Virago 250. Softening suspension?

[bungbung]

Sorry but mostly bollix
The preload usually cannot compress the spring because the other end is attached to the swingarm which is free to move. You crank one end in - the other moves out.

Look at the picture, if you increase the preload, the spring is shortened.

[jrandom]

blah blah blah

Seriously, man, what the fuck are you on about? I think that was the least meaningful post on how suspension works that I've read on KB.

Preload is when you have an adjustable collar around the top of a shock absorber's spring that can be wound down to pre-compress it.

It's there to adjust how much the bike squats down toward the ground when you sit on it.

This works because the length of a spring (and the height of your suspension) depends on how much weight is effectively sitting on it. Put 100kg on a particular spring and it will squash down a particular amount.

So if you build a shock absorber with a screw-adjusted collar that can take up some of the usual uncompressed length of the spring, you can adjust the amount of weight that can be sat on top of that shock absorber before it starts to compress.

Shall I draw some pictures with words?

SPRING
SPRING
SPRING
SPRING
SPRING
SPRING

Here's our spring. It's 6 lines of text high. Nobody's sitting on the bike.

Now I sit on the bike:

MY FAT ARSE
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING

I have compressed the spring, and my fat arse is riding 5 lines of text above the ground. I do not like this. My fat arse drags in corners, so I reconfigure my shock absorber to look like this:

RIGID COLLAR
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING

Now, when I sit upon the motorcycle, it looks like this:

MY FAT ARSE
RIGID COLLAR
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING
COMPRESSED SPRING

Et voila, my fat arse is now 6 lines of text above the ground, and no longer drags in corners.

I am pre loading the spring with a length of rigid collar equal to the amount that it was sagging by when I sat upon it.

[Bass]

Look at the picture, if you increase the preload, the spring is shortened.

But ONLY with the shock fully extended. It's tricky to see. Basically what adjusting the preload does is to move the starting point around.

Hookes law states that the spring compression is proportional to the load. So for a given load the spring length is determined. Normally the load is taken on the swing arm but with the shock fully extended it is taken internally by the shock.
All it does is change the load required to START the shock moving. Once the shock is moving, the load determines the spring length and so the preload determines the ride height.

[Bass]

Et voila, my fat arse is now 6 lines of text above the ground, and no longer drags in corners.

I am pre loading the spring with a length of rigid collar equal to the amount that it was sagging by when I sat upon it.

Precisely
You have increased your ride height back to where it needs to be, which is what I have been saying all along.
Its bump response i.e. the firmness of the ride is unchanged because our standard bump will produce the same deflection regardless of how fat your arse is.
Whistle up Robert taylor if you don't believe me.

I'll ignore the insulting shit for now.

[vifferman]

I'll ignore the insulting shit for now.

Have you started ignoring it yet, or can I get a shot or two in first?

[jrandom]

I'll ignore the insulting shit for now.

Just to be clear, what I was insulting was your ability to convey information meaningfully. I read your post, scratched my head, and thought, "huh"?

I have no doubt that you have a perfectly accurate understanding of how shock absorbers work, but I do hope you don't work as any sort of teacher...

[Bass]

Have you started ignoring it yet, or can I get a shot or two in first?

Be my guest - go for it!

[jrandom]

PIts bump response i.e. the firmness of the ride is unchanged because our standard bump will produce the same deflection regardless of how fat your arse is.

That is absolutely, one hundred percent correct.

As I said, I was not implying that anything you said was wrong; just that it was incoherent.

[Bass]

Just to be clear, what I was insulting was your ability to convey information meaningfully. I read your post, scratched my head, and thought, "huh"?

I have no doubt that you have a perfectly accurate understanding of how shock absorbers work, but I do hope you don't work as any sort of teacher...

Ok 10 out of 10 on that one

[NZsarge]

.........

[Bass]

Just to be clear, what I was insulting was your ability to convey information meaningfully. I read your post, scratched my head, and thought, "huh"?

I have no doubt that you have a perfectly accurate understanding of how shock absorbers work, but I do hope you don't work as any sort of teacher...

Actually, I certainly don't claim it to be perfectly accurate - that's a whole specialist field in itself, but I get by

[Bass]

That is absolutely, one hundred percent correct.

As I said, I was not implying that anything you said was wrong; just that it was incoherent.

Actually, these days, it's probably not correct because it assumes that you don't have a rising rate linkage

[Bass]

OK - despite your emphatic (and arrogant sounding) rebuttal, I *do* actually understand how shocks work, what preload does, etc.
I just took issue with your assertion that preload alters ride height, although your subsequent modification to make it effective ride height is better.

I humbly apologise for any apparent arrogance, but I still stand by my assertion that the primary effect - indeed the only real effect is to change the ride height

[tri boy]

I'm with you on this Sarge. Please stay out of this one for a while Robert

[jrandom]

... it assumes that you don't have a rising rate linkage

I'm not familiar with products in the market (I probably know less than you do, for that matter) but I would have assumed that any motorcycle with a rising rate linkage would have it designed to operate linearly in the range of travel affected by the suspension's available preload adjustment.

For what it's worth, correct me if I'm wrong, but as far as I can see (just thinking about it now, off the cuff) the effect of a rising rate linkage could be achieved with an appropriate progressive spring.

I assume that design engineers go for rising rate linkages because it's cheaper than speccing progressive springs, and allows a finer-grained control over the latter stages of the suspension travel.

Am I missing anything?