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Thread: Handling of lowered GSA vs standard height, part 2

  1. #33
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    Ash, enjoying this thread, yes interrupted by Mr but the thread has a genuine purpose.

    When I started to reading it I thought well if the COG is lower its got to handle better. But there is a bit more to it than that.

    Keep up the good work

  2. #34
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    SteveC glad to see and read normal helpful comments your obviously a biker, yeh back to the point of COG just now winterwise I ride with a sheepskin seat cover a very thick one and that’s just about puts me into the danger zone of on tippy toes if not carefull.

  3. #35
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    Handling of lowered GSA vs standard height, part 2

    The lowered suspension presumably affects wheel travel and ground clearance on the limit. Does it also affect the Telelever geometry? Does it brake dive more or less with lowered springs?
    Wunderlich sell a (very expensive) modified Paralever arm that lowers the back end. Something less silly money might be an idea.
    08 R1200GSA
    76 Suzuki GT750

  4. #36
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    Quote Originally Posted by Ash700 View Post
    Blueranger, I see a forum with a common interest such as motorcycles (especially branded motorcycles) as a friendly place where members can share experiences, pose questions and discuss related issues.
    I agree completely.......

    Quote Originally Posted by Ash700 View Post
    You seem to be one of those people who go out of their way to pick holes and discredit what others say.
    I can see why you perceive this as you do...it's actually intrest in the subject matter not trolling for it own sake.....

    Am I a bit of a keyboard warrior...probably...but not because I just want to piss people off for the sheer fun of it.....what I care about is knowldege and discerning fact from opinion...as a detective something I expect you would also cherish?

    I'm trying to work out whether your knowldege and experience is accute enough to take it (on face value) that the lower GS does handle discernably better and whether you are self ware enough for placebo not be a factor....so in the abscence of repeating the test with a more competent and consistent rider than myself with a datalogger and under double blind conditions......your simple test is all we have to go off...but all credit to you for actually doing it and not just posting a wooly question hoping to get a clear answer..more than some manage.

    I actually get completely where your coming from with the low speed wobble...the funny thing is I find the LC GSA to be significantly better balanced than say the 1150GSA. I also do a lot of filtering with a large top box with 2m worth of 16mm chain in there.....

    Considering both generations have a similar fully fuelled weight..truth be known by the time I'd ditched the ABS module, the CAT and changed the end can the 1150 was probably lighter...but still felt less stable.

    I speculatively put this improvement down to them lowering the COG on the LC and possibly even moving it forward...one thing is for sure the LC feels to me much more sure footed and stable off road, riding ruts was always a challenge for me where as on the LC I feel like I can ride them quick enough to track the centre with confidence.

    I did notice too that the 12LC is harder to get on the centre stand for me.

    Interestingly, I note that the steering angle on the 1150GSA is 26.2, the hexhead is 25.7 the LC GSA is reduced to 25.5......

    The steeper steering angle my well explain why at walking speeds it wobbles all over the place?
    Would also be interesting to weigh the LC;s wheels vs the 1150's wheels as well to see if the angular momentum of the wheels is any different.

    Incidentally, if you assume that the bike is not perfectly in balance between left and right side when perfectly vertical and ignoring the effect of the cylinder position in balance and flywheel rotation, I would estimate that the lower GS would have around a 5% reduction in the overturning moment as a result of the 50mm reduced height....which in simple terms would flip to a 5% reduction in force required to lift the bike back to vertical from leaned over...so if very crudely we then said that 5% in overturning moment translated back directly to kg, you be at about 13kg for a fully fuelled GSA...I'd say you probably notice a light difference like that if you were riding flat out, or if you were carrying 13kg of luggage...nearly a bag of sand and gravel or small child...but I think the wide bars of the GS mask that effect to degree.

    Also, the Wheelbase would be reduce by about 1.5%....not big numbers but definately discernable.

    I am still intrigued by thought process behind thinking the lower bike would be slower steering....

  5. #37
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    I have to confess that I’m assuming that BMW have reduced both ends of the bike by the same amount, but I don’t know if this is a fact. If it is, the trail, rake and castor angles would remain the same (please correct me if I’m wrong). The wheelbase, in theory, would be ever so slightly less, but that would be virtually impossible to detect. A bit like tightening the chain on a bike, lengthens the wheelbase - imperceptible done in increments. I suppose what I’m saying is, apart from the COG being lower, I’m not sure what else would make the difference, as not much else seems to have been changed. Although 263kg (578lbs) sitting 50mm lower is significant.

    I’ve learnt that both bikes bottom out at the same height, which means the lowered one has less suspension travel. That being the case, the spring compression rates and internal damping will have been changed to still allow for the same max load weights. I know that suspension set up is a science and can be a nightmare... which is why I think that BMW have done a brilliant job in getting both bike options to feel so similar. What did I notice... discount the fact that the bike is physically lower and a very slightly firmer ride, the thing that I did notice was a slightly better turn in and tracking in corners. It felt a bit easier to change line mid bend. It was just easier when pushing on in the twisties - less drama if that makes sense?!

