R12/R17 Suspension Set-Up and Corner Weights
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Thread: R12/R17 Suspension Set-Up and Corner Weights

  1. #1
    Fellow Frogger!
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    Default R12/R17 Suspension Set-Up and Corner Weights

    I'm researching my options for coilovers for my R12.

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    I've read through the Koni college thread from a few weeks ago, but I'm wondering if anyone has ever measured the corner weights on an R12 and would care to share the numbers so I can use them as a guide for calculating the required spring weights?

    Also, does anyone have a spare r12/15/17 front shock out of the car that can take some measurements for eye to top mount lengths (fully compressed and fully extended) and eye to top of body and extended shaft length, as well as the thread lengths on the top of the shaft and bottom of the body?

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    I’ve got some front koni’s I can take measurements of this weekend.

    Keen on how this goes.
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    COL
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    I can give you front and rear weights for an R12 wagon when I find where I wrote them down as I can't remember what they were.

    I can measure up a standard shock, as I should have some laying around here.

    I also have standard spring rates written down as well somewhere.

    I have done this to the front of my R12
    Renault R12/15/17 Lowering Front End
    Last edited by COL; 13th September 2019 at 08:23 PM.
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    Yay community to the rescue!

    I'll have a look over the junk. I feel I kept 1 x front and rear for moments like this.

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    Quote Originally Posted by COL View Post
    I can give you front and rear weights for an R12 wagon when I find where I wrote them down as I can't remember what they were.

    I can measure up a standard shock, as I should have some laying around here.

    I also have standard spring rates written down as well somewhere.

    I have done this to the front of my R12
    Renault R12/15/17 Lowering Front End
    Front and rear weights are as follow for my 1976 Renault R12 wagon.

    Total weight 1020 Kg
    Front weight 560 Kg
    Rear weight 460 Kg

    These weights were taken on my local weigh bridge that weighs large trucks. It weighs in 20 Kg increments.

    Will get the shock measurements over the weekend if time permits.
    Regards Col

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    COL
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    Found an old Munro shock out in the shed and have taken the following measurements.

    Overall extended 500 mm
    Overall retracted 415 mm
    Bottom pin to spring perch 150 mm
    Bottom pin size 16 x 1.5 mm x 16 mm long
    Top pin this is not a metric thread but is approximately 10 mm and is 18 mm long it has a shank that is 32 mm long where the top mount bushes sit.
    Regards Col

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    Thanks all for the input.

    Col,
    Is there any chance you can get a measurement of the total body length from bottom pin to top of the body above the spring perch?

    I'm looking at re-purposing some off the shelf coilovers and will require some spacers on either side of the bottom mount, and probably using an existing pillowball top mount to be bolted into the top spring perch. Currently either a rear Subaru WRX coilover (MY15+), or a 964 Porsche rear coilover seem to be the most likely candidates when using a very heavy spring rate and are half the price of having something made specifically for the 12.

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    COL
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    Quote Originally Posted by 3006882 View Post

    Col,
    Is there any chance you can get a measurement of the total body length from bottom pin to top of the body above the spring perch?

    That measurement is 310 mm
    Regards Col

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    This thread raised my interest as I was curious to see the corner weight figures for a 12. However, the figures discussed to date are not the actual corner weights. The corner weight figures are the readings you get when you place the car on a set of corner weight scales, one under each wheel. The four readings when added together give the total weight of the car. You can also see the actual weight distribution for corner to corner, side to side, front to rear.

    OK guys, what are those numbers ?

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    COL
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    Quote Originally Posted by Bustamif View Post
    This thread raised my interest as I was curious to see the corner weight figures for a 12. However, the figures discussed to date are not the actual corner weights. The corner weight figures are the readings you get when you place the car on a set of corner weight scales, one under each wheel. The four readings when added together give the total weight of the car. You can also see the actual weight distribution for corner to corner, side to side, front to rear.

