Nitrogen Pressure

[BadgerMan]

I just did an oil change in my YZ250F's rear shock and I have not had it charged yet. After the final bleed I just put in 125psi of filtered compressed air. My seat of the pants testing in the garage could detect no difference from the pre-oil-change charge of nitorgen that was in there. I am tempted to just go riding with the 125psi and see how the shock works at the lower pressure.

How does pressure (air or nitrogen) affect shock performance and will I notice a difference between the 125psi and 160-170psi of nitrogen or compressed air?

BTW, I am just a semi-fast and fairly old woods rider and I weigh 170 lbs.

 

[marcusgunby]

I have ran shocks as low as 9 bar and as high as 12bar to see if i could tell and i honestly couldnt.I would however run it at least the recommended minimum as i can see no gain in going lower-if you want a softer feel try a lighter fluid.

 

[BadgerMan]

Nawh, I'm not really looking for a softer feel. I am running Mobil-1 ATF in the shock and even at 7.5wt, I really like the way the shock feels. I was just curious about the 125psi of compressed air so I stuck the shock back on the bike and started bouncing on it. I truly could not tell any difference.

BTW, I do not know what the recommended (by Yamaha) charge pressure is for my bike but 160-180psi seems to be the consensus based on my searches.

Thanks for the reply.

 

[marcusgunby]

As far as i know most jap bikes OEM at 10bar.

 

[Jeremy Wilkey]

B-man,
I would charge that shock a little more... you risk cavitation, and subsequently seal-head rock.. This will damage your shock body!

As for the air no big deal, for a consumer...


Best Regards,
JEr

 

[BadgerMan]

Yeah, I was afraid of that but I thought it might be OK as long as I was not riding supercross with the bike. :eek:

Anyway, I stopped at a bicycle shop today and bought a shock pump (really neat little thirty dollar gizmo) and set the pressure at 160psi. I can't feel any difference, but better safe than sorry. I am going to tear it down after a few rides and check the condition of the ATF and also for oxidation in/on the res. cap.

BTW, the shock pump looks like this,

http://www.beyondbikes.com/images/large/pu9000.jpg

Thanks again for the advice.

 

[dave186]

has anyone else used one of those shock pumps? Id like to get one so i can experiment with different pressures.

 

[BadgerMan]

Hey, it works great! It has a bleeder button underneath the dial so you can set the pressure very accurately and you hardly lose any pressure when you disconnect it. It does take about fifty or sixty strokes to get my shock up to 160psi though. Still a lot cheaper than $250.00 for a tank and regulator.

 

[Wanabe]

that pump thing looks pretty cool. I've never worked on the shock myself and I've been wanting to service it in the next couple of weeks. Are the shocks on pedal bikes and dirtbikes the same are is there some kind of adapter needed? And do you know if most bike shops have these things?

Eric

 

[Vic]

Originally posted by Wanabe
hey this is wanabe's girlfriend he won't let me ever type anything so I am while he isn't looking. Shh...don't tell him he'll be pissed!!

That's strange. He let's his wife type anything she wants. :eek:

 

[Mac]

Originally posted by Jeremy Wilkey
As for the air no big deal, for a consumer...

Best Regards,
JEr

Jeremy, could you please elaborate on this?

I thought air wasn't recommended for whatever reason so I brought my shock to work with me and rigged up a valve to fill my shock with N2 but I also have a compressor at home that will compress air up to 250psi which would be much easier for me.

What are the pro's/con's using air vs N2

Thanks

 

[Jeremy Wilkey]

Mac,
What I'm saying is if some dude wants to put Dry clean air in his shock for one ridse its not the end of the world. However thats a far cry from the right way to do it or what anyone should do in anything other than an emergency. As for the advantages, Nitrogen has know and predictable chemical and physical charahchteristics.

Regards,
Jer

 

[BadgerMan]

Here is a link to another thread on the air vs. nitrogen subject.

http://dirtrider.net/forums3/showthread.php?threadid=40071&highlight=nitrogen

It seems to me that there are many instances where compressed air is, or has been used for similar purposes.

-Automotive air assist shocks
-Fox air shocks
-ATB shocks and forks

I'll let y'all know the results of my testing. My only real concern is corrosion (inside the bladder) due to any moisture that may be in the air. It seems like regular maintenance would prevent that though.