Info on a Tire's Aspect Ratio

[Charlesbusa]

First the Aspect Ratio is located on your tire;

190/50zr17

The aspect ratio is the 50, meaning 50% of the width. Thus the normal busa tire height is 95mm, which defines the tire's profile(triangular vs rounded)

Now here's the REAL question what does this mean to a rider??
I searched on the web for hours and found very little info on what a tire's aspect ratio, or profile, does for the motorcycle. Here's all I could find;
"First of all, the most obvious characteristic is the width of the tire. The width, in concert with the diameter of the wheel, determines the size of the contact patch. The size of the contact patch in turn determines the load that the tire can bear, the amount of traction that will be available, how well the tire disperses water, and how much it resists steering inputs.

The diameter of the wheel and tire, in addition to its effect on the contact patch, affects the steering and stability of the bike. A larger wheel will be more stable at speed, and more resistant to steering inputs. This is in part due to the greater gyroscopic effect, but another factor is the greater contact patch caused by the larger wheel. In essence, a larger diameter wheel creates a longer contact patch, which requires more leverage to move.

The aspect ratio of the tire is the distance from the bead of the tire to the tread surface divided by the nominal width. In general, it describes the profile of the tire's cross-section; a lower aspect ratio means a flatter profile.

The profile of the tire is affected by several elements: the aspect ratio, the wheel width, the width of the tire, and the manufacturers intentions for the tire. The profile in turn affects the handling. A triangular profile will cause the bike to turn in more easily, but may make it a little more prone to tucking or falling into the turn. On the other hand, a rounder profile may be a little more difficult to turn in, but might have a little more linear response to steering inputs. This is to a great extent motorcycle dependent -- some bikes may like a particular tire, others may not."


Since 190/55 are going to become more common, I've been trying to research everything the aspect ratio changes. I will probably change to 190/55 since I love to lean.

Any comments??

I know there is some vast tire knowledge out there

 

[GSXTacy]

I think its this month sport rider that has an awsome article about tires, they could probably explain it.

 

[Charlesbusa]

I think its this month sport rider that has an awsome article about tires, they could probably explain it.

Nope, just how to read the numbers printed on the tire.

 

[Charlesbusa]

I've read that lower aspect ratio gives you more traction when the bike is straight up and down, makes sense.  So a higher aspect ratio tire should be less traction straight up, but more traction in a lean than a lower aspect ratio tire, right??  We are still dealing with the same width, just different profiles.

We know a 55 aspect ratio makes it easier to lean than a 50.  And a 50 provides more traction when the bike is straight up than a 55.

Conused yet ...

Let me try to sum it up like this;

2 tires, same everything except aspect ratio. One is 50 the other 55.

Does the 55 aspect ratio give you more traction(bigger footprint) at a lean than a 50 aspect ratio?



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[Charlesbusa]

 

[DaCol.]

If your talking about the same tire size and width then the basic answer is that a low aspect has more traction in a straight line (more rubber on the road) but turns in slower and is generally harder to go full lean right to full lean left which makes it harder to get through the turns. A high aspect has a more pointed center (not as rounded or flat as a low aspect) and will corner quicker as in falling into the turn faster and quicker. But you have to wait longer to get on the throttle out of a turn (need to be more upright).  For bikes, this is the basic difference I've found. But I've also found that unless your pushing the envelope you will not really notice any real difference just riding on the street.

 

[Charlesbusa]

If your talking about the same tire size and width then the basic answer is that a low aspect has more traction in a straight line (more rubber on the road) but turns in slower and is generally harder to go full lean right to full lean left which makes it harder to get through the turns. A high aspect has a more pointed center (not as rounded or flat as a low aspect) and will corner quicker as in falling into the turn faster and quicker. But you have to wait longer to get on the throttle out of a turn (need to be more upright).  For bikes, this is the basic difference I've found. But I've also found that unless your pushing the envelope you will not really notice any real difference just riding on the street.

First you said a lower aspect ratio has more traction in a straight line, then you said with a higher aspect ratio tire you have to wait until you're straightened up before getting on the gas.

Not trying to fault you, I do appreciate your input, just trying to get this figured out.  No one seems to know the technical side to aspect ratio...

It seems to me that if a lower aspect ratio tire gives more traction in the straight.  Then a higher aspect ratio tire would give you more traction when the bike is leaned over.  Same width, rim, everything except aspect ratio.

does anyone know this for sure...    

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[BA BUSA]

Hey Charles

The lower aspect ratio tire has a bigger contact patch when the bike is upright. The higher ratio tire has a bigger contact patch when the bike is leaned over. There is only so much availible traction for cornering,braking, and acceleration....whenever you are doing more than one of these at a time is where rider skills are tested the most. You should be very careful when braking into a turn and when accelerating out of a turn. Braking and turning along with turning and accelerating need to be done with very subtle amounts of throttle, brake, and steering input

 

[DaCol.]

Aspect Ratio, let me see  

 if I can explain without telling you the riding differences. A 190/50 on a 6" wheel means that the side wall of the tire is 50% of the width of 190 cm. Which makes it wider compaired to the heigth of the wall size. A 190/45 has even a smaller sidewall compaired to the tread width. A real example is looking at the moderns car tires. You can see this dramaticly in comparison. As far as leaning in a turn, the side wall reflex angle (that's the part that contacts the road between a straight up tire, and where the tread stops) will give you how much rubber is on the road. But that of course depends also on the tire pressure. High pressure lower contact but more stability, low pressure more contact but it also ads a squrm factor adding to less stability. This is where rider style and comfort comes in. THERE IS NO ONE PERFECT SETTING for all riders.
Hope this helps ! This is how I have always understood it as explained by a Dunlop guy !