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Discussion Starter · #1 · (Edited)
I'll save y'all who dont want to read all this or dont care about why, I'll save you time... 180/55rz17 is better than 190/50zr17. Now then, for my fellow nerds...

So, it's time for new tires, stock dunlops lasted ~3,200 miles. I am moving up to dunlop q3 tires, q2s were my favorites, and these are supposed to be better?!? We'll see. I was looking on here, and another member was asking about 190 tires (which I'm getting anyway, so I figured I'd write my results for the community. Now then, on with it right? Right.

I have had the stock 180/55zr17s obviously, and we all know how they feel. I will say my feelings for comparison anyway! Fizzer with the stockers had great turn-in, decent lean angle abilities, and fairly good grip both upright and leaned. However, I did feel that I reached the "slide point" early at higher speeds, and the feel left some to be desired (although this is more from the brand/model/sidewall stiffness than size, but I digress). So all in all a great setup, but will the other sizes be a great setup, or even a truly "EPIC" one? We will find out...

So, yesterday, I discussed my plan with a buddy who works at the shop I buy my shit from. I was going to do only 180/55 and 190/55 but he told me they had a tire that was "used" in 190/50 from a bike a kid bought and immediately put a 240/xx on (zx-10 i think?) anyway, these tires took the bike from the crate/truck it came on, to the showroom, and the to the shop...so maybe 200ft total. Brand new "used" tires fitted today after work, I can say the 190/50s suck azmar... Turn in was heavy, steering felt sluggish, that being said. It did have better stability at speed and on wheelies, it also seemed to rev up slightly faster, and shift earlier when accelerating hard. Overall, I'd say they felt like extremely squared off 180/55s. I will explain why for y'all that don't know too much about tire sizing...

The first three numbers denote width in millimeters, so 190/xx is 190mm wide, now this varies from manufacturer to manufacturer because they take this measurement in different places, but not a whole lot. The second pair is the tire height as a percentage ratio to width, so, 190/50 is 190mm wide multiplied by 50%(or .50 for you arts and literature folks) =95mm "tall." Now then a 180/55 is 99mm "tall". I say "tall" because that is inside "edge" of the tire to the point in the middle of the tread, so a 180/55 is overall 8mm taller. This means the circumference is 77.9 inches on the 180/55 and 76.91 on the 190/55, an INCH less per revolution of the tire!

Here is a cross section of the tires I am discussing courtesy sportrider.com






photo (1).JPG

So we can see the difference here... Wide and flat versus tall and skinny (only discussing the 180/55 and 190/50). Im sure you can see why turn-in and steering would be affected negatively, as well as why stability would be better... If not PM me and I will explain in more detail, as I have more to cover here... Now then why would rev-up and shifting be affected...

The fz-09 is geared as follows
1) 40/15 or 2.66
2)38/19 or 2.00
3)34/21 or 1.62
4)29/21 or 1.38
5)25/21 or 1.19
6)28/27 or 1.04

With a final ratio of 16F 45R on the sprockets. (2.81 for y'all using that system). So, with the stock 180/55 tire you will be going these speeds at redline per gear, I will also include the rpm drop when shifting at redline(all theoretically)...
1)67.3mph/~2700rpm drop
2)89.7mph/~2300rpm drop
3)110.8mph/~1700rpm drop
4)129.9mph/~1600rpm drop
5)150.7mph/~1400rpm drop
6)173mph/top gear.

versus 190/50

1)66.4mph/~2900rpm drop
2)88.6mph/~2600rpm drop
3)109.4mph/~2100rpm drop
4)128.3mph/~1800rpm drop
5)148.8mph/~1600rpm drop
6)170.8mph/top gear

Obviously, above 130mph or whatever it doesn't pertain in a practical sense...

These may not seem like a huge difference, but it will alter the shift dynamics and the rev character of the bike. Also, torque multiplication comes into effect because of the difference in tire height. Basically trading speed per gear for torque per gear. Its a fairly complicated equation to get torque, so I'll only do 1st gear...

