Edit: For those interested in these plates, there's a group buy for them here: *OPEN* GB #2: '06-'08 D675 Rear Suspension Correction and/or Ride Height Plates - Triumph675.Net Forums
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Talking about the triangular linkage plates (see attached image). The image is not taken from my bike btw.
I've often speculated that the 675's stock suspension action is too harsh, in that it rises too quickly.
For a quick explanation of what's going on, the swingarm, when the suspension is compressed, rises up. This effectively lengthens the distance between the dogbone mount point to the bike frame, and the top-triangle swingarm mount point. The pivot point between the dogbone and the triangle will move up. The further you compress the suspension, the faster it'll move up, effectively squeezing the rear spring even faster.
This is what makes the bike's rear suspension a rising rate system.
Now, the issue seems to be that you need to give a fair amount of pre-load to the 675 to get it to sit far enough down in the rising rate stroke to make the rear feel more compliant. This is exactly why we have that strange behavior with the 675's rear suspension. To actually make it feel softer to ride, you need to increase the preload. The problem with this of course is that in doing this, you're also eating into your top-out range. This reduces the rear suspension's ability to extend far enough to deal with going over rises well without the rear feeling all "wobbly", or even leaving the road when it normally shouldn't. In a nutshell, some top-out range is a good thing.
So, it would seem to me that the way to "fix" the 675's rear suspension issues would be to lengthen the distance between the two right-hand triangle pivots (the triangle-swingarm pivot, and the triangle-dogbone pivot). This will reduce the rate at which the suspension will rise. We would also need to lengthen the dogbone-triangle pivot and triangle-shock pivot distance correspondingly.
I need to pull out the ruler and do the proper trigonometry math, but it would appear that in leaving the top two triangle pivots alone, but dropping down the dogbone pivot about 2mm along the arc of the dogbone swing should be pretty close to what's needed to soften the action of the rear suspension without altering the ride height of the bike. This should allow for a wider range of supple action before the rate rises and becomes harsh near the top of the stroke.
Anyone messed around with anything like this before? Experiences?
----------------------------------------
Talking about the triangular linkage plates (see attached image). The image is not taken from my bike btw.
I've often speculated that the 675's stock suspension action is too harsh, in that it rises too quickly.
For a quick explanation of what's going on, the swingarm, when the suspension is compressed, rises up. This effectively lengthens the distance between the dogbone mount point to the bike frame, and the top-triangle swingarm mount point. The pivot point between the dogbone and the triangle will move up. The further you compress the suspension, the faster it'll move up, effectively squeezing the rear spring even faster.
This is what makes the bike's rear suspension a rising rate system.
Now, the issue seems to be that you need to give a fair amount of pre-load to the 675 to get it to sit far enough down in the rising rate stroke to make the rear feel more compliant. This is exactly why we have that strange behavior with the 675's rear suspension. To actually make it feel softer to ride, you need to increase the preload. The problem with this of course is that in doing this, you're also eating into your top-out range. This reduces the rear suspension's ability to extend far enough to deal with going over rises well without the rear feeling all "wobbly", or even leaving the road when it normally shouldn't. In a nutshell, some top-out range is a good thing.
So, it would seem to me that the way to "fix" the 675's rear suspension issues would be to lengthen the distance between the two right-hand triangle pivots (the triangle-swingarm pivot, and the triangle-dogbone pivot). This will reduce the rate at which the suspension will rise. We would also need to lengthen the dogbone-triangle pivot and triangle-shock pivot distance correspondingly.
I need to pull out the ruler and do the proper trigonometry math, but it would appear that in leaving the top two triangle pivots alone, but dropping down the dogbone pivot about 2mm along the arc of the dogbone swing should be pretty close to what's needed to soften the action of the rear suspension without altering the ride height of the bike. This should allow for a wider range of supple action before the rate rises and becomes harsh near the top of the stroke.
Anyone messed around with anything like this before? Experiences?
