Adjusting stack height.

[Salty seadog]

Good day all,
I am going to play a bit with the stack height on the road bike to find a favoured position. I can move spacers up and down fine to raise or lower the bars so no problem there. My question is regarding the stack (spacers) that will be above the stem once i have found my ideal position.

The frame is a specialized roubaix carbon frame and specializeds' advice in their literature is to not have the stack proud of the stem for too long but to cut down the steerer tube (i think i have that right) so the top cap is flush with the stem again. it seems to sugest that not doing so can affect the headset somehow.

Can anyone confirm this or offer any other advice for experimenting with stack height?

Many thanks,

ssd.

 

[Viking]

Once you have your ideal position and the top cap has been used to preload the bearings and the stem has been clamped to the fork you could remove the top cap and the spaces above the stem without any impact on position safety etc. (assuming are stem torque settings are correct – so it isn't immediately obvious to me why the spacers above the stem would have any impact on the bearing. Those below the stem are another matter, although there is some debate as to how real that effect is.

If it is aesthetics, then it is in the eye of the beholder. In any event, if you do decide to cut the steerer tube be very careful and read the advice on here and elsewhere. Getting that wrong could be very expensive.

 

[Salty seadog]

It seems to be to do with the expander plug not being able to do its job properly....

 

[T.M.H.N.E.T]

An awful lot of bikes come with a stack of spacers below the stem and an awful lot of those will never be altered.

 

[Kajjal]

As above the top cap preloads the headset and the stem then clamps it in place to that position. Spacers above the stem make no difference as they would not be under any great stress. No sure what they are suggesting.

 

[Viking]

It seems to be to do with the expander plug not being able to do its job properly....

The plug can be moved to a position where it aligns with where the stem clamps (to provide internal support to the steerer tube).

 

[T.M.H.N.E.T]

The plug can be moved to a position where it aligns with where the stem clamps (to provide internal support to the steerer tube).

What?

 

[Viking]

What?

The plug can be moved to a position where it aligns with where the stem clamps (to provide internal support to the steerer tube).

 

[T.M.H.N.E.T]

The plug can be moved to a position where it aligns with where the stem clamps (to provide internal support to the steerer tube).

I'm struggling to see how or why not having your entire expander plug inside the carbon steerer is a good idea.

 

[Viking]

I'm struggling to see how or why not having your entire expander plug inside the carbon steerer is a good idea.

If the stem is moved far enough it may clamp the steerer tube in a position that isn't supported by the internal plug. That could put stress on the steerer tube walls which is what I guess the OP is referring to. All depends on how much the stem is moved, the material that the stem is made of and the type/size of plug. I guess it is the usual manufacturer CYA warning.

 

[T.M.H.N.E.T]

The expander plug itself puts stress on the steerer walls, it's function is bearing preload. No?


Either way, my question was related to fitting one correctly, which you seem to be recommending not to do.

 

[Viking]

The expander plug itself puts stress on the steerer walls

which is balanced in the other direction by the stress from the stem clamp.

Either way, my question was related to fitting one correctly, which you seem to be recommending not to do

What a bizarre comment. All recommendations on the placement of expander plugs is that they are fitted in the steerer tube in a position where they can support the steerer tube walls when the stem is clamped. Why do you think this is wrong.

 

[T.M.H.N.E.T]

All recommendations on the placement of expander plugs is that they are fitted in the steerer tube in a position where they can support the steerer tube walls when the stem is clamped. Why do you think this is wrong.

Any expander plug I've ever used in a carbon steerer sat flush with the top of the steerer. You suggested above that it can be moved to support the two stem bolts

 

[Viking]

Any expander plug I've ever used in a carbon steerer sat flush with the top of the steerer. You suggested above that it can be moved to support the two stem bolts

Some fit "flush" with the top of the tube and can't be moved, others (e.g. some Reynolds types) can be positioned in the tube.

In any event, back to the OP, the number of spacers above the stem place no greater or lesser stress on the headset once everything e.g. preload and stem clamping is setup properly.

 

[T.M.H.N.E.T]

Some fit "flush" with the top of the tube and can't be moved, others (e.g. some Reynolds types) can be positioned in the tube.

In any event, back to the OP, the number of spacers above the stem place no greater or lesser stress on the headset once everything e.g. preload and stem clamping is setup properly.

Kudos on the backtrack