GS ground clearance

Discussion in 'Hack Vendors' started by Sparrowhawkdesign, Apr 2, 2011.

  1. Sparrowhawkdesign

    Sparrowhawkdesign Been here awhile

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    I am seeing a lot of questions about ground clearance issues with the BMW GS models with sidecars. First off I have to say that I love the Telelever front ends. The problem we run into here is that when we install a new ball joint mount plate to reduce the trail and provide lighter steering, moving the wheel forward causes the front of the bike to drop slightly. Of course this modification immediately gets the blame for the loss of ground clearance.

    The GS is built with a reasonably long travel, softly sprung suspension. It provides an awesome smooth ride over very rough terrain in its stock two wheel configuration. Then we add the weight of a sidecar which of course we load down with everything but the Kitchen sink as the saying goes. What have we done to help the suspension compensate? A lot of the time nothing, but of course the front end modification is going to get the blame.

    Traditionally, when installing a sidecar to any bike, one of the first things suggested to the new sidecar rider would have been to upgrade the suspension. I have never put a sidecar on a GL1500 for example, without changing out the front springs. Those of us that install sidecars, and specially for the first time owner, have to take some of the blame for not taking the time to educate our customers properly in this regard.

    Now the reason for this post is not to divert all the blame for ground clearance problems away from the front end modifications. Of course they can contribute to the problem as well, but we need to look at the whole picture to really solve the problem.

    As part of our ongoing effort to improve our products when we see issues arise, most of our front end mods have been designed to help compensate for this loss of clearance. As we build these in small batches, it allows us to make changes fairly quickly. In fact, we have one batch being made right now with this change.

    Ride Safe Barry
    #1
  2. twintwin

    twintwin Been here awhile

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    Could you explain how you will keep the front end not to drop to much in order to have the same ground clearance. Did you only redesign the lower bridge? or did you also perform some alterations on the telelever, and or on the front shock set up. Pictures would help, thanks.
    #2
  3. iHop

    iHop Adventurer

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    Dauntless/DMC (steel lower triple tree extension):
    [​IMG]

    Dedome (raised lower triple tree extension + Telelever de-rake):
    [​IMG]

    Click here for an animation that shows the difference better

    Ground clearance is not the only area that the DMC experiment I paid for failed and why I switched to Dedome. For $300 to DMC I got: A powder coated 3/8 steel plate (would have been merely expensive if they had only charged $100) that didn’t mate to the stock fender. No instructions. A front wheel that rubbed on the “beak”. A broken mud fender and blown fork seals when the suspension bottomed (suspension already upgraded with very stiff Wilbers). Top fork tube pivots at the absolute end of their travel. When I encountered this, I called Jay and ask him how this part is supposed to fit, I got the answer, “I don’t know, I didn’t design it.” How they improved the part when they didn't want to hear anything about how it worked, or didn't work in this case, once they got paid is not clear to me.

    Post-sales support, zero.

    [​IMG]
    #3
  4. twintwin

    twintwin Been here awhile

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    Thanks iHop for the 2 pictures and the animation, that speak for itself.
    I have also a Dedome, since now 4 years, and I'm still very please with it.
    My question to Barry from DMC was: what OEM parts are modifed and or new parts manufactured in oder to reduce the trail of the GS without changing the OEM groud clearance, because he does not give any details. Pictures will help to understand how is made this new DMC trail reductor.
    #4
  5. claude

    claude Sidecar Jockey

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    This situation is always a delima whenever doing a trail reducer or modified triple trees. As Twin Twin knows this can happen with ANY manufacturer of a trail reducing system if the homework was not done well.
    Not only does kicking the front forks out with various trail reducers lower the ground clearance due to the geometry factor it also allows a different leverage to be working on the front spring(s). This makes for less EFFECTICVE spring rate which also does no one any favors and can also lower ride height in and oof itself.
    Yes, there is some dancing required to keep or raise ground clearance once a trail reducer system is installed as raising the front end back up gains trail again. Somewhere in between losing trail (desired) and gaining it back(undesired) is the best compromise. This is true no matter if the bike is a telelever or has conventional triple trees.
    I had spoken to Jay and others about this a while back regarding various bikes.
    With modified trees is is a good idea to request fork extension and the approprite clampos to secure the joints created in the fork tubes.
    With telelever front ends the plate or bridge (1200 gs) can possible be made to gain back the drop from moving the wheel forward. Another thing is that on most tlelever fronts aftermarket shocks do allow ride height to be gained back. Tree type front ends should have heavier springs.
    The quick and easy ways to reduce trail may make for easy steering but can create other issues which may or may not be a bad situation depending upon th ebike itself.
    I still prefer the leading link front ends as they can be designed specifically to work well on all fronts.
    Sorry to but it just food for thought.
    #5
  6. D.Bachtel

    D.Bachtel Been here awhile

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    I just want to know in inches....
    How much clearance?
    Lowest spot overall off the three patches of tire.

