Aftermarket speedo and rear wheel?

[P.]

Just a passing thought whilst looking at aftermarket speedos.

If you were say, installing onto a bike which had a 17 inch rear and 19 front, and you kept swapping the wheels for SM wheels, 17 and 17, rather than having to change the speedo to match the new sizes, would you not just be able to use the rear wheel as a permanent pickup?

Obviously requiring a long enough cable, but realistically would that be viable? Can't see an issue directly but if you can do let me know.

[Vincent]

I presume that the front wheel is used generally as the rear can spin. I can't see it making much difference though - might look a bit odd if the wheel spins and the speedo shoots up but it'd soon settle down.

'Front wheel is nearer the speedo too of course.
____________________
Space Is Deep

[weasley]

Gearbox or front sprocket pickup is even neater and the way more modern bikes tend to do it. Yes, your speed 'goes up' if you spin it up but then this happens on cars anyway (still awaiting the snowstorm of doom so I can get out and prove I can hit 30 mph on my drive).
____________________
Yamaha XJ600 | Yamaha YZF600R Thundercat | KTM 990 SMT | BMW F900XR TE

[P.]

Enduro bike, no sprocket covers or anything to mount the other side to, rear wheel and swing arm however provide perfect sizing for the magnet and pickup.

[mentalboy]

Could you not employ a Doovy BBQ gps rig when running on the 17's.

You'd only need it for one run, then note the important speeds and use typex marks on your speedo? (Obviously, fail with a digi speedo!!!)
____________________
Make mine a Corona.

[P.]

Speedo, what speedo

Its purely digital, its going to be used for those errr 1 wheel adventures too, which made me think rear was still possibly the best, I'm not fussed about mega accurate, its only a rough guide so I know in 30/40/50 zones to relax and keep around the limit.

[mentalboy]

So employ gps then remember that 30 is 33, 40 44, etc (for example)
____________________
Make mine a Corona.

[P.]

Ah, remember. There is my flaw, I have a terrible memory which is getting progressively worse, I've forgotten family before, so uhh, yeah. But what about 17/19 and 17/17 wheel setups?

[Northern Monkey]

If it's only for the odd hoon about, then a hand held GPS and a couple of tie wraps?

[_Iain_]

Pushbike speedo, hit the mode button and change wheel diameter when you change wheels. Glue magnet to both sets of wheels.
____________________
Please be aware that the above post may be full of complete nonsense.
Riding: '07 KTM Duke II, Baotian BT49QT-20 Driving: '88 Volvo 340

[lihp]

https://www.wiggle.co.uk/garmin-edge-200-gps-cycle-computer/

Attach to bars, hit go, and done, GPS Speedo so no sensors etc.

Even then download the data later to put onto google maps.

Simple neat, and not expensive
____________________
covent.gardens: lihp is my most favourite member ever

[G]

Surely no self respecting bike has a 17" rear and 19" front .

[P.]

Could have said 18/21

But basically an 18 is closer to 17 than 21 is to 17, so the small difference between 17 and 18 on the speedo will be minimal.

[G]

If you stick a knobbly 18" next to a knobbly 21" there's not a massive amount of difference as the rear is not only fatter, but tends to have bigger knobs.
A 17" rear road tyre is likely to be a good bit different.

However, if you can into the speedo, easy to print out some different overlays to stick on top of the normal numbers.

[P.]

Hmm, I see.

Well this is going to be a pain. I just don't fancy doing 40 in a 30 on a bike that you would expect a local scum bag to be on, especially as one may not be owned by said rider. Minimal issues = happy Paddy.

[SQL]

GPS for real speed, then use speedo for MOT's

[P.]

It isn't just the MOT people I need to please, its 5-0 and their witch hunt for enduro bikes

[G]

If you're doing the right speed, the police aren't going to know your speedo is out.
When I got stopped many years ago one of the reasons mentioned a little under the real speed I believed I was doing was that I didn't want them to use the "doesn't your speedo work"... to look at said speedo and see it didn't actually have a needle .

[P.]

I suppose, I just want to minimise the risk, as I said, they aren't all going to check out exactly in my name.

[SQL]

[Fizzer Thou]

Waffles has a digital speedo setup on the XR250 that is switchable between the 21" dirtbike wheel and the 17" SM wheel.It is neat,tidy and has other useful functions as well.
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[P.]

Think that bike has a power source though? I'm running sans battery, would that still work?

[Fizzer Thou]

The digital speedo on Waffles XR250 is fed from an AC source and lights up as soon as the engine starts.There is a small battery inside from what I remember.But the instructions also allow for feeding from a DC source which the speedo automatically senses either AC or DC feed.

As for the speedo sensor,we used the originally supplied magnet for the 21" dirtbike wheel and a KTM style sensor for the 17" SM wheel after finding a suitable magnet to fit to the front disc.
____________________
Just talk bikes.What else is there?

Always have a 'Plan B'

[G]

A push bike speedo, as above, will be more accurate that might just have a setting for 21 & 17 wheels as you can measure it more precisely.

The really cheap one I had started to go iffy around 50 (would start to show half the speed), but the decent one I had on the ZX9 (after the above incident) was good well in to three figures.

[P.]

It is likely to never exceed 60.. so a cheapy shouldn't be too bad.