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Old 10-04-2012, 01:06 PM   #16
Clay Spinner
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Ahhh... top tips guys. I'll be adding a set of wp 4860 with 300mm travel to the front. Anyone fancy a cold beer while talking this over so I can at least pretend I know what I'm talking about?!?!
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Old 10-04-2012, 01:19 PM   #17
Prutser
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Quote:
Originally Posted by Clay Spinner View Post
Ahhh... top tips guys. I'll be adding a set of wp 4860 with 300mm travel to the front. Anyone fancy a cold beer while talking this over so I can at least pretend I know what I'm talking about?!?!
I use the same fork full length. With a 50 mm longer swing arm.
My rear wheel has 248mm travel. The shock has 114 mm stroke.
For this amount of travel you need to raise the subframe otherwise the tire will hit the seat lock.

Cheers
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Old 10-04-2012, 01:34 PM   #18
Clay Spinner
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Thanks for that Pruster... perfect! If I put all of this together in my head its beginning to take shape! I like numbers as they mean things to me... never was good with words! I'll have a troll back through and find that thread with all of the pics of your bike. I really like the battery placement as well so may try to copy that idea if you don't mind.
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Old 10-04-2012, 01:52 PM   #19
adventure950
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Hi prutser I take it your using a paralever extended set ( which as standard is 50 mm longer than a monolever anyway) up not a monoshock to get those measurements you give as they would involve pushing the mono shaft uj beyond its maximum ability to move upwards or downwards and it would quickly self explode.
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Old 10-04-2012, 01:54 PM   #20
Prutser
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Quote:
Originally Posted by Clay Spinner View Post
Thanks for that Pruster... perfect! If I put all of this together in my head its beginning to take shape! I like numbers as they mean things to me... never was good with words! I'll have a troll back through and find that thread with all of the pics of your bike. I really like the battery placement as well so may try to copy that idea if you don't mind.
On my ST the battery is placed on the original place.
On a R65GS i'm building the battery is under the gearbox.I didn't want to change the exhaust on my ST.
I don't mind someone making the same thing.
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Old 10-05-2012, 12:22 AM   #21
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Originally Posted by adventure950 View Post
Hi prutser I take it your using a paralever extended set ( which as standard is 50 mm longer than a monolever anyway) up not a monoshock to get those measurements you give as they would involve pushing the mono shaft uj beyond its maximum ability to move upwards or downwards and it would quickly self explode.
I'm not using a paralever. So far no explosions
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Old 10-05-2012, 06:20 AM   #22
adventure950
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Hi Prutser, when I did the calculations regarding the driveshaft length and the amount of travel tha Maximum on a 100mm extension was theoretically 260mm doing ( a rough bit of working out 244 at 50mm extension) really would be the maximum travel so to achieve 248 you need to be carefull your not pushing two areas too far. Firstly the uj will be running very tight at those angles, and even though these are extremes if the shaft is revolving at any speed the wear and stress on the joint will be very high. Also the internal dimensions of the shaft tube mixed up with the offset pivot between the uj and the swing arm pivot mean the more extreme the angle the closer the shaft gets to the edge of the internal area of the tube which in turn puts pressure on the UJ and swing arm pivots. This clearance I believe runs out before the above measurements. Which would indicate your drive shaft could well be rubbing on the internal metal of the tube. Both these factors are part of the reason why HPN run a maximum of 240 travel on a 100mm extension and take into account they also machine the internal area of the tube as well as machine part of the the bevel box cup end of the shaft to lighten and reduce the diameter of the shaft which may give them a slight advantage over the standard sizes. I wanted to go a bit safer again and so reduced that travel to 234mm travel in real terms but doubt it would ever get beyond 230. I am not being critical here at all just hope you are aware of the problems that may be encountered and ( i hope are not a problem for you) if your informed you can prevent a failure of the components or damage to your bike or even worse yourself. Jake.
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Old 10-05-2012, 07:14 AM   #23
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Quote:
Originally Posted by adventure950 View Post
Hi Prutser, when I did the calculations regarding the driveshaft length and the amount of travel tha Maximum on a 100mm extension was theoretically 260mm doing ( a rough bit of working out 244 at 50mm extension) really would be the maximum travel so to achieve 248 you need to be carefull your not pushing two areas too far. Firstly the uj will be running very tight at those angles, and even though these are extremes if the shaft is revolving at any speed the wear and stress on the joint will be very high. Also the internal dimensions of the shaft tube mixed up with the offset pivot between the uj and the swing arm pivot mean the more extreme the angle the closer the shaft gets to the edge of the internal area of the tube which in turn puts pressure on the UJ and swing arm pivots. This clearance I believe runs out before the above measurements. Which would indicate your drive shaft could well be rubbing on the internal metal of the tube. Both these factors are part of the reason why HPN run a maximum of 240 travel on a 100mm extension and take into account they also machine the internal area of the tube as well as machine part of the the bevel box cup end of the shaft to lighten and reduce the diameter of the shaft which may give them a slight advantage over the standard sizes. I wanted to go a bit safer again and so reduced that travel to 234mm travel in real terms but doubt it would ever get beyond 230. I am not being critical here at all just hope you are aware of the problems that may be encountered and ( i hope are not a problem for you) if your informed you can prevent a failure of the components or damage to your bike or even worse yourself. Jake.
Thank you Jake,

