How to upgrade your Downtube Mini suspension spring:

It's a very simple procedure: remove the spring, install the doorstop, ride. No special parts need to be manufactured. I have broken it down in a step-by-step procedure for clarity.

Materials needed:

1. Rubber doorstop. The one pictured is almost perfect in all respects - shape, size and damping properties. Note the dimensions and especially the recess at the one end.






2. 2x mudguard washers (this is what they were called at the hardware store, basically large washers. Hole: 10mm. Total thickness: 2-3mm

Procedure:

1. Enlarge the screw hole in the doorstop to 9mm: Pop the doorstop in a deep-freeze for a couple of hours to harden it, then simply drill the hole out with a 9mm drill bit. (A 6mm or 1/4" bit will probably work but you'll have some effort to push the suspension bolt through at assembly time.)

2. Place the bike upside down. (Optional): Unhook the rear brake noodle.

3. (Optional): Loosen the rear axle nuts and take the chain off the front cog to create slack. Pull the gear and brake cables a bit to the back to create some slack. Then pull the rear wheel to the extreme of the track end and hand-tighten the axle nuts to keep it there. This step creates some room to access the suspension bolt but may not be essential.

4. Remove the rubber end cap pictured. Unscrew the bolt in the recess. Leave it in place - no need to remove it.



5. Swivel the rear triangle to open the suspension gap and remove the rubber concertina sleeve, spring and the plastic washers under the spring ends.



6. Insert both plastic washers around the spring boss at the main frame side of the suspension joint. This fills in that recess a bit so that the spring boss height matches the doorstop recess depth.



7. Apply a small amount of grease on the recess end of the rubber doorstop. Push it over the frame side spring boss. It is a neat fit and some force is needed.

8. Slide the mudguard washers over the suspension bolt up against the spring boss on the rear trangle side. When pushed against the spring boss, the washers must be slightly recessed to ensure the doorstop is captured by the edge. Grease the bolt lightly.



9. Push the bolt through the doorstop hole and tighten it. Mine requires some fiddling, especially pushing the suspension gap closed to ensure the bolt threads engage. Put the rubber end cap back in.



10. (Optional): Put the rear wheel back in its place and settle the cables. Hook up the rear brake.

Go for a ride!