[ninjamon]

:-\ Assume for discussion purposes we're just talking tubeless here. Some of the differences are probably straightforward, like thinner front tires will turn easier, fatter fronts will be less affected by raingrooves, cracks, etc. But if any of you have experience with both, I'm wondering about such things as how well they wear, resistance to road hazards, affect on stopping the bike, overall bike handling, etc.

 

[Lacessit]

Well.. the wider tire will have a greater contact patch.. So, it will:

• grip better
• Steering response should be bit slower.
• drag more so you'll reduce your MPG a (tiny) bit

Tire wear should be the same, as it's dependant on compound not width.

I don't actually have any experience on the matter, just extapolating from my cage. I'm still on stock rubber, but I hope that'll change with the new season.

 

[hollywood]

Do you think It's a significant difference in the turning response? Is it something
you would get used to quickly? Getting new tires in two weeks!

 

[Super Sneaky Steve]

It will feel weird for the first few hundred miles then you'll get used to it quickly.

I kept my front stock and went with a 150 out back so I could fit Diablos. The stock sized front stopped just fine with upgraded pads and line.

 

[hollywood]

Thanks Steve.

 

[knightslugger]

the 120 65/70 doesn't deform from the pinch?

 

[ninjamon]

I'm curious about the statement that the wear should be the same, since it's dependent on compound rather than contact patch. If you consider an example...say a 110 front versus a 130 front, wouldn't the same motorcycle weight be supported by a smaller contact patch on the smaller, therefore more friction forces per square inch? I would think that over several thousand miles of turning, braking, etc. you would wear out the smaller tire more rapidly.

 

[MrSciTrek]

Hmmm...

If a tire has a bigger contact patch won't the weight be spread over a larger area thus reducing the PSI on the road?

If the same weight is borne onto a smaller contact patch it will have more pressure per square inch, yes?

Guess this is a topic where there can be all sorts of bench-based debate when actual on-track/road testing would set things straight.

So... racers, what're your experiences with change in width only (same brand & compound)?

 

[ninjamon]

I think you and I are saying pretty much the same thing MrSciTrek. We can take an even more extreme example...say the new Vulcan 900 with the thin 80/90-21 front, versus say, a Suzuki M50 with a 130-16 front. It just seems to me that the really thin fronts would be more prone to wear than fatter fronts. I'd like to hear from anyone who may have some experience on this. :-\

 

[fog]

This is just a question , for which I don't know the answer. With a larger contact patch , wouldn't it push thru the corner and cause more heat from friction therefore causing the tire to wear quicker ? When you are countersteering it seems that the smaller tire would glide thru the corners because of the smaller contact patch causing less friction , reducing heat and cause less wear.

That does it. LUCKY!!!! go to your room. That has got to be the most illogical set of reasoning I have ever heard. A pure mouthing (er typing)of a bunch of nonsensical words without a shred of thought.

The truth is the differences in milage is so small it is way overshrouded by driver use, and cannot be defined any better than that. If a scientific yest were to be derived with all variable controlled except the size they would wear out at exactly the same time.


Bah FOG

 

[MrSciTrek]

That's what we were looking for... voices of experience.

One tire size up is nothing relative to a driver's skill.

 

[knightslugger]

the 120 65/70 doesn't deform from the pinch?

umm... so uh... about ^... ???

 

[2001ex500]

I'm hoping to get tires in the near future too. Here is another angle on the question.

From reading other posts it appears that by up sizing the tires, the cross section becomes more peaked because the rim is narrower than the tire is optimally intended for. It is this peaked shape that leads to the increased turn in, because the bike tips off the peak more quickly so to speak. The stock size tires have a more dome shaped cross section, and so the bike tends to more gradually and progressively lean into the turn.

What is the effect of mixing the two cross sections, most commonly a 150 on the rear with a stock 110 up front? The rear wants to turn in more quickly and the front is more gradual lean. Does this alter the handling dynamics?

Does the stock front moderate the quicker turn in tendency of the larger rear?

Or does the larger rear possibly make the back of the bike want to turn in quicker than the front and produce a sort of understeer effect. I may be thinking with auto dynamics and the point does not even apply, but does anyone have any experience with this?

Thanks

 

[fog]

I'm hoping to get tires in the near future too. Here is another angle on the question.

From reading other posts it appears that by up sizing the tires, the cross section becomes more peaked because the rim is narrower than the tire is optimally intended for. It is this peaked shape that leads to the increased turn in, because the bike tips off the peak more quickly so to speak. The stock size tires have a more dome shaped cross section, and so the bike tends to more gradually and progressively lean into the turn.

What is the effect of mixing the two cross sections, most commonly a 150 on the rear with a stock 110 up front? The rear wants to turn in more quickly and the front is more gradual lean. Does this alter the handling dynamics?

Does the stock front moderate the quicker turn in tendency of the larger rear?

Or does the larger rear possibly make the back of the bike want to turn in quicker than the front and produce a sort of understeer effect. I may be thinking with auto dynamics and the point does not even apply, but does anyone have any experience with this?

Thanks

You have completly reversed reality or your understanding of tire function is retarded. Read the following piece then ask some intellegent questions.

