Suspension preload settings

[parkmoy]

As a fairly new rider I need advice on setting the rear preload. I weigh 200 lbs and at the moment have it set just short of the middle of its travel. It feels fine on smooth roads but quite bumpy on rougher tarmac. Is there a way of determining the optimum setting?

 

[RedLdr1]

Is there a way of determining the optimum setting?

I usually try different settings and see what feels, and works, best. It sounds like it is still a bit too stiff so I'd soften it up several clicks and see how that feels... I also suggest you write down your settings and note how they feel as you adjust it.

 

[Rmcapozzi]

Adjusting shock pre-load is done to correctly set the height or sag of the suspension so that there is adequate travel up/down. It will not change the stiffness of the suspension. To do that you'll need dampening/rebound adjustments (the NT doesn't have them) or a different spring rate (requiring replacement of the current spring). If the sag is to low, the suspension will not have enough travel to absorb raised bumps in the road. This may cause your suspension to "bottom out". If your suspension is bottoming out, then it could result in quite a sharp jolt. The same is true if you don't have enough sag. The suspension will be able to "top out" more easily and again giving a more rough ride.

Check out this article. It explains how to set the sag (by using your pre-load). http://www.motorcyclistonline.com/howto/122_0508_motorcycle_suspension_setup/

 

[Rich]

I set mine to the highest setting at which the suspension compresses just a bit from its "unladen" state when I sit on it. If it's got too much sag you will get an unstable-feeling ride. If it's too little you get a really harsh ride under some conditions.

Because of the way coil springs are typically made, tightening the preload also removes some portion of the spring from being able to compress, making the spring rate higher (more force required to absorb a given displacement - like a bump). This because when increasing the preload part of that last coil-and-a-half (on one or both ends) gets pushed down to where it no longer can extend at all. This effectively shortens the usable portion of the spring, making it stiffer earlier in its travel.

 

[Rmcapozzi]

I set mine to the highest setting at which the suspension compresses just a bit from its "unladen" state when I sit on it. If it's got too much sag you will get an unstable-feeling ride. If it's too little you get a really harsh ride under some conditions.

Because of the way coil springs are typically made, tightening the preload also removes some portion of the spring from being able to compress, making the spring rate higher (more force required to absorb a given displacement - like a bump). This because when increasing the preload part of that last coil-and-a-half (on one or both ends) gets pushed down to where it no longer can extend at all. This effectively shortens the usable portion of the spring, making it stiffer earlier in its travel.

When you change the pre-load the swing arm will move up/down. Although you are compressing the spring with preload, it still doesn't change the spring rate or firmness of the rear shock. Initial firmness (to begin additional compression of the spring) will be higher but compression from there forward will follow the exact rate of spring compression as before.

Pre-load on motorcycles is used to adjust the ride height not the stiffness of the ride.

Lot's of articles out there on the subject (see below for a few).

http://www.sportrider.com/tech/146_9510_tech/

http://www.sonicsprings.com/catalog/preload_tech_article.php

http://www.sportrider.com/suspension_settings/suspension_setup/146_0402_suspension_setup_guide/viewall.html

 

[Rich]

When you change the pre-load the swing arm will move up/down. You aren't really "compressing" the spring until you have the suspension completely topped out. At that point, then adding pre-load will compress the spring but I don't think you can dial that much into the NT. If you were able to compress the spring with the pre-load adjuster, then the initial compression of the suspension would feel more harsh but the spring rate would remain the same regardless of the amount of pre-load.

Pre-load on motorcycles is used to adjust the ride height not the stiffness of the ride.

Lot's of articles out there on the subject.

http://www.sportrider.com/tech/146_9510_tech/

http://www.sonicsprings.com/catalog/preload_tech_article.php

http://www.sportrider.com/suspension_settings/suspension_setup/146_0402_suspension_setup_guide/viewall.html

I confirmed my statement by testing this activity on my wife's bike (a Suzuki LS650), basically because it's easier to measure, with it having the exposed rear suspension.

The bike is set at it's lowest/softest for her. I measured the distance between the top and bottom collars of the springs at 5.3 inches. I tightened them one notch - still 5.3 inches. Tightened them another notch - the springs very visibly were compressing this time, changing the setting was much harder, and the measurement was now 5.2 inches. I tightened them the remaining 2 notches (again, very visibly compressing) and the distance was just under 5 inches.

