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ricardokg15 10-27-2019 12:29 PM

Sprockets
 
I am running a 16 front and 43 rear on a 98 zx7r but now I want to goto a 15 front 42 rear since I do alot of highway and would like to get more top end out of the bike. Can anyone help me on wat is the best set up

mte78 10-27-2019 03:29 PM

I did 15 f/ 45r. I wanted better acceleration.

For the highway you should be just fine with the stock gearing.

ninjanut 10-28-2019 02:19 PM

If you are trying to increase top end, do not go down at the front. Dropping teeth off the back is what you want.
Not sure how much more top end you will get through gearing but I doubt much if any.

Swollzilla 10-28-2019 10:49 PM

I went from a 45r to a 43r as I was trying for more top end. While it gave me a few mph for such the small change what was awesome is how much better on the rpm’s. I gained almost a thousand rpms @ 100mph and I couldn’t even tell the loss in the low end. Just toy around with it till it’s right for you

92Ninjas 11-03-2019 09:33 AM

IDK about the best setup. I was running 18f/40r. I currently run 17f/42r

ninjanut 11-03-2019 07:11 PM

Pretty sure neither of those combos will help top end.

evan_calgary 11-06-2019 07:30 AM

Hey Steve, why would you advise against going down @ the front?

I thought it was generally established 1 tooth front roughly equal to 3 tooth rear and does not matter where it comes from provided you are not getting into crazy sizes. Just gear ratios right?

Necron9d9 11-07-2019 06:09 AM

So, to the OP when you say you "want more top end out of the bike" as you do a lot of highway, I'm not quite sure what you're after.

1. To gear your bike taller by dropping the final drive ratio (front and rear sprocket tooth combination count) to reduce engine rpm at a given speed in top gear for a higher terminal velocity at engine redline- so to make it "faster" as in a higher top speed.

2. To reduce the RPM at cruising speed to reduce vibration thru the bike, less sound and better mpg for more comfortable distance riding.

#1 looks good on paper but in reality this only works if you have the HP to push that gearing. OEM bikes will NOT pull redline in top gear stock because they are geared tall to begin with from the factory, plus lean carb/injection settings to meet emissions and Db testing. If the engine is turning at a lower RPM at the speeds where they run the tests on the dyno, it makes the bikes less loud and stinky and so they pass the standards. I don't know the mods on your bike but I'm thinking you're not regularly pulling 2x+ the speed limit on your usual commute nor are you trying to win a Red Hat from the SCTA for the 200mph club. If you are, then a ZX-10/14/H2 is the hardware upgrade you really need.


#2 Yes, the lower gear ratio will do all of that but at the cost of acceleration in the low and mid range where you do nearly ALL of your riding when not on the highway.

As MTE said above stock is fine, what with a 170ish "potential" if you can corral all the ponies. The ratio he's running is basically +5 teeth over stock and so gives a punchy low/mid with enough top to get your ass 3 hots and a cot for a good long time if you get caught. I personally like to gear for the wet dream of a perfect run up to the end of the fastest straight I see on a track, Fontucky or Willow Springs in CA usually for me. That means my usual terminal speed plus another 5-7 mph or so if i get lucky on an overrun. Number wise that means I don't need anything beyond 150ish, so then why not get there faster on the low and mid where most street bikes need to work.

As to what to do with each sprocket, definitely do not reduce the front vs the rear.

Yes, 1 tooth off of the front is equivalent to 3 added to the rear, but think of two circles, the first is 3" and the second is 8" with a chain running parallel between them at the top.

If you lop a tooth off the front and so reduce that diameter, the reduced height of the front sprocket makes it lower in height in relation to the rear. That causes the chain angle to increase due to the reduced height of the ft sprocket and so the chain runs harder against the guides and swingarm cap and grinds them down faster. They call this bad. Additionally, making the front sprocket smaller puts the chain to a more severe angle of turn as it is pulled around the front sprocket and so in theory the chain heats up and wears more because of it .

It's better to add teeth to the rear vs. dropping off the front unless you are going for a change big enough to need altering both front and rear ratios. If so then you also need to add a few extra links to the new chain to make up for the additional chain wheel diameter on the rear. If you don't then you will have to turn in the chain adjusters and shorten up the bike's wheelbase to compensate.

If you need to change ANY of the sprockets or the chain, you need to do all 3 at once or you'll wear out the new parts (and the old ones too) like you won't believe. More expensive than just buying a smaller front sprocket but best and really cheaper in the long run.

To make your ride better as it is for a commuter there's a few things you can do.

https://spidergrips.com/

If you want to play with your final ratio:

https://sprocketcalculator.com/

for the sprockets themselves I'd recommend:

https://www.supersproxusa.com/

ninjanut 11-07-2019 12:31 PM

Quote:

Originally Posted by evan_calgary (Post 4078016)
Hey Steve, why would you advise against going down @ the front?

I thought it was generally established 1 tooth front roughly equal to 3 tooth rear and does not matter where it comes from provided you are not getting into crazy sizes. Just gear ratios right?

If you drop the front you are lowering the top speed due to the engine revving higher. He will want to add to front and reduce the rear to get more top end (in theory). As mentioned, adding top speed without engine mods is not likely through simple gearing.
If you go -1 up front it is the same as +2 at the rear. Opposite of what he wants.

evan_calgary 11-08-2019 07:21 AM

Quote:

Originally Posted by ninjanut (Post 4078060)
If you drop the front you are lowering the top speed due to the engine revving higher. He will want to add to front and reduce the rear to get more top end (in theory). As mentioned, adding top speed without engine mods is not likely through simple gearing.
If you go -1 up front it is the same as +2 at the rear. Opposite of what he wants.

Misread! Thought you meant not making any changes at the front and only going for the rear. My bad. Also yes, larger @ front.


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