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Coxyzxr
Brolly Dolly



Joined: 22 May 2008
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PostPosted: 11:40 - 26 May 2009    Post subject: Simple sprocket question. Reply with quote

What's going to give better acceleration.

1 tooth down on the front?

or

1 tooth up on the rear?

I know both. But individually?

Kind regards
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Wozza
Brolly Dolly



Joined: 17 May 2008
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PostPosted: 11:43 - 26 May 2009    Post subject: Reply with quote

1 down on the front, but it won't make a massive difference.
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Mr Hammers
World Chat Champion



Joined: 10 Jul 2008
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PostPosted: 11:45 - 26 May 2009    Post subject: Reply with quote

A change of 1 tooth on the front equates to 3 or 4 on the rear, I think.
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Coxyzxr
Brolly Dolly



Joined: 22 May 2008
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PostPosted: 11:46 - 26 May 2009    Post subject: Reply with quote

Mr Hammers wrote:
A change of 1 tooth on the front equates to 3 or 4 on the rear, I think.


If that's the case I'd guess contrary to first reply by Wozza it would make quite a difference?

Many thanks.
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 11:49 - 26 May 2009    Post subject: Reply with quote

Hi

Basically 1 tooth on the front will have more effect than 1 on the back. Looking at ZXR750L gearing (16:44) 1 tooth down on the front would be the same as 2.75 teeth up on the back.

How much it will help acceleration will depend on what is the limiting factor. If traction or wheelies are the limiting factor in 1st then no great help, and in any other gear you could probably just change down a gear to gain the same advantage.

All the best

Keith
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Coxyzxr
Brolly Dolly



Joined: 22 May 2008
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PostPosted: 11:55 - 26 May 2009    Post subject: Reply with quote

Kickstart wrote:
Hi

Basically 1 tooth on the front will have more effect than 1 on the back. Looking at ZXR750L gearing (16:44) 1 tooth down on the front would be the same as 2.75 teeth up on the back.

How much it will help acceleration will depend on what is the limiting factor. If traction or wheelies are the limiting factor in 1st then no great help, and in any other gear you could probably just change down a gear to gain the same advantage.

All the best

Keith


Thanks as always Kickstart.

To be honest just wanting some more accerelation in the shorter gears.

Also the bike never reaches rev out point in top gear/prone on a long... airstrip either. Just always seems about 800rpm away. Thought it'd help with that also. But mainly for more accerelation.

Regards
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Wozza
Brolly Dolly



Joined: 17 May 2008
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PostPosted: 12:04 - 26 May 2009    Post subject: Reply with quote

Coxyzxr wrote:
Mr Hammers wrote:
A change of 1 tooth on the front equates to 3 or 4 on the rear, I think.


If that's the case I'd guess contrary to first reply by Wozza it would make quite a difference?

Many thanks.


Changing down 1 tooth on the front sprocket alone will make a difference, just not a massive difference. I recently changed 1 down on the front and 2 up on the rear, and the difference wasn't that big. For example in sixth gear, engine revs are about 1k higher than before for a given road speed.

Having said that it depends on bike and gearing and so on... Keith has arrived so no need for me to go on Smile
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 12:05 - 26 May 2009    Post subject: Reply with quote

Hi

Red line doesn't really indicate where the power / torque ends. It is actually torque that is the important bit (power just means that you can gear it lower for the torque to be geared down less).

Purely by chance in the bath this morning I was reading an old copy of PB with an article on the ZXR750J and ZXR750K. The J made its peak and rapidly fell away after about 9000 rpm.

While you might land up with better acceleration in 2nd gear at Xmph, this is no great gain if you would otherwise still be in 1st with even better acceleration.

Do you have a dyno graph and gearing for your bike? If so can you post them up?

All the best

Keith
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Coxyzxr
Brolly Dolly



Joined: 22 May 2008
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PostPosted: 12:16 - 26 May 2009    Post subject: Reply with quote

Kickstart wrote:
Hi

Red line doesn't really indicate where the power / torque ends. It is actually torque that is the important bit (power just means that you can gear it lower for the torque to be geared down less).

Purely by chance in the bath this morning I was reading an old copy of PB with an article on the ZXR750J and ZXR750K. The J made its peak and rapidly fell away after about 9000 rpm.

While you might land up with better acceleration in 2nd gear at Xmph, this is no great gain if you would otherwise still be in 1st with even better acceleration.

Do you have a dyno graph and gearing for your bike? If so can you post them up?

All the best

Keith


Thanks again guys/Keith.

I don't have a performance graph.
I read that article too, the power transformer one where they try making the J more like a K?

If I'm honest here: with my zxr you can pretty much crank the throttle as much as you want and know the nose won't lift. (Front end heavy porkers) Sometimes I feel it'd be nice if it did though you know? Maybe first gear power wheelies? even just a bit?

Many thanks.
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Kickstart
The Oracle



Joined: 04 Feb 2002
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PostPosted: 15:12 - 26 May 2009    Post subject: Reply with quote

Hi

Found a couple of graphs for the ZXR750J. One J1 and one J2, but quite different.

Stuck the details up here. Red line is the J1, blue line the J2 and the green line is the J2 running one tooth lower on the front (15:45 instead of 16:45).

All the best

Keith
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Coxyzxr
Brolly Dolly



Joined: 22 May 2008
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PostPosted: 15:17 - 26 May 2009    Post subject: Reply with quote

Kickstart wrote:
Hi

Found a couple of graphs for the ZXR750J. One J1 and one J2, but quite different.

Stuck the details up here. Red line is the J1, blue line the J2 and the green line is the J2 running one tooth lower on the front (15:45 instead of 16:45).

All the best

Keith


Thanks Keith.

In laymans terms what's that telling me? Shifting the torque down the range and moving it from the top?

Strange the stock J2 is different to J1 as essentially they were the same machine with an attempted fix on the rear shock, nothing more afaik.
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Kickstart
The Oracle



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PostPosted: 15:23 - 26 May 2009    Post subject: Reply with quote

Hi

Suspect that one might have been a better prepared press machine Wink . Or just the effects of different dynos.

The graph is thrust at the back wheel vertically against speed horizontally, for each gear. The thrust is what is accelerating you.

All the best

Keith
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Coxyzxr
Brolly Dolly



Joined: 22 May 2008
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PostPosted: 15:26 - 26 May 2009    Post subject: Reply with quote

Kickstart wrote:
Hi

Suspect that one might have been a better prepared press machine Wink . Or just the effects of different dynos.

The graph is thrust at the back wheel vertically against speed horizontally, for each gear. The thrust is what is accelerating you.

All the best

Keith


Awesome, many thanks.
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