Some of you know a little about me and how I ride.
I am thinking of gearing the GS down by swapping the front sprocket. Mostly I want to reduce the acceleration difference between my GS and my Triumph, and also since I have the Triumph for highway use, I can afford to sacrifice a bit of highway buzziness for acceleration on the GS and make it more of a targeted lower-speed vehicle.
Anyway.
I have read a jillion posts about this, and the consensus seems to be either that going down to a 15t makes no noticeable difference or that going to a 15t makes the bike crazy hooliganish. Anyway, I'm considering actually going to 14t. So the question is, should I go straight to 14t on the first shot, or is that going to be too extreme and I really will be happy with 15t?
Again, I am not worrying about commuting and noise or mpg here. Looking for a bit more pep in the step. I don't mind shifting more.
Hey Mr72... long time since our last chat...
I do not have any info about it, but I get interested ( Actually as I do not have a more powerful bike,, so I am very happy with the GS acceleration LOL)...
I founded this
https://www.bikechatforums.com/viewtopic.php?t=252138
maybe can help you!
I'm leaning towards just going for the gusto and putting on a 14. Currently in top gear I turn about 4K rpm at 60mph and this would result in only about a 600rpm increase at that speed according to my math (about a 15% increase in gearing). That's not horrible. Seems like a 15% increase in torque at the rear wheel is not likely to turn the GS into an uncontrollable wheelie machine.
You could just go for the 14 and if it's too much, split the difference with a 15.
Have you tried to find +3 or +6 rears? I ask because going down on the front increases chain wear because it's going around a smaller radius. While other setups have smaller fronts on higher output engines, I prefer to reduce the effects on the existing maintenance schedule.
I also ask because comparing a GS and a Triumph, two down may not be enough.
Quote from: Falken Hawke on January 18, 2019, 08:09:33 PM
going down on the front increases chain wear because it's going around a smaller radius.
Interesting concept. It's the first I've ever heard of it.
Can you provide any evidence to support this claim?
I can.....it's down to a phenomena known as chordal action or chordal effect. In simple terms the lower the number of teeth on a sprocket the More the chain will vibrate as it passes over it and obviously the More the chain vibrates the shorter it's lifespan.
http://chain-guide.com/basics/2-2-1-chordal-action.html
And of course you have to consider what effect the increase in vibration will have on other components and the ride quality.
I am with Falken on this, far better to alter the larger rear sprocket, at least from an engineering point of view.
No. Parts are long discarded. Besides, even if I did still have them, variables such as maintenance is inconsistent over time, weather conditions, etc., etc. Basically, no one outside a lab will have evidence.
Individual experiences will vary based on what was tried and experienced. Other common variables are the vehicle, its use, the rider, and the specific parts. I'm not saying don't go two down but rather that there may be results that are otherwise not desirable.
Quote from: Falken Hawke on January 18, 2019, 08:09:33 PM
Have you tried to find +3 or +6 rears? I ask because going down on the front increases chain wear because it's going around a smaller radius. While other setups have smaller fronts on higher output engines, I prefer to reduce the effects on the existing maintenance schedule.
I also ask because comparing a GS and a Triumph, two down may not be enough.
Yes I considered it. But not for the reason you mentioned, which I also did in fact consider as well. :) Too many years mountain biking, I'm fully aware of the wear factor. It's not only the chain but the sprocket itself will wear more quickly with fewer teeth.
I considered going up a couple of teeth on the rear in conjunction with going down in the front in order to keep the overall chain length the same. I haven't gone out and measured how much slack I can take up with the chain adjusters but I don't want to have to cut the chain when switching;
This brings up other options of perhaps going down to 15t in front and up to 40t in rear, which will give me something slightly between my previous two options.
Regarding the difference with the Triumph, well it has 70% more torque than the GS, but the gearing on that bike is very different and the torque curve is a lot wider. I did a (not-so) quick and (pretty much) useless set of calculations to compare. Counting the primary drive and final drive ratios, I calculate that stock, the bike is traveling about 10% slower across the board in each gear 1-5 on the GS when the engine reaches the torque peak than the Triumph is, but also this gives about a 1.1x torque multiplier. So to get the GS to have a similar torque feel I would have to increase the gear ratio by about 50%, which is not possible. So there simply is no way to get the GS to "feel" like it has as much torque off the line as the Triumph by gearing changes.
