Gearing

[Steve L]

Hi, I have a Sherco 290 that I want to gear up, I know that putting a smaller rear sprocket on will achieve this but I want to change the front as it is cheaper. I have been told different stories, can someone please clear this up for me. It currently has the standard 11 tooth sprocket, do I need to go with a 10 or a 12 tooth sprocket to achieve the higher gearing, thanks Steve.

[Trango]

The 12 tooth sprocket will raise the gearing. If you divide the number of front teeth by the number of back teeth it will tell you the gear ratio. The lower the ratio the higher the gearing.
Example:
46 rear divided by 12 = 3.83
46 rear divided by 11 = 4.18
46 rear divided by 10 = 4.60

[Steve L]

cheers thanks for that Trango, my mate was right I nearly bought a 10 so it would have been worse, I will now have to see if I can get a 12, thanks again Steve.

[jamie]

i think you will find the standard gearing on a sherco 290 is 10/42. if it currently has an 11 tooth front you will struggle to get a 12 tooth sprocket to fit as there will be very little clearance between the chain and the clutch slave cylinder. rear sprockets are cheaper than slave cylinders.

better off buying a 38T scorpa sprocket, 4T on back equivalent to a tooth on front.

sprocket same bolt pattern, but may need countersunk bolts instead of the standard cap screws.

talk to kal daley, he will have all you need.

[Steve L]

Hi Jamie yeah you are right they do have 10 / 42, I was after an 11 tooth not a 12 like I wrote. They are hard to get so I decided to get a 39 rear, I haven't had much of a ride since fitting it but it seems to of done the trick, cheers Steve.

[gordonmichaellee]

When changing ratios I think you have to consider a few other things first.
1
what do you hope to accomplish?( is it to go faster in top gear)
2
what terain do you mostly ride on( and is it always going to be that way)
3
have you considered ( if going faster in top gear is not the goal) using a higher gear in the gearbox for that particular section( I mean ride most of it in 2nd instead of first) at least that way you have a lower gear if you should need it?
4
bear in mind in first gear you will now be putting more strain on the clutch and gearbox