[shep532]

OK .............. I don't really get this gearing lark.

If I remember correctly standard Adventure gearing is 17/42

I currently run 16/45 and find the gearing just about right.

I tried 16/47 and it was great - but with a standard length chain I had wheel clearance issues at the front of the back wheel and it rubbed on the shock guard and on compression caught the wheel arch where the exhaust bulge is. (Basically I needed a 120 length chain). But by fook the bike was lively.

I found with the lowered front sprocket - it wasn't just like a lower gear, it seemed to actually change the torque characteristics of the bike. I suppose that was because I now ran different revs for a given speed and had some 'in-between' gears compared with standard.

Martynho has recently said he has stayed at 17 on the front but gone larger on the rear. I think 17/45. he reckons this stops chain slap and is kinder to the front sprocket and offers a similar gear ration to 16/42

So - I like my 16/45. if I changed to 17/47 how would this compare? I reckon it'd be a similar ratio ......... but how would you expect it to 'feel'?

I have this theory in my head somewhere ........ that depending on whether you change the front or the rear sprocket - although you may end up with the same actual gear ratio - the way it affects the bike will be different. Or am I just bullshitting myself?

All I'm thinking is that I have the 17/47 sprockets so I can easily give it a go. Will it be beneficial to take some strain off the front sprocket?

Thought, comments and ideas please?

Pete

 

[Duncan]

Shep,
Hope this helps, based on the sprockets you have.

Fr Rr Ratio
17 42 2.47 Speed
16 42 2.63 ↑
17 45 2.65 |
17 47 2.76 |
16 45 2.81 ↓
16 47 2.94 Accel.

Sorted in order of Ratio.

R

 

[Martynho]

Heyup Pete,

You should have been paying more attention during maffs at school

There will be no difference in "feel"as you put it for the same ratio achieved by different means. but 17/47 is going in the wrong direction for you if you like your current 16/45 and the 16/47

17T front is definitely better for wear, the other factor affecting wear is the combo of f/r sprocket size with chain length. As this affects the number of times any given tooth meets the same link on the chain. Less is better.

Here have a play with this..... Gearing Commander: Motorcycle Gear Ratio Calculator for Sprockets RPM Speed Chain

The 990 is loaded into the database.

 

[riderbob]

16/45 works for me.

 

[mooky]

For offroad, I want to give a 16:47 a go too - Dirt Tricks are making a steel 47T rear.
Id like to try a 16:51 too

 

[Martynho]

Going trials riding?

 

[mooky]

Going trials riding?

Motocross

 

[Martynho]

You must be:

A big b*stard
A forkin good rider
Mental
Rich

Good luck and be sure to post pics. I like this idea, but as I fulfill none of the above then I am happy to watch someone else get hurt.

 

[mtb_man]

Just had the first ride on my new 17-45 gearing. It's heaps better at low speed and the engine still has enough to cruise pretty comfortably on the highway.

17-47 would be mental for wheelies

 

[DAKAR990]

Just a quick reply to say that you need only to divide the number of teeth on the rear sprocket by the number of teeth on the front sprocket !
This will tell you the ratio you are running,
The ratio !!

 

[Happyhenry]

Just had the first ride on my new 17-45 gearing. It's heaps better at low speed and the engine still has enough to cruise pretty comfortably on the highway.

17-47 would be mental for wheelies

Is going from a standard 17-42 to 17-45 OK with the standard chain length? Looking at the Gearing Commander it has to be much better for chain and sprocket wear as well as chain clearance than going for 16-42, whilst giving the same gearing.

 

[Martynho]

Yes you can run an std 118 chain on 17-45 (I have just fitted this), but you have to switch the adjusters around. You have to run 118 to get the full benefit as a 120 chain will see a different (worse) combo of same tooth/link frequency.

 

[Vic]

I run 16/42 on my Adv990. I wouldn't consider myself to be an experienced rider and dont quite understand how changing sprockets works chain/gearbox wear wise, but thought that changing the front sprocket could help me cope with the twitchy throttle whilst riding offroad. now I can go a gear up a little bit earlier. still think I'm gonna have to get a throttle cam to cure the problem completely. got to say tho, the power delivery especially at the bottom revs, has really improved. not that there was any improvement needed, but the bike feels a loot faster.
BTW interesting thread. I'm learning something here.thanks
Vic

 

[Happyhenry]

Yes you can run an std 118 chain on 17-45 (I have just fitted this), but you have to switch the adjusters around. You have to run 118 to get the full benefit as a 120 chain will see a different (worse) combo of same tooth/link frequency.

Thanks. That's got to be the better option. 17-45 sprockets are now top of the list for me.

 

[shep532]

I run 16/42 but the bike feels a loot faster.

On my 16/45 the bike is actually slower on the road .............. but far nicer off the tarmac.

 

[Martynho]

Shep's slow anyway

 

[shep532]

Shep's slow anyway

Oi! I said the bike was slow not me

Anyway - last time we were out me and Gav were on nobblies and you were on some girly road tyres .......... otherwise we wouldda thrashed you

 

[SonnyRider]

I have a 16\47 with 120 link on my 950SE
It used to have a 16 \ 45 with 118 links, with the blocks turned around

I find the pick a little better, is slightly more flighty in 1st & 2nd. Who am I kidding? I find it a bit more manic than before
I've also fitted a scott oiler to help improve chain life because it's not an optimum front\rear\link ratio.

Lets face it, if I were bothered about those wearing fast, I would be worried about fuel consumption too = I wouldn't have bought a big mad KTM:666:

I find 3rd is more fun off road, where'as before it could drop the revs down too low, relying on the bottom end stomp to get going. Now it just pulls cleanly

 

[DAKAR990]

I have been running standard gearing for over 4 years and 2 years before that on my 950 s !
Countless rallies and over 40000 miles, I have found it to be ok !

Maybe I should try going down to a 16 on the front, then I don't need to shorten the chain do i ?