500 twin forks

[Fitz]

Has anyone got a set of fork springs handy that they could measure the free length of

The manual states 400mm but I have just ordered some replacements and the supplier reckons 500mm length

This message dated 1/4/2016 9am UK time

 

[KERMIT1200]

Fitz,
Springs 400mm
Pre load tube 65mm

Andy

 

[Fitz]

Cheers Andy, the springs I found are supposed to be progressive type heavier load than standard

I noticed that on a lot of pictures I have under braking and cornering the front end is very low compared to others such as Austen, Robin and the like, I am a big guy so I expected to need to  uprate the front end

I had the forks modified to give me full compression and rebound damping but I thought changing the springs that are probably 35 years old would be a good idea especially as I am big. I found marks on the front mudguard where the fairing had touched it, I have pictures from Oulton that look fairly serious but after tweaking the compression adjuster for Donington testing it does not look so bad, I can see some dirt on the fork leg of one picture that shows the amount of travel I am using and that look reasonable. I am using a fairing and bracket that I developed myself so not the standard Barca fairing which does nothing as far as I could see

The bike handles OK but I dont want to just try and use hydraulics to handle a sagging front end, I dont mind tweaking the pre load on the springs by adding spacers

 

[Vince]

I havent hear any suspension types recommend muiltirate springs, its hard enough sorting cartridge damping without adding spring rates that change with travel used.Have you added a cable tie to the fork,that will give you accurate data on sag and travel used. One of the issues finding fork springs for the corpulent is the ones Race Tech use max out at 0.95kgs/mm.Thats Eibock, and they need to fit inside and that limits whats about as well.That kinda shocked me when I was told that. The Race Tech website has a spring and settings finda thats work a look,probably wont have your bike but maybe the Laverda or Bevel Ducati section might work for you.They defiantly have a How to manual for Suspension tuning thats a great referance

 

[sfcpiet]

Wouldn't bother with any aftermarket dual-rate springs.  The "dual-ratedness"  is usually negligible, so virtually useless.  Often pure sales hype.

Fork springs are easy to tweak, especially for racing applications where long travel is not needed and tracks are smooth as billiard tables.  Cut down the existing springs... spring rate and travel are directly proportional to any alterations, ie, halving the spring doubles rate, halves possible travel. Add a longer spacer to take up the missing bit of spring and to adjust pre-load.  Find out the current spring rate, have a good think, use a bit of common sense and go from there.

Gutekunst Federn, https://www.federnshop.com/de/ have a nifty spring calculator on their site, german only unfortunately.  Bound to be something similar to be found in your preferred lingo.

I've "made" my own springs for a couple of my bikes for which I could not find dedicated items.  Gutekunst offer metre-long pieces in many rates and sizes, good for a great deal of experimenting.  The maths are simple and no great special tools required.  An angle grinder with cutting disc, a gas blow torch to bend the spring end windings and a grinder to square them off.

piet

 

[Fitz]

Hi Piet, the springs I am looking at are from a German manufacturer called Pamoto, the item is on Ebay as follows or if you just search for Laverda fork springs

Rechnung f?r Artikel Progressive Fork Springs LAVERDA SF500 35mm Marocchi Artikelnummer: 400176290034

I have learned quite a bit about these bikes over the last couple of years but had not heard of an SF500 so I searched the web and found it was just an early 500 twin. I looked around the pictures I found and the forks just look like standard Marzocchi 35mm types, I cant imagine why the manufacturer says they are 500mm long when the manual and Andy tell me 400mm

 

[tobster]

Hi Fitz, I can confirm that the fork springs in my 500 are indeed 400mm long (mine are actually 395 and 398mm). I have increased the spacer tube length to reduce the static sag. I too have never found progressive springs much good, whoever they have been made by.