How the sprocket can determine more speed or more accelerati

[donhuzayfa]

How does the sprocket determine speed or acceleration?

[oldgreg01]

Different diameter sprockets alter the gearing.

Think about how gears on a push bike work.

[Donnie Brasco]

Technically speaking:

Smaller front sprocket: faster acceleration, lower top speed.

Bigger front sprocket: slower acceleration, higher top speed.

Smaller rear sprocket: slower acceleration, higher top speed.

Bigger rear sprocket: faster acceleration, lower top speed.

[Colin the Bear]

Look at a mountain bike

[Decor58]

Basically what DB said, the front sprocket will turn at a set rpm however what determins the rpm of the rear sprocket is the ratio of the number of teeth at the front to the number of teeth at the back.

The more teeth at the rear the higher the top speed the lower the torque, the lower the teeth the more torque & the lower the top speed

[rennie]

Technically speaking:

Smaller front sprocket: faster acceleration, lower top speed.

Bigger front sprocket: slower acceleration, higher top speed. I disagree! other way round I think

Smaller rear sprocket: slower acceleration, higher top speed.

Bigger rear sprocket: faster acceleration, lower top speed.

[rennie]

Basically what DB said, the front sprocket will turn at a set rpm however what determins the rpm of the rear sprocket is the ratio of the number of teeth at the front to the number of teeth at the back.I agree

The more teeth at the rear the higher the top speed the lower the torque, the lower the teeth the more torque & the lower the top speed

I disagree! other way round I think

[rennie]

But!, then again, it is nearly 4 in the morning and I really CBA

[oldgreg01]

its the diameter of the sprockets that counts. Number of teeth is irrelevant

[Guest akey]

its the diameter of the sprockets that counts. Number of teeth is irrelevant

 

No of teeth and size of sproket are directly related as the Pitch must be the same between front sproket, rear sproket and chain. In fact its the no of teeth that really counts as this is how you determin the size of the sproket and therefore to final drive ratio.

So a number of examples:

Standard set up:

Front = 15 teeth

Rear = 30 teeth

Drive ratio = 1:2

Therefore if the front sprocket spins at 300 RPM the rear sprocket will spin at 150 RPM

Now lets up the rear sprocket

Front = 15t

Rear = 45t

Drive ratio = 1:3

therefore at the same 300 RPM at the front the rear will spin at 100 RPM

So if you increase the teeth at the rear, or reduce the teeth at the front you will increase acceleration but decrease top speed. You will also hold higher engine RPM for any given gear and speed than standard which can increase fuel consumption.

If you reduce teeth at the rear, or increase at the front you will increase top speed but decrease acceleration.

Other points:

Many modern bikes take their speedo reading from the front sproket so by changing the final drive ratio you will need a speedo healer as your speedo will read incorrectly.

You may need a longer / shorter chain

2 teeth down on the front, tends to equal approx 3 teeth up on the back (1 tooth down is approx 1.5 up on the rear).

Just have a look at the size of rear sprokets on stunt bikes - they are usually huge to give better wheelies

Personal experience:

I went up 2 teeth on the rear on my gixer 750 and it was a completley different bike, massive acceleration, I also know that a common mod on the 600 is down 1 on the front and up 2 on the rear (you can keep the standard chain).

[oldgreg01]

But as you say, that's only to do with having to keep a standard pitch for the chain.

If you manufactured a knew chain and sprocket set that was the same diameter but double the number of teeth then it would make no difference. Likewise snapping every other tooth of your standard sprocket.

So it's the diameter that counts.

[oldgreg01]

I'm interested in what you say about the big difference dropping size makes though.

Is it advisable to change the chain at the same time? I guess it depends on the chains condition? Mines only done 4000 miles.

[Guest akey]

But as you say, that's only to do with having to keep a standard pitch for the chain.

If you manufactured a knew chain and sprocket set that was the same diameter but double the number of teeth then it would make no difference. Likewise snapping every other tooth of your standard sprocket.

So it's the diameter that counts.

 

While technically the argument holds try to purchase a 9" diameter sprocket from a dealer!

All bike chains are supplied by number of teeth and pitch not diameter.

[Guest akey]

I'm interested in what you say about the big difference dropping size makes though.

Is it advisable to change the chain at the same time? I guess it depends on the chains condition? Mines only done 4000 miles.

 

If the chain has only done 4000 miles then I personally wouldnt change it, just fit a new sproket. It will depend on how much adjustment you have on your bike as to how much change you can get away with, but you can usually go up or down 1 or 2 teeth without needing to change the chain.

The gixer was loads better and accelerated like mad with +2 on the back, its the cheapest and easiest way to make a bike accelerate better.

[oldgreg01]

While technically the argument holds try to purchase a 9" diameter sprocket from a dealer!

All bike chains are supplied by number of teeth and pitch not diameter.

 

Fair point

Speedohealers are £85, plus the cost of a sprocket. That's not too bad, I'll have to look into it.

Cheers.

[donhuzayfa]

My bike gets too high revs too quickly, any suggestions as to increase or decrease teeth,??

[Guest akey]

Decrease rear sproket mate, but I would think carefully before doing it what bike is it and in what gear does it rev to quickly?

[donhuzayfa]

It's a kymco kr sport 125 cc, made by a partner of Honda, it is kind of a flaw in all reviews, it idles @ 3/4000 revvs, and starts over revving @ 9000, feels like youve put it in neutral whilst driving, the kind of loud over revv, maybe the sprocket can slow this process down??

[donhuzayfa]

Mostly revs in gear 1-2-3,

[Guest akey]

Mate that sounds more like your clutch needs adjusting as it is slipping at high revs!

Sent from my iPhone using Tapatalk

[Donnie Brasco]

But!, then again, it is nearly 4 in the morning and I really CBA

 

I'm not gonna argue Ian,I need that tent