Loose headset? Most modern carbon frames are made by bonding a carbon or aluminium headset cup into the headtube and occasionally this bond breaks. Don’t worry – we can fix it.

Case Study: Masi

This poor Masi came to us with a headset cup which was being pulled into the headtube.  We’ve seen similar issues with both aluminium cups and carbon cups or races.

Bonding aluminium to carbon is really common:  Most “full carbon” frames will have at least one aluminium hardpoint for the dropouts, bottom bracket, suspension pivots, headset etc.  Generally these are trouble-free but if one does come loose we’re able to fix it.

In this case once we got everything apart we could see that very little glue had been used and there was nothing for the glue to bond to.

This Masi has a terrible design with two major issues:
(1) The aluminium insert was press-fit into the carbon headtube.  There was no room for glue.
(2) The aluminium insert was taller than the contact area of the headtube.  What this means is that at the factory any glue which was applied to the insert was squeezed out of the way when installing the insert.

We modified the aluminium insert on the lathe in three ways:

• Reduced outside diameter to give 0.5mm of clearance for the glue to bond
• Reduced height so the insert was lower than the carbon contact area
• Chamfered the top

In the finished repair you’ll see:
(3) Glue between the frame and insert
(4) A really nice glue bond between the top of the aluminium insert and the inside of the carbon frame.

Before and After

In this case the original insert was in good condition with no corrosion so we can re-use it.  If there was lots of corrosion or damage we’d manufacture a new one.

After cleaning off any residual glue we intentionally rough-up the surface of the aluminium to ensure a good mechanical bond for the glue.

We use a tiny endoscopic camera to look inside the frame after bonding and check our work.  Here we can see glue all the way around the aluminium insert – this means we’ve got a full glue bond and it’s not going to come loose again

Alignment is Critical

The hardest thing with headtubes, bottom brackets, or suspension pivots is ensuring frame alignment. If these aren’t replaced EXACTLY in the correct planes then bike performance and rider comfort will be compromised, the frame won’t track straight, and it will chew through bearings.  Our custom jigs allow us to ensure all suspension pivots are bonded correctly and usually to better tolerance than when the frame was new.  I knew those years studying mechanical engineering would come in handy 🙂

Guaranteed work

We stand behind all our repairs 100%.  You can have full confidence that we’ll correctly fix your frame.