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Do I have a faulty shock? Xfusion O2 Pro RL


MarcoDB97
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Hi all, this is my first post so if it's in the wrong section or something just let me know and I'll sort it out.

 

So the reason why I'm asking is because I recently bought a 2020 Scott Spark 970 with a Xfsuion O2 Pro RL (165/45) rear shock and it's my first dual suspension bike now after taking it for the first ride the suspension was too soft and a friend of mine told me how to set up the sag and I did a bunch of research and then bought a shock pump.

 

While trying to set it up I was pumping up to 200psi, the shock is limited at 280psi according to the Scott representative I spoke to earlier this week, and I was still not able to get 20-25% sag recommended by Xfusion setup guide (it was still sitting in the 30% range at 200psi).

 

I only weigh about 82kg with all my gear which is why I thought 200psi was too high. At the moment after sitting on the bicycle the o-ring is about half way up the shock and this is with about 170psi.

 

so as not to damage it I stopped trying to set it up and waited to get to my trails today where there is a shop that is well known in JHB South area. After myself and the guy at the shop tried to set up the sag again, he was also pumping over 200psi, he told me he reckons it's faulty. I guess I do trust his opinion but wanted to know if anyone with the same shock has had any similar issues or tips for me?

Edited by Marco De Barros
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Rather bounce, jump on your bike and see if you get to 90% travel then decide, I have a Scott Genius 2015 with a Xfusion rear shock and ride with around 30% sag. You will feel if its too hard, it will bounce all over the place instead of helping you.

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Sounds like the negative air chamber might not be properly charged. Start by emptying the shock very slowly. Next, hold the rear wheel and pull the top tube up hard and hold it there for about 10 seconds. You might feel the air from the negative chamber release and the shock extend further. Then attach the pump and charge it 30 PSI at a time. After every 30 PSI, move the bike through around 30% of the stroke slowly around 10 times. Repeat until you get to 220 PSI. That should get you close to 25% sag.

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Sounds like the negative air chamber might not be properly charged. Start by emptying the shock very slowly. Next, hold the rear wheel and pull the top tube up hard and hold it there for about 10 seconds. You might feel the air from the negative chamber release and the shock extend further. Then attach the pump and charge it 30 PSI at a time. After every 30 PSI, move the bike through around 30% of the stroke slowly around 10 times. Repeat until you get to 220 PSI. That should get you close to 25% sag.

 

 

I was thinking of emptying the shock but wasn't sure if that was okay so I'll give the negative air chamber set up a shot once I hear back from the people I emailed. Thanks for the advice!

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If you're near the store you got the bike from...pop in and ask them to help you set it up. That way, if there is a problem, they can see it first hand.

 

I bought the bike from Cape Town and it was shipped to a shop here and they told me to contact the one I bought it from, kind of thought that the shop here would have set it up correctly. so I've sent out emails to the shop and Scott, so we'll see what happens when they reply. 

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200psi isn't very hard. If you ride it the neg pressure will equalize quickly if you feel the suspension is a bit soft, so I don't think it's that.

 

The whole "pump it to your weight in pounds" is a very bad guideline, especially when it comes to rear shocks. With rear suspensions the leverage ratio comes into play.

If you are on 30% at 200psi, then my thumbsuck is that you will ens up at around 225-240psi to get the 25% sag that you like.

 

The 250 psi is still far off. Put more air in the shock, and find a shop that has more knowledge.

Edited by PhilipV
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200psi isn't very hard. If you ride it the neg pressure will equalize quickly if you feel the suspension is a bit soft, so I don't think it's that.

 

The whole "pump it to your weight in pounds" is a very bad guideline, especially when it comes to rear shocks. With rear suspensions the leverage ratio comes into play.

If you are on 30% at 200psi, then my thumbsuck is that you will ens up at around 225-240psi to get the 25% sag that you like.

 

The 250 psi is still far off. Put more air in the shock, and find a shop that has more knowledge.

 

Will do, thanks. The person I am in contact with from Scott is setting something up with Ridgeway Cycles and I'm sure they will properly investigate this for me.

 

So if if I get to around the 240-250psi mark its not going to damage seals or anything?

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I have a new X-fuision on my flare max, one thing to check is how deep the stanchion pushes in  with no air in the shock. Mine stops 5mm short of the full length, thus calculation sag and checking for  full travel use requires keeping that 5mm that can never be used in mind.

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I have a new X-fuision on my flare max, one thing to check is how deep the stanchion pushes in  with no air in the shock. Mine stops 5mm short of the full length, thus calculation sag and checking for  full travel use requires keeping that 5mm that can never be used in mind

 

Okay that's interesting I'll have to check, I never got the shock empty so wouldn't have noticed that but could make sense

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Have you read the setup guide? I'd suggest starting there, you'll find the manufacturer has a pretty good idea of how it works.

 

As mentioned earlier, shocks with large volume negative springs need to equalise before they appear to hold pressure. If you haven't followed this procedure you're not going to get it to work properly except eventually by accident.

 

Also, if max pressure is 280, pump it to 280 and see what sag it gives you. No point only taking it to 70% pressure if it's still got too much sag.

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Have you read the setup guide? I'd suggest starting there, you'll find the manufacturer has a pretty good idea of how it works.

 

As mentioned earlier, shocks with large volume negative springs need to equalise before they appear to hold pressure. If you haven't followed this procedure you're not going to get it to work properly except eventually by accident.

 

Also, if max pressure is 280, pump it to 280 and see what sag it gives you. No point only taking it to 70% pressure if it's still got too much sag.

I have read the manual but it just says after installing and checking that there are no clearance issues one should continue to pump it up to the recommended sag 20-25%, so nothing specifically about negative air chamber

 

 So should I follow the process the_bob pointed out?

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There are 3 kinds of "losing pressure" when inflating a shock.

 

1. Disconnecting and reconnecting the pump - when reconnecting the pump a certain amount of air will be released from the shock into the hose. This usually causes a pressure drop of about 10psi. The reading on the gauge before disconnecting the pump is correct - the chuck on a shock pump is designed to not release air from the shock when disconnected.

 

2. Large volume negative air springs use the air from the positive spring to charge. This is why on RS Debonair and Fox EVOL air cans, among others, the shock needs to be inflated in small increments, equalising pressure in between. Failing to do this will create a harsh breakaway and topout, and also make it look like the positive spring is losing pressure when the air is actually just being transferred via a port or valve to a different part of the can.

 

3. The shock is actually leaking.

 

If, once you've cycled the shock about 20 times, it still seems to be losing air, you probably have an actual leak. Try the method the_bob describes and see if you get a decent result.

 

As for maximum pressures - don't be scared to use the max pressure if you need to. These things are designed with a fair amount of safety margin.

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