One funny thing is that if I go with a 14t front sprocket on the GS then when calculating the primary drive and final drive along with the transmission gear ratios, 6th gear in the GS will be almost exactly the same as 3rd gear on the Triumph. That's nuts! But maybe that's acceptable. I'd be turning nearly 5K rpm at 55mph on the GS with a 14t front sprocket and my current rear tire (140/70). The good news I guess is that would be an indicated 65+ mph.
And... I'm ok with all of that. So now I'm even thinking I might as well go totally nuts and get a 14t front sprocket and a 41t rear and swap the whole thing. I won't likely be doing long stretches at 60mph on the GS, I have a Triumph for that. With that gearing, at 45mph-50mph, which is really the more realistic top cruising speeds I get to on the GS, I would only be turning 4200-4500 rpm. That's not horrible. And I happen to know my GS is quite peppy at 4500 rpm, nothing wrong with that. If I have to take a stretch of 60-65mph it's well within the reasonable cruise range of the GS, it'd just be loud and probably get crappy mpg and make me want to get back on the back roads ASAP. But that bike would be a back-road monster with that gearing.
I think I'm going to do it. That should inject a big chunk of extra character into the old GS.
Quote from: Falken Hawke on January 19, 2019, 02:58:00 AM
Basically, no one outside a lab will have evidence.
Which means to me "you won't notice a difference."
I'm sure things like chain lubrication schedule and sprocket alignment have far bigger impacts on chain life than the sprocket size.
Quote from: sledge on January 19, 2019, 02:41:13 AM
I can.....it's down to a phenomena known as chordal action or chordal effect. {Snip}
Interesting.
Thanks for the info.
Quote from: mr72 on January 18, 2019, 06:39:16 AM
...Currently in top gear I turn about 4K rpm at 60mph....
That seems a low rpm! I thought it was closer to 5K at that speed. I'll have to go out and check.
btw, I presume you've seen the https://www.gearingcommander.com site but I'll put it here anyway.
Yes that web site was a big help in calculating a lot of this for me!
It should be noted that it shows actual speeds and not indicated GS500 speedo speeds :)
I had to re read this original post in order to figure out exactly what it is that you are trying to achieve here.
The key is that you don't care about top speed.
But trying to get the same performance of a higher HP bike by simply lowering the gear ratio(s)....ehhhh.
The only possible difference you're gonna feel, with lower gear, is the "hole shot" from a standing stop.
Once you start moving....the Engine RPM / Wheel speed / wheel torque/ curve is gonna be exactly the same..EXCEPT...
The shift points are gonna happen at a slower wheel speed.
You only have a set amount of HP....
HP = torque x RPM (at the wheel, not at the engine)....
If you increase the torque (lower first gear) the the RPM is reduced.....essentially no difference in performance! (except that first 1/4 second at the hole shot)....
If it were so easy as changing gear ratios...then just put lower gear on the triumph an blow away all the competition.
If you want to go faster, or accelerate quicker....it requires more HP...
Good luck...anxious to see the results....(not just that it "feels" better, but some concrete numbers)
Cookie
Quote from: mr72 on January 17, 2019, 03:56:44 PM
Some of you know a little about me and how I ride.
I am thinking of gearing the GS down by swapping the front sprocket. Mostly I want to reduce the acceleration difference between my GS and my Triumph, and also since I have the Triumph for highway use, I can afford to sacrifice a bit of highway buzziness for acceleration on the GS and make it more of a targeted lower-speed vehicle.
Anyway.
I have read a jillion posts about this, and the consensus seems to be either that going down to a 15t makes no noticeable difference or that going to a 15t makes the bike crazy hooliganish. Anyway, I'm considering actually going to 14t. So the question is, should I go straight to 14t on the first shot, or is that going to be too extreme and I really will be happy with 15t?
Again, I am not worrying about commuting and noise or mpg here. Looking for a bit more pep in the step. I don't mind shifting more.
Quote from: twocool on January 20, 2019, 06:02:56 AM
I had to re read this original post in order to figure out exactly what it is that you are trying to achieve here.
