Rear wheel lock-up? You don't need an electronic speedo....

[lawrence]

Interesting article in this month's Jampot magazine about replacing a chronometric speedo with an electronic one because the owner suffered rear-wheel lock-up.

Rear wheel lock-up happens when the rear axle is assembled incorrectly. You don't need to spend a fortune, just make sure the cup seal holder is inserted the correct way round (it is NOT as the spares diagram).

See http://www.jampot.com/article_read.asp?id=82

[MartinAmes]

BEWARE.

A GPS Speedo (on it's own) is not legal in the UK.
You can have one in addition to your mechanical or electrical one, which have to be connected either mechanically or electrically to the car or bike.

A GPS speedo could loose signal and thus not indicate your speed. UK traffic law states that you must have a working speedometer.
This is why you cannot use your Satnav as a speedo.

The only exception that I could see is, if your vehicle was never originally fitted with a speedometer.

[bob]

It doesn't need to be incorrect assembly of the rear axle .
Many years ago . I replaced the speedo drive gearbox with a new one from AMOC , but not the drive dog . as that was OK .
The new gearbox and the old drive dog it ended up were incompatible causing the whole to bind up .
If the drive dog is an original , then replace that as well .
Rear wheel lock up is a serious brown trouser moment .

[Groily]

What Lawrence says is often right - but the blasted drive boxes don't seem to me to last that long anyway. I must have had a dozen over the years for various bikes, and even if they are greased regularly they don't seem to hang together that well, at least for me.
I thought that electronic gizmo was pretty handy as well as sounding to be more accurate than a typical set-up. Just a bit pricey maybe.
I periodically resign myself to the notion that a speedo is optional, until I can be bothered to replace the drive units, usually when doing tyres or brakes. Usually including reaming out the hole for the axle so the darn things fit at all . . . You get to know pretty accurately how fast you're going - or not! -from engine note and how much the bugs hurt on impact. So far I haven't met a gendarme who fancies giving a bike a road test, to see what he can find fault with.
And here's a serious heresy - I reckon the later magnetic instruments hang together better than chronometrics even if they're less accurate . . . Ducking for cover. But having three of each at the mo, and knowing the problems I've had (ie none with magnetics and endless and expensive with chronos, especially odometers) I can only comment on what I see!

[aeac21]

A simple question:
I am building a trike with a 1961 G80S base on which I grafted a rear quad - so I no longer have an original rear wheel with its speedo gearbox - Do you think I can adapt the electronic speedo with the front wheel ??
Thanks in advance for help - Jean-Paul

[spookefoote1956]

I have seen this done several times on a variety of bikes

[kernow kid]

A simple question:
I am building a trike with a 1961 G80S base on which I grafted a rear quad - so I no longer have an original rear wheel with its speedo gearbox - Do you think I can adapt the electronic speedo with the front wheel ??
Thanks in advance for help - Jean-Paul

Hi Jean-Paul,
There are lots of digital Speedos available, and they rely on a magnet attached to the wheel spoke and a reed relay attached to the fork leg that is triggered every time the magnet passes it. Once calibrated, they work fine. Trickiest part is running the wire from the relay up to the display in a neat way. Very basic is a bicycle type that has its own battery and can be as cheap as £5! Motorcycle displays can even have neutral, main beam and turn indicator light built in, but would need 12v from the bike, negative earth.
Regards kk