Thinking of Going to a 22T Gearbox Sprocket

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4.10 x 19 rear wheel size ….. it is your choice , no best answer to this one , except what works best for you ….
 
Dan1950 said:
60 MPH on my rubber with a 22t sprocket should have me at about 3300 RPM.
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The theme throughout this thread is that your gearing should suit your riding style. Here in suburbia I spend most of the time at 35-55 mph and a 20T works perfectly. 2500 rpm at 40mph is a sweet spot in my iso's and I get superb throttle response to 70 and beyond when needed. If you'll be at 60+ most of the time than something steeper is appropriate.
 
Craig said:
4.10 x 19 rear wheel size ….. it is your choice , no best answer to this one , except what works best for you ….
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Not really interested in going 19" rear wheel.
 
22T was the standard size for the non-US/Canadian 850 Mk3 and seems about right for mine with 19" rear wheel/4.10 tyre as I live in a flat area of the UK and don't normally carry a passenger.
Thinking of Going to a 22T Gearbox Sprocket
 
You had asked after my wheel size , in both my posts I referenced what ever you decided was your choice …. just posted what worked for me, as other posters had previously
 
My vibration eases off at just under 2500rpm and upwards, so cruising at 2500rpm very smooth. Reading previous comments on threads here, I think there's a trade off with isolastic adjustmets. The bigger the gap on the front and rear engine mounts, the more the isolastics seem to perform to reduce vibes, but the handling is less precise. I've no practical experience on this. But, I'm happy with it currently and hoping mine doesn't need adjustment too frequently. It looks like a pig of a job, especially the rear, even with my Mk3 vernier adjusters!
 
Me 3 on the 2500 rpm thing - mine is really choppy between 2500-3000 ish - so much so, I downshift to stay out of that zone when riding through slower areas:

4th gear: 50mph+
3rd gear: 40 mph+
2nd gear: 30 mph+

@Dan1950 - I know that you say that do not plan to ride below 60 mph, but Upper NY is much like Ontario - you might be surprised at how much time you spend under 50 mph... just saying.... having a smooth, useable 4th gear down to 50 mph is a nice feature, and keeps me from up-gearing. I know that my bike would pull more gear, but I would lose on the other end...

As far as the fuel economy thing goes - really?!? It is a Norton, not a diesel VW!! LOL!! Besides, the best fuel saver that I have found so far is making sure your carburetors are in good nick. I went from 40 mpg to 60 mpg just by installing a new set of needle jets...

Edit: And yes, I run my iso's as tight as I dare: tighten til it vibrates, then back off one hole. Everything is a compromise, I guess....
 
maylar said:
It was a side effect of installing a cNw head steady. My mirrors go dead still at 40 mph/2500 rpm now.
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Is that in 4th? On my 23T I'm in 3rd at 40 at just around those sort of revs.

So, a question: if I'm in 3rd at 2500rpm/40mph and accelerate hard, won't the engine perform the same as a 19T in 4th? Same be said if we both drop it down a gear? So am I only losing performance off the line in 1st and that disadvantage disappears as soon as the 19T changes up to 2nd? I

Also, in 2nd gear, I'm doing over 75mph at 6,000revs. So I don't need to lose time changing gears! :p
 
Mart UK said:
Is that in 4th? On my 23T I'm in 3rd at 40 at just around those sort of revs.
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Yes, in 4th with a 20 tooth and a 19" wheel. It's pretty much 16 mph per 1000 RPM. For the type of riding that I do I wouldn't want anything else.
 
Derek Wilson said:
@Dan1950 - I know that you say that do not plan to ride below 60 mph, but Upper NY is much like Ontario - you might be surprised at how much time you spend under 50 mph... just saying.... having a smooth, useable 4th gear down to 50 mph is a nice feature, and keeps me from up-gearing. I know that my bike would pull more gear, but I would lose on the other end...

....
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After driving over 500,000 mile in several Peterbilts with 13-speed Road Ranger transmissions, down-shifting for overtaking and varying road conditions is not only 2nd nature to me, I enjoy the added RW torque.
 
Dan1950 said:
After driving over 500,000 mile in several Peterbilts with 13-speed Road Ranger transmissions, down-shifting for overtaking and varying road conditions is not only 2nd nature to me, I enjoy the added RW torque.
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Yes - 13 speed is one of my favorites too.