*(this part was an error in my work and is ammended on pg 3)Stock torque is ~60ft/lbs, so, 60*2.66(1st gear)=159.6ft/lbs, then 159.6*2.81(chain&sprocket gearing)=448.476ft/lbs. Now the tire is where it changes... the rear sprocket is 45 tooth, and is 9.75in in diameter, the 180/55 is 25.05in diameter, 190/50 is 25.03in diameter, so...
180/55=448.476*(9.75/25.05)=174.556ft/lbs
190/50=448.476*(9.75/25.03)=174.696ft/lbs
So, an extra .14ft/lb of torque at the wheel basically. This may sound rediculous I mean, thats not a huge difference. But remember,torque is angular moment of force, and it is accelerating at such a high rate in tire rpms compared to the engine, that horsepower(HP=(torque*rpm)/5252), or work being done, so in first gear, at the tire the HP is actually higher! For example, for the 180/55, at 35mph(2,217,600in per hour), the tire is turning at 28,467.26rpm, so... [(174.556*28,467.26)/5252=946.14HP] and 190/50=959.09HP, a 13HP increase more or less across the rev range. I hope y'all all can understand these mind-warping physics behind this;). *

So, in conclusion, 180/55 is better for turning than 190/50, however, a 190/50 with give you "more HP" at the wheel in terms of torque being applied and work being done, meaning easier wheelies and better acceleration! If you have any questions or you feel i messed something up along this project of a write up, feel free to correct me or ask the question on the thread or PM me! Thanks for reading! I will have the 190/55 tire on the bike this weekend and will continue this, probably sunday.
 

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Discussion Starter · #2 ·
Please note, different makes/models have different measuring systems and true "sizes", so these sizes and calculations are specific to dunlop q3 tires and to the fz-09. Obviously different bikes make different power and have different gearing.
 

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Interesting thoughts, but you can't change wheel hp with gearing, whether that's due to sprocket or wheel size. Not with spherical cow type calculations anyway, obviously there'll be a bit of difference in frictional loss. One reason why hp is a much more useful measure than torque imo.

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Discussion Starter · #4 ·
It doesnt change engine HP, it is a measure of the work being done at the point the wheel meets the road. HP is work measured as 33,000ft-lb/minute=1HP. I calculated the HP of the wheel not the engine, I can redo it in ft-lb/min rather than HP if it really bothers you(I'm being serious, not trying to start an internet fight). I just felt that HP was a unit of measurement we could all understand easier in relation to motorized vehicles.
 

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I'm not trying to argue either, find this stiff interesting.
Hp at the wheel though is horsepower at the engine minus frictional losses - you can't multiply it, unlike torque.
Changing gearing simply changes the rpm at any given speed in a certain gear - so will alter hp in that sense as you are moving the engine to a different place in the power curve. You cannot alter wheel hp across a rev range though.

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Discussion Starter · #6 ·
I'm not relating the output at the wheel to the engine rpm, rather the wheel rpm. Isolating the wheel from every thing but the power driven into it. HP output by the engine doesn't change, but neither does torque. They change throughout gearing changes, HP is directly related to torque. By basing my wheel calculations on wheel rpm rather than engine, I am finding the amount of work over time being done my the tires. By finding the momentary angular force (torque) and then converting that to work being done over time (moving and accelerating the bike) we derive the wheel hp. This is why lower gears accelerate faster. Most people know that gearing alters torque after the gear change, but by putting down more force, there is more work being done as well, therefore there is more hp at the force transfer component(tires). This is why if you've ever had a dyno tune, they put it in a 1:1 gear ration in the gearbox(or as close as possible), because the gearing will skew measurements as more force is applied in lower gears and more work is done. Does this make sense? It's kind of a weird concept to try to explain
 

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Fzbolt said:
This is why if you've ever had a dyno tune, they put it in a 1:1 gear ration in the gearbox(or as close as possible), because the gearing will skew measurements as more force is applied in lower gears and more work is done.
Is this the reason they do the dyno runs in a higher gear?
 

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I don't have time to do the calculations right now, but will try when I have time.

Try this - power is a measure of energy produced over time. The engine coverts energy from burning gas to do this. If power at the wheel can be somehow different to that at the crank, where does this extra energy come from? I can't remember my laws of thermodynamics, but I'm pretty sure energy can neither be created or destroyed. Gearboxes multiply torque, not power.

I imagine dyno runs are done in higher gears to reduce torque at the wheels and so reduce tyre slippage.

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I don't have time to do the calculations right now, but will try when I have time.

Try this - power is a measure of energy produced over time. The engine coverts energy from burning gas to do this. If power at the wheel can be somehow different to that at the crank, where does this extra energy come from? I can't remember my laws of thermodynamics, but I'm pretty sure energy can neither be created or destroyed. Gearboxes multiply torque, not power.

I imagine dyno runs are done in higher gears to reduce torque at the wheels and so reduce tyre slippage.

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This is true. You can't change the energy an engine produces through a gearbox. If this were true all of our cars would be powered by COX 0.49 cc model airplane engines.

The laws of Thermodynamics can't be violated.
 

