Vacuum bleeding a shock

WARNING: ALWAYS WEAR EYE PROTECTION. I’ve had suspension fluid sprayed in my eyes and it sucks. It can happen even if you do everything right.

Degas the Suspension Fluid 

Suspension fluid has a lot of dissolved air in it, and before bleeding this air must be removed for two reasons:

• Dissolved air makes the oil more compressible.
• It allows the oil to absorb any small air bubbles left after bleeding.

Fill the vacuum bleeder reservoir no more than halfway with suspension fluid. Close the compressed air valve, open the vacuum valve, start the vacuum pump and run it to -30 in of Hg, then close the vacuum valve and turn off the vacuum pump. The the fluid sit in vacuum for 15-30 minutes. The vacuum can then be relieved by slowly opening the compressed air valve.

Bleed the Damper

NOTE: These bleed instructions are for bleeding a reservoir shock with a bleed port and an IFP. Although the basics of the bleed procedure are the same, the details for other damper architectures are different, so be sure to familiarize yourself with those before bleeding. 

Preparation

• Service/rebuild the damper and assemble it without suspension fluid.
• Connect the appropriate bleed adapter to the bleed port on the shock, and position it so it’s the highest point of the damper.
• Install the IFP and the reservoir cap retaining clip. It is very important the IFP be retained inside the shock during the bleed process.
• Fill the vacuum bleeder reservoir no more than halfway with the desired suspension fluid.
• Set your compressed air regulator to 45 PSI.
• Connect the compressed air source to the vacuum bleeder.

Bleed

1. Close the compressed air valve, start the vacuum pump, and slowly open the vacuum valve. Once there’s a good vacuum, close the vacuum valve and turn off the vacuum. Be sure to close the vacuum valve before turning off the pump.

NOTE: What look like bubbles under vacuum are actually pockets of vacuum and will collapse during the pressure phase of the bleed.

2. Verify the vacuum valve is closed, and slowly open the compressed air valve. Oil should start flowing from the reservoir into the damper. Once the pressure is stable, cycle the damper several times by hand. It can also help to tap the damper to dislodge any bubbles.

4. Repeat steps 1-2 several more times (I usually do 5 cycles) to help insure all the air is evacuated from the shock. Any small bubbles which remain will be absorbed by the degassed suspension fluid.

5. Close the compressed air valve, and use the pressure relief valve to release the pressure.

6.  Disconnect the air compressor, open the compressed air valve, and set the IFP depth. The excess oil will be pushed back to the vacuum bleeder reservoir.

7. Disconnect the vacuum bleeder from the bleed adapter, then remove the bleed adapter and close the shock's bleed port.

8. Install the reservoir cap and pressurize the reservoir to spec.

Building a vacuum bleeder

A suspension vacuum bleeder uses alternating vacuum and pressure to bleed a damper. It's much easier than hand bleeding, does a better job, and is a less mess.

Bill of Material

A bleed adapter specific to the damper will be required to connect the vacuum bleeder to the damper. ANSO (https://anso-suspension.com) makes good bleed adapters at a reasonable price, and the list below reflects using ANSO adapters. If different bleed adapters are used, the "3/8" FNPT V-Style coupler" would need to changed to work with those adapters.

• 1/4" NPT 50 PSI pressure relief valve - $9 -  https://a.co/d/7lOzOpp
• 3/8" OD 1/4" ID polyurethane (PU) tubing - $9 - https://a.co/d/7cUTqff
• 1/2" NPT to 1/4" barb 90* fittings - $10 - https://a.co/d/fgpZFRI
• 3/8" spring hose clamp - $6 - https://a.co/d/gdm5f48
• 3/8" FNPT V-Style coupler - $9 - https://a.co/d/8DQBxJ5
• 1/4" NPT pressure gauge - $13 - https://a.co/d/f1TbRqJ
• 1/4HP 3.5 CFM vacuum pump - $55 - https://a.co/d/2L3zF0F
• Hydronix HF2-10CLWH12 filter housing - $23 - https://a.co/d/dYMTLSv
• 3/8" NPT 3/8" tubing push to connect fittings - $9 - https://a.co/d/auJHnwp
• 1/2" NPT mini ball valves - $13 - https://a.co/d/72oPZEk
• 1/4" FNPT air hose quick connect adapter - $4 - https://a.co/d/aGIQmXG
• 1/4'' NPT 1/4" barb fittings - $5 - https://a.co/d/cOngmrj

TOTAL - $165

Assembly

NOTE: Whenever installing a fitting the threads should be wrapped with at least three layers of Teflon tape. Be sure to orient the wrap so that tightening it doesn’t try to un-wrap it. 

