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  1. #1
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    '04 Z150 FR SL losing pressure in cold

    I've seen this happen on three different forks now, including my own. On very cold, technical riding, the left leg air pressure in the positive air basically disappears. A very good mechanic (shop owner) who has been on these rides speculates that the cold weather is causing the air volume to decrease so dramatically that the seal between the negative and positive air chambers is failing when the fork is taking hits. That chamber will not hold air well after the loss, although the fork will still work by increasing the air pressure in the right leg and adjusting the negative air accordingly. Again, in the past week, I've seen this happen on three separate '04 Z150 FR SL's. Later, when it warms up, the fork holds air fine. Does the speculation about the cause of the problem make sense and does anybody know a fix? This is one fantastic fork other than this issue, so I would like to figure out how to fix this. Thanks, Mike

  2. #2
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    same with my 04 z1 sl

    happened saturday. temp was around 22 deg. faren. started with 150 in the pos and ended up with 120 after the ride. also a great fork and would like to prevent it.
    fork is 2weeks old and running 10wt oil.

  3. #3
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    Quote Originally Posted by staz
    happened saturday. temp was around 22 deg. faren. started with 150 in the pos and ended up with 120 after the ride. also a great fork and would like to prevent it.
    fork is 2weeks old and running 10wt oil.
    Out of curiosity......How were you able to determine what pressure it had after the ride?

  4. #4
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    Shouldn't happen.

    Quote Originally Posted by Mike Brown
    I've seen this happen on three different forks now, including my own. On very cold, technical riding, the left leg air pressure in the positive air basically disappears. A very good mechanic (shop owner) who has been on these rides speculates that the cold weather is causing the air volume to decrease so dramatically that the seal between the negative and positive air chambers is failing when the fork is taking hits. That chamber will not hold air well after the loss, although the fork will still work by increasing the air pressure in the right leg and adjusting the negative air accordingly. Again, in the past week, I've seen this happen on three separate '04 Z150 FR SL's. Later, when it warms up, the fork holds air fine. Does the speculation about the cause of the problem make sense and does anybody know a fix? This is one fantastic fork other than this issue, so I would like to figure out how to fix this. Thanks, Mike
    I have a couple of these forks, and we've even had some single digit nights around here. I have always been impressed how long these forks go without losing pressure. The really low positive pressure in both legs seems to maintain pressure for long periods. I'm very anal about checking pressure before each ride, normally, but I've continued to see normal pressure for so long that I don't even do that anymore. Pressure loss like you're describing shouldn't be occuring when things are working as they should.

  5. #5
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    the psi gauge

    Quote Originally Posted by Blue Shorts
    Out of curiosity......How were you able to determine what pressure it had after the ride?
    i just got out the pump and took a psi reading

  6. #6
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    Then why has it happened on three different forks? That's the point that makes me think it's a systemic issue to the design and not a single fork problem. I'm really not exagerating on that point of three forks- the LBS I race for gave us great deals on these forks and also runs it on a demo that employees of the LBS ride often - so several people I ride with have the fork. Otherwise, I would write it off to a problem with one fork, tear it down, rebuild it, and see what happened. So, again, any suggestions would be welcomed. Thanks, Mike

  7. #7
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    Quote Originally Posted by staz
    i just got out the pump and took a psi reading
    The drop in pressure that you're seeing is simply do to the way you are measuring the pressure. Your fork is not losing air due to the cold weather.

    When you add air to your fork, the pressure indicated on the guage is correct. If you remove the pump and re-attach it to take a reading, it will show a lower pressure. The reason is that when you re-attach the pump, air from inside the fork enters the pump....thus lowering the overall pressure.

    Try this experiment:

    Pump the fork up to your normal pressure. Remove the pump and them re-attach it. You'll notice that the pressure dropped. The pressure will now read lower because of the phenomenon indicated above.

  8. #8
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    Quote Originally Posted by Mike Brown
    I've seen this happen on three different forks now, including my own. On very cold, technical riding, the left leg air pressure in the positive air basically disappears. A very good mechanic (shop owner) who has been on these rides speculates that the cold weather is causing the air volume to decrease so dramatically that the seal between the negative and positive air chambers is failing when the fork is taking hits. That chamber will not hold air well after the loss, although the fork will still work by increasing the air pressure in the right leg and adjusting the negative air accordingly. Again, in the past week, I've seen this happen on three separate '04 Z150 FR SL's. Later, when it warms up, the fork holds air fine. Does the speculation about the cause of the problem make sense and does anybody know a fix? This is one fantastic fork other than this issue, so I would like to figure out how to fix this. Thanks, Mike
    What change in pressure are you noticing?

  9. #9
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    The positive air pressure in the left leg is disappearing. Basically, the fork starts having no compression resistance. This only has happened in very cold (less than 15 degree) riding on technical terrain. Right leg (the one w/o the doppio air cartridge) continues to hold pressure. Negative air works fine. Exact same problem, three different forks, three different riders. Can make work adequately by doubling the air pressure in the right leg, decreasing negative air by about 20%. Left leg holds pressure when get back into the house, bleed all air out fork, re-pressurize. Held for two warmer (above 30 degree) weather rides, just fine, then bled out again on next real cold ride. This is a very sudden occurence- JRA after riding a technical section, I brake, whoa, I'm, using 5 inches just from braking. Logic tells me probably happened under compression going through the tech. Another rider had the same thing happen with one of these forks on a Moment abot 15 minutes later. Any advice appreciated. Peace, mike

  10. #10
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    Couple of things.

    Quote Originally Posted by Mike Brown
    The positive air pressure in the left leg is disappearing. Basically, the fork starts having no compression resistance. This only has happened in very cold (less than 15 degree) riding on technical terrain. Right leg (the one w/o the doppio air cartridge) continues to hold pressure. Negative air works fine. Exact same problem, three different forks, three different riders. Can make work adequately by doubling the air pressure in the right leg, decreasing negative air by about 20%. Left leg holds pressure when get back into the house, bleed all air out fork, re-pressurize. Held for two warmer (above 30 degree) weather rides, just fine, then bled out again on next real cold ride. This is a very sudden occurence- JRA after riding a technical section, I brake, whoa, I'm, using 5 inches just from braking. Logic tells me probably happened under compression going through the tech. Another rider had the same thing happen with one of these forks on a Moment abot 15 minutes later. Any advice appreciated. Peace, mike
    Mike, I still say this is not normal, regardless of the temperature you're experiencing. Maybe some crazy Antarctic minus 50 degrees would adversely affect any fork, air or coil, but your temperature is not that extreme to dramatically affect fork performance, much less lose a lot of air. Someone awhile back posted some good scientific info on how altitude and ambient temperature affected air suspension. It took some unbelieveable extremes to make much of a difference. Seals would have to become so hard that they wouldn't work to let air escape at the rate you mention. Now you may indeed have a failure of some kind, or are on the verge of having a seal failure, to cause your air loss. I'm just saying that at the temperature you're riding in, an air fork or air shock will work, and at worst will perhaps exhibit more stiction because of cold temps.

    I've ridden my two Z150 SLs in below freezing weather numerous times, along with numerous rear air shocks, with no problems. I even seen some freezing water collect around the fork seal/stanchion area with no adverse effects. You may indeed have a problem going on here, but I don't think it is inherent to this fork or the temps you are riding in. It sounds like a unique situation for sure. Have you talked to Marz for any tech input on this? Maybe Brian, who posts here frequently, can comment on this.

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