856 sealed bearing snag

[Simon]

 I've Just started looking into how to convert an 856 s/arm pivot to run on sealed bearings but I've hit a snag,I'm wondering how any of you may feel about how I propose to overcome this,firstly I would like to do this conversion on my old 856 but it is just a commuter bike for my wife now and I cannot justify any outlay or time off road,I'm just looking into the feasability out of interest,now to the problem,as I wish to keep things simple I was going to base the design on my 4500 conversion (using a through shaft),but here's the problem when you strip out the 856 pivot you'll notice a drilling each side a short distance into the frame of approx 22mm diameter to locate the pivot bearings,fine so far,now the hole that allows the the retaining bolt to go through the frame is curiously drilled offset but large enough to allow the M6 bolt (thats fitted to my 856) to go through the 22mm hole centrally,so how would anyone feel about machining through the frame pivot so the diameter was 22mm all the way through   to me there looks to be plenty of material to work with,yes sounds drastic but it looks simple job for a precision engineering shop,don't blame anyone who runs to the hills and says don't let him near my bike though ;)I've been asked a few times about this conversion thought I'd start looking into it,next I'll be needing someone brave (mad)enough to let me do it :-[Simon. [smiley=laughing.gif]

[tmaybee]

Hey Simon.  I just pulled apart my 955.  It doesn't look the way you described your 856.  The hole in the middle is not offset.  It is probably about 1-2 mm smaller radius than the holes for the axles on the outsides.

Could you make 2 axles similar to the stock ones do that they bolt together but have the ends smaller to fit the bearings?

You could have one bolt going through one of the axles and into the other.  This would hold the axles in the frame and the bearings on one of them.  The other axle would have to be threaded at the end and fitted with a short bolt to hold the bearings on that axle.

Does that seem like it would work?

Trevor

[Simon]

Hey Simon.  I just pulled apart my 955.  It doesn't look the way you described your 856.  The hole in the middle is not offset.  It is probably about 1-2 mm smaller radius than the holes for the axles on the outsides.

Could you make 2 axles similar to the stock ones do that they bolt together but have the ends smaller to fit the bearings?

You could have one bolt going through one of the axles and into the other.  This would hold the axles in the frame and the bearings on one of them.  The other axle would have to be threaded at the end and fitted with a short bolt to hold the bearings on that axle.

Does that seem like it would work?

Trevor

Hi Trevor,I'd say that mine has the same drilling as yours but just not central,probably its a manufacturing fault on mine,
I did looking into making 2 suitable bearing carriers but they would need a reasonably thick external flange to stop them pulling through (I wouldn't trust the inner radius to prevent them pulling through),these would have to have a dia larger than the s/arm pivot so they won't fit,as yours has a central inner drilling this makes a big difference,I suppose there could be made 2 half shafts , 1 threaded which then could butt up together internally in the smaller hole, then stepped out in the 22mm dia portion of the frame and continuing out externally at 12mm dia to carry the bearings,sounds good to me but won't fit mine ,but if everyone elses are like yours (please let me know) thats how I'd go,Thanks Simon.

[racetype9]

I checked my 856  and it is also drilled offest.  But, the bearings seat well and the bolt doesn't bind when feeding it through.  

The thought of precision pivot's are awesome, but I think I'll ride it awhile before surgery.  

Simon, thanks a million for the due diligence on it.  

Also, thanks to the board for the tip in the pivot rebuild kit. I picked it up from the LBS ($31!    ) and put it together. After a fresh coat of paint and some new bits, It's reborn.  Rides sooo nice.  I threw on a Fox rear shock while I wait for the Risse and the total weight comes in at 25.4 lbs.  I put a pic in the file section. Hope it loads...

[racetype9]

I checked my 856  and it is also drilled offest.  But, the bearings seat well and the bolt doesn't bind when feeding it through.  

The thought of precision pivot's are awesome, but I think I'll ride it awhile before surgery.  

Simon, thanks a million for the due diligence on it.  

