What are the advantages of motorbike specific sat navs?

How accurate is the speedo on the Garmin GPS units? I like the look of the Zumo 400 and the digital speedo thing is an attractive feature but only if it's accurate to within 2-3mph!

Originally Posted by teriyakimonkey

All this is very good but what really justifies the extra ?100+ more than a car one? I'll be using it 90% of the time in the van and can get away with a plastic bag if it rains.

Bike GPSs tend not only to be properly waterproof, but also made to resist knocks and particularly constant vibration better than car ones. They also tend to have bigger and brighter screens, which are much simpler to operate with gloved hands and easier to see with the sun on them.

[embee]

Originally Posted by ranathari

How accurate is the speedo on the Garmin GPS units? I like the look of the Zumo 400 and the digital speedo thing is an attractive feature but only if it's accurate to within 2-3mph!

The speed is as accurate as the positioning. In reality it's much more accurate than the speedo, there's no reason for it to be otherwise. Speedos are inaccurate for good reason. If the GPS wasn't pretty accurate it wouldn't work at all, 10% error would be a bit useless! You can rely on the indicated speed to the nearest mph.
Before getting a Zumo, check very carefully exactly what the spec will do, for example bluetooth, maps included, car mount included, Text-to-speech (TTS). The lower spec ones don't have various features. Best value for money has to be the higher spec, the 550 includes both cradles and European maps, b/tooth, TTS etc.

Waterproofness - the Zumo unit itself is rated as IPX7, which is basically submersible, but note that the cradles aren't! You have to be a little careful making sure you keep the connector pins covered if the unit isn't in the cradle for example.

The screen brightness is excellent (and is adjustable), can be set for day or night or auto switching, very good even in bright sun, and the touch screen works with gloves brilliantly. The "buttons" are automatically bigger when it's in the bike cradle than in the car cradle for example.

[TEC]

The GPS speed is only accurate when doing a steady straight line speed, start hooning round bends and the GPS will take a second or two to catch up each time, more likely to show a straight line speed through a set of bends. Like wise it will be inaccurate when climbing or dropping rapidly over hills. I would not trust it to replace the bikes speedo when it matters, e.g. you know there's a traffic car behind you

[embee]

It's probably most useful to mentally "recalibrate" your speedo under reliable steady state conditions, as TEC suggests above. I know that at a GPS speed of 70mph my bike speedo says 75mph for example. 30mph is not far enough out to risk doing anything over the indicated value.

Looking like it's got to be a Zumo then but they cost a lot. Will have a look on Kelkoo.

[TEC]

Originally Posted by teriyakimonkey

Looking like it's got to be a Zumo then but they cost a lot. Will have a look on Kelkoo.

Or GPSW, they do pretty good deals at times and their support is excellent