Suzuki GSX-R Motorcycle Forums Gixxer.com banner

1 - 20 of 20 Posts

·
Registered
Joined
·
25 Posts
Discussion Starter #1
Hi all
K4 1000, new to me 16,000km bike, PO had put new 530 chain and sprockets on 17/42, I have done -1 on the front and love it, really wakes the bike up.
Now what I was thinking about was that it has a 190/55 on the back and from playing with the Healtech app the change from 50 to 55 is like -1 tooth on the back so I basically loose 30% of the benefit from the -1 at the front or close enough.
So should I also do +1 or 43t on the rear? This will also return the wheel to its orignalish spot as the -1 required the wheel to be moved to rear a bit.
Cheers
 

·
Hand-Eye Coordinator
Joined
·
6,509 Posts
If it's a street bike, it doesn't really matter. That being said...

You cannot get hung up on printed tire sizes and gear ratios. You need to actually measure the circumference of the rear tire while mounted to the rim to get actual data. I say that, because different manufacturers have different tire profiles.

Given the host of different brands and applications of tires, I will actually stick to 3 brands' top-end track tires, because that's what I know and the starkest contrast, I believe.

Looking at the rear wheel, from the rear of the bike, you will notice how tire profile looks different on the following:

Michelin- at the top of the tire, it almost looks like the center of the tire comes to an apex. It almost looks like it comes to more of a 'point' of a triangle shape like a capital 'A.'

Pirelli- Looking at the top of the wheel, it looks much more bulbous and 'fatter.' Shaped like a Greek omega. 'Ω.'

Dunlop- Again, looking at the top profile, it will fall pretty much in the middle between Pirelli and Michelin.

Wanna throw another wrench into the equation? How about inflation pressure and/or riding 2 up? That will change gearing ratios a little, too.

If you've found a setup that you like, keep it. If you wanna fuck with it, ride a gearing combo for a hundred miles and if you don't like it, swap out a sprocket. If you wanna recoup some of the cash, you can sell the sprockets you don't want. I know "conventional wisdom" (which in itself, is an oxymoron) says that one needs to change both sprockets and chain all at once, but doing 100 miles on one set and swapping it all is not needed. I went through at least a half-dozen gearing changes last year on the same chain.

Finally, if all you are doing is cruising, single rear tooth adjustments are moot. You aren't gonna notice changes at 5k rpm. You gotta be well over 10k rpm to notice the subtle changes.
 

·
Super Moderator
Joined
·
14,942 Posts
I don't have any hard data on this (and probably couldn't do the math anyway) but I am also running -1 on the front of my 1000 and went from a 190/50 to a 190/55 without noticing any difference whatsoever in low end acceleration.
 

·
Registered
Joined
·
416 Posts
If it's a street bike, it doesn't really matter. That being said...

You cannot get hung up on printed tire sizes and gear ratios. You need to actually measure the circumference of the rear tire while mounted to the rim to get actual data. I say that, because different manufacturers have different tire profiles.

Given the host of different brands and applications of tires, I will actually stick to 3 brands' top-end track tires, because that's what I know and the starkest contrast, I believe.

Looking at the rear wheel, from the rear of the bike, you will notice how tire profile looks different on the following:

Michelin- at the top of the tire, it almost looks like the center of the tire comes to an apex. It almost looks like it comes to more of a 'point' of a triangle shape like a capital 'A.'

Pirelli- Looking at the top of the wheel, it looks much more bulbous and 'fatter.' Shaped like a Greek omega. 'Ω.'

Dunlop- Again, looking at the top profile, it will fall pretty much in the middle between Pirelli and Michelin.

Wanna throw another wrench into the equation? How about inflation pressure and/or riding 2 up? That will change gearing ratios a little, too.

If you've found a setup that you like, keep it. If you wanna fuck with it, ride a gearing combo for a hundred miles and if you don't like it, swap out a sprocket. If you wanna recoup some of the cash, you can sell the sprockets you don't want. I know "conventional wisdom" (which in itself, is an oxymoron) says that one needs to change both sprockets and chain all at once, but doing 100 miles on one set and swapping it all is not needed. I went through at least a half-dozen gearing changes last year on the same chain.

