How-to: Mending the TPU tube - how to make the plastic pellet leak-proof again
Stefan Frey
· 15.11.2024
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Low weight, low rolling resistance, good puncture protection Bicycle inner tubes made from thermoplastic polyurethane (TPU) have some advantages over butyl inner tubes. However, even the thin plastic tubes are not absolutely puncture-proof. We explain here how to seal a hole in the lightweight inner tubes. And, which 3 Rules and special features when patching TPU hoses must be observed.
Preparatory work: Localise the hole
As with the butyl hose, the easiest way to find the defective area of the TPU hose is in a water bath. On tour, of course, you have to rely on your hearing and the fine airflow from the hole. Holes can also be easily felt with sensitive lips. Caution: Only inflate the tube to 0.3 to a maximum of 0.5 bar, otherwise it could burst or become deformed and develop a "bulge".
1. clean the defective area on the TPU hose
Now comes rule & special feature no. 1: The TPU tube must not be roughened. Instead, clean the relevant area with alcohol. Most patch kits come with patches soaked in cleaner. Other alcohol-based solutions will also work, as long as they are not moisturising - this impairs the adhesive effect.
2. apply adhesive
Rule & special feature no. 2: To attach the patches, no vulcanising agent is used, but a Special adhesive similar to a superglue. Do not apply the adhesive too thinly to the tube, as this will make it adhere better, and leave it to work for a minute.
3. press the adhesive patches onto the TPU hose
Press the patch on firmly for about a minute. This does not always work straight away, but more adhesive solves the problem in most cases. After the repair, you should wait about 30 minutes until the connection is properly fixed, then lightly pump the TPU hose at 0.3 bar and fit it.
How is a TPU hose made and what makes it so special? We have all the information about the lightweight hoses summarised in an exciting article.
4. alternative self-adhesive patches
The classic repair kits do not work for TPU inner tubes. However, special sets with self-adhesive patches are also available for plastic tubes. Here, too, the following applies: Never roughen the material around the patch, but clean it with alcohol.
Once the alcohol has completely evaporated, remove the protective film from the patch - the adhesive side must remain clean - and press the patch on firmly and crease-free. Mini-creases can usually be massaged out from the inside out.
Rule & special feature no. 3: Always pump the TPU tube only slightly outside the tyre! This avoids defects. Then carefully pull the inner tube back into the tyre. When fitting the tyre, make sure that the inner tube is not pinched by the tyre bead.
The right patch set for the TPU hose
The classic patches for butyl inner tubes or the practical "glueless patches" do not work on TPU inner tubes. To repair plastic inner tubes as shown above, you need a special patch kit.
Some manufacturers include a few self-adhesive patches with the inner tube. Otherwise, however, all TPU inner tube manufacturers also offer their own repair kits - self-adhesive or with special adhesive:
Stefan Frey
Editor