Also, thanks to the board for the tip in the pivot rebuild kit. I picked it up from the LBS ($31!    ) and put it together. After a fresh coat of paint and some new bits, It's reborn.  Rides sooo nice.  I threw on a Fox rear shock while I wait for the Risse and the total weight comes in at 25.4 lbs.  I put a pic in the file section. Hope it loads...

[Simon]

I checked my 856  and it is also drilled offest.  But, the bearings seat well and the bolt doesn't bind when feeding it through.  

Thanks for the info,what I need to know are all 856's machined with an offset drilling on the worldcup frame ,could it be that the 856 was mass produced in taiwan, but was not the 955 & 956 produced in the USA   not sure can someone enlighten me,if so this could account for this anomoly,Simon.

[tmaybee]

I need to know are all 856's machined with an offset drilling on the worldcup frame

I just checked my 856.  It is drilled in the center the same as my 955.  From looking at it, I can't see how it can be drilled offset.   The axles have to go into a hole in the frame that is centered.   From what I can see, if the holes (that the axles fit into) were drilled offcenter, you wouldn't be able to fit the axles into the frame... unless the axles were made offset as well.

I am confused now

How many "steps" are there to the hole in your frame?  There are 2 sizes on mine:  the size that the axle ends fit into the frame  and then a smaller size that goes directly through the frame.   Is it this smaller size that is offest?   I REALLY wish I had a digital camera.   [smiley=groucho.gif]

Trevor

[Simon]

The holes for the bearing (axles) are centred its the hole further in that is off centre,the one that allows the bolt to travel through the frame,there is only 1 step per side but the lip is larger one side to the other hence offset to the bearing (axle) hole location,Simon  

[tmaybee]

Ok, I gotcha now.  

Then both my 955 and 856 are drilled on center.

Trevor

[Simon]

Ok, I gotcha now.  

Then both my 955 and 856 are drilled on center.

Trevor

Thanks Trevor, looks like I've got a bit of head scratching to do ,must of been a QA problem [smiley=redface.gif] thanks again Simon.

[mach_y]

I know this is an old thread, but since I am doing my conversion (I thought this weekend), I just found the inner shaft hole on my 856 is offset as well... of course I realized this after I had the new hollow bearing shaft made.

I am going to drill it out... wish me luck!

Ok, I gotcha now.  

Then both my 955 and 856 are drilled on center.

Trevor

Thanks Trevor, looks like I've got a bit of head scratching to do ,must of been a QA problem [smiley=redface.gif] thanks again Simon.

[Simon]

I know this is an old thread, but since I am doing my conversion (I thought this weekend), I just found the inner shaft hole on my 856 is offset as well... of course I realized this after I had the new hollow bearing shaft made.

I am going to drill it out... wish me luck!

Ok, I gotcha now.  

Then both my 955 and 856 are drilled on center.

Trevor

Thanks Trevor, looks like I've got a bit of head scratching to do ,must of been a QA problem [smiley=redface.gif] thanks again Simon.

Blimey this is a very old thread and I'd forgotten all about it.
Anyway be carefull if your drilling the frame out to have a central hole because then you would need to have the through shaft diameter made to suit the new hole size.
Simon.

[mach_y]

I went ahead and did it...used a 1/2 inch metal drill, which is slightly smaller in diameter than the spec'd shaft.  Could have just had it made out of 1/2 diameter to start with, oh well   I used the sandpaper and drill trick to make the shaft diameter a little bit smaller at a time until it was a perfect fit.

All looks great!!  Thanks Simon for the great writeup

I know this is an old thread, but since I am doing my conversion (I thought this weekend), I just found the inner shaft hole on my 856 is offset as well... of course I realized this after I had the new hollow bearing shaft made.

I am going to drill it out... wish me luck!

Ok, I gotcha now.  

Then both my 955 and 856 are drilled on center.

Trevor

Thanks Trevor, looks like I've got a bit of head scratching to do ,must of been a QA problem [smiley=redface.gif] thanks again Simon.

Blimey this is a very old thread and I'd forgotten all about it.
Anyway be carefull if your drilling the frame out to have a central hole because then you would need to have the through shaft diameter made to suit the new hole size.
Simon.