BMW Replacement Springs

Discussion in 'Old's Cool' started by east high, Aug 22, 2011.

  1. east high

    east high Been here awhile

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    I'm looking to refresh the suspension on my /5 while maintaining a stock-ish ride and appearance. I found this page detailing the options for the front.

    According to the fiche supplied by Max, my best 'stock' bet for the fork would be p/n: 31421232017.

    Now, I'm using the fiche to look up the rear and I'm stumped on what HD means, but if it's anything like the HD spring mentioned in the above link it's not for my bike.

    I'm thinking this spring, p/n: 33531235550, is the ticket for a stock rear replacement.

    Am I on track with these decisions? I know about Icon shocks with the chrome cover that look stock, but I don't want an unevenly stiff ride. Ruling out progressively wound shocks, is there a stiffer fork spring that would match the Icons if that's a better route?
    #1
  2. JimX

    JimX .. .

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    I like the pre-81 RS fork spring, 31421232017.
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  3. east high

    east high Been here awhile

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    A quick search on Max's site and it looks like this spring is labeled as 'heavy duty', probably due to the added weight of the RS fairing. Sounds like it might be a good match for the Icon shocks?
    #3
  4. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Most guys try to combat brake dive with stiffer springs. All that does is compromise the suspension and beats you and the bike up. It's hard on the steering head bearings, wheel bearings, front end components and everything else on the bike that gets jarred from the excessive bouncing. All this to keep the front end from diving when the brakes are applied hard.

    Well, don't use the brakes! Simple as that. Brakes are for stopping, use the throttle instead. :lol3

    Sounds like a joke, but I'm not - these bikes want to be ridden smoothly, and that's where the speed happens. Racing as fast as possible to the next turn, jamming on the brakes, negotiating the turn, hitting the throttle down the next straight .... no no no. All wrong!

    Just get it right and run through the turn. These are first and foremost, touring machines (sporty - but still touring) and that's what they're good at. Ridden like touring machines they really shine.

    First off, how do you know you need new springs? How much sag do you have?

    Also, even the stock springs are progressively wound, so the word progressive doesn't delineate anything here. But stay away from the Progressive (brand) stuff; springs are waaaay too stiff!

    So, the soft springs are what work best in these bikes. And it is possible to get the Ikons with different springs. But there are so many variables when it comes to shocks, this could turn into another oil thread. :D
    #4
  5. DaveBall

    DaveBall Long timer

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    Wirespokes has it right.

    These bikes do need good suspension, but good suspension does not mean the same thing as stiff springs. As with all bikes, these bikes have their own quirks and you have to learn how to ride them. They definitely need to be treated like the touring machine they were designed to be. Don't use the brakes so much as the engine. It will slow you down pretty damn good. Also, don't overload the damn thing. They did not come with top boxes and racks to hang 500 pounds of gear on, for a very good reason. Sure they will do it, but expect to wear things out much faster and expect the handling to be worse than a rubber cow.

    Think more Gentleman Touring, where you load a few days worth of clothes in the bags and pack your credit cards in your wallet and the bike will give you lots of great enjoyable and comfortable miles. Many of these bikes push in excess of 500,000 miles and most of them with a minimum of issues.
    #5
  6. east high

    east high Been here awhile

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    Yep. That's what I'm looking for. I don't want a stiff ride; I hope to keep it stock. I think this all came about from me inspecting my worn and leaky rear shocks. Replacing just the cartridge and bushings is over $200 a side. Ouch :eek1 I'm just looking for options if stock is NLA or overly cost prohibitive. The idea of going with stiffer fork springs was only if I went with stiffer Ikon shocks to keep the bike balanced. Good to know Icons come in different spring rates.

    Thanks for the advice guys. Please keep it up.
    #6
  7. supershaft

    supershaft because I can

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    You need new shocks! New shocks and stock springs with more preload to your taste and you will be amazed!
    #7
  8. Wirespokes

    Wirespokes Beemerholics Anonymous

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    Watch ebay for a set of Konis. They show up all the time. They're rebuildable, and different weight springs are available, so it's not like used ones are a waste of money. They're actually a great value in a replacement shock and will transform your bike. Of course, watch for a set that look good with undamaged shafts. I rarely change front springs and the Konis have worked fine with them. Just recently I removed the front springs from the LS because they were way too stiff - probably Progressives - and replaced with stock and the bike feels much much better now.
    #8
  9. batoutoflahonda

    batoutoflahonda Long timer

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    No doubt. Even my R1100S has to be ridden smooth. Like I tell the sport bike guys, it's like an old prop driven fighter plane. You have to set every thing up. The new sport bikes are like jets. Just give it gas. Meaning with a red line at 8K instead of 16, You can't be doing all that fancy down shifting-jam the brakes-punch it crap. Try that on a BMW twin and heavy compression braking will lock the rear, the front will dive, and that's when stories are made. On a recent trip with a friend of mine, I watched him pick off new sport bikes in the twisties on a '76 R90/6. It's all in the wrist.
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  10. Wirespokes

