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Old 02-20-2013, 09:04 PM   #76
Phreaky Phil
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On my 1st DR650 I tried some clamps with less offset than the standard one and I gave the bike a headshake at about 100kmh. It caused a shimmy in the bars above that speed and luckily never got any worse. I changed back to stock clamps, shimmy gone.
In theory less offset = more trail = more stable. Right ? ?
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Old 02-20-2013, 09:56 PM   #77
Lornce
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Quote:
Originally Posted by Phreaky Phil View Post
On my 1st DR650 I tried some clamps with less offset than the standard one and I gave the bike a headshake at about 100kmh. It caused a shimmy in the bars above that speed and luckily never got any worse. I changed back to stock clamps, shimmy gone.
In theory less offset = more trail = more stable. Right ? ?
All other factors being equal, that is correct.

Did you alter the ride height when you added the modded triple clamps.

Are you absolutely certain you didn't wonk the adjustment on the steering head bearings when you fitted the non-stock triple clamps.

fwiw, I've got a stock DR650 and it's terribly unstable on soft gravel roads.

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Old 02-21-2013, 12:57 AM   #78
Phreaky Phil
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Originally Posted by Lornce View Post
All other factors being equal, that is correct.

Did you alter the ride height when you added the modded triple clamps.

Are you absolutely certain you didn't wonk the adjustment on the steering head bearings when you fitted the non-stock triple clamps.

fwiw, I've got a stock DR650 and it's terribly unstable on soft gravel roads.

Yeah, all was good with the install. No other changes other than the clamps. Ran with it for a few weeks. I tried the other clamps after riding a mates Yamaha XTZ 660. It felt way more stable in the front I have a DRZ 400 front end on my current DR which is way better than the standard front end.We rode a lot of sandy tracks on the TAT and the front still feels twitchy. We were 2 up with gear, which may not have helped.Maybe to much weight up high. I haven't ridden any sandy tracks solo.
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Old 02-21-2013, 10:05 AM   #79
Dmaster
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Quote:
Originally Posted by Lornce View Post
I've never felt the need for a steering damper on an airhead GS or G/S.
Me nether,.. till i tried one. I just didn't believe the difference.
So i took it off (it wasn't mine anyway)
And from that moment i really felt it helps allot.
Stagehand has one right?
On a (sort of) stock geometry GS/PD he can tell you more.

I run a DRZ front end with DRZ triples.
More trial than stock, less stable than stock .
I don't get it either but it just is.
Tried several things can't get it as good as stock. (raising or lowering the back and/or front)
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Old 02-22-2013, 12:44 AM   #80
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Quote:
Originally Posted by Dmaster View Post
Me nether,.. till i tried one. I just didn't believe the difference.
So i took it off (it wasn't mine anyway)
And from that moment i really felt it helps allot.
Stagehand has one right?
On a (sort of) stock geometry GS/PD he can tell you more.

I run a DRZ front end with DRZ triples.
More trial than stock, less stable than stock .
I don't get it either but it just is.
Tried several things can't get it as good as stock. (raising or lowering the back and/or front)
Try a little forward weight transfer.

.
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Old 02-22-2013, 02:26 AM   #81
Ras Thurlo OP
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Quote:
Originally Posted by Rucksta View Post
Try a little forward weight transfer.
to make the front more 'planted'?

how do you achieve this other than sliding forks down a bit and rebalancing your chopper? or getting into more major engine relocation discussions

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Old 02-22-2013, 02:56 AM   #82
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Originally Posted by Ras Thurlo View Post
to make the front more 'planted'?

how do you achieve this other than sliding forks down a bit and rebalancing your chopper? or getting into more major engine relocation discussions
Yes

Minor swing arm extension

Edit Bit hard on a GS thats the trouble with being monlever centric
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Old 02-22-2013, 08:49 AM   #83
Dmaster
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Quote:
Originally Posted by Rucksta View Post
Try a little forward weight transfer.

.
Stock was the best, so back to stock geometry it will be.
We should finish the triples .
I'm not into swing arm extensions and other stuff on my current bike.

I just don't understand why its getting unstable by making the trial bigger.
Its not how its supposed to be .
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Old 02-22-2013, 09:30 AM   #84
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It's all about the sweet spot.