But trying to get the same performance of a higher HP bike by simply lowering the gear ratio(s)....ehhhh.
Well, that's not what I am intending to do. Just trying to reduce the big difference in feel when going from one bike to the other.
Quote
The only possible difference you're gonna feel, with lower gear, is the "hole shot" from a standing stop.
Yes, which is precisely where there is the biggest difference from one bike to the other.
Quote
Once you start moving....the Engine RPM / Wheel speed / wheel torque/ curve is gonna be exactly the same..EXCEPT...
The shift points are gonna happen at a slower wheel speed.
That's not true at all, because the GS's engine does not make the same amount of torque across the entire rev range.
You are correct that the shift points will happen at a lower speed, of course that's the entire point. But it's not a linear change.
Quote
You only have a set amount of HP....
HP = torque x RPM (at the wheel, not at the engine)....
divided by 5252 ... horsepower = torque (ft-lb) * RPM / 5252. ... at the wheel, or at the engine, same math.
With lower gearing, there is more torque applied across the entire rev range at the wheel in every gear. It may be true that, for example, there is no more torque in 6th gear at a certain engine speed than there was with previous gearing in 5th gear, but everyone knows that at 60mph you accelerate quicker in 5th gear than in 6th. So lowering the final drive ratio will increase acceleration in every gear because it increases delivered torque in every gear. What it doesn't do is make you shift any faster, so the overall acceleration measured outside of one gear may not be improved and may even be worse, who knows.
But in any case, going from 20 to 40 mph in 2nd gear will happen quicker with the reduced gear ratio than it would otherwise. Of course you will be revving higher, which is the point. Same for going from 40 to 60 in 4th gear, or from 0-20 in first gear, or from 30-50 in 3rd gear, etc. You only have to "shift more" if you are accelerating a wider range of speed than can be covered in one gear, which is just about the same range as before, just slightly different speeds for each gear.
Quote
If you increase the torque (lower first gear) the the RPM is reduced.....essentially no difference in performance! (except that first 1/4 second at the hole shot)....
The RPM is increased. And there is a theoretical difference in performance. More torque equals faster acceleration, in each gear.
Consider: stock gearing, the GS hits the hp peak in 3rd gear at about 74 mph. With my gearing change, it will hit the hp peak in third gear at about 65 mph. In either case you have to shift twice to go from 0-60mph but in the case of the lower gearing, you reach the hp peak in each gear. So a stock GS will probably go quicker from 0-75 mph where it can do it in two gear changes vs my gearing suggestion which will require a 3-4 shift just before hitting 75, but the lower-geared bike will go quicker 0-60.
Quote
If it were so easy as changing gear ratios...then just put lower gear on the triumph an blow away all the competition.
You certainly could, but the Triumph has such a wider torque curve than the GS, the gearing makes much more sense like it is. FWIW I don't think the Triumph is really any quicker in actual stopwatch timing to speed than the GS. It just feels much more responsive due to 70% more torque at any time, meaning it doesn't need the (wheel) rpms to make the same power. To get the same power on the ground I have to increase wheel RPM on the GS by 70%. In the end this will mean the GS needs 6 gears to cover the same speed range that the Triumph does in 3. But that's totally OK if I am never going to be cruising over 50 mph.
Quote
If you want to go faster, or accelerate quicker....it requires more HP...
Faster, like faster top speed, you are correct, more total HP. But quicker just requires more HP at the ground, which can be achieved by increasing leverage through gearing. The tradeoff of course is not only top speed but also wear and tear on the engine and reduced comfort at highway speeds.
Quote
Good luck...anxious to see the results....(not just that it "feels" better, but some concrete numbers)
I won't have any concrete numbers, I [almost] only care about if it feels better.
Sooooo........
Let's do this..........
You have lower gear ratio in each gear...i.e...your second gear is lower than my second gear right?...so you "think" you have more torque....and somehow go faster..or accelerate faster...
But...My second gear is lower than your third gear Right? So I just stay in second longer...I have now more torque (according to the way you think)
To get the fastest possible acceleration, you have to run the engine up to redline, then shift....doesn't matter the actual gear ratio, only that you run to redline and shift....this produces the max HP, the most of the time....
Lowering the overall gear ratio, only matters from a dead stop.....you can draw the curves....other than the shift points...and the start point and the end point, they are the same.
