[John C Marriott]

Hi Joshua. I read this thread before I attempted to set up my own CR70 rims s tubeless over the weekend. I (eventually) had a successful result so thought I’d share my method.  I didn’t find the project easy but it was my first attempt at a tubeless conversion so perhaps someone with more experience would have found it straightforward.

Method as follows:
1. Clean and dry the tyre bead and rim bed
2. Use Tesa 4289 tape to seal the rim bed. I recommend putting the roll of tape on a radiator for an hour beforehand. It’s inflexible and unworkable when cold. I put on two layers of 25mm tape in one go, going a little up each rim sidewall with significant overlap in the middle.
3. Repeat the above with electrical tape. completely covering the Tesa tape. While the Tesa tape doesn’t allow air through it, it isn’t overly sticky. The opposite is true of electrical tape and it will stop the Tesa tape unravelling or letting air under it at the edges. The flexibility of the electrical tape allows you to go higher up the internal sidewall of the rim.
4. Fit the valves. Pierce the 4 layers of tape with a cocktail stick or similar and the push the value through. Getting an airtight seal here proved to be very difficult, probably because the factory fitted tape on my rims wasn’t fitted very well around the valve area. I wound some PTFE tape around the bottom of the valves to try and get a better seal.
5. Add sealant to the tyre. Use a bit more than recommended (more on this later)
6. Fit the tyre but don’t use a tyre leaver if possible to avoid damaging the tape you’ve just installed. If you stand the wheel up, fit the tyre at the bottom first and work your way up on both sides. Push the wheel down on the tyre at the bottom which will make it slacker and easier to fit at the top.
7. Take out the valve core and inflate with a compressor or ‘airshot’ device. Put your finger over the hole in the valve and replace the core. Spin and shake the wheels to distribute the sealant inside.
8. Hopefully your tyres have sealed and are now looking ok. Attach a track pump with a pressure gauge and inflate them to their maximum recommended pressure. Do they hold the pressure for an hour?  Hopefully so but mine didn’t with air leaving through the valve area an even through the weld in the rim. Give the sealant some time to work. The valves were the biggest pain point for me. Took me ages but I finally managed fix them by unscrewing the ring that secures them on the outside of the rim, which encouraged the sealant to ‘bleed’ (why we used extra), eventually forming a seal. Leave the track pump connected through this process so you can keep an eye on the pressure. Keep turning the wheel 45 degrees every 10 mins if pressure is still being lost so that the sealant finds its way into any little gaps.

Good luck!

[Author]

Posts