Fork springs

[Batfink]

Is there any way of working out what springs could be in a set of forks without a full deconstruction???

[Volvi]

they used to say when the busa first was released, the front springs were meant for little short arse nippons, in other words not strong enough for the average fast food westerner. i changed my springs years ago to 95kg. ones. guess its been ok. if I had to guess id say they come with 75-80kg springs.

[Shifu]

Yes there is.

[Batfink]

Yeah thanks Volvi.. Stock fork springs r slack nod I have heard ppl talking about putting in 1, 1.1, 1.2kg springs... Was wondering if I remember right and if yes... Wtf it means.. And can you check somehow what springs you got..

My 01 springs were adjusted to presprung tension of 8 and I still hit bottom on serious bumps...

My other springs were seen to hit close to bottom on only baddest bumps while presprung tension was on 1-2 .... While still having a good "bounce"

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Ooh shifu......
Please share your knowledge with a grandpa like me. Lol

[Shifu]

Ooh shifu......
Please share your knowledge with a grandpa like me. Lol

Take one leg of the fork out. Either one will do. Using soft jaws or two pieces of timber hold them in the vice vertically upside down (axle end at the top) by the outer tube. Put the front axle through and tighten the pinch bolts. That will serve as a good spot to hang the weight from. Make sure the forks are vertical at all time. Now measure the distance between the edge of the dust seal to the caliper mount casting as accurately as you can - vernier is good for this. Write down the result. Now hang some known weight on the axle. About 20 kg will do and dumbells are good for this but you myst know the weight accurately so weigh them beforehand. With the weight pressing on the fork measure the distance between the edge of the dust seal to the caliper mount casting same as before. Deduct this measurment from the value you got before. That is your deflection under the given force. Now you can easily calculate your spring rate. Lets say the fork compressed 18.5 mm under the weight of 21 kg so your spring rate is 21/18.5= 1.135 kg/mm or 11.1 N/mm (multiply kg/mm by 9.81 to get Newtons (N) /mm in which spring rate is usually designated). The result is not 100 % accurate as you will have some internal friction affecting your measurments but for all practical reasons it is accurate enough to determine if you have a correct spring in. For a 90 kg rider you need spring rate of about 10.5 N/mm. The OEM on GEN 2 is 8.5 N/mm so they have not improved from GEN 1 judging from what Volvi said.
Cheers.

[Batfink]

Ooh shifu......
Please share your knowledge with a grandpa like me. Lol

Take one leg of the fork out. Either one will do. Using soft jaws or two pieces of timber hold them in the vice vertically upside down (axle end at the top) by the outer tube. Put the front axle through and tighten the pinch bolts. That will serve as a good spot to hang the weight from. Make sure the forks are vertical at all time. Now measure the distance between the edge of the dust seal to the caliper mount casting as accurately as you can - vernier is good for this. Write down the result. Now hang some known weight on the axle. About 20 kg will do and dumbells are good for this but you myst know the weight accurately so weigh them beforehand. With the weight pressing on the fork measure the distance between the edge of the dust seal to the caliper mount casting same as before. Deduct this measurment from the value you got before. That is your deflection under the given force. Now you can easily calculate your spring rate. Lets say the fork compressed 18.5 mm under the weight of 21 kg so your spring rate is 21/18.5= 1.135 kg/mm or 11.1 N/mm (multiply kg/mm by 9.81 to get Newtons (N) /mm in which spring rate is usually designated). The result is not 100 % accurate as you will have some internal friction affecting your measurments but for all practical reasons it is accurate enough to determine if you have a correct spring in. For a 90 kg rider you need spring rate of about 10.5 N/mm. The OEM on GEN 2 is 8.5 N/mm so they have not improved from GEN 1 judging from what Volvi said.
Cheers.

Thanks Shifu... U got the sums I need!!! Now just end over