Motorcycle spring preload vs. snowmobile

If you don't know, snowmobile rear suspension systems (called a skid) are a self-contained unit with a front shock with a coil-over that absorbs energy as the front of the track impacts a bump. Typically, it is coupled to the rear shock and they work in tandem to disburse the energy throughout the skid. Towards the rear of the skid, torsion springs are used as the primary suspension of weight of the sled, rider, gear; the rear shock is often naked, has 10-15" of travel, and does a majority of the work.

With that context out of the way...

...Adjusting the torsion springs up on a sled is the best way to increase ride quality. It makes the ride firmer, but allows for more bump compliance especially at higher speed on rutted up trails as the shock can do that work while the springs manage the sled's free weight.

I have never messed with the preload on a motorcycle until last week.

With the new, firm Corbin seat, ride quality on the Honda was subpar. Teeth chattering at some points! I have read on this forum that the Gold Wings are severely undersprung, and to crank up the preload out back to make the ride softer.

This is opposite of the snowmobile - yes, increased spring pressure enhances ride quality on a sled - but it does not make it softer, it makes it more controlled.

So, I followed the advice on here and cranked up the rear preload using the knob to about halfway between soft and hard. It was at soft, as set upon delivery.

What a difference! The rear shock actually absorbs bumps pretty well; I can push down on the back of the bike and it compresses easily. I am pleasantly surprised, at not really sure why the two types of vehicles result in such different outcomes from the same adjustment.

I don't pretend to know why either and have never owned a Snowmobile...I do know that a couple years ago when my bike was at the dealer for some service, the owner and I were talking about the rough ride I had on my F6B..He took off the side cover and adjusted the rear shock, that was set at "0", to 17 clicks, or about halfway on the adjuster, and the ride seemed to be much better than before he changed the setting...I have left it that way and all feels much better over bumps and rough roads....JMHO.....Regards

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Originally Posted by opas ride

I don't pretend to know why either and have never owned a Snowmobile...I do know that a couple years ago when my bike was at the dealer for some service, the owner and I were talking about the rough ride I had on my F6B..He took off the side cover and adjusted the rear shock, that was set at "0", to 17 clicks, or about halfway on the adjuster, and the ride seemed to be much better than before he changed the setting...I have left it that way and all feels much better over bumps and rough roads....JMHO.....Regards

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17 Clicks from either stop is the "golden number"! Shortly after taking delivery of my 6 one of the first orders of business was adjusting the shock preload/dampener. Several members tried different setting and all came to the conclusion 17 clicks was the mid point of a total 34 clicks available. I'm 250 lb and the mid way adjustment provides a smooth/controlled ride without any "spine jarring ride harshness".

Ride Safe

bob109

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Originally Posted by bob109

17 Clicks from either stop is the "golden number"! Shortly after taking delivery of my 6 one of the first orders of business was adjusting the shock preload/dampener. Several members tried different setting and all came to the conclusion 17 clicks was the mid point of a total 34 clicks available. I'm 250 lb and the mid way adjustmeny provides a smooth/controlled ride without any "spine jarring ride harshness".

Ride Safe

bob109

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Thanks guys. I was going to ask your weight to see if where mine is set is a good match for my heft. I am about 235 lbs myself, so close enough. I did not count clicks; I twisted the knob up to the third line from HARD which is around halfway. The ride is noticeably smoother.

I think the reason that many feel that the "0" setting is too hard is in error. I think it is so soft that with the shock set so soft, we were actually "bottoming out". When you crank up the setting to 17(or so) it allows the shock to do it's work without hitting the stop.

Remember you are not compressing the spring. You are adding hydraulic pressure inside the shock.

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Originally Posted by Sorcerer

Remember you are not compressing the spring. You are adding hydraulic pressure inside the shock.

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Yes and no. Dialing up the preload actually compresses the spring via hydraulic pressure on a piston sitting on the spring. By increasing the initial compression on the spring BEFORE adding rider weight (preload), you actually raise the frame of the bike (or snowmobile) allowing for increased travel when you hit a bump. Works the same on bikes, snowmobiles and cars. In other words, if the bike has 4 inches of suspension travel available, and you use up 2 inches from static weight of the bike and rider you only have 2 inches left to absorb bumps. If you increase the preload so the suspension only sags 1 inch with the static weight, you now have 3 inches available to absorb the bumps. The suspension will feel firmer because of the increased compression of the spring, but you won't bottom out as easily so the ride will feel better. The rate that the suspension moves at in response to a bump is called damping (compression when you hit the bump, and recoil as the suspension returns to the normal state) and is controlled by the flow of hydraulic fluid through the internal porting of the shock.

