SPRING RATE CALCULATOR

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seb421
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SPRING RATE CALCULATOR

Post by seb421 »

REAR SHOCK SPRINGS

Image

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?

http://racetech.com/ProductSearch/2/Hon ... /1997-2005

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)

Code: Select all

9 Stone
57 Kg
126 lbs

10 Stone
63 kg
140 lbs

11 Stone
69 Kg
154 lbs

12 Stone
76 Kg
168 lbs

13 Stone
82 Kg
182 lbs

14 Stone
89 Kg
196 lbs

15 Stone
95 Kg
210 lbs

16 Stone
101 Kg
224 lbs

17 Stone
107 Kg
238 lbs

18 Stone
114 Kg
252 lbs

19 Stone
120 Kg
266 lbs

20 Stone
127 Kg
280 lbs

*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
Last edited by seb421 on Tue Nov 06, 2012 5:06 pm, edited 5 times in total.
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Re: SPRING RATE CALCULATOR

Post by VTRDark »

Another useful thread you have started mate :thumbup: It should be a sticky, well handy that, so bookmarked away.

So in which case there is no need for you replace your spring, maybe put the money towards it having it serviced. Replace the oil, re-pressurise and stuff. Turned out a good buy that that shock. Well done. :thumbup:

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Re: SPRING RATE CALCULATOR

Post by popkat »

For reference Standard firestorm spring rate is 16.4kg/mm or 916lbs/in, according to the racetec site.

Link below is the ohlins spring chart, helpful to id the ohlins numbers, the top blue line numbers equal the spring length, the side blue numbers are the spring rates marked next to them. This will allow you to understand the markings on an ohlins spring.
This chart also shows N/mm. KG/mm and lbs/in so you can cross reference all the different types of spring measurement.
Sebs WP in this thread has 170/175 so is in N/mm My Penske has a 950lb/in spring. converted over to KG/mm mine would have a 17KG/mm spring (I weigh 172lb) and Sebs probably an 18KG/mm (he weighs 196lb) but could get away with a 17KG spring

http://www.r1-forum.com/forums/attachme ... 1299450151


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seb421
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Re: SPRING RATE CALCULATOR

Post by seb421 »

popkat wrote:For reference Standard firestorm spring rate is 16.4kg/mm or 916lbs/in, according to the racetec site.

Link below is the ohlins spring chart, helpful to id the ohlins numbers, the top blue line numbers equal the spring length, the side blue numbers are the spring rates marked next to them. This will allow you to understand the markings on an ohlins spring.
This chart also shows N/mm. KG/mm and lbs/in so you can cross reference all the different types of spring measurement.
Sebs WP in this thread has 170/175 so is in N/mm My Penske has a 950lb/in spring. converted over to KG/mm mine would have a 17KG/mm spring (I weigh 172lb) and Sebs probably an 18KG/mm (he weighs 196lb) but could get away with a 17KG spring

http://www.r1-forum.com/forums/attachme ... 1299450151


Is that for use on an R1 with their Linkage shock ratio etc?
As that 18KG/mm spring on a storm according to race tech data would make me 16 Stones, i'm not 16 Stone with my gear on = 18 kg/mm = 176.4N
which says you at 12.2 stones (172 lbs) should be between 16.25kg/mm and 16.95kg/mm
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Re: SPRING RATE CALCULATOR

Post by seb421 »

cybercarl wrote:Another useful thread you have started mate :thumbup: It should be a sticky, well handy that, so bookmarked away.

So in which case there is no need for you replace your spring, maybe put the money towards it having it serviced. Replace the oil, re-pressurise and stuff. Turned out a good buy that that shock. Well done. :thumbup:

(:-})

Thanks buddy edited and added ib/ in data for those with shocks marked up with Ilbs ratings too

i'll stick it in the bike see how it rides, and if its sh1t ill get it serviced possibly by KAIS as they are only up the road from me :thumbup:
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Re: SPRING RATE CALCULATOR

Post by VTRDark »

I have some useful suspension pdf files for download. A Suspension 101 guide which contains 5 separate parts scanned from a magazine. Not by me, it's something I downloaded and found it interesting. And even more useful is a Road Race Suspension Setup Tips including how to set up static sag.

These have been uploaded to a fileserver for you to download. I have buried the files in a folder inside a zipped folder which has then been put into another folder that has been compressed in a rar format. This is password protected, the password is vtr1000. So make sure your compression software is capable of uncompressing rar files as well as zip files.

The password protected rar file is named 3747fuvncne.rar and the zip file inside is named ggfycytc.zip and the folder inside that contains the pdf's is named ggfycytc. Don't worry about the stupid names folder names, this is done for security reasons as I don't want the filehost to see the contents. Just drag the pdf file out and chuck the rest.

