K62, no skiddoo

Going round a steep, downhill bend last week, I came perilously close to losing the front wheel when I had to brake sharply. Fortunately I straightened the wheel out before I lost it completely, but it left me less than enamoured with the dodgy Chinese tyres that come with the bike. Part of this may be down to the added weight of those two extra batteries, but it left me feeling that the tyres really were something of a weak link on this bike, and so I set about looking into a quality replacement.

Others reported having gone for a slightly wider fitting, and the “Continental Zippy” was mentioned a few times. But I couldn’t find this in the wider fitting so settled on the Continental K62, a close relative also referred to as the “Zippy 3”. As usual, I ordered on-line, and one was soon on its way.

A few days later it arrived and I immediately dashed over to the motorbike shop to get it put on. I even drove there and just took the wheel off in front of the shop. My heart sank a bit when the bike guy I’d asked to refit it said “it’s bigger than the other one, it’ll probably not fit and rub against the mudguard”, but my impression of the pretty sizeable gap (and the veracity of people’s reports in the forum of this tyre-size being fine) won out and it went on without any trouble at all.

It is indeed bigger in diameter as well as width, – the old one is about 390mm, but the new one is more like 430 or 440. But this has two good side effects:

  1. They look more chunky and a bit more respectable (despite my reservations about the lack of swirlies), and actually raise the ride height by and inch or so. The mudguards were clearly placed where they are with bigger tyres in mind, IMO.
  2. I noticed straight away that the speedometer’s accuracy is not quite as wildly overstated. It now seems to be more like 12-14% out, rather than the 17-20% it was before.

The most important thing, though, is the sure-footedness of the ride. There was a brittle, precarious quality to the ride before, and the sense that the bike would quickly betray me unless I treated sharp bends or uneven surfaces with the greatest respect.

Even with just the one tyre on, it feels much more forgiving now, reminding me of a similar experience with an old VFR400 I had many years ago. After a spill in wet conditions I took advice and changed the very poor, (again) Chinese – tyre on the front wheel for something of much greater quality, and it immediately transformed the bike’s handling. This reinforces the old adage about the tyres being the most important part of the bike. Rubbish tyres mean rubbish handling.

So even though the tyre was pretty inexpensive, it still feels substantially better than the chunk of cheese that it replaced, and I’m nothing like as nervous about leaning into bends more than a tentative few degrees from the vertical.

So I also plan to replace the back wheel with something of equal caliber. But I have concerns about the impact of the larger size on the acceleration, particularly with that rather too gentle ‘soft start’ that makes pulling away from a full stop a little too leisurely for my likes. But the effect of that extra 4cms or so is very much open to debate. Is the “soft-start” purely dictated by speed, as given by the motor’s hall sensor, leaving that side of the acceleration pretty much unchanged, or will its impact be noticably adverse? Does an extra 10% diameter also up the top speed by a similar amount?

So this is definitely one for the debating chamber. If a bigger tyre on the back might upset the apple-cart, then I can always settle for something of a similar size instead…

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One Response to K62, no skiddoo

  1. hohisilver says:

    That’s an interesting point, I’d not considered the effects of larger tyres on acceleration/top speed. My guess is that the soft start won’t feel that much different, normal acceleration will be slightly reduced, and top speed may even be reduced a little. Although the theoretical top speed will be higher, it also depends on the ability of the controller to supply the extra current to turn the larger wheel. Just my opinion of course, I may be totally wrong!

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