Experience with sprocket changes | GTAMotorcycle.com

Experience with sprocket changes

Oppoe

Well-known member
Thinking about doing a sprocket change to a +2 in rear, how much acceleration would I expect? 15% increase? Is something like a -1 front +2 an insane difference? I've used some sites to calculate the changes but none give examples of how much faster the bike will accelerate.

Also any vendors you recommend? Best chain/sprocket material for street use? Best bet to go with a 520 chain if doing a change?
 
Thinking about doing a sprocket change to a +2 in rear, how much acceleration would I expect? 15% increase? Is something like a -1 front +2 an insane difference? I've used some sites to calculate the changes but none give examples of how much faster the bike will accelerate.

Also any vendors you recommend? Best chain/sprocket material for street use? Best bet to go with a 520 chain if doing a change?

What kind of bike? Bigger noticable difference on smaller bikes. Still a noticeable difference on bigger bikes but not worth the money on the street for me, since 600cc+ sports bikes are already over powered for street use. If I was changing the sprockets from wear and tear, maybe I'd consider it. If you go to the track, it'll add to the fun.

I've gone -1 front / +2 rear on a few bikes, both street and track. I think that's around the limit unless you're stunting and want a dinner plate as a back sprocket.
 
Steel sprockets last longer than aluminium. Going to a 520 for street use for saving weight isn't of much benefit. Might save a bit on cost maybe.
 
As a first approximation, acceleration increase should be directly correlated to the change in ratio. If the calculator shows a 15% change in ratio, expect 15% faster acceleration. Obviously there are exceptions (more gear changes required to achieve certain speeds, you may be past the hp peak at certain speeds etc), but on the street these won't be a big deal.
 
If you haven't seen it, try this site. You can see the difference in top speed etc with different sprockets.
https://www.gearingcommander.com/

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Thinking about doing a sprocket change to a +2 in rear, how much acceleration would I expect? 15% increase? Is something like a -1 front +2 an insane difference? I've used some sites to calculate the changes but none give examples of how much faster the bike will accelerate...

at the risk of stating the obvious:
It will certainly have you shifting gears earlier and slightly more often, if or how much faster the bike will accelerate kinda depends on how awesome are you at upshifting at precisely the right time and how much top speed you are willing to sacrifice to increase your potential to accelerate.
... gear it too low for your particular ride and in real life you will end up yielding faster acceleration times by launching in second gear instead of first!

Is a mistake to simply assume lower gearing will always relate to faster acceleration, there are too many other variables to consider such as weight and the power delivery characteristics of your particular engine, trial and error testing is the normal way to prove or test real life results of gear ratio changes. Rule of thumb is one tooth change on the countershaft sprocket is noticeable but subtle, a one or 2 tooth change in the rear sprocket is less noticeable or near non-existent simply because of the math. (countershaft sprockets are typically 1/3 ~ 1/4 the size of your rear sprocket so 1 tooth change on front relates to 3 or 4 tooth change on rear)

Does your bike have a close or wide ratio transmission? Some manufacturers equip their production bikes with internal gear ratios that are less then ideal for pure performance considerations, but the intent is to make the bike more ridable for the street. If your bike has a wide ratio transmission and one or two of the gears has less than optimal ratios then attempting to address that issue at the final drive can result in less than desirable overall results.
 
Thinking about doing a sprocket change to a +2 in rear, how much acceleration would I expect? 15% increase? Is something like a -1 front +2 an insane difference? I've used some sites to calculate the changes but none give examples of how much faster the bike will accelerate.

Also any vendors you recommend? Best chain/sprocket material for street use? Best bet to go with a 520 chain if doing a change?

it'll be enough of a difference to put a smile on your face, don't know how one would quantify that in %, what bike is it for?
 
What kind of bike? Bigger noticable difference on smaller bikes. Still a noticeable difference on bigger bikes but not worth the money on the street for me, since 600cc+ sports bikes are already over powered for street use. If I was changing the sprockets from wear and tear, maybe I'd consider it. If you go to the track, it'll add to the fun.

