These are images of my rear shock. Can anyone tell me what shock it is (don't believe it is stock) and provide some guidance as to adjustment for my weight and riding conditions?
What rear shock is this?
- Thread starter antrey
- Start date
ST1100Y
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Its definitely an aftermarket with air assisted damper, but I cannot figure out the MFG (its not a Fournales though), so I can only guestimate on the functions: that Schrader valve at the top seems to allows one to increase/lower pressure in the damper section by using a standard tire filler/gauge, probably functioning as a 'preload adjuster' and/or simple change between stiff<>soft (just as on air assisted forks), saving one from having to fumble with a hook key to change 'preaload' of the spring (the 'comfy' version would feature an onboard compressor and dash indication to adjust by pushing some buttons). The 'hex dial' on bottom seems to control the orifices of the oil filled part in the damper cartridge, probably altering the 'response time' (fast<>slow AKA 'sport<>comfort'). AFAIK do both settings need to be changed together, so when you top up the air pressure for more payload, you'd also need to set the adjuster dial to the 'close' side so the damper can cope with the added mass.
I'm old and out of touch with shock technology, but years ago that valve was used to put high pressure Nitrogen into the system to keep the oil from foaming. I can't say for sure that's what its for, but that was one function back in the day. The pressure was in the range of 150-200PSI as I recall, so you don't want to mess with the valve and let it escape. My memory is weak, but I'm pretty sure one of my riding buddies in the '80s found that out the hard way.
kiltman
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- Apr 27, 2013
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- 68
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- Stratford, Ontario Canada
- Bike
- 2002,ST1100ABS
- STOC #
- 8826
I believe it is very similar to a progressive 420 shock. I just installed mine last night. The hex key fitting is to adjust the damping. Only turn it clockwise. I've set mine at 3. I bought mine used, and it came with some documentation.
As for set-up, you will just have to do trial and error
As for set-up, you will just have to do trial and error
This. Nice to have a Schrader valve like that to recharge the shock with Nitrogen from time to time (2 years or so). My zrx had silly little rubber ball type valves that had to have the specific sized needle to insert, lot of shops didn't have them. Schrader valve makes it much simpler. Hardest part may be to figure out what the pressure is supposed to be. ZRX with dual shocks ran at 160 - 175psi, again which no dealerships knew anything about (although they would just charge it to what I wanted). Had to dig around on the net to find any hint of that. The ST with one shock and much more weight may run at a different setting.
Makes a noticeable difference in the shock action when it's set to the correct pressure.
ST1100Y
Site Supporter
Affirmative, my Wilber shock (with piggyback expansion vessel) runs with nitrogen charge; its however not 'accessible by user' through a simple Schrader valve (actually is the charging port not even visual)... But while searching for enforced rear car suspension (for an estate), I came along a number of accessory shocks featuring such tire valve stems where the user tops off the pressure according to pay-/trailer-load. Also the forks on on super-sports and dirt bikes often feature adjustable air assistance, where the rider can simply adjust the pressure in air-chamber... all of this brought me to above assumption(!).
However, once a list member can ID the MFG of that thing, locating the documentation will be easy and assuring proper useage.
Last edited:
OP
OP
Thanks all for your feedback. I think I've traced it down to a progressive 465 series or previous, similar shock. The progressive page does not list a 420 series and shows the 465 as the compatible one with the ST1100. The 465 seems to be a recent model though and I suspect the one on my bike may be prior to the 465 being available. This is the link to the instructions, which do not mention the pressure at the Schrader valve and only mentions the damping settings, so I'm still at a loss as to what the air pressure should be: http://www.progressivesuspension.com/pdfs/3082%20465%20Series%20Install%20Instr.pdf
The pressure at the schrader valve is not spec'd because its not a user adjustable setting. Its a high pressure Nitrogen bladder that is filled at the factory to something in the neighborhood of 150psi. Its not a ride tuning adjustment, and that's why there's no reference to "air pressure" in the instructions, its not an air valve. Leave it alone and forget about it. I suspect the main reason they went away from the schrader valve setup for the bladder is too many people thought it was some adjustment port and tried to adjust it, then let all the Nitrogen out and had to pay to have it refilled and complained.
OP
OP
Don't quite agree with the "leave it alone and forget about it" sentiment. You should at least get a call in to Progressive, see if it was theirs and ask what pressure they filled them to. Almost any shop will have the equipment to refill it properly, and you don't want to leave it empty because it simply will perform poorly. Ballpark, you could just go with 150 and be done with it.
Agreed. You took my statement literally, which was a reasonable interpretation. In the context what I really meant is don't mess with trying to adjust it with air, that's not what it's for. Thanks for keeping me honest, I agree he should have it checked to make sure its at the specified Nitrogen pressure, it may have slowly leaked over the years.
For sure, that is a Progressive Suspension 420 series / first generation shock. Had one on my '93 years ago. If it has any more than 40K miles on it, send it in for a rebuild over the winter. They can also change the spring rate if needed.
OP
OP
The previous owner put only about 1,000 miles per year on the bike for a total of 5,900 miles over 6 years. He installed the shock at some point during that time. It feels pretty good to me, but I will confirm with him if it was over two year ago and maybe check the pressure.
The Progressive shock is good for 40-50K miles before needing rebuild. If it's only got 6,000 on it, you have quite a ways to go. No need to check the pressure. The shock is very reliable and will go the distance.