who's a master of suspens(ion)e ?

[craigie]

apart from Mr Hitchcock....

I've not much to adjust but I have preload and rebound on the back which kicks me right out my seat when I hit a bump, even kicks my girl & me up together when she's on the back.

my question is this; do I decrease or increase the rebound? logic and my basic understanding of English (I'm a jock don't ya know) suggests that I decrease but I've heard suspension can be a bit of a black art.

any tips most welcome

cheers


Craig

[A Yerbury]

you essentialy want a firmer ride. so you will want to wind down the spring adjuster and the lock with a c spanner or shock wrench then, play about with the screw at the bottom. 8 clicks back from fully wound clockwise is standard so try 4 then 8 then 12 etc etc

[crust]

if its kicking you out of the seat then there's a couple of things to check.

What you have to find out is - is it rebounding too quick or is the shock not moving , too much rebound.

Try bouncing up and down on the bike at a stand still.

If the back end goes down but dosent come back up very quickly then you have too much rebound, so wind the adjuster back.

If it springs back quickly then add more rebound dampimg. If this dosent make any difference then the shock has a leak and lost its gas/oil.

:) Crust

[Chris]

As Crust says, it's probably the Rebound damping you want to play with. Wind the adjuster all the way in, counting the turns/clicks and make a note of this so that you always have a reference to come back to, then adjust away.

The pre-load is what it says, it pre loads the spring, and once you are sat on the bike (particularly 2 up) you'll be compressing the spring yourself so it won't have any effect on the ride (unless it is a heavily progressive spring, which it isn't). It will however affect the rear ride height and hence handling, so if you ride 2 up regularly, add a bit to compensate for the extra compression of the rear spring.

If you want to get it professionally, have a word with Dave Wood, he's done loads of monsters now.

[craigie]

Ta lads

I'll invest in a C-spanner, more height sounds good, and then get fiddling on the rebound.

notes, notes, I must rember not use my memory.

cheers


Craig

[crust]

for a little background information try this -

http://www.ohlins.com/pdf/07255-01.pdf

the two rings on the shockbody adjust the amount of preload on the spring and affect the ride height as a by-product but only because the spring is not compressing so no suspension.If you carry your girlfriend a lot then this might be a good idea as the extra weight will cause the spring to compress but it will make the rear suspension harsh for you riding solo.

On your bike the rear shock is compressed by the swinging arm and by a rod linked by a rocker. To adjust the ride height, you adjust the length of the rod by screwing the rod ends in and out. This will raise the rear of the bike and make it turn quicker, adjust it too far and the bike will become unstable.

:) Crust

[craigie]

hey Crust

I had a look and I can't see how to screw the rod ends in and out, I am pretty stupid so if you can make it simpler I'd appreciate it. apologies for my mechanical ignorance, ta for the ohlins thing as well.

cheers


Craig

[crust]

no problem, we all had to start somewhere.

At the bottom end of the shock it attaches to the swinging arm. The other end of the shock attaches to a rocker link.

The other end of the rocker attaches to a rod that attaches to the swinging arm.

Its this rod that contains the rod ends - at either end. These are screwed into the rod and locked with a locknut.

IMPORTANT - One of these rod-ends has a left hand thread - it undoes the other way.

What you have to do is loosen off the locknuts (one undoes normaly ,the other undoes the other way) then put a spanner on the flat in the rod and turn it. One way will make the rod-ends undo and extend the length of the rod. The other way will shorten the rod.

You want to lengthen the rod to raise the ride height and speed up the steering. The trick here is to make small adjustments and try it.

Apparently its a bit of a pig to get the spanner in to do the adjustments so try it a few different ways.

Hope this helps, if not keep posting, we'll get there in the end ;)

:) Crust

[Gizmo]

Adjusting the ride height alters the geometry of the bike, thats not really the rear suspension action, bike will turn in quicker as you've increased the head angle and altered weight bias. Best article I found was one from an RC51 site (http://www.motophotos.com/rc51online/Mods/Sus%20Settings.doc) , its a word doc file and will download if you click the link.