    OK guys, what are those numbers ?
    The best I can do is try and get each wheel onto a public weigh bridge by parking the car cock eyed on the entry and exit of the weigh bridge as I don't have access to a set of wheel scales.
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    Regards Col

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    Have any of you modifiers of 12/15/17 suspension read what Renault reccommends for competition? They have plenty of suggestions but I cannot easily translate the French but if I was going down that path then I would at least read up on what strengthening and other mods they suggest. If I ever get back to my R12G replica maybe then I would have the incentive.

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    I would expect most of the modifications such as strengthening are for cars intended for rally competition. I have never seen anything about corner weights which is generally something for top end circuit or tarmac competition. Hence my interest to see some corner weight numbers.

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    Quote Originally Posted by Bustamif View Post
    I would expect most of the modifications such as strengthening are for cars intended for rally competition. I have never seen anything about corner weights which is generally something for top end circuit or tarmac competition. Hence my interest to see some corner weight numbers.
    I wouldn't be so sure about that....
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    OK JohnW, however I will remain sure until I see those mythical suggested corner weight numbers for an R17 or R12 Gordini.
    I now suspect they only exist in the land of unicorns.
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    Quote Originally Posted by COL View Post
    The best I can do is try and get each wheel onto a public weigh bridge by parking the car cock eyed on the entry and exit of the weigh bridge as I don't have access to a set of wheel scales.
    Easier a set of bathroom scales and do some math

    corner.jpg

    120 kg scales with a lever 4 :1 gives you 480kg
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    R16 suspension was set at factory using 4 scales.

    Unequal length suspension design was optimised for LH drive, not the best for OZ

  17. #17
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    Well spotted Driven. Thats why some effort on corner weights will make a big difference on a competition car. During the build stage some thought in moving ancillary items to the left side, battery to the left side rear on a 12 etc is a cheap way of making useful gains in braking and handling. It's interesting to see how close you can get to equal readings side to side with the driver in place and 20 litres of fuel in the tank. Not something usually discussed on AF.

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    Quote Originally Posted by Bustamif View Post
    I would expect most of the modifications such as strengthening are for cars intended for rally competition. I have never seen anything about corner weights which is generally something for top end circuit or tarmac competition. Hence my interest to see some corner weight numbers.
    Not according to Renaults Competition book, many, if not most of the mods also apply to circuit racing.

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    Great news, so what does the competition book suggest on corner weights ?

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    The two Renault "Competition Guides" for the 12/15/17 I've got don't have corner weights, neither does the more recent 1985 Renault 5 Turbo Cup manual - when corner weighting would have been used in the set-up. I suspect because corner weighting is individual to each car, depending on the equipment, driver/crew, purpose and circuit, as indicated by Bustamif.

    3006882's vehicle sounds like it is far removed from stock spec, even without taking suspension into account, so it would be best to find a set of corner weight scales and start with the subject car itself.
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    Thanks Simon, so it is really more of a process to follow than a specification like camber or toe settings. I like the suggestion from "driven" below, using 4 bathroom scales with a lever system. I believe that if you try to measure one wheel at a time there would be considerable inaccuracy. The simple test would be to add the result from each wheel which I am sure will be above the actual weight of the car if it's then weighed on a weighbridge with 4 wheels equally on the weighbridge.

    The correct method for an accurate balance is to weigh on 4 scales, anti sway bars disconnected, add or remove shims from spring supports or adjust ride heights if you have adjustable spring seats to get as near as possible to equal distribution side to side. Measure ride heights then wheel alignment to specifications. If you are really serious you repeat the process a few times and play with moving a few components around including the drivers seat.

  22. #22
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    To get really serious on corner weights read of many

    https://grassrootsmotorsports.com/ar...orner-weights/

    Includes fixing under / over steer issues at track

  23. #23
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    Good link driven. The scales I have were acquired from a Lola Indy car team that did not want to freight the scales back to the USA after one of the Gold Coast races. Have lasted many years with a regular check and calibration. The cables are a pain however I don't use them enough to buy new wireless scales.

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