How to replace your rear shock

Published: 29 November 2006

 Why would I want to replace my rear shock?

Either because your current shock is leaking/worn out through age, or can’t cope with your weight/riding style with the available adjustment. Or simply because you want something more race-oriented – or something more compliant.

Are aftermarket shocks that much better?

Yes. They are usually designed for racing and come with a greater and finer range of damping adjustment, and are easier to service. They can also be bought with ride-height adjustment so the steering characteristics of a bike can be changed. The greater the range of adjustment (and higher build quality) the higher the price tends to be.

Are there any cheaper options available?

There are businesses advertising in MCN BikeMart, offering standard shock rebuilds, but many shocks can’t be rebuilt because they are sealed units, or new parts can’t be sourced. If you were happy with the standard shock’s performance when new, then there’s always the option of replacing like-for-like from your dealer, but that can be as expensive as an aftermarket unit.

Can I really change the rear shock myself?

Changing a single rear shock is well within the scope of anyone who can remove the bike’s wheels – though some late-80s and early-90s models have ridiculously complicated linkages and will take longer. Allow at least 3-4 hours. On older and high-mileage bikes there’s a good chance some of the mounting bolts will be corroded and seized. And while the rear suspension is apart inspect all the bushes/bearings for wear and tear. A decent toolkit (10-19mm sockets and spanners minimum) and a torque wrench should be all you need, along with some grease to lubricate moving parts.

1. As soon as you’ve taken the shock out of the wrapping, have a good look at the bike to plan your route. On some models various parts of the bike (panels, battery case etc) will need to be removed to get at the shock and remove it. But in most cases simple removing the rear wheel to get at the linkages will suffice.

2. Support your bike with the rear wheel a little off the ground. A paddock stand can’t be used because the swingarm will be free to move with the shock removed and the bike will fall over. Support it from beneath, or raise the back using a strap tied to the garage roof. Whichever method you choose, the bike’s weight must be canted forwards.

3. Remove the wheel spindle and rear wheel. Although with some bikes it is possible to get the shock out through the frame rails above it with the wheel in place, removing the wheel takes load off the connecting linkages. It also makes it easier to get sockets or spanners on bolts and nuts and to see what you’re doing.

4. Undo the most easily accessed of the two bolts (top or bottom) holding the shock in place – once removed, the linkages/shock can move to make easier access to the remaining bolt. If both bolt heads are easily reached, remove their retaining nuts, but leave the bolts in place until you are ready to pull both out.

5. Jiggle the swingarm as you pull the bolts free. Get a friend to push them through from the opposite side with a thin shaft (eg screwdriver). Corroded bolts may need forcing with a hammer and drift and liberal soaking of WD40. If seized then localised heat from a gas-torch is necessary. Ask a dealer to do this.

6. Carefully remove the shock, noting which way round it sits and watch for any bushes or spacers that may drop out to run away under the tool chest. Watch your knuckles and that you don’t end up knocking paint off the spring or scratching the shock’s body/frame. It may take several goes, trying different angles until you can wiggle it free.

7. Before fitting the new shock, check it against the original to make sure it’s the same length with the same end fittings. If the new shock requires that you use old bolts or bushes, give them a check for corrosion and clean them up with wet and dry (fine) grit paper. If they’re excessively worn or pitted, replace them with new items.

8. Before reassembly, grease all the bushes, bolts and put a light smear of grease over all the linkage arms and any other exposed aluminium surfaces to prevent corrosion. Check around the linkages for grease nipples and give them a squirt with a grease gun (someone’s granddad/dad will have one) while you have easy access.

9. Before fitting the new shock, by using info from the supplier, set the damping adjusters and spring pre-load to a recommended base setting – it saves skinning knuckles if you hold the shock tightly in a vice. Shocks with only pre-load adjustment should be set to match the rider’s weight. Try it at the halfway point for starters.

10. Offer up the new shock, wiggling it in the same way you got the old one out, while being careful not to scratch it. Push the top end of the shock into its mounting point and loosely refit its mounting bolt. By raising the swingarm and moving the shock to and fro, you should be able to line it up and fit the remaining bolts.

11. Fit the securing nuts on to the bolts and finger tighten (on the nut side). Tighten them to the correct torque figure (from a service manual or friendly dealer) using a torque wrench. A dab of thread locking compound (Loctite) on each of the bolt’s threads is recommended. A friend may need to hold a spanner on the bolt head to stop it turning.

12. Bikes with twin rear shocks are easier to deal with. Simply swap the old shocks for the new units one at a time. Again check the new shocks match the old ones – as some cheap replacement shocks are universal but the springs may foul the bodywork/tyres. Don’t forget to refit the bushes or spacers in the order they were removed.