twista
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posted November 04, 2007 11:40 AM
 Edited By: twista on 4 Nov 2007 11:42
gear ratio question
i have a 17 up front and since im gonna probably keep this bike,, what is the ratio for:
18/46 (stock)
17/46 (present setup)
17/49 (next potential)
im thinking of going to a 17/49 what will that do to the wheel base,, and will it want to come up drastically or is it doable on the regular street drive? any input is appreciated!
what is the difference between 17/46 and 18/49 which is taller,, and does anyone have a NEW 18 that they would be willing to trade for a 17Toofer?
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shiphteey
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posted November 04, 2007 02:34 PM
Twista, are you asking what the numerical ratio is? All you have to do is divide the rear sprocket number by the front sprocket number. For example 16/48 gearing would be 3:1 18/46 gearing is 2.56. 1 tooth change in the rear isn't that noticable but if I change it up at the strip or land speed racing, since I'm making a more concerted effort to go WOT I can now feel it.
Are you talking about making these gearing changes on a stock chain? If so I don't think 17/49 will fit, in fact I'm almost 100% sure it won't. I tried 17/48 and its too tight. Have you considered a 16 tooth? You could run 16/46 instead of 17/49 and it would be "close" but not the same, I'll let you bust out the calculator! 17/49 vs stock wheelbase....17/49 would be shorter.
If you want max wheelbase 16/44 is pretty nice. Its a 1/2 tooth more aggressive than 17/46 but you get tons more wheelbase so you can put the power down w/less wheelying.
I think it may help if you let us know WHAT is it you are trying to achieve ;-)
A.
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twista
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posted November 04, 2007 03:06 PM
Edited By: twista on 4 Nov 2007 15:10
ship,, i have the 17 up front and stock gear on back,, what would i have to go with to get a little more top end,, so right now its 17/46 if 46 is stock cant remember if its 46 or 48
but the front is the only thing changed at this point it is a 17,, and i got substantial low end out of changing the front sprocket,, NOW,, i have a new 49 tooth rear that i want to use,, SO,, what would i want to do if i want to fall in between where ia m at now and stock using the 49,,does 16/49 make sense?
so to sum it up i want a little more top end then where im at now with the 17 up front and the stock back,, how do i achieve it utilizing the 49 on back,, is it doable at all ,, or am i waisting my time,, i have a 120 link EKDVX2 as far as the chain is concerned..
also how many links are on the stock chain,, if you know.. thanx Ship Vic
one last thing is that the wheel base being on the short side is fine as i like winding it up in first and shifting clutchless and having the whell come up and riding it out thru a gear or two,, its less radical than powering up 1st and going thru them.. thanx again
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shiphteey
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posted November 04, 2007 05:39 PM
Well 18/46 is stock. That is 2.56 gearing.
17/46 is 2.71
With your proposed 49 tooth usage
18/49 is 2.72
17/49 would be 2.88.
So neither a 17 or an 18 would get you what you want (in between 17/46 and 18/46. As you can see 17/46 and 18/49 is pretty close, with 18/49 having a little more acceleration.
17/49 would be quite a handful! Going -1 in the front AND +3 in the rear, you will be wheelying a lot more!
On a side note, 16/46 would be the exact same gearing as 17/49. I would like to try that gearing but have yet to try it. The most aggressive gearing I have tried is 16/44, mainly because it gives you maximum wheelbase if you aren't adding/removing links to a stock length chain. Also, the gearing has a touch more acceleration than 17/46 (2.75 vs 2.71)
So to answer your question, technically speaking, using the 49 tooth won't allow you to gear in between stock 18/46 and 17/46 in terms of feel without going with a 19 tooth front sprocket! That would be 2.58 and would technically fall in between 2.56 and 2.71.
Since you have a 120 link chain then you may be fine since that is more links than stock.
Seems like the 49 tooth isn't the way to go for you if it involves buying a hard to find 19 tooth just to have a touch more acceleration than stock. In conclusion, yes, I think you are wasting your time but if you really like wheelies or are set up for drag racing its a good sized sprocket.
A.