Quote:
Originally Posted by Dmaster View Post
I just don't understand why its getting unstable by making the trial bigger. Its not how its supposed to be .
Think about a shopping cart caster. Tons of trail, no stability, shakes all over the place sometimes. Now think about your bike and imagine it with the steering stem way the hell out in front of the bike. Now think about the forces on the wheel when you try to turn it. The wheel would be sticking out the side of the bike, unstable as hell, impossible to keep balance. True, it seems like it would keep it more stable in a straight line, but what's really happening is that the amount of trail determines the width of the path that your steering geometry considers to be a straight line. As that path narrows with larger trail, it gets to the point where the path is so narrow that you are never going straight, thus unstability occurs, because, on a bike, you never really are going in a straight line. If you were to plot a fine line from your wheels, it would NEVER be considered even close to straight, you're constantly correcting.

There's a sweet spot between instability from too little trail and instability from too much. This spot ranges from crisp cornering to stability, but at each end is danger. This is of course considering the fact that the sweet spot is different for every bike depending on the rest of the geometry, weight distro, etc.
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Old 02-22-2013, 11:16 AM   #85
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like Dmaster, I have been riding long forks and standard swingarm. In my instance a 80 paralever with marzocchi magnum forks.
The forks are another world but I also find the front jittery in the rough stuff, hence asking about dampers


Quote:
Originally Posted by naginalf View Post
Think about a shopping cart caster. Tons of trail, no stability, shakes all over the place sometimes. Now think about your bike and imagine it with the steering stem way the hell out in front of the bike. Now think about the forces on the wheel when you try to turn it. The wheel would be sticking out the side of the bike, unstable as hell, impossible to keep balance.

are you saying we are are taking this into mud and bitching that it doesn't feel right?


[IMG] photo muddragster_zps53d6d9bc.jpg[/IMG]
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Old 02-22-2013, 12:01 PM   #86
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Quote:
Originally Posted by Ras Thurlo View Post
are you saying we are are taking this into mud and bitching that it doesn't feel right?
Ha, no, but that is a great example of my last sentence. Look at those triples, not much different from your own in terms of offset, no? Yet look at what that does to the trail at such an extreme rake, HUGE trail, yet this is stable for this bike BECAUSE of the extreme rake. This is why people get confused about trail when they see bikes like this that are super stable because of it. With rake like that, all you have is stability and nothing much else. Also, don't confuse rake and trail, very common to confuse and/or correlate the two together. It's a trifecta of rake, trail, and weight distribution (including spring rates) that makes effective steering geometries.

Our bikes actually aren't all that bad at about 28. Take a look at this KTM 250SX-F that I'm pulling forks from:

By my "tracing on a postit on the screen" measurement method , these are at 29, a full degree MORE than our bikes. Yet the HPM triples made to adapt these forks to our bikes have about 14mm more offset. That and the slight increase in rake puts the trail numbers of this ktm at roughly 15-20mm more than our bikes. But like I said, every bike is different. People complain about KTM geometries being hard to turn in. Also, our bikes have more weight on the front, it's distribution and riding position are completely different, so it works. But with less offset and more trail from using the triples off of one of these bikes, your instability issues are understandable.

If you were to stretch that ktm out, and put a bigger engine and gas tank right behind the front wheel, that geometry would be unstable. Most of the weight there is back, on the rear wheel, so they can get that front wheel in the air, and when they land and squish that enormous amount of fork travel down (thus decreasing trail dramatically) it remains stable. It's all about the sweet spot and making it as big as possible in terms of an offroad bike.

But really, our bikes are made for both off and on road use. You're trying to have your cake and eat it too. If you want to make jumps on your beemer, keep the stock dirtbike triples and massage out the instability with a steering damper, that's what they're for and the reason you see so many on dirtbikes. They are easing instabilities from both too much trail on smooth ground, and too little trail when those long, soft forks get compressed. On a road bike, you have a steering damper because the trail is so small that you are trading stability for flickability. A damper makes your sweet spot bigger.

I should also say that this is all purely empirical observation and thinking on my part, I admit that I really don't have any actual experience, I'm just good at spacial reasoning. I'm open to being wrong if someone wants to correct me.
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Old 02-22-2013, 07:34 PM   #87
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I reckon you either nailed it or got so close you could move the thread to perfect line and get a million hits while the bench racers tried to agree on how to pick holes in your reasoning.
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