Rented an 08 GS and WTF!

Discussion in 'GS Boxers' started by Texmoto1, Aug 8, 2010.

  1. Texmoto1

    Texmoto1 Adventure Berzerker

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    Some friends and I recently rented some bikes in San Francisco and did an epic trip of Northern California. 2 of the bikes we rented were 2008 GS's. At home my buddy has an 09 GS and I have an 07 GSA. Within 5 minutes of getting on the rentals, I noticed a DRAMATIC power difference between the bikes we ride at home and the rental machines. They also ran smoother and had slighly better gas mileage. In terms of power, the best way to explain, would be to say that when excellerating in 6th gear at 70 mph on the rental feels like mine in 4th!
    I understand that there is a little more power between 07 and 08 however my buddies 09 really doesnt feel much if any faster than my 07. The only 2 differences I can find in ours vs the rentals are that the rentals have cast wheels and 30-40 K miles and ours have spokes and 6-12 K miles on the odometers.
    I asked the rental company if they do anything different with maintenance or set up other than by the book and as I expected....Nope. Just a couple of GS's run hard and put away wet.
    The only thing I can figure is that those rental bikes have loosened up and are running smoother and faster than ours?

    Anybody ever have or heard of this kind of difference before?
    #1
  2. BluByU

    BluByU Long timer Supporter

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    Glad you enjoyed your time in CA.
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  3. ricohman

    ricohman Long timer

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    No. But why do people that own a GS go and rent a GS? :D
    #3
  4. David_Moen

    David_Moen Long timer

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    I think you answered your own questions, rental bikes get run hard, not babied. They probably are well run in. I know my bike feels more powerfull and smoother at 20K than it did when brand new.
    #4
  5. marty hill

    marty hill The Energizer Bunny

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    I have run in 6 12GS's. They have all felt much better after about 20k. I also run them after 50 miles at a bit more rpm's than recommended.:lol3
    #5
  6. Schtum

    Schtum Free Genie

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    Having rented a GS from Dubbelju in SF in 2008 and going back there with my son, from our home here in Scotland, at the end of this month to rent a couple of GSes for a few days, the answer is....."because we can".

    It's the perfect bike for not only doing some miles but also attacking some of the Bay Area's finest goat tracks in company with a GS riding buddy who lives in the Bay Area.
    #6
  7. sh2515

    sh2515 Been here awhile

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    no idea what I am talking about but ran into this website and think that some truth maybe in it given your experience with rental bikes nobody gives a rat ass about.
    #7
  8. Tork

    Tork Aluminum Cigar Stuffer

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    "Ride it like you're renting it" Makes sense now.
    As does "Rev Limiter, a bump a day keeps the carbon away"
    #8
  9. muddbutt

    muddbutt Pork Chop Expert

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    Heavy tires and rims have a big impact on performance.
    #9
  10. kindofblue

    kindofblue Ride it like you stole it

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    Ah, yes, the motoman break-in. Did it myself on several bikes
    #10
  11. Tork

    Tork Aluminum Cigar Stuffer

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    Has anyone ever weighed cast vs spoke wheel sets and posted the results? I would be interested to know.
    #11
  12. sh2515

    sh2515 Been here awhile

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    what was your result?
    #12
  13. JimVonBaden

    JimVonBaden "Cool" Aid! Supporter

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    The weight difference is about 2.5 pounds.

    There are lots of reasons for the difference in performance. Miles, quality of tune-up, motor variables, accessory weights, altitude, humidity, fuel quality, all can have an effect.

    Jim :brow
    #13
  14. Tork

    Tork Aluminum Cigar Stuffer

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    Thanks Jim

    It seems to me not to be that significant.

    Tork
    #14
  15. muddbutt

    muddbutt Pork Chop Expert

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    Yes, but it's unsprung weight. So it has a much bigger impact than just the weight of the rim because when it is spinning it is much more difficult to accelerate or stop- the force required to accelerate the rim is exponential with speed.

    The difference in rear wheel horsepower in a car with 6 lbs of difference in rear wheel weight is up to 8 hp gain at the rear wheel dynoed.

    So, translating this over to the BMW - 3 lbs savings - I would not be surprised if it gain 2-4 hp at the rear wheel just by having a light set of rims.
    #15
  16. Anorak

    Anorak Woolf Barnato Supporter

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    The weight of the wheels or other parts of the drivetrain will not alter the actual amount of horsepower at the rear wheels. If the power output is measured on an inertial dynamometer, the numbers will differ but that is because it measures acceleration and then uses the rate of acceleration over a period of time to calculate horsepower. Hmm, seems like a number of variables could make the process less accurate.
    #16
  17. muddbutt

    muddbutt Pork Chop Expert

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    I am talking about measured rear wheel horsepower, not at the shaft.

    On a dyno, Lightening the rotational mass decreases the force needed to spin the drum, resulting in increased v measured rear wheel horsepower.

    Remember, Once a bike is moving, the energy of the system has two components, the translational (moving part) and the rotational turning part (the wheels). The rotational mass calc is exponential, so the weight is much more of a factor than the sprung weight.

    THe importance of reducing Wheel weight is well understood in the road racing community. Racers know that the single most important thing where you want to save weight is in the rims and tires. In addition, the wheel weight makes the bike handle and feel much snappier.

    For example, if you put carbon fiber rims on a 1200gs, you would see an increase of about 5-7 hp on a dyno at some point in the curve (nearer the lower rpm range).
    #17
  18. Anorak

    Anorak Woolf Barnato Supporter

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    Yes, acceleration, but acceleration isn't horsepower. The mass of the drivetrain doesn't change the amount of horsepower at the rear wheel. On a real brake type dynamometer not an inertial one the mass of the drivetrain will have no effect at the measured horsepower at the rear wheel. An inertial dyno measures acceleration and derives the horsepower from that.
    #18
  19. PRW

    PRW living @ 11.5740741uHz

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    +1 :nod

    The unsprung wheel weight differences will certainly affect acceleration and braking, but humidity has a huge effect on engine performance, smoothness and acceleration, for sure. And in my experience, there is typically a huge difference between TX and CA humidity levels.

    I ride two Chicago - CA round-trips/year and keep the '08 in NCal all winter. The lower relative humidity of CA makes for a much better running engine overall, as compared to most Spring/Summer days in Chicago. It's gotten to the point where I can essentially detect the RH levels, based on how my bike is running... :D
    #19
  20. Texmoto1

    Texmoto1 Adventure Berzerker

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    Several reasons:

    1. Dont have the time off for the added time it would take. My money at this point is worth less than my time so its better to Fly-Rent-Ride. I would rather Spend my available time riding where I want, rather than droning on some hwy trying to get to where I want to ride!

    2. That ride from TX to California can SUCK at this time of the year!
    #20