Set up for the long one.

**Bass** · 11th July 2010, 23:30

Originally Posted by Phreaky Phil

I think you have to look at the springs and damping together.
:

Eventually, of course you do and I guess that everybody learns in their own way.
My way is to try and understand the influence of each component separately before trying to figure out their combined effect.
If you want to discuss damping, I am happy to, eager even. However as you have pointed out, it can be difficult getting across our exact meaning when conversing like this.

**Bass** · 11th July 2010, 23:45

Originally Posted by That looks like fun

Ok, you win I will show that I can be serryus.

Forget sag, rebound, static and all that stuff.

Lets look at "Sprung" vs "Unsprung" weight.

Any weight not supported by the springs, eg wheels, tyres, etc can be taken straight out of the equation as we have little control over that (unless you mount your load to the axles somehow, but why?

) Everything else is "Sprung weight" Regardless of if the weight is carried high, low, forward, back or by those poor buggers plowing the field. If it is supported by the springs it becomes part of the sprung weight.

AND THE SPRINGS HAVE TO BE STRONG ENOUGH TO SUPPORT SAID SPRUNG WEIGHT while maintaining the ride height characteristics of the vehicle. This is so the suspension has the correct amount of travel to go up and down goodo

So now that we have the load carried and supported properly shall we look at the real problem.............
Yes the vehicles damping devices (thats shock absorbers to ewes), righto, away ya go sort them out

I don't understand your need to ridicule, especially as in this case I think that you are pretty much correct. What you are effectively saying is that there is no such thing as static loading - it's all dynamic and that any change to the weight carried by the suspension IDEALLY requires a change in the spring rate.
I agree with you
It's just a bitch that it's impractical to be changing springs every 5 minutes.

If you want to talk damping, fine.

You start. How's your differential calculus?

**Bass** · 12th July 2010, 00:12

Originally Posted by warewolf

Okay, there's a bit of misquoting/misinterpreting throughout this thread

I'll try to be clearer.

No, I'm obviously the one who needs to be clearer as so far I have made a piss poor job of explaining myself.

I was trying to point out the logical consequences of considering the luggage as part of the static load. The main one is that the spring rate then becomes dependant on the rider weight only. This is obviously nonsense and so the luggage cannot be part of the static load..
I apologise for not spelling that out.

I agree with the rest of your analysis except that I would set the static sag first, but that's a personal thing. I guess that in effect you are saying that the spring rate depends on the difference between static and rider sag. I agree completely.
I now think that the static sag MUST be set without the luggage however which is what I was asking at the outset.

Despite appearances to the contrary, this thread has been of significant assistance to me as I now have the means to pack a bag for the next OZ trip (whenever that may be), chuck it on the bike, take a few measurements and order exactly the spring(s) that I would need. I need to know the existing spring rate of course, but I can measure that.

So far as the Trumpy goes, I was trying to illustrate that while most of the respondents here were differentiating between rider(s) and luggage, so far as a pillion was concerned that there was no difference in their effect. I could either put my 65kg wife on the pillion seat or I could put 65 kg in the panniers - the effect on the ride would be the same for both - again trying to push the point that the luggage is not a static load.
I have actually been trying to keep rising rate linkages out of this discussion because of the added complication and because it's not actually necessary to consider them provided we are always making comparasons at the same points of the suspension travel.

**That looks like fun** · 12th July 2010, 06:20

Originally Posted by Bass

I don't understand your need to ridicule, especially as in this case I think that you are pretty much correct. What you are effectively saying is that there is no such thing as static loading - it's all dynamic and that any change to the weight carried by the suspension IDEALLY requires a change in the spring rate.
I agree with you
It's just a bitch that it's impractical to be changing springs every 5 minutes.

If you want to talk damping, fine.

You start. How's your differential calculus?

Its not an overwhelming need to ridicule

In fact some see it as humour. However in a two dimensional world such as print the writers intent is open to interpretation by the reader

As a mechanic (in a life before I found trucks) I met many people who with best intent over complicated things for little gain. IT repair people are classics at this, just ask them to build you a simple program based on excel and see what you get

Colin actually gave the best answer I have seen so far when he explained how to know if you have the correct "springs" for the load being carried. Static, Dynamic, don't matter. If the spring is required to carry that weight then it needs to be designed and set for it. Once that is done your ride characteristic's are controlled by the shock absorber and the vehicles design limitations.
Changing where the load is carried (on rider or on bike) will have an effect on required shock absorber action

Differential calculus,

I think thats the piece on the back of the truck that distributes the torque of the engine equally at right angles to the prop shaft what makes the wheels go round and round

**Bass** · 12th July 2010, 08:49

Originally Posted by That looks like fun

Its not an overwhelming need to ridicule

In fact some see it as humour. However in a two dimensional world such as print the writers intent is open to interpretation by the reader

There is an old saying although no-one seems to know who first said it......................"Sarcasm is the lowest form of wit"

Originally Posted by That looks like fun

Differential calculus,

I think thats the piece on the back of the truck that distributes the torque of the engine equally at right angles to the prop shaft what makes the wheels go round and round

