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Old 08-10-2013, 07:48 AM   #931
SOLO LOBO OP
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Quick update: the wrong bushings came in last week, and my forks are with Alex as of today. Should be back riding next week
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Quote:
Originally Posted by Stagehand
your bike is suitably dirty. Well done.
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Old 08-16-2013, 02:17 PM   #932
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Another quick update, and once again HUGE props to Alex and Konflict...

The forks are sitting here in my cube and will be on this weekend.

Alex changed the oil for a lighter weight, changed the low speed damping, did some bushings and seals....

Great service, really nice guy and can't wait to try these out ASAP.

I'd ride over to the Airhead Tech session in GA, but don't think I'd make it... maybe before Brad, but not before the end of the session

Another note: I am going to install these flush with the top of the top triple this time, and add some pre-load to the rear shock spring since it was so far off with the bags on...
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Quote:
Originally Posted by Stagehand
your bike is suitably dirty. Well done.
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Old 08-21-2013, 01:44 AM   #933
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I've just been into the forks again, pulling both sets of mine apart and mixing and matching the best parts into one set, including new seals and wipers. No surprises in both forks and the best of my bushings seem to have a fair bit of life left in them. Having swapped to the sliders from my second set of forks I now have a proper HE caliper bracket (for 320 rotor) rather than my previous cobbled together thing.

I tried really hard to re-shim my forks myself.

I found an Oz suspension tuner who had worked these forks for a HPN style BMW before and he was willing to sell me a pile of appropriate shims and a settings card to get me to where he got and allow me enough spare shims to play around from there.
Stock valving in these forks in his opinion is very insufficient for big heavy bmw's. He described the right shims for these forks as 'more like washers than shims' compared to what we have.

Bumping up oil weight, like I have done, with the stock valving would probably mean the destruction of those stock little thin shims pretty quickly.

New shims arrived this morning but trouble struck this afternoon when the largest OD shims he sent and spec'd for (23mm) wouldn't fit inside my cartridges (which only take a maximum 21mm shim).

So after some head scratching and a phone call and further confusion that mine has delta shims on top of the mid valve, my cartridges are bundled up and will be getting posted to said suspension tuner for him to figure out and send back (generously, at no extra cost it seems).
He felt sure that the WP 50mm extreme forks he did last time fitted a 23mm OD shim inside (at lest that is what his records say) so thinks that maybe there was/is a difference between years?
I don't know... I vaguely recall coming across some information that there were 'WP50mm's' and 'WP50mm Extremes' and that the two might have been slightly different in some way, but I can't remember much of that now...
Both sets of my WP50's are exactly the same inside the cartridges.

My cartridges will be in the mail tomorrow and either way I will end up with re-valved forks and a good little pile of appropriate shims left over to play with.

I also had a nice discovery today that this whole nightmare of a special tool that I don't have (and that I and Solo Lobo for at least two have tried to make up hamfisted substitute tools for) is not actually necessary to get into the cartridge to do things like shorten the forks or get to the shim stacks.



I will try to take a photo next time (too oily this time) but it is really simple and it makes getting into the guts of these forks really quick and easy
(and thus makes the prospect of ongoing DIY re-shimming/fine-tuning a much more appealing proposition):
The base valve is held in the bottom of the cartridge by an internal round wire snap ring. You push the ring out of its groove, pull it out, then if you push the rod down the base valve gets pushed out.
With the base valve out the mid valve and rod poke right out of the bottom of the cartridge and you can do everything you need to do (such as add the spacer to shorten the forks, etc) without ever unscrewing that big awkward screw cap thing.

Clear as mud?

Solo, do you know what weight oil Alex has set yours up to run with? I asked him when he posted in this thread but he never answered. Mine will be set up for 5W at 180mm.
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Old 08-21-2013, 07:58 AM   #934
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Quote:
Originally Posted by ontic View Post
Solo, do you know what weight oil Alex has set yours up to run with? I asked him when he posted in this thread but he never answered. Mine will be set up for 5W at 180mm.
My invoice says "Maxima Light Racing Fork Oil", but don't know which that means... I would guess 5et

http://www.maximausa.com/shopping/in...zCXFBsVHpfUUL2

I ended up pinching my points wire before I could test-ride the re-built forks over the weekend, but have it fixed now... going to sneak in a ride tomorrow!
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Quote:
Originally Posted by Stagehand
your bike is suitably dirty. Well done.
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Old 08-21-2013, 09:27 AM   #935
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Quote:
Originally Posted by SOLO LOBO View Post
My invoice says "Maxima Light Racing Fork Oil", but don't know which that means... I would guess 5et

http://www.maximausa.com/shopping/in...zCXFBsVHpfUUL2

I ended up pinching my points wire before I could test-ride the re-built forks over the weekend, but have it fixed now... going to sneak in a ride tomorrow!
My guy said to always use 5 wt with these forks.
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Old 08-22-2013, 08:13 AM   #936
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Making progress!!

