New Holland 98d Series corn heads

The Calmer upgrade kit solves many
of the mechanical problems with the
John Deere 40 and 90 series corn heads.
The kit enables your corn head to perform
better than new and a at a fraction of the cost
of a new or chopping corn head.
100% satisfaction guarnteed!

BT Chopper Stalk Rolls

Through the integration of multi-length blades,
Calmer Stalk Rolls have a patented “open window”
feeding chamber, which guarantees the efficient flow of cornstalks into the row unit to become processed into “confetti-like” pieces by 20 razor-sharp blades.

Multi-Zone Beveled Stripper Plates

Our patented stripper plates have a wider front opening to help prevent the bulldozing of cornstalks when slightly off the row. The beveled stripping area emulates the bottom portion of the corn ear to help reduce butt shelling problems and trash intake.

Slow Down Kit

calmer’s patented “slow down” kit includes a new drive and idler sprocket combination, which slows down just the gathering chains by 25%. This reduces trash intake, decreases kernel loss and increases the longevity of the sprockets and chains.

Grass Knives

Calmer grass knives are designed specifically for
the bt chopper’s redesigned nose cone and
helps prevent the back wrapping of grasses
along the waterways or in heavy vegetation.

John Deere 40/90 Upgrade
Kits Explained

Follow along with Marion as he explains the Full Calmer BT Chopper® Upgrade Kit offered for the John Deere 40 and 90 series corn heads. He describes in detail how the Calmer Upgrade Kit is one of the most advanced corn head systems in the industry that will note only enable your older John Deere corn head to perform better than a new head, but also make you more money by reducing a pass across the field, eliminating the chopping of stalks, improving planting operations, and increasing yields. We guarantee your satisfaction or your money back! 


follow our recommended steps for maximum performance

Step 1



Reliable stalk rolls are critical to a top-performing corn head. That’s why Calmer invented the World’s Only All-Weather Stalk Roll™ known as the BT Chopper®, which is the only roll in the industry with a patented “open window” feeding chamber for the superior feeding and processing of stalks in all crop conditions. 

The 10 razor-sharp knives on each stalk roll cut, chop and shear cornstalks into confetti-like pieces for accelerated decomposition. As a result, you’ll be able to reduce a management pass across the field, improve your planting experience and increase yields. Calmer Grass Knives match the curvature of the  BT Chopper’s® redesigned nose to  prevent the back wrapping of grasses.



multi zone beveled stripper plates from calmer features

“They work just as Marion described – true facts! Saves those small ears you would lose with OEM deck plates and now we have no butt shelling. Calmer’s rolls/kits gets rid of all the husks and now just ears going through the machine.”

Lyle Schilpp

Farmer, Rock Falls, IL

Reduce Butt Shelling and Decrease Intake of Material Other Than Grain (MOG) aka “Trash” Into Combine

Calmer’s Patented Multi-Zone Beveled Stripper Plates have a wider front opening that helps minimize the bulldozing of cornstalks when not fully aligned with the row. This wider retrieving area is manufactured straight to reduce ear wedging problems and beveled in the back stripping area to allow the stalk rolls to engage the ear shanks, leaves and husks, which significantly reduces trash intake into the combine. The patented beveled edge emulates the rounded bottom of the corn ear to help reduce butt shelling problems by displacing the energy around the base of the corn ear.


Slow Down Kit Chains and Sprockets 

“I have been using Calmer Chopper Rolls and trash reduction kit since 2010. Recently traded heads and the first thing I did was remove brand new JD rolls and put Calmer Choppers on. Since I started using Calmer products I’ve had 5 neighbors update their corn heads to Calmer product!”

– Randy Warner,
Rock Rapids, IA

By slowing down gathering chains by 25% with Calmer’s smaller 6-Tooth Drive Sprockets, trash intake can be reduced by an average of 61%. Calmer’s larger 9-Tooth Idler Sprockets improve the chains’ grabbing ability in both normal and adverse crop conditions and allows for a standard-size gathering chain to be used. This new-and-improved, non-greaseable idler sprocket is solid-steel and has a replaceable bearing for increased life and lower maintenance. Longer-lasting Chrome-Pin Gathering Chains are sent with all Slow Down Kits.

Big picture Economics

Follow along with George as he explains the cost economics of maintaining his corn head with BT Chopper parts.


 No Feeding Chamber

No stalk roll will perform properly without a feeding chamber in the entry area. All factory John Deere rolls have the same length flutes and therefore a continuous overlap in the entry area, which creates a wall of rotating steel and prevents the the entry of cornstalks.

Mechanically, this flawed design results in the premature wear in the first few inches of the stalk roll, while the remaining length of the blades stay in “like new” condition since stalks cannot travel further up the row unit.

Cornstalks CANNOT engage with factory rolls or become processed due to the continuous overlap in entry area.


Patented “Open window” Feeding Chamber

Through in integration of multi-length blades, the Calmer BT Chopper® Stalk Roll is the only stalk roll on the market with a patented “open window” feeding chamber, which enables cornstalks to travel efficiently into the row unit to become processed.

