Front sprocket mod - 15T or 17T. Tried both. My conclusion.

[reminor]

Most of us know that swapping stock 16T (16 tooth) front sprocket is a cheap and effective mod to change dynamics of GS500. You can go either down to 15T (sometimes 14T) or up to 17T sprocket. Each way has its rationale and pluses and minuses. You can easily find much information on this forum about both directions and see for yourself.

So here is .02 from someone who tried it both ways.

When I got my GS in 2006 I read many topics on moding here (thanks fellas!). I decided to go against the trend of lowering the tooth count and selected to go up a tooth, to 17T. I do 90% of my riding on a highway going 65-80mph non-stop, so that mod would allow me to maintain lower RPMs at any given speed and maybe save some gas. I did not do much of 2-up riding then.

I rode like that for almost 2 seasons. First season doing backroads with 40mph tops. Second season going highway. I was averaging 55miles on a galon and rearly was going over 80mph (eighty is plenty for me and bad enough on my 55mph-limited highway anyways).

Recently I decided to see what I am missing (if any) and swapped my 17T with a 15T sprocket.

Here's my observations. First of all, going up or down a tooth from stock may bring much less change than you expect. If I am not mistaken it is about 5% change in gear ratio. If you go from mod to mod, 17T to 15T the change is much more preceived, but still quite moderate. Don't get me wrong -- you feel it, but not to the extent you may expect.

I found that proper carb tuning and syncing affects dynamics of your GS500 so MUCH, MUCH MORE than sprockets. So guys get your carbs done before trying to fix sluggish moves of your bike with sprockets. I found that jetting and ignition advancer mod affect performance of your bike MUCH MORE than sprocket swap. Do your jetting before sprockets.


So this is my final conclusion on sprocket swap. Though I do not regret riding with 17T at all, if you consider this mod go to 15T. No questions in my mind now. My in-town and 2-up riding feels much better now with a 15T. My highway riding doesn't feel much different, up to 85mph I tried. My fuel economy may suffer with higher RPMs on the highway, we'll see.  Now with a 15T sprocket I cruise at 70mph at about 6200rpm, vs. ~5500 with a 17T. Not a huge change if you ask me. In town and stop-n-go the bike is more nimble to get off. Better for 2-up riding, no doubt (but I repeat myself here). As for higher highway RPMs I may just enjoy riding by going a bit slower, just 5-7mph slower will get me where I was with 17T. So in short going with 15T or 14T is overall better, IMHO.

Keep the rubber side down folks. Summer is finally upon us.
=)

[manofthefield]

I compromised and use a 16T sprocket

[SIKDMAX]

Nice write up!  Whats the best/ a good brand of sprocket to use, and anyone have any links to cheap places on the net for them?  I need a new chain also.  Thanks! 

[ohgood]

I'm just beginning to enjoy a 15t front. I'll agree with you about it barely being noticeable from a 16t stock size. The difference from a dead stop is noticeable, but no where near unsafe or wheelie prone. Directly after the friction zone (IE, clutch fully released) there is virtually no difference, other than the rpm's are a few hundred higher for the same cruising speeds.

Given that the gs has a wide range of usable power (I don't mean a huge amount of power ) from way down around 3,000 rpm all the way up to 9,500 or so. That's a pretty large amount of play area, although I'd bet most people only use 1/2 of it most of the time.

Some love the 14t playfullness, I'd like to keep the front end on the ground unless I'm REALLY feelin frisky.

Nice summary of your experience

[ohgood]

Nice write up!  Whats the best/ a good brand of sprocket to use, and anyone have any links to cheap places on the net for them?  I need a new chain also.  Thanks! 

www.denniskirk.com has cheap cogs, but you may want to phone the order in. there are subtle difference from 89-94 vs 94-200x iirc. it's just a shoulder on the cog, but it will help keep it quiet and from rattling on the output shaft.

They're good folks , and will pull it from stock, put hands on it, and let you know it's really on it's way

I got lucky on my chain, one of the members here posted it to me for $35 shipped !

[GI_JO_NATHAN]

I love my 14T. Front doesn't ever come up, unless I really want it to.

[Suzuki Stevo]

I just put a 15T on my '07, in 5th gear 35mph is roughly 3500rpm, 45mph is roughly 4500rpm and so on, 65mph is now roughly 5500rpm in 6th gear

[Villager]

Interesting. I was considering swapping from 15t to 17t for touring, but after reading this I might not bother. Unless anyone has directly compared mpg?

[SIKDMAX]

I put on a 15T on my bike yesterday and definitely can tell a difference.  Taking off from a stop is much nicer, and Im crusing about 6500 RPM at 65 mph indicated.  I like it... wish I could power wheelie though hhaha

[jeremy_nash]

I HAD a 12 tooth front and a 42 rear, and I could power wheelie in second.  went back 2 16 in front though, and get 51 mpg average

[reminor]

Just to update you guys on my MPGs since the swap.

My last couple of "need-to-switch-to-reserve" moments happened at ~141-143 miles on the ODO vs. my usual 150 miles with a 17T (on almost the same route/dayly routine/speeds). I usually fill up just under 3 galons, so it is roughly 3 mpg less than I had with 17T (e.g. 52 vs. 55 MPG).