    Wirespokes Beemerholics Anonymous

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    These old airheads are deceptively fast. By that I mean, you don't feel like you're going all that fast, but you are! Doing it right, you don't get that adrenaline racing rush, just a 'calm, workmanlike-attention-to-details' state of mind. They're faster than they seem.
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  11. DaveBall

    DaveBall Long timer

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    As an alternative and less expensive replacement, I put on a set of Progressive rear shocks with their HD springs. I went with the HD springs because I do a lot of 2 up riding, and neither of us is getting any lighter. Left them on the lightest setting and have been very happy with them.

    As to BMWs being deceptively fast. Once you learn the bike and how it likes to be ridden, you will find that you become smoother and smoother in your riding skills. It's kind of fun, every once in a while, to shock the hell out of some of the go fast crotch rocket crowd. Talk to any F1 or Indy Car driver and you will find that the ones that win the races are usually the smoothest drivers.

    Not everyone has to be like Paul Tracy. I always remember his statement "If you can't win the show, then BE the show!". I watched him either blow up or kill many a car during his racing career. Also watched Michael Andretti out maneuver many a driver in a slower car. Michael was one of the smoothest drivers I have ever seen or met.
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  12. Lornce

    Lornce Lost In Place

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    This.

    :deal

    p.s. will all you progressive spring afficianados please send me your stock fork springs?

    :norton
    #12
  13. adrenal

    adrenal skrunkwerks.com

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    How about the damper part of the 'spring-damper' system?
    A few years back. I mucked around with fork oil weight because I always found the feel of the front end of your average airhead a little too spongy and indirect or isolating from the road surface.
    The BMW spec is for 5 weight. 10 weight proved too stiff so I tried a 50:50 mix: Poifect! So 7.5 is good for me but its partially a subjective thing as well as depending on rider weight and riding style, state of roads around you etc etc.

    So 7.5 became the stock spec for me. It slows the diving on braking a bit too. Have a play...
    #13
  14. east high

    east high Been here awhile

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    I scored a clean pair of 7610 Koni shocks. I'm guessing the number printed on the spring (220) is their weight rating? From the sound of it, a set of Konis in the rear and a touch more preload and/or thicker oil in the forks with stock springs might be a good pairing?
    #14
  15. Lornce

    Lornce Lost In Place

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    Thicker fork oil or additional spring preload will accomplish two entirely different things.

    Personally, I'd preload the fork springs to 20-25% (of total fork travel) sag under the unladen bike and leave the fork oil at 5w. This nets a plush ride with good cornering manners.

    Front springs that are too stiff and fork oil that's too thick results in poor cornering manners as the front wheel ass'bly is unable to respond with subtlety to road surface irregularities.

    imho,
    Lornce
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  16. east high

    east high Been here awhile

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    Thanks for the advice, Lorence. I like the cut of your gib. So preloading the fork springs is accomplished by a spacer of some sort? I've only done this once and it was on a different bike with a different setup, but it was accomplished with a piece of pvc pipe cut to length and placed between the spring and fork cap.
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  17. Lornce

    Lornce Lost In Place

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    You've got it. The target is to get the bike sitting under it's own weight with the fork compressed 20-25% of it's total travel.
    #17
  18. Mallard

    Mallard insert joke here

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    Thank Wirespokes, Daveball, & Lornce, I just re-read your posts. I enjoy your sensible perspectives/aims for the front end set up.

    The R90/6 is only just keeping it's headstock off the axle, so it's time for a rebuild, including front springs.

    It's like Goldilocks & The Three Bears over here. The R80 is too stiff, the R65 is too soft. So I'd like to get the R90 right.

    Before adjusting preload, before experimenting with oil, I'm wondering on advice for the spring itself. Wilbers, Wirth, Progressive.... the makers are endless. Were the original springs or 'heavy duty' original springs a good match for a bike that is only ridden solo, or look elsewhere? All I want to do is get the bike to behave as it was meant to.
    #18