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Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
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rbike Offline
Running Like a Top

Florida
Posts: 274
Joined: Oct 2015
Post: #1
Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
Thanks to all that assist others! The forum is great. This is my first post. I was going to wait until after I did this mod, but I have a few technical questions that after revisiting my original calculations that don't add up correctly from some of the 2014 data I saw on line. Originally I posted this to 19/37 thread, but I felt it should be on its own.

My desire to do this mod was initiated by the vibration at 4000 rpm when cruising at 70mph in 5th gear. The engine has way more power and needs to go into a next gear, but none is there. Plus, I am amazed at frankly the poor mpg motorcycles are now getting. My 750 nighthawk and CB450 were well above 50 into 70s. Getting upper 40s mpg during break in when I never went above 50mph and then apx 40mpg or less now that I have done first service and do 70mph on the interstate.

If you look at the following image I am providing, it is laid out with the 2013 CB1100 gear ratios on the far left in black, then the corresponding ratios for the 2014 model in Brown, then 2 options in blue and purple for modifying the front and rear sprocket on the 2013.

I read from many that their 2014 model when they are in 6th gear at 70mph they are doing 3250, 3300, ...rpm. What ever the real number is it will not differ from bike to bike, but from my calculations, I do not see how that is possible. If you look at my image data, nothing lower than apx 3729 rpm (4000 x 0.964/1.034) would be possible - and that is not even including the 40 tooth rear sprocket that would raise it to 3825 rpm (3729 x 40/39). Am I missing something or is the 2014 data I am using flawed. How is apx 3300 possible?

This brings me to deciding on the rear sprocket size I should get manufactured. Increasing the front sprocket to 19 is all that is possible. That alone will yield a drop in rpm to 3789 (4000 x 18/19) in 5th gear.

The next question is whether to also decrease the rear sprocket to 37 or 35. If 37, the purple numbers are the final net ratios and would yield an rpm of 3595 (4000 x 37/39 x .9474) - 90%. If 35, it is the blue ratios and the rpm would be 3401 (4000 x 35/39 x .9474) - 85%. A 10% drop will increase mileage to the mid 40s at a minimum
and 15% should be upper 40s to lower 50s.

A 15% or 10% drop in final net ratio in first gear should have minimal affect on getting rolling without requiring any clutch slip. I have started in 2nd occasionally by accident without problem and that is a much larger 35% drop.

Again the main reason for looking into this was to reduce the rpm in 5th. It is way too high IMHO. This is one of the only errors in design and I do not know why they released the 2013 this way. With such a major difference, switch out, cost, upgrade to the 6gear 2014 Tx is not an option.

Feedback regarding this sprocket mod and actual confirmation of rpm on a 2014 in 6th doing 70rpm :huh:is appreciated.

FYI, I purchased a great pair of slip on grip covers $20 that have eliminated apx 75% of the vibration through the handlebars. You may purchase the grips at http://www.misano-moto-imports.com/produ...overs.html for $16.95 plus S&H.

Pictures explaining above numbers used and of Package and What it would look like when Installed

   
   
   

[i]Now:[/i] '13 CB1100-W/S, Eng Guards, Grips, Omni Cruise, Rear Rack, Plug 4 Bat Charge, RLETS, '16 PCX150
[i]In-Work:[/i] Sprockets, Redo Tank
[i]Still-To-Do:[/i] Life, ...
Prior: '60s Honda 50 or 90, '70s CB450, '80s Clueless, '90s-00s CB750 Nighthawk
11-09-2015 07:09 AM
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The ferret Offline
Forum Moderator

Ohio
Posts: 31,283
Joined: Apr 2013
Post: #2
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
Never was good at math. here are some pics of the speedo of my 14 deluxe at various speeds..no trick photography...no math lol

http://cb1100forum.com/forum/showthread....ed+vs+rpms

.
Defender of the Realm
2014 DLX (the pleasure horse)
2021 NC750X DCT (Angry Bird)
11-09-2015 07:21 AM
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rbike Offline
Running Like a Top

Florida
Posts: 274
Joined: Oct 2015
Post: #3
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
Ferret, you are one of those that as I discovered the forum in early 2015, I appreciate and learn from your posts, but only joined now because I had questions.

