Bicycles should be maintained regularly even they have the best quality.Inspecting chains
The chains of bicycles stretch over long time use. The pitch of the bicycle chain is 0.5 inches, so the measurement of 24 chains are 12 inches. The chain should be replaced if the length has exceeded 1/8 inch.Chain cleaning
As oil and mud build up in your chain, you have to clean it. You can use a chain washing machine to clean the chain, or put the disassembled chain in a vessel of clean oil and shake the excess dirt free. Dry the chain and then apply clean grease.Inspecting freewheel and crankset
If the chains derail from the freewheel after changing to a new chain, you need to change the freewheel. The chain would be stuck if the teeth on the crankset were worn out and the crankset should be change. The loosened fixed screws should also be retightened.Inspecting rims
Inspect the bicycle's rim around valve and spoke holes to look whether there are small rifts or not, then change the rims as quickly as possible if there are rifts. Lift and rotate the wheel, then adjust rim if there is friction between rim and brake pads after observation.Inspecting spokes
Change the broken spokes of front and back wheels after inspection. The rims must be readjusted after changing the spokes. The direction of rim's runout must be observed when adjusting the rims. If the rims swing rightwards, loosen the right spokes and tighten the left. If the rims swing leftwards, the operation is contrary. The runout amplitude of the rims should be less than 2 mm.Inspecting handlebars
Inspect for any deformation on the handlebars and replace them if there are rifts on the combining parts.Inspecting saddles and seat post
Remove the seat post and inspect for deformation and rifts. Put a thin oil on the post and set it back if it is normal. Inspect the saddle and bottom bracket, replace them if there are any damage or other problems.