I just did the 14T front sprocket swap last weekend, and (finally) the bike is docile in traffic, and doesn't bog at 45 mph.
I will be doing a 520 chain conversion at some point, and have heard positive things about a 15T front (better mechanical leverage, I am told).
IF that is the case, and I am looking for a gearing combo close to my 14F / 41R, then what would be a 15T equivalent? I assume a 15T / 43T ?
14/41 = .341
15/43 = .348
Would anyone even feel the difference of .007 gearing change?
I am asking since I honestly don't know.
Thoughts? Or is it just better to stick with the 14 / 41 combo?
It will feel about the same as the 15/43.
It's a good idea and likely the chain will last longer.
If you want to get REALLY close, 15/44 would be .001 off...
Quote from: trouble on September 08, 2008, 09:08:49 PM
It will feel about the same as the 15/43.
It's a good idea and likely the chain will last longer.
Why would the chain last longer? The only thing I can assume is that the front sprocket radius is larger, if that affects any chain wear.
There was a mechanical engineer who posted something about the 15T having a better mechanical advantage over a 14T (larger radius from the countershaft).
Can anyone verify if that is correct, or is it just a hunch?
Quote from: hillbillypolack on September 09, 2008, 05:37:29 PM
Why would the chain last longer? The only thing I can assume is that the front sprocket radius is larger, if that affects any chain wear.
There was a mechanical engineer who posted something about the 15T having a better mechanical advantage over a 14T (larger radius from the countershaft).
Can anyone verify if that is correct, or is it just a hunch?
There is no mechanical advantage, in fact, the opposite is true. But, it
is indirectly related to sprocket diameter.
Chain drives do not transmit a constant force. Each time a chain link engages a sprocket tooth, there is a force impulse in the chain. This is due to tooth profile, centrifugal force, etc. These pulses wear a chain out faster. In industrial applications you will rarely see sprockets with less than 20 teeth because that is the "rule of thumb" diameter ratio that more or less eliminates the pulsing effect. Fewer than 20 and the effect increases pretty dramatically. If I remember correctly, having only 12 teeth decreases chain life by over 50%. (I could look up the equation, if you like.)
So that's the semi-detailed explanation ... and yes, I'm a mechanical engineer.
To make matters even more muddy you also are effecting the squat/antisquat aspect of the chassis. Playing with different angles as the chain is pulled on by the sprocket (smaller sprocket is pulling from a different angle due to size).
We are splitting hairs here though, ducati has fit 14 tooth sprockets on some of their bikes right of the assembly line (748,916sps) so it is not out of the norm.
If I am putting on a new chain and sprockets I always go for the 15 tooth front. If there are outside reasons where this is not possible it is not that big a deal.
if it's a single sided swingarm bike and the rear sprocket is $300 or more, good motivation to do the front. if it's a dual sided swingarm and they $100 or less then go up on rear. a bigger front and rear will also move the chain off the swingarm guard, which might help.
For the record, gear ratios are calculated by dividing the driven gear tooth number by that of the drive gear.
So instead of...
14/41 = .341
15/43 = .348
...it would be...
41/14 = 2.93:1
43/15 = 2.87:1
Quote from: ducvet on September 09, 2008, 07:08:54 PM
To make matters even more muddy you also are effecting the squat/antisquat aspect of the chassis. Playing with different angles as the chain is pulled on by the sprocket (smaller sprocket is pulling from a different angle due to size).
This is VERY important if you're setting up your bike for max performance in the twisties. If anyone is interested, I can post a diagram & explanation.
Quote from: Norm on September 20, 2008, 06:53:31 AM
Quote from: ducvet on September 09, 2008, 07:08:54 PM
To make matters even more muddy you also are effecting the squat/antisquat aspect of the chassis. Playing with different angles as the chain is pulled on by the sprocket (smaller sprocket is pulling from a different angle due to size).
This is VERY important if you're setting up your bike for max performance in the twisties. If anyone is interested, I can post a diagram & explanation.
Please do.
How do I post a pic here?
[xximg]picturelink[/imgxx]
without the xx
also located beneath the ITALICs button.
I still can't get it.
(//)
Until I can figure out the picture thing, here's a description:
This is commonly referred to as "pole of the moments". Draw a line along the upper chain line, another line from the rear axle thru the swingarm pivot. Now, draw a line from the tire contact patch to where all 3 lines intersect. The steeper this angle is, the more anti squat characteristics the bike will have. As you can see (figuratively) the sprocket sizes plays a significant role.
