Rear wheel

The rear wheel is the rim, hub and spokes or cast arms at the back. On chain bikes the hub also carries the sprocket carrier and cush drive on one side and the brake on the other. On scooters the wheel bolts straight to the gear case.

What it does

The rear wheel carries most of the weight and passes the drive force to the road. It must run straight and in line with the front wheel. Chain adjusters set both chain slack and wheel alignment, so uneven adjustment pulls the wheel out of line. Bearings, spokes and rims wear and get damaged the same way as at the front.

Signs it is worn or failing

• Wobble: Wheel is buckled or wobbles.
• Rocks on the axle or rumbles: Wheel moves sideways on the axle, Rumbling from a wheel.
• Rim dent or crack: Rim is dented or cracked.
• Clunk from drive: Cush drive clunk.
• Loose spokes: Spokes are loose or broken.

When to replace it

Replace a cast wheel that is cracked or bent beyond the runout limit. Rebuild a spoked wheel with a new rim if bent badly.

What to match when buying

• Usually: Wheel bearings, Rear tyre, Cush drive rubbers, Spokes and nipples, Wheel axle and spacers.
• A complete wheel must match make, model, year, rim size, brake type, sprocket carrier type and tube or tubeless.
• Rim code, for example 3.00×15: width × diameter in inches.

Fitting notes

• Remove and refit the rear wheel. Note spacer positions.
• Check the axle nut torque for your exact bike; the K-Light 125 manual gives two different values, so confirm before work.
• After fitting, set chain slack and alignment: Check and adjust chain slack.
• Watch for spacers as the axle comes out. There may be one, two or none, and they centre the wheel in the swingarm.
• On a drum brake, undo the brake anchor bolt and the rod adjusting nut before the wheel comes out. The anchor stops the brake plate turning with the wheel.
• Some swingarms have open slots or a removable block at the rear, and some hold the wheel on one side only with lug nuts. If the bike has no centre stand, the wheel must be held off the ground another way, and a silencer or shock may have to come off.

Reference (K-Light 125)