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twista
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posted November 04, 2007 06:53 PM
Edited By: twista on 4 Nov 2007 19:13
excellent ,, well put and articulate,, thanx for the info Ship!,, i think im gonna try the 17/49 for shits and giggles and then wind up with a 2.6* ratio by going 18/47-48 or 17/44-45 does that make any sense,, and have you ever heard of the 17/49 being run on the street,, also this hard to come by 19 tooth front,, why are they hard to come by and were they stock fitment from another model and if so which one,, once again thanx for all the help,, i really appreciate it!
would you have any thing as far as sprockets that i might be interested in? and how many links does the stock chain have,, whats a good rule of thumb to use to know when the chain isnt long enough for a specific application,, is it as simple as not being able to get proper chain adjustment after the install,, or is there more to it? thanx
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shiphteey
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posted November 05, 2007 07:23 AM
Twista,
I haven't heard of anyone running 17/49 but that doesn't mean you can't! I'm sure someone has given the amount of 12s out there and the possibility for different cominations. Unfortunately no bike that I'm aware of comes with a 19 tooth front sprocket, thats pretty big! ZX-12s come with 18s, Busas, ZX-11s, ZX-14s come with 17. 16-17 is about the norm for beefier chained bikes. Since the 12 was really the only bike that came with an 18 tooth it presumably didn't make any sense to go to a 19 since people could just go -2 or -3 in the rear to run near what a 19 tooth would do. Also, I don't think you can just slap on a 19 tooth, you may need to remove your sprocket cover or do some grinding.
Bergie (RAC4IT) on the board has run a 19 tooth before and I think Vincent Hill has too.
My rear sprockets wouldn't fit your bike unless you are on BST Carbon Fiber wheels.
Personally I have a 16, 17, 18 and 19 for fronts and 44-46 for rears. I may pick up a 15 tooth one day but since the most agressive gearing to date that I have run is 16/44 it may make sense to try 16/45 and 16/46 before jumping to the 15 (why not just use what I got, right?)
I can't remember how many links the stock 12 chain has until I get to the shop today or tomorrow. Genearlly speaking, if you go -1 in the front you can usually go +1 in the rear at the same time and have near the same wheelbase, give or take. Some bikes you can go -1 in the front and +2 in the rear and the wheelbase is similar, but again, I've tried that on the 12 already 17/48 and it was too tight w/stock chain.
If 16/44 is about the longest you can go on stock wheelbase, then oubiously 17/44 and 18/44 works. But on the flipside, 15/44 or 16/43 just may be too much, get it?
A.
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dougmeyer
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posted November 05, 2007 09:27 AM
No point in lookiing at 19:xx One, the sprocket is too large and you have some clearance problems, and two, even on The Salt with 5 miles to run, I've never really stayed with an 18 for long.
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entropy
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posted November 05, 2007 09:47 AM
quote:
No point in lookiing at 19:xx One, the sprocket is too large and you have some clearance problems, and two, even on The Salt with 5 miles to run, I've never really stayed with an 18 for long.
you ran a 17????
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VincentHill
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posted November 05, 2007 10:18 AM
DM, so many people are using the 19 nowadays that Sprocket Specialist carries them in Stock! Yes, it is not a Perfect fit and you have to radius the Steel Piece by 1/8 inch all of the way around but not a lot of work and it saves 3 smaller gears needed to buy!
Keeps the chain from rubbing the Swing Arm a lot better also!
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shiphteey
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posted November 05, 2007 12:04 PM
Good points both ways. DM, you ran a 17 at B-ville! What gearing did you run and what MPH did it yield you?
I ran 18/44 @ Bonneville, stock rev limiter and I was about 100 RPMs if that from the rev limiter and had to keep getting off of the nitrous over and over at 208 on GPS, but since its a flying mile for timing I yielded 206.xx Gotta love them big tailwinds!!!!!!!!!
Had I had a 19 on there I woulda been facking FLYING!
A.
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Megabyte
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posted November 05, 2007 01:11 PM
I've heard guys say that a 16T robs HP because of the tighter radius, and that it rubs metal to metal. Just wondering what your take, and experience has been.
Thanks,
quote:
T If you want max wheelbase 16/44 is pretty nice. Its a 1/2 tooth more aggressive than 17/46 but you get tons more wheelbase so you can put the power down w/less wheelying.
A.
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shiphteey
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posted November 05, 2007 03:13 PM
I haven't noticed any shards of metal along the inside of my sprocket cover area or chain guard. No uneven wear shown anywhere, all is good.
It could in theory rob a little HP, but for the first few gears, its intial gain in thrust from the shorter gearing will MORE than offset the minutae HP loss, bet on that!
That being said I have taken the 12 to over 190 mph with a 16 tooth on the front.
A.
