Sprockets

[jacob11379]

Since I can remember I always did 1 tooth down in the front and one or two up in the back, but that was on street bikes.

I have a couple track bikes that were modified prior to me buying them. One I believe is 1 down 3 up and the other is 1 down 5 up....

Now I have a bike that the teeth have not been changed yet. But I realize I dont really know the difference in how the bike will respond with teeth in the front or rear being modified. Yes i understand itll be quicker, and more torque which increases wheelie and instability with throttle/not good in corners at some point.

My question is simply whats the difference if any between front and rear modifications in sprocket?

For example, lets say your sweet spot on said track is 1 down 4 up. whats the difference between going 2 down and stock rear, or stock front and 7 up? etc

 

[stangmx13]

"1 down / 3 up" is a poor way to talk about gearing. just list the actual teeth AND the chain length. for example, a combo i like on my R6 is 15/43-114.

the main difference between everything u listed is the location of the rear axle. axle position is very important at the track. each tooth will generally move the axle ~4mm, while 2 links moves the axle ~16mm. so 15/44-114 is 4mm closer than 15/43-114. 15/44-116 is 8mm longer than 15/42-114. etc etc.

there are other small effects with anti-squat and chain pull when changing gear ratios. but they are so small compared to the effects due to axle position that they arent worth worrying about for most riders.

 

[jacob11379]

"1 down / 3 up" is a poor way to talk about gearing. just list the actual teeth AND the chain length. for example, a combo i like on my R6 is 15/43-114.

the main difference between everything u listed is the location of the rear axle. axle position is very important at the track. each tooth will generally move the axle ~4mm, while 2 links moves the axle ~16mm. so 15/44-114 is 4mm closer than 15/43-114. 15/44-116 is 8mm longer than 15/42-114. etc etc.

there are other small effects with anti-squat and chain pull when changing gear ratios. but they are so small compared to the effects due to axle position that they arent worth worrying about for most riders.

Good to know....

I think I found answer to my question. Simply divide rear sprocket size by front sprocket size to get drive size.

15/44 is 2.93
16/47 is 2.94
17/50 is 2.94

Doesnt seem to matter which one is changed

 

[csik magnet]

Good to know....

I think I found answer to my question. Simply divide rear sprocket size by front sprocket size to get drive size.

15/44 is 2.93
16/47 is 2.94
17/50 is 2.94

Doesnt seem to matter which one is changed

For final drive ratio, yes a (for example) 15/45 is identical to a 14/42 or a 16/48; all 3 give you a ratio of 3.00. There can be some caveats, like on a R6 running a 14 tooth front sprocket will rub the chain guide too much.
Like Robert said, axle position will vary for each gear set (unless you're changing your chain length with each one as well, and even that can only be done in steps of 2 links). Moving the axle in will be a bit more responsive, moving it out yields more stability. I don't notice a difference in how the bike handles with a 48 sprocket vs. a 46 with the same chain, and that's almost a centimeter of wheelbase! But the effect is still there (also I'm not the most discerning rider, I'm sure some others would pick up on it immediately).

I think a lot of people start with 1 down/1-2 up for the track because it gets you gearing that's better suited for it AND it lets you keep the same chain without your axle moving very much and throwing off your wheelbase.

 

[jacob11379]

For final drive ratio, yes a (for example) 15/45 is identical to a 14/42 or a 16/48; all 3 give you a ratio of 3.00. There can be some caveats, like on a R6 running a 14 tooth front sprocket will rub the chain guide too much.
Like Robert said, axle position will vary for each gear set (unless you're changing your chain length with each one as well, and even that can only be done in steps of 2 links). Moving the axle in will be a bit more responsive, moving it out yields more stability. I don't notice a difference in how the bike handles with a 48 sprocket vs. a 46 with the same chain, and that's almost a centimeter of wheelbase! But the effect is still there (also I'm not the most discerning rider, I'm sure some others would pick up on it immediately).

I think a lot of people start with 1 down/1-2 up for the track because it gets you gearing that's better suited for it AND it lets you keep the same chain without your axle moving very much and throwing off your wheelbase.

I havent been able to pick up much feel on wheel placement yet. Actually one of my bikes has the rear tire as far back as it can possibly go and shims to raise the rear end. Feels great to me....:nchantr

New bike ill ride and see how it feels and go from there. Specs say "the transmission is close type ratio with 2nd-6th shortened". Dont know how that corresponds to actual track riding but I should see here real soon....:ride

Appreciate the feedback

 

[abominablestein]

slightly off topic... for the r6, does the rear tire warmer rub against the chain for yall?

have a new to me r6 and tire warmers and it seems like a point that might wear out.

sorry for the hijack!

 

[jaybocc2]

slightly off topic... for the r6, does the rear tire warmer rub against the chain for yall?

have a new to me r6 and tire warmers and it seems like a point that might wear out.

sorry for the hijack!

does on all bikes mostly a bit.

 

[jaybocc2]

I havent been able to pick up much feel on wheel placement yet. Actually one of my bikes has the rear tire as far back as it can possibly go and shims to raise the rear end. Feels great to me....:nchantr

New bike ill ride and see how it feels and go from there. Specs say "the transmission is close type ratio with 2nd-6th shortened". Dont know how that corresponds to actual track riding but I should see here real soon....:ride

Appreciate the feedback

always as far back as possible.

