how to replace your idler wheel bearings

It's the little things. The little rocks in your shoe or the itch on your back you can't reach. Little things can grow into big, bad and ugly things. Of course, little things, done right, produce better, bigger things.

Call them bogies or idler wheels; they're little wheels that do a fair amount of work. Are they worth a "little" attention? Absolutely.

What is an idler wheel's function? In the case of the slide-rail idlers, those that ride on top of the track help ease the friction between the track and hyfax, particularly at high pressure points along the rail. The rear-most idler wheels, or rear axle wheels provide a turning point for the track- and provide track tension and alignment. The upper idlers guide the track up over the rear skid frame mount and also provide a route for the track to meet the drivers. Combining these little functions brings a sum that equals a larger purpose: allowing the track to rotate somewhat effortlessly.

Generally a sled can go thousands of miles before its idler wheels start showing signs of wear. Of course, this is also dependent on the type of riding and conditions. Poor storage conditions can also shorten bearing and wheel life.

Our demonstration sled for changing out idler wheels was a 1988 Polaris 400 SKS. This well-maintained sled had nearly 5200 miles on its life; owned by Eric Woolstenhulme of Idaho Falls, Idaho. This sled introduced Wooly's young children to the snowmobiling beat while he and his wife enjoy the new crisp throttle pulls of today's iron.

Before we coach you through a full idler swap out or idler wheel bearing replacement, you should probably understand the consequences of when an idler wheel bearing fails.

If the bearing seizes, the wheel stops spinning and if this goes unnoticed, track damage can occur. If the bearing fails and comes apart, the wheel can be spun and bounced on the shaft and cause damage to skid frame components. If this happens on a rear axle wheel or upper idler, the track can become severely mis-aligned, the track clips can tear up the hyfax and suspension components can tear up the track. If a slide rail idler wheel fails, the track will ride on the hyfax only and cause excessive wear of the hyfax (a good reason to consider installing hyperfax hyfax on the skidframe). Furthermore, if a bearing is starting to seize, undue resistance caused by the bearing steals horsepower.

Checking and maintaining the idlers is a fairly simple task. The best way is to release the tension on the track and spin the wheel while listening and feeling for any growling. But, the simplest way is to move the wheel from side to side checking for slop in the bearing. Comparing this to a good wheel and bearing will soon teach you when a bearing is going south.

Also, note that most idlers can have just the bearing replaced instead of purchasing a wheel/bearing assembly.

To remove idler wheels, place the snowmobile on a sled lift, or place the rear end on a jack stand, or roll the sled over on its side. If you choose to roll the sled on its side, place a piece of carpet on the shop floor to protect the bumper rail, belly pan and hood, and make sure the oil, fuel and radiator caps are tight.

Then, most slide rail idlers can easily be unbolted, removed and replaced.

If replacing a rear axle idler wheel, loosen the rear axle bolts and the alignment bolts. (Placing a mark on the slide rail at the alignment bolt's head or measuring its position will speed aligning and tensioning the track during reassembly.) Remove the rear axle bolts and remove the idler wheel. If an inner wheel needs replacing the axle needs to be removed to replace the wheel.

If replacing an upper idler, release the track tension as above. Then remove rear skid mount bolts and swing the suspension out from the tunnel. The idler can then be slid from the shaft.

Reinstall idlers and skid frame components in reverse order of removal and tighten track to original settings and check alignment per your owners manual.

As a piece of advice, if an idler wheel starts to show its age or begins to seize while out in the hills or on the trail, swapping idler wheels around is a good get-you-home measure. The upper idler bearings are smaller than the axle idlers or slide rail idlers for some manufacturers; note this when swapping.

You can swap the outer axle idler for a center. If snow conditions are good for hyfax lubrication, it is no big deal to run without a few slide rail idler wheels.

Remember, big repairs are avoided with little maintenance measures such as giving the your sled's idler wheels and bearings an eyeball. Fulfilling those little things can pay big dividends.

Here is the simple how to.

1. Remove designated idler wheel from rear suspension skidframe.

2. With a snap ring puller, remove the bearing's snap ring.

3. If using a bearing puller, remove bearing.

4. If no bearing puller is available, place the idler wheel on top of an opened vise (opened wide enough to expose bearing and race).

5. Using a socket or round bar, drive the bearing out by the inner bearing race.

6. With the bearing removed, inspect C-clip groove for improper wear or damage.

7. Clean the idler wheel with a cleaning solvent.

8. Set the new bearing on of top the idler wheel and tap into place using a bearing driver, socket, or pipe the same size as the outer race. Driving the bearing on the inner will damage the bearing's roller surfaces.

9. Reinstall C-clip on bearing. Ensure C-clip is secured in its groove.

10. Return idler wheel to skidframe and secure.

By way of information, bearings are not proprietary and can be picked up at a bearing shop if a dealer isn't available.

Woolstenhulme is an engineer extraordinaire and a superb freelance mechanic who operates out of his garage with a crescent wrench and vise grips. He has helped AmSnow on several garage done "how to" repairs or installations just to show that even an eight-hour-a-day desk junkie can do this stuff. Many thanks.