Do the gear change...it will "
feel" better to you...it won't
be any better but it will feel better to you...it will never "feel" like a more powerful bike, no matter what you do to the gearing.
Cookie
Quote from: mr72 on January 20, 2019, 06:50:19 AM
Quote from: twocool on January 20, 2019, 06:02:56 AM
I had to re read this original post in order to figure out exactly what it is that you are trying to achieve here.
But trying to get the same performance of a higher HP bike by simply lowering the gear ratio(s)....ehhhh.
Well, that's not what I am intending to do. Just trying to reduce the big difference in feel when going from one bike to the other.
Quote
The only possible difference you're gonna feel, with lower gear, is the "hole shot" from a standing stop.
Yes, which is precisely where there is the biggest difference from one bike to the other.
Quote
Once you start moving....the Engine RPM / Wheel speed / wheel torque/ curve is gonna be exactly the same..EXCEPT...
The shift points are gonna happen at a slower wheel speed.
That's not true at all, because the GS's engine does not make the same amount of torque across the entire rev range.
You are correct that the shift points will happen at a lower speed, of course that's the entire point. But it's not a linear change.
Quote
You only have a set amount of HP....
HP = torque x RPM (at the wheel, not at the engine)....
divided by 5252 ... horsepower = torque (ft-lb) * RPM / 5252. ... at the wheel, or at the engine, same math.
With lower gearing, there is more torque applied across the entire rev range at the wheel in every gear. It may be true that, for example, there is no more torque in 6th gear at a certain engine speed than there was with previous gearing in 5th gear, but everyone knows that at 60mph you accelerate quicker in 5th gear than in 6th. So lowering the final drive ratio will increase acceleration in every gear because it increases delivered torque in every gear. What it doesn't do is make you shift any faster, so the overall acceleration measured outside of one gear may not be improved and may even be worse, who knows.
But in any case, going from 20 to 40 mph in 2nd gear will happen quicker with the reduced gear ratio than it would otherwise. Of course you will be revving higher, which is the point. Same for going from 40 to 60 in 4th gear, or from 0-20 in first gear, or from 30-50 in 3rd gear, etc. You only have to "shift more" if you are accelerating a wider range of speed than can be covered in one gear, which is just about the same range as before, just slightly different speeds for each gear.
Quote
If you increase the torque (lower first gear) the the RPM is reduced.....essentially no difference in performance! (except that first 1/4 second at the hole shot)....
The RPM is increased. And there is a theoretical difference in performance. More torque equals faster acceleration, in each gear.
Consider: stock gearing, the GS hits the hp peak in 3rd gear at about 74 mph. With my gearing change, it will hit the hp peak in third gear at about 65 mph. In either case you have to shift twice to go from 0-60mph but in the case of the lower gearing, you reach the hp peak in each gear. So a stock GS will probably go quicker from 0-75 mph where it can do it in two gear changes vs my gearing suggestion which will require a 3-4 shift just before hitting 75, but the lower-geared bike will go quicker 0-60.
Quote
If it were so easy as changing gear ratios...then just put lower gear on the triumph an blow away all the competition.
You certainly could, but the Triumph has such a wider torque curve than the GS, the gearing makes much more sense like it is. FWIW I don't think the Triumph is really any quicker in actual stopwatch timing to speed than the GS. It just feels much more responsive due to 70% more torque at any time, meaning it doesn't need the (wheel) rpms to make the same power. To get the same power on the ground I have to increase wheel RPM on the GS by 70%. In the end this will mean the GS needs 6 gears to cover the same speed range that the Triumph does in 3. But that's totally OK if I am never going to be cruising over 50 mph.
Quote
If you want to go faster, or accelerate quicker....it requires more HP...
Faster, like faster top speed, you are correct, more total HP. But quicker just requires more HP at the ground, which can be achieved by increasing leverage through gearing. The tradeoff of course is not only top speed but also wear and tear on the engine and reduced comfort at highway speeds.
Quote
Good luck...anxious to see the results....(not just that it "feels" better, but some concrete numbers)
I won't have any concrete numbers, I [almost] only care about if it feels better.
If what you suggest were true then motorcycles would only have one gear.