This design performs in all crop conditions, guarantees the traction of stalks for processing, results in longer stalk roll life, reduces low ear snap, and prevents the bulldozing of stalks at the end rows.

Cornstalks EASILY engage with Calmer’s patented “open window” feeding chamber to become processed.



 Limited Residue-to-Soil Contact

Straight-fluted knife rolls for John Deere 40 and 90 corn heads have too much overlap in the entry area, which prevents cornstalks from engaging properly with the flutes to become processed. This hesitation results in stalks and ears passing below the corn head without being managed.

Failing to properly process cornstalks prevents residue-to-soil contact, leading to the immobilization of important nutrients on the soil surface, slower degradation rates and leaves a wet mattress of residue in the spring.


Cornstalks failed to enter the knife chamber, resulting in little residue-to-soil contact and slow decomposition rates.


10 intermeshing Razor-sharp blades

 Superior Residue to Soil Contact

During rotation, the shortened flutes on the Calmer BT Chopper are timed to create 2, 4-inch feeding chambers for an efficient handoff of the stalk into the 17 1/2-inch knife chamber to be processed.

In the knife chamber, 20 intermeshing, razor-sharp blades cut, chop, and shear cornstalks into confetti-like pieces. This process exposes the pith of the stalk and places the residue strategically over the row for superior residue-to-soil contact, accelerated decomposition, easier planting and higher yields!

Cornstalks are easily engaged and processed for superior residue-to-soil contact and rapid decomposition..



Factory straight stripper plates are not formed to match the natural shape of the bottom side of the corn ear, which causes kernel loss upon impact by displacing all the energy on one kernel. (see image below)

Also, because these plates don’t match the curvature of the ear leaf, the ear shank cannot get close enough for the stalk roll blades to grasp and process it at the corn head. This results in the husk staying attached to the ear and sends it and more material other than grain (MOG) into the combine.


Straight stripper plates don’t emulate the bottom portion of the corn ear, increasing butt shelling and trash intake.


Patented Multi-Z Beveled Stripper Plates

Calmer’s Patented Multi-Zone Beveled Stripper Plates are straight in the front retrieving area to reduce ear wedging and beveled in the stripping area to allow the stalk rolls to engage more ear shanks, husks, and leaves, reducing trash intake by an average of 33%. These beveled stripper plates have a weld hardened surface for extended life.
Calmer’s Multi-Zone Beveled Stripper Plates emulate the rounded butt of the corn ear. This does a better job at displacing energy, which reduces butt shelling.


Calmer Beveled Stripper Plates push more kernels toward the cob, reducing butt shelling and trash intake.


Excessive Gathering Chain Speed

With genetic enhancements, today’s corn hybrids are taller and drier and therefore more brittle during harvest time. Prior to 2008, corn heads utilized row units with speed ratios from the 1960s that used fast gathering chain speeds. These fast gathering chain speeds often cause the gathering chain lug to shear or break off the top of the plant before the stalk rolls have a chance to pull it below the stripper plates. The gathering chain lug then takes the broken portion of the plant and pushes it inot the cross auger, eventually resulting in a LARGE PILE OF FLUFF.



patented slow down kit

Calmer’s Patented 6-Tooth Gathering Chain Drive Sprocket slows down the gathering chain by a full 25% and reduces trash intake by an average of 60%! This allows the stalk rolls to make additional revolutions and make more of the plant disappear below the stripper plates before the gathering chain lug can break it off. We also recommend replacing the factory 8-tooth idler sprocket with Calmer’s Patented 9-tooth idler sprocket (heavy-duty solid-sealed sprocket with replaceable bearing) to reduce wear on the idler block and increase the chain lug’s grabbing ability in down corn.

Calmer’s patented drive and idler sprockets help reduce the amount of trash going into the combine and prevents large piles of fluff from accumulating on the corn head.

gathering chain speed modifying sprockets

Get MORE than you bargained for this fall with Calmer’s BT Choppers® and Residue Management Upgrade Kits

With Calmer Upgrade Kits, you’re getting more than just corn head parts, you’re getting a peace of mind that your residue management and corn head problems are solved for good during harvest. 


Agronomic and Mechanical Advantages

Mechanical Advantages

    • Compatible with all Tillage Systems
    • 25% Less Hp Needed than with Chopping Heads
    • Superior Cornstalk Flow to Engagement
    • Better Ear Separation
    • Less Tire Wear
    • Less Butt Shelling
    • Increased Harvesting Speeds (Achieved through a combination of installing Calmer® products and proper combine settings)
    • Lower Spread Load

Agronomic Advantages

    • Unmatched Residue Decomposition
    • Warmer Soils
    • Drier Soils
    • Increased Earthworm Populations
    • Reduced Nitrogen Penalty
    • Easier Planting
    • Higher Yields

Still not convinced?

Look at the Benefits on The Ground

Read the testimonials, or review the scientific studies – residue is value returning to the soil.  Calmer BT Choppers speed soil renewal and health.