Final Drive Experience/Thoughts

Discussion in 'Hacks' started by Square4, Sep 17, 2012.

  1. Square4

    Square4 Been here awhile

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    I have a 2002 R1150 GS Adventure that has a DMC M72D sidecar mounted to it. I have put about 15,000 miles on the combination and it has performed well. I have made changes and improvements during this time and have had a lot of fun trying them and learning. One of the reasons that I have always loved motorcycles is the rush that one gets from the great acceleration that comes with riding a motorcycle. However, the sidecar rig has always been somewhat on the mild side and I decided to explore ways to improve it. For background the previous owner of the bike had worked to improve its performance. He had put RT pistons into it to up the compression ratio, had the heads ported and flowed by San Jose BMW, put on a Power Commander module, removed the catalytic converter and run it on a dyno to set it up for best performance.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    A few months ago I picked up a brand new old stock final drive that has a 3.2 ratio versus the 2.82 that was on the GSA. Last weekend I decided to put the new final drive on and wanted to provide others with the experience that I have had riding it for a little over 100 miles. The slight negative is that to go 70 mph (speedometer indication) I ran 4000 rpm with the 2.82 final drive and with the 3.2 final drive, I am running 4500 rpm. I actually do not find this to be an issue since I get the worst vibration from the motor from about 3800 to 4200 rpm. Above this range, it smoothes out but does have a minor high frequency vibration that I do not mind but will need to run some long days to see if it bothers me. I also found that I ran 80 mph at 5000 rpm and the vibrations did not increase. The change that I experienced in rpm was similar to using the 2.82 final drive and running the bike in 5<SUP>th</SUP> gear. For my bike the 5<SUP>th</SUP> gear runs 4500 rpm at 70 mph and I found that the vibrations that I experienced was the same as what I got in 6<SUP>th</SUP> gear with the 3.2 final drive at 70 mph. The point is that one can simulate the high speed vibration effect that one might expect to find when going to a final drive with a 3.2 ratio. Having said that, the 3.2 final drive rig was a lot more responsive even when running at these higher speeds because it just seemed like the rig pulled better and seemed to run easier and more quickly would accelerate up to whatever speed I wanted.<o:p></o:p>
    The positive things are that the bike now takes off from a stop like a two wheeler and even on my 20% grade drive way it takes off from a stop without a whimper. It is a no never mind. One does not have to focus on giving it some extra rpms to take off. Riding in the lower gears are just a blast. It has very good low end torque and makes all of the lower gears very responsive and fun to play with. It is like riding a two wheeler in terms of the torque and the responsiveness of the rig. I was playing around and after taking off from a stop I decided to give the bike a good handful of throttle and I broke the rear tire loose and heard a definitive squeal (I think my clutch is working well even tho I have abused it in the past doing some off-roading) and then I shifted to 3<SUP>rd</SUP> and grabbed another handful of throttle and it did it again – that had never happened with the 2.82 final drive. The system just flat gets with the program and makes it a much more fun rig. With the low end response, the ability to run slower and stronger should make this rig better handling on Pacific Northwest mountain roads and I think it should also reduce abuse of the clutch. When you ride this rig it brings a smile to your face because of the way that it responds. <o:p></o:p>
    I know that there are other final drive ratios at 3.0 and 3.3+ but have never ridden these for comparison so I do not know how they compare. It would be neat to have access to one of each of these drive ratios to access them to final out which one works best for a hackers needs. The 3.2 seems like a good compromise to me since it will easily run the interstate speeds and provide a significantly lower end for the slow work in the mountains. I will only learn in hindsight as I gain more experience. Having said this I am thinking that the 2.82, 3.0, 3.2 and 3.37 final drive ratios would most likely be running correspondingly at 70 mph 4,000 rpm, 4,250 rpm, 4,500 rpm and 4,750 respectively. I would then jump to the assertion that this would be like having a top gear referenced to the 2.82 final drive of 6, 5.5, 5 and 4.5 respectively. So one could simulate the top end by running the bike at the corresponding rpm. This would provide some insight to those that might be considering changing their final drive ratio. However, this only covers the top end but does nothing to simulate the great acceleration and responsiveness for the lower gears. I have no ideas how this changes for the other final drive ratios.<o:p></o:p>
    Have any hacker inmates run a series of different final drive ratios and have comments on what their experience has been?<o:p></o:p>
    I also do not have any idea of the gas mileage but would expect that it should not change other than when I am running at high speeds for extended periods of time since I will be at higher rpms.<o:p></o:p>
    Steve<o:p></o:p>
    #1
  2. DRONE

