Spring Rates Database

Ralph

New member
I know this topic has been discussed before in previous threads as I have just done a search on spring rates and colour codes. The information gleaned so far has been very patchy and inconclusive. I like the idea proposed by I think it was Thanos, though I'm not too sure, that we start a database of front and rear springs and their specifications for rear wheel drive Peugeots.

The format could perhaps be as follows:

Year 1982
Model 505
Variant GR (Sedan/Estate)
Front or rear spring (f/r) Rear
Colours on spring (COS) Red Yellow Yellow
Free spring height (FSH) 419mm
Number of coils (NOC) 7
Coil diameter (CD) 15.5mm
Spring rate (SR) not calculated
Spring rate could be calculated by the formula provided by Thanos:

Spring rate in lbs/inch = 11500000 times the coil thickness in inches to the fourth power divided by the coil diameter in inches to the third power, divided by eight, divided by the number of active coils.

I could see this as being very useful for those who want to know what springs are on their car and what they could be upgraded to. This topic regularly surfaces on AF when members ask questions about modifying their car's suspension. All information will be usefull if enough of it was provided to building up the overall picture So if any of you have some springs up in you shed, grab your calipers and start measuring! Also have a look at what is fitted to your car, you can still get info on colour codes and coil diameter which will be helpful although free length and number of coils will be impossible to measure. Here's my contribution to start the ball rolling:

1982
505
GR Sed
Rear
COS Red Yellow Yellow
FSH 419
NOC 7
CD 15.5
SR not calculated (I'm still trying to figure out the formula provided)

1983
505
GR Sed
Rear
COS Yellow White
FSH not measured, on car
NOC not measured, on car
CD 15.8
SR not calculated

1985
505
GTi Sed
Rear
COS Red Red Yellow
FSH not measured, on car
NOC not measured, on car
CD 15.5
SR not calculated

1984
505
SR Sed
Rear
COS Red
FSH not measured, on car
NOC not measured, on car
CD 14.7
SR not calculated

If there is enough interest shown and the specs are posted, I'll collate them into a database and publish it here on AF for all to enjoy. I'll post more as time permits.

Cheers,

Matt.
 

Thanos

New member
I think this is a good idea, Matt, so here is my contribution:
The reason the formula is giving you trouble is that you are missing the coil diameter. For the 504's and 505's they are 122 mm rear, 150 mm front. Or since the formulas are in inches, 4.8 inches rear, 5.9 inches front. The coil (wire) thickness is what you have listed as coil diameter so I rudely made the changes below:
Ralph said:
The format could perhaps be as follows:

Year 1982
Model 505
Variant GR (Sedan/Estate)
Front or rear spring (f/r) Rear
Colours on spring (COS) Red Yellow Yellow
Free spring height (FSH) 419mm
Number of coils (NOC) 8
Coil diameter (CD) 122 mm
Coil (wire) thickness (CT) 15.5 mm
Spring rate (SR) ?

First we convert coil (wire) thickness to inches: 15.5 mm divided by 25.5 mm/inch equals 0.61 inches

Spring rate= 11500000X0.61X0.61X0.61X0.61/(divided by)8X8X4.8X4.8X4.8= 225 lbs/inch

Or you can use the great link PeterT provided above and come up with the same number with much less drama. (Thank you Peter for this and much more useful information.)

Matt, since you graciously offered to be the database administrator, this is what I would envision:

Develop separate excel spreadsheets for front and rear springs that will include all the constants (modulus and coil diameter) and the calculation formula (I can assist you there).
Then you will have to input the car model, spring color code, coil thickness in mm and number of active coils and the spring rate will be calculated automatically. We can even take this a step further and use the link PeterT has provided to predict ride heights for replacement springs. This will be very helpful to all. Consider the recent example with Chris (505 to the max) who is going through a suspension upgrade right now (Chris, I hope you do not mind being used as an example). By taking a look at the color code of his springs he would tap into the database and find out the existing rates. After measuring a coil thickness, coil diameter and counting the number of active coils, he could calculate rates for the replacement springs and expected ride height using the link PeterT provided, which would also be listed along with the spreadsheet. Chris had the advantage that someone else has used the same system so he knows what to expect, but with this information he would have been able to quantify the effect, especially since he is making significant changes to ride height and stiffness.

