theoretical suspension question

OK, let's say you have a rear shock whose rebound damping does not work, as in, there is not enough rebound damping thus allowing the spring to "pogo".

Now, you can not rebuild the shock and fix the damping so to counter-act the pogo effect, theoretically, would it be better to increase the spring preload thus effectively reducing the distance the spring will travel while it pogoes?

Or, would it be better to reduce the preload in the spring thus effectively slowing down the rate at which the spring rebounds?

Obviously, neither case is ideal, but purely in the interest of discovery which one would you chose and why?

The purpose of either adjustment would be to maintain the best traction and control so any other adverse or positive effects are also valid.

Personally, I would reduce the spring preload by a whole lot, but not convinced that would yield the best result.

 

tech forum...

and the answer is Thermosman

i have no idea and thought i would be a smart ass.

 

In a case like that, I would try to get the bike balanced. I don't think I would adjust the spring pre-load on the shock. It isn't really going to help the problem and would create other problems. I would actually take out rebound in the forks so the whole bike moves excessively fast in rebound. I would rather ride a balanced bike (even if it is jacked up) because it will be more predictable.

 

got my smarty remark out of the way.. so why o' why would you not fix the shock? i would tend to agree that a shock with little rebound damping, even with the adjuster all the way in, could have more issues if you added preload.. but reducing shock preload (to try and get around the issue at hand) creates more problems by changing the bike geometry. drops the rear, changes the attitude when on the gas, etc.

I'm not certain trying to balance the bike by backing the fork rebound, is gonna make things any better. You now just have a bike that is f-ed front and rear now.. get the friggin thing valved correctly and fixed if it's broke. Your life and the life of others could depend on it.

 

I assume you're asking this question as a quick fix trackside when the shock cannot be properly replaced or serviced right. Not because you are wanted to keep a blown out shock and try to put a band-aid on it?

 

If the shock is blown out I think it doesn't matter what spring is in it. It's just a spring (no damping) and will bounce / pogo no matter what.

 

agreed. pretty sure it will just be a matter of the current ride height at the time it tries to eject him. A spring rate is a spring rate.

 

LOL!For the best pogo effect extend ride height to maximum length, install stiffest spring possible and roll throttle on at extreme lean angle for maximum ejectability.

 

And if possible bleed all the pressurized nitrogen from the shock. Dave Moss demonstrated this in one of his old youtube vids. I think it might've been an old 916 with all the nitrogen pissed out from the shock. The back end flopped up and down like a fish out of water from just pressing down on it once.

 

Yes, clearly the best solution would be to fix the shock, but I was asking for opinions on what people think would be the better way to go between more preload, less, or keep the same sag as if the rebound was functioning just for the sake of conversation and out of curiosity.

Theoretically;
If you add preload the spring will return faster, but less distance.

If you reduce preload the spring will return more slowly but travel further.

So to reduce the pogo effect of having no rebound damping (say for the sake f argument the shock didn't come with that knob) which way would you go? Or what other adjustments could be made?

For example; put your weight forward going into a turn and as far back as possible past the apex.
Stuff like that

 

I ride a Grom and an FZ-09, so I know exactly what you're talking about. Preload seems to have little effect - either way, it's underdamped.

 

Yup, preload will affect geometry not the spring rate so it will still pogo.

 

You're thinking of how the spring works the wrong way dynamically under cornering loads and acceleration.

Also, as with most questions like this, there's a lot of information being left out. Is the spring the correct rate for application, rider and pace? (If you're bottoming the shock and packing it up, it won't really matter.) What bike? Is it a mini?

 

NO! It makes it stiffer! Stiffer, I tells ya! I don't need no stinking spring! You're just trying to sell me something! I'll just crank up the preload in the fork.

 

Smash the spring all the way down so it does almost nothing giving you no suspension. Wear a kidney belt and DON'T CRASH

 

You too?

 

I've killed more brain cells than I can count trying to explain to riders that more preload is not the solution to incorrect spring rate.

 

So basically you are riding a bike pre 80's or any of Yamaha's latest "standard" offerings, does this about sum up your dilemma.

Leave everything else alone and ride it as is if forced to, but I would much rather fix the problem given a choice. So I would neither add nor subtract spring preload

 

As much as that is correct, it would be better than nothing to add preload.

Agree, leave preload, add compression. at least you could slow the pogo in one direction.

The spring rate is the spring rate... Preload doesn't change that.