Mountain Bike Reviews Forum banner
1 - 6 of 6 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
I recently built up a blur using a new 2004 frame which came with a progressive 5th element shock. Now that I have it built I have been trying to set the pressures in the fork and shock, but I am running into some problems (?) with the shock. When I hook the shock pump to the shock it never registers any pressure even when the pump is screwed all the way on. I have tried 2 different pumps and I get the same result. I know it holds some pressure because I can stick a pointed object in the valve of the shock and release pressure.

Also if I air the shock up to the recommended pressure for my weight (around110psi) the sag is way off. If I up the pressure to the max (150) it gets my sag pretty close to 15mm, but on a short ride around the block the shock got close to bottoming out (judging by the position of the o ring). Is this shock functioning correctly? Any idea what is going on with this shock?
Thanks
 

·
Registered
Joined
·
97 Posts
Two questions, how much do you weigh and where did you find the "recommended" pressure? My guess is the pressure setting you're using is for a 5th element coil shock piggyback reservoir and not for an air shock. I would suggest setting the main air chamber at 10 psi above your body weight and the IFP chamber at 55 psi to start. (i.e. - If you weigh 150 lbs, set the main chamber at 160 psi.)

As for not seeing pressure on the gauge, it's not an unheard of problem. The valve core is set too far in to press against the end of the pump fitting.
 

·
certified mtb addict
Joined
·
163 Posts
Bromine said:
The valve core is set too far in to press against the end of the pump fitting.
Use a valve core removal tool to back out the valve a little bit. A little dab of blue loc-tite on the valve's thread may be a good idea if you do this (the inner thread).

Also, check post #4 in this thread http://forums.mtbr.com/showthread.php?t=231965 for the recommended pressures.

I weigh about 80kg (~180lbs) and run about 125psi in the main chamber and about 95psi in the IFP chamber.
 

·
certified mtb addict
Joined
·
163 Posts
The chart is correct, it is the same as the one that came with my bike and is what I used as a starting point for the pressures.

I run what I posted above, much lower than Bromine recommended, but slightly higher pressures than the official chart recommends. Bromine's suggestion of 55psi in the IFP chamber is too low - there is a sticker on my shock stating to inflate the IFP chamber to between 75 - 125psi. Also important - the IFP chamber must be inflated before the main chamber.

The valve issue may also be causing the pump to give a false reading - perhaps showing a higher pressure than is actually in the shock (i.e. showing the pressure in the pump rather than in the shock). Play around a bit with the valve and once you start getting good pressure readings, then try the numbers from the chart.

This TF Tuned page has some good reading about the 5th air shock.
 
1 - 6 of 6 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top