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Old 17-Aug-2006, 14:56
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andyb andyb is offline
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I disagree with the spring thing. The reason being, and this was explained to me by the previously quoted guru when i suggested my delicate fighting weight required a new spring......

"Imagine the forces acting on the rear end of the bike when you crack the throttle open...........some 120-150bhp twisting the rear end down"....yours and mine ...ahem 16 stonnes, doesnt really make that much difference!
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Old 17-Aug-2006, 17:22
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it's all in the compressin damping, I'm 17stone and I find for my S that the front needs +1 ie 1 harder than it says in the book and the rear is +2 harder,
The springs, the forks are round right up, the sag is out the window but it works for me if you want I could look for you,
The rear is a compromise for me, I go two up and dont want to take the rear shock off each time I ride it, so I have the spring wound up a bit to much for one up, theres no sag at all, it goes down about 5mm when I seat on it,
dont over do the rebound,
I hope this helps,
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  #13  
Old 17-Aug-2006, 20:16
Felix Felix is offline
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Originally Posted by andyb
"Imagine the forces acting on the rear end of the bike when you crack the throttle open...........some 120-150bhp twisting the rear end down"....yours and mine ...ahem 16 stonnes, doesnt really make that much difference!

Don't know who said that but that's utter ********. The spring is directly dependant on the load transfer under acceleration and the amount of static weight on the rear wheel. The only difference horsepower makes is the amount of load transferred to the rear. If the bike wheelies, for instance, the entire bike/rider weights is transferred to rear wheel.
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  #14  
Old 17-Aug-2006, 23:21
Gizmo Gizmo is offline
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Originally Posted by Felix
Don't know who said that but that's utter ********. The spring is directly dependant on the load transfer under acceleration and the amount of static weight on the rear wheel. The only difference horsepower makes is the amount of load transferred to the rear. If the bike wheelies, for instance, the entire bike/rider weights is transferred to rear wheel.

The forces acting on the swingarm are actually a pulling force from the the front chainwheel to the rear sprocket, the pivot position influences what effect they have on the suspension. this technique is used on Full sus mountain bikes to stop pedal induced bob, the pull counter acting the downward pressure, thats bit over simplified because i can't really explain exactly what happens for each pivot option but what important is where the pivot is in relation to sprocket, on a motorbike it gives squat typically on an mtb it counteracts squat but i agree horsepower just alters the amount of load.

spring weight is critical, if you are heavy you need heavier springs, compression damping ( depending upon adjustor range) has hardly any impact ( less than 10% of spring) rebound has more effect. adding clicks of compression is a placebo, i doubt many riders can actually tell 4 - 5 clicks and if the spring is way out its pointless anyway. K tech can explain all of this and adjust your shocks damping to match the spring, you may need shim changes if the spring alters by a large amount, a stiffer spring needs more rebound damping to control it and you may go beyond the adjustors range.

I added a tech article to upnorth on this based upon stuff i'd found it is quite complex but worth a read
http://www.ducati-upnorth.com/tech/suspensionspring.php
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  #15  
Old 17-Aug-2006, 23:26
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andyb andyb is offline
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Quote:
Originally Posted by Felix
Don't know who said that but that's utter ********. The spring is directly dependant on the load transfer under acceleration and the amount of static weight on the rear wheel. The only difference horsepower makes is the amount of load transferred to the rear. If the bike wheelies, for instance, the entire bike/rider weights is transferred to rear wheel.

Ill tell Mr H you said so...........
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  #16  
Old 17-Aug-2006, 23:32
Felix Felix is offline
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Yes, the pro or anti-squat forces do come into play, but on most sports bikes the are designed to cancel themselves out to a large extent by an appropriate swinging arm pivot location. The maximum contribution of additional load on the rear suspension due to squat forces are roughly 10%.

If you really want to confuse yourself, have a read of this book:Motorcycle Handling and Chassis Design. I've made extensive use of his design analysis software in my own bike project. Seems to work alright.
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  #17  
Old 12-Sep-2006, 20:40
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Been to see Colin todat at Oulton track day. Sorted suspension with taking settings away from Section 8 originaly used. Now better ride and no more pogoing. Great chap.
Thanks for the advice
G
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  #18  
Old 12-Sep-2006, 20:49
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khushy khushy is offline
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so what ARE your settings . . .

Front

compression (clicks out from fully in)
rebound (clicks out from fully in)
preload (turns from fully anit-clockwise)

and the same from the rear

Khushy
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  #19  
Old 12-Sep-2006, 21:47
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Originally Posted by khushy
so what ARE your settings . . .

Front

compression (clicks out from fully in)
rebound (clicks out from fully in)
preload (turns from fully anit-clockwise)

and the same from the rear

Khushy

Go pay yer £40 yer tight git! arnt you on a 749r?
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  #20  
Old 13-Sep-2006, 09:25
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khushy khushy is offline
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settings . . .

my settings are fine - thank you very much - just thought it might help everyone else.

2005 999s actually!
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