856 faux bar XC version

[Simon]

Just modified my faux bar 856 to a XC race version,
firstly the origional version was great but I had a couple of issues mainly down to me I add,
firstly I had raised the rear to compensate for any slackening of the head angle as I'm using 4" travel forks,I always maintained I hadn't raised the bike as I always ran extra sag so the ride height was the same as a standard 856 set with standard sag,if you know what I mean [smiley=laughing.gif],
anyway came across a problem (should of thought of this  ) whats a world cup frame renowned for  
yep DIG IN,so what happens to all the extra sag when grinding hard in the granny ring, yes its all used up as the s/arm extends down,no problem with that for climbing but because the s/arm can extend further down you could get this effect in the middle chainring when your hard single tracking,now I can't say for sure this is happening but occasionally I have had the cranks momentarily lock up on me,
you see if you get your bike (stand next to it)and hold the front brake on,lean over your bike and hold the cranks putting a little pressure on the chain,then compress the suspension,what happens   the cranks turn backwards,this is down to the pivot point and I've made this more noticable by raising the rear suspension,on the whole though its still been great but I'm more of a single track/climbing rider so here's the new version plus all the spec's from both versions for you to compare via my linkage simulator,

Origional
Rear travel 143mm
Shock stroke 35mm
BB height 378mm static 292mm rear compressed
             255mm front and rear compressed
Chain growth 32.6mm
Max vertical force at the wheel 632.5 N
Shock compression ratio 4.08 : 1 (TO HIGH)

XC Version
Rear travel 108mm
Shock stroke 35mm
BB height 369mm static 304mm rear compressed
             267mm front and rear compressed
Chain growth 25.8mm
Max vertical force at the wheel 831.8 N
Shock compression ratio 3.05 : 1 (ideal)

sorry for the euro measurements but thats what the simulator uses and I can't be bothered to convert  
Simon.
Ps thats a new strut ( its lighter  )and mountings
so its a 5 min job to convert back

yes thats a converted 855 strut.

[will]

Wowie Kazowie!

That is so cool. This version is even better (IMHO) because it's such a subtle change to a beautiful design.

If I could only...

[Frankd3000]

VERY interesting!!!! Who'd have thunk it, huh?

I'm glad to see you've come across all this. It certainly helps me with my upcoming upgrades. THANKS Simon!!!!

Now, a few Q's;

1) the predominant contributing factor for the "bobbing" effect (I can't think of a better word right now) is the ride height, correct? This is just a simply case of physics and their relation between the height of the BB, the location of the (main) pivot and the position of the rear wheel (also the front, but .... too much tech right now  [smiley=laughing.gif] ).

2) you altered the shock compression ratio with just the re-location of the strut mount-to-s/arm position, right? It looks like you have the same linkage piece in place through both versions, right?

Awesome stuff, Simon - as always.  

[Simon]

Thanks Will  [smiley=beer.gif]

Frankd3000
First Q, Yes your correct, though there's no bobbing effect,by raising the b/b
the pedalling force locks out the suspension (in certain gear ratio's) more than it should but also the suspension action acts against the cranks eg as it compresses its trying to turn the cranks anti clockwise again depending on which gear ratio you happen to be in,this happens on most bikes but raising the b/b the way I did I beleive exaggerates the dig in system,I have still kept a raised b/b but not by very much,if you measure (approx) from the centre of the rear axle to the centre of the top shock bolt standard is around 22-1/4" I set the first version to 22-3/4" and the new version is set to 22-3/8"
bombing downhill  with all that travel is a breeze though,

Second Q, yes your spot on,just made a new strut and fitted extra mounts on the s/arm so I can change back to the other system if I wish,note even more mud clearance [smiley=nod.gif],
I used the linkage simulator before making these changes to make sure everything was positioned correctly and I could get the spec's before any changes,
first ride tomorrow and if successfull I'll be looking into fitting the PUSHed system (threshold damping)to the shock,also testing RDI's new spring kit for a ODS shock I've fitted to my wifes bike.
[smiley=beer.gif]
Simon.

[Frankd3000]

 [smiley=laughing.gif] That's the first thing I noticed in the pics (the new strut). It looks like you have more mud clearance than the original piece, and (obviously) waaaaay more then the s/arm itself. Good show!!!

Sorry, one more Q (I can't help it! A lot of what I see is simply helping me with my next - and biggest - step);

Chain growth - reduced with the XC Version, but only due to the reduction in rwt, yes? I don't see any geometry changes to support evidence otherwise, but just want to be sure.

Good luck with your riding tomorrow!!!!! Hope you will have a blast!

[shovelon]

Simon,

I too like this version too. Maybe the logic behind the geometry made it  look better once I applied it to the result. It looks fast.

Can't wait to hear how the pushed shock works on it too.

Terry

[Simon]

Sorry, one more Q (I can't help it! A lot of what I see is simply helping me with my next - and biggest - step);

Chain growth - reduced with the XC Version, but only due to the reduction in rwt, yes? I don't see any geometry changes to support evidence otherwise, but just want to be sure.

Good luck with your riding tomorrow!!!!! Hope you will have a blast!

Frankd3000 once again your spot on,its just related to the decrease in travel,there's not much you can do about chain growth unless you move the s/arm pivot point,
if your interested here's where you can download the linkage simulator (you need to register on the site first before you can download) the sites not in English but you can translate plus the programme only downloads in English
http://translate.google.com/translate?u=http%3A%2F%2Fwww.mtbcomprador.com&langpair=es%7Cen&hl=es&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools

Terry, yes I can't wait to try the PUSHed system only I've got to save up for it first   but I will get it eventually [smiley=nod.gif]
Simon.

[Frankd3000]

UHHHHHH?!?!??!??!?!?!

Today is yesterday's tomorrow, eh!

Sooooooooooooooooooo? How was it? Don't tell me you couldn't ride because it rained, either. [smiley=laughing.gif] (sorry, couldn't resist that one)

Oh, THANKS for that link. I just registered.

[Frankd3000]

Simon,

Thank you. I love you.
Thank you. I love you.
Thank you. I love you.
Thank you. I love you.
Thank you. I love you.
Thank you. I love you.
Thank you. I love you.
Thank you. I love you.

AWESOME link!!!!!!!!!!!!!!! I'm going to get started on my frame info tomorrow. (why do they have a second set of files to download if they're already in the program?)

[Simon]

Frankd3000
  [smiley=laughing.gif] it was the day before but now its the day after
  beleive it or not we're basking in sunshine

 Anyway yes I've had my first ride and it was awesome,it rode very similar to the origional design
but I didn't get that occasional pedal lockout,also it
felt much more lively when attacking sharp climbs and sprinting,I've yet to determine the best sag setting for me so I ran it quite stiff,even then I'm able to run
lower shock pressure's,
I took with me a standard 856 (my wife's steed)with coilover springs
fitted to the ODS dampers (I'm testing the front for RDI)
to enable me to compere the two,although the springs transform the ODS system the difference between the two is like night and day,here it is at my local park yesterday,yes thats sun you can see through the tree's [smiley=laughing.gif]


Yes thats a very handy programme to have,no idea
why thay have a second programme I just downloaded both,can't remember how I came across it in the first place,the good thing is you can put the picture up of your bike (always use a pic of the right hand side) then when it tells you to click on certain points you can put them in different places to then
see the effects,its great to play around with.

Simon [smiley=beer.gif]