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Old 04-22-2006, 10:21 PM   #61
holycaveman
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Your rear shock bumper squashes down a bit, in calculated travel. And its your linkage/swingarm etc that gives you your overall travel, not nessasarily the rod length.

Also a longer rod won't increase bottoming. The problem is the adventure is sprung like the KLR. Just for moderate offroading, in order to keep the nice ride for the street. If you want offroad bottoming resistance you need to revalve it.
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Old 04-23-2006, 09:41 AM   #62
bmwktmbill OP
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Cave,
Not sure what you are saying. I suggest you disassemble the rear suspension on A KTM Adventure, clean and grease it and get out a measuring tape and start measuring with the wheel off. There are three moving parts, the shock rod, the connecting link/pivot and the swing arm. If you lay under the machine and look up you will very well understand how it works, that it is linear on the KTM and that one controls the other so that if the shock compresses 2.5 inches the link/pivot moves the swingarm via the pivot thru an arc of 7 1/4 inches. Brother, these parts are made of steel and that is how it is. You can't change anything unless you change the length of one of the components. All are related to the other.
I sure wish someone else would try this so I could understand why the rear wheel travel is so limited when I actually measure what is going on. It would help me if someone could stick a tape on their rear shock and measure the length of the shock rod to the rubber bumper with the rear wheel off the ground. I don't need exact, just approximate would really help right now. Should be around 2.5 inches?
Thanks,
Bill in Tomahawk, WI
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Old 04-23-2006, 10:44 AM   #63
meat popsicle
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bill,

cave said "revalve", and while I don't claim to understand the mechanics of the supension, many folks who seem to have a good handle on it, and the professional shops who do this for a living, say that revalving is a component of reworking the suspension.

I am guessing that the valve(s) must be like jets in a carb, metering the shock/fork fluid. Change how fast the fluid can move from one portion of the shock/fork to another would alter the way it responds.

Perhaps this is not a linear process either. Sure would be nice to read something on how these items work; I am tired of just floating by on hope...
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Old 04-23-2006, 03:49 PM   #64
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Hell yes the valving is non-linear!!! That is the big problem with changing the links, which are also non-linear - most are quite progressive in order to provide supple motion at near full extension yet firm up through the stroke to resist bottoming. (The KTM/WP PDS system is a notable exception.) Two inter-related curves - futz with just one and you can very easily make things worse. How much of this you notice depends on what characteristics are important to you.

A simple (hopefully) explanation of your shock mechanism, for those unfamiliar with it:

Shock valving is simply a piston with holes (orifices) in it with a series of thin, flexible washes stacked over the holes. This is called the shim stack. By varying the flexibility, number and spacing of the shims, the stack can be extremely fine-tuned to react differently to the varying oil flow requirements.

The piston is fixed to the shock shaft. When the shock moves (compression or rebound) the piston must move through the oil bath contained in the shock body, so the oil must flow through the holes in the piston and push the shims out of the way. The way the shims move in relation to different loads gives you the reponse curve of the shock. There are two sets of holes in the piston and a shim stack either side; one for compression, one for rebound. Cartridge forks have two much smaller pistons, each with one shim stack.

Note also that the rebound/compression adjustment clickers cannot change the shape of the response curve of the shim stack. They are a simple needle valve arrangement for a bypass to the piston. Essentially they only raise or lower the entire curve. Changing the shape of the curve requires changing the shim stack. Typically, the rebound knob is on the bottom of the shock because the bypass is up the middle of the shock shaft; the compression adjuster is on the remote oil reservoir to alter the flow from the shock to the reservoir.

So there will be shims to allow small oil movements for small bumps. There will be shims that will rapidly open a big hole to allow oil to flood through, such as when you hit a big bump and the wheel has to move a long way fast. Plus everything in between...that's where it gets complex and you just hand it over to your suspension fellah and say, it's doing this, and I want it to do that...

An example: my '95 Triumph Trophy runs an Ohlins Daytona shock. If the rebound clicker was set soft for small bumps, it would weave on high-speed corners. Set hard to get rid of the weave, it was harsh on small bumps. My Ohlins man compared the shim stack to the '96-on Trophy, and noted that Ohlins had firmed up the low-speed (weave) damping...so he simply installed that shim stack...voila! Perfect! or pretty damn near it.

I have heaps and heaps of documentation with diagrams etc. Let me know if you want more info, I will dig it out for you. It's also bound to be online somewhere.

[Edit]
Yeah, try here: http://www.ohlins.com/mc_when_you_are_riding.shtml
Woulda saved me a lotta typing!

And see this: http://www.off-road.com/dirtbike/mar...b101shock.html
More pcitures and explanations.

Enjoy!
[/Edit]
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warewolf screwed with this post 04-23-2006 at 04:14 PM Reason: Add link to Ohlins, and again for another
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Old 04-23-2006, 04:00 PM   #65
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Pds

Here is some description of the PDS system, which is NOT fitted to the LC4s.

http://www.motorsports-network.com/ktm/Ktm.htm

Quote:
Originally Posted by KTM
The heart of the PDS system is the new WP 'Smart Shock', the first shock with a brain. The new smart shock is both speed and position sensitive, thus eliminating the need for heavy, complex linkage designed to provide a rising-rate function.

