Bonneville America Forums Forums Technical Forums General Tech Preload?

Ok, so I've tried to google some answers, but am still a little confused. Rear Shock Preload. I'm not quite sure I get it. Most of the info seems a bit more technical than practical. So, maybe I almost kind of got this... feel free to throw in your comments... If my shocks are set on the lightest setting, the springs wont be as compressed, so when hitting bumps the ride may be bouncier? If they are set on the heaviest preload, the springs are under more compression so the ride is more rigid? If I am correct, why would you want more preload?

So, more preload would lessen the chance of bottoming out?

yes, but too much will fling you off like a rag doll.

So how many of you guys actually change the preload of your bike when you ride two-up or load her down when going on a trip?

I do on my 440s...its easy, just turn the top.

I adjust the preload when riding 2-up. My wife weighs in around 130 lbs with gear. The bike is far too springy/bouncy with the shocks in the default (#2) position. I bump it up to two notches (to #4), and the bike handles very well like that. I set it back to #2 when I'm riding solo.

H.

The less preload on the rear shock won't make it more bouncy since the dampener will still be doing it's job but it will be softer and compress easier. It will also make it so the suspension won't carry as heavy a load without bottoming.

If you want to get into the mathematics look up Hooke's law of elasticity. The formula governing the mechanics of the spring is F=-kx (k is the spring constant, x is the distance the spring is compressed or stretched, F is the force required to compress or stretch the spring). The minus sign in the equation is there because the spring will exert a force opposing the force trying to compress it so that it reaches it's natural state of equilibrium.

So, when you add preload you are pre-compressing the spring (the lenth of the shock doesn't change but you can see grooves that show you how far you've compressed the spring, right?). By preloading you are adding a force component that opposes weight (payload) that you add to the bike. This way they operate the same way that they do if there is a small payload and no preload. This also explains why they feel more rigid if you add preload but no payload.

In other words, when you add preload the spring creates a force that pushes up from the ground. When you add payload it exerts a force on the spring that pushes down to the ground due to weight created by gravity. If preload is higher than payload, the springs feel rigid because there is not enough weight to counteract the opposing preload. If payload is higher then the springs operate normally by absorbing the potential energy created by gravity (by bouncing around uneven road surfaces) until the spring is fully compressed. Hope this helps, I tried to put it as close to layman's terms as I could.

Thanks, that's as good of an explanation as I've heard. When i got my new Progressive 812 shocks they came with a detailed proceedure for setting preload. Apparently, since there are dips (potholes,etc.) as well as raised bumps, the shock needs to be able to handle both. I was too lazy to go through the whole setup procedure recommended by Progressive and just left the preload in the stock (softest) setting. Since the shocks feel great, I'm not going to mess with them, but would be interested in hearing other people's setups.

I think I understand this all now too. Thanks, everyone. I will have to play around once my progressives arrive to figure out my setting(s).

Now for another question: what tool do you guys use to adjust the preload on the stock shocks? And is it easier to turn the preload up if the bike is on a stand, with no weight on the rear wheel?

I bought the Triumph tool.. it's small, cheap ($3 or so), and fits in my tool roll. Having said that, I use a Robertson screwdriver that fits the adjuster hole perfectly. The handle is long enough to easily adjust the stock. I don't take any weight off the bike, although it would go easier if I did. I do pop off my saddle bags to do this. They are on Easy Brackets.

H.

When I adjusted mine (stock), I went round a mates as he was the only person I could think of who might have a C-spanner.

Unfortunately, the ones he had were no good as the shape of them meant that bits of bike kept getting in the way, so we used a torx driver that he didn't mind sacrificing in an adaptor on a socket wrench, this did it fine.

This is also the main reason I have yet to adjust them back as I haven't been round there since

The proper tool would probably be better though

It's kind of funny. The 'proper tool' is just a bent rod. It's a bit short to use unless you have an extension. It's perfect for the tool roll though.

H.

The proper tool is dependent on the shocks you have.

If the ride does not feel right, adjust the rear shocks until it does.

There is definitely a sweet spot. If payload added, adjust accordingly.

A 5mm allen wrench was the "tool kit" on my Speedmaster, and it will adjust the shocks on level ground. A longer tool does make it easier (more leverage).

Here's the Triumph shock adjusting tool (for the stock rear shocks)



Part number T2300995

H.

Hi all. When I first bought my bike I thought I might have made an error of judgement on the style of bike for long rides as with the oem shocks and a back problem I was getting hammered.

Rather than having to buy a bike for practical reasons but with no real style, I decided to gamble on buying expensive shocks with Corbin and backrest.

For me it was the best decision I could have made. Mind you, hagon not having the spring ratings properly matched to a rider's weight caused me some physical and emotional grief for a couple of years. Eventually though, me and a few other blokes on here got hagon to change their specs so they would send the right springs to match varying rider weights.

Anyway, yes I regularly adjust my pre-load depending on two main factors. If riding with extra weight over my rear wheel which occurs mainly when i travel with luggage, given the weight I travel with is the roughly 50 to 60 kgs, I generally will need to rotate the collar that compresses the spring two revolutions downmTo get me that perfect pre-load setting.

The other factor I've noticed more recently is how hot or cold weather effects my preload. Without talking to anyone it's my opinion with the oil viscosity changes with temperature, which in turn varies a shock's ability to move about as freely or not due to the oil's thickness. I've only based this conclusion on looking at my shock's construction so bag me out if you want I don't really care. What's important for me is to find that sweet spot as I ride and when I say sweet spot I mean, more times than not my bum stays firmly planted on the seat and not being bounced off it. So with the viscosity thing I've only found a difference of one revolution between summer (hot days) and winter (cold days) though whilst This one revolution whilst it may sound a bit pedantic, it's enough for me to adjust my nitros given it's a simple process anyway.

Btw, fwiw I've read a fair bit about sag and whatnot but after a while of persistently searching for the comfort I paid good money to find, the best indicator to work out whether your shocks are dialed in correctly or even any good, is whether your backside stays nicely planted on your seat. The rest is experimenting either compressing or alternatively de-compressing the springs to work where you are in the spectrum.

That's my experience anyway.

Stacka