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 failures 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 spot; the inside dual on the auger side of the combine is the most common wheel affected by cracking.

Let's say you're in the middle of harvest and you have a combine wheel crack. You'll probably want to source a used wheel to get your operation up and running fast. That's a great way to get by for the rest of harvest. But after your crop is in the bin, you may want to call NTS Tire Supply and discuss your options to permanently fix the cracking problem.

Factory Wheels + Non-Factory Combine: Asking for Problems

If you've experienced 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 you've added hopper capacity or a heavier head, the tires and wheels have an even tougher task under the extra load. You might be exceeding the load rating of your tires; and the wheels may not have been designed to carry the extra load.

If you're 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.

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

One option to permanently fix cracking combine wheels is to upgrade to a set of straddle duals. Originally designed by Kirchner, straddle duals have proven their worth 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 remember that you'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, you 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. Your may be able to float through wet spots that your 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: HD Straddle Duals

• 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.

Our HD straddle dual 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 a set of our HD straddle duals.

Call NTS Tire Supply to Keep Your Harvest Rolling

Harvest isn’t too far away from hectic in the dictionary, and with good reason. The last problem you need when racing the weather is a wheel failure that brings your entire operation to a halt. Want to skip this late-season headache? Call NTS Tire Supply and we'll help you switch to straddle duals. Virtually no cracking issues. Better flotation & fuel economy. Straddle duals are ready to Drive Your Farm Forward.