Vacuum Pump

• Fill the vacuum pump’s sump with suspension fluid, roughly the same viscosity as you’ll be using.
• Remove the inlet fitting and replace it with a 1/4” NPT barbed fitting.

V-Style Coupling

• Install a 3/8” NPT push-to-connect fitting.

Quick Connect Coupling

• Install a 1/4” NPT barbed fitting.

1/2” Ball Valves

• Install the 1/2” NPT barb 90* fittings so they point away from the valve handle.

3/8” Push-to-Connect Fitting

• In one of the fitting, drill out the bottom of the fitting so a tube can extend all the way through the fitting.
• Meticulously clean any metal swarf out of the fitting.

Filter Housing

• Drill a 19/32” hole in the top of the lid and and thread in the drilled out 3/8” push-to-connect fitting. Teflon tape is not needed on the thread. The fitting will tap itself into the plastic of the lid. Keep threading it in until the bottom is just proud of the inside of the lid.
• Drill a 15/32” hole in the top of the lid, then thread in the pressure gauge. Teflon tape is not needed on the thread. The gauge will tap itself into the plastic of the lid. Keep threading it in until the bottom is just proud of the inside of the lid.
• Drill a 15/32” hole in the side of the lid and thread in the 1/4” NPT pressure relief valve.  Teflon tape is not needed on the thread. The valve will tap itself into the plastic of the lid. Keep threading it in until the bottom is just proud of the inside of the lid.
• Clean out any plastic shavings from the lid.
• Install the two two ball valves into the two threaded holes in the lid. The valve handle should face upward, and the barb fitting should face downward.

Putting it all Together

• Insert the polyurethane (PU) tubing through the push-to-connect fitting in the lid and feed it down until it sits about 1/4"-1/2” above the bottom of the reservoir. Install a zip-tie or clip to prevent the push-to-connect release collet from being depressed.
• Cut the PU tube to length. It needs to be long enough to go from the vacuum bleeder to the damper with some slack in the tube. However, the tube should be kept as short as practical to aid in bleeding.
• Connect the V-style coupling to the end of the PU tube. Install a zip-tie or clip to prevent the push-to-connect release collet from being depressed.
• Cut a length of PU tube to connect the reservoir to the vacuum pump. Put two spring clamps on the tube, warm up the two ends with a hair dryer or heat gun, connect them to the barb on the vacuum pump the barb on one of the ball valves on the reservoir; this is now the vacuum valve. Put the spring clamps in place.
• Cut a length of PU tube to connect the reservoir to the air compressor. Put two spring clamps on the tube, warm up the two ends with a hair dryer or heat gun, connect them to the barb on the quick connect coupling and the barb on the other ball valve; this is now the compressed air valve. Put the spring clamps in place.

Testing

• Test the reservoir to make sure it holds vacuum. Close the compressed air valve, open the vacuum valve, and run the vacuum pump until the pressure gauge registers 30 in. of Hg vacuum, then close the vacuum valve and turn off the pump (air can bleed through the vacuum pump when it’s not running so close the vacuum valve before turning off the pump). The reservoir should easily hold the vacuum for several minutes, if not hours. If it doesn’t, there’s a leak which needs to be found.
• Test the reservoir to make sure it holds pressure. Pressurize the reservoir to 45-50 PSI and close the compressed air valve. Set the air compressor’s regulator to 45-50 PSI, DO NOT pressurize the reservoir with higher pressure air and try to stop it at 45-50 PSI using the pressure gauge. Again observe the pressure gauge for any changes in pressure. If the pressure drops over the next several minutes, there’s a leak which needs to be found.

