SquidBusters Archive - gearing change

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gearing change
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Posted by: natrona848

I'm floating an idea and I want some opinions from those that know.

Currently my bike runs a 520 chain with a 15 tooth front sprocket and a 43 tooth rear sprocket.

I'm thinking of doing a conversion to a 14 tooth front and 40 tooth rear which would also run on a 520 chain.

I know I have to be aware of the chain having potential to hit the the swingarm and that I might loose top speed. That doesn't really matter to me though, I have no desire to go 160 on the street or on the track for that matter.

Basically what I'm looking for is quicker acceleration and having the bike to be a bit higher in the rpms at street speeds.

Thoughts??????

Posted by: Falcn

Simple Excel gearing calculators exist out there - they will allow you to figure out what the engine speed/road speed the new gearing will give you vs. the stock set-up. Essentially you will be changing the gearing by 6 teeth overall - which is a good bit!

This is the one I have used for my racebike. It takes into account the internal transmission ratios and sprocket ratios.

http://www.winsite.com/bin/Info?24000000036851

here is another one that would work:

http://www.winsite.com/bin/Info?24000000036851

Just google Motorcycle gear ratio calculator or something like that and you will find lots of pre-existing gear calculators.

Here is an online one if you don't want to use Excel.
http://www.dansmc.com/mc_software1.htm

Posted by: Oxi-Rider

Unfortunately, you will have higher rpms at all street speeds. You might be turning 7000 rpms or more at 70 mph in top gear!!

Posted by: natrona848

yeah i know and i don't have to to that extreme, could go less and still feel a difference.

Posted by: natrona848

here's what i have in the stock setup, it's all latin to me

DRIVETRAIN
Transmission
6-speed, return
Final drive
Sealed Chain
Primary reduction ratio
1.891 (87/46)
Gear ratios: 1st
2.923 (38/13)
2nd
2.055 (37/18)
3rd
1.666 (35/21)
4th
1.450 (29/20)
5th
1.272 (28/22)
6th
1.153 (30/26)
Final reduction ratio
2.866 (43/15)

Posted by: natrona848

i don't know, for me it seems if i could get it right and for the cost, it would have big pontenial for the $$$ and time envolved.

Posted by: Falcn

I would start with the 14 tooth sprocket - I won't be able to look at the spreadsheet for you until after my parents leave.

Posted by: JohnC

I went from a final drive of 3 (16/48) to 3.2 (15/50) on my R6, and it's pretty dramatic, a great mod for an inline four on the street. Be prepared to lose some gas mileage, but really gain some acceleration.

And I just looked at what you said - you were thinking about going from a 15/43 to a 14/40? You'll see no change, basically, if you do that. You need to go DOWN in the front and UP in the back to do what you want to do.

On that bike, since the rear sprocket is already so small, just dropping a tooth in the front is going to be pretty dramatic, taking your from 2.866 final drive to 3.07. I'd try that and see what you get.

Posted by: natrona848

okay, seems like going to a 14 in the front makes the most sense. gas mileage i'm not so worried about, just like loosing top speed, i do long days but i try my best to stay off the highway and i don't commute so all that stuff won't hurt me, should make it fun instead.

i posted the 14/40 numbers since RK has a kit set up for those sizes. like i said, for now this stuff is latin to me but i do understand the principle of it.

thanks everyone.

Posted by: garry

Why would you go down on the front AND down on the rear to get more acceleration? Those changes counter-act each other. Just drop a tooth up-front or go up a couple (or three) teeth on the rear, but not both unless you want a dramatic change. You're bike is new enough that I'd just slap a smaller front sprocket on there, re-adjust the chain and have at it. No need to swap the chain and rear sprocket out yet.

Posted by: 87hurricane

One thing to think about, if you go with a smaller sprocket up front, you chain may wear out faster, because its a tighter arc that its turning. I have gone up a tooth in the front on bikes before, and it is a significant, noticable difference.

Posted by: Falcn

Don't worry about chain links Eric, just buy a 120 link chain - I'll cut it and rivet it for you to the proper length no matter what sprockets you get.

Posted by: BlackB12

Quote:

Originally Posted by garry

Why would you go down on the front AND down on the rear to get more acceleration? Those changes counter-act each other. Just drop a tooth up-front or go up a couple (or three) teeth on the rear, but not both unless you want a dramatic change. You're bike is new enough that I'd just slap a smaller front sprocket on there, re-adjust the chain and have at it. No need to swap the chain and rear sprocket out yet.

I too don't see the point of changing both sprockets. Dropping the front one one tooth prolly won't require a new chain.

Mike

Posted by: natrona848

well, if i change the front, i'm going to put an aftermarket one on the rear too to shave some unsprung weight and no need to lie, looks play a part too. i know that wear could be accelerated but i'm not too worried about that either, i don't abuse my bike.

if i can find a deal on a gold chain, the stocker is gone!

Posted by: mangeldbug

Im still waiting on the 14T Ryan ordered for the Duc. Its backordered.

Eric, you might be able to find info on gold chains here.

Posted by: garry

The DID ZVM (great chain) is gold plated. Had one on my Sprint.

Posted by: natrona848

DID is on the short list.

kristen, no way am i cool enough to rock a grill like that!

Posted by: Falcn

You can also get an RK XW-Ring 520XSO in gold. My chain is an RK x-ring - been on there for years and years.

Posted by: Wingspan

I've regeared every bike I've owned, except for the VFR. I'd just drop a tooth in the front. If that's not enough then go up a tooth or two on the rear. I've never noticed any significant MPG drop after a gear change, though I'm sure it exists.

My personal opinion on the "smaller sprocket=more chain wear" point is this: The added wear is very small and much less a factor in chain life than the less that perfect level of adjustment and maintanance that the average chain experiences. As far as I'm concerned, it is a valid arguement in theory but means little in reality.

Posted by: Falcn

If I keep the VFR around long enough to need a new chain I plan on going down one in the front.

Posted by: Falcn

http://www.dropbears.com/u/utilities/gearing.htm

is this the one you downloaded? Version 12? This is what I actually ended up using for the racebike.

Posted by: HarleyJohn

It'll wheelie easier too.

Posted by: natrona848

no need to worry about that, i'm a sissy on the throttle

Posted by: Old Duffer

you should get 13/60. That's what I had on my gsxr