View Full Version : Front sprocket size, which one to go for?

05-31-2008, 02:51 PM
ok so heres a table which i found what the different final gearing does to the bikes top speed in top gear at 12,000rpm


(sorry, i couldn't copy and paste the table)

with a performace exhaust on my bike, i was wondering if the bike would be able to cope, with a front sprocket 15 and leave the rear sprocket at 47 teeth, and still have decent enough acceleration.

thanks for reading and i hope you can help me :)

thanks again


05-31-2008, 04:24 PM
just with a performance exhaust... no it wouldnt your acceleration would be really slow.

look below at all my mods and i only have a 14 tooth front and 47 rear just look what youve got on and go one size bigger if you want a higher top end.

06-01-2008, 05:41 AM
kk thanks for the info :peace:

06-01-2008, 06:05 AM
i run a 14 on our bikes and that ok with just standard de restricted
you wont know till you try

06-01-2008, 08:31 AM

I have 14/47 on my bike at the moment which is completely stock.

My acceleration is shocking haha, barely moves until she gets to around 7k rpm, then shes alreet but i would say go for a 13.


Aprilia af1
06-03-2008, 10:57 AM
I would have thought your aceleration would be ok with a 15 tooth front and sports exhaust on a 50cc. i used to have a 50cc on my af1 different engine to rs but i had a 15 tooth front and standard 40 tooth rear, everything standard and it pulled ok just had to slip the clutch more than usual and didnt't pull past 5th gear but then it was set up rubbish and still is, my bro has a 2003 derbi gpr50, and his has an 80cc and a performance exhaust with a 15 front but that has great accel so that probably would have almost as good aceleration as a 50.
But you can't compare a derbi engine to aprilia rs50(not new model) as the ratios are completely different once worked out.

Hope this helps.

Rs Redline!
06-03-2008, 12:01 PM
You realise that the table is for the Aprilia RS50 1999-2005, Not a Derbi GPR with Aprilia stickers. So the top speeds in the table are not going to be acurate for your bike.

the race leader
06-05-2008, 08:29 AM
11/47 Ftw!

06-05-2008, 09:02 AM
derinately dont go any higer than a 13 other wis u most likely wont even get the bike into sixth gear. my rs had an arrow exhaust, 12 tooth and it redlined in 6th doin 65mph. i got a 13 tooth and after that it struggle to get past 10k revs although it still pulled the same speed. i i had a longer stretch of road it would of gradually built up the revs but unfortunately i live on an island so there is nowhere long enough lol.