K2 / Proflex Riders Group
General => Tech Forum => Topic started by: colinv on August 23, 2005, 06:41:19 am
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What would be a good replacement rear shock for my 959? and does anyone know what the eye to eye is? cheers.
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Risse Astro5 has always been a favourite on this bike,
reasonably light,great performance and custom build,
i2i is 8 1/4" (209mm),
many are now experimenting with propedal shocks
and varing i2i lengths.
for Risse in the UK checkout CVI
www.cvi.co.uk
Simon.
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Cheers Simon, would it matter too much if it was a 200mm i2i shock? or do you have to stick with 209?
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Cheers Simon, would it matter too much if it was a 200mm i2i shock? or do you have to stick with 209?
Personally yes,
my son has a 206mm i2i on his Oz which seems fine,
however I've tried a 200mm i2i on an Evo which is basically the same setup,the guy who owned it liked it,
I couldn't get on with it,felt like I was sitting in it not on it,plus the cranks kept hitting obstacles that never normally posed any problems.
Simon.
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Go longer (up to 220mm on a 5500) rather than shorter than 209mm........IMHO
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Ditto with Colin.
I have gone longer, coil 8.5"x2.5" travel. I likey.
Then I went to an 8.25 airshock x 2 inches travel(via extender).
The airshock is light and infinately adjustable, but stingy on plush. It feels like the old noleen on steroids.
The coilshock is cushy but heavy. If given an ultimatum on either, I would chose the coil and covet a titanium spring.
So I am currently looking for an 8.5 x 2.5 airshock for my Oz to get the best of both worlds. The others will be handed down to the spare bikes.
In Colin's HO,
Terry
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i'm currently getting a custom fox rp3 [210x50mm] built. had a risse genesis, which actually is ok, but i'm assured the fox will make my oz feel like a completely new bike.
rode a kona in the weekend with an rp3 and was reasonably impressed, so we'll see...
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Just out of curiousity, can anyone explain this to me?
I was reading a thread over on MTBR comparing different people's feedback on platform valved rear shocks. I got the impression that some shocks worked better with single pivot bikes, while others worked better with linkage designs. Any idea why this would be so? Seems to me that if the leverage ratio is the same, the shocks should perform basically the same regardless of the frame design. Right?
Oh, and that RP3 looks awesome. Exactly what I would have designed if I had the brains and money to make a custom "do everything" shock. Schweet! 8)
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Just out of curiousity, can anyone explain this to me?
I was reading a thread over on MTBR comparing different people's feedback on platform valved rear shocks. I got the impression that some shocks worked better with single pivot bikes, while others worked better with linkage designs. Any idea why this would be so? Seems to me that if the leverage ratio is the same, the shocks should perform basically the same regardless of the frame design. Right?
No no no. Tsk tsk tsk. :)
Having a comparable leverage ratio isn't an important factor. It's not a factor at all, IMHO.
Take a look at Specialized's FSR design. Linkage with a Horst link (so it's a REAL linkage design, not "just" a faux-bar). Why would you need a stable platform? Theoretically there should be little need for such a thing (don't worry, I won't make a sacrastic comment about Specy's "superior engineering" ;D ).
Now, theory aside - what's the #1 complaint about these bikes? They're usually regarded as being "too active". Check it out, it's legit. The real question is why? Best advice to give an owner with this bike/complaint - learn to pedal smoother/more effieicenty. Now, this isn't to say that the rider is lazy, uneducated or anything negative in any way.
So, what's different about a SP bike? Nothing, when you look at it from the perspective of why a stable platform is wanted..... and needed. It's got nothing to do with leverage ratio. It's all about rider induced pedal input. There's no hard and fast rule to apply when stable platorm is concerned - it's more a necessity of the rider's output.
If you would have asked me if I wanted this on MY bike even just a week ago I would have asked "why would I want to do that?". Different story now.... several reasons, but predominantly - i'm lazy and don't pedal perfect circles. ;) I'm a "masher".
If you really want to try to target the frame design as the main culprit then look at how easily the chain is allowed to affect the suspension's movement. Again, nothing to do with leverage ratio.
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the leverage ratio will almost certainly have a diret relation to the expected shaft speed and damping valving,so its important to get a shock with a leverage ratio that is compatible with your own bike...or am i completely off the wall here?
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I have the predisesor to the rp3. A Float RL AVA. I got the 7 7/8" or200mm leagth and made an adapter to make it longer. Now this worked well because (bear with me because I have lost my drawings) the adapter effectiveately made the shock 215mm. Now on my 5500 I was supposed to run 8mm of sag on a 209mm length shock, so while you are sitting on the bike the shock should be 201mm long. Now the Fox wanted 13mm of sag so that makes 202mm ride height. Now an extra mm or 2 eithe way should be considered well within the relm of personal feel. My adapter is very light and stong. And I put the same shock in my fork as well, which was the expensive/complicated part. They work awsome! I'm sure the RP3 is only that much better. I would love to post my drawings if only I could find them. Good luck
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Jazzclrint,
Brilliant work on that adapter. Post a pic of the front.
Pivoting on the adapter, nice!
Terry
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I'm also looking to replace my rear NR-2 on my 4000. I'm currently looking for a Swinger 3 way but not many with an i2i of 8.25 are available.
I've seen some great extension adapters in the gallery. Can anyone tell me how you built your adapter if you needed one? Did you have it machined or homemade?
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Something no one has mentioned,
by increasing the i2i length and then running increased sag
do you experiance increased pedal feedback as I foundout on my 856 project when I first tried it ???,
only mentioning this as the Oz and Evo bikes
have the dig in system (due to the s/arm pivot point) that Proflex was well know for,more sag = more distance for the s/arm to travel digging in,
or are you riding areas that require more travel and little use of the granny ring hence less likely to notice this phenomenon ???,
just thought I'd throw that into the discussion.
Simon.
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Simon,
The strut bikes such as 857/957/and 856 have a higher swingarm pivot for agressive dig-in than the Oz/Evo line. Long shocks can result in frame jack.
In my case on my Oz, I run the 8.5 i2i Swinger. It has 2.5 inches of travel, so my shock extends 1/4 inch more than stock, and bottoms 1/4 inch more than stock. I run an additional 1/4 inch of sag to get to that sweet spot of no bobbing and no jacking. The reduced jacking comes from the increased sag, and the reduced bobbing comes from the SPV pressure setting I put in the chamber.
Sure people still say that SPV on a semi-active frame design is redundant, but I can tell you that the infinite tunability has allowed me to tune my shocks right in.
Terry
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Hi Terry,
thanks for the info,now I'm unsure about the pivot point because the standard 856 I have and the standard Oz of my son have virtually identical s/arm pivot height distances,now I now the pivot point on the 856 is further back and was moved forward on the 857 (I read once on the RDI site the blurb was,for easier manufacturing process not performance related),so I'm wondering is it the choice and setup of shock that helps prevent pedal induced feedback or eliminate it all together,just curious after my experiances with pedal feedback when I raised the back of the 856,no spv shock on that just a Fox float.
Simon.
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Simon,
I do remember a bike review for a K2. I think it was for the '98 4000 with smartshocks. A change in frame geometry from the 957 noted that the swingarm pivot location was lowered to a more active position. That meant the piivot was moved closer to the bottom bracket. Over damping of the rear shock was mentioned as well, posibblly the reason the bike was fast. But the overdamping prevented bobbing.
As far as the difference between the world cup struted and the "9" series struted frames in my mind was not only ease of manufacture, but a straighter arc path and more access to travel .
Anyway, they are all good in their own right.
Terry