Preload question

HootOwl

HootOwl

Well-known member
Hey guys

I have managed to thoroughly confuse myself whether increasing rear shock preload will raise or lower seat height?

I seem to think that removing/decreasing preload also lowers the seat height, but that seems counter intuitive.

So to decrease seat height (forgetting about Sag and the like for now) is it add or remove preload ?
 
Or an adjustable tie rod as on many Ducati's...

$_3 (1).webp
 
Exige said:
The sock length won't change - your shock would need a separate adjustment on it :unsure:
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Shock even. Clearly your socks are nothing to do with preload, more like prewash :ROFLMAO:

You may have a tie-rod on the bike which would alter the seat height (very marginally) if it were shortened or lengthened but it would also have a whole load of consequential knock on effects at the front end that you would need to start really fiddling about
 
West Cork Paul said:
Shock even. Clearly your socks are nothing to do with preload, more like prewash :ROFLMAO:

You may have a tie-rod on the bike which would alter the seat height (very marginally) if it were shortened or lengthened but it would also have a whole load of consequential knock on effects at the front end that you would need to start really fiddling about
Click to expand...
🧦
 
Its a Multistrada, so no tie rod. I cant really change the arse end and measure it while I sit on it, so I cant test what if anything works.

I read online in several places that decreasing preload will reduce ride height, but just seems counter intuitive to increasing preload, and thus shortening the spring.?

The theory behind decreasing preload seems to be the bike squats more with less preload applied when a rider is added, but I am working with Excel problems today and my head is fried, so can I hell as like visualize that lol
 
HootOwl said:
Its a Multistrada, so no tie rod. I cant really change the arse end and measure it while I sit on it, so I cant test what if anything works.

I read online in several places that decreasing preload will reduce ride height, but just seems counter intuitive to increasing preload, and thus shortening the spring.?
Click to expand...
The spring length changes but not the length of the shock - it will change the ride height due to the static and rider sag being altered.
 
HootOwl said:
Its a Multistrada, so no tie rod. I cant really change the arse end and measure it while I sit on it, so I cant test what if anything works.

I read online in several places that decreasing preload will reduce ride height, but just seems counter intuitive to increasing preload, and thus shortening the spring.?
Click to expand...
Does decreasing preload make the suspension softer so there is more give when you sit on it resulting in a lower seat height ?
 
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I have a DVT with manual suspension Paul

I have wrapped my head around it now. Last year I wound the preload right up front and rear on it thinking that I was lowering the seat height, but obviously I wasn't ....

This year I thought about it a bit more and moved the preload (and other) settings nearer where they ought to be. i.e. softened off from where I had them.

To be fair, its not made a massive difference to seat height anyway, but what does happen now when I shove my 87 kilos on it, is that the suspension lowers more than it did with all the preloads wound up.

The Multi is good enough that it handled OK anyway with the suspension rock hard, but it should ride even better now.

I guess the answer is, reducing preload allows the ride height to reduce under rider/passenger load. (I hit both goals)

Its the opposite of the old twin shock bikes where we would crank up the shock loading cam to carry a passenger which raised the tail of the bike somewhat.

Now, I can visualize how it works, I was struggling before :)
 
HootOwl said:
I have a DVT with manual suspension Paul

I have wrapped my head around it now. Last year I wound the preload right up front and rear on it thinking that I was lowering the seat height, but obviously I wasn't ....

This year I thought about it a bit more and moved the preload (and other) settings nearer where they ought to be. i.e. softened off from where I had them.

To be fair, its not made a massive difference to seat height anyway, but what does happen now when I shove my 87 kilos on it, is that the suspension lowers more than it did with all the preloads wound up.

The Multi is good enough that it handled OK anyway with the suspension rock hard, but it should ride even better now.

I guess the answer is, reducing preload allows the ride height to reduce under rider/passenger load. (I hit both goals)

Its the opposite of the old twin shock bikes where we would crank up the shock loading cam to carry a passenger which raised the tail of the bike somewhat.

Now, I can visualize how it works, I was struggling before :)
Click to expand...
There are some useful suspension threads pinned at the top of the Suspension section in The Workshop

Tyres & Suspension

Here's the place to share your knowledge and experience, or to learn new stuff, on those important things that keep you and your bike the right way up.
www.ducati.community www.ducati.community

Your suspension, front & rear, is a ‘fixed’ length (when static) so the bike sits at a fixed height (with no-one on it) above the axles. When you increase the preload on the spring you are simply pre-compressing the spring to reduce its overall ability to compress.

Imagine if that spring is 30cm long and when fully compressed is 15cm long. If you increase the pre-load to reduce its length to 25cm it now can only move a further 10cm rather than the full 15cm.

Compressing, or squeezing, the spring doesn’t affect the ‘fixed’ static length of the suspension unit because for every force in one direction there is an equal but opposite force in the opposite direction. Thus, applying force to squeeze the spring results in the spring trying to push back and, due to the design of the suspension units the telescopic parts are pushed apart. As you reduce the uncompressed length of the spring the spring extends the length of the suspension resulting in no overall change of the static length of the suspension so your seat height doesn’t lower or raise.

Oh dear, I do hope this isn’t confusing.

Because the spring can only be compressed 30cm (in this example) if there is no preload then when the rider and pillion gets on it feels ‘soft’ and the bike sags under the weight. If there were lots of preload applied the bike couldn’t sag as much when the rider gets on because much of the possible 15cm of movement has already been taken up by the preload. It now feels ‘hard’. Also the ride will feel harsher because the spring has less overall travel available to it due to the fixed preload that was applied. There is a whole load more that can be detailed here but I’m trying to keep it brief.

FYI the suspension has an overall length of travel front & rear which you’ll find in the manufacturers specs for your bike. The suspension works best when it’s working within the middle third of that travel. ie, assume your rear shock has an overall travel length of 170mm (which is yours I believe) then you, ideally, want to set the preload such that when you (or you and a pillion if that’s the weight for that trip) sit on the bike (in full gear) the suspension compresses by 57mm. The spring will then be set at its optimum.

If anything is not clear please ask, it took me a while to get my head around the subject.

If your aim is to lower the seat height then I believe there are lower seats that be bought, or even complete frame lowering kits which involve a new, shorter rear shock, and dropping the front triple clamps down the fork tubes.

I don’t know whether your bike has an adjustable (for height) seat or not; I guess not as that’s the first thing an owner can do.
 
The bike does have an adjustable seat Paul. I am on the lowered setting. I bought a low Pikes Peak style seat too.

I can manage the bike OK, but am always happier when I can get both feet properly flat on the ground. (I am there now)

It all stems from when I was pushing it backwards into the garage last summer and it went down on to its side.

I slowed it to a gentle fall as it was falling on to me alongside it, and there was zero damage, but it still knocked my confidence somewhat.... in addition to being next to impossible to pick up in a confined space and on my own. I collected a nice set of bruises as a reward for slowing it down :)

I know that 99.9% of motorcycle riding is in the head. I had to do something to try and reconcile that and get my mojo back ;)
 
I was stuck with the bike in the entrance to the garage door lol. The bike squeezed itself down by running down me, but there was very little room to position and get it back up again.

I had to dead lift it up past 20 degrees and then try to lever/push it on to it's wheels in a very limited amount of room but not allowing it to drop again. Luckily my daughter was on hand to supply the 5% effort that I just did not have left when switching from lift to push.

It did fk up my back in doing it for the next 6 weeks or so too :(
 
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