If the system passed both the vacuum and pressure tests, install it in its final position or install it in its stand/frame.

Andreani Thread

Many vacuum bleed adapters use "Andreani thread" named after the Andreani vacuum bleed machine. It's actually an 1/8" BSPP (British Standard Pipe Parallel) thread. 

Adapters from BSPP to NPT are available:

https://www.amazon.com/dp/B0CLHK1CP2

https://www.amazon.com/dp/B01LQU8FV8

NOTE: There is a British Standard Pipe Parallel (BSPP) and also a British Standard Pipe Taper (BSPT). Make sure you purchase the Parallel.

Rock Shox Deluxe pull shock rebuild

Rock Shox Deluxe pull shock rebuild - 50mm travel

Bill of Material:

O-ring (Buna or Viton) 16mm OD x 10mm ID x 3mm width - https://a.co/d/hH2sRR9

O-ring (Buna or Viton) 25mm OD x 20mm ID x 2.5mm width - https://a.co/d/ampJWyj
TC oil seal 10mm ID x 20mm OD x 7mm height - https://a.co/d/5dajKVA
Slickoleum grease

Suspension Oil - Stock was 5wt, but can be increased for increased damping. Approximately 1 liter is required for bleeding.

Tools Required:

Adjustable wrench

15mm cone wrench

Vise with soft jaws

10mm shaft vise (potentially not required)

NOTE: I have no measure the rebound needle o-ring and therefore do not know its size.

Due to the lack of IFP or any pressurized components, the Rock Shox pull shock is very quick and easy to service. 

Working on shocks can be dangerous. Always wear eye protection when working on suspension.

Disassembly

Remove the spring and spring perch and clamp the eyelet assembly of the shock in a vise. 

The two ends of the shock are locked into the shaft by the top out bumper perch and the bottom out bumper perch. Unlock them by loosening the perches.

     

Unlocking the top out bumper perch.

Remove the rebound adjuster assembly from the shaft and the bottom out bumper and perch.

Using an adjustable wrench, loosen the two end caps of the shock. If you can't hold the shock bodily tightly enough with just your hand, lock the preload adjuster and trunnion together and use those for added grip. 

Remove the shock from the vise and remove the eyelet assembly, top out bumper and perch, preload adjuster, trunnion, and both end caps. If the eyelet assembly is too tight on the shaft to remove by hand, use a 10mm shaft vise.

Empty the old oil from the shock, remove the shaft and damper piston assembly, and thoroughly clean all parts.

Service

Using a pick, carefully remove the wiper and o-ring from the end caps, and using a flat screwdriver, carefully remove the oil seal from the end caps.

The wiper is a proprietary size, but didn't work very well anyway, so we're using an o-ring instead. Lubricate a 16x10 o-ring with Slickoleum and install it in the wiper gland of the end cap. Lubricate a TC oil seal with Slickoleum and install it in the oil seal gland of the end cap. Use soft jaws in your vise to fully seat it. Lubricate a 25x20 o-ring with Slickoleum and install it on the o-ring gland of the end cap.

Bleed

I bleed using the immersion method.

First, put the shock with the end caps on the shaft but not screw to the body in a gallon Ziploc freezer bag. Then pour in about a liter of suspension oil, and burp and seal the bag. Have someone hold a corner of the bag, or clamp it in a vise, to free both your hands.

Move the shock around to purge any air from it, then screw both end caps into the body. Keep the shock submerged in the oil at all times! Take extra care keep the hollow top half of the shaft submerged.

Get the two end caps as tight as you make them by hand; it'll be enough to keep oil from leaking out. The oil will soften the Ziploc bag, so don't take too long.

Immersion bleeding with a Risse Racing Shock.

Remove the shock from the bag with the hollow top shaft facing up so it doesn't lose any oil. Clamp the shock back into the vise.

Pour the remaining oil in the bag back into its bottle.

Clamped in vise after bleeding, with the end caps tightened. Excess oil is seen at the top of the shaft.

Finish tightening down the two end caps with an adjustable wrench. As you tighten them down excess oil will come out the top of the shaft. Be very careful moving the shock as it can cause oil to shoot out the shaft.