Finally, if all you are doing is cruising, single rear tooth adjustments are moot. You aren't gonna notice changes at 5k rpm. You gotta be well over 10k rpm to notice the subtle changes.

The number printed on the side of the tyre 100% matters...

All the tyre manufacturers have their own individual profiles from the dead center of the tyre, to the outer edge of the tyre, but......

The overall circumference and diameter of the dead "Center" of a brand new tyre will be near on exactly the same Regardless.... of tyre manufacturer, for a given tyre size.

IE... a brand new (Pirelli / Dunlop / Michelin sized in 190/55), will all have near on exactly the same overall circumference and diameter at the dead center of the tyre...



As to the OP's question, he is correct comparing a stock OEM geared (42 rear) and tyre (190/50) K4 1000 with -1 front tooth (16), to his K4 1000 with -1 front (16) and rear (42) utilizing a (190/55) tyre.

Having the (190/55) he is losing out some advantage of - 1 front (16) tooth, because of the larger diameter (190/55) compared to the smaller diameter (190/50).

Adding +1 rear (43 tooth) to the rear, he will restore just about all (99%) of the advantage lost (gearing ratio) from the (190/55).

If the OP went +2 rear (44 tooth) with his (190/55), he would have slightly more advantage, than stock OEM with - 1 front (16), (42) rear with a (190/50).

Which way to go, the OP can make their own decision.



The difference in overall circumference and diameter between the K4 OEM size of (190/50), compared to the newer size of (190/55) is as follows.

190/55/17 diameter = 640.8mm (overall circumference 2013.13mm)

19mm taller diameter than

190/50/17 diameter = 621.8mm (overall circumference 1953.44mm)
 

·
Registered
Joined
·
25 Posts
Discussion Starter #5
Thanks mate
That makes sense to me!
It seems like every second 600/750 owner does the -1/+2 mod on their smaller capacity bikes that already have a tooth or two less on the front than a 1000 and most are more than happy with the result.
The thou is well able to pull the lower gearing but even with -1 it's only reving at 5 grand at 110km on our over speed enforced Sydney highways so I suppose fitting a 43 or 44 rear sprocket won't end the world and as Mcbayne says I can always put the 42 back on.
 

·
Registered
Joined
·
416 Posts
Thanks mate
That makes sense to me!
It seems like every second 600/750 owner does the -1/+2 mod on their smaller capacity bikes that already have a tooth or two less on the front than a 1000 and most are more than happy with the result.
The thou is well able to pull the lower gearing but even with -1 it's only reving at 5 grand at 110km on our over speed enforced Sydney highways so I suppose fitting a 43 or 44 rear sprocket won't end the world and as Mcbayne says I can always put the 42 back on.

No worries...

Here are the calculated figures @ your selected ( 110km/h ) using the Gear Ratios and Circumference of a brand new 190/55 for reference only...

( Obviously excluding drive line loses thru gear mesh, tyre slip on the road, and tyre size variation from wear / temperature / tyre deflection etc in the perfect world... )

Calculating it is a lot easier and cost you nothing. :smile:




4351 rpm @ 110km/h in 6th gear (190/50) (17/42) stock gearing...

So gain 272 rpm going to -1 front (16) below.

4623 rpm @ 110km/h in 6th gear (190/50) -1 front (16), (42) rear...

So lose 137 rpm (lose 50.53% of - 1 front (16) gain with (190/50) switching to a (190/55) below).

4486 rpm @ 110km/h in 6th gear (190/55) -1 front (16), (42) rear...

So only 30 rpm less of (190/50) -1 front (16), (42) rear. ~ 99.39 % of 4623 rpm below.

4593 rpm @ 110km/h in 6th gear (190/55) -1 front (16), + 1 rear (43)...

So gain 77 rpm more than (190/50) -1 front (16), (42) rear, slight increase...

4700rpm @ 110km/h in 6th gear (190/55) -1 front (16), + 2 rear (44)...
 

·
Registered
Joined
·
25 Posts
Discussion Starter #7 (Edited)
Now there are some very helpful facts.
So to sum it up...

