Suspension setup

[Rico]

Thanks all for the help. What is spring rate though?

I checked the settings last night, the preload was at the factory setting, but the damping was harder than it should have been. So they were not matched. I reset the damping, and had one of the best riders ever afterwards, along some main roads with narrow lanes and tight corners. I felt so much better around the corners, it felt more stable and my confidence went up so I could take them faster. Perhaps it is a placebo effect, but whatever it is, it's brilliant. After a while the bumps appeared and still felt very hard to me, so I might at some point make it softer, although I'm not sure how to match the preload and damping then, as there are no specific "levels" for the damping.

I did have a couple of 600cc sports tourers (Suzuki GSX600f and Kawazaki ZZR600) before my G650, and I'm sure I remember those being a fair bit nicer over the bumps.

None-the-less, I can't wait to head to one of my favorite windy roads in the Brecon Beacons on the weekend. Might head to the Forest of Dean afterwards too... what with all this riding, I never have a chance to clean the dirt gathering on the bike, this is surely a good sign!

[Corvus]

Rico said: "Thanks all for the help. What is spring rate though? "


No doubt there'll be a full explanation on tinternet, but in essence the rate is pretty much built into the spring, BMW's elastogran being the only attempt at productionised on board adjustable spring rate I've heard of myself. It is a measure of how much a spring will compress for a given applied load eg; kg per mm etc.

A single rate spring will compress the same number of mm for each extra kg force or load applied. Then there are dual (or multiple) rate springs where the coils wound most tightly compress first untill coil bound, then the next section of coils, less tightly wound, kick in. Then there's progressive rate springs....

Except for the bmw elastogran bikes, a change of spring rate means a change of spring.

Oh, of course there are gas springs, of which I know less about!

[conkerman]

OK, Here goes.

The spring holds the bike up and 'suspends' the bike. The damper stops the spring bouncing.

For motorcycles in my experience.

Step 1. Set everything back to standard. If not still happy.

One of the most important settings on motorcycle suspension is the sag setting. Sag is set adjusted using preload, and is a function of the stiffness of the spring.

With the rider on the bike, the wheels should be between 25-35% of their way through the suspension travel.

You need to measure the distance between a fixed point on the wheel/swingarm and a fixed point on the bike with

1, The wheel off the ground with the suspension unloaded. A
2, With the rider on board. B

Sag = A-B

There is some adjustment available by the preload adjuster, but if you can't set sag by being a flyweight or a porker then a change of spring is required.

Once this is done, you can then set the damping to your taste.

I hope this helps.

[Corvus]

OK, Here goes.

The spring holds the bike up and 'suspends' the bike. The damper stops the spring bouncing.

For motorcycles in my experience.

Step 1. Set everything back to standard. If not still happy.

One of the most important settings on motorcycle suspension is the sag setting. Sag is set adjusted using preload, and is a function of the stiffness of the spring.

With the rider on the bike, the wheels should be between 25-35% of their way through the suspension travel.

You need to measure the distance between a fixed point on the wheel/swingarm and a fixed point on the bike with

1, The wheel off the ground with the suspension unloaded. A
2, With the rider on board. B

Sag = A-B

There is some adjustment available by the preload adjuster, but if you can't set sag by being a flyweight or a porker then a change of spring is required.

Once this is done, you can then set the damping to your taste.

I hope this helps.

Does altering the preload alter the available suspension travel? Does it change the "set length" of the spring? Not sure if that's the right term.

Cheers

[conkerman]

I think of it as fine ride height adjustment.

Been quite a while since I messed with suspension, but the correct spring rate, Sag adjustment allows the suspension to work correctly.

Your questions got me googling.

Have a look at this



http://racetech.com/articles/SuspensionAndSprings.htm

[Corvus]

I think of it as fine ride height adjustment.

Been quite a while since I messed with suspension, but the correct spring rate, Sag adjustment allows the suspension to work correctly.

Your questions got me googling.

Have a look at this



http://racetech.com/articles/SuspensionAndSprings.htm

Thanks.

I'll see if I can digest it! Ha.

[Corvus]

I think of it as fine ride height adjustment.

Been quite a while since I messed with suspension, but the correct spring rate, Sag adjustment allows the suspension to work correctly.

Your questions got me googling.

Have a look at this



http://racetech.com/articles/SuspensionAndSprings.htm

Right. I think I get it. The sag is measured taking into account the shock fully extended to stop ie; topped out. So increasing the preload will in actual fact shorten what I've been calling the "set length" (dunno if that is a good term or not). Preload!