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Originally Posted by Travelor

Yes and no. Dialing up the preload actually compresses the spring via hydraulic pressure on a piston sitting on the spring. By increasing the initial compression on the spring BEFORE adding rider weight (preload), you actually raise the frame of the bike (or snowmobile) allowing for increased travel when you hit a bump. Works the same on bikes, snowmobiles and cars. In other words, if the bike has 4 inches of suspension travel available, and you use up 2 inches from static weight of the bike and rider you only have 2 inches left to absorb bumps. If you increase the preload so the suspension only sags 1 inch with the static weight, you now have 3 inches available to absorb the bumps. The suspension will feel firmer because of the increased compression of the spring, but you won't bottom out as easily so the ride will feel better. The rate that the suspension moves at in response to a bump is called damping (compression when you hit the bump, and recoil as the suspension returns to the normal state) and is controlled by the flow of hydraulic fluid through the internal porting of the shock.

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Good explanation. It must be that the F6B rear shock is a rising rate shock ... as the motion of the shock progresses through its stroke, it gets progressively firmer. With the spring preload at "SOFT", the static weight mentioned by Travelor is compressing that shock through the first half of its travel, which may be the softest portion of its travel, and once bump energy hits the shock we are experiencing the final 2" of its travel, which is damped very firm.

Most modern snowmobile shock absorbers are rising rate ... they are designed to absorb small "trail chatter" but become progressively firmer as the stroke of the shock increases towards the stop.

On another note, I see that there is some disagreement about whether the dial adjuster is a damping adjustment for the shock (moves a piston in the shock, reducing travel but increasing hydraulic pressure) or a spring preload which has nothing to do with the shock directly except to create a condition that increases its travel.

On a snowmobile, it is almost ALWAYS better to go up in spring size rather than dial the existing spring up to a stiffer setting. This is where it is different than a bike. Cranking up springs eats up shock travel on a snowmobile because of how the skid is a self-contained unit; one is actually pre-collapsing the skid by doing this and taking away an inch or two of travel, which is also the least damped portion of the shock travel, which results in a harsh small bump ride. By going up a size in springs, you maintain the full travel of the skid (again, self-contained and coupled) but buy yourself additional control of the motion of the skid as a unit by controlling the static weight better. This, is turn, allows the shock (s) to do their "thing".

The previous owner, weighted about 170-180# & had it set at 17 clicks. It like to broke my teeth. I checked the owners manual, if my memory is correct, factory setting is 3-4 clicks. I cranked it back 17 clicks to "0" and up 4 clicks. I'm 200# & it feels great to me. I saw a snowmobile on TV once or twice.
We went to Leesburg, FL. Bikefest this weekend. As usual, it was packed. Lots of folks from all over the country.

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Originally Posted by olegoat345

The previous owner, weighted about 170-180# & had it set at 17 clicks. It like to broke my teeth. I checked the owners manual, if my memory is correct, factory setting is 3-4 clicks. I cranked it back 17 clicks to "0" and up 4 clicks. I'm 200# & it feels great to me. I saw a snowmobile on TV once or twice.
We went to Leesburg, FL. Bikefest this weekend. As usual, it was packed. Lots of folks from all over the country.

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Here's two more:

https://imgur.com/a/vjaAMqH

First one is near Watertown, NY, about a month and a half ago. There are 183 windmills up there and when they are cranking, you know it if standing near them.

Second one is myself and a friend, after riding through a sudden and unexpected lake effect snowstorm that dropped about 15" in three hours. Had to go 10 mph or less for 10 miles or snow would come over hood and block headlight.

Snowmobiling is a lot of fun ... still ranks higher than riding bikes in my opinion, but its enjoyment is much more dependent on weather and conditions than motorcycling. After all, on bikes, the trails are always groomed! 1100 miles this year, we average 1500-2000. Been riding them 20 years, ~37,000 miles.