Effect of preload

[gregr]

So my new bike is a 2013 Ducati Multistrada, with the fancy new skyhook suspension. Compared to everything else I've ridden, this bike is _tall_. At least for me.

The preload is electronically adjustable, and has settings from 1 (lowest) to 24 (highest). Each "click" corresponds to about 0.5mm. Switching from 1 to 8 to 24, I can feel the back of the bike moving up.

On settings from 1-10 or so, I can touch my toes to the ground. On 24, I can point my feet straight down and the ends of my toes touch the ground. Ok in the garage, less confidence inspiring elsewhere. :-) In "enduro" mode, it defaults to 24. I want to change it to 8 or so, and I'm wondering if there's any bad consequences to that.

My question is - other than ride height, what is the effect of changing the rear preload?

My assumption is less travel to the top/bottom - but with a progressive rate spring, seems like you're unlikely to bottom out anyway.

Can anyone help me understand how preload affects the suspension, and the bike's handling?

[Jmetz]

On settings from 1-10 or so, I can touch my toes to the ground. On 24, I can point my feet straight down and the ends of my toes touch the ground. Ok in the garage, less confidence inspiring elsewhere. :-)

Welcome to every time I ride. :lol:

[WolFeYeZ]

http://www.womenridersnow.com/docs/stories/3706/Shock%20Preload%20Example.jpg

^ That sums up my knowledge of this subject.

[sloridr]

suspension (http://www.amazon.com/Sportbike-Suspension-Tuning-Andrew-Trevitt/dp/1893618455)

Check out this book. I found it at my local Barnes and noble

[asp_125]

suspension (http://www.amazon.com/Sportbike-Suspension-Tuning-Andrew-Trevitt/dp/1893618455)

Check out this book. I found it at my local Barnes and noble

I would just take my bike to STM and say "Here, take my money!" :lol:

[asp_125]

Preload sets the amount of sag, rather than using it to tune ride height. Aim for 30-35mm of sag on streetbikes, 25-30mm for race bikes.

Read more: http://www.motorcyclistonline.com/howto/122_0508_motorcycle_suspension_setup/#ixzz2Sk27egRw

[TFOGGuys]

Preload determines loaded ride height, which controls where in the stroke the suspension operates and things like the chassis attitude and roll center. As a rule, you want to adjust preload at the rear to provide 27-35mm of sag when the rider is in riding position. Sag is measured at point directly up from the center of the rear axle, and is the difference between the suspension being fully topped out and compressed under the rider's weight.

[gregr]

Thanks all. So let me get specific. This bike has different "modes" - urban, touring, sport, and enduro. They adjust suspension settings, by default, as follows (sorry don't have the actual numbers on the shock rebound/compression settings, so I'll go with my unverified soft/hard impressions below), for single rider mode:

urban - preload 1, soft
touring - preload 8, medium
sport - preload 8, hard
enduro - preload 24, soft

So urban has the lowest preload, presumably to drop ride height. And enduro has soft settings, but a high ride height / preload - presumably for ground clearance.

Also, switching to 2-up mode, or +luggage mode, increases the preload to 24 in all modes (IIRC).

Any of these are adjustable. And given the default settings, it seems the bike is designed to operate (with the same rider) across the whole range. What I'm wondering is, what would be the actual impact of dropping the enduro preload to, say, 8? Or dropping the touring to 1?

(sorry if this is already answered and I'm just not getting it...)

[TFOGGuys]

Thanks all. So let me get specific. This bike has different "modes" - urban, touring, sport, and enduro. They adjust suspension settings, by default, as follows (sorry don't have the actual numbers on the shock rebound/compression settings, so I'll go with my unverified soft/hard impressions below), for single rider mode:

urban - preload 1, soft
touring - preload 8, medium
sport - preload 8, hard
enduro - preload 24, soft

So urban has the lowest preload, presumably to drop ride height. And enduro has soft settings, but a high ride height / preload - presumably for ground clearance.

Also, switching to 2-up mode, or +luggage mode, increases the preload to 24 in all modes (IIRC).

Any of these are adjustable. And given the default settings, it seems the bike is designed to operate (with the same rider) across the whole range. What I'm wondering is, what would be the actual impact of dropping the enduro preload to, say, 8? Or dropping the touring to 1?

(sorry if this is already answered and I'm just not getting it...)

Basically, the enduro setting is designed to improve ground clearance while allowing the full use of suspension travel for better ride and control on rough surfaces. Reducing preload while leaving compression and rebound settings alone would not cause any particular issues, other than making it easier to bottom the suspension over bumps and reducing ground clearance.

All of this assumes that the spring rate is correct for the rider weight. The increased preload for 2up riding is a way of compensating (somewhat) for the incorrect spring rate for the additional weight.

[gregr]

Basically, the enduro setting is designed to improve ground clearance while allowing the full use of suspension travel for better ride and control on rough surfaces. Reducing preload while leaving compression and rebound settings alone would not cause any particular issues, other than making it easier to bottom the suspension over bumps and reducing ground clearance.

Ah! Thanks Jim, that's what I was looking for. If I were to be on bumps and such, and bottomed out in the back, how would I know? As I write it that sounds like a stupid question...but is it obvious when it happens? Do I live to tell about it?

In reality, the worst I think I would do is a dirt road, but if I accidentally ended up on a rougher track, it would be nice to know what to look out for!


All of this assumes that the spring rate is correct for the rider weight. The increased preload for 2up riding is a way of compensating (somewhat) for the incorrect spring rate for the additional weight.

I'm guessing I'm a little lighter (150lb) than the "average" weight they'd design for, but with minimal luggage, I'm guessing I'm sort of in the average range.

[TFOGGuys]

Bottoming can be hard to detect unless it's pretty severe. If it's really bad it can compromise traction and control. Basically, it feels like just what it is, the suspension running out of travel and coming to an abrupt stop.

[gregr]

Bottoming can be hard to detect unless it's pretty severe. If it's really bad it can compromise traction and control. Basically, it feels like just what it is, the suspension running out of travel and coming to an abrupt stop.

Ok - thanks Jim!

[asp_125]

Bottoming or simply fork travel is pretty easy to find out on the front forks. Simply strap a zip tie to the lower fork leg (or upper for conventional forks) near the fork seal and ride. The compression of the fork will push the zip tie along the fork and you can simply measure the difference. The rear shock will be harder to apply the same technique, however, you might have to get creative.

[FZRguy]

Doubtful you will ever bottom the fork or shock on a 2013 Muti unless you are hucking it off jumps at the MX track. :)

[gregr]

Doubtful you will ever bottom the fork or shock on a 2013 Muti unless you are hucking it off jumps at the MX track. :)

Probably true! And the only way I'm going to be on a MX track is if I take a pretty serious wrong turn somewhere. :)

[Samko]

Probably true! And the only way I'm going to be on a MX track is if I take a pretty serious wrong turn somewhere. :)

Or if you ride with Grim.