 Torsion Bar Spring Rates |
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| joea9146 |
 Mar 10 2006, 09:22 PM
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#1
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Senior Member  Group: Members Posts: 663 Joined: 10-February 03 From: Denver, NC Member No.: 283 Region Association: None  |
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 ====================================================== > SIZE ( mm) SPRING RATE ( Lb/in) > 18.8 110 > 21 173 > 22 210 > 23 250 > 24 296 > 25 350 |
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| Sideways |
Mar 10 2006, 10:13 PM
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#2
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Member Group: Members Posts: 119 Joined: 18-October 05 From: Calgary, AB, Canada Member No.: 4,969 |
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. |
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| TimT |
Mar 10 2006, 10:17 PM
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#3
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retired Group: Members Posts: 4,033 Joined: 18-February 03 From: Wantagh, NY Member No.: 313 |
What??? you got some splainin to do Joe did you find some of the info at Instant-G? |
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| Aaron Cox |
Mar 10 2006, 10:18 PM
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#4
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
here is the instant G one...
http://instant-g.com/Data/911CoilConv.html |
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| Sideways |
Mar 10 2006, 10:31 PM
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#5
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Member Group: Members Posts: 119 Joined: 18-October 05 From: Calgary, AB, Canada Member No.: 4,969 |
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...... |
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| ArtechnikA |
Mar 10 2006, 10:48 PM
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#6
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
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... |
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| TimT |
Mar 10 2006, 10:53 PM
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#7
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retired Group: Members Posts: 4,033 Joined: 18-February 03 From: Wantagh, NY Member No.: 313 |
Occams razor
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) |
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| TimT |
Mar 10 2006, 10:55 PM
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#8
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retired Group: Members Posts: 4,033 Joined: 18-February 03 From: Wantagh, NY Member No.: 313 |
Ha!! Rich said it more succinctly than I
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| Sideways |
Mar 10 2006, 10:55 PM
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#9
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Member Group: Members Posts: 119 Joined: 18-October 05 From: Calgary, AB, Canada Member No.: 4,969 |
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) |
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| Aaron Cox |
Mar 10 2006, 10:58 PM
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#10
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
i love this place... latin prods, and spring rates in the same post (IMG:http://www.914world.com/bbs2/html/emoticons/tongue.gif)
i learn stuff everyday |
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| Sideways |
Mar 10 2006, 10:58 PM
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#11
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Member Group: Members Posts: 119 Joined: 18-October 05 From: Calgary, AB, Canada Member No.: 4,969 |
Wheel rate is also effected by any friction in the suspension, bushings etc, however your 935 suspension would be all but devoid of this..... |
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| Sideways |
Mar 10 2006, 11:02 PM
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#12
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Member Group: Members Posts: 119 Joined: 18-October 05 From: Calgary, AB, Canada Member No.: 4,969 |
Thanks for the latin lesson, based on this my first response should have read.
Both are correct. (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) |
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| TimT |
Mar 10 2006, 11:07 PM
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#13
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retired Group: Members Posts: 4,033 Joined: 18-February 03 From: Wantagh, NY Member No.: 313 |
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.. |
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| Sideways |
Mar 10 2006, 11:09 PM
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#14
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Member Group: Members Posts: 119 Joined: 18-October 05 From: Calgary, AB, Canada Member No.: 4,969 |
I'm just a dumb ass that cannot get my thoughts from my brain to my fingers...... (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) |
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| TimT |
Mar 10 2006, 11:10 PM
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#15
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retired Group: Members Posts: 4,033 Joined: 18-February 03 From: Wantagh, NY Member No.: 313 |
And Steven
Welcome to the club (IMG:http://www.914world.com/bbs2/html/emoticons/welcome.png) all is good.. we can all learn (IMG:http://www.914world.com/bbs2/html/emoticons/beer.gif) |
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| Sideways |
Mar 10 2006, 11:12 PM
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#16
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Member Group: Members Posts: 119 Joined: 18-October 05 From: Calgary, AB, Canada Member No.: 4,969 |
(IMG:http://www.914world.com/bbs2/html/emoticons/hijacked.gif) Self confessed....
Tim how do you like the Haltech systems, A friend of mine used to work fro them is Australia. (IMG:http://www.914world.com/bbs2/html/emoticons/hijacked.gif) Over... |
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| TimT |
Mar 10 2006, 11:18 PM
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#17
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retired Group: Members Posts: 4,033 Joined: 18-February 03 From: Wantagh, NY Member No.: 313 |
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 |
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| joea9146 |
Mar 11 2006, 08:47 AM
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#18
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Senior Member Group: Members Posts: 663 Joined: 10-February 03 From: Denver, NC Member No.: 283 Region Association: None |
OK.... so a front 21mm torsion Bar Has a spring rate of 240 lbs ???
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| ArtechnikA |
Mar 11 2006, 09:11 AM
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#19
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rich herzog Group: Members Posts: 7,390 Joined: 4-April 03 From: Salted Roads, PA Member No.: 513 Region Association: None |
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. |
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| Sideways |
Mar 11 2006, 09:35 AM
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#20
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Member Group: Members Posts: 119 Joined: 18-October 05 From: Calgary, AB, Canada Member No.: 4,969 |
You are correct..... |
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