Soft versus stiff suspension?

[SuziGSX250boy]

I've just gotten into bikes and am restoring an old Suzi 250. Question: what difference does it make to handling, cornering, braking, if I have a soft suspension on the rear or a stiffer suspension?
I've just recond the front forks and they have stiffened up quite noticably but now I find bumps are more 'shocking' than before when front end was softer.
For extra insight I am 6 foot and 122 kgs with my gear on and the suspension hasn't bottomed out more than once or twice.

[Corse1]

Oh Boy its not as simple as soft or hard. Its a combination of spring preload, compression damping and rebound damping.

If I set my suspension on the Duc to be as hard as the triumph it still won't jump all over the road like the speed triple will.

You may have a harder spring in one but a larger orifice for the oil to flow thereby making it easier for the suspension to move even though the spring is stiffer compared to another.

Stiffer suspension usually works better if you ride a bike hard or for racing purposes and a softer suspension would be more compliant for touring.

Compression damping can be dialed up on the front to reduce dive when braking. It really comes down to setting suspension up from the start for your weight. Setting static sag and comparing that to loaded sag will identify if springs are rated for your weight and then it goes from there.

I can't imagine you would be wanting to race an old 250 so you need to decide what the bike is being used for.

Now someone chime in and say that I am talikning a load of Crap (which I don't mind) or that there are posts on this site regarding suspension setup that should tell you more if you search.

I am Officially OUT OF MY DEPTH. :yes:

[AllanB]

When out in public, I like to keep my front fork soft. But in private when I'm really giving it a thrashing I find a stiff front fork is best .......... :sweatdrop

[White trash]

Oh Boy its not as simple as soft or hard. Its a combination of spring preload, compression damping and rebound damping.

If I set my suspension on the Duc to be as hard as the triumph it still won't jump all over the road like the speed triple will.

You may have a harder spring in one but a larger orifice for the oil to flow thereby making it easier for the suspension to move even though the spring is stiffer compared to another.

Stiffer suspension usually works better if you ride a bike hard or for racing purposes and a softer suspension would be more compliant for touring.

Compression damping can be dialed up on the front to reduce dive when braking. It really comes down to setting suspension up from the start for your weight. Setting static sag and comparing that to loaded sag will identify if springs are rated for your weight and then it goes from there.

I can't imagine you would be wanting to race an old 250 so you need to decide what the bike is being used for.

Now someone chime in and say that I am talikning a load of Crap (which I don't mind) or that there are posts on this site regarding suspension setup that should tell you more if you search.

I am Officially OUT OF MY DEPTH. :yes:
OK. You're talikning a lot of crap. (Whatever that is)

[KiwiGs]

This is what I do for the road.
I am not a racer or an expert but this works for *me*

First set the Static sag:
For street purposes, front sag should generally be between 30 and 35mm, and rear sag between 25 and 30mm. Don't vary from these numbers if you're heavier or lighter--that's the whole idea of measuring sag while you are on the bike. An easy way to check if your shock spring rate is in the ballpark is to measure the rear "free" sag, that is, the sag without your weight on the bike. This number should be between 0 and 5mm--with the bike off its stand and on its own, you should be able to lift the rear end just slightly and top out the suspension. If your bike is topped out at rest, you need a stiffer spring, because you have got a lot of preload dialed in to achieve the correct static sag. Alternately, if your bike has a lot of free sag (you can lift the rear a bunch before it tops out), you need a softer spring.

Compression damping can be initially set as follows:
It is difficult to set compression damping without riding your motorcycle and feeling how its suspension works. Start with the compression adjusters in the middle of their adjustment range, and take your bike for a spin. Working with the front and rear individually, soften the damping adjuster, and try your bike again over the same road. Is your handling better? Worse? The same? Try again, this time with the damping stiffer than what you started with. Continue experimenting, making adjustments accordingly.

Rebound damping can be initially set as follows:
With the sag properly set and the bike at rest and off its stand, firmly push on the triple clamp (don't hold on the brake or push the handlebar) or seat. When you let go, the suspension should rebound quickly to its original position--but not beyond. If it takes more than approximately one second for the suspension to return to position, less rebound damping is needed. If the fork or shock over-extends past its free sag, and then compresses again, more rebound damping is required. Street riding entails many different pavement characteristics, and the road is generally bumpy compared to a racetrack, so it's better to err on the soft side if you are unsure. This will also give you the added benefit of a smooth ride for daily use; you can always dial in a tad more rebound when you get to your favorite road where the surface is more of a known quantity.

