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It turns out, if you forget to remove the pressure from a fork when doing an air shaft change, what you essentially have is a spear gun... eek....
I wanted to drop the travel on some (unused) Revelations I got in the CRC fire sale..
Simple enoughh job... Drop off the lowers (with abrely any oil in..sigh)... remove the air shaft c-clip..insert new air shaft..bish bash bosh..
However, I was struggling to remove the c-clip -it seemed to be under some sort of "pressure".
Oh well... I'll pull and twist a bit harder..
Follower by an almighty BANG as the old air shaft jettisoned across the garage, and I literally got shotgunned in the glasses/face/hair with a barrel full of fork grease!
Had there been children/robbins in the garage, they for sure would have been killed to bits!
I stood there for 20 secods checking i hadn't been speared in teh thorax..counting my blessings!
That's a lesson I won't forget in a hurry!
DrP
IIRC, the early Rockshox forks from the 90s used to fire the damping rod out the top of the fork if you bottomed them out too hard.
You just completed the cyclist version of Spring Compressor Roulette
I have made a similar mistake despite doing lots of lowers servicing.
Took me a while to find the airshaft in the garage.
The more times I make mistakes like that the more I come around to the idea that safety glasses, gloves, etc are a good idea
Did similar on my Mezzers. Didn't use a pump to depressurise which meant the negative spring was still charged. Got a bit of a suprise as I dissembled the air spring!
IIRC, the early Rockshox forks from the 90s used to fire the damping rod out the top of the fork if you bottomed them out too hard.
Actually reminded me of a time at uni my housemate got 'shot' in the face by the top cap of some cheapo air forks on an old GT... he hit a drainage type channel riding through southampton common... bottomed out the fork and a big bang later, he was nursing a nice red mark on his face!!!
DrP
did that with an old manitou shock that had somehow got air pressure where it shouldn't have had air. I swear I felt it skim past my face and leave a fairly significant dent in the roof of the shed.
What with this and the spring compressor stuff... Did the spring compressor/ slammed car thing work in the end?
Not quite the same, but I was staring interestedly at the inside of a caliper as my mate blew compressed air through the brake line. The idea was it'd probably ease the stuck piston out. What actually happened was one second later both pistons crossed my eye line about an inch away before accelerating towards the western horizon 🙂
See also cutting spokes out of a fully tensioned wheel with no rim tape
See also effect of partially depressurised rear shock when changing tokens for the fifth time that evening. I am lucky to have my fingertips still in OEM spec as leftover air in negative chamber collapsed the shock when opening the air can. I don’t know where my fingers were caught but I had interesting marks on my fingers for a month or two.
DrP
Full Member
IIRC, the early Rockshox forks from the 90s used to fire the damping rod out the top of the fork if you bottomed them out too hard.
Actually reminded me of a time at uni my housemate got ‘shot’ in the face by the top cap of some cheapo air forks on an old GT… he hit a drainage type channel riding through southampton common… bottomed out the fork and a big bang later, he was nursing a nice red mark on his face!!!DrP
RST as well, a guy I used to ride with got a fractured jaw from it!
Not quite the same, but I was staring interestedly at the inside of a caliper as my mate blew compressed air through the brake line.
I had a mate back in the day who did that with a brake caliper off a car. Only problem was he held it in one hand with his fingers between the two pistons.
As a kid I fired an air rifle at old wooden door. It turned out to be harder than I expected and the pellet bounced straight back at me hitting me on the cheek half an inch below my eye...
What with this and the spring compressor stuff… Did the spring compressor/ slammed car thing work in the end?
Yeah - funnily, the car spring compressor (clamp type on, similar to the pic posted above) waas absolutely fine - felt supre solid and safe. I used hand tools (as advised) and just gently compressed each side bit by bit. didn't feel like it would slip or explode.
I reckon using an impact wrench (like ont eh pic above!) would be much sketchier - vibration and gross imbalance of the L/R compressor would be much scarier!
The hardest part of lowering the polestar was the fact that the front shocks needed to be compressed IN SITU in order to remove them from the lower a-arm..
I didn't have the official tool, so had to improvise by jacking the shock up, whilst lowering the a-arm..
Above: THIS was the dangerous bit!!
This was fine..
