Just to follow on from the other thread where I was saying that a 1200 Sport gearbox had fallen into my shopping cart from whence it is going to fall into my GRiSO I thought it might interest people to learn what the ratios in the various boxes are. I haven't done the sums on the Stelvio yet but I'm pretty certain it uses the same ratios as the GRiSO. I'll confirm later.
OK, so there are basically two sets of primary gears. These are the only helically cut gears in the box. The first one is on the clutch shaft. The second one on the primary shaft of the box. (I'll insert pics later if people wish.)
The way you calculate a gear ratio is taking the number of teeth on the driven gear and dividing it by the number of teeth on the driver. Now the GRiSO uses a 26 tooth clutch shaft gear and a 35 tooth primary. This gives you a ratio of 1.35 to 1.
Both Sport and Norge use a 24 tooth clutch and a 35 tooth primary giving a ratio of 1.46 to 1
(Edit.) Actually looking at those figures is weird as it seems to indicate the GRiSO has the higher primaries, which is weird because the Sports are definitely taller geared. I think I'll have to just take the boxes apart and looksee.
Now after that all the boxes use the same ratios for the first four gears. They are.
1st- 17/38 giving a ratio of 2.235 to one.
2nd- 20/34. 1.7 to one.
3rd- 23/31. 1.35 to one
4th- 26/29. 1.115 to one.
So the primaries in the Sport and Norge box make the overall gearing higher than the GRiSO but other than that everything is the same.
From there things change a bit. In 5th and 6th both the Sport and the GRiSO retain the same ratios with tooth counts of.
5th- 31/30 1.03 to one. Essentially a direct drive.
6th- 29/25. 0.86 to one. A substantial overdrive.
Looking at the Norge though fifth is already an overdrive!
5th- 31/29. 0.935 to one.
And sixth is higher again!
6th- 30/24. 0.8 to one!ALL
the CARC bevelboxes use the same ratio so from the point of this investigation can be ignored.
So, what we can see from this is that the GRiSO is the lowest geared of the lot. This means that it will have, at least in theory, the fastest acceleration and lowest top speed. This is irrelevant in the real world of everyday riding though as you're rarely, if ever, going to be hitting the rev limiter in 6th. I have done it once, maybe twice, the Speedo was saying 247kph! Given wheel slip etc. a more realistic figure might be 220 but I can tell you when it goes 'Blurp-Blurp' at that velocity it is a bowel emptying experience as GRiSO will get very squirrelly if it hits bumps at that speed!
Next cab off the rank is the Sport. I've long liked the slightly taller gearing of the sport. It doesn't seem to make the bike appreciably slower in the lower gears due to the 8V's prodigious Torque but it turns sixth into a true overdrive and if you're wanting to get off the line quickly I actually find that I don't seem to run out of revs and find myself grabbing another gear in a frantic hurry like I can do on a GRiSO. Top speed will probably be little different as the power produced and the parasitic factors, (Wind resistance, the fact the rider is a great fat bastard etc.) won't change. It might even be a bit slower! Who cares? If you're caught doing 200kph here you are going to gaol and your bike is being confiscated and anyway, riding GRiSO over 150 kph for any length of time is tiring! That's why I'm swapping to a Sport box on mine.
Finally we come to the Norge. This has the benefit of the taller primaries but also has those two taller top gears. It just so happens there was one of those boxes sitting around for cheap in Holland as well as my Sport box. Well this morning it fell into my cart as well and it's going to get flung behind the engine in a certain black and Orange 1400cc GRiSO that sometimes lurks around these parts.....
For all the noise and bollocks spouted about 'Getting more power' out of the 8V there are plenty of other interesting, enjoyable and really pretty inexpensive ways of customising and improving your ride!
If you want 130hp? Buy a TV4! Betcha we'll only be half a beer behind you at the pub at the end of the ride and we'll be a lot more relaxed as welll