    Don in Nipomo
    #6
  7. iHop

    iHop Adventurer

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    8.5" at the back half of the skid plate.

    [​IMG]
    #7
  8. D.Bachtel

    D.Bachtel Been here awhile

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    Nice Ihop, that's plenty! How about some shots from the front and the rear down low.

    That's a beautiful BMW you have there.:clap

    Don in Nipomo
    #8
  9. Sparrowhawkdesign

    Sparrowhawkdesign Been here awhile

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    Sorry for the delay in answering your post. This is the first time I've had a chance to get back to this. Long day/night Sunday and two new workers starting yesterday kept me busy. Can't seem to do this like I did when I was younger. LOL

    Just did a quick picture search and I can't find the pictures I need to show you. I will have someone search for them today so I can post them. Worst case I have a batch of modified parts I should be getting next Monday so if we can't find the pictures I want I will have more taken next week and post them for you.
    Barry
    #9
  10. Sparrowhawkdesign

    Sparrowhawkdesign Been here awhile

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    First off let me thank you for this post. While I wasn't directly involved with your situation I appreciate the opportunity to respond to it as best I can with what I know. Also, if you want to PM me with your name and phone number and the approximate date you ordered the part from us I will attempt to look into it for you.

    We have been doing this type of modification for over ten years and I personally for over twenty. While there have been the occasional problems over the years, for the most part I would say we have been about 99% successful. Unfortunately the 1100 GS was one that caused us some problems in the beginning. The first one we did I believe was the R1100R. We did make the mistake of thinking the 1100GS was the same as the R and sent one or two of the same part out in the beginning without actually having a GS in house to check. Won't make that mistake again. LOL

    We did finally get a GS into the shop and made the changes needed. Thinking we had the issue solved we once again started sending the parts out. At first it seemed strange that although we had actually had a bike in the shop and made the mods that corrected any problems on the GS, some customers were having success and some weren't. Eventually we found out there were two different fender designs that we weren't aware of. I can't say for sure but this may have been about where your problem came in.

    As far as our response to your case the way you describe it, I wasn't involved and I'm not going to try to argue with you about what happened as I just don't know. What I do know however is this. Our policy from day one has been to do whatever is possible to make the customer happy. In this situation it doesn't suprise me that Jay said he didn't know the answer as he didn't design it. I have seen him say this on a number of occasions.
    I have also seen him always tell the customer he would look into it and have the person that designed the part get back to them and try to solve the problem. I also know that if the problem could not be solved the customer would be asked to return the part for a full refund. This is and always has been our policy and I know Jay is adamant about it. I have seen occasions where he has insisted on refunding the customer even when it has been obvious the problem was something the customer was doing wrong and they just could not get it right.

    I understand and accept the fact that in your case you could have experienced some fender problems. I will dispute however your claim that this caused damage to your fork seals. I have done many of these modifications on hundreds of motorcycles without any issue with seals and a lot of them have fork tubes that angle forward a lot more than your GS.
    We will have to agree to disagree on that one.

    As far as the angle of the fork tube being near its limit at the top of the tube I agree with you. It is almost at it's limit of travel. The fact is however that it is still within it's range of movement and has not ever been a problem.

    I should probably take this opportunity to explain why we went with this method of trail reduction. In the beginning we actually looked at doing it similar to the way Dedome does. He is in effect actually "raking" the front end. On a normal front end that would mean changing the angle of the steering stem on the frame while maintaining the position of the wheel. This is much simpler on the Telelever. After asking a number of potential customers about doing this we found that for the most part they did not want to have their A arms cut up and welded on. Also the down time needed to do this along with the possibility of their part getting lost in the shipping were also problems for some. We then looked at designing and producing our own replacement A arms but in the end determined this would make the cost of modification too high for most people. After looking at the problem and possible solutions we decided to go the way we did.

    With the exception of some of the early steel 1100GS parts we have had no problems with this method. We have made some modifications along the way to help with the ground clearance issues however and as always will continue to listen to any issues customers have with any of our products and do our best to solve them.

    As I said in the beginning, please PM me your info and I will look into your situation for you.

    Barry
    #10
  11. iHop

    iHop Adventurer

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    You have that completely backwards.

    Dedome is de-raking the front end.

    Raking the steering head is what you do to make a chopper. Exactly the opposite of what has been done here, or what is needed on a sidecar rig. Choppers have lots of trail. Sportbikes have very little.

    The wrong way to make a chopper is to extend the lower triple tree, that reduces the trail. People who wanted choppers on the cheap, because cutting the frame is expensive, would extend the lower triple tree, put longer forks on, and get an unrideable bike. However, that’s one of the right ways to reduce the trail on a sidecar rig, with a long history. Harley had adjustable triple trees to accomplish that for sidecar use for a very long time.

