Wheel sizes

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

Random, i know. But i'm bored and trying to work out the actual spped of a cbr125. Yes, before people say it. Its slow.

Anyway, without a wheel to hand, im stuck. Is a 17inch wheel actually 17" in dia, or is that the rim?

I need to know the circumferance of a 17" wheel!?

Stuart.
____________________
"because one stroke isnt enough and four strokes waste two"

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

It is a 17" rim, then the tyre on top of that.

So a 17" wheel with a (for example) 100/80 tyre has a circumference of (((17 * 25.4) + ((100 * 0.8) * 2)) * 3.141592653)mm.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

1.861m?

(I'm doing a biology degree to get away from maths and english!)
____________________
"because one stroke isnt enough and four strokes waste two"

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Well I made it 1.859m.

Not sure what size rear tyre the CBR125 has.

If you look on the 125 sports bike forum there is a guy on there who has got one and now wants to derestrict it. Seems nobody told him before he bought it that they are not restricted.

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

carvell · Scuttler Joined: 05 Sep 2003 Karma :

1.8592m to 4 D.P. is the correct answer.

Your rounding was a bit iffy!
____________________
Yamaha TDM 850

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

72.6MPH in 5th at peak, 80.5MPH in 6th at peak. if my maths is correct...
____________________
"because one stroke isnt enough and four strokes waste two"

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

What are the tyre sizes, primary drive ratio, final drive ratio, gearbox ratios and max revs / revs at peak power?

All the best

Keith
____________________
Traxpics, track day and racing photographs - Bimota Forum - Bike performance / thrust graphs for choosing gearing

carvell · Scuttler Joined: 05 Sep 2003 Karma :

cagiva gezzer · World Chat Champion Joined: 17 Mar 2003 Karma :

https://www.cub90.co.uk/Resources/cbr125r04e.pdf

I got all the info from there. I think my maths is correct, havent got any tunning books to hand so i cant check it, but it looks right.

Carvell - Its a calculation based on engine speed,primary reduction , gearbox reduction, drive reduction and wheel size. They are the speeds the bike will reach if it revs to peak power.

No doubt i've messed it up though!
____________________
"because one stroke isnt enough and four strokes waste two"