I'll quickly summarise it but its better to read the whole thing. As has been said starting point should be pre load and rebound, the first thing is to make sure you've got preload and sag correct, too little pre load and you'll bottom shock out on big bumps, too much and rear will be too stiff, shock springs suit a range of rider/pillion weights, if you are at ends of range you may need a different spring.


To start measure between a fixed point on swingarm( say rear axle bolt) and rear sub frame, lift rear as high as possible and so that suspension is totally unweighted (you'll need a helper) take a measurement , then with rider sat on bike take another measurement, this should be about 30mm less (25% of Monsters 120mm travel) if its greater increase preload, if it less reduce preload. if you end up with no preload on or over 3 turns on then its new spring time. record how much preload you have then repeat with rider and pillion and once again aim for 30mm, record that setting so you can easily swap over when carryng a pillion.

Once set you an look at rebound, too much and shock will pack down, what happens is that the shock hasn't returned from one hit before it takes another, over a sequence of bumps you end up with a stiff rigid feeling shock as it tries to return then gets forced back by another hit, eventually you end up using all the shock travel so its fully rigid. Too little rebound and bike fires back on first hit. As has been said, try it at rest, bike should rebound smoothly and not slowly or fire back, thats a nice midway point, you can then begin to alter by half turns and see what impact it has. Pick a road you know and are happy riding and spend a bit of time trying different settings, don't alter a lot in one go.

Same principle applies to forks, remember if you alter rear ride height it alters weight distribution putting more weight over front as you increase rear ride height so you'll need to check settings as you change rear

if in doubt, take the bike to a good suspension company, a friend of mine always uses Baines Racing and recently had his S4 setup by them, ask them what they are doing, most will be happy to explain it and show you whats going on.

[craigie]

thanks all,

I will hopefully have some time, and maybe some dry weather, this weekend to try a few things out.

cheers again


Craig

[Will]

Just a small comment the original 620i.e. did not have a ride height adjuster (adjustable length suspension connecting rod) - the 620S i.e. did. I am not so sure about the later 620i.e. but I suspect that it doesn't have one either.

My 2002 620ie stock suspension settings used to give me quite a kick in the pants when going over bumps - it was as if the 'compression damping' was too high, that is it the spring was not compressing fast enough when a bump was hit so all the force was transmitted to the rider. Unfortunately the 620 does not a 'compression damping' adjustment only 'rebound damping'. I have found that reducing the rebound damping by about 3 clicks has helped the real wheel track bump roads slightly better.

Will

[craigie]

cheers Will

I've been looking and looking and thinking I must be blind, it must be here somewhere, so I'm pretty relieved you said that, of course someone will now say that 02 620's do have it and I'll be a fool again...

reducing is what I was going to try so I'm glad I had the right idea.

cheers again


Craig

[crust]

ah, in that case next time you're at a meet check out the length of rods on other bikes as people might have one for sale.

:) Crust

[Will]

cheers Will

I've been looking and looking and thinking I must be blind, it must be here somewhere, so I'm pretty relieved you said that, of course someone will now say that 02 620's do have it and I'll be a fool again...

reducing is what I was going to try so I'm glad I had the right idea.

cheers again


Craig

Just another little thought - it is possible that when you are carrying a passenger that the suspension is 'bottoming out', i.e. running out of travel due to the extra weight of the passenger. This is pretty obvious though as the bike would feel very low at the back and there would be a loud 'clunk' as the shock absorber reached the limit of its travel' and would transmit the energy of the bump through to the rider and passenger.

I am 12 stone and my 10yd old son is about 4.5 stone - when we are both on the bike I have to increase the preload to about 80% of max to ensure that I keep enough ground clearance and avoid ' bottoming out' over large bumps.

Will