Thinking of Going to a 22T Gearbox Sprocket

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Fast Eddie said:
I like your figure better, when I last dyno’d it, it was 65rwhp… so that means it’s around 81 at the crank.

Sweet !
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Not all dynos have the same loss factor either. A 350 HP 5.7 Gen III Hemi would pull about 180 RWHP on a Dynojet dyno but only around 245 HP on a Mustang dyno. They used different methods of resistance.
 
I use gearing equivalent to a 22 tooth sprocket on my 850. I ride mainly two up, and we have use it a lot for long trips. It works great set up that way. I also ride to work and ride in traffic. You will not find first gear to tall. Around town often you are in third. I suppose that might cause gearbox wear, but I have not had any problems in about 25000 miles. I guess if for some reason you never wanted to go more than 60 MPH the lower gearing would be OK. I prefer to be able to use lower revs on the highway. I think if I didn't ride two up all the time I might even put a 23 tooth sprocket on.
 
tricatcent said:
I use gearing equivalent to a 22 tooth sprocket on my 850. I ride mainly two up, and we have use it a lot for long trips. It works great set up that way. I also ride to work and ride in traffic. You will not find first gear to tall. Around town often you are in third. I suppose that might cause gearbox wear, but I have not had any problems in about 25000 miles. I guess if for some reason you never wanted to go more than 60 MPH the lower gearing would be OK. I prefer to be able to use lower revs on the highway. I think if I didn't ride two up all the time I might even put a 23 tooth sprocket on.
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I like to cruise about 75 MPH. It won't get you a ticket normally and it eats the miles up.
 
No cruising here above 70mph and that only on twin highway … I tried a 22T only briefly as made the combat feel a bit sluggish , next was 21T which was perfect for my type of riding , always lots left at right wrist when I gad the urge …maybe just kinda try a few different T counts and decide what best for you , have fun experimenting !
 
Craig said:
No cruising here above 70mph and that only on twin highway … I tried a 22T only briefly as made the combat feel a bit sluggish , next was 21T which was perfect for my type of riding , always lots left at right wrist when I gad the urge …maybe just kinda try a few different T counts and decide what best for you , have fun experimenting !
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What size rubber do you have on back? It seems curious that nobody has addressed tire size in effective gearing. A 22t with my 18" rubber is very close to a 21t with a 19" tire on the back.

Only .4 MPH difference at 4000 RPM

Thinking of Going to a 22T Gearbox Sprocket


Thinking of Going to a 22T Gearbox Sprocket
 
Craig said:
No cruising here above 70mph and that only on twin highway … I tried a 22T only briefly as made the combat feel a bit sluggish , next was 21T which was perfect for my type of riding , always lots left at right wrist when I gad the urge …maybe just kinda try a few different T counts and decide what best for you , have fun experimenting !
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And you bare riding a 750 Combat, not an 850 MK II.
 
It's a bit like asking what's your favourite ice cream. It's all good but everyone has their particular favourite ice cream. People find a favourite ratio that suits their particular riding style and the terrain they inhabit. For me it is 20 tooth.
Re the rear tire size- most people that switch to an 18" rear run a 4.00 x 18 Avon Roadrider or similar. The 4.00x 18 Roadrider is 671 mm in dia., Identical to the 100/90/19 Roadrider , so there's no change in overall ratio from that.
One downside to high gearing on a Commando is the higher the gearing the more time spent riding in the vibe zone. Just the opposite of all the other British parallel twins.



Glen
 
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Just for a different perspective:

I put a 120/90-18 on the back of my bike - same OD as the original 4.10-19 - restored the steering geometry back to original, which I really enjoy.

We have 20T sprockets on both the 750 Combat (my bike) and the Mk2 850 (Dad’s bike). Seem like a good compromise on both bikes. We typically keep the speeds under 85 mph, usually 60-70 mph. We don’t typically ride in traffic, and it gives a nice spread of speeds in each gear to keep the revs over 3000 rpm while in lower speed limit areas - think small towns / villages.

FWIW - ultimately, it’s your bike - gear it how you want.
 
