Stem Height - Cannondale Synapse Carbon

aimnburn

Hi,

I want to lower my stem height so I removed the top cap and stem bolts, removed the stem and moved a spacer from below the stem to above it. Then re-tightened everything in the proper order (headset cap followed by stem pinch bolts).

The headset felt solid with no play. I went for a cycle and everything felt great. It was on my mind that I may not have done it all correctly so I found the manufacturer assembly instructions online and the instructions state that no spacers should be above the stem. So I need to undo what I did.

The steerer and spacers are carbon. So could this be a reason why I should not have spacers above the stem? Does anyone know if I need to look at getting the steerer cut (which I don't want to do as its a very final solution) or do I just need a different type of spacer, an aluminum one maybe, above the stem?

From the instructions -
"Assemble the fork, headset, spacers, and stem without tightening the stem bolts onto the head tube. When the system is assembled, the carbon steerer tube should be 2-3 mm below the top of the stem. All spacers must be located below the stem and within the maximum stack height as shown. No spacers may be used above the stem."

Thanks

Lumen

I don't know why they advise that. It's completely normal (even recommended) to have one small spacer above the stem to spread the load around the top cap.

Spacer material doesn't matter at all. Just needs to be the right size.

edit: maybe they mean don't put the conical spacer above the stem. That would be bad, obviously, though I did ride mine around like that for a few days before I cut the steerer.

cajonlardo

Cannondale and Specialized are among the companies who specify this.
Their reasoning is the load on the compression plug rather than concern for the fork steerer

Edit: also some stem manufacturers also specified no spacers above, no idea why

aimnburn

Lumen wrote: »

I don't know why they advise that. It's completely normal (even recommended) to have one small spacer above the stem to spread the load around the top cap.

Spacer material doesn't matter at all. Just needs to be the right size.

edit: maybe they mean don't put the conical spacer above the stem. That would be bad, obviously, though I did ride mine around like that for a few days before I cut the steerer.

Thanks for the reply Lumen.

So do headset manufacturers always recommend having no spacers above the stem? Is that just said to cover themselves but is generally ignored? I've left the conical spacer where it was.

One thing I did notice when I re-assembled was that I was able to loosen the top cap when everything was tightened up. I fixed that by just tightening the top cap by hand (not the bolt that was already tight). I put it down to the fact the spacers were above the stem. It is tight now and I cant loosen it again by hand but I'm a bit anxious about the whole thing.

I don't want to mess up the carbon steerer by applying pressure where it shouldn't be - i.e. above the stem. I also don't want a headset/stem failure on a 70kph plus descent. That would really ruin my day

aimnburn

cajonlardo wrote: »

Cannondale and Specialized are among the companies who specify this.
Their reasoning is the load on the compression plug rather than concern for the fork steerer

Edit: also some stem manufacturers also specified no spacers above, no idea why

So does that mean that there needs to be sufficient length between the stem and the steerer tube for the compression plug to work? In this case what options do I have to lower the stem?

The assembly instructions state a maximum stack height but they don't specify a minimum one.

H.E. Pennypacker

They want you to have the stem clamping onto the area of the steerer that's supported internally by the compression plug. There seems to have been some issues where users clamped the stem onto an unsupported area of the steerer and damaged it. For carbon steerers such as those used by Canyon, the steerer isn't internally supported so the issue doesn't arise.

You should tighten the forks against the headset bearings using the compression plug and then the stem should be tightened against the steerer in that order. You shouldn't really be loosening and tightening the top cap once you've tightened the stem.

A torque wrench is a good idea too.

cajonlardo

aimnburn wrote: »

So does that mean that there needs to be sufficient length between the stem and the steerer tube for the compression plug to work?

Yes. If have time to google Cannondale spacers above stem you will find a fair bit. But that is essentially what Cannondale are saying.

aimnburn wrote: »

In this case what options do I have to lower the stem?

Officially , they say you cut the tube. In reality I can't see how this works. If you were completely certain that you needed to lower it by more than 1,2, or whatever spacers you could cut and then fine tune with the final spacer? Riding around very close to your optimum and then remove and cut to final height?

One last thing, years ago I emailed cannondale Support with a headset query and the got back quickly. I have since recommended this to a couple of people who also got quick responses. Maybe ask for their advise?

darkvalley

Interestingly I have the opposite issue with my Trek. I wanted to raise the stem on my Trek Domane and there is a 5mm spacer above the stem. Trek however advice that a 5mm spacer is required above the stem.

"2. Use spacers above and below the stem- always. This is not as obvious as over torquing, but riders must have a minimum of 5mm and maximum of 40mm of spacers between the stem and the headset. In addition, a 5mm spacer is required above the stem. These spacers prevent the stem from creating a stress riser on the steerer."

aimnburn

cajonlardo wrote: »

Yes. If have time to google Cannondale spacers above stem you will find a fair bit. But that is essentially what Cannondale are saying.


Officially , they say you cut the tube. In reality I can't see how this works. If you were completely certain that you needed to lower it by more than 1,2, or whatever spacers you could cut and then fine tune with the final spacer? Riding around very close to your optimum and then remove and cut to final height?

One last thing, years ago I emailed cannondale Support with a headset query and the got back quickly. I have since recommended this to a couple of people who also got quick responses. Maybe ask for their advise?

Some great advice there, thanks cajonlardo

aimnburn

I've got it sorted. The compression assembly has adjustable length. So you just need to make sure the expander rests at the bottom stem clamp. This means that when you tighten the stem the steerer is protected by the opposite pressure of the compression assembly.