One final check--with your bike off its stands, place your hands near the rear of the tank, and push down. A well-balanced setup will have both ends of your bike compressing and returning at approximately the same rate with this push. If the front compresses or rebounds different than the rear, attempt to match them, keeping within the parameters established individually.

[vifferman]

I've just recond the front forks and they have stiffened up quite noticably but now I find bumps are more 'shocking' than before when front end was softer.
Exactly what does "just recond" mean?
It could well be something as simple as something not lining up, or crud in one of the damper's orifices, or overfilling with oil that's making the front end more 'shocking'.
Unless of course, you've put much stiffer springs in.

I put new stiffer springs in my bike a while back (0.95 kg.mm straight wound springs, vs. 0/74kg/mm progressives) and heavier oil to compensate for excessive bounciness in the front. The nett result was the bike cornered brilliantly, but over bumps and ripples was tiring to ride, as the action was too harsh.
I spent a not inconsiderable sum having Racetech dampers, new seals and bushes fitted, and extra slippery baby lesbian afghani fur seal penguin whale oil, and the suspension was brilliant, but still a bit harsh. So, I spent another (modest) sum on 0.90 Ohlin springs, more oil, and some tweaking of the damping (the latter was free of charge). Now my suspension is compliant, almost plush, and the bike is nicer to ride. However, the steering isn't quite as precise (it's gone from seemingly scalpel-like to more of a sharp paring knife precision).

While it was rideable with the wrong springs and crap damping, and with the wrong springs and great damping, and reasonably safe, and better than stock in many ways, it's now more betterer, and I'm not being exercised by the bumps. It would've been fine on the track, and was fine on the motorway and round town, but between 80 and 100 km/h on 'B' roads, it was crap. Over 100km/h I guess it was OK :whistle:.

So... to answer your question, ideally what you need is suspension that is stiffly sprung enough for your weight and the kind of riding you do, and appropriately damped for the springing and for the roads you ride. If it's too soft, the handling will suffer (it may tend to run wide turning into corners, and/or coming out of them), and if it's too firm, it will handle better up to a point, except if it's so stiffly sprung and/or damped that the tyres aren't maintaining contact with the road, or it's affecting the steering.

[dipshit]

For my street riding I simply go by this...

Too hard is getting a thump and launching over any slight bumps and unsettling the bike and feeling like the bike is only skimming across the top of the road surface.

Too soft is a feeling of wallowing and pitching every time you go over a slump or rise in the road or make a throttle or brake input.

Somewhere between these two is where I like to be.

Of course it can be as much about damping control as it is about spring rates.

[CookMySock]

and then theres two different types of damping, one to damp the bike from ramping the springs up and down slowly AKA "wallowing" - this is called "slow speed damping" because the damper is moving at a slow speed. Then theres the damping that restricts movement when the wheel hits a square-edged bump, called high-speed damping, as the damper is moving at a high speed.

The balance is something like, enough slow speed damping to keep the bike and suspension from getting why out of whack on undulating surfaces and when braking or cornering hard, and the right amount of high-speed damping so the suspension doesn't transmit the forces directly to the bike when hitting some bump hard and get all out of control.

Steve

[Robert Taylor]

Those who have preceded this post have all by and large been on the right track.

But to throw in another thought. If the suspension is too soft it can feel too hard, because it is riding low in its stroke and precompressing the springs too much. So very often you make the suspension firmer to make it feel softer.
There is a fine widow of settings where everything works properly and it must be individualised to every rider.
If the spring rates are too soft ( for example ) no amount of extra preloading is going to alter the fact they are still softly rated springs. Overpreloaded springs will give a harsh ride but still blow through their stroke when riding over abrupt obstacles. Firmer springs appropriate for your height and weight will require much less preload to achieve sensible ride height figures. They will actually be more compliant at the top of the stroke but will provide much better pitch and square edge bump control.
And then theres damping, but I dont want to be up all night typing....

[retro asian]

If the suspension is too soft it can feel too hard, because it is riding low in its stroke and precompressing the springs too much. So very often you make the suspension firmer to make it feel softer.


I pretty much experienced this with my cruiser. Previous owner had the rear shock set at 2 out of 7 (1 is softest), going around corners it felt like the rear wheel was drifting. Going over bumps, my pillion's ass was flying off the seat.

I now have the rear set to 5 out of 7, and the bike is noticeably higher. It rides like a totally different beast now, I feel more stable in corners and going over bumps feels much better than before.

[F5 Dave]

That's not really what he was saying, . . .

Correct ride height through preload will help, but a band aid won't help internal bleeding.