Speed check

[peckham_ryu]

I've realised I need to figure out how far off the speedometer is on my cheap little Taiwanese motorbike. So far, I've used a smartphone app to determine what my top speed has been on a journey. That confirmed that the speedo is cautious by more than 5mph, i.e. if the needle says I'm tearing up the highway at 35mph, I actually haven't touched 30 yet.

Anyway I can't find an app that will give me accurate retrospective spot speed over a short distance, and I don't have a way to strap my phone to my handlebars to spot check my speed in real time. But I'm thinking I could just find one of those road signs that tells you how fast you are going, and ride past it a few times until I reach the speed limit according to the sign: then I'll be able to mark up the dial on the speedo in the right place.

So - any suggestions for where there is one of those speed indicator signs, on a stretch of road that doesn't suffer from traffic, and is rider-friendly (as in, not lined with parked cars)? Or, any better suggestions?

[TheArtfulDogger]

Go up to Sydenham hill, ride like the wind towards crystal palace and make a note of the speed you are doing on the dial as you pass the speed cameras... When the ticket comes through the post you will be able to see the speed the cameras claimed you are going at and voila you have your benchmark.

[peckham_ryu]

TheArtfulDogger Wrote:

-------------------------------------------------------

> Go up to Sydenham hill, ride like the wind towards

> crystal palace and make a note of the speed you

> are doing on the dial as you pass the speed

> cameras...

This morning, I rode that bus lane like I was auditioning to take over from Tom Cruise in the Mission: Impossible franchise. The bike was belting along faster than it's ever carried me before!

According to my phone, the very top speed I reached all morning was a totally badass ... 30.2mph. At this rate, I frankly suspect I should just ride as fast as I can all the time, on the assumption it will never be fast enough to trouble the long lens of the law!

[Loz]

If you don't minding spend just under a quid for an app, try Ski Tracks. It's made for skiers (obviously...) but it will show you you maximum speed over a distance. So, sit on 30 for a little bit and then see what the max speed recorded was.

[uncleglen]

I've been meaning to look into a similar discrepancy when using my Tom-Tom. If my speedo says 70mph the sat-nav says 65 mph and in order to get the sat-nav mph to go red I have to nearly be registering 80mph on the car speedo....my daughter says it's because the car speedo is doctored to show a higher speed than you are actually doing for safety reasons?

[peckham_ryu]

The sat-nav will be accurate. I had the same issue on my old Ford Focus. I don't think it's that the speedo is doctored - some of them are just a bit rubbish. If I could strap a Tom-Tom to my handlebars I'd be sorted :)

[Blah Blah]

I always thought vehicle speedos were deliberately 10% out. I'm guessing so that people who think they driving at the limit are actually just below.

[TheArtfulDogger]

Why not get someone to follow you in a car with a passenger using the sat nav to verify what speed you go at past a fixed point in the road

Not 100% brilliant but will do the trick

[DulwichFox]

There are some roadside devices that tell you your speed..

.. just at a loss to point out where one is..

.. think there may be one on Beckenham Hill rd. between Beckenham Junction and Bromley rd.

It displays your speed (car) do not know if motorbikes resister.

DulwichFox

[Townleygreen]

all cars speedometers are set to over-record your speed by about 10%

[uncleglen]

There used to be one on Grange Road just past Crystal Palace on the way to Croydon

[exdulwicher]

Borrow (or buy) a cycle computer. Some are cheap basic ones that use a magnet attached to the spokes but you can get plenty of GPS ones whcih just clip onto the bars with a simple elastic band style mount and they don't need any set up.

[Seabag]

My (evil fume spitting) VW matches the speed shown on my satnav

Are both out by 10% then?

[ruffers]

To Seabag - no, the GPS is generally very accurate, and you appear to have an accurate speedo also.

The 10% on speedo's thing refers to the police allowing a 10% margin of error before prosecution (normally) as it's accepted there are variables up to 10% on a speedo, ie you're very unlucky to get nicked at 76mph on a motorway, 32 in a 30 etc. Most car or bike speedo's err toward over estimation but by no means all.

For Dulwich Fox road side signs do register bikes.

And to finish on the original subject on my motorbike I very rarely need a satnav so don't want a fixed holder. I got one of these https://www.amazon.co.uk/Finn-Universal-silicon-smartphone-mount-bikes/dp/B00D8Z9KPU/ref=sr_1_1?ie=UTF8&qid=1462290711&sr=8-1&keywords=finn+phone+mount meant for bicycles though and it's great, holds my phone just fine at what the GPS has confirmed are, er, 'fast' speeds. Try one of these with a GPS speed app on your phone.

[TheArtfulDogger]

Looks like there is one thing honest about Seabags VW tdi after all, as it's not the emissions test results 😂