Norm, theres a FAQ that deals with the picture thing. Basically, you need to upload your picture to a place like Flickr or photobucket. Then right click on the picture, select copy image location, and paste it between the img tags.
Quote from: JBubble on September 23, 2008, 07:10:21 AM
Norm, theres a FAQ that deals with the picture thing. Basically, you need to upload your picture to a place like Flickr or photobucket. Then right click on the picture, select copy image location, and paste it between the img tags.
Quiet you - all this talk for Flickr techno voodoo bable ;D . Sheeees Bubble there you go being practical again.
Quote from: yuu on September 23, 2008, 07:23:18 AM
Quiet you - all this talk for Flickr techno voodoo bable ;D . Sheeees Bubble there you go being practical again.
i know, i know. i should just keep my mouth shut. [laugh]
Quote from: JBubble on September 23, 2008, 07:10:21 AM
Norm, theres a FAQ that deals with the picture thing. Basically, you need to upload your picture to a place like Flickr or photobucket. Then right click on the picture, select copy image location, and paste it between the img tags.
http://ducatimonsterforum.org/index.php?topic=109.0
tada!!!
http://i239.photobucket.com/albums/ff154/motomaxy/swingarm-poleofthemoments.jpg
Quote from: Norm on September 24, 2008, 07:45:09 AM
tada!!!
here ya go
(http://i239.photobucket.com/albums/ff154/motomaxy/swingarm-poleofthemoments.jpg)
Quote from: JBubble on September 24, 2008, 08:20:56 AM
here ya go
(http://i239.photobucket.com/albums/ff154/motomaxy/swingarm-poleofthemoments.jpg)
Cool diagram, but what does it mean? Should I NOT put a 14t sprocket on my bike?
Quote from: NorDog on September 24, 2008, 11:01:50 AM
Cool diagram, but what does it mean? Should I NOT put a 14t sprocket on my bike?
hell if i know man. i was just helpin the guy post a pic. ;D
FWIW, i put a 14T on my bike and love it.
Thanks for the help Bubble, I'm not the most computer literate guy around. We're in process of buying a CNC machine so get ready for a LOT more questions!!!
The 14T sprocket gives a different upper chain line & reduces some of your anti-squat (not very much tho). The biggest problem is that it puts the chain so close to the swingarm that you don't have much room to steepen your swingarm angle. Go the the text I posted above & draw some imaginary lines. There is no fixed number that is "the best" - different riders, different bikes, etc. BUT, if you don't try different set ups, you'll never know if your bike is properly set up for you.
Now, if you want to get really confusing, start a thread on chatter. ???
Except the swingarm pivot is not in front of the countershaft sprocket, it's behind it...
I'm not sure if I follow your question nakid, can you elaborate for me?
Quote from: JBubble on September 24, 2008, 08:20:56 AM
here ya go
(http://i239.photobucket.com/albums/ff154/motomaxy/swingarm-poleofthemoments.jpg)
what is the point ahead of the countershaft sprocket in your picture?
I'm running 15/43 and the bike is more managable in parking lots & such. It takes a few MPH off the top speed, but I didn't buy a carbed, air-cooled, no aerodynamic plastic covered bike for top speed. It works well IMO ~
JM
Quote from: the_Journeyman on September 27, 2008, 09:28:16 AM
I'm running 15/43 and the bike is more managable in parking lots & such. It takes a few MPH off the top speed, but I didn't buy a carbed, air-cooled, no aerodynamic plastic covered bike for top speed. It works well IMO ~
JM
Yeah, my S4RS has ALWAYS run out of road long before it ran out of power.
Quote from: NAKID on September 27, 2008, 09:13:31 AM
what is the point ahead of the countershaft sprocket in your picture?
I think the graphic illustrates the following:
The dot forward of the countershaft sprocket is an imaginary point where the lines of the top of the chain, and from the center of the axle and tangent to the tire meet.
When the swingarm is at the lowest point (squat?) the line of the chain comes closest to the
sprocket swingarm pivot. By going down a tooth (15t to 14t) the chain line (actually, the chain itself) comes closer to the swing arm pivot point. If it comes too close, the chain can dig into the swingarm.
That's the only thing I can figure out from the diagram (assuming it is dimensionally accurate).
But, has anyone had this problem from installing a 14t sprocket?
Quote from: JBubble on September 24, 2008, 11:17:27 AM
FWIW, i put a 14T on my bike and love it.
