New Sprockets - 16/40?
#1
New Sprockets - 16/40?
Hi all... I had a new chain and sprockets fitted today and rode back home with them (250km). They didn't have stock size sprockets and according to my invoice they fitted 16 tooth front and 40 tooth rear. I'm pretty sure I would have had stock on there previously (17/42?). On the highway, sitting on 110km/hr it would be sitting on around 4050-4100rpm, on the way home tonight it seems to sit on slightly higher rpms at 110kph. Funny thing was that cars were passing my and kinda felt I was going a bit slower than normal.
So out of this I have 2 questions... firstly, what would the effect be of going to 16/40 size sprockets compared to stock? would is increase or decrease RPM's at highway speeds? I've tried reading up about the sizing but it confuses me!
Secondly, how do our speedo's work? Will the speedo auto adjust to different sprocket sizes? My old bike had the speed running off of the front wheel, therefore it was independant of RPM's or final drive gearing. I just have a feeling that if one was to gear the sprockets to have less RPMs at highway speeds, that the speedo would be reading a lower speed than what you're actually doing.. and vice-versa, if one was to gear it so it has more pot and higher RPM's at highway speedo would do the opposite with the speedo vs actual speed. Am I onto something here or does the speedo display the correct speed no matter what sprocket ratio/gearing is used?
Thanks for any help on this one!
Cheers. Carl.
So out of this I have 2 questions... firstly, what would the effect be of going to 16/40 size sprockets compared to stock? would is increase or decrease RPM's at highway speeds? I've tried reading up about the sizing but it confuses me!
Secondly, how do our speedo's work? Will the speedo auto adjust to different sprocket sizes? My old bike had the speed running off of the front wheel, therefore it was independant of RPM's or final drive gearing. I just have a feeling that if one was to gear the sprockets to have less RPMs at highway speeds, that the speedo would be reading a lower speed than what you're actually doing.. and vice-versa, if one was to gear it so it has more pot and higher RPM's at highway speedo would do the opposite with the speedo vs actual speed. Am I onto something here or does the speedo display the correct speed no matter what sprocket ratio/gearing is used?
Thanks for any help on this one!
Cheers. Carl.
#2
RE: New Sprockets - 16/40?
hi
new to cbr1000's. but just changed my sprokects I run 17 and 44. give a bit more acceleration.
check out his link
http://www.jtsprockets.com/52+M54a708de802.0.html
the ratio's you have are only slightly lower than you had before. are you sure you had 17, 42 before you put it in the shop.
the speedo won't adjust. When I run 17, 44 it makes you speedo read let say 30 mph (about 50 kph) but you are actually goin about 27 mph, great if you go through the zillions of speed camera's in the UK.
hope the link helps
blue2
new to cbr1000's. but just changed my sprokects I run 17 and 44. give a bit more acceleration.
check out his link
http://www.jtsprockets.com/52+M54a708de802.0.html
the ratio's you have are only slightly lower than you had before. are you sure you had 17, 42 before you put it in the shop.
the speedo won't adjust. When I run 17, 44 it makes you speedo read let say 30 mph (about 50 kph) but you are actually goin about 27 mph, great if you go through the zillions of speed camera's in the UK.
hope the link helps
blue2
#3
RE: New Sprockets - 16/40?
The stock 17/42 gives the ratio 2.47. Your new 16/40 gives ratio 2.5. It is almost no difference.
The bike would rev abour 50 more rpm in 110 km/h. Or you will loose 1,3 km/h at 4100 rpm. Hardly noticeable at all.
I have changed my gearing to 17/45 (from stock 17/43 for the -87-88 Hurricane) to get a funnier bike. Te early Hurricanes have the speedo attached to the front wheel.
The bike would rev abour 50 more rpm in 110 km/h. Or you will loose 1,3 km/h at 4100 rpm. Hardly noticeable at all.
I have changed my gearing to 17/45 (from stock 17/43 for the -87-88 Hurricane) to get a funnier bike. Te early Hurricanes have the speedo attached to the front wheel.
#4
#5
RE: New Sprockets - 16/40?
as for the speedo from, the front sprocket, you only need to worry if you are going for top speed.
lower rear sprocket figure i.e 40 tooth with 17 front.
if you are going for more acceleration don't worry your speedo will under read
but there are people out there that can supply alternate drive gears
but it's weather you can be bothered to do it.
if you speedo tell you you are doing 100 mph and you are actually travelling 96 mph
who care's we have all been running false readings any way as most speedo's have a 7%
inaccuracey anyway.
as long as you are over taking your mate or a volvo what's the worry!!!!!!!!!!!!!!
Blue 2
lower rear sprocket figure i.e 40 tooth with 17 front.
if you are going for more acceleration don't worry your speedo will under read
but there are people out there that can supply alternate drive gears
but it's weather you can be bothered to do it.
if you speedo tell you you are doing 100 mph and you are actually travelling 96 mph
who care's we have all been running false readings any way as most speedo's have a 7%
inaccuracey anyway.
as long as you are over taking your mate or a volvo what's the worry!!!!!!!!!!!!!!
Blue 2
#6
RE: New Sprockets - 16/40?