Download link
http://www.mediafire.com/?dgtih0yf9pk39f1
2.71mb
Password= vtr1000

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Re: SPRING RATE CALCULATOR

Post by popkat »

It's nothing to do with an R1 Seb, it's the Ohlins spring rate chart. A spring is a spring so to speak. I used to have the chart saved but lost it somehow ?, I googled it and the first link was off an R1 forum so i just copied it off there.

The racetech site says the spring for your weight is 17.3kg which is 170n but the spring in your picture shows 170-175 so is it a 17.3 OR AN 18KG ?, My post was suggesting you could use either depending on your preferance.

You say my spring should be 16.95kg for my weight, well my spring is 950lb which equates to 17kg. Spot on, I race bikes and prefer the rear to be fairly firm, if i was a different type of rider ie touring for example i might opt for a 16.5 or even 16kg spring for my bike. Suspension isn't an exact science it's about finding a ballpark and finding something that suits from there, if it was as easy as numbers then everyone could sort it out for themselves, hope this helps.
Last edited by popkat on Sun Nov 04, 2012 12:35 am, edited 2 times in total.
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Re: SPRING RATE CALCULATOR

Post by seb421 »

popkat wrote:It's nothing to do with an R1 Seb, it's the Ohlins spring rate chart. A spring is a spring so to speak. I used to have the chart saved but lost it somehow ?, I googled it and the first link was off an R1 forum so i just copied it off there.
Sorry i must have misread your post i read it as you was quoting R1 Ohlins spec Spring rates at me
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Re: SPRING RATE CALCULATOR

Post by Trainraider »

Ok,

Here is the dilemma. The original spring is hard as a rock.
Raceteck gives spring rate of 15,8kg/mm for my weight.
The closest spring available is 16.1kg/mm.
Original is 16.4kg/mm.
The lower option would be 15.2kg/mm

I know that I am light weight series driver so I find it really odd that going two steps down (15.2kg/mm) would mean that it is aimed for a driver for about 52kg (8 stones).

The roads here are bad (there is one pothole - the road network), so soft suspension would be appreciated.

But the change between 16.4 and 16.1 does not seem big enough. Because the suspension is REALLY hard. It was bearable only when I had saddlebags filled with tools and beer (20kg at minimum).

I would not want to buy wrong spring because I can only test it at summer (that is roughly 4 months away), and returning the spring at that point is not anymore an option.

Please advice :confused
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Re: SPRING RATE CALCULATOR

Post by popkat »

If thats all thats available and you only want to change the spring on the standard shock then I'd go with the 16.1kg spring, it'll be softer than standard for you, if you can set the static sag to around 15mm it should have the effect of feeling a bit softer than if it was set at 10mm for example. It's a compromise whatever you do as the rebound damping isn't great on the standard shock and the shock is also old.
There's no substitute for a replacement better shock, you can make the std one a bit better for you but i doubt you'll get it spot on, hope this helps.
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Re: SPRING RATE CALCULATOR

Post by AMCQ46 »

if you liked the performance of your std shock with an extra 20kg on the back, work our what % that is of your riding weight and that is a measure of how much over your ideal spec that spring is =x% too stiff

then buy a spring which is x% less stiff than the standard one.
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Re: SPRING RATE CALCULATOR

Post by seb421 »

Get a progressive spring benny swears by them!
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Re: SPRING RATE CALCULATOR

Post by lloydie »

Linear or progressive is down to personal choice and how you ride the bike .
For example
Progressive should be fitted it you like to just plod alone as you do if you use the bike to commute on .

Linear should be used if you like to ring it's neck as the linear gives a Constant Spring rate and much better feel .
And it easier to set up :-)

If you put progressive spring in the forks fix a progressive spring on the rear shock or it will feel wrong .
Which ever you fit do both ends so they match your weight and riding preference
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Re: SPRING RATE CALCULATOR

Post by Trainraider »

The stock spring was on the lowest possible pre-tension setting. So I don't think I can set the static sag any more.

That did neither have much of effect.

Of course new Öhlins would be great to have, but there is no hope to get that with my salary. So I have to go 1/4 price and start with things I can afford. And even small improvement is big improvement for the hard tail rock-sledge.

Well, the easiest would off course to eat a lot and drink even more to gain some mass, but that would demand some extra tuning to keep the performance level same... So spring change it is.

The problem with the racetech webpage is that it does not give "range" like öhlins springs have...

Would the softer spring be still ok, if I give a full pre-tension?

Edit: I am mostly driving solo, and I am a calm rider, so comfortable tops performance. I also assume that Racetech springs are linear which I would be happy with.
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