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twista
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posted November 06, 2007 05:11 AM
do you think 17/49 would be retarded? i mean its more than twice the low end im getting from stepping down to a 17 on front,, do you think it would cause mechanical issues,, hurt the bike etc.. or would it just be a handful from light to light, i know back in the day i had a Honda CBX and i went down 1 in front and up 2 in back,, and with that combo i was able to spank my buddys (rest in peace) CB1100F,, and it allowed the bike to wheel stand thru 4 gears,, 630 lbs. that was a spectacle.. if it wont hurt the bike then i think i will give it a try,, but right now i often find myself trying to upshift and there isnt another gear,, so this is gonna probably be retarded.. input?
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entropy
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posted November 06, 2007 05:18 AM
i use 17/49 for 1/4 mile, near top of 5th at 155mph or so.
to use on the street? why not.
your mileage will suffer and 1st gear will be a REAL handful, but go for it 
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KZScott
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posted November 06, 2007 08:23 AM
i have 17/51 for the 1/4
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dougmeyer
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posted November 06, 2007 11:14 AM
Hellooo....
17-38, 17-39, 17-40
I like changing th rears. Much easier, no need to remove bodywork if you're in a hurry.
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entropy
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posted November 06, 2007 01:13 PM
quote:
Hellooo....
17-38, 17-39, 17-40
I like changing th rears. Much easier, no need to remove bodywork if you're in a hurry.
whoa! what a concept!
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VincentHill
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posted November 06, 2007 02:05 PM
quote:
Hellooo....
17-38, 17-39, 17-40
All gears I do not have! It is also about money with me and with 17 , 18, 19, I do not need anything smaller than a 41 I have 7 rear sprocket including the Original. I can gear for anything from 160 to 230
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dougmeyer
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posted November 07, 2007 10:35 AM
RE: Wheel vs C/S
Also, your percentage of change can be much smaller when changing the wheel sprocket. When running naturally aspirated, without "excess" power, the smallest change can be just right . The correct decision may be lost in a change that is larger than required.
Interesting anecdotal nugget:
Did you guys know that the ZX-7RR Superbikes and Works WSB's could run with two or three slightly different primary ratios without changing the crankshaft? This was done by using different clutch baskets with the drive gear ground on a different pitch circle using the same number of teeth. Sometimes that very small change was just what the doctor (or Mr. Chandler or Russell) ordered.
Doug
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VincentHill
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posted November 07, 2007 02:09 PM
quote:
RE: Wheel vs C/S
Also, your percentage of change can be much smaller when changing the wheel sprocket. When running naturally aspirated, without "excess" power, the smallest change can be just right . The correct decision may be lost in a change that is larger than required.
Interesting anecdotal nugget:
Did you guys know that the ZX-7RR Superbikes and Works WSB's could run with two or three slightly different primary ratios without changing the crankshaft? This was done by using different clutch baskets with the drive gear ground on a different pitch circle using the same number of teeth. Sometimes that very small change was just what the doctor (or Mr. Chandler or Russell) ordered.
Doug
Since you were NA and % of change was totally a factor and you needed to be Exactly on the money I can understand what you are saying. My problems are not HP Related but HV (Hill Vincent) Related! Very hard to run 200+ without arming the NOS Even harder when you turn up the NOS and do not add the required amount of Fuel Harder yet when had a Cheap NOS Button that broke off during the run! So Small of things with such big Negative results! 
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twista
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posted November 17, 2007 11:26 AM
18/49 is 1 point higher than 17/46 (2:72) versus a 2:71,, is that 1 point noticeable,, i just aquired a lot of 4 front wheels 16-19 (front sprockets) think im gonna try the 49 on back and go back to a 18 up front,, will the stock chain work with that combo,, and anyone need a sprocket or two? thanx
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dougmeyer
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posted November 17, 2007 02:14 PM
There are a lot of duplications and very close combinations, but no I wouldn't say .01 is worth a change. .05 maybe, .1 for sure
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twista
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posted November 17, 2007 04:19 PM
ship,, what would a 17/45 do to wheel base? im thinking that since i find myself looking for another gear that isnt there on the highway,, i would shave 33% off where i am at right now
(17/46) going from a 2.71 to a 2.65 which is still an increase of 66% from a 2.56,,
will the stock chain work? and i would like the wheel to come up with just power,, you think that will remain? thanx bro and sorry to bother you,, but it appears that your knowlege in this area is REAL,, dont mean to be a pain in the ass...forget the last post,, its just too much low end,, dont get me wrong its fun,, but i need a little more on the highway!
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