    Shame it looks a bit squashed and drags its pegs. Don’t get me wrong, the standard bike is incredible and during times when I’ve had it on track days it has impressed me much more than I thought it would; and that was after getting off my S1000RR. Obviously two bikes in different leagues, but the GSA is a lot more capable than it ought to be. Having ridden nothing but radical sports bikes for past 30 odd years and going straight to a GSA and not being bored with it after nearly 4 years is testament to how good they are. What the hell did they introduce a lowered version for?

  6. #38
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    The other thing to consider is that the Centrifugal force during a turn will obviously compress the suspension, if the lower bike has a more rapid rise in spring rate then proportionally it will compress less in actual mm (hence feeling firmer) depending on the mass balance between front and rear wheels will also affect how much the front or rear compresses.

    I'd wager the front and rear were dropped equally, otherwise you'd have to change steering angle and if I recall when doing my outfit 1" equates to roughly 0.5 degrees, so in dropping the front by fitting a 17" wheel and raising the rear by 1" I effectively adjusted steering angle by 1 degree.

    For simplicity, I'm more inclined to think its easier to have a different shock length for each respective version than change steering geometry.

    As for changing direction mid bend....assume thats by adjusting bars only on constant throttle? is that in tightening and extending the turn radius?

    Edit:

    Would say that on a GSA as your sat upright you'd tend to put weight on the rear more so than a sports bike which would put your weight forward, therefore in theory on a bike with a longer spring, the rear would drop more increasing the steering angle making it feel "heavier"...the lower bike would possibly sit more neutral making the bike feel more "flickable".

  7. #39
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    Quote Originally Posted by blueranger View Post
    I agree completely.......



    I can see why you perceive this as you do...it's actually intrest in the subject matter not trolling for it own sake.....

    Am I a bit of a keyboard warrior...probably...but not because I just want to piss people off for the sheer fun of it.....what I care about is knowldege and discerning fact from opinion...as a detective something I expect you would also cherish?

    I'm trying to work out whether your knowldege and experience is accute enough to take it (on face value) that the lower GS does handle discernably better and whether you are self ware enough for placebo not be a factor....so in the abscence of repeating the test with a more competent and consistent rider than myself with a datalogger and under double blind conditions......your simple test is all we have to go off...but all credit to you for actually doing it and not just posting a wooly question hoping to get a clear answer..more than some manage.

    I actually get completely where your coming from with the low speed wobble...the funny thing is I find the LC GSA to be significantly better balanced than say the 1150GSA. I also do a lot of filtering with a large top box with 2m worth of 16mm chain in there.....

    Considering both generations have a similar fully fuelled weight..truth be known by the time I'd ditched the ABS module, the CAT and changed the end can the 1150 was probably lighter...but still felt less stable.

    I speculatively put this improvement down to them lowering the COG on the LC and possibly even moving it forward...one thing is for sure the LC feels to me much more sure footed and stable off road, riding ruts was always a challenge for me where as on the LC I feel like I can ride them quick enough to track the centre with confidence.

    I did notice too that the 12LC is harder to get on the centre stand for me.

    Interestingly, I note that the steering angle on the 1150GSA is 26.2, the hexhead is 25.7 the LC GSA is reduced to 25.5......

    The steeper steering angle my well explain why at walking speeds it wobbles all over the place?
    Would also be interesting to weigh the LC;s wheels vs the 1150's wheels as well to see if the angular momentum of the wheels is any different.

    Incidentally, if you assume that the bike is not perfectly in balance between left and right side when perfectly vertical and ignoring the effect of the cylinder position in balance and flywheel rotation, I would estimate that the lower GS would have around a 5% reduction in the overturning moment as a result of the 50mm reduced height....which in simple terms would flip to a 5% reduction in force required to lift the bike back to vertical from leaned over...so if very crudely we then said that 5% in overturning moment translated back directly to kg, you be at about 13kg for a fully fuelled GSA...I'd say you probably notice a light difference like that if you were riding flat out, or if you were carrying 13kg of luggage...nearly a bag of sand and gravel or small child...but I think the wide bars of the GS mask that effect to degree.

    Also, the Wheelbase would be reduce by about 1.5%....not big numbers but definately discernable.

    I am still intrigued by thought process behind thinking the lower bike would be slower steering....
    I appreciate the need for things to be engineered and designed - I’m a huge fan of fine engineering. But once it is engineered it then has to be ridden/driven/flown etc., in order to know how it handles and feels. That is all I was doing. It wasn’t a huge scientific test, it was a fairly simple test ride, on the best roads I could find at the time (and they were cold roads too).

    You have thought about flywheel rotation and vertical balance, things I admit I hadn't considered. Accumulatively, I suppose many small factors make a difference, but it is worth repeating that it wasn’t a huge difference I found.

    I have always had a natural interest in mechanics and how things work. I’ve taken many things apart over my lifetime and put them back together, the only thing that eluded me was a typewriter - should’ve made more notes on that one! My profession honed my desire for accuracy, and when I have the time I can be quite pedantic. As well as discerning between opinion, fact and belief.

