Hi, I just bought this bike from offerup knowing it will need some repairs. I noticed some rattling in the front area of the bike when doing a small drop test. Isn’t there usually a screw on that top cap part? It is missing completely. Also I have the ability to rotate the handlebars so that they are not in alignment with the wheel..
I’m brand new to biking and want to repair it myself, I apologize for the lack of bike knowledge/terminology.
by ohgeze
12 Comments
The top cap part is also stuck on there, I haven’t tried clamping or using any force on it yet though. Wasn’t sure if that’s a good idea or not.
You need a few spacers to fill the gap, and a bolt to preload the cap.
I was just reading this, it’ll sort you out: [https://canecreek.com/everything-you-need-to-know-about-headsets/](https://canecreek.com/everything-you-need-to-know-about-headsets/)
I hope that’s not a crack on the back side of the steerer tube visible above the stem.
My suggestion is to find a bicycle collective in your area. They can teach you how to fix anything on your bike at a very reasonable cost. [https://www.bikecollectives.org/wiki/Community_Bicycle_Organizations](https://www.bikecollectives.org/wiki/Community_Bicycle_Organizations)
Do you have a torque wrench? If not you probably shouldn’t proceed until you do.
You should also read or watch some videos about how to install a stem on a road bike.
Once those things are taken care of, remove the top cap and see if you can find a bolt for it at the hardware store or local bike shop. If not, you need to buy a new top cap and expander plug from the bike shop. Probably best to take the bike there with you but not 100% necessary.
I think you should replace the 5mm spacer under the stem with a 2mm or 3mm spacer to reduce the gap between top of steerer tube and top of stem. But it’s hard to be sure about this from the pics provided when it’s all assembled.
Head tube is too long for starters. There shouldn’t be a gap at the top.
Cannondale utilize expanding plugs, my guess is the bits are at the bottom of your steerer or not there completely. Loosen the stem bolts on the side, the stem cap needs to come out, flip the bike upside down and take out any loose bits. Once it’s back together attempt to reassemble your front end, add any spacers you need so the stem cap sits on the spacers not on the steerer.
[The compression plug has come loose](https://www.foresttrekcycle.com/image/foresttrekcycle/image/cache/data/all_product_images/product-3334/bike_headset_expander_05-420×420.png). Just adding a spacer will not fix this
You need to check if there is a crack on the top tube. If not, get a few spacers and watch some videos on how to install a stem on a Cannondale frame. You should also download the manual for the bike from the Cannondale website. There are detailed instructions how to install the headset, stem etc.
If the steerer tube has a crack, see if you can cut the broken part. If it goes to far down you will have to get a new fork.
You’ve only got one speed and one brake?
You’ve got a Bontrager stem on a Cannondale, they’re incompatible /s
You do not have a standard headset topcap. There are some people giving you bad/incorrect advice because they do not know that Cannondale has some unique headsets and expanders.
I think you probably have one of the early models where Cannondale actually used a starnut in a carbon steerer. The “top cap” in those cases served as both a top cap and the support for the stem, and had a single long top cap bolt running through it (they’re longer than most top cap bolts at about 50mm). There’s a picture of how those worked on [page 9 of this manual](https://manualzz.com/doc/31006281/cannondale-systemsix-2006-2008-owner-s-manual). For this type you want the top of the steerer tube 2mm below the top of the stem. The topcap is then tightened like any other to set the preload on the headset. Then the stem bolts are tightend. I know these were in use on some 2007 models, and perhaps on your 2009 synapse as well.
There is another type of cannondale Si that uses an expander plug. These generally have a hex tool broach in the “top cap” (which in this model also serves as a support, but only for the top bolts of the stem) and do not have a central bolt running through the top cap. I don’t see a hex broach in your top cap, so I don’t think this is what you have. [This type is detailed on page 9 here.](https://www.cannondale.com/-/media/files/manual-uploads/manuals/129387_oms_synapsecarbon_en_low.pdf)
What you should do:
Loosen the stem bolts on the steerer even more, so they are barely engaged.
Pull up on the top cap, it should come out with some twisting. If it is a different design, unscrew it anti-clockwise.
Look inside and see if you see a starnut. If so, get yourself a top cap internal socket head cap bolt that’s 50mm long. These are generally M6 x1.0
Press your stem down on the steerer, with front wheel on the ground, so you remove any vertical play in the headset. Observe the distance between the top of the stem and the top of the steerer. if it is ~2-3mm, then you do not need to add spacers below the stem.
Add no spacers above the top of the stem. Leave the stem bolts loose.
Install the top cap and bolt. Preload the headset: https://www.youtube.com/watch?v=lM4iddLaL8I
Once the headset preload is set, tighten the stem bolts to spec. (5.2Nm max) with a torque wrench.
I’m all about DIY, but I recommend seeking the advice of a professional in this case . The steering system on your bike isn’t something you want to leave up to chance. Especially on a used bike with a carbon steerer.