Hi all,

Does anyone know what the cheapest external speedometer is, that:

• Is UK road legal (will pass the Motorcycle Single Vehicle Approval [MSVA] test)
• Is reliable (enough to pass the MSVA)
• Doesn’t relay on the existing gears/mechanics working in the wheel to calculate the speed (i.e. my display works, my problem is with the equipment that actually measures the speed)

I’m guessing the DVLA will not like my idea of simply installing a cheap bicycle speedo on the motorbike?

Thanks

I've been running a bike with a bicycle speedo as its only speedometer for years and it gets through the MOT ok. Set it so it shows speed and total distance travelled. The only other thing you need to do is rig up a light so you can read it at night. I have a vague memory that it's the GPS based ones that they object to.


The MSVA might be different though and I know very little about that.

Just to update this topic, I came across this - https://www.classicautoinnovations.com/classic a day or two back. The web page is aimed at the classic car market but it could equally be used to drive a normal looking mechanical speedo on a bike.

Just in case the web link doesn't work, or you can't be bothered to click through, it's a device that gets your speed from a gps signal but then uses it to turn a cable going to your mechanical speedo. So you could have a normal looking speedometer with a cable going into it (to keep the testers happy) without needing the wheel driven gear mechanism. As the cable comes out of a black box with some wires going to it who knows what it's measuring.

As usual, as it comes from the US, the brexit pound makes it look a bit pricey but hope springs eternal (as they say) that it won't last forever

How do you rig up a light that works?

Thanks

Cheap bicycle speedos don't expect the bike to do 50 mph .. so may not function at speed - thus the legal requirement failure is possible. Sigma ones usually function at speed. Placement of the sensor is critical - you don't want it close to the centre of the wheel but out towards the rim - this maximises the 'open circuit' time minimising the effects of the cable capacitance maximising the possible maximum speed. Don't think about a 'wireless' one - they can suffer from the bikes spark plugs giving off interference.

GPS speedos fail to function in longer tunnels - thus they can fail legal requirements. The tunnel shields the speedo from 'seeing' satellites that the GPS uses to calculate speed. Similar things can happen where tall buildings obscure large portions of the sky.

Of course this assumes the MOT/MSVA tester is aware of the problems and cares.

The easiest way is to have the original equipment functional. Easiest in that testers will recognise it and not question it if it basically functions.

Backofbeyond - thanks for the call out! Classic Speed would certainly solve the issue discussion. You are correct; we designed this product originally for the classic car market, but have found other markets - like motorcycles - that benefit from having an accurate speedometer regardless of the vehicle specifics.

We can't say for sure if it would satisfy MOT requirements as we have not researched these, but would welcome the expert(s) to weigh-in.

As for tunnels and tall buildings: yes, tunnels do cause a drop of satellite lock, however we designed an algorithm to keep a speed in the instance of lock loss. This keeps the recent average speed (last few seconds) displayed on the speedometer through the tunnel / parking structure. If you stop in the tunnel, the speed will slowly drop to zero as the average pulls in the zero speed. Tall buildings have yet to be an issue due to the powered external antenna we use. The issue with tall buildings is they limit the field of view of the sky, thus limiting the number of satellites to lock on. Our GPS hardware tracks 22 satellites on 66 channels simultaneously. Short story - about 10x better than your smart phone! We also use "dead reckoning" to fill in the blanks if needed. This is a basic navigating skill taught to sailors, Boy Scouts, and hikers.

I hope this helps!
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Brian Induni, CEO & Classic Speed inventor
Classic Automotive Innovations