Suspension Frame Maintenance

From Farkin Wiki

[edit] Checking for play

You can check for play in the suspension by lifting the rear wheel off the ground using the seat and lowering it to the ground again. If you feel any clunk when the wheel contacts the ground or if you can lift the seat slightly before the rear wheel leaves the ground these is some play in the suspension. Alternately you can try to wiggle the rear wheel side to side independently of the frame (but make sure play is not due to loose hub bearings).

There are several possible causes

• Play in shock mounting bushes
• Play in pivot bearings/bushes
• Loose bolts in shock mounts or pivots

It also pays to inspect the frame for cracks which could cause play in the suspension and creaking noises

The location can be pinpointed by touching the bike each side of a pivot point (eg one finger on the main frame one on the swing arm, or on finger on the shock one on the reducer) then lifting/dropping the rear wheel using the seat, you should be able to feel the play in the offending pivot.

[edit] Bearings

Most new suspension frames run sealed cartridge bearings at the pivot point(s). Depending on the frame manufacturer these bearings can range from something designed for use with high speeds and light loads (not MTB suspension) to something more suitable. The bearings seals are not designed to work against overzealous use of pressure washers or submersion try to avoid these when riding/washing your bike should either occur bearings can be repacked as described below.

Sealed bearings can be checked by removing whatever bolts etc hold the frame together then rotating the bearing (still in whatever part of the frame it is in if it is a press fit). If the bearing feels “notchy” or grinds or has sticky spots it’s time for a replacement. Note: the seal could be contacting the bearing cage causing the bearings to feel bad, if the seal looks damaged you can remove it as described below and feel the bearings again to see if it was the seal.

If the bearing is OK you can actually remove the seals with a fine pointed tool such as a dental pick or jewellers screwdriver, being careful not to permanently bend the metal plate built into the seal to provide stiffness. You can now see the grease in the bearing (there is usually not much from the factory). If you remove both seals the grease can be removed with a suitable solvent (carby clean, acetone etc) and if possible blown out with compressed air. The bearing can then be repacked with your favourite grease. The seals simply press back in, making sure that they fit properly into the bearing otherwise they can fall out.

If bearings require replacing inspect the bearing before removal to look for any numbers either stamped into the metal parts of moulded into the rubber seal, write these down and quote them to your bearing supplier when ordering replacements (or better still take in a sample). If there are no numbers etc then measure the OD (outside diameter) ID (the diameter of the hole in the middle of the bearing) and the width of the bearing once removed from the frame most bearing suppliers should be able to get what you need from these dimensions. Press fit bearings can be removed with a hammer but a more controlled method involves an engineers vice. Find a suitable item (sockets come in a wide variety of sizes and are pretty useful for this) that will support the area of the frame that the bearing is in yet has a hole in it just big enough for the bearing to fit through. Support the frame with this, then place another suitable item of a size just big enough Not to fit through the bearings hole (another socket, bolt etc) on the bearing so it does not touch the frame and wind the vice shut, depending on if the bearings were installed with loctite or not it can require some force to remove them. So long as the frame is supported only around the bearing there is little chance of bending or doing any other damage provided the supporting item is the right size.

Bearing installation is the reverse of removal, support the frame with soft jaws or a block of wood, find a suitable item that fits into the recess the bearing is to be pressed into and which also will only press on the outer race of the bearing (you don’t want to press on the inner race as this could damage the bearing and pressing the seal can damage that), wind the vice in.

Inspect to ensure that the bearing is seated into the frame and reassemble.

[edit] Shock bushes

There are several styles of these as well as several sizes. The shock reducers are normally a tight fit into the shock eyelets if the are an easy fit or can be wiggled about then the reducer of bush is worn. If the shock bush is at fault a special tool such as this one is required to remove and replace it.

Note: with 6mm diameter shock mount bolts (referred to as M6) it is possible to bend the bolts due to hard landings, fully threaded bolts (as opposed to long shank bolts which have a 6mm shank with thread only where the bolt actually protrudes from the frame) etc. check the shock bolts are straight when you have them out. There are several ways to fix the problem. You can fit a larger bolt, which will require modification of the frame thus voiding warranty. Make sure there will still be plenty of material around the bolt hole. If the bolt was threaded for the full length try to get a shanked bolt in as high a grade as possible grade 12 should be OK. Alternately the shock reducers (which are on either side of the shock and are what allows the bolt to bend in the first place can be replaced with a full length like this or this

1/2" (12.7mm) shock bushes are used on: Fox, 5th, 03 and 04 Rockshox (apparantly) and Avalanch

12mm bushes are used in: Manitou, 05 Rockshox and DNM

03 and earlier rochshox used 10mm

A bit rough around the edges but hopefully helpful If anyone has a good bearing search engine or know where to get shock bushes post it up