Raiding Sliders vs Geometry

Rapid Dog · 10:10 AM

BMW Atlanta and others...
There has been more than a few people that have questioned wether raising the tubes up in the clamp, say to put the bars up top, will change the geometry and handling of the bike.
I have to say I do not know.
One member claimed that the BCR fork tubes where longer than the standard S....I'm not so sure that's true.
The sliders (male) are purely neutral as far as length vs geometry goes from what I understand.
I ay be way off here.

Your thoughts...

BMW Atlanta · 09-22-2006, 08:04 AM

Quote:

Originally posted by Rapid Dog
BMW Atlanta and others...
There has been more than a few people that have questioned wether raising the tubes up in the clamp, say to put the bars up top, will change the geometry and handling of the bike.
I have to say I do not know.
One member claimed that the BCR fork tubes where longer than the standard S....I'm not so sure that's true.
The sliders (male) are purely neutral as far as length vs geometry goes from what I understand.
I ay be way off here.

Your thoughts...

You're thinking right.
Fork tubes/stanchions werent longer if I remember correctly but the bike sat taller due to a longer sport front shock with stiffer spring vs standard sport shock and standard shock. So BMW actually has 3 front shocks available for the Boxer cup with 2 variants of the front sport shock.

Rapid Dog · 09-22-2006, 08:13 AM

...as I assumed.
But the other question, does actually moving the sliders affect the actual geometry...any idea?

roger albert · 09-22-2006, 08:18 AM

NO, it has NO effect whatsoever.
That's been well established for several years now,
and pretty well established since before the S came out.
I don't think there have been more than a few questioning
it, and they were all quickly set straight.

You're on the right track rapid, albeit not too rapidly

Rapid Dog · 09-22-2006, 08:24 AM

...jus' checkin', I got a guy who axed the question that's all...he'll be joining us soon..

BMW Atlanta · 09-22-2006, 08:40 AM

short of taking the slider a few inches out of the forks there are no ill effects. One could go overboard and slide the tube 3"+ up and take away alot of rigidity in the leverage aspect and cause some flex shudder under heavy braking because there wouldnt be enought tube in the forks to disperse the load so they would flex more.

roger albert · 09-22-2006, 08:49 AM

Quite the evangelist there Rapid!

Rapid Dog · 09-22-2006, 08:54 AM

...i like to think of myself as a shepherd for wayward and the weary...

ErricZ · 09-22-2006, 10:07 AM

Anyone got side-by-side pics of raised/non-raised tubes? To see the non-effect?

BMW Atlanta · 09-22-2006, 10:11 AM

Quote:

Originally posted by ErricZ
Anyone got side-by-side pics of raised/non-raised tubes? To see the non-effect?

why? short of having the bike on a fixed front axle stand and a camera on a fixed tripod would be the only relative comparison to make of a "non-effect".

Think of it this way, You could push a broom with a 4' handle or an 8' handle but chances are you are still going to push the broom the same either way and one's just going to have a longer handle. The clamps are fixed in relation to the frame as your hands are to your shoulders. Makes no difference how much slider is hanging out in reference to ride height or rake/angle.

ErricZ · 09-22-2006, 10:26 AM

Quote:

Originally posted by BMW Atlanta
short of having the bike on a fixed front axle stand and a camera on a fixed tripod would be the only relative comparison to make of a "non-effect".

Doesn't sound impossible to setup for a pic. BIKE magazine does it with their riding position overlays. *shrug*

I hear you guys talking but I don't see anything other than typed-out "proof". I don't usually believe EVERYthing that I read on the Internet. Not sure why everyone is so adamant about not actually, visually proving (or disproving) the geometry.

BMW Atlanta · 09-22-2006, 10:30 AM

ride on over and I will gladly show you in person on the showroom floor with angle finder and tape measure.

Peter Parts · 09-22-2006, 10:45 AM

Quote:

Originally posted by ErricZ

I hear you guys talking but I don't see anything other than typed-out "proof". I don't usually believe EVERYthing that I read on the Internet. Not sure why everyone is so adamant about not actually, visually proving (or disproving) the geometry.

Fair enough to be skeptical about accepted wisdom.

Here's a way to look at it: if you can raise one stanchion at a time while the other is locked in place, this would prove the geometry hasn't changed. Try it and I think you'll join the majority viewpoint.

A well-known wrench from Pennsylvania wrote me that he has ridden with the S stanchions raised 4 inches to ease back pains. Not sure if this was a long and careful trial or just brief ride but the souce is trustworthy.

roger albert · 09-22-2006, 10:58 AM

Well said Peter. Very good explanation.
Heck, from a geometry standpoint, you could REMOVE a stanchion, or even both. Wouldn't budge the wheel vs frame, which is pretty much the definition of geometry.

But damn, this is a darn simple system with everything out there in the open. You only have to look at your bike for about 30 seconds to prove it. I can see how the uninformed (all of us, to greater/lesser degrees) could debate ECU control algorithms, but this? What's not to see or understand???

signit98 · 09-22-2006, 11:04 AM

>>>Fair enough to be skeptical about accepted wisdom.<<<

...kinda reminds me of a guy who insited that German car companies don't close their productionlines in august!

I am searching for static diagrams on that topic, hev not found any yet...

pmc847 · 09-22-2006, 11:08 AM

ErricZ

On conventional forks you move the fork up (or down) using both top and bottom triple clamps thus moving the frame and motor up or down. On the BMW you only move the tubes using the top clamp only, thus not moving the frame. The only way to move the frame on our bike is to change the length of the shock (same as forks on conventional). Now, if you could move the big tube up or down in the bottom clamp then you would be moving the frame but you can't because the tube is machines to fit the clamp and can not be moved. Simple.

Philip

JonyRR · 09-22-2006, 11:12 AM

well, you can argue endlesslyy and (mastur)debate this endlessly, but the fact is this front end IS NOT!! a stanchion/slider 'convnetional' front end. I didn't believe it myself until I looked closely at the measurements.

The ONLY thing that sliding the fork 'stanchion' tubes up does is to, as bobby said, reduce the internal overlap of stanchion and 'slider'...which, I suspect, if the 'stanchions' came far enough out, would produce some rocking motion as the internal engagement surfaces are shorter.
Mine ARE out at least 3" and that's the ONLY reason I have been cosnidering longer 'stanchions' from Forking By Frank...to regain the internal overlap. I can feel it.
But as far as changing frame or steering geometry, it does not...not one whit.
RAISE the front shock via shims under the top mount and measure the wheelbase befoe and after...you'll get a surprise as the OEM-VS-raised measurement will not be in the direction that conventional thinking says it should.
Unlearn everything you thought you knew about conventional forsk when dealing with telelever.
Wanna really cook some brain cells...throw conventional-fork thinking at a new K bike

...you'll have to drink a BUNCH ot tequila to unscrew your brain from that one

Steve Carlton · 09-22-2006, 11:19 AM

I like to use a fork instead of chopsticks at Chinese restaurants. Don't know if that's helpful or not.

BMWSaint · 09-22-2006, 11:20 AM

So given the geometry stays the same, what changes, if any, happen to a bike's handling with different handlebar setups: low/BCR, middle/SA, raised/Barbacks &/or Wunderlich triple handlebar clamp w/1150R bars, e.g.?

signit98 · 09-22-2006, 11:24 AM

Hey, Erric... I've tried to draw something rather quickly, I hope this will explain it...