The spring rates can help all of us make informed decisions/choices regarding potential replacements. Trial and error spring choices can be time consuming and costly, especially considering the labor/cost in replacing rear 504/505 springs

Thanos
 
Last edited:

Ralph

New member
Thanks Thanos,

Feel free to make any changes you see fit. That was a bit of an oversight on my part, I was thinking wire thickness. Could you clarify what you mean by active coils and modulus please?

I'll have a go at doing a spreadsheet and post it up on my server which I am still trying to get going properly.

Hopefully there will be some interest in this and it will be of benefit to others.

Matt (Database Meister).
 

Thanos

New member
Ralph said:
Thanks Thanos,

Feel free to make any changes you see fit. That was a bit of an oversight on my part, I was thinking wire thickness. Could you clarify what you mean by active coils and modulus please?

I'll have a go at doing a spreadsheet and post it up on my server which I am still trying to get going properly.

Hopefully there will be some interest in this and it will be of benefit to others.

Matt (Database Meister).


Active coils is the number of coils in the spring that are free to move. Count the total number of turns (it does not have to be a whole number) and:

If the ends of the spring are not touching another coil, what you counted is the number of active coils.

If the ends are not touching another coil but are ground flat subtract 1/2 from what you counted if one end is ground, subtract 1 if both ends are ground.

If one end is touching another coil subtract 1 from what you counted, if both ends are touching another coil subtract 2. If the ends are touching another coil it does not matter if they are ground flat.

The modulus is a constant, in our case the 11500000 in the formula.

Your excel formula should look something like this:

Front spring rate= (wire thickness in mm divided by 25.4) to the fourth power, multiplied by 6655 and divided by the number of active coils

Rear spring rate= (wire thickness in mm divided by 25.4) to the fourth power, multiplied by 13000 and divided by the number of active coils

To raise a number to the fourth power, multiply it by itself three times: For example, 2 to the fourth power is 2x2x2x2= 16

Thanos
 

Ralph

New member
What 505 variant are these springs from? :confused: I know the answer as I removed them. Your help to get the database happening will be very much appreciated by all Peugeot enthusiasts.

505%20Springs_0222%20Resize.JPG

Matt (database meister)
 

Thanos

New member
Ralph said:
What 505 variant are these springs from? :confused: I know the answer as I removed them. Your help to get the database happening will be very much appreciated by all Peugeot enthusiasts.

505%20Springs_0222%20Resize.JPG

Matt (database meister)


Hey Matt, here is another one, from today's adventure:

1980 505 STi front springs, clearly not the original ones, 13.25 mm wire, 6.3 actice coils, one yellow, one green, works out to 85 lbs/inch. The markings on the rear springs were not distinguishable, but the rear springs were clearly were not matched to the fronts. The wire was 15.5 mm as for the standard late STi springs, but the springs had too many coils to be STi rears. As a result, the rear was too soft and the car understeered like a pig.

Thanos
 

Mike L

New member
1972 504 Ti

yr: 1972
model:504
Type: TI sedan
Front/Rear: Rear
Colours: Green Yellow (yellow green, depending on which way u read it)
Free standing height: 420mm
Number of coils: 10
Coil diamiter: 16 - 17mm
Spring Rate:????
 

Ralph

New member
Thanks for your contribution Mike. I've found that the colours start at the top and fade down towards the bottom.


Matt.
 

Uffee

New member
yr: 1983
model:504
Type: Diesel Pickup
Front/Rear: Front
Colours: indecipherable
Free standing height: 325mm
Number of coils: 6.5
Wire diameter: 13.75mm
Spring outer diameter: 143mm
Spring Rate: 145lb/in
 
Last edited:

boodek

New member
Nothing to add, except I love the way a 12-year-old thread is still active. That's why I am still part of FF since 25th July 2001 - nearly 17 years.
 
Top