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Discussion Starter #1
Ok.. So I know a lot of people go down a tooth on the front, but I was wondering if anyone has ever reached a happy medium by going up 2 teeth in the rear? I really dont know how to calculate this stuff. So heres what I come up with.

stock is 15/39. Divide 39 by 15 and you get 2.6
Common mod is 14/39. 39/14 gives you 2.78 =More giddyup Less Top

So then I come up with bigger rear

15/40. Not very much gain at 2.66
15/41 2.73


The 14 tooth mod is 6.47% shorter

The 40 tooth mod is 2.26% shorter

The 41 tooth mod is 4.76% shorter

So is it safe to say that going to 41 tooth rear is a nice happy medium? Drawbacks that I can see would be the rear sprocket costs more and the chain probably wont fit with a larger rear sprocket.

Anyone have any thoughts on this? Is my math or reasoning off???

I'd like to have some more pick up but I dont want to top out at... 135ish???
 

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I went to the DP Alloy 42 tooth rear. Stock 15 front and my chain fit fine. You do have to move the wheel almost all the way forward but it works. I never figured the exact ratio but it feels good while riding.
 

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well, I went to the 14 tooth front right away, then a couple months later I went to a 40 tooth on the rear because the new Carrozzeria rims came with a new rear sprocket and I could specifiy the number of teeth. 14/40 is a 2.857 ratio. Just about perfect in my view. Bike is pushing its redline about 220kph, but riding these is not about 200kph+. Wheelies real nice.... :)
 

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if you go too extreme on the ratio then you'll find yourself working the gearlever a lot more. I find it great with the 14/40 (or any other combo giving you about 2.8 ratio). I think if you go much more than that, it will require working the gear lever overtime....
 

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Discussion Starter #5
DADDA. Seems like your gearing is suiting you pretty good. I've never taken the bike to full speed yet. I've just got around 525 miles on it since picking it up a couple weeks ago (reallllllly babying this thing). Actually just buttering it up for an all out S&M session at about 600.01.

If youre still pulling 135 in that gear, I think the 42 tooth rear option might squeak me out a bit more. State's usually dont chase a bike and damned if I dont have this "flee" twitch when I see their little heads turn and noses dip. The bike looks like it can do 150+ so maybe thats enough. Then again, I'm the only one with a red S for a couple hundred miles from what I can tell. Maybe I can just blame it on you. "Yeah officer.. I'm pretty sure it was this Australian dude."
 

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Hero

How does your bike feel after the Termi goodies you had put on.............The only thing I don't like about my GT so for is the head seem to loose. Going to take the shield back off and see if that helps. Already installed the stock bars. Halls already had my Demo with over 600 when I bought it. So no wait on break in for me. Like I would have drove easy anyway. I also think a couple of teeth extra on the back plus the 14 already on my front would be perfect.........For playing.
 

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Although in my opinion 14t on the front is about perfect from a gearing standpoint, it is the safe minimum size from a wear point of view with a chain of the very modest quality fitted as OEM to the Sportclassics. A better solution is to retain 15t on the gearbox, and fit a 42t at the back. (It also looks better in gold!)
 

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I'm not so sure I would want to go 14/42, if for no other reason that it may change my gear shifting pattern in traffic. Changing the gearing in this direction (as we all do) causes the motor to rev up quicker for a given speed - you can go a bit too far resulting in more frequent upshifting. OK, OK, maybe that's NOT a problem. On the other hand....
I am happy with my gearing selection and it seems that on my favorite roads the gear changing points are still spot on. Adding a few more teeth to the back might just force an extra gear change just a bit too often.
As for the top speed of 220kph, it gets to 200 pretty quickly but the last 20 seem to take a long time. Above 180 it starts to leave the comfort zone a bit - still stable but feeling VERY FAST for a public road. I hit 260 on my old R1 and that actually felt slower than the SC at 200. Go figure! I think the SC is the better deal - would rather feel faster at a slower speed. Though, hittinig a kangaroo at 260 or 200 makes little difference - you're still dead.
For you non Aussies - bikes DO hit kangaroos and it does hurt.
The other benefit to the gearing change, for those who have not done it yet, is that the annoying guage vibration at low rev acceleration goes away - the motor picks through the revs quickly enough to eliminate that irritating little feature of the stock bike. :)
 

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I have been running 14/39 for a long time now, the stock 15/39 set up was way too tall for the hills and this is a nice set up for around here - much quicker off the line but at the sacrifice of top end which is not a real big deal as i don't see too many straight long roads ;). I have had it to 190kmh with this set up without any issues and it will go faster. This is roughly the equivalent of running a 15/41 but it was easier to change the front sprocket out, as an aside I needed to use a rattle gun to get the nut loose :eek:.

