When leaking wheel rims attack
CB500 tyre causes a sticky situation
When seasoned spannerman Paul Knight took this old, but low-mileage, Honda CB500 for an MoT he wasn’t expecting too many issues, but a rare discovery left him feeling deflated.
The owner of A55 Motorcycles in North Wales explained: “The rear tyre was bit flat, so I pumped it up and rode it for its test and it passed no issues. But when the owner came to pick it up that night the rear tyre was completely flat… which was embarrassing as I was the last man to ride it!
“I looked for foreign objects in the tread and found nothing. Although the tyre had plenty of tread, it was six-years-old and so the owner decided to replace it anyway.”
When the tyre came off, Paul found that it was full of slimy gunk. This turned out to be a puncture preventative that the previous workshop had installed. These products have a two-year shelf life, but this bike had been treated six years ago and stood still for more than two years. So when Paul looked closer at the wheel he saw that the product had started to corrode the rim. “It had actually forced a small portion of the tyre clear of the rim and broken the airtight seal, letting the tyre deflate completely. This happened because as aluminium corrodes it expands significantly, forming a white powdery oxide. In nearly 40 years in the trade I’ve never seen this before!”
Paul managed to wipe the rims clean, then get a wire brush on them. The new tyre sealed back on the rim without the need of bead sealant, so no permanent harm was done.