Yep -1 on front equals +3 on rear. Going smaller on front does tend to increase wear on sprocket and chain guides though.

Yeah. I was pondering that yesterday afternoon when returning to Guildford from Brackley (A43/M40/A34/M4/A33..etc.....nice ride!) It didn't make sense.

But.........a larger wheel/circumference essentially raises the gearing......therefore enabling lower revs per given speed and vice versa higher speed per given revs.

Amen to that!

Having refitted the OEM silencer my Ten feels like a new bike again........well, not quite so old and abused. It was clearly missing significant back pressure and the engine feels a bit smoother and tighter. Being a courier I also like the stealth mode of being able to chuff along at a fair rate of knots without sounding like it.

As for gearing:
15/45 = 0.3333
14/45 = 0.3111 *
15/47 = 0.319
15/48 = 0.3125 *

I bought Kev's encyclopedia. It's a fountain of knowledge. The most cost effective thing I can do bhp wise is fit a stage 2 DNA (the bike came with a stage 1 K&N). That should add around 3.5bhp ish. I have a 16 tooth front which will lower the revs at 80mph from around 5000 to 4700. With a 110 link chain it will shorten the wheelbase by 3.5mm which is perfectly acceptable. I'll test that setup and go from there (this is on my XTR).

The XT660 engine produces max torque around 5,500 rpm. Don't be afraid of revs - they can actually smooth out some vibes .
Much better to have a more willing engine with less throttle at higher revs than one bogged down at lower revs.
In terms of vibration, big singles suffer more from low rpm abuse than high rpm.

3.5hp gain is not even 10%. You'll get far better/useable gains by lowering the gearing especially for offroading.

Good luck with what you decide. It's a great choice of bike - hope it's the right one for you.

A XTX has the front axle more in line with the forks & a smaller
front wheel.. all adds up to less rake, less trail.. the geomitrey
would be somewhere between a dirt bike & road bike...

Yeah. I've been pondering this one too! :icon_scratch: I reckon, the effective gearing lowers as the tyre wears down (as you say), resulting in a lower "real" top speed from any given revs in top, but (here's the rub) you'll only notice it on a GPS not on the bike's speedo. The bike's speedo will become more and more optimistic as the rear wears, which will occur at an identical ratio to that by which the gearing is lowering. Therefore I think, the speedo will read the same in 5th at 5000rpm with a new or worn tyre, but the actual road speed will decrease with a worn tyre... :confused1:

Ugg.......now my head hurts! :dontknow:

108,000 miles of courier use :partyondude: your a hero !

Nah, not me. It's the bike that's the hero!
:love4:

And it's because I'm a courier (returning to OP's thread) and have to keep costs to a minimum I will always extol the virtues of appropriate gearing before expensive exhausts and engine mods.
Tried a different silencer but the bike needed more money spent on tuning/re-mapping.

Trying out a different courier company next week that appear to be much busier so mileage should be going up faster soon.
On track for 200,000 km's, but what about 200,000 miles?? Sweepsteak anyone?!