Thanks for your reply. I never doubted 3250 was the rpm from members posts, but from the Transmission gear ratio data that many have posted, I don't understand how it is possible. If the 2013 does 4000 rpm in 5th (Tx ratio is 1.034 - 30/29) with a front/rear 18/39 sprocket combination and the 2014 has a 0.964 ratio in 6th with a 18/40 sprocket combination, then the 2014 should theoretically only be able to do 3824 rpm in 6th - (0.964/1.034) * (40/39) * 4000. For the math to work out correct allowing an rpm of 3250rpm in 6th on a 2014, the sixth gear ratio must be 0.8191 not 0.964.

For the following equations it is, Engine RPM / Transmission ratio equals the front sprocket rpm. Then Multiply (*) by the sprocket ratios = rear wheel rpm.

On a 2013, 4000 / 1.034 = 3868 then * 18/39 = 1785 wheel rpm. In order to keep same 70mph speed (wheel rpm) on a 2014 in 6th, a Tx ratio of 0.8191 must be used: 3250 / 0.8191 = 3967 then * 18/40 = 1785 wheel rpm

If 0.8191 is the "real" ratio everything makes sense, but if it is actually 0.964 than something else is in the picture I am unaware of. This is my dilemma and reason for this thread/post.

In a nutshell, you confirmed my reasoning to do a 35 vs a 37 rear tooth sprocket. That will enable a 3400 rpm in 5th at 70mph. Talking with pekingduck, there should be no problem starting in 1st with only a 15% reduction in ratio. After that everything is in sync.

[i]Now:[/i] '13 CB1100-W/S, Eng Guards, Grips, Omni Cruise, Rear Rack, Plug 4 Bat Charge, RLETS, '16 PCX150
[i]In-Work:[/i] Sprockets, Redo Tank
[i]Still-To-Do:[/i] Life, ...
Prior: '60s Honda 50 or 90, '70s CB450, '80s Clueless, '90s-00s CB750 Nighthawk
(This post was last modified: 11-09-2015 09:00 AM by rbike.)
11-09-2015 08:38 AM
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Bheezy27403 Offline
High Mileage

Triad NC
Posts: 941
Joined: Sep 2015
Post: #4
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
My head hurts
11-09-2015 09:03 AM
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Nemo Offline
High Mileage

Jacksonville, FL
Posts: 924
Joined: Oct 2015
Post: #5
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
(11-09-2015 09:03 AM)Bheezy27403 Wrote:  My head hurts

DITTO
Confused

N

“It is easier for me to be forgiving of the stupid than of the evil."
EmptySea

#BLACKBIKESMATTER
11-09-2015 09:39 AM
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Randy B Offline
Road Warrior

Palm Bay FL
Posts: 2,537
Joined: Apr 2013
Post: #6
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
1. Honda does not recommend anything smaller than the stock 39T rear sprocket because of swingarm clearance issues with the chain.

2. 37T sprockets have been used successfully and I have seen no issues reported with the chain hitting the swingarm.

3. A 35T sprocket would most definitely cause the chain to hit the swingarm and would not be recommended for use.

My thoughts.
(This post was last modified: 11-09-2015 12:17 PM by Randy B.)
11-09-2015 10:45 AM
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ChipBeck Offline
High Mileage

Scottsdale, Arizona
Posts: 886
Joined: May 2013
Post: #7
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
Rbike,

My 2013 CB11 has a 19 tooth front and 37 tooth rear and it took my 70mph rpm from 4000 down to 3600 and made riding much more pleasurable. The speed limit here in AZ is 75mph. Starting out in 1st gear is no problem even when two up. If you go all the way down to a 35 tooth rear you will need to break and shorten your link-less chain and you'll need to see how much the chain drags on it's slider. Taking a link out of the chain is not necessary with the 19/37 combination. One other item to look for. The stock CB11 rear sprocket is steel and very durable. Almost all aftermarket sprockets are made of aluminum and wear out much faster. "7th Gear Designs" has made custom 37 tooth steel sprockets for several members here and they are a work of art with slotted lightning holes. They are the company to contact to make you a steel rear sprocket.

When you finish let us know how it works out. All the best bro.

Chip

The road to hell on earth is paved with the good intentions of liberals.
11-09-2015 10:51 AM
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The ferret Offline
Forum Moderator

Ohio
Posts: 31,283
Joined: Apr 2013
Post: #8
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
lol like I said I never was good at math, so beyond the pics, I can't help you in figuring ratios etc. bet a Japanese engineer could explain it though, but we don't have any on the forum right now!