I've gone -1 front / +2 rear on a few bikes, both street and track. I think that's around the limit unless you're stunting and want a dinner plate as a back sprocket.

ye but 600s generally lack torque down low, and its especially noticeable on the street when you are constantly stop and go
 
ye but 600s generally lack torque down low, and its especially noticeable on the street when you are constantly stop and go

Lack torque? compared to maybe a minivan, or a big cruiser, sure. Still more than enough for normal street use. Being in fetal position in stop and go is more of an issue than engine characteristics.
 
Lack torque? compared to maybe a minivan, or a big cruiser, sure. Still more than enough for normal street use. Being in fetal position in stop and go is more of an issue than engine characteristics.

whats the definitions of enough? a cbr 125 is more than enough for normal street use
compared to its peak output the amount you get at 3000 rpm is low, and you have to rev them quite a bit for them to feel exciting on the street, a simple solution to that is a change of gearing
 
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I never notice much difference on 600cc+ bikes. Some 250s and thumpers come geared lower than necessary, it makes starting easier for beginners. Narrowing the sprocket ratio helps on small bikes.
 
whats the definitions of enough? a cbr 125 is more than enough for normal street use
compared to its peak output the amount you get at 3000 rpm is low, and you have to rev them quite a bit for them to feel exciting on the street, a simple solution to that is a change of gearing

I guess it depends on the user. 0-3k rpm and 3k to powerband is still pretty exciting to me on the street for a 600cc sports bike.

8k to peak wide open is just banging a stripper. More fun than "normal" sex but can't be doing that all the time.
 
Bike is a 17 gsxs 750. Was just thinking of a sprocket swap to open up the bike more in lower rpms, no point in having top end power. Also some nice bling

On gearingcommander I have to input 2011 gsr 750 (same bike) and it's showing me that a -1 front +2 rear increases top end and lowers acceleration, isn't this wrong or am I totally misreading it?
 
Bike is a 17 gsxs 750. Was just thinking of a sprocket swap to open up the bike more in lower rpms, no point in having top end power. Also some nice bling

On gearingcommander I have to input 2011 gsr 750 (same bike) and it's showing me that a -1 front +2 rear increases top end and lowers acceleration, isn't this wrong or am I totally misreading it?

Take a screen grab. Down in the front and up in the rear absolutely increases acceleration and decreases top speed.
 
One or two teeth more on the rear will make a noticeable difference if you want a little more grunt down low. One tooth down on the front (equal to three up on the back) was a bit too much on the street for me. Required too much shifting, more engine vibration as well as shortening your chain life.Absolutely no reason to go with an aluminum sprocket on the street.Won’t last nearly as long as steel and no noticeable benefit.
 
Bike is a 17 gsxs 750. Was just thinking of a sprocket swap to open up the bike more in lower rpms, no point in having top end power. Also some nice bling

On gearingcommander I have to input 2011 gsr 750 (same bike) and it's showing me that a -1 front +2 rear increases top end and lowers acceleration, isn't this wrong or am I totally misreading it?

Nope, it don't work that way, your engine is simply going to be reving faster at any given road speed and you are going to need to shift sooner because you will hit redline at a lower road speed. Lowering the gearing might help your bike to attain redline in top gear and there is some indication that change has been applied to the 2018 model, so you might actually be on the right track with a one tooth smaller front sprocket gearing change.

Suzuki specs say your engine has a 72mm bore and 46mm stroke (very over-square) <- that is why your engine is suited to high horsepower at high engine revs, if you wanted something with low end grunt at the cost of high end performance you should have bought a bike with a longer stroke. You bought a screamer, make her scream!

For a real life example in practice take a look at stunt bike setups, tiny front sprocket and huge rear sprocket makes for a bike that you can walk behind in first gear but sucks for top speed performance.
 
If you care about durability, don’t bother with a 520. Sounds like you may get a few years out of that if your lucky from what I gather your after. Keep it stock and just rev the bike more if you want the acceleration out of the hole. Unless your racing then durability goes out the window. Stock gearing and steel, the japs got it right for street riding.
 

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