Fox shocks

[2stroke4stroke]

I've dragged the old units out the spares box and wonder if anyone can recall what pressure they should be pumped to.

I did read somewhere that 200 psi was the figure but that seems more like that for air spring units and i certainly don't think my local Fox dealer had the equipment to pump or measure to that sort of pressure when he set them.

I may have had a manual but that will be long gone.  Any advice appreciated.

[tlrmark]

Still have a manual from the early eighties.

Quote,  We use 200 PSI of nitrogen. Pressure is not critical however. Anything from 100 to 300 psi will work adequately. Nitrogen works best, but if it is not available you can use air.

[2stroke4stroke]

13 hours ago, tlrmark said:

Still have a manual from the early eighties.

Quote,  We use 200 PSI of nitrogen. Pressure is not critical however. Anything from 100 to 300 psi will work adequately. Nitrogen works best, but if it is not available you can use air.

Thanks Mark.  I'm fairly sure the dealer's bicycle trackpump did not dispense nitrogen ☺

[still trying]

Hi, 

I've been working on setup of shocks/springs recently and have found that for my bikes system the gas pressure helps tune the compression, i.e, it works with the spring to create progression by adding more resistance at the top end of travel and less at the start .

This is because as gas is compressed the pressure increases exponentially, so it affects the final travel more than the initial travel.

Use it to fine tune the suspension for bottoming. Set the spring sag for your weight and the small stuff. Then start adding pressure to suit, NOTE when you get it about right Reset the sag, as any pressure added will affect this. Then its back to testing, i.e, riding.

It looks like the limits pressure wise for the shock is 300 psi, Don't exceed this for obvious reasons. But 0-300 would depend on your preference.

The factory settings are to suit the weight of the average rider and the weight of the bike, hence tune to suit yourself and your style/level of riding.

Nitrogen is the perfered gas, but air is ok and cheaper during testing. To get access to nitrogen, try performance tyre shops, they usually have a bottle and appropiate regulators hoses etc.

Edited May 10, 2017 by still trying

[pmk]

On 5/7/2017 at 0:01 PM, 2stroke4stroke said:

I've dragged the old units out the spares box and wonder if anyone can recall what pressure they should be pumped to.

I did read somewhere that 200 psi was the figure but that seems more like that for air spring units and i certainly don't think my local Fox dealer had the equipment to pump or measure to that sort of pressure when he set them.

I may have had a manual but that will be long gone.  Any advice appreciated.

I assume, and maybe incorrectly, these are Fox Shox coil spring type units with or without reservoirs.

If they are Fox Airshox or Dual Airshox, those uses far different pressures to set up the air springs.

Thor Lawson site states 200 psi off road, 100 psi for trials and road.

Edited May 31, 2017 by pmk

[2stroke4stroke]

Correctly assumed pmk.  Put 150 in though it gradually leaked out but the units still performed well.  No doubt a stripdown would be in order.

[pmk]

17 hours ago, 2stroke4stroke said:

Correctly assumed pmk.  Put 150 in though it gradually leaked out but the units still performed well.  No doubt a stripdown would be in order.

150 PSI is a pretty standard pressure we use when building modern shocks.  Correctly it is 10 atmosphere or 147 PSI.

The 100 PSI is fine for slower shafts speeds that are not sustained and will provide a bit more compliance on the initial bump. 

You did not mention where the leak is at.  Those should be an easy rebuild and parts should be reasonably priced.

If those are the red, white, blue FoxShox, they always had a great appearance to them also.

 

[2stroke4stroke]

Now red, white, blue and rust brown☺  I assume the seals need renewed and, as you say, a simple job, if the seals are a standard obtainable size.  I've never been inside them but they are probably a bit cruder than the Fox mountainbike ones I have worked on.

 

[pmk]

3 hours ago, 2stroke4stroke said:

Now red, white, blue and rust brown☺  I assume the seals need renewed and, as you say, a simple job, if the seals are a standard obtainable size.  I've never been inside them but they are probably a bit cruder than the Fox mountainbike ones I have worked on.

 

Having fully rebuilt Fox MTB rear shocks, moto stuff, especially vintage stuff is super easy.  No micro parts, just simple old school shocks.

Even my Curnutts, while a bit more intricate, are super easy.

Check Thors site to see if the parts are special or standard.

[tony27]

On 6/3/2017 at 5:49 AM, 2stroke4stroke said:

Now red, white, blue and rust brown☺  I assume the seals need renewed and, as you say, a simple job, if the seals are a standard obtainable size.  I've never been inside them but they are probably a bit cruder than the Fox mountainbike ones I have worked on.

 

For seals & other parts Thor Lawson in the states is the man to use. I bought the parts & manual off him when I rebuilt mine but rather than buy the internal bush I made new ones out of aluminium bronze that I had left over from a job at work

http://evolutionsuspensionproducts.com/ThorLawson/index.html