Pike Dual-Air losing neg. air? Wiper seal blowing out
I have had two new Pike Dual-Air RCT3 160 forks fail on me; one on it's 5th ride, and one right out of the box.
The first one was working perfectly on it's first 4 rides. The only thing I did to it after installing was set the sag. Halfway through the 5th ride, it topped-out hard when catching a small amount of air. I pulled over and played with the travel adjustment, but it wasn't working. The fork was at full extension, even when I was sitting on it (no sag). I was able to ride it home gently, but it was topping out the whole way. Compression felt normal.
The next day when I was rolling it into the shop, I felt the front end compress fully as if it had no air. When I lifted up the front, the left seal pulled out of the lower. The shop had it for a couple days and claimed they were having trouble getting through to SRAM, so I ended up calling Backcountry.com where I bought it, and they agreed to send me an exchange.
Not expecting any issues with the new one, I cut the steerer, installed it, stickered it, and then sat on it for the first time check the sag. I noticed immediately there was no sag at all, so I figured I just needed to let some air out. I put the pump on it and kept letting small amounts of air out but still it was not dropping. I removed the shock and used a small Allen to depress the valve, and while seated and holding the front brake I rocked back and forth a few and times. And then 'POP!' the left seal blew out of the lower again.
My theory is that the negative air chamber is leaking into the lower, and the pressure is blowing out the seal. Does that make sense? And why would I get 2 in a row with this issue? Is it possible they are shipping from Backcountry with too much air in them, and perhaps during the transport flight the air pressure is blowing the seal? Any other logical explanation? I'd love to send it back to SRAM to get their take on it, but it's been easier to get it exchanged instead.
Anyone else have this issue?
Last edited by *MoonDogg*; 05-19-2014 at 11:17 AM.
Your theory makes good sense to me. Did you have proper negative and positive pressure before it happened?
I don't know the innards of this fork but I had a similar issue on my Reba XX. In my case the problem was my fault; during a service of the fork I installed one of the sliding piston spacers backwards on the main air shaft, which resulted in me pressurizing the fork lower when I thought I was pumping up the negative air chamber. The fork behaved oddly (due to no negative pressure) and all of a sudden the air blew out of the lower (it came out the bottom in my case). I took it apart, fixed my mistake, and the fork worked perfectly after that.
In other words, I suspect there was poor QC on your forks. Chalk it up to bad luck and try again. It is odd that your shop could not fix this -- these forks are not very difficult to service (even I can do it). I assume they didn't want to touch it unless they knew SRAM would pay.
Note that a pressurized lower (which should not happen) should not by itself make the fork stick in position. That was likely caused by something wrong in the air chamber, which in turn caused the leak into the lower.
There is only one valve, and I believe it auto balances? anyway, I set the proper pressure on the first fork, but didn't get that far on the second.
Originally Posted by Jfloren
The fork wasn't stuck in position, it would compress normally. It just would top out because there was no negative air pressure to prevent it (my guess)
Originally Posted by Jfloren
I've put my 3rd fork on and it's working normally after 3 rides. Hopefully it stays that way as I have some races coming up.
Thanks for your comments.
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