[Mr. Furious]

So I've switched from a 6" TPC+ dual crown down to a more reasonable Pike426 Air U-Turn for my hardtail. I've had a few rides on the Pike and like it so far.

I've mostly been using it in the 110mm setting and I noticed clicking or knocking sound at the very beginning of the stroke. The sound goes away if I move up to 120mm or 140mm of travel which I figure is weird. If it were a bushing problem I figure that knock should always be there, regardless of the travel setting .. right?

The headset feels fine at each of the bottom and the top of the headset, and the sound is definately coming from the fork and not the headset.

I weigh 185lbs on a good day and have 150psi in each of the positive and negative air chambers. I googled the hell out of the Pike and it looks like no one is having this issue except me.

 

[bushrider]

I read about this issue on MTBR.
Apparently the fix is to run slightly higher negative pressure than positive pressure.
Try running 10psi more in the negative.

I have the same fork (454 u-turn air) but havent had an issue.
I also run mine at 110-125mm most of the time.

 

[Mr. Furious]

Thanks for pointing that out - I wasn't registered with MTBR until today.
I'll try the negative air pressure thing - I also see some guys my weight running lower air pressure in the positive chamber.

 

[|S2|]

Did you find that less positive air pressure fixed the issue? I have a new revelation 426 air u-turn that has the same problem. All the way out it's fine, all the way in it happens intermittently and any setting between there it happens all the time. I appreciate any info you might have on it. Thanks.

 

[rhys.l]

Yep, exactly same problem here. Although I have no issues at the extremities of the travel, just in between and I have a 409 (which obviously would make no difference). I found it went away after I did a full rebuild of the air side (and even thought I found out why it did it) but after a few rides it was back again.

I have pretty much no knowledge as to how an air cartridge works, but whilst rebuilding them i noticed one of the pistons that is clamped and held down by one of those u-shaped circlips still had some play in it even when the circlip was pushed all the way on over the washer which sits ontop of the piston. I put another thin washer under there to solve the problem but there was still a little play by memory. I have no idea if that would make any sense in relation to being the cause of this problem, just thought I'd put it out there though.

 

[Banshee Rider]

This is a trait of the air u-turn system according to SRAM. My co-workers Revelation did the same thing, only in the 120mm setting, and only in the first half inch of travel, regardless of air pressure settings. For me, it's really not an issue since I either have my fork at 140 or collapsed all the way. But for alot of people, it could be a deal breaker, because its pretty annoying. According to the tech reps at SRAM, there's no straight fix. You just have to live with it or find something else.