Jump to content
Sign in to follow this  

Valving vs. Springs?

Recommended Posts

Im trying to raise a genius topic here. I have never seen this talked about before. I know for a fact that valving and proper spring rates are important, but I have an observation to propose. I like my front end with a lot of spring, as in one rate higher, and almost no valving.The opposite goes for the rear, I like lots of valving and light springs. Where am I going with this? I guess I am trying to ask the question, does it matter and what is the reason for this? Also what is the advantage to this and what does it change? I know for a fact that lots of valving makes for a very dampened feel, and more spring gives more bounce. But why not run a balanced feel of spring and valving? I know everyone does their own thing and its all preference. Is my setup wrong thanks to a technicality of physics? I dont know what to think on this subject, maybe some people could weigh in how they run their setups and why you guys think it works the way it does. As in give your type of riding, dirt, and bike/stroke count. I dont want to hear anyone saying someone elses setup is wrong. I just want to hear what you guys think about how I think, and weigh in with your settings/thoughts. thanks guys.

Share this post


Link to post
Share on other sites

My thinking is it is a chicken or the egg kind of deal.

For a stiff fork spring you could take a lightly sprung bike, jack up the compression damping, and make it “feel” like the stiff spring with the same bottoming resistance.

On the rebound side if you like the way the front end pops up with stiff springs you can lighten the rebound damping on a softly sprung bike and get it to “feel” the same way. Or vice-versa.

My thinking for picking a spring rate is you want to find a spring that is light enough to get good weight transfer to the front wheel under braking. Brake dive weights the front tire and sets up the steering geometry for a turn. On the rear the spring needs to be soft enough to transfer weight to the back under acceleration and hook up the tire.

Low speed trail riding needs light springs to get the right weight transfer. High speed desert riding needs stiffer springs to keep the same weight transfer and “feel”.

I think there is more to spring selection than setting you sag. Somehow sag has been translated from a starting point to a destination. If you hack around on preload you can get the same sag with just about any spring IMO.

Share this post


Link to post
Share on other sites

So.........

The fork spring needs to be soft enough so keep the wheel from pushing and stiff enough to keep it from tucking.

The rear needs to be soft enough to hooked up the tire but stiff enough the bike doesn't wheelie out every time you hit the gas.

In between is a huge overlapping gray area of tuning the stacks.

Share this post


Link to post
Share on other sites

I'll just throw some real basic stuff out for consideration. The springs first have to support the weight of the bike and rider. That's what setting the preload (sag) is about. You need the springs compressed a bit under normal operating loads so that the suspension can extend into low points as well as compress in response to the high points. All quite obvious to most, I'm sure.

But from that point, consider: "stiffer" in a spring means a higher spring rate, say 60 pounds/inch vs. 50 lbs/in. When an obstacle is encountered that puts a load of 100 pounds on the spring, one will compress 1.67" while the other compresses 2". Not such a great difference, but what about the next two inches? If both springs are still under the influence of that same 100 pound additional load, and the suspension encounters and two inch obstacle, the first spring will need another 120 pounds of force on top of the first hundred to comply with the bump without transmitting the energy of the impact to the chassis and rider, while the second spring needs only 100.

Softer springs store less energy, so the return less of it on rebound, also. So the softer spring will produce a more compliant ride, but it may also cause two things that are undesirable: excessive bottoming, and just too much motion and change of attitude in the chassis. This is where damping comes in. The function of damping is quite simply to control the action of the suspension unit in a way that minimizes extremes of motion on the one hand, while minimizing energy transfer to the chassis on the other. Seldom a very simple thing to accomplish in every situation.

The answer to your question, then is that a balance must be struck between spring and damping that suits your particular needs. The spring must be soft enough to yield a pleasant ride, but stiff enough to offer a stable handling platform and progressively resist excess compression. Damping must allow motion within a desired range of stroke speeds while resisting excesses. I doubt there's a simple answer, and there certainly isn't a one-size-fits-all approach, even for what would look like two identical situations.

Share this post


Link to post
Share on other sites

As you know in this case the springs job is to provide and maintain ride height. The valve's job is to control the spring. You also have a personal opinion of what you like best and really that is all that matters because going as fast as you can on a motorcycle is all about being as comfortable and in control as you can be while being as far outside your comfort zone as possible.

I am guessing you would not be asking this question if you were 100% satisfied with your suspenders or maybe you are just wondering if you are normal, either way that is couple of reasons why R & D happens every day, we are always looking to do better.

My personal experience with over springing and under valving is a very deflective feel. To me it just feels like the tire is not following the ground as much as it is bouncing across it. The other end of the spectrum in some situations will feel very similar. Have you ever had your suspension... (I'm going to use the industry accepted slang here) pack up on you? If you have then you know how violent the energy in those springs can be. I think that under sprung and over valved would lead to more packing.