I think it a personal preference... 22t saves hassle when changing chains...but the downside is the torque loading from low engine revs.. The hooligan me liked seeing 70odd mph in 2nd and the noise on full shout as well as the ability to cruise in the 90s but on todays crowded and over policed roads it all seems a bit passe . If it were not such a hassle to take the primary drive off, would probably go back to 19 t
 
oldmikew said:
I think it a personal preference... 22t saves hassle when changing chains...but the downside is the torque loading from low engine revs.. The hooligan me liked seeing 70odd mph in 2nd and the noise on full shout as well as the ability to cruise in the 90s but on todays crowded and over policed roads it all seems a bit passe . If it were not such a hassle to take the primary drive off, would probably go back to 19 t
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On the uncrowded highways where I live I will seldom be riding under 60 MPH.
 
Dan1950 said:
Here's my reasoning:

First of all I live in a rural area about halfway across the Northern tier on New York State. Riding in traffic will be brief, perhaps less than 10% of my riding. I live on the Northern edge of the Adirondack Park.

Second, I want a good highway bike that will also be fun in the twisties. A dual purpose machine so to speak.

Third, I have found that lower gearing can have a "placebo affect'. All the noise and fury gives the elusion of greatly increased acceleration when sometimes, that is not really the case. In fact, too low (numerically high) gearing can actually have a negative effect on acceleration once out of the hole. It all depends on the torque curve.

Last, I have a 110/90 X 18 rear tire that is almost 2% smaller than the stock 19" rubber, so increasing the sprocket tooth count by 5% wont have a significant affect on acceleration but will reduce RPM somewhat..

Here are some screen shots of the various combination. Let's concentrate on the 3500 - 4500 RPM range.

1: Stock 21t with 19" rubber
Thinking of Going to a 22T Gearbox Sprocket


3500 RPM in 4th = about 64 MPH, not bad.


2: Current gearing 21t with 18" rubber
Thinking of Going to a 22T Gearbox Sprocket


3500 RPM in 4th now equals just over 61 MPH. heading in the wrong direction IMO


3: Custom gearing 22t with 18: rubber
Thinking of Going to a 22T Gearbox Sprocket


Now we are doing just over 64 MPH at 3500 RPM, just a bit more than stock. For every 500 RPM the speed in 4th increase by just over 9 MPH so 75 MPH will be at just a little over 4000 RPM and 80 MPH will be attained with less than 4500 RPM. 3rd gear ought to be a hoot for overtaking.

So given the fact that I have 18" rear rubber, my riding style and the environment I will be riding in I think adding a tooth to the gearbox sprocket to be worthwhile, especially since I already have the gearbox exposed.
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If it were me I would set it up for the best fuel economy especially living in rural area.
 
Dan1950 said:
Yes I know. It is so colorful and funny.

Reminds me of the days when I hunted deer and small game almost exclusively with tradition muzzle loading rifles and shotguns. I called breech loaders "suppository guns" as you loaded them by sticking something in their backside.
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I'd be careful if I were you, The OP might get upset that you're draining his thread!;)
 
BERT said:
If it were me I would set it up for the best fuel economy especially living in rural area.
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I think the 22t will be a good compromise. 3000 RPM at 55 MPH, 75 MPH cruise at just over 4000. And I think acceleration will be better than smaller sprockets under many conditions. A 22t in 3rd will out accelerate a 20t in 4th.
 
1973 850, 20T OEM wheels/tires. When I bought the bike it had a 23T sprocket. Couldn't deal with the lack of "go." 20T works fine for me - bike frequently runs at 90MPH for extended periods on Mexican highways as well as more typically moderate speeds on twisty, secondary (or tertiary!) roads.

As noted, the choice is all about what works best for your riding style.
 
Dan1950 said:
On the uncrowded highways where I live I will seldom be riding under 60 MPH.
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maylar said:
That pretty much says it all then.
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60 MPH on my rubber with a 22t sprocket should have me at about 3300 RPM. I can overtake in 4th but I like kicking down into "passing gear" for a more spirited experience. Should put me just over 4000 RPM when I drop to 3rd. :D
 
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