OZ ATV :: The Australian ATV Forum

[bullet]

I hope someone finds this interesting...

I thought I would share a little technical learning on ATV suspension, or more to the point, when to service a shock.
I’ve just sent my rear shock off to QuadSquad for servicing after noticing a fairly dramatic decline in performance . I have a good understanding of hydraulics, but I was surprised at the rate of change in the shocks operation. After discussion with Adam on what might cause such noticeable change, he explained a few things, I whipped the shock out and sent it back to QuadSquad for servicing. So this is my example of how I noticed it needed servicing.

Firstly, lets consider what work the rear shock does.
If you do Finke at pace, your front end probably takes half or two thirds the impact that the back end does. Most of your weight is over the back wheels when you are hammering whoops, and there is only one shock unit back there doing all the work (compared to the two up the front). Add to that, there is usually a hot exhaust running past the rear shock somewhere, and in any case the front shocks are out in the fresh air and the rear shock gets a lot less cooling tucked in behind the radiator air flow and engine heat. So at a conservative guess the rear shock might be under 4 times the stress of any front shock. It makes sense that this shock is going to need servicing more often than the fronts. But how can you tell when.

When I had my shock dialled in, depending on the type of riding, I normally found that I ran the rear low speed compression about 8 clicks off of ‘H’ (full adjust to Hard). After a few months and maybe the equivalent of 3 race days and a bit of in-between training, I noticed the need to click the low speed in another click (7 clicks off full H). A month or so later maybe another click. The next month the same again. I vary settings a bit to suit the task, but essentially I found that I was chasing particularly the compression adjusters just to maintain the same performance. My riding style was not changing that dramatically, it was the shock.
I got to a point where I was 3 clicks off of H and I started asking Adam questions. The Shock stroke resistance was becoming more and more linear. It was losing its progression. It still felt smooth, but a bit more floaty, and I had lost any decent bottoming resistance. After about a six month service life, I was running 3 clicks off H and the shock seemed weaker still. So I wound all of the Low speed and High speed on full toward ‘H’ for a test ride to see what i had up my sleeve. Answer... Nothing. I could not adjust the shock back to anywhere near it’s original performance even with every adjustment wound all the way in. The best way I can think to describe it, it seemed to lose all of its progressive resistance and only offered maybe half of its normal ability. Cranking up the adjusters made sense to me, but the bit I underestimated was how much the characteristics change. It seemed that any internal space age progressive valving rocket science became almost worthless if the oil is out of service.

I ended up doing the Vic Titles on it like that and had to change my riding a bit to suit. The rear shock could no longer handle the big impacts and blew too easily through to the bump stop.

I thought I would share this just in case anyone else was wondering how good their suspension ‘should’ be. What I’ve learnt is that if your shock oil is passed its service life, you cannot even begin to evaluate the valving performance. In other words, if your rear shock is old or has not been serviced for a long time, and you think you need better suspension... you are probably more than half right. Your riding and suspension requirement would be improving with experience, and your shock is slowly going the other way and getting worse every time you ride. What you need first is a shock service. Keep your shock in good condition, and then with an experienced shock builder, you can work out exactly what you need.

The next question I asked Adam... What if a customer sends you a shock and says it’s too weak, and he has all the screws wound in full. How do you tell if the oil is just worn out, or if the valving is just too weak? Whilst he was explaining an answer longer than the above, which included things like oil colour, viscosity, the way the rider rides etc etc... I could see the short answer was
‘you need to take it to someone who knows what they are doing’.

I can’t wait to get my shock back
_________________
Can-Am X Team
Bullet #Y12. MrsB #Y18.

[yogie]

so you think, mine after about 350+ hours could do with a look at...
_________________
2005 KFX700
With a few bells and whistles
and the twin yoshi's
American Star A-arms, tie rods
elka stickers
Shorty Shifter
I have a Waco
rossco gave me a flexx sticker
honda thumb
Great at climbing trees
durablue stickers

[bullet]

Definitely.
If they are non-serviceable, you might be limited with replacement options.
But if they are servicable, get them done and have a good think about what you might want to change while you are about it.
_________________
Can-Am X Team
Bullet #Y12. MrsB #Y18.

[Big Jb TRX450]

Bullet that was a great read, gave a great insight into the workings of such an important bike component
_________________
04 TRX 450r
with a bit of this & a bit of that

[PeteW]

yogie wrote:

so you think, mine after about 350+ hours could do with a look at...

you've got a KFX yogie, they could have done with a looking at when they were new....
_________________


www.thumbpump.com
www.dirtcomp.com.au

[fossil800R]

PeteW wrote:

yogie wrote: so you think, mine after about 350+ hours could do with a look at... you've got a KFX yogie, they could have done with a looking at when they were new....

chuckle..snort..guffaw
_________________
I'm not suffering from insanity, I'm enjoying it!!!

[yogie]

fossil800R wrote:

PeteW wrote: yogie wrote: so you think, mine after about 350+ hours could do with a look at... you've got a KFX yogie, they could have done with a looking at when they were new.... chuckle..snort..guffaw

shut your pie hole...
_________________
2005 KFX700
With a few bells and whistles
and the twin yoshi's
American Star A-arms, tie rods
elka stickers
Shorty Shifter
I have a Waco
rossco gave me a flexx sticker
honda thumb
Great at climbing trees
durablue stickers

[phil58]

PeteW wrote:

yogie wrote: so you think, mine after about 350+ hours could do with a look at... you've got a KFX yogie, they could have done with a looking at when they were new....

Are you refering to his shock? or his mental state when he bought the kfx??
_________________
Phil.....

[bullet]

To follow up on this topic...

I got my rear shock back from Quadsquad, and just refitted it. I sent the shock to Adam the way I was last using it, with all the adjusters wound hard in. It is good practice to send the shock to your suspension tuner in it's normal condition. That way they get an idea of how you run.
The oil in my shock was aparently quite discoloured and overdue for change, so Adam was confident we did not need to do any valving changes to get me back on track. I was not so confident. I thought the shocks characteristics had changed SO much, that perhaps my needs were different (old age), and that i needed a tougher compression shim stack.
I checked the shock over before installing it and Adam had sent the shock back with all of the adjusters centralised at 12 clicks out. I thought I remembered running the compression at about 8 clicks out and the rebound at about 10 clicks out. So I set them to that and centralised the High speed copmpression adjuster for it's first test ride.
Out the shed and down the driveway over a few bumps, it already felt different. I did half a lap around my test track and was amazed at the difference. the rear end was very dead, and very slow. I pulled in immediately and wound the High speed compression completely off, the low speed out to 12 clicks (where Adam originally had it) and I knocked the rebound out to 14 clicks.
This time I did a few laps of my track, and singled out a few jumps that I knew were a good test case. The rebound was now a bit too fast, so I went back in one click and I was happy with the compression. I left it what I thought was a little bit dead (hard) because I reckon I probably got used to it being too fast over the last few weeks anyway.

End result, of just getting an oil change service done...
My shock now rides a lot more controlled and firmer with Zero high speed on, 12 clicks off with the low speed compression and 13 clicks off with the rebound.
Consider that before servicing, I had everything wound in full hard and it still was not cutting the mustard.
Now i've got heaps of adjustment either way, and each click actually makes a difference.

Thanks QuadSquad, I won't be leaving it so late next time
_________________
Can-Am X Team
Bullet #Y12. MrsB #Y18.

[Quad Squad]

bullet wrote:

Thanks QuadSquad, I won't be leaving it so late next time

I've heard that before haha
_________________
www.quadsquad.com.au
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