I'm am aware of those things and using the thin drive shaft.(not the one with the demper)
When I measured the clearance there was still enough room. And not to much (extra) stress on the u joints.
The shock I'm using is even shorter than what I could actually fit on the bike.
I have measured a lot of those swingarms and checked the clearances. Al the bikes had a different amount of travel before something would touch on the inside or the u-joint would be under to much stress.

At the moment I'm putting a bike together with the same length swing arm. And this one will never be able to make the same wheel travel because of the swing and shaft combi...!

I think I was just lucky with the shaft and the swingarm combination i'm using.

What I did do is give the bike more sag. To keep the monolever from jacking(lifting) until the shock is fully extended.

But thanks again for all the data. That might be helpful to a lot of us.

Thanks, Bas
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Old 10-05-2012, 07:23 AM   #24
Airhead Wrangler
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Quote:
Originally Posted by Prutser View Post
I have measured a lot of those swingarms and checked the clearances. Al the bikes had a different amount of travel before something would touch on the inside or the u-joint would be under to much stress.
How are you checking clearance inside with it assembled? Snaking a bore scope in from the trans side?
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Old 10-05-2012, 07:53 AM   #25
adventure950
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Hey Bas, ta for the reply and glad you did not take it the wrong way as I know some folk could easily have mis-interepreted my way of putting it across. I reckon your doing really well I am pretty impressed that you managed to get a few various parts to mix and match so to speak - its interesting as it starts to show the big tolerance variations of the original manufactured parts from BMW.
cheers Jake
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Old 10-05-2012, 08:19 AM   #26
Rucksta
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What adventure950 says is correct and the measurements ring true with my experience..
With the standard rear end geometry, a standard(ish) shock with 90mm stroke
and a 100mmm swing arm extension resulted in a 60mm increase in travel or 230mm total measured at the rear wheel. (no bump stop)
.
Increasing the drive shaft angle particularly the down angle (range of arc) will result in more travel.
A longer stroke shock will allow taking advantage of the longer travel and clearnace problems do arise

There are slightly different approaches to the solution of clearnace and shock length while still retaining
a cush drive shaft rather than going to the solid shaft prefered by HPN.

Hogging out extra metal from where the U- Joint / shaft passes through the curve in the swing arm is a help.
You can really go to town with the die grinder and remove everything you can get to.
This solves the problem with the U-Joint grinding.

The next point of grinding is the cush drive assembly.
A beveled edge on the inboard end of the cush drive spring helps clearance at the rear of the tube.
Preloading the spring with one or two 42mm hardened washers again on the inboard end of the cush
(GS front end has a couple) moves the fouling point and carefull alignment of the swing arm position in the
frame (left / right) lets you find a sweet spot.