And I am not trying to tell you what sprocket to put on your transmission, but you posted on here looking for information, and unfortunately, people are providing you with information. Sorry, I don't have 500,000 miles of experience with a 20T, only about 60,000 miles - maybe I am not qualified to have an opinion.

You have already made up your mind that you are going with a 22 tooth. So go for it....

I am not even going to mention the advantages of converting to an o-ring chain....

FWIW
 
I've lived in the same geographical area all my life. I've not really "toured" with the Commando, though I have ridden it for hundreds of miles through New England and upstate NY in the past and covered every conceivable road condition. And I've never wished for a different front sprocket than what it came with. Nowadays, I really enjoy the way the MKII pulls from 35 to 80 without a balk and without downshifting. IMO the 20 tooth sprocket matches the torque curve of the 850 perfectly. So... to each his own. Ride on.
 
Mart UK said:
Is that in 4th? On my 23T I'm in 3rd at 40 at just around those sort of revs.

So, a question: if I'm in 3rd at 2500rpm/40mph and accelerate hard, won't the engine perform the same as a 19T in 4th? Same be said if we both drop it down a gear? So am I only losing performance off the line in 1st and that disadvantage disappears as soon as the 19T changes up to 2nd? I

Also, in 2nd gear, I'm doing over 75mph at 6,000revs. So I don't need to lose time changing gears! :p
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If you raise the gearing by 15% from stock you will have 15% less rear wheel torque in each gear and a 15% higher speed at any given rpm.
A friend geared his Thruxton R up about 12% and was convinced that it accelerated quicker with the change . He asked me to try it. I did and it felt slightly lacking. It's hard to tell for sure via the butt dyno, although some will claim their device is a perfect instrument.
So we went thru the gears starting off side by side in 1st.
I'm about twenty pounds heavier than he is, nonetheless, his bike just kept falling back, farther and farther in each gear. By sixth, at highly illegal speeds, he was behind by about a dozen bike lengths.

Glen
 
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worntorn said:
If you raise the gearing by 15% from stock you will have 15% less rear wheel torque in each gear and a 15% higher speed at any given rpm.
A friend geared his Thruxton R up about 12% and was convinced that it accelerated quicker with the change . He asked me to try it. I did and it felt slightly lacking. It's hard to tell for sure via the butt dyno, although some will claim their device is a perfect instrument.
So we went thru the gears starting off side by side in 1st.
I'm about twenty pounds heavier than he is, nonetheless, his bike just kept falling back, farther and farther in each gear. By sixth, at highly illegal speeds, he was behind by about a dozen bike lengths.

Glen
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Yes, OK, but if we rev the bikes in the same range, I will be in a lower gear, after you have topped out and changed up. Will that not make a difference?
 
Whichever bike has the mechanical advantage at any instant will outperform the other.
In practice, if the other guy has the same bike and a bit lower gearing, he will have the best acceleration all around but may be limited for top end, dependant on the ability to pull to the redline in top.

With the two Thruxtons, the gearing difference was also really noticeable when exiting a corner. We both needed the same gear nine times out of ten, but my standard geared bike had quite a bit more oomph than his 12% overgeared bike. I guess it had 12% more go, so that was very noticeable. Before the gearing change he stuck like glue on the corner exit acceleration.

With the 20 tooth on the Commando 6500 rpm = 105 mph. 6500 with 23 teeth = 121mph, except the bike may not have enough power to pull 6500 with the 23 tooth, especially if up in elevation.
Sometimes the lower geared bikes will actually have a higher top speed.
But you do get more " relaxed" cruising with the higher gearing, and burn a bit less fuel. Then there's the vibration zone as discussed.
If you are happy with the way the higher gearing works, there is nothing wrong with doing it that way, however there is a reason Norton fitted 19 tooth and 20 tooth sprockets to North American bikes.
Thirst for acceleration!
Glen
 
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I don't know. I'm no idiot, but somehow understanding the torque, power, gearing thing has always eluded me. And my father lectured mechanical engineering at Birmingham Uni, drives him nuts. I can't get past why a 23T bike revving at 5,000 revs isn't producing as much torque as a 20T bike at 5,000revs. When I'm in 2nd at 50, or 3rd at 70 and you're in 2nd at 40 or 3rd at 60 at some point you change gear out of the max torque spot, while I'm just getting into it. And vice versa. Why doesn't it just cancel each other out?
 
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