Down gearing

mwad · Post by **mwad** » Wed Sep 10, 2008 10:23 pm

Hi

I have been considering down gearing my VTR as it is geared to the moon lol. I have never done this to a bike before and I'm not very hands - on when it comes to mechanics so would prob get a friend to help.

What would be the best way to do this - a smaller front sprocket ?

Where would be the best place to buy ?

Would the acceleration improvement be much better or just a little better ? Is it worth the hassle ?

Finally, I believe I would need to sort speedo reading incorrectly ?

Thankyou in advance

Mark

Kitch · Post by **Kitch** » Thu Sep 11, 2008 10:15 am

Renthal make a "race kit" for it with front and rear sprcokets and a chain.

Very good value and goes from stock 16-41 to 15-42

(Tsubaki chain included - Â£114)

http://www.intobikes.co.uk/products?det ... 53&search=

mwad · Post by **mwad** » Thu Sep 11, 2008 3:30 pm

Thanks for the replies gents. Is it a mod that begs to be done ? Does the bike accelarate MUCH harder ?

Max · Post by **Max** » Thu Sep 11, 2008 7:29 pm

I'm using 15-44 and it does accelerate quicker

Pete.L · Post by **Pete.L** » Thu Sep 11, 2008 8:28 pm

mwad wrote:Thanks for the replies gents. Is it a mod that begs to be done ? Does the bike accelarate MUCH harder ?

Best mod out there in my opinion. You can spend a fortune on the engine and not get a lot more omph and a rear spocket will only cost you 20 odd quid.
Or you could do both!

Pete.l

Stratman · Post by **Stratman** » Thu Sep 11, 2008 11:05 pm

I fitted a 2 tooth bigger rear sprocket. Can only agree with others - best mod I have done. Much more tractable and smooth

Kitch · Post by **Kitch** » Fri Sep 12, 2008 6:33 am

Its almost as if Honda tacitly expect you to do this modification.

They went a put a very long 6th gear on it so that when you down gear the ratios you don't lose so much off cruising ability for distance riding and it can pull enough revs to run at 30mph in 6th.

Going to a 15 front or 44 rear does make a pretty big difference. Doing both make power wheelies in 2nd commonplace.

mwad · Post by **mwad** » Fri Sep 12, 2008 3:36 pm

Kitch wrote:Its almost as if Honda tacitly expect you to do this modification.

They went a put a very long 6th gear on it so that when you down gear the ratios you don't lose so much off cruising ability for distance riding and it can pull enough revs to run at 30mph in 6th.

Going to a 15 front or 44 rear does make a pretty big difference. Doing both make power wheelies in 2nd commonplace.

I must admit, losing the cruising ability was a concern, that was going to be my next question

LotusSevenMan · Post by **LotusSevenMan** » Sat Sep 13, 2008 8:46 am

Great modification.

I've had both 'mods' (as in just the front sprocket down a tooth and just the rear up two teeth) but at different times.
I prefer the latter as easier on the chain than turning through the tighter front sprocket radius with a chain that doesn't appear to be worn out when adjusting the axle in the swing arm and the feeling/rideability was just better.
Don't forget though that the FS's innacurate speedo becomes more so.
That's why I (and others) have fitted a 'Speedo Healer' unit to get a proper reading from the thing.
As to Touring, I have found it very good having done about 850 miles recently from Kent to the West Country and back etc.
Got a true 43mpg average with most cruising at just slightly higher than one should be speeds etc !!!!!!!!!

Squiffythewombat · Post by **Squiffythewombat** » Sat Sep 13, 2008 10:33 am

+1 to everything said here!

one down front
two up back

front wheel never stays down...hours of fun!

tony.mon · Post by **tony.mon** » Sat Sep 13, 2008 11:39 pm

Dropped one tooth front this year as I go to the Bulldog Bash and run the poor old thing up the drag strip. Last year I kept hitting the rev limiter in fourth just before the lights, either I lost time changing just before the lights or I was hittng the limiter for the last 20 yards.

SO I fitted a 15 tooth front, and it worked fine.

But I dunnarf notice the revs being higher when i'm cruising on the motorway.
Used to sit at 95 or so (indicated) in top around 5000, but now is revs to 5500, and feels much worse. Probabaly in a vibration range for the handlebars, end weights or something.

Either way, in order to try to get a smidgeon better fuel consumption when I go to Valencia for the MotoGP next month I'm putting it back to standard.

And at least I'll have a speedo that is within 10 or 20% of right.

mwad · Post by **mwad** » Tue Sep 16, 2008 3:33 pm

[quote="

And at least I'll have a speedo that is within 10 or 20% of right.[/quote]

The speedo is THAT inaccurate ?

Kitch · Post by **Kitch** » Tue Sep 16, 2008 10:55 pm

Since I have a speedo healer I calculated mine had factory error of 6% this was compounded to around 12% after sprocket mod.

Great little bit of kit - get accurate speed - handy for seeing how fast you're really going (with top speed recall button) for camera limits etc too.

Reduces your overall mileage by the same percentage (thats over 1000 miles a year on mine)

Makes fuel stop planning and sat nav more accurate too with true distances displayed.

tony.mon · Post by **tony.mon** » Tue Oct 07, 2008 11:33 pm

Speedos can over and under read by 10%, typically the mnfrs set them to over read so that you feel that you're going faster.
it's safer that way, if you drift over the speed limit according to your speedo you're still actually under it, in all likelihood.

That's why when you're following the old bill on the motorway and you think they're going to nick the odd person that drifts by a bit faster than they're going, they don't bother.

Also consider the difference in tyre rolling radius as it wears- the smaller the tyre, the more times it goes round in a given distance, so a new tyre will make your bike read slower.

Without a speedo healer, though, you just recalcualte what speed it's reading as you go through the common limits- for mine, that's reading 36 to give a realistic 30, 48 to give 40, and 82 is safe at 70 limits.