In the interest of saving money on my new (road)bike build, I’d like to reuse my Ultegra front mech. It’s currently on an aluminium frame (I’m assuming 31.8 dia)and I’d like to fit it to a steel (28.6 dia)tube. I’ve seen adapters at some online cycle shops for £20! Has anyone use a section of plastic plumbing pipe for this?

Works fine .

Ive used electrical tape in the past with no real issues

Most shimano MTB mechs come with a selection of shims for exactly this purpose. Put a WTD in the classifieds and I expect someone will have them for nowt.

Might fit better on the seat tube.

shimano shim £2.50

The wife’s has insulating tape doing that job. Seems OK. I have a new mech to fit but haven’t got round to doing yet as all is fine.

The bits of rubber you get with a light fitting do the job perfect. Just buy a cheap light from tesco or somewhere.

Was just about to ask the same question 🙂

Bit of old inner tube makes a good rubber shim.