    Actually Dedome does the exact same thing Dauntless/DMC does, but by 1/2 the amount, raises the fork bridge to compensate, and then de-rakes the head (by shortening the Telelever).

    Options to reduce trail for sidecar use:
    One: extend the lower triple tree. (Dauntless/DMC)

    Two: de-rake the steering head (like a sport bike)

    Three: do both. (Dedome)

    That’s why the wheel ends up in the stock position, although the steering geometry has been very much changed.

    De-rake the head (reducing trail some), pulling the wheel back, then kick out and raise the forks with an extended fork bridge (reducing trail the rest of the way).
    #11
  12. Sparrowhawkdesign

    Sparrowhawkdesign Been here awhile

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    Sorry, but in your apparent need to prove me wrong you are not paying attention. There is no such thing as de-raking to my knowledge. I suppose if the steering head was brought back to complete vertical that term might apply. LOL It doesn't matter which direction you change it, you are still changing the rake angle. What you end up with is more or less rake than you started with. I was assuming you knew this and would understand what I was explaining. I explained it this way to help people that know less about this get the concept. If, as I said before, all you want to do is try and prove me wrong then this discussion is ended. If however you have any other thoughts or ideas you would like to share I will be happy to discuss them with you.
    Barry
    #12
  13. iHop

    iHop Adventurer

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    Well then, let me Google that for you:
    http://www.google.com/search?source=ig&hl=en&rlz=&q=de-raking&aq=f&aqi=&aql=&oq=
    Obviously adding rake angle (raking) and lowering rake angle (de-raking) are novel new terms I made up just to make you look bad. Caught me.
    #13
  14. Sparrowhawkdesign

    Sparrowhawkdesign Been here awhile

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    Thanks for that. I see where the word derake came from. Unfortunately it is not in my dictionary although the work rake is. Somebody made it up to describe doing a reduction in the rake angle and it obviously has become a way to describe a reduction in the rake angle. I had never see it used before. I would have thought to derake would have been to describe completely eliminating any rake angle leaving a vertical steering head. Obviously I have done enough front end modifications over the years to know that Dedome was doing a reduction in the rake angle. As I pointed out, we looked at doing the same thing in the beginning before I had ever heard of Dedome. You have to understand that after almost forty years of building, designing and installing sidecars to have someone suddenly tell me I don't know what I'm talking about is going to cause a reaction. Obviously it did. Sorry for that. I just didn't think I would have to go into so much detail to describe what I was talking about. With your knowledge of this subject I thought you would get it. Barry
    #14
  15. jpalamar

    jpalamar Long timer

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    Having a bike, '07 GS Adventure, on its way to DMC I thought I'd like to understand a bit more. Let's see if I understand all that's going on, not so much from the absolute, but from the pracitcal.


    Since I have opted for the trail reduction to improve steering, I'm inclinded to understand that I will lose some ground clearance, though minimal i.e. <2 inches?

    Trail reduction in itself would effectively increase ground clearance, considering just geometry alone (raise the front end), but factor in a soft suspension along with an increased 'downward' vector (reduced trail), plus the added weight of the side car (downward force), and voila, some reduction in height where one would think it should increase height???
    #15
  16. Sparrowhawkdesign

    Sparrowhawkdesign Been here awhile

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    There are going to be some gaps in my answering here as I am working on three different sidecar jobs while training a new employee and answering phones. :rofl

    For the basics regarding rake and trail take a look at this site first.
    http://www.seegercycle.com/Rake-and-Trail.aspx

    Barry
    #16
  17. Sparrowhawkdesign

    Sparrowhawkdesign Been here awhile

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    Finally got a picture of the new part along side one of the earlier ones. You can see the change made to solve the ground clearance loss. This one is for the BMW 1200GS.
    Barry

    Attached Files:

    #17
  18. Melrone

    Melrone Been here awhile

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    I have the older one on my03 GSA which works just fine,but I also replaced my shocks with Works shocks.I also lowered my bike to a 31" seat height which works great..My biggest complaint was no instructions with anything I bought.Why is that?I got hte same answer that I Hop got.Why is that??:deal
    #18
  19. jaydmc

    jaydmc Long timer

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    The part installs exactly the same as the factory part, So no instructions are needed as it is the same as in the factory service manual. We have however with the last one we installed in house taken step by step photo's to be able to include with the part.
    With the new part the bike sits about 1/8 of an inch higher then it did with out the sidecar,
    Ground clearance depends on many factors.
    Jay G
    DMC sidecars
    #19
  20. claude

    claude Sidecar Jockey

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    I am glad to see you all have come up with this modification Jay. I remember we had quite a discussion about this a while back,. Good job!
    #20