Posts
23
Joined
1/28/2008
Location
GB
Edited Date/Time
1/18/2019 4:52am
Hi,
I just bought a second hand trax shock. I've installed it and it seems to have a slight knock when lifting the bike up from the back, as if the bushings are gone. But when looking at the bushing there is no play in them. is this just the trax feature and is pretty normal? or should I be looking at getting the shock serviced, although it was done 6hrs ago according to the previous owner which he gave me his receipt for proof.
The bike is a 2018 sxf350 with only 18hrs on it so linkage bearings are all fine.
I just bought a second hand trax shock. I've installed it and it seems to have a slight knock when lifting the bike up from the back, as if the bushings are gone. But when looking at the bushing there is no play in them. is this just the trax feature and is pretty normal? or should I be looking at getting the shock serviced, although it was done 6hrs ago according to the previous owner which he gave me his receipt for proof.
The bike is a 2018 sxf350 with only 18hrs on it so linkage bearings are all fine.
My CV Fork is out for Service so ask the Suspension Tuner to replace the Top Bearing on the Trax
Have the trax system checked, the springs inside might be broken, it happens.
Would like to avoid the cost of sending the shock to the mainland be serviced again if possible after such few hours.
The Shop
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Heres a video i took last night of the knocking albeit not a good one, difficult when your by yourself aha https://www.dropbox.com/s/dkkf6kvrp634r92/IMG_0593.MOV?dl=0
There are some coil-compression springs in this shock, but nearly all shocks use them. And compression springs don't normally break.
But...perhaps there is something about this shock where "the springs: were a problem.
With that....I'll add this.
Often bushings look and feel perfectly fine but still end up making noise when the forces applied via the swing arm are there. So...this could be a bushing or bearing thing.
Secondly, WP often uses what is called a "top-out" spring in their shocks, and they are beefy. This is a short but large spring that sits on top of the seal head that cushions the blow when the shock goes to full extension. Some shocks use a spring, other shocks use a hydraulic top out. Now...what matters here is that the top out spring counters the effect of the main spring when the shock goes to full extension, meaning the shock is not as tight at full extension as other shocks. That can me the movement coming off of full compression is soft.
You could measure for this by putting a zip tie on the shaft, with the bike on the stand, and then seeing how far you can compress the shock by pulling up on the tire with your hands.
NOW...that said, if this is not a bushing or bearing problem, what I really think it might be is free piston top out. I say this because I often open up a lot of recently serviced WP shocks where the free piston is knocking against the top of the reservoir when the shock goes to full extension. This means at full extension, the pressure in the shock is zero, giving the top out spring even more effect, (F=PA against the area of the rod).
This is because the service person did not properly set-back the free piston before filling and charging the shock, made all the more likely when service dudes use shock pumps to purge trapped air. And...free piston top out is way more noticeable on a WP shock because of their big top out springs.
Is that making any sense?
You only get this problem with free pistons, and not with bladders (but I do prefer free pistons over bladders). So does Ohlins.
Bottom line, I would not ride the bike until you fix this because if it is this, then the free piston is hammering against the shock body each time the shock goes to full extension.
Thanks to Slavens for the image.
That large but short spring on top of the seal head is the top out spring. This wants to compress the shock when it's at full extension and with shock that have softer springs or little pre-load, it can produce some slack. But again, I have never seen this cause a knocking noise but would exacerbate the free piston top out matter.
the internal springs we are talking about are the ones inside the trax mechanism on the shock.
I wouldn't expect the top out spring to be broken internally. The shock has been ridden with this knock happening and still performs better than the oem one which came on the bike, so therefore that rules out that anything internally to do with the top out is broken.
I've spoken to the suspension tuner that last serviced the shock, and he said that it was normal for these shocks to knock like this with the trax feature when being lifted up. I've also looked at the were the movement is coming from and it is definitely from the the trax mechanism, and he has ensured me that on the last service these trax springs would of been checked and replaced if needed. Also said that it is unlikely for the newer model traxs shocks to have the broken springs because of the tighter tolerances and strong springs.
Coil compression springs can break, but...it's very very rare. They are simple and super tough. You can get millions of cycles out of them.
And the noise in the video is...well, unacceptable. I can't think of a noise like that ever being normal based on how I see any shock designed. Something is not right.
The bushing/bearing thing is a possibility, but I'm still hot on the likelihood of the free piston topping out. More so because of how often I see this, even after a WP shock has been serviced from a reputable tuner.
Okay...so if you want to test my theory on the free piston topping out, take the shock out, remove the main spring, and see how soft the initial compression is. It's also likely that the shock is not even fully extending during this test so test to see if you can pull the shaft out further.
If the free piston is NOT topping out then the shaft should easily and firmly glide to full extension, with a sharp stop.
You could also depressurize the shock, remove the hex screw from the top and measure the distance down where the free piston is. It should down at least 30mm.
https://www.dropbox.com/s/45xa557gbloc0f1/IMG_0600.MOV?dl=0
This video you can see the trax mechanism extending.
1. Someone removed the top out spring from the seal head.
2. The free piston was never properly set and is topping out at full extension, (assuming you have not lost oil).
Now...the only other consideration is that the shock was shortened. Shortening a shock means putting a top out spacer inside, and these can defeat a top out spring or end or stroke hydraulic lock.
IMO, this is not WP's responsibility. They don't owe you an explanation. If you get one, great. If you don't, don't be upset.
The shock is not behaving as designed, and as I noted earlier, it's very common for shops to not properly set the free piston.
Pit Row
This rod is inside the trax unit that sets on the lower clevis. Those springs can break or in my case the threaded parts can unscrew.
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