JMI 10″ Pneumatic Wheel Upgrade + Tow Handle for Wheeley Bars

Product Overview

This upgrade takes a JMI Universal-style Wheeley Bar off pavement. Six 10″ all-terrain pneumatic wheels replace the factory 2⅜″ hard-rubber casters and their standard hardware, and a tow handle assembly with the bracket matched to your leveling-screw size comes in the box along with all mounting hardware. The layout is two front swivel casters plus four rear wheels arranged in dual-inboard pairs, which keeps track width narrow while spreading the load. Fitted, the kit raises the scope approximately 3¼″ over the factory setup — less lift than the 5″ polyurethane upgrade despite the much larger tire, because of the pneumatic tire profile. Shipping weight is 35.0 lb. Made in the USA by JMI, part of the CXB Astro family.

Who It's For

This is a good match if the ground between where your rig is stored and where it gets used is not paved — a lawn, a gravel drive, a mulched path, sand, or broken pavement that the stock casters dig into. It also suits you if you travel to a dark-sky site and need to move a loaded mount from a parking area to a field pad, or if a motorized Wheeley Bar is where you are heading, since the 10″ wheels are one of the two prerequisites for the Motor Upgrade.

Key Features & Design

• Six 10″ pneumatic tires: Air-cushioned all-terrain tread that bridges ruts, gravel, and lawn rather than digging into them.
• Tow handle included: The assembly ships with a bracket cut for your bar’s leveling-screw size, so pulling the loaded bar replaces pushing it from behind.
• Dual-inboard rear pairs: Four rear wheels carry the load in two inboard pairs, keeping overall track width narrow for doorways and gates.
• Front swivel casters: The two front stations swivel, so the bar still steers on a tight pad.
• 3¼″ ride height increase: A modest lift for a 10″ wheel, thanks to the pneumatic tire profile.
• Prerequisite for the Motor Upgrade: The motorized drive works through these rear pneumatic wheels.
• Made in the USA by JMI, part of the CXB Astro family.

Mechanical Design

The reason a 10″ pneumatic tire works on soft ground is geometry and compliance together. A larger diameter meets an obstacle at a shallower angle, so a stone or a rut becomes something the wheel climbs rather than something it stops against, and an inflated tire flattens its contact patch under load, spreading weight over more area so the wheel floats on turf instead of cutting a trench. Six wheels rather than three divides the load further still. The rear axle carries four of them as two inboard pairs, which is what lets the kit add that carrying capacity without widening the bar past a doorway — the extra wheels go inward toward the centreline rather than outward. The two front stations stay swivel casters so steering behaviour is preserved. The tow handle mounts at the steering end and changes the direction the force is applied from: pulling a loaded dolly puts the operator ahead of the mass, where footing and sightlines are better on rough ground, instead of behind it.

Recommended Uses

• Moving a loaded imaging rig from a garage, across a lawn, to a backyard observing pad.
• Transporting a mount from a parking area to a field position at a dark-sky site over gravel or grass.
• Crossing a mulched or sanded path between a storage shed and an observing spot.
• Working on broken or heaved pavement where the stock 2⅜″ casters catch on every lip.
• Setting up the wheel half of a motorized Wheeley Bar conversion.

Compatibility and Accessory Notes

Because the tow handle bracket bolts to the leveling-screw hardware, this kit is leveling-screw specific and comes in two versions. The 5/8″ version fits current JMI HD Wheeley Bars — HD Medium, HD Large, and HD Shorty — with 5/8″ leveling screws. The 1/2″ version fits Standard Medium bars and older HD models with 1/2″ leveling screws. Measuring the outside diameter of one leveling screw with a caliper or rule settles which you have. Neither version fits the Triangle Style Wheeley Bar or the Sky Trekker series, which use different frames. The tow handle is part of the kit, so the standalone 1/2″ and 5/8″ tow handles sold for the 5″ caster setup are not needed here. The Tie-Down Bracket Kit works alongside these wheels and earns its place once the route crosses uneven ground. The Motor Upgrade calls for these wheels plus a Battery Pack Holder already fitted. Tell us your Wheeley Bar model and the diameter of your leveling screws and we will confirm which version to send.

Good to Know Before You Order

• The two versions are not interchangeable. The tow handle bracket is cut for either 1/2″ or 5/8″ leveling screws, and the wrong one will not align.
• The $364 list price assumes factory installation before the bar ships. Fitting the kit to a bar already in the field is priced differently, because the small casters are not coming back as a trade-in.
• JMI does not take back removed small wheels. They are traded in against the upgrade price only when the work happens at the factory.
• The kit raises the scope about 3¼″. Many observers welcome the extra eyepiece height, and it is worth allowing for if your reach at the eyepiece is already near its limit or you are measuring tip-to-tip for a new bar.
• Pneumatic tires hold air. They take the same occasional pressure check any air-filled tire does.
• Triangle Style and Sky Trekker bars are outside this kit’s fitment.

Frequently Asked Questions

Is it difficult to install?

It is a bigger job than a caster swap but still hand tools only: six wheel stations plus the tow handle bracket, with all hardware supplied. Ordering the kit with a new Wheeley Bar has it fitted at the factory. On an existing bar the work is done by the owner, and units built with bolt-on wheels take it directly — very old riveted-wheel units do not.

How do I tell whether I have 5/8″ or 1/2″ leveling screws?

Measure the outside diameter of one leveling screw with a caliper or a rule. Current HD Medium, HD Large, and HD Shorty bars use 5/8″; Standard Medium and older HD bars use 1/2″. Send us a photo if the reading is ambiguous.

Does the tow handle replace the leveling screws?

No. The handle mounts at the steering end using the leveling-screw hardware as its anchor, and the leveling screws stay in service.

Do I need to buy a tow handle separately?

No. The tow handle assembly and its bracket are part of this kit. The standalone tow handles are for bars running the 5″ polyurethane casters.

Will six 10″ wheels still fit through a doorway?

The four rear wheels sit as two inboard pairs rather than spreading outward, which is what keeps the overall track width close to the original bar.

Can the Tie-Down Bracket Kit be used with these wheels?

Yes, and it is worth having. Rolling a loaded mount over uneven terrain is exactly the case the tie-down kit was designed for.

Bottom Line

In short: six 10″ pneumatic all-terrain wheels and a matched tow handle that turn a hard-surface Wheeley Bar into one that crosses grass, gravel, and sand, with a 3¼″ ride-height increase and a narrow dual-inboard rear track that still clears a doorway.