Searched around and found this : But which one is correct ?

Front Rates
Torsion Kw (lb/in) Ks (lb/in)
Dia (mm) (Wheel) (Spring)
16 77 90
17 97 112
18 122 138
18.5 137 154
19 152 170
20 187 207
21 227 249
22 273 298
23 327 355


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> SIZE ( mm) SPRING RATE ( Lb/in)
> 18.8 110
> 21 173
> 22 210
> 23 250
> 24 296
> 25 350

They are both correct, one is for the front end the other rear of a 911.

The chart for the front lists both Wheel rate and actual bar rate. The spring rate is different at the wheel due to basic leverage.

QUOTE

The chart for the front lists both Wheel rate and actual bar rate. The spring rate is different at the wheel due to basic leverage

What??? you got some splainin to do

Joe did you find some of the info at Instant-G?

here is the instant G one...
http://instant-g.com/Data/911CoilConv.html

QUOTE (TimT @ Mar 10 2006, 09:17 PM)

QUOTE The chart for the front lists both Wheel rate and actual bar rate. The spring rate is different at the wheel due to basic leverage What??? you got some splainin to do Joe did you find some of the info at Instant-G?

When a bar, coil spring etc is manufactured it has a certain rate, the spring rate. #200 for eg.

The wheel rate is measured at or around the hub of the wheel (It s the spring rate the wheel 'see's').

Ie leverage comes into play, generally the wheel rate is lower that spring rate because the wheel is attached to the spring via a lever (the A arm) the difference between spring and wheel rate depends on the location of the spring and the length of the lever (among other things).

In the case of a 914/911 the spring is at the piviot point of the arm and the lever is the lengthof the arm from the bushes to the plane of the hub.

Does this help, this is very simplified......

QUOTE (Sideways @ Mar 11 2006, 12:31 AM)

Does this help, this is very simplified......

it doesn't help me understand why a spring would have a different rate if it's at the rear rather than the front, if that's what you mean.

wheel rate, sure, but that wasn't the question...

Occams razor

QUOTE

Does this help, this is very simplified...

actually it doesnt help a bit..

When I buy 600# spring for our 935... Im buying a 600# spring..

Im well aware of spring rates, K values etc.. I know about the ratios that delta "x" will impart to the spring/torsion bar etc..

wheel rate and spring rate are intimately related.. as they will be

but one thing in the relationship is constant... the spring rate..

(unless of course it is a spring system made from variable rate springs)

Ha!! Rich said it more succinctly than I

QUOTE (ArtechnikA @ Mar 10 2006, 09:48 PM)

QUOTE (Sideways @ Mar 11 2006, 12:31 AM) Does this help, this is very simplified...... it doesn't help me understand why a spring would have a different rate if it's at the rear rather than the front, if that's what you mean. wheel rate, sure, but that wasn't the question...

Sorry, I should have separated that sentence, the wheel rate comment was separate to the front and rear torsion bar piece.

The torsion bars are a different length front to rear hence the different rate for the same thickness bar. (rear bars are longer)

QUOTE (TimT @ Mar 10 2006, 09:53 PM)

Occams razor QUOTE Does this help, this is very simplified... actually it doesnt help a bit.. When I buy 600# spring for our 935... Im buying a 600# spring.. Im well aware of spring rates, K values etc.. I know about the ratios that delta "x" will impart to the spring/torsion bar etc.. wheel rate and spring rate are intimately related.. as they will be but one thing in the relationship is constant... the spring rate.. (unless of course it is a spring system made from variable rate springs)

i love this place... latin prods, and spring rates in the same post

QUOTE

In its simplest form, Occam's Razor states that one should not make more assumptions than needed.

i learn stuff everyday

QUOTE (TimT @ Mar 10 2006, 09:53 PM)

Occams razor QUOTE Does this help, this is very simplified... actually it doesnt help a bit.. When I buy 600# spring for our 935... Im buying a 600# spring.. Im well aware of spring rates, K values etc.. I know about the ratios that delta "x" will impart to the spring/torsion bar etc.. wheel rate and spring rate are intimately related.. as they will be but one thing in the relationship is constant... the spring rate.. (unless of course it is a spring system made from variable rate springs)

Wheel rate is also effected by any friction in the suspension, bushings etc, however your 935 suspension would be all but devoid of this.....

Thanks for the latin lesson, based on this my first response should have read.

Both are correct.

QUOTE

however your 935 suspension would be all but devoid of this.....

there is friction.. not much though

Aaron, Occams razor is a concept to keep in mind!! its good stuff..

Im an engineer that lives in the KISS... environment..

QUOTE (TimT @ Mar 10 2006, 10:07 PM)

QUOTE however your 935 suspension would be all but devoid of this..... there is friction.. not much though Aaron, Occams razor is a concept to keep in mind!! its good stuff.. Im an engineer that lives in the KISS... environment..

I'm just a dumb ass that cannot get my thoughts from my brain to my fingers......

And Steven

Welcome to the club



all is good.. we can all learn

Self confessed....

Tim how do you like the Haltech systems, A friend of mine used to work fro them is Australia.

Over...

Haltech is good.. user friendly.. easy to tune...

at least from my experience.. we have a bunch of cars out there running Haltech.. no problems that I know of

OK.... so a front 21mm torsion Bar Has a spring rate of 240 lbs ???

QUOTE (Sideways @ Mar 11 2006, 12:55 AM)

The torsion bars are a different length front to rear hence the different rate for the same thickness bar. (rear bars are longer)

good point. you are correct.

i was misdirected because i've never seen a 911 rear bar as small as even a very large front bar. but a quick look at the parts list shows that SWB cars had 22 and 23 mm rear bars and there are (now) 23mm+ fronts, so it is possible.

QUOTE (joea9146 @ Mar 11 2006, 07:47 AM)

OK.... so a front 21mm torsion Bar Has a spring rate of 240 lbs ???

You are correct.....

QUOTE (TimT @ Mar 10 2006, 09:07 PM)

Im an engineer that lives in the KISS... environment..

No Way. I work with bunch of ME's EE's and a Physicst (sp) the further up the food chain you got the more difficult it is to explain how to tie your shoe.

Somedays I feel like a feeder gold fish in a koi pond. But when hits the fan I can show them how to turn the fan off.