ZX12 sprockets

[JPaddo]

Thinking 17/46 or 17/47.

17/47 is stock wheel base... wheelie prone?
17/46 lengthens wheelbase by what? So little that's it not noticeable in the twisties? I spose it'd keep the front planted but I'm not keen on making it harder to tip in than it already is.

No need for a chain right? I've only got a 6000km chain anyway (original chain from new, actually) Was just thinking of picking up a couple of vortex. Yeah I know aluminium and all but I can get em local easily, unless anyone knows where I can get renthal in non stock sizes.

Any feedback on highway RPM - say @ a buck 20(ish) compared to stock? As people know the 12 has a buzz in the bars at highway on stock gearing, 17/46 is enough to get past it?

Oh, also, I'm a complete and total track noob but I'm going to EC a little these days. What gearing do you run for that?

Effect on top speed? Do you run it with rev extension feature from ignition mod? (12 actually has an artificially lowered redline - thanks to all the angry European govt boffins) Anyone running a g-pack?

Lots of Q's I know, sorry bit of a brain dump just to get some thoughts.
Cheers.

[MAXUMIS]

what rear tyre are you running at the moment?

[JPaddo]

190/50 but I'll be going 190/55 shortly provided it fits inside the hugger.

[MAXUMIS]

i have a 190/55 rear and went up 2 on the rear sproket(48) but the tyre compensated for most of it and that was swaping from a 200 rear witch is taller than a 190/50 rear.they say 3 on the back is -1 on the front so if you go -1 on the front with a 190/55 rear as compared to a 190/50 there wont be a big differance.i have heard that you have to raise the hugger to compensate for a 55 BUT i have not seen for my self.

[JPaddo]

Still 18 on the front then maxumis? How do you find it compared to stock? Must shorten the wheelbase a lot too? Or running non-standard chain?

[MAXUMIS]

still standed front but upping the rear sproket i went a new chain.it was a catch 22 sitch have the wheel right ford and tight chain(from memory i dont think it would have fitted) or new chain and have a longer wheel base .if you go -1 on the front you will save on a chain

[MAXUMIS]

you best work out what tyre you are going to use before hand as tyre size can change gearing a fair bit.

[JPaddo]

190/55 (i'll chuck some washers or something on the hugger if I have to). So the tyre will make the 17 front (or larger rear, or both) less pronounced.

[JPaddo]

Well in the end I went with 17 front, 47 rear. Just give me a few combos to experiment with. I'm actually interested in 18/47 as it should shorten the wheelbase nicely.

Yeah I know it's 3am (in the land of daylight savings, unlike this forum)

[Smitty]

..........

Yeah I know it's 3am (in the land of daylight savings, unlike this forum)

the forum is whatever YOU make it
...check yr User Control Panel
you just might join the rest of us

[JPaddo]

omg winner. I'm a software engineer too, I code forums like this for breakfast.

[MAXUMIS]

this calculator will help http://www.google.com.au/url?sa=t&rct=j ... SUSonDt63A

[Gosling1]

..... I'm actually interested in 18/47 as it should shorten the wheelbase nicely......

mate - 1 tooth up on the front sprocket is going to make SFA difference to the overall wheelbase - you care talking a change of around 5-8mm, on a wheelbase that is 1450mm long. In % terms, that is a difference of about 0.0055% - which is about exactly the difference you are going to feel in the wheelbase when you change sprockets.

Even going up to 50 teeth on the rear will make SFA difference to the wheelbase ( but it will give you good wheelies )

BTW - if you go from 17:47 to 17:46, you won't lengthen the wheelbase, you will shorten it. This change will only move the buzz from 120 to about 125.

The gearing change above, is reducing the overall final drive ratio from 2.76 to 2.70. You will notice a *very* slight difference in acceleration - maybe. The top-end change will be unnoticed, unless you regularly hit redline in 6th.

There is a much more noticeable difference though, when you drop from OEM gearing of 18:46 (2.55) to 17:46 (2.70). This change actually does make the acceleration more snappy off the mark. If you stay with 18 tooth front, to get almost the same gearing you would need to change to a 49 tooth rear (2.72).

That gearing calculator from Maximus is worth a read. But remember - changing the sprockets only affects the gearing, it has SFA to do with the wheelbase, and you won't be able to feel a change in the wheelbase at all from a change of sprockets. Even allowing for normal chain stretch on the OEM chain - the wheelbase can vary by up to 20-25mm. This still only represents a change of 0.017%. It is bugger-all in real terms.

[JPaddo]

Exactly what I needed to hear Gos thanks mate you're a champ.

So 17/18 vs 46/47 = SFA in wheelbase, no effect on cornering. And probably, no difference in wheelie monsterage between 17/46 and 17/47

[Gosling1]

no worries brother - with the 12 you get way more effect on the steering by changing to a 190 rear instead of a 200, but you have already done that mod.

No change in wheelie monsterage at all from a 46 to 47 tooth. If you went 16/50......well now that would get you off the mark quick smart and wheelies at your beck & call !