HarleyMotorcyclePartsStreet Bob (FXDB) Shock Swap: Find Out What Is Fitted First
Plenty of used Dyna Street Bobs are already lowered. Measure before you order, or you buy the wrong length.
Do not order from the catalogue description of your bike. Order from the bike itself. This dark solo-seat bobber attracts lowering early in its life, so a used FXDB frequently arrives on someone else's choice of shock, and buyers who assume stock end up surprised when the new pair lifts the tail or sits lower than the old set ever did. The tape measure is the first tool out on this job.
Tools
- Tape measure and notebook
- Phone for photos
- SAE socket set
- Torque wrench
- Motorcycle lift or stand
- Service manual
An inventory before any spanner
Read the shock bodies. A maker's name, a label or a colour that does not match the rest of the dark factory finish is a good clue, though not proof, that the originals have gone. A receipt from the seller is better still.
Then measure. With the bike on the kickstand, note the distance between the centre of the upper fastener and the centre of the lower on each side. Note the height of a fixed point on the rear fender as well, so you have a true before-and-after number.
Compare your eye-to-eye reading with the standard length listed for your year in the service manual. A clear gap means you are looking at a lowered bike, and now you get to decide something the last owner decided for you.
Write the result on the same page as your fender height. Weeks from now, when you wonder whether the new pair really changed anything, that page will settle it.
Check the left and right readings against each other too. A mismatch suggests a mixed pair or a bent mount, and either is worth knowing now.
Choosing a length on purpose
Going back to standard height gives you the travel and clearance the bike was designed around. Staying low keeps the look and the easy reach to the ground, at the price of bottoming sooner and a shallower lean before hard parts touch.
Think about the solo seat as well. If you truly ride alone, say so when comparing load ratings. A shock chosen for a passenger you never carry can feel harsh on your own.
Remember the kickstand. Dyna shock length directly alters how far the machine leans when parked, and a change in either direction can leave it too upright to trust or leaning further than you like.
Propping up the frame
Use a lift or a stand that bears on the frame. Bring the rear up until the tyre is just unloaded, and stop. If the tail hangs too far, the swingarm drops and pulls on the mounts, which makes every fastener harder to shift and refit.
Tie the bike down. The rubber-mounted engine can give it a slight sway when you lean on a wrench, and that movement should never reach the stand.
Out with the old one
Pick whichever side is less obstructed. Photograph it close up, with the hardware in shot. Previous owners sometimes add spacers or odd washers, so your photo records what was on the bike, even if it turns out to be wrong.
Undo the upper stud fastener, then the lower. Draw the shock off and leave its opposite number in place, which holds the swingarm in position. Never have both off together.
Keep any non-standard hardware in a labelled bag. Do not assume that it should go back on. Look up what the manual shows for that stack, and if the previous owner's parts differ, sort out why.
Reading the studs and bushings
A lowering shock can run hard against its stops for years, and that abuse shows up at the mounts. Check the mounting stud for wear ridges and thread damage, and feel whether it shifts at all in the frame.
Inspect the swingarm side the same way. Press a fingernail into the bushing rubber. If it is splitting, flaking or has gone hard and shiny, plan on replacing it instead of reusing it in a new shock.
In with the new pair
Offer the new unit up and support the tyre on a block, moving it up or down until the eyes meet the mounts without force. Never hammer an eye on, and do not pry on the finish.
Fasten by hand first, then torque to the figure printed in the service manual for your exact year. Move to the other side and do the same. Set any preload adjusters to match each other.
Measuring the result
Roll it off the stand and repeat your fender and eye-to-eye measurements. They should now say what you meant them to say. Check the kickstand lean on flat ground, and again on a slight slope, before walking away.
Take a gentle first ride, listen for tapping from the rear and look underneath afterwards for anything rubbing. Confirm the fasteners are still at spec once you get back.
Mistakes that cost money
- Assuming a used FXDB is at stock height.
- Refitting a previous owner's spacers without checking what they do.
- Confusing this bike with the 2018-up Softail Street Bob.
- Choosing a load rating for a passenger who never rides on a solo seat.
- Forgetting that length also changes kickstand lean.
When to stop
If you find mismatched hardware you cannot explain, or an eye that only lines up under force, do not bolt it up and hope. Find out what the correct stack is first, from the manual or a Harley technician.
Parts for this job
Check fitment for your own model and year before ordering — add your bike and we will flag what fits.
Other Harley how-to guides
This guide covers procedure and judgement. Torque figures, fluid capacities, gaps and tension settings are specific to your model and year and must come from the factory service manual for your motorcycle — we deliberately do not print numbers we cannot stand behind for your bike. Independent aftermarket retailer, not affiliated with Harley-Davidson, Inc.