On the inagural ride today with the re-worked forks I noticed that I have front end dive while braking which I didn't have before! That is a good sign.

I also added about 15mm of pre-load to the rear spring and the bike is much more level when riding, although the rear is firmer that I would like... thinking I may need to change the spring.

Now to pack on some more miles to get the forks dialed in.
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Quote:
Originally Posted by Stagehand
your bike is suitably dirty. Well done.
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Old 08-22-2013, 10:18 AM   #937
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Solo, I'll be flying back north for good on Saturday and rebuilding my forks first chance I get, so we'll need to do a swap/comparison at some point.
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Old 08-22-2013, 10:54 AM   #938
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Quote:
Originally Posted by Airhead Wrangler View Post
Solo, I'll be flying back north for good on Saturday and rebuilding my forks first chance I get, so we'll need to do a swap/comparison at some point.
You don't have to ask this guy twice to test-ride your HPN !
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Quote:
Originally Posted by Stagehand
your bike is suitably dirty. Well done.
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Old 08-22-2013, 06:56 PM   #939
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Quote:
Originally Posted by Airhead Wrangler View Post
Solo, I'll be flying back north for good on Saturday and rebuilding my forks first chance I get, so we'll need to do a swap/comparison at some point.


I've been delving into the online suspension 'literature' again, specifically about valving, and the more I read the more complicated it gets... different tuners touching up our forks with different approaches (behind cloaks of secrecy), different styles of shim stacks, our base valves, mid valves, interactions between the base and mid valve... tricky stuff and so hard to compare apples to apples...

I am feeling very at home pulling these forks apart now, and they really are very easy to work on.

Airhead Wrangler, are you re-springing and/or re-valving your 4860's?
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Old 08-22-2013, 10:37 PM   #940
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Quote:
Originally Posted by ontic View Post
Airhead Wrangler, are you re-springing and/or re-valving your 4860's?
Mmmm, not yet. I've got quite a bad case of stiction, so I'm opening them up for the first time just to see what's in there. The spring rate I have feels just about right, so I've got a set of new bushings, seals, and oil waiting on the shelf to (hopefully) cure the stiction and then I'll ride them for a while to see where I need to go from there. These are just a pair of cheap ebay forks that have definitely been rebuilt before (came plastered in stickers from some random dirt bike suspension tuner nobody's ever heard of) so who knows what I'll find inside them.
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Old 08-23-2013, 02:39 AM   #941
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Quote:
Originally Posted by Airhead Wrangler View Post
Mmmm, not yet…
Oh that is right, I remember now. Good luck with that with that stiction.

I've been playing with my spare set of WP50's today trying to figure them out. These have definitely been opened before as well, including a bit of obvious work accessing shims (with wrong socket or spanner size slightly damaging stuff).
Anyway, I've measured what shim stacks I have in this spare set and am wishing I measured what I had in my other cartridges I just sent off for re-valving...





Time to geek out a bit. I think I have got this understanding right, but I won't take offense if I haven't

A few notable things.

Both compression and rebound forks are exactly the same inside and in function except for the adjuster circuit. In other words, they both dampen on compression and rebound- for adjustment: one bleeds oil through through an adjuster on compression stroke (from bottom of midvalve out the top of the damper rod), the other bleeds oil through the adjuster on the rebound stroke (between the top and the bottom of the midvalve/piston).
Both my forks each had exactly the same rebound and compression shim stacks in each.

The midvalve or piston (in both forks) dampens through a shim stack on rebound only and has a lightly sprung float or check plate for compression flow.

The base valve dampens through a shim stack on compression only and has a lightly sprung float or check plate for rebound flow.
More about this later.

A mini tutorial below on how to get into the cartridge easily, bad photos due to garage light and iphone:

First of course:
Remove bolt from bottom of fork, drain oil.
Unscrew fork cap, remove spring and remove the whole cartridge. (all these instructions have more detail earlier and in the manual).

