seb421

REAR SHOCK SPRINGS



i came about this trying to find out about my shock, i thought i had been sold a WP shock that was for a rider 170-175 kg in weight as that was what was stamped on the spring 170-175, thankfully Al pointed out to me that i was incorrect in thinking it was kg rating it was infact the Newton Force rating of the spring, so to anyone that has a got a shock second hand and doesn't know what spring is on it this may be of some use?

Springs may be marked up with a lb/in force number or a N/mm number

RT - Digital Product Search

Recommended Shock Spring Rate (for me 14 stone): 17.3 kg/mm (use closest available)

You can get the Newton force by multiplying the Mass and the Acceleration. F = m.a,

So in this case the Acceleration is the Gravity which is 9.8 m/s. and the Mass is the Spring rate given

The answer is F = 17.3kg X 9.8m/s = 169.54N

So ideal spring for me Solo would be 170N so very happy with the 170-175 spring,

To get a kg rate of a spring for a listed Newton force simply divide the Newton Force by Gravity

So
175N/mm / 9.8m/s = 17.8kg/mm
170N/mm / 9.8m/s = 17.3kg/mm

So what is a Spring Rate??? A Spring rate is the number of kg or Newton needed to move the spring by 1 mm (or inch if you use lb rating).

Here are some pre worked out spring rates for the rear shock for road use on a Firestorm

To work out what spring rate suits what rider weight you have to then factor in the shock linkage ratio, the weight of the bike, the weight distribution of the bike and the type of riding. Then you add the rider weight (in full riding gear). These are results calculated by the Racetech site, i have added the N/mm and lb/in data using conversion rates

Stock Rear Shock Spring Rate: 16.4 kg/mm = 160.8 N/mm = 918.3 lb/in

9 stones = 15.55 kg/mm = 152.3 N/mm = 870.7 lb/in
10 = 15.9 kg/mm = 155.8 N/mm = 890.3 lb/in
11 = 16.25 kg/mm = 159.2 N/mm = 909.9 lb/in
12 = 16.6 kg/mm = 162.8 N/mm = 929.5 lb/in
13 = 16.95 kg/mm = 166.1 N/mm = 949.1 lb/in
14 = 17.3 kg/mm = 169.5 N/mm = 968.7 lb/in
15 = 17.65 kg/mm = 172. 9N/mm = 988.3 lb/in
16 = 18 kg/mm = 176.4 N/mm = 1007.5 lb/in
17 = 18.35 kg/mm = 179.8 N/mm = 1027.5 lb/in
18 = 18.7 kg/mm = 183.2 N/mm = 1047.1 lb/in
19 = 19.05 kg/mm = 186.6 N/mm = 1066.7 lb/in
20 = 19.4 kg/mm = 190.1 N/mm = 1086.3 lb/in




FRONT FORK SPRINGS
(Standard Firestorm Forks)

Stock Fork Spring Rate: .585 kg/mm(stock) Very Soft and undersprung

9 Stone = 0.791 kg/mm = 7.75 N/mm = 44.29 lb/in
10 = 0.812 kg/mm = 7.96 N/mm = 45.46 lb/in
11 = 0.833 kg/mm = 8.16 N/mm = 46.64 lb/in
12 = 0.854 kg/mm = 8.37 N/mm = 47.82 lb/in
13 = 0.875 kg/mm = 8.58 N/mm = 48.99 lb/in
14 = 0.896 kg/mm = 8.78 N/mm = 50.17 lb/in
15 = 0.917 kg/mm = 8.99 N/mm = 51.34 lb/in
16 = 0.938 kg/mm = 9.19 N/mm = 52.52 lb/in
17 = 0.959 kg/mm = 9.40 N/mm = 53.70 lb/in
18 = 0.98 kg/mm = 9.61 N/mm = 54.87 lb/in
19 = 1.001 kg/mm = 9.81 N/mm = 56.05 lb/in
20 = 1.022 kg/mm = 10.02 N/mm = 57.22 lb/in

I will also work out the rates for CBR 929 / 954 forks fitted to a Storm and fill in shortly


Rider Weights (approx)


*Thanks to AMCQ46 for helping me with this as i was about to get rid of this shock had he not informed me of how springs are marked up