This measuring is FAAAR from perfect (+- 30% easily) and may be affected by speed, wind direction, temperature, gas quality, number of stops, moon phase, etc, etc. So my conclusion would be that the MPG difference between 17T and 15T is "neglectable small, though probably exists". 

I still prefer doing 75-80mph on the highway, albeit with slightly higher rpms and somewhat buzzier mirrors. Again, the riding perceivable change is far from huge. But I do enjoy better pickup while in 6th gear when passing (but again I am sure tuned carbs play much bigger role in that).

Rule of thumb with a 16T sprocket - when increasing rpms every 1k gives you about 12-13mph increase in speed (riding in 6th gear), i.e. while my tach is at 6000rpm it is about 67 mph, 7000rpm is 79mph, etc.


All in all, I'd say to an average guy -- stay with stock 16T. Best balance between agility and low rpms at speed. I guess Suzuki engineers do earn their salary for a reason. 

PS Lately I stumbled across an interesting thought about side effects of going to 15T. Going 15T may help you sell your bike (when the time comes) because the pickup from the standstill is somewhat quicker and "mightier", so the bike appears more powerful.

[08GSSteve]

Front sprockets change on it's own only does half the job.  Need to change the rear 3 up or 3 down as well.  You can do this without having to change the chain.

[starshooter10]

I put on a 15T on my bike yesterday and definitely can tell a difference.  Taking off from a stop is much nicer, and Im crusing about 6500 RPM at 65 mph indicated.  I like it... wish I could power wheelie though hhaha

theres a shop in my area who hooks me up good..

120$ "including tax" for a new RK Xring chain 39 stcok rear and a 14 (or i could have got a 16) front

[Teek]

Personally I find my 14t makes for a much quicker, smoother roll on from a standing stop, but I have to shift up a lot sooner than stock in all gears of course, so there's more shifting overall in town. It used to be fine up to 45 in 1st if I wanted, now it has a hard time making 35, and I usually shift up to second at 20-25. I like it in the canyons better this way though. Once on the flat at higher speeds I'm usually just a gear higher than stock, and am seldom gong fast enough for long enough to even hit 6th. For me though I found I need to be more careful in feathering the clutch at low speed maneuvering, like tiny figure 8s. I've had to add more practice time because the bike is so right there, especially with the rejet, I need more finesse. I've never had the front end come up even when piling on the rpms, but I never drop the clutch. The bike can slide me back in the seat even harder and quicker if I really crank on the throttle. That's plenty of excitement factor for me. 

[the mole]

Just changed my standard 16 for a 17 and I'm loving it for my highway commute. Keeps my rpm under 6,000 at 110kph (68mph) speed limit. Seems smoother running than it was at 6200 and I hope to improve the economy. Fuel here is getting over $1.70 a litre now ($6.80 a US gallon). I used to get 24km/litre=60mpg (US gallon) and I go 110km each way to work.

[08GSSteve]

Hey mole are you sure you are running a stock rear?

My new 08 in top gear runs
(stock front and rear)
100km/hr = 5000rpm
110km/hr = 5500rpm

change your rear as well mate and your rpm's will drop more.

[reminor]

To each his own  This mod is so easy (~30 minutes including the chain adjustment) that you can go back and forth (15T to 17T) at any time.

So far I am enjoying 15T on the highway and not going back to 17T again, even though my 17T gave me about 500rpm less at a given speed (in 6th). Another advantage, when the speed drops to 45-50mph I am still in 6th to pass. With 17T I'd need to switch to 5th for sure. The thing I like a lot is more pickup, all the way up from 2500-2800rpms. With 17T the torque under 3000rpms was virtually non existing. It's not gobs of torque by any means, but still a nice change. Similar like feeling when riding down hill, all of the sudden the bike has more power and agility.

I wish the gears on GS500 were taller (more spread between them with regards to ratio). I find myself skipping gears every time I accelerate on ramp (going 1st -> 3rd -> 6th). Just no need for such close steps. My rpms drop just about 1500rpm on each following gear. I wish GS engineers went with more like 2500rpms between the gears. I wonder if other bikes have taller gears? Any experience?


Gas mileage update. With my latest fill up I went 140 miles on 2.6gal (i.e. ~54mpg). That's with 15T, 90% highway @ 75-80mph and one 40mph two-up joyride ~25 miles. Not bad.

[Suzuki Stevo]

With a 17T I pulled off 69.8 MPG in 90° weather, gas station to gas station Hwy riding. I have a 15T also...if I stayed off the interstate the 15T would be my choice, other than that I prefer the 17T over the stock gearing.

[pjm204]

I am considering going up to a 17 or 18tooth. I ride everywhere, back roads, highway, around town, but I seem to spend the most time in the 70-80(indicated) mph range. I don't really like running the engine at 6500rpms so I figure picking up some teeth will definitely help. If I wanted to do wheelies I would have gotten a different bike.

[the mole]

Hey mole are you sure you are running a stock rear?

My new 08 in top gear runs
(stock front and rear)
100km/hr = 5000rpm
110km/hr = 5500rpm

change your rear as well mate and your rpm's will drop more.

Yes, stock rear. The speeds I'm quoting are true speed, checked by GPS. My speedo overreads 10% which is typical for a GS.
It doesn't matter whether you change front or rear or both sprockets, its the overall ratio that matters (back/front). If I want a taller ratio than the 17 gives me, its cheaper to go to an 18 than to change the rear.