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davidimurray
10-18-2007, 08:01 AM
Does anyone happen to know what is the smallest size front sprocket you can get or fit (I can always make a custom) for the SXV550.

Just been doing some calcs and I am leaning towards using a 12T front sprocket.

Cheers

Dave

nubus
10-18-2007, 08:11 AM
Wouldn't you benefit more from dropping 1 tooth in the front and adding 3 in the rear?
It would help get the chain up off the slider and cause less chain stress up front.
BTW, what are you looking to top out at with that gearing??? 70-80 mph???

Gix
10-18-2007, 11:33 AM
Just been doing some calcs and I am leaning towards using a 12T front sprocket.

Cheers

Dave

Say goodbye to your swingarm then :rolleyes:

orangerider2
10-18-2007, 01:43 PM
That would put way too much stress on the gear box.:cigar:

davidimurray
10-18-2007, 02:34 PM
Keep forgetting to mention in my posts that this is for a Formula Student car.

Top speed will be somewhere around 70mph, with lots of low down grunt! Been looking at the gear ratios and we will be traction limited for most of first gear and probably for most and second gear - better get the traction control sorted!

Cheers

Dave

irie
10-18-2007, 02:59 PM
You'll waste too much time changing gear - better to use higher ratios and use less gears. It'll be faster.

pumpman
10-20-2007, 11:52 AM
That would put way too much stress on the gear box.:cigar:

Shorter gearing is easier on the gearbox, not harder. Must've had that cigar in backwards!:cheers:

orangerider2
10-20-2007, 12:13 PM
pumpman

Rethink what you just said.:cigar:

pumpman
10-20-2007, 12:23 PM
pumpman

Rethink what you just said.:cigar:

OK, I did...now educate me.:confused:

orangerider2
10-20-2007, 01:01 PM
The smaller the CS, the closer you are to a direct connection from the rear wheel to the gear box (main shaft) depending on engine sprocket size and clutch sprocket size you could have the equivalent of the motor sprocket hooked up to the rear wheel, any movement ( shock) from the rear wheel has a more dramatic impact on the motor with a smaller CS. If you have the power to pull it, a larger CS, will do no harm to the motor. It`s when you don`t have enough power, that you will encounter problems.

A smaller CS will also wear faster, and they tend to allow the chain to ride on the swingarm more.:cigar:

pumpman
10-20-2007, 01:42 PM
The smaller the CS, the closer you are to a direct connection from the rear wheel to the gear box (main shaft) depending on engine sprocket size and clutch sprocket size you could have the equivalent of the motor sprocket hooked up to the rear wheel, any movement ( shock) from the rear wheel has a more dramatic impact on the motor with a smaller CS. If you have the power to pull it, a larger CS, will do no harm to the motor. It`s when you don`t have enough power, that you will encounter problems.

A smaller CS will also wear faster, and they tend to allow the chain to ride on the swingarm more.:cigar:

I agree the small sprocket is a bad idea...but not because it will overload the transmission. You are forgetting the big sprocket on the wheel when you say it would be the equivalent of connecting the motor shaft directly to the wheel. The torque from the output shaft of the motor is MULTIPLIED at the wheel by the ratio of the sprockets, and rotating speed reduced accordingly. Conversely, any torque the wheel might exert on the transmission output shaft is DECREASED by the inverse of that ratio. As always, improper downshifting could be stressful for the transmission, but less so with the smaller sprocket. Acceleration is definitely easier on the transmission due to the reduced torque at the shaft for a given torque at the wheel. I respect your knowledge and experience, but your take on this seems wrong. Don't give up on me, I am still learning something new every day.:cheers:

davidimurray
10-21-2007, 06:03 AM
We will probably be running something like 12-34. This is because the smaller we can get the rear sprocket, the closer we can mount the diff to the engine, the further back we can move the weight distribution and shift more weight onto the tyres under acceleration.