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Does one tooth make much difference?

Discussion in 'General Motorcycling Discussion' started by Senator17, Jun 19, 2014.

  1. I'm thinking of changing the gearing on my 2012 Kawasaki Z1000 by replacing the rear sprocket only. The Z comes with a 42 tooth rear, the Ninja 1000 (The touring version of this bike) comes with a 41. Has anyone had the experiece and can pass on if the noticed much difference?

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  2. would? have!
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  3. 42:41 is the difference. The math is simple. You can work it out from there.

    The only advantage for a smaller rear sprocket is in long distances without any accelerating. You use less fuel because engine is geared a bees dick longer, but the offset is using more fuel in accelerating. It also slightly tames the power. Imo, changing the rear sprocket by 1 won't even be enough to be noticeable. If you want to make an effective change go one up on the front.
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  4. Yes even one on the rear will be a noticeable difference.

    Did you say you wanted to make it taller or shorter gearing?

    The pitfall with gearing changes that people don't realize is the wheelbase change.. Yes I'm a picky fcuker but it really annoys me. I've seen people put extend swingarms on gay bling rockets and claim "it doesn't change the handling at all", that's horseshit. In motogp I've heard of them adjusting wheelbase by 0.4mm to get the bike right. I can definitely notice 3-4mm.

    Anyway, if you change the rear down you reduce your wheelbase and if you change up you increase it.

    Off the top of my head I tooth on the rear is about 7mm difference but one chain link (pair) is about 14mm.

    Longer will make the bike more stable at speed but be more prone to understeer on the exit of corners and shorter will make the bike turn in handle more responsively but more twitchy and loose on the rear when getting on the power.

    The factories to go great lengths to get this number right for the bike's intended use.

    I think going down 1 on the rear is pretty safe for touring purposes, but I wouldn't want to be shortening the wheel base below stock on a 1000cc bike.

    The more common complaint with gearing is speedos being out, normally people shorten their gearing do the speedo reads high that's not so bad but when you lengthen your gearing your speedo will read low so you'll need to be more aware of it going through speed traps etc.
  5. I agree with Lilley. I'd be very surprised if you would notice any difference day to day. I doubt you'd even see any difference in fuel consumption or performance outside margins of error resulting from half a dozen other factors. To put it into perspective, your back wheel and tyre are approximately 625 mm in diameter. 1/42 of that is ~15mm or, a little bit more than the difference between a new tyre and a bald one. Can you pick the gearing difference when you buy a new rear tyre? A race ace on a GP125 probably could. A road rider on something with more than a 200 rpm powerband, I doubt it.

    By all means go for it if you're changing your sprockets anyway but it's not worth springing for a new rear sprocket for the sake of one tooth.

    One tooth difference on the front is a different matter, making, roughly, three times the difference, which is noticeable, not so much in performance terms but more as a means of, for instance, finding an rpm sweet spot at your most common cruising speed, or avoiding being stuck between gears at a particular speed limit where you spend a lot of time on your commute.

    Manufacturers pick gearing for a variety of reasons, some of which are utterly irrelevant in the real world. For example, my BMW K100RS came with one less tooth on its crownwheel (more or less equivalent to a tooth on the rear sprocket) than the more sedate RT model because, for marketing reasons, the RS had to do 210 km/h and it wouldn't on RT gearing, coming up a smidge short. So it got a tooth less, and the torque of the Brick lump was able to wind the bike to the magic 210. I rode the bike on both original RS gearing and, later, RT gearing and, even keeping accurate fuel consumption records, could detect no difference on the road. I certainly couldn't feel any difference in acceleration because the flat torque curve didn't care much about gearing. For any rider who didn't take their bike to 210 km/h, any practical difference was non-existent.
  6. So many facts yet the key one is wrong :p

    "Anyway, if you change the rear down you reduce your wheelbase and if you change up you increase it."

    Actually, if you change the rear sprocket down i.e smaller you will increase the wheelbase, if you go up or bigger it will be a decrease in wheelbase.

    Also, given the overread of bikes, going down 1 tooth on the rear will probably actually get the speedo closer to truly accurate...
  7. On ducati's, it is common to go down one tooth on the front sprocket so the bike is more manageable at posted speeds.
    On my 1100 monster, it meant that 40 kmh speed zones could be managed in second gear instead of revving the tits off it in 1st gear or stalling it in 2nd with the std gearing. Having top end speed reduced by 5-10 kmh means nothing over 200 kmh anyway on the road.
  8. Fennel, good pick up on the wheelbase changes with bigger and smaller sprockets.
    Senator17,... Regarding one tooth change on the rear either way, why would you bother, you're better going up or down on the primary sprocket, cheaper, easier to change, no change in wheelbase (unless you measure with a micrometer) and at least you will feel the difference. By the tacho it would change maybe around 300 to 400 revs either way in top gear.

    Cheers Alex
  9. I don't know why you would ever want to dull down the performance of a sports bike further with taller gearing, given they're geared way too tall from the factory anyway!

    I recently went -1 front and +2 at the rear on my blade (should be standard mod on all bikes remotely sporty), its like a new bike, you can actually use the power now, and the top speed is probably reduced from something it would never actually had the legs to hit, to around 270 odd.
  10. Sorry brain fart!
  11. Are the front sprockets the same between the two models?

    Depending upon the ratio of front/rear teeth, it may make a difference... But I suspect the effect will be subtle at best.

    Assuming a 17T front you'll go from:
    2.470:1 f/r ratio.

    For reference, my TRX stock is:
    +2 on the rear (noticable) gives:
    2.411 :1
    & +6 (current gearing, very noticable) gives:

    We're talking second decimal point change in ratios... Don't know what that would be in %.
  12. #15 Senator17, Jun 20, 2014
    Last edited by a moderator: Jun 20, 2014
    Thanks I agree with the speedo commnet. The gearing change is approx. 2.4%, that is I would actually be traveling 2.4% faster at any indicated speed. As my speedo currenlty reads about 3% high, I would actually be traveling a beez dick below the indicated speed. So that adds one more reason to change.

    Wow, thanks everyone for all that great information. I worked out that the change would drop my revs at freeway speeds of 110kps by about 120 rpm. Not really noticable. Marginal at best to make any difference to fuel economy or range. I'm guessing with my fairly average abilities I won't really notice much difference is performance. The top speed of my bike would go up about 6 kph from 256 to 262, which I doublt it will ever see. Acceletarion would be down slightly, but I doubt I'd notice something like 2.4%, it would still feel farken quick. The speed the bike is traveling would be closer to the indicated speed on the speedo but still below indicated speed so all legal there.

    Somehow I don't think I'd notice the difference in handling by lenghthening the wheelbase from the difference of one tooth on the rear sprocket.

    But if lengthening the wheel base creates more understeer, what can be done to conter that effect?
  13. Go back to standard rear sprocket? :whistle::whistle::whistle:
  14. What else can be done to courter the effect of added understeer?
  15. Drop the yokes over the forks to steepen head angle and shorten trail (but you lose some ground clearance). Put rear suspension on max preload to raise the ride height, steepen head angle and shorten trail. Tip in earlier and steer harder.
  16. plenty of things can decrease understeer. generally entry issues relate to front end of the bike, exit is the rear. In saying that basic front end settings and ride heights def affect exit, just not as much e.g. increasing E2E length of the shock, incr preload, incr rear spr rate, decrease rebound, incr compression, finding the equiv gear ratio in a combo that lets you preserve your desired geo, or running a larger diameter rear tyre or combo of tyre where the fr/rr diameter diff is net positive to the rear.
  17. Hosack front end.