Sprokets

92CBRZiggy · 09-07-2004, 01:37 PM

I am going to replace my chain soon and was considering going down a tooth or two in the rear while I had the chain off. I was just wondering what affect this would have on the performance of the bike.

~Ziggy

hybrid · 09-07-2004, 02:31 PM

The basics of gearing, down in the front is the same as up in the back. for every tooth down in front the effect is similiar to up three in the back. Now, down in front or up in back is less top mile per hour but quicker acceleration. Up in the front or down in the back is more top mile per hour but less acceleration. I doubt youd feel a huge difference in 2 teeth down in the back. If you want absolute top speed, The bike has to be able to pull to the rev limiter in top gear. If it does easily then gear with a lower ratio. If you want more acceleration go with a higher ratio.

That being said, a larger rear sprocket transmits more wheel torque than a smaller front. The gearing would be the same but you would feel more torque with the bigger back sprocket. So for the cheapies out there.... Just doing the front is the wrong way to go. There are plenty of physics involved but I can explaine it to anyone who wants to know.

92CBRZiggy · 09-07-2004, 03:12 PM

Now my question is how much of a difference would it be going up in the rear one, two, or three teeth.(had it backwards before). I am looking to gain some acceleration, but still be able to ride it fine on the road.

Oni · 09-07-2004, 04:51 PM

Go up a tooth a two. Two is probably ideal for what you're looking to do. Faster off the line while still rideable for everyday commuting. You'll loose a little top end (guessing 15mph or so?, not that familiar with your bike), but that fast would be far from legal on the street/interstate anyway. You might want to post in the Honda section to get an answer from someone that's done the mod to your bike.

hybrid · 09-07-2004, 04:55 PM

Thats a question of math. I would need to know a lot of numbers to give you the answer but say an 01 R6 indicated 165 and you went down 1 in the front and up two in the back it now indicated 151 at the rev limiter in top gear. the difference is now it pulls roll on wheelies ( with a little throttle f@cking) in second gear at 40-45 mph in a sit down. Thats at 5000 feet which is an automatic 20% horsepower loss from sea-level. The math need would be all the gears from the primary to the final drive and the circumferance of the back wheel. Trust me its a lot of math to get the supposed number and that is without the adding of wind resistance and friction loss. I would just do 1 down in the front and 2 up in the back with a 520 conversion depending on the bike ( I dont know what your bike is) I might have that stuff laying around (new) anyways it should wake most bikes right up. If your a stunter and dont care if your bike goes over a 100 supersize it in the back and go 1 down in front and up 6-8 in the back. Its how they do the super slow wheelies, with control.

LuvDog · 09-07-2004, 08:00 PM

Quote:

Originally Posted by hybrid

That being said, a larger rear sprocket transmits more wheel torque than a smaller front. The gearing would be the same but you would feel more torque with the bigger back sprocket. So for the cheapies out there.... Just doing the front is the wrong way to go. There are plenty of physics involved but I can explaine it to anyone who wants to know.

Can you help explain this to me a little more?

Why is just going down 1 tooth in the front the wrong way to go?

Is it bad for the bike? Does it result in more wear and tear?

falco · 09-07-2004, 10:09 PM

Turning hard around an even smaller sprocket is a little harder on the chain, not a real big deal though, but I want an explanation to hybrid's post same gear ratio why would the rear be more torque?

mrzedexsixargh · 09-07-2004, 10:51 PM

It's all about leverage.

BTW, +2 in the rear made a world of difference for my ZX6R.

92CBRZiggy · 09-08-2004, 11:25 AM

Thanks for the input everyone. I will try asking around in the Honda section to see if someone can give me specific numbers from experience. And Hybrid, I have a 1992 CBR 600f2.

~Ziggy

92CBRZiggy · 09-08-2004, 12:42 PM

Another question about this subject. I will need to get a different chain size if I go up two teeth in the rear, right? Probably shoudl have thought of this sooner, since I already have my chain and am just waiting for a weekend without work to put it on.

hybrid · 09-08-2004, 01:19 PM

If you go one down in front and up 2 in the rear the stock chain size is still usable.

On the question of why use bigger, it is simple physics. Chain pitch around the front sprocket is a tranny killer ( out put shaft bearing anyways) it also takes more power to squeeze the links around a small diameter. On the rear it is the same as a torque wrench. If you have a torque wrench that measures 1 foot from the socket head to the grip, the amount of force measured is actual, so to get 60 ft lbs of torque you actually have to exert it. If the wrench is 2 feet it would exert the same torque with only physically 30 lbs of exertion. Why? because you doubled the distance. Kind of like holding a broom at the end of the handle and using your wrist to move it, its way harder to move it from there than to grip the handle next to the head. Leverage, it king. So the larger sprocket will transmitt more torque with less effort and because it is larger the flywheel effect is greater.

hybrid · 09-08-2004, 01:21 PM

If anyone needs more explanations let me know I can give you the math formulas for gearing and wheel torque as well