The stock gearing is 15/38 giving a top gear ratio of 3.995 to 1. Most people settle for changing the front sprocket to a 14t or changing the rear sprocket to a 41t, reducing the overall gearing to about 4.3 to 1
What is the stock gearing on a 2002 ST4s? Thanks in advance!
If your asking this because your trying to determining or play with different front and rear sprocket sizes, send me your email address, and I can give you a really cool spreadsheet I wrote for comparing RPM versus SPEED, based on your sprocket choices. I wrote it for an ST4s, but it can be easily modified for any gearing.
If your asking this because your trying to determining or play with different front and rear sprocket sizes, send me your email address, and I can give you a really cool spreadsheet I wrote for comparing RPM versus SPEED, based on your sprocket choices. I wrote it for an ST4s, but it can be easily modified for any gearing.
Switched to a 14T front on my '03 ST4S. Just did 3700 mile mountain vacation and it was a huge improvement over stock.
Plus - while getting the 15T off is a pain the 14T size will forever be much simpler to get on/off. I have to think this was the size the bike was designed to go up to and as other posts have mentioned Duc used the 15T for the EPA's drive by top gear noise tests.
__________________
2008 1098
2003 ST4S-ABS
Corbin seat w/br
+3" Zero Gravity
Ducati Designs headlight
New in 2005 are the following:
- Staintune stainless exhaust
- Spidi Ergo Jacket & pants
This is an interesting thread... sounds like something I would be interested in. So, try not to roll your eyes too far back in your heads as I ask this: ( relative "newbie" to mods/upgrades that I am! )
What is the improvement when switching to a 14t front sprocket? A little LOWER gearing, putting a little more power rather than speed while at ones normal rpm levels? Or,...? Thanks!!
This is an interesting thread... sounds like something I would be interested in. So, try not to roll your eyes too far back in your heads as I ask this: ( relative "newbie" to mods/upgrades that I am! )
What is the improvement when switching to a 14t front sprocket? A little LOWER gearing, putting a little more power rather than speed while at ones normal rpm levels? Or,...? Thanks!!
Increased torque, or bottom end is the net result. But as you have already figured out, the trade-off is top end speed.
The stock front is a 15T, and the stock rear is a 38T (I think it was anyway, it been a while). Anyway I've played around with various rear sprockets (40, 41 & 42), and ended up using the 42T for everyday driving and short trips (300 miles or less). Naturally, I installed a new chain and increased the lenght by 2 links over stock.
With the new chain length and a 41T rear sprocket, the axle will align almost at center on the swingarm when the chain is properly tensioned. I'm currently running my 42T regularly so I can get accustomed to it for tracking. I had been waiting for the temp's to drop about 15 or 20 deg. and so I could be more comfortable. But I think the 41T is a better choice for the highway, perfect actually.
Many people will opt for changing the front sprocket down to a 14T so that the purchase of a new chain cab be avoided. My opinion on that (and I'm probably gonna get countered on this) is unfavorable, because of the reduced moment arm (front sprocket radius reduction). It's not a concern about chain tension, but rather "Load" on the engine. It's JMHO, I don't have any data to substatiate my concerns. But I have read that on some bikes, changing the front sprocket down a size, can result in the chain prematurely wearing the sacrificial plastic slide or chain guide that's on top of the swing arm. But I don't have any experience with that personally. Just something I read.
Everything Gilbert says is absolutely correct. The deflection angle of the chain is worsened going to a 14T from the stock 15T. There is also a lot to be said for the benefits of gearing targeted to your specific uses. But there is a simple, wide range of gain to be gotten from just changing your countershaft to a 14T.
However, I reiterate my observation on the fit of the 14T versus the 15T and belief - maybe unfounded so call it intuition with a trace of other posts I've seen - that Ducati engineers really designed this engine to use a 14T countershaft sprocket. No engineer would make changing the stock countershaft that much more difficult to r & r than one only a single tooth smaller.
The simplest way to describe the benefit of the 14T could be in saying that it makes a slight increase in engine RPM in any gear at any speed. The advantage then becomes very apparent in top gear where the stock gearing makes 6th gear useless for accelerating at any speed less than 85-90 mph.
With a 14T you have much better engine response at that slightly higher RPM (see the dozens of torque and HP curves posted on this board on different topics). Given a set of stock variables such as cam profiles and timing, exhaust restrictiveness, airflow, compression ratio, displacement, etc., your bike's desmoquattro engine makes more HP and torque as rpm increases within the range shown in those torque and HP curves.