.
Defender of the Realm
2014 DLX (the pleasure horse)
2021 NC750X DCT (Angry Bird)
11-09-2015 10:52 AM
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ChipBeck Offline
High Mileage

Scottsdale, Arizona
Posts: 886
Joined: May 2013
Post: #9
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
(11-09-2015 10:45 AM)Randy B Wrote:  1. Honda does not recommend anything smaller than the stock 39T rear sprocket because of swingarm clearance issues wit the chain.

2. 37T sprockets have been used successfully and I have seen no issues reported with the chain hitting the swingarm.

3. A 35T sprocket would most definitely cause the chain to hit the swingarm and would not be recommended for use.

My thoughts.

Gentlemen,

Although I have not tried it I agree with Randy's comments above IF the stock 18 tooth front sprocket is used. Going to a 19 tooth front sprocket provides more clearance from the chain slider on the swing arm and some or most of that extra clearance is given back with the 37 tooth rear. So the first change in gearing should be going to a 19 tooth front. Nobody I'm aware of has used a 35 tooth rear with a 19 tooth front so I don't know it will cause problems. If it does you can just go back to the 19/37 combo that you know will work. Cheers.

Chip

The road to hell on earth is paved with the good intentions of liberals.
11-09-2015 11:06 AM
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rbike Offline
Running Like a Top

Florida
Posts: 274
Joined: Oct 2015
Post: #10
RE: Deciding 37 vs 35 tooth rear sprocket on 2013, 19 on Front is correct
I just verified with my local Honda parts and service.
2014 Transmission Gears are as follows:
M is main, C is Countershaft
M1-12, M2-17, M3-23, M4-25, M5-27, M6-28
C1-37, C2-33, C3-34, C4-31, C5-29, C6-27
This agrees with the transmission numbers/ratios in the original posted. So it still does not explain why 3250 is possible. If I had to guess, I would say that more than 1 gear is involved at times between the crankshaft and the first sprocket. For the purpose of this discussion, it is a moot point, because all that is affected my upcoming mod is the final sprocket ratio. The 2013 is a 18/39 & the 2014 is a 18/40. So by changing the 2013 to a 19/35 ratio, I will be reducing engine rpms equally in every gear by 15%. This will enable a cruise rpm of 3400 in 5th at 70mph.

I hope this eases the head pain some may be feeling - after all this is a technical thread. Even I get headaches when I overwork my cerebrum. It still pains me as to exactly how 3250 is being made possible.

(11-09-2015 10:51 AM)ChipBeck Wrote:  Rbike,

My 2013 CB11 has a 19 tooth front and 37 tooth rear and it took my 70mph rpm from 4000 down to 3600 and made riding much more pleasurable. The speed limit here in AZ is 75mph. Starting out in 1st gear is no problem even when two up. If you go all the way down to a 35 tooth rear you will need to break and shorten your link-less chain and you'll need to see how much the chain drags on it's slider. Taking a link out of the chain is not necessary with the 19/37 combination. One other item to look for. The stock CB11 rear sprocket is steel and very durable. Almost all aftermarket sprockets are made of aluminum and wear out much faster. "7th Gear Designs" has made custom 37 tooth steel sprockets for several members here and they are a work of art with slotted lightning holes. They are the company to contact to make you a steel rear sprocket.

When you finish let us know how it works out. All the best bro.

Chip

Thanks Chip. I spoke to 7th Gear Designs about doing this in steel for me and I am just waiting for him to get situated in his new facility. I manufacture PTO pulleys in Aluminum for fan belts, but for this steel is the only way to go with a chain.

Your feedback is what I have been looking for. I am going to break the chain & remove links so that it is as close to original as possible regarding for & aft adjustment & alignment. I asked (not on this thread) and I was told 35 is the smallest without hitting anything. If anything gets hit, I will have no choice but to do a 37. Without doing the mod and finding out too late, is there a way to ensure nothing will hit?

[i]Now:[/i] '13 CB1100-W/S, Eng Guards, Grips, Omni Cruise, Rear Rack, Plug 4 Bat Charge, RLETS, '16 PCX150
[i]In-Work:[/i] Sprockets, Redo Tank
[i]Still-To-Do:[/i] Life, ...
Prior: '60s Honda 50 or 90, '70s CB450, '80s Clueless, '90s-00s CB750 Nighthawk
(This post was last modified: 11-09-2015 11:35 AM by rbike.)
11-09-2015 11:25 AM
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