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Numerous figures have been mentioned but on
average Bike speedometers read around 5-10%
higher than actual speed. The SV's speedo is electronic, receiving a signal
from a sensor mounted on the Primary Sprocket cover which detects
the rpm of a magnetic sender mounted on the Primary Sprocket....cue
pictures courtesy of
Bjam - click here.
Also check out: How to avoid a
shattered sprocket cover The electronics of the system work on a presumed standard rolling
diameter of the rear tyre and stock gearing so any changes here may
further increase inaccuracy.
Most of us can live with the inaccuracy of a standard bike setup but use of a re-calibrator like Yellow
Box or Speedohealer becomes more of a necessity if for instance you
you change sprocket sizes.
See the following pages also: Gearing explained
Gear Ratios
Chart
Gearing ratio calculator
Sprocket/gearing changes
....and a couple of useful links:
How to Choose the Best Gearing for Your Bike, Your Riding Style
at any Track and Why it Makes Such a Difference
www.sportrider.com/tech/146_0008_gearing How do they connect to the bikes
system? - here's a couple of diagrams but there are detailed
instructions with the units. There are downloadable
instructions available on the Yellow Box and Speedohealer websites.
Speedohealer
now have 'plug-n-go' kits - no cutting of wiring required!
Speedohealer
Website
Yellow Box
Website
Don't
forget, see the following
pages also:
Gearing explained
Gear Ratios
Chart
Gearing ratio calculator
Sprocket/gearing changes
Slyboy 04/2004 -
For those of you who may remember I changed the gearing of my SV1S to 1
tooth less on the front and two up on the back (16/42)........(tell
me more)
Bogus Dave: Gearing changes have a lot to do with personal
preference. You (Slyboy) sound happy, so you've found the "right"
gearing for you. However, most riders will be pleased with changes
much closer to stock, for example one or two teeth on the rear
sprocket.
With race cans, lower gearing will result in more perceived exhaust
sound when you are cruising at Interstate speeds. Your one down and
two up should give you about 500 rpm more on the highway in top
gear. It doesn't sound like much, but it's quite noticeable with
open exhaust.
Another factor with lower gearing is that you will have more engine
braking in each gear. You may or may not like this. Also, you may
find that slow speed corner exits in first gear become rather
challenging because the throttle is so sensitive with drag race
gearing.
Your gas mileage will take a hit too. I just wanted to add my
comments before everyone rushes out to buy sprockets. I've changed
the gearing on almost every bike I've owned, so it's all for fun. Do
what makes you happy.
Bayouboy: I'm about to change my gear ratio as well. I'm not at
all concerned about the lowering of top speed. For me I think the
biggest negative effect will be the higher engine rpms during
highway droning. The 1 down / 2 up change that Slyboy did results in
an 11.6 % change. My tach indicates about 5000 rpm at 80 mph in 6th.
With this change the RPMs will increase to 5578. Anybody got a guess
as to what that will do to your gas mileage?
I'm going with 17/42 (stock front/+ 2 rear) sprockets for a 5% gear
ratio increase. So at 80 mph in 6th I'll be turning 5250 RPMs.
Hopefully the mileage won't suffer too much
UPDATE 06/2004:
CS..........rear...........gear ratio (# of revolutions of CS
sprocket per rear wheel revolution)
17...........40............ 2.353 (stock gearing)
17...........42.............2.471 5% change - quicker acceleration
lower top end
16...........41.............2.562 8.9 % change - ditto
The stock chain is size 530 with 108 links. I have 17/42 gearing and
a 108 link 520 chain (no difference in length between 520 and 530)
so its the same length as the stock chain. Here is a pic of where
the rear wheel ends up with this 17/42 gearing and a stock chain. If
you go 16/41 the wheel will probably not move very far from the
stock 17/40 position. Just wanted to let you know that 17/42 works
with stock chain just in case you really didn't want to make the
larger gearing change to 16/41.
Definitely easier to get the front wheel up in 1st from a standing
start. I like the 17/42 better than the stock gearing. No problems
controlling the bike -you will get used to how much throttle to use
to do what you want. Overall the bike just spins up a little faster
which I enjoy. Don't care at all about loss of 5 % of top speed as I
never go 140+ MPH anyway except on the long straight on track days
which is only a few times a year. The only real trade off is I'm
running 5% higher engine RPMs when touring. After using the
SpeedoHealer to correct stock speedo error and gearing change I'm
turning an indicated 5K RPMs at 70 MPH. With stock gearing I would
be turning about 4750 RPMs at 70 MPH. Not really a big deal, might
be lowering my gas mileage a little but thats not a big deal either.
The difference between 530 and 520 is in the dimensions of the pins
and plates. (See
DID spec page here) They are thicker in the 530 so its a
stronger chain. The length of the plates are the same so the length
of the chain is the same. Of course that also makes the 530 chain
heavier for the same length compared to 520. That is why some folks
switch to 520 and replace the steel rear sprocket with an aluminium
one. This change will drop a couple pounds of rotating mass so its
popular with the racers
jrl305: .......with the stock 17/40, the bike is already at 9%
off. I only dropped the front to a 16 and it went to 14.5%. All of
this was verified by using a GPS for the better part of a couple of
days at varying speeds. The YellowBox has corrected the speedo but
the tach is still 10% off, verified by a few different dyno runs. I
can run for hours at 80 mph with the 16 and the only thing that
seems to suffer is the gas mileage. Keep it under 70 and it's fine.
IMO the bike is geared too high from the get go and the 16t
countershaft sprocket is the answer.
Each to his own though.
Bogus Dave: I invariably gear my bikes down for more
acceleration: Bandit 15 to 14, ZX-12 18 to 16, and FZ-1 16 to 15T
front sprockets. Factory gearing is always too tall for me. I like
doing power wheelies and corner exit wheelies.
So, what I am going to say now will surprise you. When I first rode
Orlando Rick's SV, I thought the gearing was too tall. I even
suggested to him that he gear it down. Now that I have my own SV
(with Scorpion cans and vented airbox) I have changed that view. I
find the modded bike to be a bit too prone to wheelie (although very
controllable). I also feel that when leaned over in a first gear
corner, the throttle is too sensitive due to the excellent low rpm
torque of the V twin.
So, coincidently this afternoon I ordered a 39T rear sprocket. My
thinking is that I will still have easy power wheelies and that
first gear controllability will be improved on low speed curves and
first gear corner exits. My Pilot Road looks like it will be toast
at 3000 miles (yes, I am on the throttle a lot) and I will change
gearing at that time and report.
BTW... I too have had quite a few bikes over the years and have
tinkered with the gearing on most of them. Some raised and some
lowered.
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