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For some reason today I started thinking about the rear shock, suspension and pivots. I need a little help understanding the correct terms and functions. I searched for quite a while for an 'exploded view', schematic or diagram of the rear suspension of a specialized bike (my focus is on the 2012 stumpy), but I think almost any of their air/oil shocks would work. I looked at Fox as well.

I think I have figured out that the shock typically has 'eyes' at either end (mine has only one and splits into a yoke around the seat tube on the wheel side).

I believe the eye has a 'DU Bushing' which I think is a friction reducing bushing and is intended to be replaced every so often? I think next there is a 'reducer' that sizes down the hole that has a shaft or spindle to attach to the frame. Is the close to correct?

Sepcialized states 'sealed cartridge bearing pivots' for the pivot points. What were they before? Just a shaft or bushing?

Every once-and-a-while I see something about swaping out for needle bearings. I am imaging this would be for the lower eye on the typical rear shock? Do I have this right?

Lastly, can anyone find a diagram, schematic or exploded view of a stumpy rear shock and pivots???
 

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What year is your bike? Specialized has user manuals online and usually at the end there is a list of parts with views...
 

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I think if I understand you correctly. The needle bearings would potentially reduce friction on the rotation at the shock eyelet but specialized deal with this in a more elegant way, IMHO.
They prevent the rotation at the shock eyelet by a locking key system and instead have the pivot action take place at the end of the clevises where traditional sealed bearings can be implemented.
There's some exploded pictures of shocks in my build threads and the user manuals have exploded diagrams that will help you understand.

edit: the other end of the shock that bolts to the top frame has minimal rotation so not much need for needle bearings there. The clevis attachment end also uses the full diameter of the fox shock mount without spacers etc so no room to add even if there was any rotation.

If you want to look to improve your suspension performance look into better shocks. Push do a Monarch RC3 which issupposedlyastep up on the fox products and came creek have their double barrel air due out soon.
 

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If my checks are right you have a Stumpjumper Comp 2012
You can find the manuals here> Specialized Bicycle Components Just need to pick the relevant FSR year/model
If it is this then it may have the auto sag which changes things slightly but not much.
Most of the latest models have the shock running under the top tube secured by a bush at one end and by the yolk at the other. Some have bushes at both ends.

If you look at the design you will see that the ends of the shock hardly rotate when the shock is compressed. This is due to the yolk (were the bearings are effectively) rotating around its pivot. As such youll not get any benefit from needle bearings. In fact you will probabley find that there isnt a bearing at all.
Compare this to the 09/10 versions where the shock was vertical and you will see in that design that the bearing at the top rotate quite a lot. These are ideal for needle bearings and make a big improvement in freeing up the suspension.

Easiest way to figure out if needles will be of any benefit is to drop the air and see how much the shock moves from its current position ie rotates around either end., My guess is it wont.

Hope this helps.
 
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