Of course these changes were after the point where the max suspension travel was reached. That's why it's called "PRE-load". And I stand by my statement that the spring rate is affected. You can watch the coils at the end compress against the "base" coil, shortening up the effective length. Of course, normal suspension action does this, as well, but tightening the preload changes the starting point.

None of this affects shock damping, of course. But changing the preload on my NT very definitely affects the degree of impact when hitting things like drain covers and such on the road.

 

[parkmoy]

Sounds good BUT anyone any ideas how to get the measurements on a DV? - the panniers get in the way

 

[Rich]

Sounds good BUT anyone any ideas how to get the measurements on a DV? - the panniers get in the way

I do it by feel. But to measure it you could use any fixed point on the frame relative to the real axle while on the centerstand and measure the sag when on the ground (with you mounted). Takes two to do it, of course.

Yesterday I confirmed it's possible to set the preload on the NT so high that it compresses not at all with me sitting on it, even bouncing up and down on it.

 

[Rmcapozzi]

I confirmed my statement by testing this activity on my wife's bike (a Suzuki LS650), basically because it's easier to measure, with it having the exposed rear suspension.

The bike is set at it's lowest/softest for her. I measured the distance between the top and bottom collars of the springs at 5.3 inches. I tightened them one notch - still 5.3 inches. Tightened them another notch - the springs very visibly were compressing this time, changing the setting was much harder, and the measurement was now 5.2 inches. I tightened them the remaining 2 notches (again, very visibly compressing) and the distance was just under 5 inches.

Of course these changes were after the point where the max suspension travel was reached. That's why it's called "PRE-load". And I stand by my statement that the spring rate is affected. You can watch the coils at the end compress against the "base" coil, shortening up the effective length. Of course, normal suspension action does this, as well, but tightening the preload changes the starting point.

None of this affects shock damping, of course. But changing the preload on my NT very definitely affects the degree of impact when hitting things like drain covers and such on the road.

As far as spring rate and the effects of compressing on a spring's spring rate, we're probably really saying the same thing just differently. Lots of good article out there on that subject.

Your description of the results with the "preload" adjuster makes sense to me. Thanks for the information. The ride would definitely feel different for the initial compression of the spring. Compression of the spring from that point forward, would be identical as if there weren't any preload (see previously referenced articles on spring rate and preload).

Thanks!!

 

[Rmcapozzi]

Sounds good BUT anyone any ideas how to get the measurements on a DV? - the panniers get in the way

Place some blue painter's tape on your pannier lid.
Draw a horizontal line on that tape.
Now you can measure the distance from the floor (fixed point) to the line on the tape (adjustable) to measure changes in the sag.

To identify total height of the suspension:
Place the bike on the center stand.
Measure the height between the floor and the line on the tape
Measure the height between the floor and the rear wheel
Subtract the height of the rear wheel from the height to the tape
That will give you a pretty good measurement on the max, unladen height of the suspension.

 

[Warren]

I think trial and error is the best approach. Start at the factory setting and add or subtract clicks from there. I weigh 160 and had to subtract clicks. I am at 6. if I added load or a passenger I would go back to factory setting plus a few.

 

[parkmoy]

I think trial and error is the best approach. Start at the factory setting and add or subtract clicks from there. I weigh 160 and had to subtract clicks. I am at 6. if I added load or a passenger I would go back to factory setting plus a few.

That's very difficult when, as a new rider, you really don't have much idea of how the bike should feel. I have tried Rmcapozzi's suggested method and on a short test run with a measured sag of 40mm things seemed OK. I'm waiting for the weather to improve before giving it a proper test. The new setting is considerably firmer than I had it before.

 

[Warren]

The reason Honda provides like 40 settings is so that you can fine tune it for different riding situations. During the week I commute at low speeds and on bumpy roads so I have the setting on the soft side. When I go for more spirited riding on weekends I stiffen it up. There is no formula to determine what is best for every situation. Over time you will develop a feel for the bike. If you have no idea where to set it use the factory 11 clicks.