Incidentally a lot of guys swear by 14/41 (2.93).
 

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Sprocket Changes and Wheelbase

One thing to consider when changing sprockets is the effect on handling.

Changing a motorcycle’s basic geometry by increasing the length of the wheelbase increases stability at the sacrifice of quicker steering. The longer the wheelbase the greater the effect.

There are two linked forms of motorcycle instability: Wobble, which occurs at low speed and causes the front wheel to rapidly flip back and forth like that of an unruly shopping trolley; and weave, the fish-tailing effect that happens at high speed.

At street speeds, the standard wheelbase lengths give better handling, but at higher track speeds instability issues often limit maximum overall performance. At triple-digit speeds, more stability - at some sacrifice in handling - can give you faster lap times.

The longer the wheelbase, the better the bike’s ability to combat high-speed weave but (by definition) the more difficult it becomes to turn the bike into corners.

It doesn’t take much of a wheelbase change to have an effect. To give you an example, in recent years, the factory riders have chosen more stability over faster turning to achieve faster lap times. The first generation Corsa magnesium swingarms were 15mm longer than stock, the last generation were 30mm longer than stock. What swingarm length to use boils down to what’s best for each rider given their riding technique and preference.

There are other handling consequences too. These changes also put higher cornering loads on the front wheel that has a tendency to induce the front to slide sooner. Better traction out of corners is a another characteristic of longer swingarms.

So what’s this got to do with sprockets? Simple.

When you change a sprocket’s tooth number you also change the diameter of the sprocket wheel, and so for a given number of chain links you change the position of the rear wheel.

Reducing the front sprocket from 15-tooth to 14-tooth increases the wheelbase 4mm. Every tooth that you add to the rear sprocket decreases the wheelbase by 4mm.

So assuming you’re starting with a stock 15/39 wheelbase

Ratio >> Gearing >>> Wheelbase Change

2.60 >> 15/39 >>> 0mm
2.67 >> 15/40 >>> -4mm
2.73 >> 15/41 >>> -8mm
2.80 >> 15/42 >>> -12mm
2.87 >> 15/43 >>> -16mm

2.79 >> 14/39 >>> +4mm
2.86 >> 14/40 >>> 0mm
2.93 >> 14/41 >>> -4mm
3.00 >> 14/42 >>> -8mm
3.07 >> 14/43 >>> -12mm

Note however that if you change the chain by adding two more (16mm pin-to-pin) links, and checking first that the range of the chain adjuster permits this, we get instead:

Gearing >>> Wheelbase Change

15/39 >>> +16mm
15/40 >>> +12mm
15/41 >>> +8mm
15/42 >>> +4mm
15/43 >>> 0mm

14/39 >>> +20mm
14/40 >>> +16mm
14/41 >>> +12mm
14/42 >>> +8mm
14/43 >>> +4mm
 

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How does your bike feel after the Termi goodies you had put on.............The only thing I don't like about my GT so for is the head seem to loose. Going to take the shield back off and see if that helps. Already installed the stock bars.
Ducati imposes a speed limit of 80.8 mph with the windshield installed. This, on a bike that's already prone to head shake! I think I'd lose the windshield, and/or install a steering damper.
 

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Popped the shield off yesturday. Day before had installed the stock bars.

Went for a little ride before work only about 5 miles for some fuel. And to hit the clover leaf. On the way to work I got to thinking man no front end wobble at all on that short ride. Also with the shield off and stock bars on the wind did a good job of keeping my hands loose on the bars. Looks like the stock throttle cables and brake lines will go on next. The gray duc looks alot better with the stock bars on for sure.
 
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