Then go to bottom of cartridge and push the base vale in a bit (it slides up)


which exposes the internal round wire snap ring


push the snap ring out of its groove with a screwdriver, remove it, then push the damper rod down and the base valve slides out and the mid valve on the end of the damper rod comes straight out after it.
At this point you can undo the nut on the bottom of the midvalve- remove the whole piston and shims, then undo the nut on the bottom of the piston rod, then the little spring and you can put the spacer on to shorten the forks (there is a big 'nut' on top of the other end of the piston rod that you can grip with a socket to turn off these smaller nuts on the bottom)


so about 2 minutes after getting the damper rod out of the forks, and with only sockets or spanners, you can already be accessing your shims

here is the base vavle


here is the exploded version with the shims from my spare forks

Spring and check plate----------------------------shim stack


here is the mid valve (mid valve from the rebound side: you can see the hole centre frame- that is where the long adjust needle goes down to and allows oil to bleed through down to the bottom tip of the damper rod)


and exploded and shims again
Spring and check plate----------------------------shim stack



Another point of interest. One mod/improvement I have read about elsewhere that used to get done to these forks is to install an oil check valve in the compression adjuster circuit somewhere- what that does is to keep oil filled up the entire inside of the damper rod rather than letting it pump air up and out at the start of each stroke. Best place for a check valve to me seems to be here- the screwed out end of the damper rod that the midvalve is on


would need to find a very thin simple ball and light spring check valve and drill this out a bit and then set it into the end of that thing above.
(don't worry if this doesn't make any sense)




now, back to the compression and rebound functions in this fork...
in general terms it is said that the midvalve or piston flows around three times the oil as the base valve (due to a range of things I won't go into).
I have read before (also in a link I quoted way back in this thread) that it is a shame to only progressively dampen (ie through a shim stack) on the base valve instead of also doing it on the mid valve.

To repeat, on our WP50's the midvalve only progressively dampens through a shim stack on rebound.
It would however be perfectly feasible to remove the basic spring and check plate and install an actual shim stack (with or without float) to allow the midvalve to progressively dampen on compression and rebound.
The exact same thing could be done with the basevalve, if desired, so that it too progressively dampens on compression and rebound.

All the existing shims for the current shim stacks are 6mm ID (maxing out at 18mm OD- the ID of the cartridge is a bit over 21mm). Both mid and base valve 'checkplate' shims are 8mm ID.
What I am getting at is that if one wanted to play around with replacing the (boring) check plates with (progressive) shim stacks on the mid and/or base valve then one would need to have a second set of 8mm ID shims to play with.


Why have I gone into all this?
These forks really can be tweaked a hell of a lot and set up in very different ways. It sure would be nice to know how different tuners are setting them up.
Things we might want to ask our tuners (who we are paying good money to):
Are they adjusting the shim stacks on both the mid and base valves? Are they changing anything about the checkplates on both these valves, and/or changing this to shim stacks?
If they don't want to publicaly divulge actual specifics of shim stacks used (completely understandable), could they please talk in general terms about what style of stack (crossover, flexibacker, float, etc) and its character (hard, soft, etc) they are using in each valve?



Personally, I don't actually understand the theoretical benefits let alone the real world effects of progressively damping on compression and/or rebound through the mid and/or base valves through shim stacks- what we do have is the option to do any combination of these things.

I won't be publicly divulging the exact details of what gets done to my bike unless the tuner is OK with me doing so- but I do hope to be able to talk in the kind of general terms I have listed. Beyond that I will have a second set of valves to play with and make and experiment with my own settings.

I hope that was of some geeky interest.
I think I need to finally buy myself that Racetech suspension bible!
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Old 08-31-2013, 02:25 PM   #942
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Remembering something Airhead Wrangler said in his thread I took out my axle and checked it over carefully, but didn't see anything.

I reinstalled the axle, only running the axle bolt up to a very light finger tight and gave the bike the bounce test...

low and behold there was significantly less friction. I played a bit with tightening up the axle and axle clamp bolts to different amounts of torque and in different orders and had the front end go from compliant to sticky every time I firmly tightened the axle bolt.

It seems like our WP 50mm front ends are sensitive to the axle bolt torques.

I ended up pulling out my torque wrench going with 20 ftlbs on the axle bolt and 15ftlbs on the axle clamp bolts and plan on getting some miles in on Tuesday.
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Quote:
Originally Posted by Stagehand
your bike is suitably dirty. Well done.
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Old 08-31-2013, 07:45 PM   #943
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Interesting, good catch!
What is your process of tightening? The way the axle slides freely through makes this a very important issue... I'd be interested in the process from the ktm manual but below is the process I have come up with.

a bit of background:
I spent a bit of time pondering this stuff as I was recently turning up some wheel spacers (rotor side, internal hub, other side) for an odd hub that I am building into a 19" wheel.
To my thoughts the critical wheel spacer is 1. the spacer between the fork and the hub on the rotor side (to set the rotor in the right position relative to the caliper), this spacer floats on the axle and sits up hard against the fork lug, then 2. the internal spacer between the bearings(determines correct support/preload on bearings). The 3rd and least critical spacer is the one on the non rotor side, this floats on the axle but sits up hard against a step in the axle- so long as it is not too big there is a large amount of variance this spacer could be (5mm or so) and still work correctly as this difference just gets taken up by the axle sliding further in or out.
All this talk is actually trying to get somewhere...