    DRONE Dog Chauffeur

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    Sounds like with all the fun you're having, the clutch is going to get plenty of abuse! :lol3

    Since your rig and my rig are so similar (Adventure gearbox, DMC pusher) we should probably meet up somewhere and swap rigs. Though my motor is stock so won't have the extra oomph your motor mods provide.
    #2
  3. ooweel

    ooweel Jobless, Its OK!

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    This NOS final drive that has 3.2 ratio, what was the part number?

    I fished around on Max's but I didn't see it doinking around in his fiche.

    THANKS
    #3
  4. Square4

    Square4 Been here awhile

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    Drone; I would be up for getting together and comparing rigs. I am going to try to get down to White Salmon and see Elmer's former rig because he had done some neat things to it and I would like to see it so that I can plan some more winter projects. I was also wondering what you thought of Elmer's former rig with a 3.0 final drive and the torsion bar? You said that you would provide some feedback on this comparison when you had the opportunity to ride each of them over the same set of conditions. Have you had the opportunity to do this?

    OOWEEL;

    You can go to another thread and read some additional information about final drive ratios at:

    http://www.advrider.com/forums/showthread.php?t=799079&highlight=final+drives

    The part number is in this thread but I am also posting it here:

    R850GS ABS 3.20 final drive part number: 33112 330 968
    Steve<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    #4
  5. davebig

    davebig Another Angry Hun !

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    I'm new but have started off with an 1150gsadv, I had an extra RT final drive 32/11 =2.9 , I wish it was deeper, it delivers 65-66 mph (gps) @ 4k rpm, I have another 1150gs that's a bit of a hot rod that has a 33/11 it has some Wunderlich camshafts that really deliver some real power above 4k rpm. I have another set that will eventually find their way into my GSA sidecar rig. Many advantages to lower gearing the R11** gs's are over square designs (bore is a larger number than the stroke) because they have allot of grunt people tend to use that grunt rather than shift down and exploit their rpm capabilites. If you'd like more excitement find some rs,rt,s cams they will make some real passing power, and if you can live with the engine spinning a little freer switch to the road bike airtubes (between airbox and TB) but they will cost a little bit of low end torque but add passing power, everthing is a compromise. HP is a product of torque multiplied by rpm .DB
    #5
  6. twintwin

    twintwin Been here awhile

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    The most efficient used FD available in the US for sidecar use, is the one from the R850R, bike imported here. I get a used one, a couple years ago, for a couple hundred $$. You can indeed order a new one from Germany, R850GS, or what ever gearing you like, but the list price is, let say very pricy.

    From Max part fiche, FD of the R850R ABS
    part # 33 11 2 330 972
    Final Drive, ABS 37/11=3.36
    #6
  7. Melrone

    Melrone Been here awhile

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    Whats the atvantage of the 850R final drive? My final drive took a shit last month planning on sending it to Tom Cutter for rebuild.I've consider changing Tranny & FD to a RT for better highhway speeds,but its not cheap..I'm curios now....
    #7
  8. ooweel

    ooweel Jobless, Its OK!

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    I looked at everythin but the 850 R :lol3

    Any swap issues or is it a straight over swap?

    I have an 02 GSA I may put together? Now knowing I can get the gear ratio
    better suited for that application (for me) I think I am gonna hunt one down.
    #8
  9. davebig

    davebig Another Angry Hun !

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    What little I know about FD ratio's r1150gs 31/11, r1100gs 33/11,r11**rt 32/11 some R1100rs's 34/11, r850r 37/11.
    This ad on IBMWR.org 1150 GS/GSA Major Spares - Rear drive, Trans, Shaft, controls, I've emailed with him he has a 37/11 not in ad he may consider selling.
    I had a 34/11 but sold it, wish I hadn't.DB
    #9
  10. twintwin

    twintwin Been here awhile

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    All the FD from the R11XX series are interchangeable, so it is a straight over swap.
    There were not so many R850R sold in the US compared to the R1100R or R1100GS, but they are floating around on the market.
    The FD from a R850R do not pop up very often, but bikes are more available
    Put " site:craigslist.org r850r" in the google box search and you will find them, the bikes with a FD attached to it.
    #10
  11. twintwin

    twintwin Been here awhile

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    Sidecar is all about experiments and feelings, and not only about engineering.