Stock.
4351 rpm @ 110km/h in 6th gear (190/50) (17/42) stock gearing.

-1t front.
4623 rpm @ 110km/h in 6th gear (190/50) -1 front (16), (42) rear. = +272rpm @ 110km over stock.

-1t front, 190/55 tyre.
4486 rpm @ 110km/h in 6th gear (190/55) -1 front (16), (42) rear. = +135rpm @ 110km over stock. (current set up)

-1t front, 190/55 tyre, +1 (43t) rear.
4593 rpm @ 110km/h in 6th gear (190/55) -1 front (16), + 1 rear (43). = +242rpm @ 110km over stock.

-1t front, 190/55 tyre, +2 (44t) rear.
4700rpm @ 110km/h in 6th gear (190/55) -1 front (16), + 2 rear (44). = +349rpm @ 110km over stock.

So if I go from a 42t to a 44t rear sprocket my rpm will only increase 214rpm (from current set up) @ 110km/h give or take a few rpm's for variation.

Which in the big picture is nothing.

It's off to MCA to get a 44t for me!

Thank you!!
 

·
Registered
Joined
·
416 Posts
Now there are some very helpful facts.
So to sum it up...

Stock.
4351 rpm @ 110km/h in 6th gear (190/50) (17/42) stock gearing.

-1t front.
4623 rpm @ 110km/h in 6th gear (190/50) -1 front (16), (42) rear. = +272rpm @ 100km over stock.

-1t front, 190/55 tyre.
4486 rpm @ 110km/h in 6th gear (190/55) -1 front (16), (42) rear. = +135rpm @ 100km over stock. (current set up)

-1t front, 190/55 tyre, +1 (43t) rear.
4593 rpm @ 110km/h in 6th gear (190/55) -1 front (16), + 1 rear (43). = +242rpm @ 100km over stock.

-1t front, 190/55 tyre, +2 (44t) rear.
4700rpm @ 110km/h in 6th gear (190/55) -1 front (16), + 2 rear (44). = +349rpm @ 100km over stock.

So if I go from a 42t to a 43t rear sprocket my rpm will only increase 214rpm (from current set up) @ 100km/h give or take a few rpm's for variation.

Which in the big picture is nothing.

It's off to MCA to get a 43t for me!

Thank you!!

All my figures in post #6 were calculated at your selected 110km/h from your previous post, not 100km/h as you stated.

Damn it! I meant 44 Tooth! Where is the edit option??
The edit button is at the bottom right hand corner, of each of your own posts.
 

·
Hand-Eye Coordinator
Joined
·
6,509 Posts
The number printed on the side of the tyre 100% matters...
Within a given manufacturer/tire line range, yes, to a point. It still won't give you consistent circumference size/gearing ideas unless one measures. The only thing that number tells you is that the tire is taller or shorter than another within the tire line.

All the tyre manufacturers have their own individual profiles from the dead center of the tyre, to the outer edge of the tyre, but......

The overall circumference and diameter of the dead "Center" of a brand new tyre will be near on exactly the same Regardless.... of tyre manufacturer, for a given tyre size.

IE... a brand new (Pirelli / Dunlop / Michelin sized in 190/55), will all have near on exactly the same overall circumference and diameter at the dead center of the tyre...
Nearly the exact same? Within what percentage? Nope, not buying it. I've switched manufacturers within the same day and the distance between tire and swingarm changes between brands. There may be a lot of factors at play, but profile is one because contact patch changes. Just because a tire is "called" a 55, doesn't mean that it is exactly 55% and behaves the same way as a 50. Naming convention is 5% increments.


190/55/17 diameter = 640.8mm (overall circumference 2013.13mm)

19mm taller diameter than

190/50/17 diameter = 621.8mm (overall circumference 1953.44mm)
Within tire line and in theory. You are posting absolute diameter of a tire. NOT correct. Mount the tire, inflate to running pressure, rider mounts the machine, then measure from the ground to axle centre. THAT is the diameter... well, I guess, radius. A Michelin with a narrower contact patch at 24 psi (recommended) will compress more than a Pirelli with a wider contact patch at 26 psi (recommended)... again, in theory, and practice. Tires across brands and compounds will compress differently.