I run 16/43-116 iirc for longest wheelbase and most oomph on my gen4 ... may eventually swap to 16/42... gen5 is different gearbox so different gearing.

 

[csik magnet]

slightly off topic... for the r6, does the rear tire warmer rub against the chain for yall?

have a new to me r6 and tire warmers and it seems like a point that might wear out.

sorry for the hijack!

My warmers rub the chain, but it's not getting pinched/squeezed or anything. I'm sure the rubbing causes some wear but I don't think it'll ever wear out due to that.

What size rear tire are you running?

 

[stangmx13]

Optimal gearing is dependent on the track and rider pace. It’s likely that most everyone will need to go taller as they get faster. Extra corner speed requires taller gearing to take that 2nd gear corner in 2nd without being too high in the rev range. Plus, clicking 3rd or running shorter to definitely use 3rd is often slower because of reduced drive force and losing lap time from too much shifting.

+1 on keep the axle back. You won’t find many (if any) fast racers with their axle in the front half of the adjustment on a stock swing arm.

 

[jmann]

Optimal gearing is dependent on the track and rider pace. It’s likely that most everyone will need to go taller as they get faster. Extra corner speed requires taller gearing to take that 2nd gear corner in 2nd without being too high in the rev range. Plus, clicking 3rd or running shorter to definitely use 3rd is often slower because of reduced drive force and losing lap time from too much shifting.

+1 on keep the axle back. You won’t find many (if any) fast racers with their axle in the front half of the adjustment on a stock swing arm.

Is 15/45 or 15/47 taller? Just making sure for future reference. Thanks.

 

[stangmx13]

Is 15/45 or 15/47 taller? Just making sure for future reference. Thanks.

taller == more speed for a given rpm
shorter == less speed for a given rpm

15/45 is taller than 15/47
16/45 is taller than 15/45

 

[abominablestein]

just running 180. it's probably fine, i'm just being paranoid with the side of my new warmers getting a little dirty.

My warmers rub the chain, but it's not getting pinched/squeezed or anything. I'm sure the rubbing causes some wear but I don't think it'll ever wear out due to that.

What size rear tire are you running?

 

[Holeshot]

I havent been able to pick up much feel on wheel placement yet. Actually one of my bikes has the rear tire as far back as it can possibly go and shims to raise the rear end. Feels great to me....:nchantr

New bike ill ride and see how it feels and go from there. Specs say "the transmission is close type ratio with 2nd-6th shortened". Dont know how that corresponds to actual track riding but I should see here real soon....:ride

Appreciate the feedback

IMO, don’t change the bike much. Ride it. There’s several guys running 10R’s in the AFM. Check in with an AFM tuner for a good idea of if your bearing is spot on. But, assuming the bike was set up well (and that’s a big assumption), run it!

always as far back as possible.

I run 16/43-116 iirc for longest wheelbase and most oomph on my gen4 ... may eventually swap to 16/42... gen5 is different gearbox so different gearing.

I guess to each’s own...I’m setup pretty darn short. Kinda not optimum in some places, but man it goes around Thill T3 like stink and works for how I ride best.

 

[jaybocc2]

IMO, don’t change the bike much. Ride it. There’s several guys running 10R’s in the AFM. Check in with an AFM tuner for a good idea of if your bearing is spot on. But, assuming the bike was set up well (and that’s a big assumption), run it!



I guess to each’s own...I’m setup pretty darn short. Kinda not optimum in some places, but man it goes around Thill T3 like stink and works for how I ride best.

Lol short jokes aside... 16/43 is pretty dang short when coming from 17/39 stock �� I get pretty deep into 6th on the front straight off thill east

I like it I find I actually shift less than taller gearing

That said I ran stock gearing until my second afm round so it doesn't hurt to try different things to see what works.

 

[trey]

I’ve been running 16/37-39 on my 18’ zx-10. Make sure you change the ecu for whatever gearing and tire diameter you are running. The Kawi electronics are sensitive to those changes.

 

[Holeshot]

I’ve been running 16/37-39 on my 18’ zx-10. Make sure you change the ecu for whatever gearing and tire diameter you are running. The Kawi electronics are sensitive to those changes.

Excellent advice on tire diameter. That'll be a problem if not addressed.

Lol short jokes aside... 16/43 is pretty dang short when coming from 17/39 stock �� I get pretty deep into 6th on the front straight off thill east

Shoot, I meant chain length. My bad. Girth is THICK, tho...

 

[jacob11379]

Is there an easy way to add links to a chain, tool available, or should it go to a shop?

 

[stangmx13]

Is there an easy way to add links to a chain, tool available, or should it go to a shop?

the ez way is get a new chain and cut that one longer.

i have seen a few chains with multiple master links at the track. ive also seen a few chains with multiple master links break off. its not something im willing to do.

 

[trey]

Is there an easy way to add links to a chain, tool available, or should it go to a shop?

I’ve been running my chain length at 605mm ish, which is about the mid point on the adjustment of the axle. Obviously changes a small bit depending on gearing selection. You will get a whole lot of advice on where to position the rear axle. A lot depends on riding style and electronics. It’s always a give and take. With it far back, you will help keep it from lifting the front. If you run it shorter, the bike will turn better, and the lifting the front can be prevented with electronics. Again, lots of ways to do it, and none are perfect.