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Discussion Starter · #10 · (Edited)
Power is work done over time (hp measures this) 1/2(mass)(velocity)^2. If the same wieght(our bikes) is accelerated faster or slower due to a gear change, the work being done and power must change as well( from the standpoint of the vehicle to the ground). And yes, this is why dyno runs are done in higher gears (1:1) not for slippage, but because 1:1 gear ratios show the torque and HP numbers more directly to the engine rpm, than wheel rpm. That way hp can be calculated using (hp=(TxRPM)/5252).. Hp is a arbitrary measurement based off torque produced and rpm, so depending on what rpm (engine or wheel) there are different amounts of power output. (Crank output vs wheel output) horsepower has nothing to do really with the energy stored in gas (energy is stored, not power) so the law of thermodynamics isn't broken.
 

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Never understood why people want to shoehorn larger tires on rims designed for smaller tires. In terms of car tires, you get more lateral flex when you put a tire that is larger than the designed width of the rim. I can imagine the same applies to motorcycles. Not an area I want to experiment with.
 

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Say you had an engine with a perfectly flat torque curve, at all RPMs the torque is the same.

At the same speed a lower gear gives more acceleration, crank torque is the same, wheel torque is higher, RPM is higher. The greater work (HP) is coming from the higher RPM with same work per crank rotation.

From the crank you go through the primary gears, whatever transmission gear you are in, the sprockets, the rear wheel (with tire) radius. All have a ratio that changes crank torque to what the contact patch gets. Is there something magic about whether the main shaft to counter shaft ratio is 1:1? I'll go with the gear being chosen to reduce torque for the dyno and to avoid the throttle maps of the low and high gears.
 

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Never understood why people want to shoehorn larger tires on rims designed for smaller tires. In terms of car tires, you get more lateral flex when you put a tire that is larger than the designed width of the rim. I can imagine the same applies to motorcycles. Not an area I want to experiment with.
Yeah, not something I mess with much either. But if you know the width of your rim you can go to the tire manufacturer's web site and see what rim sizes they recommend for the specific tire you are considering. Not all 190 tires will have the same recommended rim widths etc.
 

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Wow!
My heads hurting from reading all this ...
It started when I saw 3200 miles out of the stock tires..

Haha...still kind of an interesting read.

...
 

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Discussion Starter · #16 ·
V2bob, if by magic, you mean ideal for measuring puroses, then for the most part yes, transmission input and output are the same and make everything more accurate.

Agreed, if the tire shouldn't fit on the rim, I wouldn't force it. But most of the 190/xx tires I've looked at recommend 5.5-6 inch rims. Our bikes have a 5.5 if I'm not mistaken.

Rexster, what's wrong with 3200miles from the stockers?
 

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My rear is slick at 1457 miles...S20
I ride pretty much back roads...
I'm old & slow...

I do have a great interest in how the bike turns.

I figure the weight of a tire contributes to hp at the wheel.
Doubt I'll go 190 but I'll keep it in mind.
 

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Btw, I'm gonna try the Q3's this time around.
They're suppose to have quicker turn in...
Average weight not like the Road 3,4s
Reviews say a taller narrower profile..

We'll see...
 

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Discussion Starter · #19 ·
Slick all the way across? That's fairly impressive! Yes wieght will certainly affect performance, especially rotating driveline mass. From what I can tell, and my reason for initiating my thread, the 190/55 has a more "triangular" profile than 180/55 and much more tha the 180/55 on stock. The 190/55 should turn better and have a better contact patch at extreme lean angle. I plan on finding out for myself and posting my results for everyone here. The larger q3 tires are supposedly lighter than even smaller q2 and other models in smaller sizes. Food for thought
 

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So, an extra .14ft/lb of torque at the wheel basically. This may sound rediculous I mean, thats not a huge difference. But remember,torque is angular moment of force, and it is accelerating at such a high rate in tire rpms compared to the engine, that horsepower(HP=(torque*rpm)/5252), or work being done, so in first gear, at the tire the HP is actually higher! For example, for the 180/55, at 35mph(2,217,600in per hour), the tire is turning at 28,467.26rpm, so...
no, it's wrong. that 28467.26 rpm number is the giveaway. take a look at your tires when you're moving at 35mph, does that really look like 28000 rpm to you?

any gearing that increases (multiplies) torque at the wheel, reduces wheel rpm. that's the mechanical advantage tradeoff - a fundamental principle you got wrong which resulted in those 900+ hp numbers.

if your gearing multiplies torque at the wheel by a factor of, say, 7 (60 ft-lbs at the engine to 420 at the wheel), you'll see that wheel rpm is reduced by the same factor of 7 vs the engine. if you plug those numbers into the horsepower equation, you'll see the increase in torque and reduction in rpm cancel themselves out, resulting in the same horsepower numbers between engine and wheel. there is no multiplication of horsepower from gearing.


I hope y'all all can understand these mind-warping physics behind this
i think the rest of us understand the physics being warped here. :laughing6:
 
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