You missed the entire point of my post. If one wants to pick fly shit out of pepper, he has to measure. Using three different types of pepper could mean three different types of fly shit.

Profile, pressures, and naming convention is all moot to absolute gearing discussion. The only way to be sure is to measure.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #11
Ok thanks edits edited, it was late for me last night...anyway ordered a 44t steel 530 today should be in Thursday.
Looking at your calculations it would appear that for every 1 tooth increase on the rear engine rpm increases approx 100rpm at 110km.
Can't wait to try it!
 

·
Premium Member
Joined
·
24,541 Posts
Ok thanks edits edited, it was late for me last night...anyway ordered a 44t steel 530 today should be in Thursday.
Looking at your calculations it would appear that for every 1 tooth increase on the rear engine rpm increases approx 100rpm at 110km.
Can't wait to try it!
Knock yourself out:
https://www.gearingcommander.com/
 

·
Registered
Joined
·
416 Posts
Within a given manufacturer/tire line range, yes, to a point. It still won't give you consistent circumference size/gearing ideas unless one measures. The only thing that number tells you is that the tire is taller or shorter than another within the tire line.

Nearly the exact same? Within what percentage? Nope, not buying it. I've switched manufacturers within the same day and the distance between tire and swingarm changes between brands. There may be a lot of factors at play, but profile is one because contact patch changes. Just because a tire is "called" a 55, doesn't mean that it is exactly 55% and behaves the same way as a 50. Naming convention is 5% increments.

Within tire line and in theory. You are posting absolute diameter of a tire. NOT correct. Mount the tire, inflate to running pressure, rider mounts the machine, then measure from the ground to axle centre. THAT is the diameter... well, I guess, radius. A Michelin with a narrower contact patch at 24 psi (recommended) will compress more than a Pirelli with a wider contact patch at 26 psi (recommended)... again, in theory, and practice. Tires across brands and compounds will compress differently.

You missed the entire point of my post. If one wants to pick fly shit out of pepper, he has to measure. Using three different types of pepper could mean three different types of fly shit.

Profile, pressures, and naming convention is all moot to absolute gearing discussion. The only way to be sure is to measure.

"That number" you say... ie the aspect ratio gives you the tyre height from the percentage of the tyre width, which when doubled and added to the diameter of the rim, gives you the overall diameter of the tyre... which you use to calculate the Nominal Circumference...... of a brand new tyre... to use in gearing calculations. Doesn't get more consistent than that...... The diameter isn't used in gearing calculations, only the circumference.

Tyres will be manufactured to set tolerances for each size, there isn't going to be massive variation...


You didn't read my statement in post #6...

To quote my self...

"Here are the calculated figures @ your selected ( 110km/h ) using the Gear Ratios and Circumference of a brand new 190/55 for reference only...

( Obviously excluding drive line loses thru gear mesh, tyre slip on the road, and tyre size variation from wear / temperature / tyre deflection etc in the perfect world... )
"


Using the nominal brand new tyre circumference as a reference, makes it very easy to compare the effect of the gearing changes, along with the circumference change, from the different size aspect ratio's available.

Yes you can measure your own tyre for sure, but if you want to change the width or aspect ratio (directly related to each other), you'd have no idea of the effect it would make, without either going to a tyre shop and measuring the circumference of a brand new tyre, or simply using the calculated nominal circumference from the marked size on the side of the tyre, as an informed guide.
 

·
Hand-Eye Coordinator
Joined
·
6,509 Posts
And you didn't read my posts. You are ballparking things, which is perfectly fine, but OP wanted to pick flyshit out of pepper. Measuring circumference gives one only that number. With tire deformation with respective pressures and profile, one contact patch may "squish" more than another. The most accurate measurement is comparisons of radius from axle centre to the ground at pressure and rider weight.
 

·
Registered
Joined
·
416 Posts
And you didn't read my posts. You are ballparking things, which is perfectly fine, but OP wanted to pick flyshit out of pepper. Measuring circumference gives one only that number. With tire deformation with respective pressures and profile, one contact patch may "squish" more than another. The most accurate measurement is comparisons of radius from axle centre to the ground at pressure and rider weight.