Where I think confusion comes in is that we commonly say that would stiffen the spring. This kind of gives the impression that we increase the spring rate, which we don't. Although on a progressive spring we do, yes? On a dual rate spring we will reduce the amount of travel before the lower rate coils go coil bound, yes?

But surely we don't change what I can only think to call the balanced static force in the spring once we sit on the bike. It will always obviously balance our weight and whatever proportion of the bike's static weight.

What is the correct term for this force or state?

The ride height is also affected and maybe geometry, depending on how we adjust each end, front and rear, relative to each other. But, because we set off down the road with the bike and ourself weighing just the same, what actually changes apart from ride height and the proportion of travel available each side of the static position?

[conkerman]

Off for wedding anniversary dinner with Mrs C

But have a look at this

http://fixbroke.tumblr.com/post/39188918110/spring-preload-and-sag-what-does-it-really-do

Sensible preload will not effect spring rate.

TTFN

[Corvus]

Off for wedding anniversary dinner with Mrs C

But have a look at this

http://fixbroke.tumblr.com/post/39188918110/spring-preload-and-sag-what-does-it-really-do

Sensible preload will not effect spring rate.

TTFN

Thanks again. A clear guide. I've also pulled my "sportbike performance handbook" by Kevin Cameron off the shelf. Pages 125 and 126 do the trick. Can recommend this book. I usually use this to help clarify motorcycle matters as a first port of call.

[Corvus]

So, am I oversimplifying things by saying that by adjusting the preload all you are doing is changing the ride height and the proportion of suspension travel available above and below the balanced static load? The portion of travel above is called "sag" and the portion below, to full compression, is called "available travel".

All other spring characteristics are dictated by the spring rate. Contributions by the damping system excepted.

If so, then it's difficult (for me) to imagine how a rider substantially above or below the design static load of around 80kg will have the bike perform dynamically as intended by the designers without a change of spring rate?

So why did the bmw elastogran never catch on? In fact why has it apparently been dropped? Are the contributions by the damping system so influential as to make changes in spring rate unnecessary?

[conkerman]

I don't think you are oversimplifying it. That's what you do when you set sag.

Yes, spring rate will be constant through the adjustment.

It doesn't, not without a change of spring. Getting a bike sprung to your weight makes a HUGE difference.

No Idea, don't even know what it is...

[Corvus]

I don't think you are oversimplifying it. That's what you do when you set sag.

Yes, spring rate will be constant through the adjustment.

It doesn't, not without a change of spring. Getting a bike sprung to your weight makes a HUGE difference.

No Idea, don't even know what it is...

http://rideapart.com/2008/10/details-bm ... uspension/

The principle of it, as I see it, is on board adjustable spring rate.

[Corvus]

I don't think you are oversimplifying it. That's what you do when you set sag.

Yes, spring rate will be constant through the adjustment.

It doesn't, not without a change of spring. Getting a bike sprung to your weight makes a HUGE difference.

No Idea, don't even know what it is...

And, if we're not 80kg, what are the chances of the ideal ride height coinciding with the sag position?

[conkerman]

Depends on how heavy you are.

You may be able to preload it up if closeish to 80Kg.

This is the ideal situation, my bikes have been good to ride even when not 'ideal', although sorted suspension really, really makes a difference.

I had a Firestorm about 10Yrs ago that was totally transformed by some suspension work, the standard forks were epically bad. My mate who currently has an S1000RR still rates the post sorted firestorm as one of the best, most usable bikes he has ridden.

[Corvus]

Depends on how heavy you are.

You may be able to preload it up if closeish to 80Kg.

This is the ideal situation, my bikes have been good to ride even when not 'ideal', although sorted suspension really, really makes a difference.

I had a Firestorm about 10Yrs ago that was totally transformed by some suspension work, the standard forks were epically bad. My mate who currently has an S1000RR still rates the post sorted firestorm as one of the best, most usable bikes he has ridden.

I happen to weigh 80kg and have done most of my biking life, so I'm lucky that, assuming the bike is well designed in the first place, standard settings work fine.

What did you make of the elastogran link?

The point I was putting forward was that, if we are a fair way higher or lower than 80kg and we adjust preload, we are changing sag and ride height at the same time. But is there any guarantee that if we focus on, say, an ideal sag measurement will we automatically end up with the "design ride height"?

I understand it is possible to buy shocks with adjustable ride height facility independent of preload. Basically you are adjusting the overall centre distance between the shock mounting eyes without (necessarily) changing the preset spring force, with the shock in the unloaded state. That's a subtle difference between adjusting preload, where the overall length between eyes stays the same but the preset spring force changes, with the shock unloaded.

Interesting stuff!