It’s the second Vespa GTS wheel we’ve had this problem with and it’s bloody annoying. Every time you go to ride the scooter the tyres have gone soft and the pressure needs to be adjusted. There are no punctures in the tyre so why does it keep going flat?
The answer is furry corrosion inside the alloy rim. This means that the lip of the tyre doesn’t seal perfectly against the wheel and air can escape slowly from between the tyre and the wheel. On the GTS (the Italjet Dragster is another regular offender) this seems to be a common problem, with one dealer telling us that by the time the third tyre has been fitted to a wheel there is normally some corrosion to deal with. This problem is not restricted just to scooter wheels; it affects motorcycles, cars and vans too. Thankfully this means that there are also solutions available.
Jerome from Readspeed Scooters was good enough to show us how a professional solves this problem.
Tools You Will Need:
Soap water spray, valve core tool, tyre bead breaker, compressor, Emery paper or nylon/carbide abrasive disc, bead sealer solution.
Step 1 – Finding the Leaks
You can do this with the wheel still mounted on the scooter.
The first step is back to school and the soapy water trick you used to find the source of a puncture on your pushbike. Fill a spray bottle (fabric cleaner etc.) with water and washing up liquid and spray around the wheel. Spray the tyre itself, looking for punctures, but also around the valve and the gap between the rim and tyre.
If it is a very slow puncture then it may take time to find but eventually, a foamy beard of tiny bubbles will form. If it’s a corroded wheel then mark the location of the leak on the rim.
Step 2 – Get the Tyre off the Bead
Use a valve core tool to unscrew the core from the valve to release all the air. Next use a bead-breaker tool (find them on eBay) to dislodge the tyre. It is far better to remove the tyre completely but for most home mechanics this is not easy to do. Although we did an article to help you here.
Clean the tyre edge and wheel to find and assess the area of corrosion. Note that this sort of corrosion comes from moisture trapped inside the tyre which Jerome often finds is made worse by certain types of puncture sealant compound or tyre fitting soap. Water can also be added by using compressors with no moisture trap on the airline.
Step 3 – Polish the Corroded Area
Jerome uses a polycarbide abrasive wheel to clean off any loose paint flakes and polish the aluminium underneath so that there is a clean surface for the tyre to sit against. Don’t use anything more aggressive than this because you don’t want to remove good aluminium. It would also be possible to do this by hand with dry Emery paper.
Step 4 – Check the Valve
By default almost every tyre garage will fit a new tyre valve at every wheel change. This is a good opportunity to do the same and clean around the valve hole to make sure there’s no corrosion there.
Step 5 – Apply Bead Sealer
Also paint the tyre bead with sealant.
With the tyre and rim thoroughly cleaned of any loose particles, you can apply a layer of Bead Sealing Compound to both the tyre and the wheel rim. This rubber solution helps to form an air-tight seal in wheels which do not have a perfect surface. Follow the instructions on the tin.
Step 6 – Re-inflate the Wheel
First refit the tyre valve and valve core. When using Bead Sealer it is better not to use tyre soap. This makes it slightly harder to get the tyre to initially seal on the rim so you need a good powerful compressor. Don’t expect to do it with foot pump – you’ve got more chance of a night of passion with the Queen.
Once the tyre has audibly popped onto the bead both sides, readjust the pressure and use the soapy water test to check if all the leaks are fixed before refitting the wheel.
Readspeed offer customers who have tyres fitted there a further free service, which is to inflate the wheels with nitrogen instead of air.
Air is around 78% nitrogen anyway, but by removing the oxygen and the moisture elements and re-inflating the wheel with almost pure nitrogen it makes the wheel far less likely to corrode again. The aluminium can’t oxidise without oxygen to react with.
The Dunlop nitrogen generator that Readspeed use first sucks out the air from the wheel before it is re-inflated with dry nitrogen.
Nitrogen has other advantages such as cooler running of the tyres in high-load scenarios and slower deflation (since nitrogen molecules are bigger than oxygen molecules).
Of course the reality is that most riders will have to adjust their tyre pressures at some time during the life of a tyre, and this will probably be done with air rather than nitrogen. As such, wheel corrosion can’t be completely eliminated, but anything that slows its progress will be more than welcome.
Words, images and video by: Sticky
Thanks to Readspeed Scooters for help with this article.
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