    I don’t know why I thought that the lowered one would steer slower? Maybe because the one in the shop looked like a chopper in comparison to the standard one I’m used to seeing and assumed it would steer slower because it looked lower at the back than the front. I haven’t a clue what BMW have done to the fork internals, but when I looked closer (after I’d ridden it) there is a difference in the gap between the front mudguard and the beak between the two bikes, so they’ve clearly lowered the front too, which is less obvious visually. Hence the surprise when I rode it - it steered very nicely.

    I’m not actually convinced that such a small percentage change in wheelbase would be that noticeable because these were things I used to play with on track and I personally don’t think that I’d notice such a small change, it’d have to be a slightly bigger percentage change to start feeling a difference. Other things, like steering angles I would notice.

    Ultimately, like most things, it’s horses for courses... but there are very few bikes on the planet that will do what the GS & GSA can do - a horse for lots of courses!

  8. #40
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    Quote Originally Posted by blueranger View Post
    The other thing to consider is that the Centrifugal force during a turn will obviously compress the suspension, if the lower bike has a more rapid rise in spring rate then proportionally it will compress less in actual mm (hence feeling firmer) depending on the mass balance between front and rear wheels will also affect how much the front or rear compresses.

    I'd wager the front and rear were dropped equally, otherwise you'd have to change steering angle and if I recall when doing my outfit 1" equates to roughly 0.5 degrees, so in dropping the front by fitting a 17" wheel and raising the rear by 1" I effectively adjusted steering angle by 1 degree.

    For simplicity, I'm more inclined to think its easier to have a different shock length for each respective version than change steering geometry.

    As for changing direction mid bend....assume thats by adjusting bars only on constant throttle? is that in tightening and extending the turn radius?

    Edit:

    Would say that on a GSA as your sat upright you'd tend to put weight on the rear more so than a sports bike which would put your weight forward, therefore in theory on a bike with a longer spring, the rear would drop more increasing the steering angle making it feel "heavier"...the lower bike would possibly sit more neutral making the bike feel more "flickable".

    Yes, totally agree centrifugal force and compression. It does also seem that the front and back were dropped by the same amounts. I think whether it’s sit-up-and-beg or a sports bike, once the rider is on the bike, weight doesn’t move too much forwards or backwards. The mass of the rider is always on the bike so I’m not sure how it would effect compression of suspension whilst cornering - this is definitely where telemetry would come into play.

    I noticed the effects of steering through the bars to change a line mid bend. On track days we teach steering ‘mid bend’ can be done on the throttle, on any bike. Close the throttle to tighten your line, open the throttle to push you wider - nice when you use it. I would have loved to have taken both bikes on a track to get a real back-to-back feel.

  9. #41
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    I suppose it’s part of BM’s compromise of designing an off-road capability alonside a tarmac touring bike. To be honest with my twin cam I thought they had got the compromise just right. I’ve ridden my daughter’s partners 2017 gsa and it sort of gelled alongside the TC but I’ve not ridden it far to notice much appart from it was heavy. But he does long distance touring through Southern Europe and North Africa so he had lots of heavy stuff in tank bag rear bag so when I tried it it wasn’t a fair comparison with old 2012 TC.
    My old 2005gs had Ohlins and it was very well set up when I bought it and I think ( not sure with old comparisons) it handled the best of the latest bm's I’ve tried lately.
    Don’t know if this gives a true picture but it’s what I think.

  10. #42
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    Handling of lowered GSA vs standard height, part 2

    When you get lowered suspension from Wilbers (on some versions) the spring and travel in the shock itself is the same. The length is lost somewhere in the shock body.
    That risks the wheel hitting chassis so they must have done their homework.
    The more radical lowering has to include reduced shock travel and I assume a shorter spring. However again they provide springs by compression rate so a shorter one has the same dynamics as a longer one.
    IMO the 50mm lower GSA looks dumpy and odd. If I could not use it without being lowered that much, I personally would look for a different bike.
    Saying that when I eventually get the wedge to have mine Wilbered, I’m going for -30mm in suspension length.
    08 R1200GSA
    76 Suzuki GT750

  11. #43
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    Just for clarity.....of itself I agree reduced wheelbase of 1.5% would likely be undectable to all but elite racers. But....cumulatively with a reduced overturning moment of 5% would be detectable (I think )


    In my head, the ease of direction change is more likely down to the "firmer feeling" suspension reducing pitching when the throttle is opened and closed.

    The lower cog would be more noticed when you have to do a sharp turn or a side to side flick.

  12. #44
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    Compared to my previous bike a very basic suspension Yamaha my first two revelations were (1) how the GS will hardly lift itself out of a bend when you power on. You still must consciously counter steer to climb out of the bend.
    (2) weighting footrests makes no difference. Again it has to be counter steered. This is especially useful in side winds as the GS rider gets blown about in the seat, but the bike doesn’t do an auto lane change.


    Sent from my iPhone using Tapatalk Pro
    08 R1200GSA
    76 Suzuki GT750

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