The real problem is there are infinite number of variables to make the perfect setup for every rider. Until we use a computer to analyze the variables as they happen and make adjustments in real time, we will need to compromise with what we like best.

I like my suspenders to be soft enough to not rattle my teeth out on breaking and accelerating bumps and stiff enough to not feel like the frame is going to break in half if I accidentally come up short or go long. Even more importantly I need that thing to track straight. When going through rollers, woops, or a long series of square edge stuff I hate that feeling that at any point the rear end is going to take off side ways. That is the major problem I struggle with. I haven't found out if it is too much spring, not enough spring, too much comp. or not enough comp. dampening, too little or to great rebound dampening and so on... you get the point.

Share this post


Link to post
Share on other sites

All I can relate to is my own experience. I had a Klx450 and they come softly sprung. I cranked up the compression dampning on the forks and shock. Turned down the rebound and cranked up the shock spring adjuster to get the proper race sag. I thought it was stupid to get it new springs. Then I thought I would try it so I had it sprung for my weight (200lbs). No valving changes just new oil, oil height in forks and springs. It was not the same bike. It turned better and the faster I rode the smoother it was. It was my first experience having it done and made a believer out of me.

Share this post


Link to post
Share on other sites

For plush I have had the best luck with stiff springs, low compression damping and stiff rebound.

  • Stiff springs keep the suspension from bottoming
  • Low compression damping lets the wheel get out of the way of a bump
  • Heavy rebound stabilizes the whole thing.

Passenger cars use this kind of setup, so nothing new here.

Going the light spring heavy compression damping route the trouble I have had is the suspension reaches it’s highest velocity at the start of a bump. Over a bump the hub traces out an arc like path.

hub-velocity.png

The arc path produces the highest vertical velocities at the start of the bump and near zero velocities as the wheel rolls over the top. Plotting those velocities gives some idea how much the suspension velocity changes over a bump.

2-peak-vel.png

With soft springs and heavy compression damping the high velocities at the start of a bump lock up the compression damping circuits and the bike rides rough. Loosen up the high speed damping and the suspension bottoms.

The spring must be soft enough to yield a pleasant ride, but stiff enough to offer a stable handling platform and progressively resist excess compression. Damping must allow motion within a desired range of stroke speeds while resisting excesses. I doubt there's a simple answer, and there certainly isn't a one-size-fits-all approach, even for what would look like two identical situations.

My personal experience with over springing and under valving is a very deflective feel. To me it just feels like the tire is not following the ground as much as it is bouncing across it. The other end of the spectrum in some situations will feel very similar. Have you ever had your suspension... (I'm going to use the industry accepted slang here) pack up on you? If you have then you know how violent the energy in those springs can be. I think that under sprung and over valved would lead to more packing.

Since you guys have had success going the soft spring heavy damping route what have you been doing to the compression damping setup.

Loosen up the bleed circuits?

Something special in the compression shim stack?

Can’t seem to figure it out, hoping you can provide some tips.........

Share this post


Link to post
Share on other sites

I don't think I said I'm using unusually soft springs, and in fact I'm not. They're the standard rates on an '06 YZ450, and I'm 180 pounds in streets and a desert racer.

The fork base is pretty ordinary, and except for the clover leaf check plate, it's nearly stock.

The mid is another matter. It's a Gen2 dual spring "Dell Taco" set up from SMART Performance with a little variation that Dave worked out with me. There's no float in the mid valve, so in reality, it's no longer a mid-speed valve at all. I have a crossover shim behind the first face shim that provides a light lead in (a bit like a bleed or float, but not quite, and then the mid stack is a simple single stage affair. Because of the DSDT setup, the entire stack can lift off the piston at very high pressures like a blowoff. This setup works exceptionally well for me.

Share this post


Link to post
Share on other sites

gray, have you ever tried another blowoff at the BV?

would like to hear if any other runs this and whats the thoughts on it

Share this post


Link to post
Share on other sites

You don't need to change valving at all if you have the proper spring for your weight and the stock valving gives you the adjustability you need. If you get the right spring and you run out of adjustability with you rebound\compression then you need to do the valving.

Share this post


Link to post
Share on other sites

What if you can get your clickers dialed in like you want, but it's harsh over small chop? What if everything's fine except for the fact that the front end deflects and skips all over on 3" rocks? What if both of those are good, but the fork blows through the stroke in big whoop sections?

There's more to it than the question of whether your adjusters can be brought into range. It is, however true that without the right spring rates to begin with, the suspension doesn't have a chance.

Share this post


Link to post
Share on other sites
gray, have you ever tried another blowoff at the BV?

would like to hear if any other runs this and whats the thoughts on it

No, I haven't. At this point, I'm pretty tickled with the way the thing works, and although I might experiment some more with the fork later, I'm more interested in getting the shock to work as well as the front end does.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×