18 inch frt wheel

[Peter Mac]

After meaning to do this for a few years now I finally got round to fitting an 18inch frt wheel to the H1d , used an s2a frt guard on the stock h1 fender mount but with the holes slotted , needs to drop another 10/15mm really tho so back in the workshop after i've had a test ride

[Kawaclive]

Hi
If that does not work you can use an H2R brace and fibreglass fender blade.
It's designed for the 18" wheel.
As a matter of interest without someone baffling us with Mathis and rolling radius's of tyres any idea how much the 18" wheel has changed the speedo reading?
Did you use the H1d speedo drive or one off a small triple?
If you want the H2R fender Nigel Everitt does them, I have his number.
Cheers

[Peter Mac]

Alright clive .. Used the h1 drive so will have to see how it reads until i find an s2/3 drive .. No maths involved in any of my spannering bud , build it then make it work school of thought for me

[Kawaclive]

HI again
You are from the same mould as me and the speedos were never that accurate anyway.
We may still tempt a maths boffin to work it out for us though.
Keep well.

[Peter Mac]

Right change of plan on the guard , after a rummage in my spares i dug out a z400 guard & bracket & after reversing the guard & shortening it i am please with the closer fit of it .. So a bit of drilling & fabrication later this week should see it on .. I'll post a pic once done

[Peter Mac]

Bit more time on it this evening & now the z400 guard is on & looks alot better the the s2a guard , Will finish it off tomorrow night & then get it painted

[Kezsam1]

Pete I've got a nice fibreglass guard may be of use

[Peter Mac]

Pete I've got a nice fibreglass guard may be of use

oh txt me a pic bud please

[Kezsam1]

Pete I've got a nice fibreglass guard may be of use

oh txt me a pic bud please

done on wattsapp this very am

[Pops]

Done quick calculation comparing the rolling circumference of the 19" and 18" tyres and the speedo will read about 4% faster with the smaller wheel assuming same tyre size and aspect ratio.

More or less

(Working away, in hotel, bored.....)

Pops

[stevie747]

HI again
You are from the same mould as me and the speedos were never that accurate anyway.
We may still tempt a maths boffin to work it out for us though.
Keep well.

It shouldn't be that hard, assuming the tyre 'height' is the same (if not measure them) then the circumference of a 19" (490mm) wheel is 2 x 3.14 (pi) x radius (490/2 = 245) = 1538mm. For an 18" (456mm) is 2 x 3.14 x 228 = 1431mm - with me so far :wink:

Therefore the 18" wheel has 93% (1431/1538x100) of the rolling circumference of a 19" wheel, so I guess the smaller wheel will read 7% higher speed..

[stevie747]

HI again
You are from the same mould as me and the speedos were never that accurate anyway.
We may still tempt a maths boffin to work it out for us though.
Keep well.

It shouldn't be that hard, assuming the tyre 'height' is the same (if not measure them) then the circumference of a 19" (490mm) rim is 2 x 3.14 (pi) x radius (490/2 = 245) = 1538mm. For an 18" (456mm) is 2 x 3.14 x 228 = 1431mm - with me so far :wink:

Therefore the 18" rim has 93% (1431/1538x100) of the rolling circumference of a 19" rim, so I guess the smaller wheel will read 7% higher speed, although the difference will be slightly greater when you add the tyre heights in

[MalcP]

Blimey, before this gets any more complicated let's keep it simple. It's as Pops says because it's all linear. Measure the diameter of the original wheel and tire (say 24") and then the new wheel and tire diameter (say 23"). Diameter has decreased by 1" on the original 24", that's 1divided by 24 = 0.0417, multiply by 100 for a % gives Pops 4.2% faster reading than before. This will work for any such change, just measure the total diameters and use the difference.

If the tire on the 19" rim now, has a different profile to the original Kawasaki tire profile the speedo may already be reading wrongly and you may end up exceeding speed limits, or worse, not doing so!

MalcP

[SAM]

With the front wheel in the air it cocks the whole thing up!

[scouse]

Why not fit a speedo drive off an 18" wheel
Or is that too simple?

After all the H1 and KH 250 use the same clock as do the early H1 and the A Series

Gary T

[MalcP]

Why not fit a speedo drive off an 18" wheel
Or is that too simple?

After all the H1 and KH 250 use the same clock as do the early H1 and the A Series

Gary T

Yes, it'd work without any sums; typical engineer! Don't you want to doing mental arithmetic when you're on your bike? Got this from the web. Basically it says you shouldn't give a sh1t about it.

"The UK law is based on the EU standard, with some minor changes. A speedo must never show less than the actual speed, and must never show more than 110% of actual speed + 6.25mph. So if your true speed is 40mph, your speedo could legally be reading up to 50.25mph but never less than 40mph. Or to put it another way, if your speedo is reading 50mph, you won’t be doing more than 50mph but it’s possible you might actually only be travelling at 40mph.

To ensure that they comply with the law and make sure that their speedometers are never showing less than true speed under any foreseeable circumstances, car manufacturers will normally deliberately calibrate their speedos to read ‘high’ by a certain amount."

MalcP

[Mitsui Spy]

Yeah but what if the wheel was out of round? Then at times the speedo could be correct and at other times it could be wrong . And what if the tyre deformed at high speed thus changing its diameter?! What then? OMG a variable read-out speedometer . And what if your speedo cable had a manufacturing fault which made its torsional stiffness too low and on acceleration it twisted, not only under-reading slightly but also absorbing energy, said energy being released when a steady speed is achieved resulting in a momentary over-read .

Jeez. I'm glad I've had my eyes opened to all these speedometer perils. To think I've been riding around in ignorant oblivion. That's it - my bike's not coming out again until I've had my speedometer calibrated by CERN.

[MalcP]

Yeah but what if the wheel was out of round? Then at times the speedo could be correct and at other times it could be wrong . And what if the tyre deformed at high speed thus changing its diameter?! What then? OMG a variable read-out speedometer . And what if your speedo cable had a manufacturing fault which made its torsional stiffness too low and on acceleration it twisted, not only under-reading slightly but also absorbing energy, said energy being released when a steady speed is achieved resulting in a momentary over-read .

Jeez. I'm glad I've had my eyes opened to all these speedometer perils. To think I've been riding around in ignorant oblivion. That's it - my bike's not coming out again until I've had my speedometer calibrated by CERN.

Even then you're stuffed as your tire will be doing twice the speedo reading at the top and zero at the bottom.

[stevie747]

I think it's all a bit arbitrary - who the hell has a steady accurate triple speedo anyway

[Mitsui Spy]

Even then you're stuffed as your tire will be doing twice the speedo reading at the top and zero at the bottom.

Don't be ridiculous, that would create a paradox. It would mean that the tyre was in a state of acceleration at constant speed. Next you'll be telling me it's accelerating towards the wheel spindle. Whoever heard of such nonsense?

[MalcP]

Even then you're stuffed as your tire will be doing twice the speedo reading at the top and zero at the bottom.

Don't be ridiculous, that would create a paradox. It would mean that the tyre was in a state of acceleration at constant speed. Next you'll be telling me it's accelerating towards the wheel spindle. Whoever heard of such nonsense?

Sodit I hadn't thought of that. What nonsense, a centripetal force, I apologize, I will cast it out of my mind as soon as I get to the next bend in the road while carefully watching my speedo.

[Mitsui Spy]