A pivotal problem

[Shaggy]

So I was riding hard (for me) the other day and was doing a few 3 1/2 foot drops.  I started on the way home and noticed that I couldn't shift into the large ring.  I stopped, looked at the front derailleur...no problems there.  Rode a little more, but still the same problem.  This time I saw what was happening.  My pivot had walked to the drive side and was preventing the chain from being able to ramp up onto the large ring.  Why I missed it the first time, I don't know.  
Anyhow, it had moved about 3/8" to 1/2" out, leaving only a small length remaining on the other side.  Had I done a few more drops and not noticed, I would have had a much larger problem.  [smiley=doh.gif]
My questions are this.  #1) Has anyone had this happen before and #2) How would one prevent that from happening again?  
Before loosening the pinch bolts I tried to tighten them to see if that was the problem, but they were tight.  Any ideas?
Thanks...

[Matno]

Which frame do you have? There are some minor differences, but I assume you need to tighten the main pivot cross bolt itself. Different models supposedly have different torque specs (and I can't remember any of them specifically), but it's pretty high (over 200 pounds, or as OP puts it: "til your fingers bleed with an allen wrench"). A dab of loctite might be in order as well...

Look at OP's Jiffy Lube instructions under "How Tos" for more info...
http://idriders.com/proflex/tech/tech_op4.shtml

One thing to be aware of is that at least a couple of EVO frames from Supergo were missing part of the pivot bolt assembly. I doubt that's the case here, but you never know...

[numbnuts]

I had the same thing happen when i first started riding my Evo and I remember that it happened to a few others who got the supergo evo frames at that time. In my case it definately was that I hadn't tightened the pinch bolts enough initially but it has shifted a couple of times since [not 1/2" tho] even with the bolts tight. I don't own a torque wrench so am careful not to over tighten and strip the threads, I probably don't have them quite right. I would just straighten and tighten everything and keep a close eye on the pivot on the next few rides. Like Matno says there may be differences, the K2 site has some good diagrams/details I think.

[Old Proflexer]

shaggy - we need more info

first of all, the pinch bolts should not be 'tight' on some models, but properly adjusted to allot the swingarm to drop or rise slowly by providing slight resistance.

what frame do you have and please be specific what's moved - ?  pics would be good if you can get them up here.

i'm not sure if your bottom bracket housing which is epoxied in in some models has worked it's way loose (moving the spindle and cranks out to the right) or the actual swingarm unit has moved somehow.  i can't imagine a swingarm moving to the right that much near the frame - the basic design doesn't allow for that.  

you may have the pivot design with bearings in which case the pinch bolts need to be loosend, the 'pivot axle' in the middle of it all should be recentered, and the unit readjusted.  go to the 'how tos' section and click on the manual for your frame - instructions on reassembly and adjusting are in the manuals.

such as http://idriders.com/proflex/resources/00_BikeAddendum.pdf

OP

[yves]

Hi Shaggy,

Also happened to me with a 4000RS frame bought from Supergo in 2000.
Turned out the pivot was missing the thread for the pinch bolt  
Had it fix by my local motorbike store, absolutely no issue since then.

Enjoy your ride,

Yves.

[Shaggy]

It's an EVO 4.0; the pivot design has roller bearings inside the frame which support the axle.  The axle runs through the frame and extends approx 3/4" per side to support the swingarm.  The swingarm tightens onto the axle with pinch bolts.
It was the axle supporting the swingarm that moved, not the swingarm itself.  I've recentered the axle and tightened everything back up.
I was just wondering if that was a result of the riding, or not enough force holding the axle in place...

[Matno]

I was just wondering if that was a result of the riding, or not enough force holding the axle in place...

Choice B. That should never happen under ANY riding conditions unless something isn't tight enough to begin with...

[Shaggy]

The manual specs both drive and non-drive side pinch bolts to be tightened to 120 in-lbs.  My math tells me that it's 10 ft-lbs (1ft/12in, the inches cancel).  However, that's relatively meaningless w/o the use of a torque wrench...something I don't own.  Anyone know how much torque wrenches are

[keen]

 I had problems w/ my DM from day one. I pulled the swingarm to polish it (brand new frame) and the drive side pich bolt snapped on removal (crossed from factory) I had a machine shop make custom studs and spacers. To this day I run a bolt thru the axle to maintain side/ thrust pre-load- my pinch bolts just dont hold the axle.

[numbnuts]

Keen, what type of bolt did you use, I imagine one that fits snuggly would be heavy and overkill as the sidways forces that cause the axle to shift are not that great. Did you use a thinner bolt with spacers?
Shaggy
Torque wrenches are expensive, maybe you could borrow or ask a mechanic to check for you, if you use loctite it should remain tight once it's correctly torqued. Or consider splitting the cost with other riders if you have a closeknit riding group, which is my preference. It does seem to have been a common occurence with the Evo 4.

[pedro]

Hello,
I used the same solution keen mentions. My other problem was that my swingarm kept developing play after a ride. Basically what I did was to leave the pivot tightening "special tool" put on tight. The "special tool" is just a long bolt, washers and nut that run through the main pivot axle, applying pressure to the swingarm's removable bushings.
It has worked great and does not seem to cause any damage,
pedro