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Benefits Of Stiffness


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No, I am not talking about love making, but motorcycle chassis ;)

 

There used to be an expression regarding motorcycle race bikes that said "as soft as possible, as hard necessary". In other words, suspension was supposed to be compliant and only just stiff enough to prevent wobbly handling.

 

The most extreme of this school was Helmut Dähne, who in the early to mid-70s softened the already rather soft BMWs so that they virtually floated down the road. He liked soft springs and fairly heavy damping.

 

But even racers like Spencer and Lawson and Rainey used fairly soft suspension settings, especially if you compare with what is used today. Current MotoGP bikes are so stiffly set up that you can see the bikes and riders being rattled over ripples.

 

So, what are the benefits? I would guess quicker, more direct steering as one. Another would be improved feel for what's going on between tyres and tarmac.

 

But I can also see disadvantages. For instance, I would expect less grip since the tyres at times will bounce instead of moving with the road surface. Also, I'd guess riders to tire sooner due to being rattled around. And visibility must be impaired at times when eyeballs are rattled in their sockets.

 

I presume they have found these stiff settings to be required today, but it would be interesting to learn more about why.

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I also heard somebody say it's to maintain chassis attutude during cornering - due to the enormous grip available, they can brake deeper and harder and also accelerate sooner and harder. And with soft suspension, the bike would not maintain its posture, but instead shift too much forward and rearward. Makes sense?

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Good question.

 

I recently dropped the air in my rear tire from 42 to 36 and took the pre-load from 4 down to 3. Boy--what a difference! The bike, even the seat, are way more comfortable now. Suddenly, I'm getting feedback from the tires when before, I was getting nothing. Before, no matter how relaxed my grip, I still just couldn't feel, heck, couldn't even hear the tires. I know that's weird, and maybe it's just something I'm noticing now, but suddenly I "hear" the tires gripping and biting just like I do with in my car. I got none of that before. So, for me, softer has been much better.

 

Of course, I'm not running a 12 psi race tire on the back either.

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Cadalora also connected soft with feel, whereas Roberts Sr? (forget who the other was) combined feel with harsh; ideally, he's have short clipons fitted directly to the front axle. So there are individual differences, no doubt. Personally, I dislike the lack of comfort that comes from stiff suspension and tyres, but they give me confidence to push - I disliky mushy.

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Im in the soft camp too.

 

 

 

 

the roads around where i commute are really harsh IMHO...

 

 

 

 

well if i have the budget, i'd get some shocks that can be tuned externally for Hi/LO damping thou.

 

 

 

 

too bad too easily stolen and out of my comfort range.

 

 

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  • 2 weeks later...

Cobie is right about tire tech, that is main reason for the very stiff motogp bikes, you simply need to load up the tires to make them work.

 

But allout stiffness isn't good, hence all the talk about flexible engine front mounts and swingarms, maybe that is also the reason why Rossi (and Stoner had) are having trouble with frontend feel on the ducati, too much stiffness in the carbon frame.

 

Ronni

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Good question.

 

I recently dropped the air in my rear tire from 42 to 36 and took the pre-load from 4 down to 3. Boy--what a difference! The bike, even the seat, are way more comfortable now. Suddenly, I'm getting feedback from the tires when before, I was getting nothing. Before, no matter how relaxed my grip, I still just couldn't feel, heck, couldn't even hear the tires. I know that's weird, and maybe it's just something I'm noticing now, but suddenly I "hear" the tires gripping and biting just like I do with in my car. I got none of that before. So, for me, softer has been much better.

 

Of course, I'm not running a 12 psi race tire on the back either.

 

Depending on the bike and rider, that's still pretty high. About the highest we go on street tires is 33 front, 33 rear.

 

I'm going off the avatar photo, as it would be higher PSI with the big/heavy bikes, but not for most sport bikes. See Steve's tire threads for the real scoop on that though.

 

CF

 

CF

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