"Try an inch of preload on them"

Discussion in 'Parallel Universe' started by Rgconner, Oct 19, 2014.

  1. Rgconner

    Rgconner Long timer

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    is what the suspension guy said.

    I put Wilbers progressive springs in my 700GS before the first service. They were Better but only Ok, and still a little soft. I rode for months like that, and felt it was adequate, but not as good as it could be. The bike oversteered a little into corners, sometimes requiring correction, and the front end dived on hard stops, and tended to travel a lot more than the back when hitting small bumps or expansion joints on the freeway.

    Talked with a suspension specialist over a beer at a club meeting and he suggested an inch of extra spacer and see where I was.

    Putting an extra inch of pre-compression through longer spacers made a world of difference. It no longer nose dives, it enters corners with more control and confidence and reduced the "over eagerness" that often required correction, and the front end bounces a lot less on the freeway than before.

    Unexpectedly raised the suspension a bit, which probably explains the cornering improvement by lengthening trail just a touch, but it also means I don't quite flat foot (more of a surprise the first time than a problem) and I also don't lean into the handlebars, which should help with the slight pressure pain I get on 6+ hour days.

    Adding an inch was a real PITA however... getting the retaining ring back in place required more than me leaning on it with shoulder weight and refitting the clip.

    Had to rig up a compression strap using a ratcheting tiedown to get it to compress enough to settle in!

    Does anyone make or suggest a better quality retaining ring for the suspension "pucks".

    The ones that are stock seem little more than unbent paperclip... leave it to BMW to hold together the front suspension of an $11K bike with a .11cent clip!
    #1
  2. Indy Unlimited

    Indy Unlimited Long timer

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    set your suspension for approximately 33% to 35% sag with rider and gear.
    bike up on center stand measure the height of the rear end with rear wheel just touching the ground. now take the bike off the stand and sit on it. measure again and it should be about 2.7" to 2.9" lower. adjust preload to get in that range. 1" of preload is too much and the bike will feel very harsh and dampening will not work right. Go to the next heavier spring if needed and ideally set it up for light preload to get the 2.7" to 2.9" sag range.
    You may need someone to help you measure.
    #2
  3. Rgconner

    Rgconner Long timer

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    At 280 (270 + 10lbs) with gear, I hit your numbers on the upper end, about 2.75, or 2 3/4.

    Before, my sag was about 3.1.

    Overall, I am about .5 inches more preload than stock, because the springs were roughly half an inch shorter than stock, and the instructions did not suggest adding more length to the spacers.

    Front end is not harsh at all, it is better, as it does not "thunk" over every minor bump.
    #3
  4. JRWooden

    JRWooden never attribute to malice...

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    Those little paper clips have always bothered me as well, but I've not seen any alternatives.
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  5. malloy

    malloy Long timer Super Supporter

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    Yeah, well try buying those little "paper clips" for .11 cents! (05 31 42 7 666 224 SUPPORTING RING 2 $2.23) Good idea to have extras on hand should one spring into oblivion. DAMHIK

    INDY - Even though you are an 800 guy, can you point the way to some info on OEM spring rates for the 650 and/or replacements single rate springs?
    #5
  6. Indy Unlimited

    Indy Unlimited Long timer

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    2009-20010 F650GS has front fork springs stock .49 Kg/mm rates
    Stock Rear Shock Spring Rate: 15.7-16.7 kg/mm

    These rates are great if you weigh 40 kilos. I do not understand how manufacturers save money putting light rate springs on all their bikes. This is a universal problem and why it is best to replace with proper aftermarket suspension on just about any bike you buy today.
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  7. Rgconner

    Rgconner Long timer

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    Of course they cost more... they have been hand polished by a buxom blonde Bavarian lass!
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  8. MTrider16

    MTrider16 Ridin' in MT

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    I'm not sure on the conventional wisdom here, but it seems to me that if you raise the pre-load on the front springs a significant amount, it should be possible to raise the forks in the triple clamps some. It might help out with your seat hieght and sag a little.

