Bicycle chain (lower end) vibrates up and down during normal cycling

The threaded collar which holds the valve shaft to the rim has an insert which locates the narrower Presta valve dead centre in the large Schrader-size hole in the wheel rim. So they've got that bit right.

I think both Presta and Schrader valves are fully opened when the relevant hose adaptor is screwed onto the valve stem, depressing the centre pin of the valve, and the only non-return valve is the one in the pump. In both cases, the valve is opened by a centre-pin of the adaptor. My impression is that it takes a lot longer for the electric pump to pump up my wife's tyres through Presta valves than the similar-size tubes in my older non-electric bike through Schrader valves, both being pumped to a similar pressure of around 50 psi. Even the much bigger tubes with Schrader valves in my new electric bike (until the tubes were changed) pumped up more quickly than my wife's Presta ones. The Presta tubes get to about 30 psi fairly quickly than take ages to advance from there to 50 psi.

The only valves with their own non-return valve are the ones fitted to children's bikes in the 1960s and 70s, which had a rubber cuff that surrounded a tube with a hole in the side, that protruded inside the valve stem and the valve could be removed by unscrewing a threaded collar.

Derailleurs have more gear ratios, but it takes a lot more skill to change gear smoothly. The one thing that catches me out is coming up to a junction in a high gear and forgetting to change down in advance so I'm in a low gear ready to set off. It was easy enough to change gear while stationary with Sturmey Archer, and it's the way I'd drive a car, but with derailleur gears you can't do it - well, you can but when you set off there is a lot of graunching as the chain tries to move across while you are applying a lot of torque to set off, so you don't make that mistake very often!

I remember seeing a modification on Tomorrow's World which gave all the rear cogs section of teeth in an arc which was capable of swivelling sideways to make it easier for the chain to move from one cog to the next without external assistance from the shifter to push the chain from one cog to the next. Adds a lot of complexity so I suppose that's why it never became common.

Derailleurs have more gears yes, but they cover no greater range than my old 4 speed Sturmey Archer back in the day..

They are great for racing and recreational use, but anyone who uses a bike for transport is probably better off with the Sturmey Archer

Especially as some combinations of front and rear cogs were near-duplicates and/or were inadvisable because the chain is at too steep an angle (eg innermost cog on front and outermost on rear or vice versa).

My e-bike only has rear (wheel) cogs, and a single cog on the pedal shaft. Sadly a lot of e-bikes (mine included) don't have a really high gear. I find it useful on the rare occasions when I'm able to go really fast (downhill that isn't steep enough just to freewheel) to be able to go into a really high gear to give a bit of extra force without the pedals going at a stupid cadence (rpm). On my manual bike, the largest front cog and the smallest rear one give a nice "overdrive" - too high for level road but useful on downhills.

My bike was advertised as having 10 gears rather than the 8 of the next model down, but these were all at the low-ratio end.

The tolerances on modern shifters are quite good. You could drive for a couple years, without experiencing any anxiety over shifting whatsoever. The modern shift controls use a ratchet, and move the selector the same amount each time. And as long as the gear spacing is uniform, the shifts will be uniform too.

I prefer the click shifters to the "rotate the handgrip" shifter. The handgrip shifter is used on cheap bikes. The click shifters, there's a large lever and a small lever, and the large lever lifts the chain uphill.

The modern shifters screw up, just before the cable snaps. And that's a hint you've only got a few more miles before you'll be stuck in the wrong gear. The cable always snaps, inside the ratchet housing. This is why fussing over the shift cable elsewhere, is a false economy. (The cable will snap, before it gets rusty.)

What you should do though, is oil the moving bits (sideways movement) on the derailleur mechanism, as this keeps the level of force required to shift down a bit. Then the cable lasts longer.

The other thing that modern bikes have, is the gears have been modified for "positive engagement" during a shift. The chain "climbs up the side" of the cluster in one smooth movement.

You can see in this picture, the gear design is "busy" and there is s*it on the side of it. It's hard to say exactly what the function of the little fiddly bits is for. Even the teeth don't have uniform shape.

If you replace your gear cluster, with an inferior lower grade one, the old sound effects come back :-) But that is also how you keep the cost down (unfortunately), of replacing a drive train on a bicycle.

Paul

There was an item on todays Jeremy Vine radio program at midday about shortages. One caller was a bike repairer and he cannot get 9-sprocket chain at all. There is none in the EU. He says he is now paying £50 for this (length unstated) but is having to resort to buying 'cheap chain' for about £10.

Which is completely contrary to my real life experience. I?ve replaced many many chains without changing sprockets without any problems.

Change the sprocket every time if you don?t mind throwing money away but most of the time it?s unnecessary.

Tim

if you could actually buy one now

Sprockets wear. Chains stretch Fat bastards who stand on pedals in high gears stretch chains. Fit bastards who peddle fast and do the miles wear sprockets...

It was bought out years ago. Now based in Holland.

That's where the two/three cog crank gears come in, as you drop the chain 'down' very quickly and in one movement.

If you have the front gears of course. I see the trend of the last few years has been to use a smaller single crank gear.

I wouldn?t describe myself as a fat bastard but I do stretch chains, especially on my stand-up bike.

Tim

Long ago now but.. my summer set up was 52 tooth front ring and 12 back. Care needed not to strip the rear threads!

Allowed me to follow buses/slow lorries inside the displaced air return:-) Not something good to do with wet or icy roads.