The way the swing arm is extended will have an influence on how much travel can be achieved.
Extending straight back will produce less max travel.
Extending back and to the left along the existing line of the swing arm will give more clearance for the cush drive.
Coming back and to the left allows you to run a wider rear tyre (140) but increases the rear wheel offset.
Dave Kellet the frame chiropractor tweaked the offset for me so the wheels align.
How he does it is his secret.

At this point you are chasing the last (practical) 5-10mm of travel.

Maximum shaft angle can be determined by experiment you will feel the point where it grinds and whatever grinds
will leave a witness mark visible on disassembly - modify, assemble, test, disassemble inspect, modify recursively.

The lower shock mount can moved forward approx 20mm to achive max travel on a 90mm stroke shock.
Removal of part of the top lip of the rear footpeg mounting plate is required to accomodate the spring.

This change in geometry maximised the down angle and limits the up angle. (shock bottoms)
Raising the subframe was no longer required.

The angle formed between the swing arm axis and the shock body is now closer to 90 degrees at
full compression resulting in a bit more progression to a stiffer effective spring rate on the big jumps.


I'm back to a std length swing arm with 210 mm travel.
The 100mm extnsion resulted in 270 mm.
I have 80-100,000 Kms of hard use on a driveshaft running at this (extreme?) angle.
No problems with wear in the U-Joint, bell coupling or the cush drive so far.
I'm using a 680 lbs/inch spring.
Std was 390 lbs/inch.
I'm 250lbs + riding gear

For me the whole rationale of jacking up the rear was to level the ride hight with a replacement front end.
I'm finding I use only 225-230 mm travel up front of the available 270mm.
I do use all of the available rear travel and would like to have a little more in reserve for those landings when I don't want to lead with the front.

With the 270/270 suspension setup to use all the available travel the changes in geometry could be extreme requiring a very smooth riding style to control the beast especially at speed.

The point of the suspension upgrade was to allow me to chuck the bike around.
I'm thinking a 250/250 setup on a 75mm extended swing arm,a slightly steeper front end (not so long forks) with a triple clamp offset in the 28-32 mm range would produce a great all round package,


I hope these results and observations help you achieve your own solution that matches your needs and capabilities.
As they say in the infomercial - results may vary.

Cheers
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Old 10-05-2012, 10:45 AM   #27
Prutser
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Quote:
Originally Posted by Airhead Wrangler View Post
How are you checking clearance inside with it assembled? Snaking a bore scope in from the trans side?
I used a frame that I did cut in half ones to shorten a swingarm. And now used it to mount a swingarm and gearbox and see wat kind of room there was for the shaft to move around. This way I could have a good look.
So I did say "measured" but it was more "looked" at the clearances..

Have seen some bikes that had a lot of machining being done on the shaft and the inside of the swingarm just like Rucksta is explaining about. Done by The Boxertoko in The Netherlands.
For riding off road and not leaving the country to far I wouldn't mind the machined bits.
But I tried to build something with the weak parts like the u-joint original. So when necessary I can just order that part nr.and replace it.

Thanks guy's for explaning and sharing all the info.
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Old 10-05-2012, 07:00 PM   #28
Rucksta
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Quote:
Originally Posted by Prutser View Post
I used a frame that I did cut in half ones to shorten a swingarm..
Can you share your swing arm shortening experience?
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Old 10-06-2012, 12:12 PM   #29
Clay Spinner
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This is all really useful stuff.... though its not my thread I for one certainly appreciate the time people have spent writing in it. It'll take me a while before it all starts to make sense absolute sense but it is interesting to hear everyone's experiences.
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Old 10-06-2012, 12:23 PM   #30
Prutser
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Quote:
Originally Posted by Rucksta View Post
Can you share your swing arm shortening experience?
I don't mind to share that. But it might belong in a Hack thread.
I shortened the swingarm for a R100 engine in a R69S frame.
The original 69S drive shaft is expensive and scarce. And I don't want to ruin original classic parts.(frame was already ruined by the previous owner) The mono swing costs 50 with the shaft in it.
Thats why I shortened a mono swingarm so the shaft sticks out enough to reach the gearbox.
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