So your implying that, the Static radius of a tyre measured to the ground of a stationary bike, is exactly the same radius to the ground, as a bike at speed... Total rubbish...

The radius of a tyre will change from deformation to the road during use a fair amount, but the change in overall circumference length of a tyre would be totally negligible in comparison...

With the tyre deformed to the road, the overall circumference length will be the same.

This is the reason why gearing calculations use the overall circumference of a tyre... For each wheel revolution, the tyre will travel the overall circumference length across the ground.


The 2 tyre sizes in question from the OP was a (190/50) and his (190/55) which he currently has fitted.

How is he meant to measure a tyre he doesn't have fitted!!! ??? (190/50)...... to compare the difference in gearing with his larger circumference (190/55)... He can't...

The whole Crux of the OP's question was comparing the effect to the gearing from the two sizes (190/50) and (190/55)...

Just measuring his currently fitted (190/55) won't tell him Squat about the comparison effect of the (190/50)!!!......
 

·
Hand-Eye Coordinator
Joined
·
6,509 Posts
So your implying that, the Static radius of a tyre measured to the ground of a stationary bike, is exactly the same radius to the ground, as a bike at speed... Total rubbish...
I never said that. Total rubbish is correct.

The radius of a tyre will change from deformation to the road during use a fair amount, but the change in overall circumference length of a tyre would be totally negligible in comparison...

With the tyre deformed to the road, the overall circumference length will be the same.

According to what empirical data?


This is the reason why gearing calculations use the overall circumference of a tyre... For each wheel revolution, the tyre will travel the overall circumference length across the ground.
Not if the tire compresses at the contact patch or if the tire actually expands at a certain speed.


The 2 tyre sizes in question from the OP was a (190/50) and his (190/55) which he currently has fitted.

How is he meant to measure a tyre he doesn't have fitted!!! ??? (190/50)...... to compare the difference in gearing with his larger circumference (190/55)... He can't...
2 rims, maybe? Or how about removing one and measuring the next once mounted, then start crunching gearing numbers, then make adjustments?

The whole Crux of the OP's question was comparing the effect to the gearing from the two sizes (190/50) and (190/55)...

Just measuring his currently fitted (190/55) won't tell him Squat about the comparison effect of the (190/50)!!!......
Fucking EXACTLY!

Finally.

My whole goddamned first post highlighted the absurdity of picking flyshit out of pepper without exact data for a street bike. Matching exact gearing of a streetbike going from a worn 50 to a new 55 profile? To which decimal point shall we measure the gear ratio, sir? Don't like your gearing? Change it. Still don't? Change it again. Hauling out the J-blocks to calibrate your caliper for a new tire measurement is silly.
 

·
Registered
Joined
·
416 Posts
I never said that. Total rubbish is correct.
This statement from you... "The most accurate measurement is comparisons of radius from axle centre to the ground at pressure and rider weight."

Yes that statement above totally implies... the Static radius of a tyre measured to the ground of a stationary bike, is exactly the same radius to the ground, as a bike at speed... which is total rubbish

How can it be the most accurate measurement with the radius constantly changing as the tyre deforms. Yes total Rubbish...


According to what empirical data?
Your above quote was quoting my statement "The radius of a tyre will change from deformation to the road during use a fair amount, but the change in overall circumference length of a tyre would be totally negligible in comparison...

With the tyre deformed to the road, the overall circumference length will be the same
."

The more a tyre deforms (there is more tyre in contact with the road) and the less a tyre deforms (there is less tyre in contact with the road). The measured circumference is the most accurate measurement, the measured radius would be all over the place as the tyre deforms, plus it's impossible to measure with the bike in motion...

Obviously you wouldn't be riding on a tyre which is way under inflated.

Eg... (190/55) circumference of 2013.13mm with a radius of 320.4mm

If the tyre deforms 20mm into the road surface, it would reduce the radius to 300.4mm.

The new circumference is now 1887.46mm, a full 125.66mm shorter... That's massive!!!...

The 125.66mm doesn't just disappear from the circumference of the tyre into thin air, it's still there...