DrP
Those spring compressors put the fear of God in me. I've seen this go wrong several times as one compressor slides round in a finger trapping blink of an eye to meet the other one.
Good job DrP! Glad to hear nothing went wrong.
Interesting. In line with my 'try to saw a Hilti nail gun cartridge in half with a hacksaw' trick.
+1 on another pal who took an RST top cap to the face midway down a trail...
IIRC some of the Rockshox and RST top caps were made of plastic, cheap plastic too, and they would just strip the thread and fire out under a suitable sudden, heavy load....
I take it that your a DrP as in a physician, rather than one of those clever PhD folk.
Even so, I’m pleased that you didn’t end up injured.
What's the proper way to do this without dying then? As I may want to give my fork a service in the coming months and would rather not lose an eye in the process. I've rebuilt an old Sektor before but afaik it was super simple inside and didn't have any fancy air cartridge stuff.
And you wonder why bike shops are struggling with such competent mechanics at home
I’ve half a spoke with nipple that’s in my neighbour’s garden.
There was a pretty major dent in my old garage roof that I made with a bit of fork internals. Can't exactly remember why, I think something was stuck down and immovable, until it wasn't and then it really wasn't.
Not quite the same but the first time I ever serviced a stuck motorbike brake, I fired a piston pretty much into orbit with compressed air... I caught a wee glimpse of it flying over the house out behind ours but god knows where it landed.
And you wonder why bike shops are struggling with such competent mechanics at home
Lolz ?
DrP
In the '80's two people at work didn't understand procedures correctly and tried to remove a large steel (10 litre nitrogen charged) accumulator with 280 bar of hydraulic pressure behind it. The clue should have been needing a pipe on the spanner to get enough leverage.... Luckily they weren't killed.
I still use the repaired mezzanine railings it blew through above and the dent in a heavily reinforced concrete floor where it landed as useful visual aids when doing new starter inductions.
”What’s the proper way to do this without dying then? As I may want to give my fork a service in the coming months and would rather not lose an eye in the process. I’ve rebuilt an old Sektor before but afaik it was super simple inside and didn’t have any fancy air cartridge stuff“
As someone that works with high pressure stuff for a living (up to 300bar ish ).
Eye protection and keep it aimed away from you at all times. Even if you think it’s not pressurised, treat it like it is and you won’t go far wrong.
Oh and read/understand the manual.
And you wonder why bike shops are struggling with such competent mechanics at home
you think similar has never happened in a bike shop?
Reverbs make spectacular oil splatters and holes in ceilings when you get sidetracked doing a service. How I'm still married is also a good question. If anyone needs any reverb spares, I'm sure there's some above my kitchen.
IIRC the first Ohlins RXF36 coil forks had a recall for firing the top caps out while being ridden.
1997 Kona Caldera with Judy TTs taking a short cut home across a field , must have hit a small hole and got shot in the chest , boy did that smart !
you think similar has never happened in a bike shop?
A mechanic I worked with lost the tip of his finger when it got caught between chain and chainring on a fixie.
He was resting his finger on the chain to check tension and rather absent-mindedly spun the rear wheel with his other hand - which caused the chain to move as well.
One shop I worked in had a specific suspension department within the workshop and the guy there was very very thorough in depressurising. Went through that step twice on every fork/shock to be absolutely certain and always wore safety glasses.
There was a reason for that - at his previous place the workshop had ended up with a large hole in the ceiling from a pressurised shock being pulled apart without sufficient checks in place.
A mechanic I worked with lost the tip of his finger when it got caught between chain and chainring on a fixie.
I was working with a guy setting up the injection system on a diesel engine, which involved removing the timing cover and turning the engine over using an enormous Cresent wrench to check that the injectors fired at the right point. Unfortunately, his hand slipped and his finger went between two timing gears (which have clearances measured in thousands of an inch). He was screaming in pain for me to get his finger out, but there were multiple gears in the chain so I had to work backwards through them to figure out which way to turn the crankshaft, with him screaming to hurry up. Probably took a couple of seconds, but seemed much longer. His finger tip looked like a crinkle cut potato chip (dipped in ketchup) when it came out.
Same spring comps I've got. Laser if I remember right, nothing special but solid!
I've even been a bit naughty and skipped the taking the disc off the hub part if it only needs jacking up a bit. Not warped one yet, although I wouldn't recommend it as standard practice!