sprockets

[richy rich]

hi, on my gilera rcr 50 i have got a 13t front sprocket and a 53t rear, ive just bought a 16t front and 52t rear for it, will this lose acceleration and gain a bit of top end speed?...
thanx
rich

[Lateshift]

yes it will, although in the case of a 50cc bike you will likely only gain something like 10mph at most :)

[richy rich]

well i get 50-55 anyway with the old ones so thats a result on a 50 lol although im not ssure how it does that because the restrictors have only been taken out the exhaust...im not complainin...cheers for that!

[richy rich]

just one more thing....will this also affect the bike up hills? because its pretty good up hills at the moment?!

[Lateshift]

as i said "10mph at most" ;)

in all fairness you may find that the bike revs out at about the same seeing as we are only talking about a 50cc engine here.

as a comparison when i dropped 1 tooth off the front of my bike, it lost 5mph top end, that means realistically its dropped to 170 instead of 175.

1 tooth on the front roughly equates to 3 teeth on the rear

-1 = +3
+1 =-3

so in adding 1 to the front and dropping 1 on the rear, you have effectively changed your gearing by 4 teeth.

if i knew the gear ratios etc i would probably be able to work out how it would affect acceleration and top end but as a rough guide and taken the speedo error and revs into account it will probably be more like an extra 5mph anyway ;)

[richy rich]

iv added 3 to the front so is that like adding 9 on the back?? lol but dropped 1 on the rear so 8?

[Lateshift]

Yes pretty much, although with the 3 that you have added and the 1 on the rear that would make 10 teeth in total ;)

Its a pretty radical change in gearing, so bear in mind that your speedo is likely to be well out of whack now ;)

[richy rich]

lol...well funny you should say that its really badly out already, i had to get my dad to go in the car n see wat speeds i was doing....30mph is right but when it says 35mph im actually doing 40 and when it says 40mph im doing 50....i havent actually found out what 45 or 50 is on the speedo as it only goes to them down hill lol...and as for the speedo being out im not sure that will happen on mine because its a mechanical speedo that goes straight from the front wheel...am i right?

[Lateshift]

and then bear in mind that a car speedo is out too by around 10% at lower speeds too ;)

However if you have a speedo that is driven from the front wheel the gearing change shouldnt be a problem, it only becomes a problem if you change to a different size tyre because you are changing the circumference of the wheel and in turn changing the ratio of the speedo then ;)

My advice would be that once you have the gearing changed, get your Dad to drive along at 30/40/50 and make a note on each run what speed your bike was indicating and then put a sticker on the clock so you know where each enforceable speed limit is ;)

But at the same time, if he is reading 40 and you are reading 50, the last thing you want to be doing is 10mph under the limit each time the speed designation changes, it will just make you a target for anything behind with a horn :D

[richy rich]

dammit i cant win with this bike lol... we'll just have to get a speed cameras opinion....or not lol... will just have to see what happens...cheers

[Tark]

going up 3 teeth on the front sprocket will make a MASSIVE difference on a 50! Your top speed would be much better but its likely the power of a 50 will not get you there in top gear. I wouldn't advise it to be honest.

[Tark]

Yes pretty much, although with the 3 that you have added and the 1 on the rear that would make 10 teeth in total ;)

Its a pretty radical change in gearing, so bear in mind that your speedo is likely to be well out of whack now ;)

If the speedo is taken from the front wheel speed then changing the gearing will not make any difference to the Speedo reading.

Its only if you have an Electronic speedo measuring the final drive that the gearing changes it.

(ps I have no Idea what the bike in questions speedo is like)

[richy rich]

i have only got 5 gears, not 6...well iv bought them now so when they get here i will try them if its crap i will change the front one... i needed new s*****ets apparently, i was just going to buy a new chain but i was told it would just get recked 'cus of the state of my sprockets..if its not good ill just buy the 13 again..

[Tark]

I take it you have got a longer chain than standard then?

[richy rich]

my chain has stretched to the max!!!!!!!....ive gone for the renthal r1 gold works motocross racing chain...

[Tark]

With having a bigger front sprocket and smaller rear sprocket the overall length of the chain might not be that much different thinking about it. i guess your adjusters will give you enough play..

Let us know how it feels....

My Guess is very very slow!

My TS50 had an 80 kit on it, performance exhaust and racing carb and I changed the front sprocket up 1 tooth cos it was getting to max speed very very easy and reving out. Just 1 tooth was enough to make a big difference and I noticed it when going through the gears. Took much longer between each gear change for the revs to buikd up.

[richy rich]

well its probly going to be B***** then lol..ohwell worth a try i suppose...mine gets to top speed really quickly at the moment and revs out... i hav gone down 1 tooth on the back now wich wont make any diffrence will it??

[Tark]

One tooth down on the back alone will make a small difference. Like said before 1 up on the front is like 3 down on the back.

It will be ok going down hills with the wind behind ya!

[richy rich]

thats all i need:grin2 lol...ill see how it is...if its crap ill buy the 14 i think ...do you think it will still make much difference having a 14 tooth if iv gone down one on the back??

[Tark]

One down on the back and one up on the front should be ok.

[richy rich]

ool....mite have to get the 14 then if the 16 is too much for the bike

[Lateshift]

If the speedo is taken from the front wheel speed then changing the gearing will not make any difference to the Speedo reading.

Its only if you have an Electronic speedo measuring the final drive that the gearing changes it.

(ps I have no Idea what the bike in questions speedo is like)


i take it you did read the next post i made after he responded to that? ;)

[Tark]

Just read it now. LOL