Hi Guys,

I've trawled through the search and couldn't find anything to help...

How do I calculate spring rates? Since I've dropped the heavier S2000 lump/gearbox into my car, it sits a bit lower and now I think the springs might be a bit weedy.

I can measure the axle weight at a friends MOT station, but was trying to figure out what the best way of calculating my spring requirements would be.

Ideally, I'd like an excel sheet, where I plumb in the numbers, but if somebody has the manual equasion, I'll do it manually

Cheers,

Murray

I'd ring Procomp and let Matt figure it out

He'll then sort you some springs out.

Mind that the spring rate required will be quite a bit more than the axle weight since the angle the shockers are at will reduce their effectiveness.

Have a look here. This is how I proceed to get an idea for first testing.

http://www.locostbuilders.co.uk/viewthread.php?tid=84991&page=2

quote:

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Originally posted by MikeCapon
Have a look here. This is how I proceed to get an idea for first testing.

http://www.locostbuilders.co.uk/viewthread.php?tid=84991&page=2

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try this then

http://www.locostbuilders.co.uk/viewthread.php?tid=84991

steve

Is that any help Murray? Or should I knock up an Excel spreadsheet?

I'd be very VERY interested in an excel spreadsheet Mike! I am considering building a Locost next and would love to do some research into how to make it handle as best it possibly could and therefore make better informed decisions!
Have sent you U2U!
Steve

quote:

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Originally posted by MikeCapon
Is that any help Murray? Or should I knock up an Excel spreadsheet?

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Thanks - I'll take a look

What about this little baby of a site


Springs and things

How do I post an Excel spreadsheet then?

add another post and at the bottom, there should be an attachment section.

browse for the file and add it.

post it

we'll then be able to download it.
tom

Posted for Mike!

Thanks very much!!!

Steve

Thanks Tom,

Has that worked?

Mike,

You're a diamond! If at stoneleigh, let me know and I'll buy you a beer

M

Do wheel frequencies not count in the equations these days?

THE single biggest factor in comfort and handling. Or used to be in the good old days!

Cheers,
Syd.

[Edited on 1/4/08 by Syd Bridge]

I use what i beleive to be a much simpler and more accurate method and all you need is a couple of measurements ,the angle of the shock, and the weights that the wheel will see
you will need meas, 1 the distance from bottom A arm chassis pickup to bottom shock mount= meas A
the bottom A arm chassis mount to center of tyre =Meas B
to get the Motion ratio at the tyre [A/B]2
example if A = 14 and B=18 then the formula will be
[14/18]2 =.61
.61 is the motion ratio at the wheel so divide .61 into the weight at the wheel to detirmine the amount the spring is holding up.

the other little thing you need is the angle of the shock to get an accurate correction factor, and they are
shock angle correction factor
10 deg .96
15 deg .93
20 deg .88
25 deg .82
30 deg .75
35 deg .66
40 deg .59
45 deg .50
the greater the angle the heavier the spring needed, so if for a verticaly mounted shock you need a 200lb spring.
if you lay the shock at 30deg you will need a 266lb spring
ie, 200/.75 =266lb
a reasonably good guide for spring rates for a road track car are

spring 250lb= 800-1200lbs
spring 350lb= 200-1500lbs
spring 450lb= 1500-2000 lbs
spring 550lb= 2000-2400lbs
spring 650lb= 2400lbs pluss

the second figure being the total load on the front wheels

so for a road going clubby with around 350kg on the front with a shock angle of 35deg i'd run some where between 200-300lb springs depending on wether road or track

I am no Einstein or math genious, but i have used this method for many years and have found it both simple and accurate
hope it helps in some way
cheers Kaspa





[Edited on 2/4/08 by Kaspa]

Good thread! - pity its stuck in bobywork?

quote:

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Do wheel frequencies not count in the equations these days?

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rates

Hi Syd,

Yes, you're right. The classic method does involve the wheel frequency calculation and I have used this in the past, although, I have to add, without much success.

The point is that you need to choose the frequency and hence spring rate. Using supposed "correct" frequencies often gave me ridiculous results.

Any method will have its weaknesses and proper testing is the real solution. In having to develop shocks for many different vehicles as rapidly as possible, I came up with "my" solution to find a starting point for testing.

For the case in question it seemed to me to be the most appropriate method.

Mike

In my work, the only definitive reference is frequencies, and they are really the only way to see which direction you are going. Then driver 'feel' comes into play.

Maybe bikes are that much different. I s'pose the much lighter weight must negate a lot of what car technology relies on.

Cheers,
Syd.

The trouble with trying to sort out a wheel frequency is, has anybody tried to bounce a clubby with coil overs with the shock removed, Mmmmmmm
Kaspa