Pogostick Continentals and Vibrating New Series

I'm using Continental Grand Prixs on my APB. These roll very nicely and are very light, but I've had my fair share of problems with them.

Firstly, one burst during my commute about 2 years ago. I wasn't going very fast, the inflation pressure was about perfect, I hadn't hit a pothole, and I wasn't carrying a load when the sidewall on the rear tyre blew out.

I was tempted to ditch them there and then, but I thought it was a once off and that it would be a mistake to write off any product, especially a tyre, based on one possibly freak occurrence so I bought a replacement and a spare.

Then late last year, when I put them on my Rigida Xplorer rims I got a pogo stick effect due the tyres not making a near perfect circle. It affected both front and back and made the bike unrideable.

I spent hours trying to get the bead to sit correctly on the rim, without success.

I partially solved the problem when I discovered that a medium width rim tape had been used when the wheels were built when a narrow tape would have been more appropriate.

The rim tape sat under the bead in places and not in others contributing to the inconsistent diameter of the inflated tyre.

What finally made the ride bearable again was the old trick of smearing washing up liquid on the inside of the rim wall, to reduce the friction between the bead and the rim. The bead is then encouraged to move more evenly outwards as the tyre is inflated.

Now the engineer in me did take into consideration that maybe the rims were at fault. I did previously have these tyres on standard Pashley wheels without a pogo problem.
However I also had Schwalbe City Jets on the Rigidas without a problem. It's difficult to say with certainty without an extensive experiment, but while the rims may be a contributing factor, they are unlikely to be the whole of the problem. I must conclude that the tyres are at least part, if not all of the problem.

What has this got to do with the New Series?

Well, on the moultonbicycle list on yahoogroups, there has been talk of a mystery vibration that occurs with Contis on the New Series, that kicks in at around 33km/h.

Well today, while the APB was on the work stand, I noticed the pogo effect again when I spun the wheels. And I noticed that the whole bike started to vibrate significantly at a certain speed. I used the bike computer to ascertain that this happened between approx 34 kph and 44kph. I repeated the the test several times with the same result. I also spun the wheels up to 70 kph, steadied the bike on the stand, and allowed them to slow down, thus ruling out that my hand pedalling motion was inducing any vibration.

the result was the same... Extensive vibration started at 44 kph and stopped around 33.

So are pogo stick contis a problem for others? Are they the reason for vibrating New Series phenomenon?

Anyhow, I have made a commitment to Contis for the time being having a pretty unworn pair on the APB, and a spare pair in the shed. So I'm pretty determined to make them work for me, instead of me working for them as seems to be the case at times!

Koowho TSR Rack

I first discovered Koowho from Japan, when I saw a fellow Moultoneer with a beautiful day rack on his APB.

Now they have done it again, with this gorgeous rear rack for the TSR.

It's made from aluminium, and you have a choice of polished or painted. It's pretty pricey, even before you add in shipping from Japan and customs. But if you gotta have it, you gotta have it 🙂

There's also a front rack.

Summer Bike

It is said that one can never have only one Moulton. My first Moulton (a 1964 Deluxe) was my only Moulton for a while, but it soon found itself sharing the bike shed with other Moulton siblings. I now have 2 Mark 3's from the 1970s, of which one is a town bike, and the other is still being restored.

So I really only have one touring and day ride bike, and that is an APB Fx8. And last night, I finally decided that summer had arrived, and it was time to put it into summer mode.

Firstly I removed the rack and mudguards. If it's wet I tend to take my Mk3 which has mudguards, and these SKS mudguards are pretty much shot at this stage, so off they go. The rack is very easy to remove and reinstall, so I'll put it back on next time I need it. In the meantime, I'll leave it off to save some weight.

In winter I use a SON dynohub with a B+M Lumotec front light. This lights up the road superbly and I've been known to go for a joyride through the backroads of north Meath in total darkness. This has been replaced with an Ultegra front hub, with Rigida Xplorer 24 hole rim.

At the back I'm now running a Shimano Capreo 24 hole and another Rigida Xplorer rim. The Capreo is a 9-26 cassette which gives a great range, and a nice top gear, which is important on a small wheel bike.

On my winter wheels, I'm using Schwalbe City Jet tyres (sadly no longer available in 406 size). These are relatively narrow at 32mm, but are good and sturdy, and have protected me from the puncture fairy for quite a while. For the summer, I am using Continental Grand Prix tyres, which are nice and light weight. I'm tempted to try Schwalbe Stelvios on the APB, but the Contis have plenty of miles left in them, and I also have a few spares, that I really should use first.

Of course, it has been raining all day today, but the forecast is good, so hopefully I'll go for a nice 50km ride later this evening or tomorrow morning... tomorrow is a bank holiday here.

Moulton TSR Racks

The Moulton designed, but Pashley built TSR is a beautiful machine, and a gigantic improvement over the Pashley Moulton APB that the TSR replaces.

[flickr]http://www.flickr.com/photos/moultonbuzz/5137731514/[/flickr]

But one thing that some Moultoneers are not happy about is the rear rack situation. The APB had a large platform rack, which was supported by a strut that extended from the back of the rack to the bottom of the seat tube, near the bottom bracket. In fact most Moulton models since 1970 have had this arrangement.

[flickr]http://www.flickr.com/photos/moultonbuzz/5137729836/[/flickr]

However, soon after the TSR launched, it became clear that the design of the rear triangle seemed to preclude this arrangement. It seemed to take quite a long time for the racks to become available, too. When it did arrive, the TSR rack was supported from above by 2 struts which attach to the top of the seat tube.

[flickr]http://www.flickr.com/photos/moultonbuzz/5137731020/[/flickr]

People I have spoken to don't seem to like this as much as the old APB arrangment, but the concept is growing on me. The APB rack wasn't the most stable, and was prone to shimmy at high speeds. Next time you see one, grab the sides of the rack and see how much you can move them up and down. Having 2 supporting struts must surely improve this situation.

[flickr]http://www.flickr.com/photos/moultonbuzz/5137124759/[/flickr]

Rack pictures are from the TSR accessories brochure from Pashley