This of course has been disproven over and over and is plainly explained with math. If sufficient traction is available and shift time is neglible then lower gears always result in quicker acceleration, at least until you reach the top speed limited either by redline or wind resistance.
Gearing down?
People were talking about it 16 years ago when I joined this forum. Its nothing new, it's nothing difficult and it's all been done before many many times before:dunno_black:
So instead of boring us all to death with endless paragraphs of meaningless and irrelevant talk why don't you just get on with it FFS?
We all know what the outcome will be and I hope very much it makes you happy!
ZZZzzzzzz
I agree with sledge...just do it and be happy! :woohoo:
Cookie
Quote from: mr72 on January 20, 2019, 09:03:01 AM
If what you suggest were true then motorcycles would only have one gear.
This of course has been disproven over and over and is plainly explained with math. If sufficient traction is available and shift time is neglible then lower gears always result in quicker acceleration, at least until you reach the top speed limited either by redline or wind resistance.
Quote from: sledge on January 20, 2019, 01:04:48 PM
Gearing down?
People were talking about it 16 years ago when I joined this forum. Its nothing new, it's nothing difficult and it's all been done before many many times before:dunno_black:
So instead of boring us all to death with endless paragraphs of meaningless and irrelevant talk why don't you just get on with it FFS?
We all know what the outcome will be and I hope very much it makes you happy!
ZZZzzzzzz
Posting something self-aggrandizing and useless?
You were doing this 2.5 years ago when I joined this forum. Its nothing new, it's nothing difficult and it's all been done before many many times before :dunno_black:
So instead of boring us all to death with endless posts of meaningless and irrelevant ego-stroking why don't you just stick to "engineering" FFS?
We all know what the outcome will be and I hope very much it makes you happy!
ZZZzzzzzz
I have also considered gearing down, but ultimately decided against it, purely because I'm planning on replacing the GS with a GSXR at some point soon and it seemed like a waste of time for me. If you do end up doing it, please document how it goes in your project thread, I'd be very interested to hear your impression of how the bike feels geared down.
I've played with 14, 15, 16, 17, and 18.
Suzuki got it right with 16. Works well for all scenarios. All the others come with compromises to some degree. If you are planning a long trip or really only plan on riding around in 1st and 2nd gear you could go for a 14 or 18. 15 and 17 just make you wish you had a 16.
I will post up about it on my project thread. I bought a 14/41 combo and plan to install it tomorrow. I might put the action camera on the tank and make a video of going 0-60 before and after just so we can get an idea of how much quicker it is, if at all.
EDIT:
Well I did go do a number of 0(or close)-60 runs with the stock gearing and the action camera on the handlebar aimed at the speedometer. Then I came home and took the rear wheel off and lo and behold, the 41t sprocket they sent doesn't have the correct bolt circle diameter. Oh well, I figured then I'd just do the front only, and as it turns out, the front sprocket they sent is also the wrong size. I should note that the part is labeled "JTF 565" which is what the wiki says is the right part, and also what Amazon's part matcher says is correct.
So it's a bust. I'm leaving the GS apart and ordering the right stuff.
See the other thread....I think the correct part number should be..... JTF 516
Cookie
Quote from: mr72 on January 25, 2019, 02:32:19 PM
I will post up about it on my project thread. I bought a 14/41 combo and plan to install it tomorrow. I might put the action camera on the tank and make a video of going 0-60 before and after just so we can get an idea of how much quicker it is, if at all.
EDIT:
Well I did go do a number of 0(or close)-60 runs with the stock gearing and the action camera on the handlebar aimed at the speedometer. Then I came home and took the rear wheel off and lo and behold, the 41t sprocket they sent doesn't have the correct bolt circle diameter. Oh well, I figured then I'd just do the front only, and as it turns out, the front sprocket they sent is also the wrong size. I should note that the part is labeled "JTF 565" which is what the wiki says is the right part, and also what Amazon's part matcher says is correct.
So it's a bust. I'm leaving the GS apart and ordering the right stuff.
the JTF565 is used only on Suzuki models:
GS400E (japan)
SFV 650
SV650
http://www.jtsprockets.com/catalogue/model/1944/
Best to consult JT catalog for accurate info...E bay and Amazon etc., will steer you wrong sometimes