Spring rates

Discussion in 'Hacks' started by Ridn3, Sep 30, 2015.

  1. davebig

    davebig Another Angry Hun !

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    Jim, Why ? I can't see where knowing the stock spring rates is of any use, weigh the damn thing and talk to Klaus or Ad Donkers or perhaps Mikepa , Klaus I'm certain has a chart or formula based rig weight, it works and has worked for other inmates quite well. Otherwise it's a long process as I found out converting Blackie to an aftermarket auto shock I think I bought 3 or 4 springs before I got what I wanted.
    As for the extra length shock I think most of the aftermarket suspension builders use the same shock and assemble with whatever length they want.
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  2. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    The suspension guru you are buying you springs/shocks from should know. And if they don't they should have the capability to determine it in their shop.
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  3. claude stanley

    claude stanley Claude

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    Spring rates vary on different scales depending on coil size an spacing and whether the spring is wound to be progressive or not. Sometimes discussions can compare apples to apples and sometimes not. Checking the spring rate at various points in 'bump' can be kind of shocking at times. Just splitting hairs here lol
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  4. claude stanley

    claude stanley Claude

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    Weighing each wheel is a start. 'Optimal' for one rider vs another can vary. Optimal for one rig or another can vary also depending on chassis, track width , rider, load, terrain and even swingarm designs etc. A good compromise is it.
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  5. SLACKER

    SLACKER Been here awhile Supporter

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    Perhaps I should have explained further.......Every shock I have ever purchased for a Rig has been too soft and I have always had to return it at least once. This goes for Ted Porter's (Both Wilbers and TFX), Klaus at EPM, as well as Ohlins from Propilot. They have all claimed to have knowledge about setting up shocks on sidecars. I have given them weights on all 3 wheels, Sag distances , my weight, my girlfriends' weight, my mother-in-laws weight , gear weight etc etc ad nauseum and they have still sent me shocks I have not been happy with. I have had to dismount/mount/dismount/return/mount shocks before I was happy. I have limited time here in the USA to work on this rig, and I am hoping to get the spring rates correct the first time around. Also, changing the shocks on the 1150 GS is no small feat ....at least for a Motor Moron such as myself. I suspect that I like my rigs with stiffer suspension than many other riders. Ad at LBS-NL stated that the rear spring that I finally chose was the heaviest he has ever installed on a 1200GSA..........by far....And I love it's performance, at least on the tarmac
    This time around I am trying to take a different tack. I know that I have not been happy with shock rates being 50% stiffer than stock on my Vstrom Rig, My R100 EML, or the car shock on this current rig, because that is what the suppliers told me they were sending me on their first try, but I do not have records of the specific spring rates..... If I knew the stock factory rates I think it would help me extrapolate a good choice. I may be dreaming, but I would really like to get it right the first time this go around.
    I can of course contact one of the suppliers and ask them about stock spring rates, but I thought I would throw it out here to see if anyone knew off hand or knew where I might find the info.
    Cheers..........I hope everyone is having a brilliant Thxgiving.........
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  6. steam powered

    steam powered just a regular punk

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    Not the factory rates, but the starting rates for Ohlins on a R1150GS with an 80kg rider is 140 N/mm on the rear and 52 N/mm front, so if you are looking for a % increase you could use these as your baseline.

    Because an 1150GS weighs the same as a 1200GSA and BMW didn't alter the linkage ratios (Ohlins' starting point is also the same for both bikes), I would suggest starting with the same spring rate as in your 1200. If your 1150 doesn't have a leading link, I would use the same % increase as used in the rear for the front.

    HTH
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  7. brstar

    brstar Long timer

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    That's one reason I love my Fournales.
    When i ordered them I gave what I guessed would be my future sidecar weights.
    Simply add or subtract air to suit.
    Initial sag is the indicator.
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  8. SLACKER

    SLACKER Been here awhile Supporter

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    Thanks for your comments. Ad from LBS gave me the ratings from the spring he installed on my 1200GSA Rig (59-59 175/240) which I will take into consideration and I'll be ordering Touratech shocks from Mikepa at LBS-USA......A great guy to deal with btw. ....Wish I had money for one of his builds here in USA . Need to sell off some bikes to free up some cash.:deal Anybody interested in one of the following?
    1976 R90S with Heinrich matching paint Daytona
    2018 R9T urban
    1994 R100GSPD Replica by Greg Hutchison https://gregsgssite.shutterfly.com/1099#851
    1987 K100 EML- Runs very nicely but not a garage queen- New Koni rebuild- Bosch fuel pump $5,500-
    1964 R60/2 original paint Dover White
    I know that this is not the right place to post these things for sale and I will get around to posting in appropriate classifieds...........Just thought I would throw it out quickly before heading to work. Cheers
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  9. claude stanley

    claude stanley Claude

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    On the sidecar A couple more concerns or thoughts on spring rates. Shock angle does come into play. Where the shock is mounted on the swingarm can be a factor too. So ..without writing a 'book' here consider shock placement on the swingarm in radical terms. What if the swingarm was 10" long and the shock mount on it was 3 inches from the pivot. Crazy but thinking in extremes may drive the point home. ...... Number 2: What if the shock was laid down more due to it's mounting points. Ideal scenario may be that the shock's upper and lower mounting points were in line the arc of travel of the swingarm. So many times as noted earlier apples may not be compared to apples in many discussions. ........ One case a while back was a shock that was said to be too soft and the discussion went for a while. The builder ended up actually adding a second shock for a dual shock suspension on the sidecar and all was okay then. Well the issue was not the first shock really but the shock mount positions. ....So it goes :-)
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  10. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    YES!! And to Claude's point, when my DMC shock tower failed on the CDR, the first sign was that the tub's suspension appeared to get really soft, then bottoming and finally collapsed completely. The first thing I did was get on my cell phone and called my buddy Gil at Works Performance. When I got him on the phone I asked him to start building me a new shock so it could get shipped out to me allowing us to continue on. He was really confused as to why I thought the shock had failed and finally he explained that it the shock hadn't puked it's fluid it had to be something else. At first it was hard to see the issue but finally after a real close inspection I found the the tube that the shock tower was mounted to had partially collapsed causing the shock angle to change which changed the geometry.

    Look at the picture and you can see the shock tower leaning rearward. DMC's design is supposed to have the shock mounted straight up and down, and it's leaning back just this much made it extremely soft. The red ratchet strap was used to keep it from bending more allowing us to get into town.

    CDT_shocktower.jpg
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