+1 [thumbsup]
This is a horse we've beat to death already. For all I've heard about 14t front sprockets causing premature chain wear and rubbing on swing arms, I've never seen it. I had the opportunity to go back to a 15 tooth when I replaced the chain on my bike about 12,000 or so mi. ago and stayed with a 14t (put it on at 600mi) - 27,000 on the bike now. I happen to like the 3.07 ratio of the 14/43 combo and you would have to have a 15/46 to equal that, and you can't get bigger than a 44t for a single side swing arm bike easily. Fitment of bigger than a 44t rear gets iffy much bigger than that too.
I don't think you mentioned what bike you have. If you have a older bike with the 2.0 primary drive ratio I'd be tempted to use a 15/44. If it's a SSSA bike a quick change unit. Like Brad Black mentioned, an OEM rear sprocket on a single sided swing arm bike cost more than a quick change sprocket carrier with a rear sprocket included.
Call Chris at Ca-CycleWorks, or any of our sponsors and see what they offer. I've used a couple of 520 DID sets from Chris.
LA
The point where the lines meet is called the "pole of the moments" and it is the top 2 lines that dictate the angle of the lower line. The closeness of the chain to the swingarm only matters if you want to change this angle. The point is not to get a particular gear ratio or to increase chain clearance or chain life, it is to adjust the squat/anti-squat characteristics of the bike during acceleration. This affects how the bike holds a line when accelerating out of a corner.
Quote from: Norm on September 28, 2008, 07:39:20 AM
The point where the lines meet is called the "pole of the moments" ...
That's what she said. [cheeky]
Quote from: LA on September 28, 2008, 06:06:51 AM
This is a horse we've beat to death already. For all I've heard about 14t front sprockets causing premature chain wear and rubbing on swing arms, I've never seen it.
+1.
The chains on our Ducatis do not know the difference between 14t and 15t. And this is only because
other factors dramatically outweigh the contribution of sprocket size to wear. Whenever industrial chain applications are mentioned in the same conversation with mention of motorcycles, one needs to put more aspects of the design into context... Many industrial chains are expected to go 10,000+ hours of use on a minimum and hundreds of thousands of hours of use would be normal. 12,000 miles at an average of 40 mph is only 300 hours of use. Designers of systems involving chains probably have more than a few parameters to consider beyond tooth size. 300 hours? That's every other month if the chain only works an 8 hour day (5 days a week)! I'd think someone would be fired, shot, or both if they designed an industrial machine that needed a chain replaced every 300 hours.
The only times I have heard of wear on the chain guides is when the rear ride height is increased by non-trivial amounts. And on 2002 and newer models. The older hoop-type rear suspended Monsters don't seem to care as much.
More to the OP's question, I doubt anyone would notice .007 difference in gearing. In my experience, people will wonder if something changed with 1 tooth difference on the rear sprocket. 2 teeth and that's a change. 3 teeth starts wandering into the land of shifting for 7th gear on the freeway. Also, 3 teeth on the rear sprocket is loosely equivalent to 1T in the front and can be simulated on most Ducatis as the difference between 5th and 6th gears. I normally advise customers worrying about the effect a 14T sprocket will have on the freeway to spend time in 5th and 6th and get used to it. Then after the install, they get happier city riding and are prepared for the small change on the freeway.
:) Chris
So what exactly happens to the bike when you go down the the 14T? How does it specifically affect the performance and what will I notice?
Quote from: StandTall on October 23, 2008, 09:48:44 AM
So what exactly happens to the bike when you go down the the 14T? How does it specifically affect the performance and what will I notice?
Less bogging/lugging at low RPMs (in my experience, better driveability at very low speeds/in stop and go traffic) and a little loss at the top end.
The biggest hit I have noticed is fuel mileage when commuting. Start and stop, never out of 2nd/3rd gear etc. I get 30-35mpg if I commute for an entire tank. If I'm out riding, even spirited/hard, even 2-up I get 40-50mpg. It's a lot more manageable in town though ~
JM
Quote from: JBubble on October 23, 2008, 09:55:25 AM
Less bogging/lugging at low RPMs (in my experience, better driveability at very low speeds/in stop and go traffic) and a little loss at the top end.
I thought about changing over to the 14t next service since I read it was better, but didn't know exactly why. Thanks for the info.
Quote from: StandTall on October 23, 2008, 02:45:44 PM
I thought about changing over to the 14t next service since I read it was better, but didn't know exactly why. Thanks for the info.
Sure thing. It was the first mod on my bike. Easy to do but don't do what my ex did to mine and put it on backwards. It will make the beast with two backs everything up and cost you a couple of sprockets and a chain.