Quote:
Originally Posted by KTM
PDS, or Progressive Damping System is what all future suspension configurations will aspire to, and KTM has it today, exclusively.

Working directly with the suspension engineers at WP, KTM developed the 1998 WP 'Smart Shock', the first shock with a brain. Essentially, the WP 'Smart Shock' is both speed and position sensitive, eliminating the need for complex linkage elaborately engineered to accomplish the same task. The WP shock dual-piston and proprietary needle valve design produces a completely progressive rising rate with virtually limitless adjustability.
Thus I would be extremely surprised if the linkage on the Adventure was linear! In the old twin-shock days, simply laying the shocks over at an angle provided a progressive, rising-rate action.
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
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Old 04-23-2006, 10:12 PM   #66
bmwktmbill OP
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Gents,
Check out these measurements. The large number is the distance between the shock eyes, The small number is the inches the swing arm actually moves on the Adventure bike when the distance changes(shock compresses).
0=16.0
1=15 3/4 inches
2=15 1/2
3=15 1/4
4=15 1/8 All numbers are inches, both columns.
5=14 1/2+
6=14 1/4
7=13 7/8
8=13 3/8
9=13.0
These are actual measurements taken off my bike. As you can see if the shock only has 2.5 inches of travel we only have between 7 and 8 inches of rear wheel travel total. As for the nature of valving on WP forks and shocks on the Adventure suspension my valving is on the bench and yes there is a blow off washer over the spring stack but it is very weak and I think acts as a one way valve. I believe the flow of oil is controlled by the number of shims in the stack and nothing else.
As for damping having anything to do with bottoming, it will only change how rapidly it occurs. You can vary the damping at the forks for more or less with a change in oil weight or oil height or by revalving(shims in the stack). At the rear shock only the oil weight or valving(shims in the stack) can be changed.
For bottoming problems you need to change the spring weight either front or rear. You can also vary the external adjustments provided by WP, in the case of bottoming the compression setting can be increased but after you have maxed that out internal work is needed and again these adjustments control the speed at which things happen.
Linear means of or pertaining to a line. I am maintaining that WP suspension is linear in movement, spring wind(straight wound springs) and damping. The only progressive variable I can imagine is the air chamber in the front forks. With this, the more it is compressed the harder it is to compress. I don't know enough physics to know if that is linear or not but some smart guy does. I am just trying to figure things out the mechanics.
Would someone measure the length of the shock rod fully extended on their Adventure bike for me? Please. My shock is away being worked on and I need the approximate measurement which should be around 2.5 inches. Just stick a tape in and guess. Accuracy is not important.
Thanks.
Bill in Tomahawk
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Old 04-23-2006, 10:42 PM   #67
warewolf
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Boyles Law

Quote:
Originally Posted by bmwktmbill
The only progressive variable I can imagine is the air chamber in the front forks. With this, the more it is compressed the harder it is to compress. I don't know enough physics to know if that is linear or not but some smart guy does.
Non-linear.

http://www.grc.nasa.gov/WWW/K-12/airplane/aboyle.html
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KTM LC4 640 Question? Check here first --> KTM LC4 (640) Index Thread
Quote:
Originally Posted by Steve McQueen
All racers I know aren't in it for the money. They race because it's something inside of them... They're not courting death. They're courting being alive.
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Old 04-23-2006, 10:43 PM   #68
meat popsicle
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Old 04-24-2006, 07:59 AM   #69
Arch
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Quote:
Originally Posted by bmwktmbill
...Would someone measure the length of the shock rod fully extended on their Adventure bike for me? Please. My shock is away being worked on and I need the approximate measurement which should be around 2.5 inches. Just stick a tape in and guess. Accuracy is not important.
Good thing, because it's hard to get anything in there to measure accurately. It is however at least 3.5" to the base of the bumper.

I dunno why we're still talking about this. Your suspension's travel is measured from full extension to full compression, not some arbitrary point somewhere in between. At full (or at least close to it) extension, a stock LC4 Adv will have about 11" from full knobs to inner fender. With just 1.25" lowering links and full knobbies, this happens...



That's with proper sag settings and an average sized guy running your average desert exploring pace. No wacky jumps, no 80 mph blasts over terrain that can kill, or any other ricky racer games.

Take the same bike, re-install the stock suspension links and the problem goes away and the bike is able to use its available travel. So, to lower yours (even more), something's going to have to give. Your suspension's travel will have to be limited, damping adjusted to suit, etc. But of course, we already know all of that.