    Just a thought.

    David
    #8
  9. baloneyskin daddy

    baloneyskin daddy bikaholic Super Supporter

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    Doesn't anyone make fork caps with preload adjustability for these?
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  10. malloy

    malloy Long timer Super Supporter

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    Thanks, Indy - Those are very light springs indeed!
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  11. acap650

    acap650 acap650

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    Increasing preload on a progressive spring compresses the softer part of the spring making it less progressive. The best solution IMO is a straight wound spring of the correct gauge for the rider's weight.
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  12. Indy Unlimited

    Indy Unlimited Long timer

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    Yeah I agree I am not a big fan of excessive preload.
    I like getting the right set of springs that work with small assembled preloads.
    #12
  13. malloy

    malloy Long timer Super Supporter

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    So, Indy & ACAP - to the question of where to find proper single rate springs in the aftermarket. Haven't had much luck with this in other threads. Any suggestions?

    Does one order a custom set? What specs? From who? etc.:ear:ear

    Much obliged.
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  14. Indy Unlimited

    Indy Unlimited Long timer

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    #14
  15. malloy

    malloy Long timer Super Supporter

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    Is that all? :rofl Thanks Indy. You make it sound so easy. Now something to work with. :clap
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  16. Rgconner

    Rgconner Long timer

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    Little excitement today...

    on a club ride and while in a slow speed (15ish? Just enough where I started to counter steer) left turn I hit either a bit of oil or a little black ice and the front wheel started to shoot out. (We could not find any oil on my wheel after I stopped, so we suspect black ice)

    The slide lasted maybe a foot or so and then the front wheel grabbed again, and started to compress the front end. I was sure it was going to fold and high side me.

    "Oh shit," I thought "I am going down." The same thought ran through the 4 riders behind me that started to scatter to avoid whatever happened to me.

    But with the preload the nose did not fold, but sprang back, ripping the bars out of my hands, My gentle pressure on the handlebars turned them out of alignment (I am a hold on loosely kinda of guy) and the sudden grab of the front tire slammed them back the other way.
    That straightened out the bike and stood it upright again.

    In the process I lost control of both throttle and clutch and the engine stalled. Quick grab of the bars and the clutch saved me from running out of momentum, I restarted the engine while I completed the turn.

    Luck or skill?

    Well, I am not that skilled and I don't believe in luck, but I do believe that adjusting the preload kept the front end from folding and having good habits like holding on loosely kept me from screwing up the correction the bike made on it's own.

    While I jammed my left wrist pretty good when those handlebars snapped back but I keep an ace bandage in my kit because I have a week right ankle. A tight wrap and I was good to go.

    "The Save" was the talk of the lunch stop, but I can say I rather had not had the attention.

    Just another day on the road of life...
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  17. Indy Unlimited

    Indy Unlimited Long timer

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    ADV rider rules:
    When you save it credit goes to rider skill !
    When you lose it credit goes to bad luck. :wink:

    Glad you saved her and enjoyed the rest of the day.
    Can't say as I have ever seen a front end high side but theoretically it is possible.
    Black ice can be very nasty. Been there & done that and it is not fun.
    #17
  18. Rgconner

    Rgconner Long timer

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    Well, it started to low side as the front end slid, then grabbed traction and tried to high side. I suspect had the suspension continued to fold it would have been more or less 90 degrees from direction of travel and I would have "come a cropper"

    I thought that is how most high sides happened, loss of traction followed by sudden return of traction.
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  19. Indy Unlimited

    Indy Unlimited Long timer

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    You are right but the front end high side is a very rare animal.
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  20. Rgconner

    Rgconner Long timer

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    Good thing too, because contemplating doing ass over elbow cartwheels with a ~450 lbs bike is not my idea of fun!
    #20