Reassembly

Lubricate the rebound needle o-ring with Slickoleum (replace if necessary/wanted), then turn the rebound knob all the way fast / all the way out. Install the bottom out bumper and perch on the shaft and thread it on all the way. Install the rebound assembly and thread it on until it stops. Then while holding the rebound assembly in place with an adjustable wrench, lock the bottom out bumper perch against it using the 15mm cone wrench.

You can now safely cycle the shock. It should cycle smoothly and should make any slurping noises.

Remove the eyelet assembly from the shaft. Install the top out bumper and perch and thread it on all the way. Install the eyelet assembly and thread it on until it stops. While holding the eyelet assembly with an adjustable wrench or in the vise, lock the top out bumper perch against it using the 15mm cone wrench.

Clean the shock with alcohol and a clean paper towel.

Reinstall the trunnion, preload adjuster, spring, and spring perch.

1998 Fox owner's manual

Download Fox manual as PDF

Schwinn suspension manual

Download Manual as PDF

Risse Racing shock service

Risse Racing shocks don't have a bleed port and rely on fast assembly to minimize air in the shock, so it's virtually impossible not to have some air mixed with the oil. The solution is assembling the shock immersed in suspension oil. It would be messy and expensive to fill a small bucket with oil, but there's a trick to making it easier.

First, clean the inside and outside of the shock very well. Then fill the body of the shock with oil, the fill a gallon Ziploc bag with about 1/2 to 3/4 quart of suspension oil, place both halves of the shock in the bag, and press all out the air and seal the bag. Have someone hold a corner of the bag, or clamp it in a vise, to free both your hands.

Now assemble two halves of the shock through the bag, making sure not to let any residual air in the bag into the shock. Make sure to "burp" both halves of the shock before assembly to get any residual air out. Get the two halves as tight as you make them by hand; it'll be enough to keep oil from leaking out. The oil will eventually soften the Ziploc bag, so don't take too long.

Once the shock is reassembled, open a corner of the bag, pour the unused oil back into the bottle, remove the shock, snug the gland nut, and clean it up well with alcohol.

The shock needs to be bled with the air chamber pressurized, however, then the design of the shock traps an air bubble under the IFP, which is released once the shock cycles. I found the easiest way to deal with it is bleeding the shock, releasing the pressure and cycling it with the shock upside down, pressurizing it, and loosening the gland nut, putting it back in the Ziploc filled with oil, separate the shock to release the air bubble, and finish bleeding it again.

NOTE: Many of the bottles of suspension oil I've used, even brand new bottles, have sediment on the bottom, so be aware when pouring it into the bag.

Risse Racing shock o-rings

Standard o-ring sizes to fit Risse Racing Genesis, Astro-5, and Terminator shocks with 1.5" shafts.

Shaft top out - #25
Cap - #27
Damper piston - #29
IFP (x2) - #123
Nut threads - #129
Main seal - #222
Wiper - H-1500 (https://www.amazon.com/dp/B005M2RC3Y)

Rock Shox SID rear shock o-ring sizes

Rock Shox produced rebuild kits for the SID rear shock. It had the main seal, body o-ring, shaft bushing, shaft seal, shaft wiper, and glide ring. They're impossible to find anymore, but aside from the shaft bushing, each of the parts are available individually.

Main seal: #221
Body seal: #31
Shaft wiper: AN-09 (https://www.amazon.com/dp/B01CYJQW1U)
Shaft seal: SKF ZBR125-1000-250-E6W (# UBR-125-01.000-250 www.mfpseals.com/c/621/skf-polyseal-ubr-rod-u-cup-urethane.html)

The glide ring can be made from a 1/16" or 0.07" thick piece of appropriate material (UHMW, PTFE, etc.). It's 2.28mm wide and approximately 124mm long.

Although the shaft bushing isn't available, it can be easily fabricate from appropriate material on a lathe.

Rock Shox SID shock rebuild kit.

Clockwise from top left: main seal, shaft wiper, shaft bushing, glide ring, body seal, and shaft wiper.

Rock Shox SID rear shock rebuild