Again, there's nothing wrong with limiting your machine's capabilities to suit your needs. If wanting to lower for casual use and commuting, of course a good suspension guy's tweaks will do the trick. But you started this thread saying that you wanted to lower your LC4 "2-3 inches", like to carry 100 lbs worth of junk, and ride down "bad gravel roads" at 60. Let me assure you that someday, if that accurately describes the bike's mission, you'll come into a dip at said speed, on said road, with said setup, and its even odds that bad things will happen.
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Old 04-25-2006, 02:09 PM   #70
bmwktmbill OP
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Hi Arch, Warewolf,
Thanks for the pics and all the words. Just got off the phone with Brad Lowe and we talked about just the problem you described and thought about shortening the spring on the rear shock to stiffen it and reduce preload on the shortened shock. Lowe recommended against doing this mostly because we are in uncharted territory with this and can always go back and cut the spring later. The Germans(Sommer) maintain thatt the stock spring will be heavy enough with the stock links for a 160 lb rider and 100 lb. gear. I will have more preload with the shortend travel in the stock shock. We are using a 1/2 inch spacer internally to shorten the shock overall length 1/2 inch which will raise the swingarm 2 ", lowering the bike 2' at the rear. Basicially the spring will have to be compressed 1/2 inch to go on the shortened unit.
Up front it is the same drill with the damper rods. I cut the spring 2" shorter yesterday by hanging it over a bucket of water. and filed the top flat after bending the top coil parallel with the other coils. They came out good. Brad is going to look at the compression damping valves and plush them up for me if they need it. I have been running the machine on the gravel with most of the compression damping turned off to get a softer(non jarring) ride on the smaller stutter bumps so typical of bad gravel. Like you said this will not be a PD racer when it is done but it should be just fine for the intended purpose. There is a big difference between a Formula one racer and a PD racer. I am hoping to come out with the best of both.
BTW for Warewolf I wrote incorrectlynin an earlier post on the rebound and compression damping on WP. It is progressive and comtrollrd internally as you stated more or less by a compressible spring/shim arrangement. I would take mine apart but I ended up shipping all the valves to Brad for changes. I am getting anxious to ride this year and we are both guessing about changes. I trust his guessing since I have no frame of reference at all.
Thanks for the measurements on the shock and your help.
Bill in Tomahawk, WI.
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Old 05-06-2006, 06:33 PM   #71
orangeparts
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Question Lowering Options For '06 640 Adventure

I am seriously considering an '06 640 Adventure. The problem is I'm only 5'7". I know Kouba makes a lowering link that will lower the seat height about 1.75". Is there anything else that can be done to bring the seat height a little lower? Thanks.
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Old 05-06-2006, 07:38 PM   #72
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Quote:
Originally Posted by orangeparts
I am seriously considering an '06 640 Adventure. The problem is I'm only 5'7". I know Kouba makes a lowering link that will lower the seat height about 1.75". Is there anything else that can be done to bring the seat height a little lower? Thanks.
I can lower the seat about 1.5 inches. I can go more... but the comfort level drops off rapidly after that, as there isn't much room for foam left. See the Renazco Racing link in my sig line.

C
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Old 05-06-2006, 08:35 PM   #73
Groundhog
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Orangeparts-
I am just a tad taller than you. I put Kouba links on my '06 and raised my forks about 1" in the trees. My problem was not with riding, but with getting on. With the links I can get my knee on the seat and have to work & wiggle to get my foot over. After I am on I can tiptoe both feet, so all is good now. I have about 1K miles on it & and am pretty happy with the lowered suspension. Need to do some more adjustment tweeking, but the trade off from stock to lower for my short legs is worthwhile to me.

I still want to get a seat from Creeper as the stocker must me made of Alpine granite. I might get it 1/2" or so lower.
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Old 05-06-2006, 08:47 PM   #74
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Quote:
Originally Posted by Groundhog
I still want to get a seat from Creeper as the stocker must me made of Alpine granite. I might get it 1/2" or so lower.
Alpine granite? Is that like... harder than regular granite?

I just did a seat for a fella’ with a short inseam on an '06... a bit kinder and gentler foam, a flatter seating surface with most of the slope and crown removed. Not a huge reduction... about 3/4", but should work well for his needs.

To both you guys... a sidestand makes a huge difference when you’re trying to get off or on the bike. The most popular by far is the SW Motech unit imported by Twisted Throttle... bolts right on with the stock centerstand for about $110.

C
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Old 05-06-2006, 09:05 PM   #75
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Quote:
Originally Posted by orangeparts
I am seriously considering an '06 640 Adventure. The problem is I'm only 5'7". I know Kouba makes a lowering link that will lower the seat height about 1.75". Is there anything else that can be done to bring the seat height a little lower? Thanks.

First off welcome to ADVrider and congrats on the bike. I'm about the same height as you and just put on a new Renazco seat (thanks Creeper) and tried the lowering links/sliding the forks up at the same time. I experienced some rubbing of the inner fender with the links so I removed them. It depends on how aggressive you ride your bike and whether or not you want to lose that bit of travel. I've just gotten used to the height of the bike and just plan accordingly when coming to a stop. Shift a cheek and look for a high spot to put a food down. I have a set of Kouba links that you can try if you're interested.

Here's a recent thread discussing the pros and cons of lowering your bike. Lots of good info here.

Errin
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