Both measurements of power to the rear wheel will improve. In top gear these benefits also come to you along an even more rapid building of rpm. Simply put, more bang with less wait which is what engine response is all about. (Don't confuse this with throttle response which is technically a function of fuel/air mix interacting with your ignition programming.)
The lower RPM of the 15T produces slightly less noise measured on a sound meter in a top gear drive by at a set speed to meet federal reg's. So, less restrictive exhaust for better performance can be OEM equipment with the only drawback being you need to change the sprocket - a relatively cheap mod for capturing significant performance benefits that include that less restrictive stock exhaust.
Last but not least by not having to wait several seconds while the engine builds rpm in top gear roll-ons - burning more fuel than should be necessary to go from say 65 up to 75 - you will actually see a real world fuel economy improvement. My guess would be as high as 3-7 mpg depending on how lazy you are about tweaking the throttle versus downshifting.
You won't regret spending the $30 on the 14T. I gotta believe that is the way your bike was meant to be.
__________________
2008 1098
2003 ST4S-ABS
Corbin seat w/br
+3" Zero Gravity
Ducati Designs headlight
New in 2005 are the following:
- Staintune stainless exhaust
- Spidi Ergo Jacket & pants
Thanks guys! Exactly the info I was looking for! I am interested in trying a 14t front sprocket... the benefits sound excellent. Where would I get one? Suggestions? Also, and bear with me here,... ( newbie to mods! ) ... will I need to do anything to my chain, or will it remain AS IS?
Easy to install this myself, or would it be a dealer installed item?
I would say your local Duc dealer shouldn't jab you much more than $40 and it would be a relatively low dollar investment to get to know the dealer parts guys better. Can come in handy. Pay a few bucks more than mail order on a low priced item to get to know them.
You can do it without breaking the chain for sure as I was able to just a couple weeks back.
First unbolt the cover and remove the sprocket bolts. Then - because it's a 15T it's gets a bit difficult. Maybe there are some guys out there that know an easier way to get a 15T off but it is kind of a pain in the ass.
I think I did loosen the slave unit without any issues (just don't pull the clutch lever in while it's off). Then I loosened the back axle and tried to get enough slack in the chain to pull it forward enough to wiggle the sprocket off the countershaft. No go - but I did this by myself and maybe someone else helping may be ablle to get enough forward pressure on the back wheel to provide enough slack OR maybe your chain is stretched more than mine and enough to do it.
Otherwise I had to remove the back wheel (definitely don't push the back brake lever down now) to get enough slack to pull the 15T out. Putting the 14T on is really a breeze and this is the point where you will see what I was talking about when I said this bike MUST have been designed for a 14T.
Wrestle the chain back on the rear sprocket and then lining the spacer up with the axle and wheel while getting the rotor up in to the caliper is definitely a two person affair and pretty dirty BUT it will never be this hard again as long as you throw that 15T away quick. Better yet - melt it down!
Sounds kind of nasty but it really takes less than 30 minutes and is a lot easier than taking off the fairings and putting them back on.
What are you doing for a headlight? The stockers should be illegal - seriously - they will get you killed out in the boonies where the critters roam.
__________________
2008 1098
2003 ST4S-ABS
Corbin seat w/br
+3" Zero Gravity
Ducati Designs headlight
New in 2005 are the following:
- Staintune stainless exhaust
- Spidi Ergo Jacket & pants
Funny you should say that about my local parts guy... I HAVE gotten very friendly with him and the service manager as well. They have already taken good care of me on a few issues! ( including some freebies! ) Sound advice!
Thanks for the concise installation instructions regarding the change-over to a 14t... I do believe this is the next mod to my bike. Currently,
I have added: Termignoni Carbon Fiber exhaust with ECU "tweak" and Dyno Tune done by BCM. Fabulous! The bike just rips!
Sargent WS seat, custom done to look like a Solo Seat as I had the rear portion wrapped to match the bike's color, yet retaining the "Bi-Posto" seating arrangement.
Assorted Carbon Fiber pieces.
Regarding the OEM Headlight: I couldn't agree more! It is a tad pathetic in it's performance. I did in fact check out the Ducati Designs system... WOW! Now that's more like it! It is a tad pricey, but well worth the cash IMHO.
I have a few things I want to do/add on this bike! Thanks again for the insructions/advice!
ST4s stock gearing
Or,...? Thanks!!
Linear Mode