Not if the tire compresses at the contact patch or if the tire actually expands at a certain speed.
Your above quote was quoting my statement "With the tyre deformed to the road, the overall circumference length will be the same. This is the reason why gearing calculations use the overall circumference of a tyre... For each wheel revolution, the tyre will travel the overall circumference length across the ground."

You can't measure tyre deformation/expansion from the radius to the ground with the bike in motion, it's constantly changing and is useless for gearing calculations as shown calculated above...

2 rims, maybe? Or how about removing one and measuring the next once mounted, then start crunching gearing numbers, then make adjustments?
Your above quote was quoting my statement "The 2 tyre sizes in question from the OP was a (190/50) and his (190/55) which he currently has fitted.

How is he meant to measure a tyre he doesn't have fitted!!! ??? (190/50)...... to compare the difference in gearing with his larger circumference (190/55)... He can't...
"

You said previously "but OP wanted to pick flyshit out of pepper. ."

You implied above comparing the two different sizes using "that number" ie (the aspect ration on the side of the tyre) to calculate the circumference is a waste of time...

You also said "The most accurate measurement is comparisons of radius from axle centre to the ground at pressure and rider weight." Wrong...

You also siad "The only thing that number tells you is that the tire is taller or shorter than another within the tire line". No the aspect ratio tells you the exact tyre height, as a direct percentage from the tyre width.

You can't measure a tyre you don't have, using the calculated norminal circumference of the two different sizes tyres, is a quick/easy and accurate way, while excluding tyre deformation / expansion out of the equation, which is totally impossible to measure anyway.


Fucking EXACTLY!
Your above quote was quoting my statement"The whole Crux of the OP's question was comparing the effect to the gearing from the two sizes (190/50) and (190/55)...

Just measuring his currently fitted (190/55) won't tell him Squat about the comparison effect of the (190/50)!!!......
"

To quote you again"The most accurate measurement is comparisons of radius from axle centre to the ground at pressure and rider weight., how does he measure a tyre he hasn't got fitted......

It's so easy and accurate to just calculate the difference in nominal tyre circumference from the different aspect ratio between the two sizes (190/50) & (190/55), which at the same time excludes all the stuff that is impossible to measure anyway...


Finally.

My whole goddamned first post highlighted the absurdity of picking flyshit out of pepper without exact data for a street bike. Matching exact gearing of a streetbike going from a worn 50 to a new 55 profile? To which decimal point shall we measure the gear ratio, sir? Don't like your gearing? Change it. Still don't? Change it again. Hauling out the J-blocks to calibrate your caliper for a new tire measurement is silly.
The OP question was spot on IMO... You still say it's "picking flyshit out of pepper without exact data for a street bike" Believe whatever you like...

It's simple as this... you use the two different tyre sizes (190/50) & (190/55) to accurately calculate the nominal tyre circumference's from their respective aspect ratio's and set them as constants... By doing this, it excludes all the stuff that's impossible to calculate. (ie excluding drive line loses thru gear mesh, tyre slip on the road, and tyre size variation from wear / temperature / tyre deflection etc in the perfect world...")

Then you can work out the direct effect the gearing changes alone... will have on the two different set constant nominal tyre circumference's of the (190/50) and (190/55).

Then you can directly compare the data to your own bike, and your'll be able to make a very well informed decision, instead of just chucking random size sprockets on it, stabbing in the dark...

That's the way I would do it.

You can do it which ever way you please.
 

·
Registered
Joined
·
25 Posts
Discussion Starter #20
Ok well...anyway regardless of what the radius of the back wheel is, I did change the rear sprocket to a 44 and did the R1 throttle mod at the same time.
The verdict is... F#%K me dead!!
Thanks fellas you helped me turn an over geared bike into the weapon I always thought a litre sports bike should be! The gears seem to flow on from one to the next,;))
 
1 - 20 of 20 Posts
About this Discussion
19 Replies
5 Participants
mrgsxr600
Suzuki GSX-R Motorcycle Forums Gixxer.com
A forum community dedicated to the Suzuki GSX-R motorcycle. Discuss the GSX-R600, GSX-R750, GSX-R1000, and GSX-R1100, and more!
Full Forum Listing
Top