvest your crops due to wet soils you probably need to convert your combines to a flotation setup. These dimensions allow for +/- tolerances and depending on the manufacturer’s tire brand, the same tire size may have a different RC. U70. This chart is based on a drive gear of 1:1 at 65 MPH using a manual transmission. These tractors have the same sizes of tires all the way around like a 4-wheel drive truck. On the other hand, if a tractor operates part time or is on road often, lower lead values may be considered. 1 is an RCI chart showing the different sizes and their perspective RCI’s. The front tire mark should be slightly past one revolution. Nick Phillippi: National Product Manager. There are several situations when a farmer should consider converting his current wheel/tire setup to an alternative configuration. Lift the tractor off of the ground and mark both the front and the rear tires. This could change some due to the type of implements used. If you need assistance with this, all Michelin Ag reps are equipped with the tools and knowledge to walk you through this. Select tires appropriate to the tractor's top speed. 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. It is acceptable to increase or decrease the overall diameter on the rear tires, but the front tires will also need to be changed. Converting tire sizes to reduce compaction can help by reducing ground pressure from your equipment. What´s behind the RCI values? If so, be sure the investment will pay out over the normal operations and normal conditions that you will be farming in. For example, if the formula result for a specific tire size and brand is 47.5, it would not have an RCI (for RCI 47 you would include the range from 46.8 to 47.2 and for RCI 48 it includes from 47.8 to 48.2). If you run bias tires by chance you can make drastic improvements by switching to the same size in a radial tire. Will the Michelin 420/90R30 and 480/80R46 Agribib 2 give an acceptable lead? Basically, your tractor is designed around a very specific ratio between the RCIs of your front and rear tires, so to avoid excess tire wear or even destroying your transmission or transfer case, you must change the front and rears in the same percentage. https://www.titan-intl.com/en/resources/Lead-Lag-Calculator. From the manual, obtain the rolling circumference of the tire desired for the rear wheel. You have an option to compare two additional tire sizes to the base tire. For instance, are you operating at the optimal inflation pressure? Typically, a farmer wants to produce the highest yield with the best quality at the least cost of production. Front tires typically are spinning 1%-5% faster than the rears. Scott Sloan: Ag Product Manager / Global LSW. Multiply this number by the rolling circumference "RC" (get from published tire data) of the front tire size. It would be nice if manufacturers would list the Front-to-Rear Overdriven Ratio in the tractor specifications but alas, most average SCUT & CUT buyers wouldn't know what to do with the information and dealer salesmen would have even less of a clue what it meant or how to explain it to a customer. 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. 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). Front: 11.5-20 (6PR), Rear 14.9-28 … Fill in all entries except the one you want an answer to (in green section). Conversions are expensive and they need to be done correctly to get the most benefit you can get. Harm-Hendrik Lange: Customer Solutions Engineer for Continental Commercial Specialty Tires (CST). The permitted front wheel lead value is between 0% and +6%. The Kubota L2500 is a 2WD (L2500F) or 4WD (L2500DT) compact utility tractor from the L series. You need to compare the likely savings to the cost and really see if the payback will be worth the payment. 2) Tread pattern – A R-1 tire’s RC is smaller than its R-1W counterpart of the same size and the same brand. 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. Tyre size. Although there can be benefits to switching to taller or wider tires, they are not always the best choice. According to the RC, each tire is then placed in a RCI group. Always contact the tractor manufacturer to be sure. Equipment like sprayers (same size tires all around the equipment) or equipment with hydrostatic drive (like combines) are not affected by mandatory equivalent rolling circumference when changing tire sizes. 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 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”. Most tire/wheel conversions are done to gain footprint or increase tire volume (actually, they’re both the same thing), lowering air pressure and thereby reducing compaction. 2. Each RCI group has a logical, even progression of RC where each RC is 5.4% larger than previous one. Practices around the world differ based on crops grown, soil conditions, moisture and. 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