Let's get this straight. I was annoyed/surprised at the tone of your posts, especially because in the finish, you had some really valuable input into the discussion.
I hear where you are coming from and I completely agree with the kiss principle. I think your approach is great for making the best of what you have. However, I want/need to go further than that and to do so I have to be able to understand what is going on at a fundamental level, especially if in due course I am able to specify my own equipment.
Let me gve you some background and perhaps you will see where I am coming from.
Two years ago, a friend and I prepared a couple of DR's and spent 2 months doing back-block Australia. Part of the preparation process was spending significant sums of money with Robert Taylor. What we received for our money initially appeared to work really well and we were pretty happy. However, once we got to Oz we were less so. Firstly, it quickly became apparent that the forks on the two bikes were set up differently and we couldn't understand why, since they were done at the same time and we are almost identical in weight. We have never resolved that.
Eventually we got the back ends pretty well optimised and remember that we had buckets of time to experiment.
It was corrugations that were the problem and initially we got our arses hammered. After a while we got things to the point where we could tackle small to medium corrugations at speed. However, if we suddenly ran into deeper corrugations (which was so common as to be normal) we got hammered so badly that it felt like our eyeballs were coming loose and we like literally could not see.
Now I have to be fair here and say that we covered 18,000 km in 2 months and we had NO breakages. In fact the DR's were models of reliability and so Robert must have got something right. Back in NZ I have put the standard spring back on the rear shock, but have left the stiffer springs in the forks beause the DR is notorious for being soft in the front and we have left the big tanks on. I have to say that it think it goes pretty well for an old DR, but the compression damping on the rear is still too high and it's set for minimum. It probably needs a thinner bottom/main shim.
However, I have always wondered if it was possible to get them to perform better than they did and I am determined to get myself to a position where I am capable of doing that evaluation myself. I am not just talking a "shit, this goes well" qualitative evaluation either. I want the numbers.
If at the end I am forced to the conclusion of "that's as good as it gets for a DR" then so be it.
If however I can find a way to put the load that we were carrying back on and get the beast to do it right, I will go and have a word with Robert. I have no intention of kicking his arse, I am just happy to spread the information around. I also want to be at an appropriate level technically so that I can have that discussion without making a dick of myself. That's where the differential calculus comes in and many years ago I could have written the equations that describe the movements in question. It WAS many years ago sadly.

**warewolf** · 12th July 2010, 10:02

This is all good!

I don't think it really matters whether you set the static or rider sag first. I've read set-up guides from various suspension experts and they aren't consistent, although rather more do say start with static. That's possibly because it can be done solo. The order you set them doesn't change the result in the other.

Pillions, hmmm well I think they should contribute to the static load, but not 100% since they too have legs. My wife moves with me, and I can telegraph my intentions. If I start to take my weight on my legs, she does too.

**That looks like fun** · 12th July 2010, 17:02

My point was, is, was and shall remain that the ride of the bike is controlled by the action of the shock absorbers. The springs (at their basest level) merely support the sprung weight of the bike (or any vehicle for that matter) in a position that allows the shock absorbers to perform to their optimum. Get the right springs for the weight, set the shocks for the terrain to be covered plus matched to "your" riding style and presto, perfection. Change any of those things and Viola it all turns to custard.
Remembering that we do not ride on a race track (where the conditions alter very little from lap to lap) so much of what we do is compromise.

Sand, corrugations, compacted gravel, freshly graded gravel, and thats all in the first ten meters of leaving home

However its good to experiment and trial new theory's and ideas, after all thats where progress is born. The KISS system reminds us that sometimes you just got to realize that you cant make a silk purse from a sows ear.

As for Sarcasm, it may be the lowest form of wit but they make good coffee

**Phreaky Phil** · 12th July 2010, 19:26

The reason I asked what shock you were using was, I used to have a DR650

. I spent considerable time and effort on the suspension. It was set up with Ohlins rear. 0.43 front springs with Race Tech Emulators. I even experimented with different triple clamps as I never really like the way it steered on gravel. When I refitted the stock shock to sell the bike I couldnt believe how bad it was.
The best suspension on a bike ive owned was my WR400 with Ohlins rear and somebody's fork kit. The Ohlins rear made a HUGE difference, even 2 up on gravel, it soaked up everything. Plush like a plush thing !! I dont know why it was so good. Maybe the valving was spot on. Maybe the leverage ratio's were better than others.
I think the corrugations are probably one of the hardest things to set up for. Its a lot to ask of the suspension, to pound up and down about 10 times a second, and in Australia to do it for hours at a time !!
As I mentioned earlier my Beemer shock is packing down over corrugations. You can feel the rear end sit down and stiffen up and you loose forward drive or it steps out sideways.
A revalve is the only way to cure it and may take several goes to get it right

**That looks like fun** · 12th July 2010, 20:46

Beemer shocks (standard ones) are notorious for not handling repeated work, eg corrugations. It is a lot to ask of a mechanical device that is supposed to stop (at a controlled rate) the actions of a fully laden scooter when all of the forces that Sir Isaac could think of are trying to throw it into orbit at the top of the bump then send it to china at the bottom, then allow the suspension to return to its correct position ready for its next beating.
Lets not forget the other factors involved, say... rider style for instance. Once you have the bike set to the optimum compromise for the surface you are expecting to ride on, the easiest adjustment you can make on the road is to the rider.

As an example, I was carrying out an assessment of a job applicant part of which involved a practical driving assessment. On a particular corner I know well he tucked the front of the unit off into the water table and went round the corner goodo

I knew why he had done it but asked anyway. Sure enough his reply was that as the corner had a slight off camber and double apex, by using the camber of the water table to essentially hold the truck to the left he avoided the weight of the truck carrying it over the centre line on the exit to the corner.

I asked him if he knew of another way to solve the same problem, after a blank look and a long silence I gave him a clue, go into the corner a bit slower

He laughed and said fair call

Got the job