Ducati Sporting Club UK > DesmoDue Race Series > DesmoDue - General Questions and Chat > FAO Tonio600, Fork spacer

[Paul James]

Originally Posted by skidlids

Trouble is paul unless you are prepaired to experiment and invest in several sets of springs to find what will work for you on each bike, you are better asking somebody that has done it. people like Maxton, Dave Parkinson, KAIS, K-Tech, etc i always used Justin at WPS until he got snapped up by Red Bull, but when it came to sorting one off specials I learnt to do it myself.
Tonio currenlty runs the standard progressive spring that he doesn't seem to be happy with and therefore wants a change. He has been recommended a couple of different options. I know his budget for DD is tight and therefore he doesn't want to waste money on the wrong springs so he is trying to understand how the options differ.
personnally I try not to race with anything other than single rate fork springs hence me recommending the Ohlins Option, No doubt these springs can be supplied in different rates and that will be down to how you like your bike setup (front/rear weight bias) and your body weight. As Tonio looks to be about the same weight as me I would suggest trying 0.85Kg/mm but its his money and therefore his choice.

I agree the Shear Modulas of the steels used to form springs varies over a range and I settled on a fixed value between the upper and lower figures to use in my equations and therefore my calculations have always been an approximation close to what is required, but as my spring supplier provides me with rear shock springs in 25lb/In steps then I usually go for the one closest to my calculation and at just over £15 a sping having to buy a second after testing the first and deciding i need slightly harder or softer is no big deal after spending £6k to £8k on building a one off special or a personalised Harris Magnum. Its always harder when you start with thin air and I have learnt to always go for a shocck with as long as stroke as can fit in the gap and get the linkage to go through a curve as linear as possible.
The linkage and shock that Harris provided for my Magnum 4 was awful, the ratio went from 2:1 to 2.5:1 and then the shock didn't have enough Stroke to cope with it. As mine was one of the first Magnum 4s later ones came with a Ohlins shock tailored to suit them and a rocker that only gave a ratio range of 2:1 to 2.1:1, Dallas had one of these later ones and it handled a lot better at speed than the early one I had, although over time i did get mine sorted

Agree with all of that, was just trying to explain a bit of the basic theory for anyone interested really. Not trying to derail your help Kev

[NBs996]

Hey, keep talking chaps... I'm learning!

[Paul James]

Originally Posted by NBs996

Hey, keep talking chaps... I'm learning!

Have a gander at this if you are bored at work then

http://www.tonyfoale.com/Articles/Springs/Springs.htm

[Tonio600]

OH MY GOD

Guys, I really really do appreciate your help, BUT... I didn't understand much of your answers, from you both You must have forgotten who you were talking to haven't you?

Kev got it right on the fact I'm after the cheapest solution possible. And for the moment, the cheapest solution is the 2 Ohlins springs monorate 8.5kg which Zimbo can sell me (at a very good price). BUT, those springs are 260mm length free, which is 20mm shorter than the rubbish standard ones and so my concern is: "is that an issue?"

I got a reply from Hagon, they can provide me with progressive springs (I think I'd prefer some monorate ones anyway) for £60. Zimbo's cheaper

So my last question is, do I go for Zimbo's or not?

Thanks again for your help

[skidlids]

or try giving DSC member Mike Davies a call at Robsom Racing and see what he can do, he sells both Ohlins and slightly cheaper K-Tech springs.

http://www.robsomracing.co.uk/

[skidlids]

Originally Posted by Paul James

Have a gander at this if you are bored at work then

http://www.tonyfoale.com/Articles/Springs/Springs.htm

Had his book for about 20 years, if i'm not mistaken his equation for calculating which sping is required doesn't work out, its either the Tony Foale (Quasar Yuk) book or Robinson's one on Chassis design.

Must admit I still prefer talking to Steve Harris about chassis design and still thinking about having a TT F2 frame off him one day