Aluminium Swinging Arm

[Simon]

Thanks to the forum my carbon swinging arm on my 4500 is fixed, however ever since I've had this bike and that is from new I've found the back of the bike quite flexy especially on fast single track this can some times put you of your intended line, I know this should be expected with a carbon frame combined with a long carbon swinging arm however I know some of you out there have fitted an aluminium swinging arm have you found any improvements? Is it a straight forward fit (same shock length etc?) I'm using a hammerhead disc adapter will this fit the aluminium swinging arm ? what K2 model or models does the aluminium swinging arm come from?does anybody have this concern or is it just me?

[Matno]

No can do. (At least I don't think so). As far as I know, the carbon frames used the pivot bushings (same as the aluminum frames from 98). Later aluminum frame models (which used aluminum swingarms) switched to bearings instead, which are not compatible (although I think one person posted here that he did make it fit with some machine work).

As for the flex, it's just something to live with on the carbon swingarms. I've never ridden the aluminum ones, but we have 3 '98 5000's in my family and they're all the same. I got used to it on mine after about a month, and now I actually like it (it helps to absorb some of the shock on off-center landings). Never noticed or heard that it causes noticeable extra wear...

If you get a frame with an aluminum swingarm, you won't need the Hammerhead adaptor anymore. They come with disc mounts.

Does that answer your questions?

[Simon]

Thanks for your reply, I've had the bike for 4 years so I'm used to the flexy nature of the bike however, I've recently tried a Orange Sub 3 on my local trails and it was fantastic no flex and it went exactly where you pointed it, excellent climber slightly heavier & less travel though, but enought for what its desiged for, I'm just trying get some of those lower flex features on my bike I think it could of made a difference.

[numbnuts]

 I have just switched from carbon to alum on my Evo and I can definately feel the difference, although I did not mind the flex at all. The swingarm i have has a simple bolt on disc adaptor that came with it

[Matno]

Did your carbon swingarm have bearings or bushings? If they were bearings, I assume you just made the swap, right?

[epac]

carbon swing arms come with bushings, alum. swing arms fromm 99 on come with bearings.

you can take the set up from the carbon and put it on the alum. but you cant take the alum. set up and just bolt it on to with the carbon.

major frame rework needed....

the bolt on disc adapter is a k2 part. the part #is 5996. you should be able to order this from your lbs.



                           ..............peace [smiley=nod.gif]

[RoentgenRanger]

Actually, I have a '98 4000 frame and I replaced the carbon swingarm with the Al one without much difficulty(other than the @#%$#%^ quad rings).  The Al swingarm was the earlier version that required the bolt on disc adapter.  I used the same bushings/seals that were on my carbon swingarm and it fit just fine.

[Di.R.T.]

I may be wrong, but I can't believe the carbon swingarm is that squishy compared to the al swingarm.  

If you're comparing the Al arm with roller bearings against the carbon with bushings, that would make a big difference.  Put the same bearings or bushings on each, and I doubt you'd notice any slop difference.

[Simon]

You'll be amazed how much flex the carbon swinging arm has (there is no slop in the bushings) you can flex the carbon swinging arm with your hands an aluminium swinging arm will by nature be stiffer but this does not necessarily mean better it just depends on the design and application they are used for

[jimbo]

I've recently tried a Orange Sub 3 on my local trails and it was fantastic no flex and it went exactly where you pointed it, excellent climber slightly heavier & less travel though, but enought for what its desiged for, I'm just trying get some of those lower flex features on my bike I think it could of made a difference.

What fork are you using and what fork was on the Orange?

[Simon]

The Orange was using a marzocchi bomber mxc, my K2 4500 is currently using a rockshox sid sl but I have also used a rockshox psylo sl and when I first built it up I was using a pace rc37 fork, I feel the psylo running at a 100mm performed the best but is bit to hardcore and heavy for the type of riding I do mainly climbing and fast single track.

[numbnuts]

I didn't know there was any difference in the bearings/bushings! The lbs who got the alum swingarm swapped it around for me, he did say some minor mods were necessary but it didn't take long so assumed it wasn't much. He said he'd done loads of the same warranty replacements so i trusted his expertise. I wish I'd hung around to see exactly what he did but I was with other guys who had to get other stuff done at different shops in a short time, so just left it and ran.