Most combines still roll off the assembly line with dolly duals (unless they’re sporting tracks). However, farmers who want to avoid downtime during harvest may want to upgrade to Keltgen Straddle Duals (formerly Kirchner Straddle Duals).
Dolly Combine Duals: A Downtime Driver Due to Cracking
- Factory OE option
- Intended to straddle the rows
- Prone to cracking
- Can fail under stress (especially with tank extensions)
Most new combines are equipped with dual wheels up front. (Unless someone ordered one with massive single floaters or tracks.) We refer to these OE setups as “dolly duals.” In most cases, they roll off the line with two-inch spacers that allow the machine to straddle the rows. If harvest turns muddy, these narrow spacers can be a headache in the form of mud-plugged wheels. Some operators choose to switch to five- or eight-inch spacers to improve their duals’ performance in wet conditions. However, in this setup, the tires are no longer straddling the rows. Tire options with OE dolly duals typically range from 480/80R38 (18.4R38) to 650/85R38.
The #1 Reason to Replace Factory Dolly Combine Duals: Uptime
There’s one big problem with dolly duals: wheel failure due to cracking. To make matters worse, the failure likely won’t happen in a clean shop near tools: Wheels like to fail on the far end of a muddy field. In the dark, to boot. Cracks generally start at the bolt holes and work their way out toward the bead. The initial small cracks can be hard to operators to spot; the inside dual on the auger side of the combine is the most common wheel affected by cracking.
If a customer calls with this in-season emergency, you'll probably have to source a replacement OE wheel fast. Maybe you have a used one on your lot you can load on the service truck pronto. However, you want to call this customer back after the busy harvest season and offer him a permanent solution to cracked OE duals: Keltgen Straddle Duals.
Factory Wheels + Non-Factory Combine: Asking for Problems
If you're investigating a farmer's combine wheel woes, there are a few pertinent questions to ask: Have you added a hopper extension to the combine? Have you purchased a wider head? Factory duals have a tough job to do on a factory-spec combine. If someone has added bin capacity or a heavier head, the tires and wheels have an even tougher task under the extra load. A farmer might be exceeding the load rating of his tires; and the wheels may not have been designed to carry the extra load.
If someone is operating a combine, such as a Case IH, with 20-hole wheels opposed to 10-hole wheels, the wheels are especially susceptible to cracks. Since the bolt holes are closer together on a 20-hole wheel, there's less steel between them to stiffen the wheel. This makes the steel more prone to flexing and cracking.
Keltgen Combine Straddle Duals Eliminate Cracking Issues
- Built to exceed OE specs
- Eliminates most cracking issues
- Better flotation with larger tire sizes
- Row spacing from 20”–38”
- Two bolt circles
Want to help your customers avoid the hassle of a failed wheel in a dark, muddy field? Turn to Keltgen Straddle Duals—a continuation of Kirchner's Straddle Dual design, which has been proven in the field for more than 35 years. Straddle duals experience far fewer cracking issues thanks to their beefed-up design. Each set of straddle duals uses two bolt circles (in place of the dolly duals’ one set) to dissipate the stresses placed on the wheel over a much larger surface area. The inner bolt circle bolts the inner wheel to the combine hub; the outer bolt circle fastens the duals together. Both the centers and rims of straddle duals are made from heavier gauge metal than OE duals as well.
Fewer Combine Wheel Failures and Mud Issues
Because of their beefier heritage, straddle duals are a more expensive option. (You’ll often need to add frame extensions to the combine as well.) But it's important to remind your customers that they're investing in uptime. How much would a wheel failure cost in terms of lost time and productivity? (Wheels aren't the easiest thing to fix in the field.) As we’ve said above, straddle duals experience way fewer cracking issues when compared to OE duals. And with straddle duals, operators will have 10 to 12 inches of clearance between the wheels for better mud flow in wet conditions. (Mud scrapers would be a smart investment as well.) Typical sizes with straddle duals range from 710/70R38 to 800s.
The larger tires and wheels help a combine float through wet fields and also have higher load capacities. A farmer may be able to float through wet spots that his OE duals would have sunk away in. And a secondary benefit of increased flotation is better fuel economy. The more a machine sinks, the more fuel it burns to climb out of its own ruts!
Even Tougher: NEW Keltgen Straddle Dual HD
- 20% thicker steel on main wheel over O.E.
- A one-piece spun flange and tube eliminates welds that commonly fail on regular duals.
- More holding power with larger diameter tube/flange and 0.75" thicker threaded ring (on 20-hole wheels).
- Bead flange reinforcements on main wheel.
- Durable powder coat finish.
Keltgen’s Straddle Dual HD is a new spin on combine duals, which we’ve designed specifically for class 9 and larger combines. Whether factory stock or packing a larger hopper extension and folding head, these massive machines can be tough on wheels. With thicker steel and stronger construction, you’ll pay more up front to roll with HD straddle duals. But ask yourself, what does downtime cost your operation? If you’re interested in protecting your harvest uptime and want to roll with wheels that will withstand fall’s toughest conditions for seasons to come, invest in Keltgen’s Straddle Dual HD.
Call Keltgen to Keep Your Harvest Rolling
Harvest isn’t too far away from hectic in the dictionary, and with good reason. The last problem any farmer needs when racing the weather is a wheel failure that brings the entire operation to a halt. Want to help your customers skip this late-season headache? Call Keltgen Wheel (or fill out our contact form) and switch them over to straddle duals. Virtually no cracking issues. Better flotation & fuel economy. Straddle duals are Forged to Go Further.
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