Thanks for all the replies guys. I borrowed a friends GPS thingy today which gives you a live actual speed reading. When sitting on 110kph on the clock I'm only doing about 98kph actual speed, hense all the cars overtaking me last night!! Plus I also noticed it took a longer to get to my destinations.
122kph on the clock is 110 according to the GPS... so if I roughly do 10 more on my clock I'll be on the speed limits.
Now that I think about it, I rekon my old sprockets setup would have been about the same too, whenever I went for a ride with someone else and they led, they would be sitting on just over 120kph on my clock -I just thought they liked speeding. So I rekon it was out of wack originally. So now I will be sitting on around 4500rpm to sit on 110kph.
122kph on the clock is 110 according to the GPS... so if I roughly do 10 more on my clock I'll be on the speed limits.
Now that I think about it, I rekon my old sprockets setup would have been about the same too, whenever I went for a ride with someone else and they led, they would be sitting on just over 120kph on my clock -I just thought they liked speeding. So I rekon it was out of wack originally. So now I will be sitting on around 4500rpm to sit on 110kph.
#7
RE: New Sprockets - 16/40?
When I bought my bike, it had 17/40 and I changed it back to 17/42. I think he had used a speedo healer to reset his speedo to the 17/40 sprockets. I checked my speed against a GPS and found I was doing 110 when the speedo was showing just under 120.
On that basis, I ride at just under 120 on the speedo because 1 point isn't worth worring about.
When I go on group rides, there are always people whoget very indignantwhen we get to the first rest stop and they complain about having to do 120 to keep up... can't accept that their bike's speedo is inaccurate.
On that basis, I ride at just under 120 on the speedo because 1 point isn't worth worring about.
When I go on group rides, there are always people whoget very indignantwhen we get to the first rest stop and they complain about having to do 120 to keep up... can't accept that their bike's speedo is inaccurate.
#8
RE: New Sprockets - 16/40?
ORIGINAL: michnet76
so if I roughly do 10 more on my clock I'll be on the speed limits.
so if I roughly do 10 more on my clock I'll be on the speed limits.
The speedometer error is linear and can be thought of as a percent. I'll explain it and then simplify. Feel free to skip the first part.
Some one already stated the ratios:
Stock 17/42 gives the ratio 2.47 (0.4047619047619047619047619047619)
Your new 16/40 gives ratio 2.5 (0.04)
The percent difference between stock and your current setup is: 98.82
To make that really simple - at 1 kph you are really going 0.98 kph, at 10 kph you are really going 9.8 kph, and at 100 kph you are really going 98 kph.
Hang on - this does not make sense given your GPS readings?
Well there are two possible things going on here. First we have NOT considered the stock speedo error. The second is the slim possibility that your sprockets are not 16/40.
Given your numbers there is just a hair less than 10% error in speedometer reading (which includes the 1.x percent error from the different sprockets).
This is a real simple one to work out on the road. If the speedometer reads 10, you are actually doing 9. If the speedometer reads 50 you are actually doing 45 ( 10% of 50 is 50/10 or 5 -- 50 subtract 5 is 45)...
60 means 54,
70 means 63,
80 means 72
90 means 81
100 means 90
110 means 99
120 means 108 ( now your GPS read 2 kph higher - this is because I simplified to 10%. It's easier to do on the road).
When I ride - I ride about 10 km/h higher than the posted speed to not draw attention. If the sign says 80 I say it said 90 and and have my speedometer point to 99 ( 99 less the 10% error is 90).
If however the sign says 50, I think 60 and ride 66 ( 66 less 10% is 60)
#9
RE: New Sprockets - 16/40?
Jesus !!!
that last explanation was a long one. Don't think I would like to be calculating my speed all the time.
Tell me do you ever miss you breaking point?
come on every one if we are honest we break the speed limit most of the time.
the only time I check my speed is for cops and cameras.
If i was aproaching a camera and the speed was 30 mph, i would pass it at 25 MPH just to be certain.
I once met a guy with a CBR900RRW the same as my bike at the time. He said he had never broke the speed limt. I called him a liar and told him to by a 125 and save on the insurance.
that last explanation was a long one. Don't think I would like to be calculating my speed all the time.
Tell me do you ever miss you breaking point?
come on every one if we are honest we break the speed limit most of the time.
the only time I check my speed is for cops and cameras.
If i was aproaching a camera and the speed was 30 mph, i would pass it at 25 MPH just to be certain.
I once met a guy with a CBR900RRW the same as my bike at the time. He said he had never broke the speed limt. I called him a liar and told him to by a 125 and save on the insurance.
#10
RE: New Sprockets - 16/40?
Thanks for the info woot... yes I understand the ratio thing. I just summised the 10kph difference as a guide. SA cops are pretty good with their speed detection stuff...most don't bother if you're under 10kph over the limit as they won't chase after you if it was a handheld laser, they only want to catch the over 10kph'ers to make it worthwhile... on the other hand speed cameras have a tolerance of only 3kph. Fortunatly we don't have many of them here in the country. But even so if I sit on 60kph in a 50 zone then I'm still doing 52-53anyway. My riding style is that I stay a couple kays below the limit anyway - well most of the time ;-)