We want torque on the axle for different reasons, to take out any play between the hub/spacers/axle/bearings or to 'tighten it all up' (and to add enough preload to cover for potential material deformation and such), and secondly to preload the bearings properly. We don't want too little or too much preload on the bearings. We also don't want to pull the forks in out of alignment too much as we will get stiction.
We can adjust this stuff independently.

I am not sure what the right torque figure is for these bearings.
Let us just say it is 20ft/lbs.

I'd suggest something like this: it might be obvious or it might be odd.. I am not sure.
prep: loosen everything, bounce the forks.
1. With both side axle pinch bolts loose, torque the axle bolt to something less than 20ft/lbs- for example something like 15ft/lbs. (this will take up all the play between the step on the axle, the spacers, bearings, and the rotor side fork lug and get very close to proper bearing preload)- it may want to turn the axle a bit but after it tightens up a bit it should grab (mine does).
2. Bounce forks.
3. Torque the non-rotor side axle pinch bolts
4. Final torque to the axle bolt up to 20ft/lbs (this will finish tightening up the forks but won't pull them out of alignment much at all)
5. Torque the rotor side axle pinch bolts.

So long as it is not some other problem such as damaged axle or something, doing a two stage axle torquing like this should allow getting the right torque everywhere required while barely pulling the forks out of alignment.
I am not sure what the final torque figure is meant to be and I am not sure what the best first step torque figure should be (but I suspect to minimise misalignment of the forks the first step should be quite close to the final figure). I haven't measured torques yet and have just been doing this by feel. This is just the process I recently figured out to be my best approach while I was making the new spacers- and it is different to how I was first doing it which I am sure was pulling the forks out of alignment a fair bit.
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Old 09-01-2013, 11:48 AM   #944
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Usually the bearings "float" in the hub.
The spacer in the hub between the bearings usually is a bit (1mm) longer than the edges for the bearings in the hub. (hope you get this don't know how to explain better) in some hubs there is only 1 side with a edge in the hub (G650X front if i remember correctly.
Preloading the bearing is only on the G/S hubs and older (with the conical bearings)
But this is not the point i wanted to make, lol

Why not torque the axle right away to the specs, then push them up and down (or take it for a spin you won't lose your wheel, and if you do you will notice)
And then tighten the axle clamps.
That's how i do it for years now.

The second time you torque the axle it could still move if there was some dirt between something and then your fork legs aren't parallel..
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Old 09-01-2013, 06:17 PM   #945
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Quote:
Originally Posted by Dmaster View Post
Usually the bearings "float" in the hub.
The spacer in the hub between the bearings usually is a bit (1mm) longer than the edges for the bearings in the hub. (hope you get this don't know how to explain better) in some hubs there is only 1 side with a edge in the hub (G650X front if i remember correctly.
Thanks for the education and correction,
although the hub I've just put together is a bit different from my original hub I just copied this other KTM hub as far as spacers go (wider hub and different length spacers, but the same relative to each other). I have a small bit of 'float', maybe .5mm or so for that middle spacer. Torquing up the axle/bearings doesn't do seem to do anything to their action so I think I got it about right... barely. I was wondering why the bearing edges in the hub were not very 'perfect', and that answers it.

Quote:
Why not torque the axle right away to the specs, then push them up and down (or take it for a spin you won't lose your wheel, and if you do you will notice)
And then tighten the axle clamps.
That's how i do it for years now.

The second time you torque the axle it could still move if there was some dirt between something and then your fork legs aren't parallel..
That sounds fine to me, and is just about the way I've started doing it anyway- I torque up the axle almost completely and then at the end just nip it up a little bit tighter. At this point it doesn't feel like this is pulling the forks out of alignment in any noticeable amount, it is ony a few ft/lbs on an already torqued axle.... I also don't see much harm in doing up the rotor side pinch bolts for that push up and down or for a ride... But I take your point anyway, that second torquing up is pretty much useless and is just a remnant habit of the first wrong ways I was doing it
Cheers,

And for the others in the thread, does anyone have the listed torque figure for the axle?
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