    I have a R1100GS rig, and did the swap with a R850R FD 3 years ago. The accelerations are much smoother, and it ease the load on the transmission and the engine. On the other hand, at highway speed, the engine runs at 500 rpm higher, so bad fuel economy.
    There is some threads with drawings here on ADV regarding the relationship of rpm with the different gear ratio, FD, but cannot find it. I hope a FD engineer will step up now and explain you with formulas what is all about.

    Now, I'm in the process of putting together a R1150GSA rig with a leading link. I will first test the rig with the OEM FD, and I may swap to a R850R, or a R1100GS, but again, it is all about experiments and feelings, so future will tell.
    #11
  12. DRONE

    DRONE Dog Chauffeur

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    Do you have to buy a complete rear drive? Can you just swap out the crowngear set?
    #12
  13. Wolfgang55

    Wolfgang55 Long timer

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    I have read here in ADV that the 15'' car rim w/ street tire will also lower the FD ratio to the ground from the stock BMW rim & trie.
    Anyone know what that new ratio might be using an 08 r1200gs?
    #13
  14. ooweel

    ooweel Jobless, Its OK!

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    I plan on going to an automotive type tire. Something to take into consideration for sure!

    Great Post Wolfgang55
    #14
  15. Abenteuerfahrer

    Abenteuerfahrer Deaf on Wheels

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    [/QUOTE]I also do not have any idea of the gas mileage but would expect that it should not change other than when I am running at high speeds for extended periods of time since I will be at higher rpms.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" /><o:p></o:p>
    Steve<o:p></o:p>[/QUOTE]

    Hola it's me Elmer

    ....Gas mileage will suffer with the change of ratios. My ex- at 3:1 ratios (4100 rpm+_)(70mph) I roughtly get about 30 mpg with it, while I used to get 32-34 mpg witht he 2.86:1...but come to a :eek1 hill the 3:1 eats it up ^.. :clap.

    cheers...
    #15
  16. twintwin

    twintwin Been here awhile

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    It depends how deep is your pocket. Crowngear set is already $600, and you have to provide the housing + the labor to install the new gears (ask Tom for a quote, and or maybe he has one complet unit (3.36) laying around in his shop).
    I went with a complet used R850R FD found on fleabay for a couple hundred $$$, I'm very please with the result and I never will go back with the OEM R1100GS FD on my rig.
    #16
  17. twintwin

    twintwin Been here awhile

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    Right if you use a 175/55/15 on a 15" rim, this is a low profile tire (common use in Europe), but the "offroad" capabilities are limited.

    Wrong when using a high profile tire on the 15" rim, 165/80/15, usually the first choice here in the US for the GS rig, because the overall diameter is the same as the OEM 17" MC tire (Tourance for exp).
    #17
  18. Melrone

    Melrone Been here awhile

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    My FD is shot. This is why I'm looking at different options.Talkwed to Tom Cutter he said its about $500- 700 for him to rebuild mine..He also said to swap out dieffrent from said RT FD I'd have to stick ewith the 1150 series because of the ABS systems are different..So with the intgrated ABS makes the swap limited...
    #18
  19. twintwin

    twintwin Been here awhile

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    Not really sure about this, all the oilhead lines (R850, R1100, R1150) have the same FD housing, and the ABS sensor hole on the FD is the same also. The ABS integrated system has nothing to do with the final drive. You may double check with the GS spot thread, some R1150GSA owner have used a R850R FD as the low gearing increase the offroad capabilties of the big GS. And actually, the 3.36 one I get, the PO had it on his R1150GSA.
    #19
  20. Square4

    Square4 Been here awhile

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    I agree with TwinTwin, I did not have any trouble doing my swap. Everything fit and used the same shimming for the ABS sensor. I do not understand what Tom Cutter is referring to. If you get some clarification on this, I would be interested in learning what Tom knows because he has probably forgotten more than I know.

    Steve
    #20