FOG
:
Tires:

A Little word that you can write volumes about:

Where to start? In these Forums, a tire thread usually goes on for 4 pages with nothing more than subjective opinions or old wives tales centered on Brand loyalty. Nobody seems to have even a modicum of knowledge about tires.
I thought that some hard facts may help you when you think about tires or handling problems.
Were going to keep in Layman’s terms here not scientific stuff or formula.

Traction: hey that’s what tires are all about right? Part of the traction a tire gives is simply the CF (coefficient of Friction) that a particular compound gives. This can vary slightly. There is virtually no difference in CA of any compound normally used in street tires.
Most of the differences in traction of various rubber compounds comes from the hardness of the rubber. This is measured by indenting the rubber with a spring loaded devise and measuring the depth of the indentation. This “Depth” is then transcribes on a Durometor Scale There are several scales, the one that covers tires it the “D” Scale. A given tire rubber compound will measure from around 50 to 100 D. The higher number the harder. You won’t find the number on any tires but most car tires have a Wear factor number that runs from 100 to 1000 with the higher being the longest wearing. This number is not solely a hardness number alone, but that’s most of it.

Why the hardness of a tire relates so much to the traction limit of that tire is because most of the grip of a tire on the road is from the rubber deforming around the road surface irregularities. Not the CF of the rubber. So the softer the rubber the more it deforms, the more grip. It’s not hard to imagine that there are real limits to how far you can go in either direction. Too soft and the tire wears rapidly or chunks, too hard and it doesn’t grip at all. BTW this is why motorcycles can lean past 45Deg.

Ok up to now we haven’t talked about tire construction. This is also related to traction. (Well hell everything about a tire (except white walls) is related to traction).
There are three fundamental types of tire constructions. The cross Bias, The Belted cross Bias. And the Radial.

The difference lies in the way the strengthing cords are arranged (all tire have cords)
Cross Bias: this is the oldest type. The cords run from one bead or edge to the other on an angle and each layer crosses the first in the opposite angle. This produces a tire that flexes uniformly across it entire surface.

The Bias belted: Constructed as the Cross Bias, with the addition of a stiffer circumferential bead or Breaker. This give a tire with Dual flexing rates. The breaker stiffens up the tread to reduce it deformation under load, but the side walls remain more flexible

The Radial: In this tire the cords are laid at a 90 degree angle in respect to the centerline of the tire and there is no crossing, Then a strong Breaker (usually steel Mesh) in laid under the tread, virtually eliminating any tread flexing at all. The side wall must then be very flexible.

Slip Angles: This is the angle of the difference between the direction the wheel is pointed in and the actual direction of travel of the machine. Or a fair estimate of the degree of sliding.

First let me say that this is not a racer thing or something confined to hard riding near the limit of adhesion. Every tire on every machine generates a slip angle when turned. A couple of forces cause this. The natural histories of the rubber (you know, the spring back) and the construction of the tire cords. Bias tire have more self aligning torque than radials and conversely generate greater slip angles.

Tire pressure can increase /decrease the slip angle of a given tire
Watch NASCAR? When you hear the commentators talk about the car’s pushing, or is loose/tight. Then he went up/down ½ lb. in the rear to fix it. What they were doing is adjusting the slip angle of the tires with tire pressure.

OK on any vehicle: a rear with a greater slip angle than the front will tend to tighten a given turn. If this is severe the thing could be un rideable. This is the reason that you’ll always be warned that it is un wise to mix tire brands. Especially Radial and Bias types.

There are a few thousand more points that affect how tires perform, but they are off into the area we don’t need to get to.

Think about all of the above the next time you’re buying tires or have a handling problem, some of it may help.

FOG

 

[ninjamon]

FOG wrote(in part):Think about all of the above the next time you’re buying tires or have a handling problem, some of it may help.
FOG
« Last Edit: Today at 11:51:17 am by FOG »



Great post Fog...only thing is, thinking about all those things makes me want to retreat to a rubber room... . Seriously, I'm still not convinced by your earlier post that the thin and the fat tire will give the same mileage...but I appreciate your opinion. Anyone know of any good websites that cover this subject?

 

[hollywood]

Don't know any website...but I assume the diference should be minimal.
Also it has to depend on your riding style aswell.

 

[fog]

FOG wrote(in part):Think about all of the above the next time you’re buying tires or have a handling problem, some of it may help.
FOG
« Last Edit: Today at 11:51:17 am by FOG »



Great post Fog...only thing is, thinking about all those things makes me want to retreat to a rubber room... . Seriously, I'm still not convinced by your earlier post that the thin and the fat tire will give the same mileage...but I appreciate your opinion. Anyone know of any good websites that cover this subject?

There is no subject, There are a thousand variables to tire wear vs. mileage that no conclusion could be reached. On the race track I would say for me I would wear out 2 110 fronts to 1 120. But I'm a heavy front tire user. Other racers may not say the same.

FOG

 

[2001ex500]

Fog is grouchy again! ;D You never know which one will show up nice Fog or the other one.

Fog, I certainly appreciate all your expertise; it has been such a help to me on the Ex500.

I have worked with auto tires for years, modified the suspension and tires of every vehicle I've ever owned. I currently autocross a car that I rebuilt the whole suspension. I've read about and taken SCCA classes involving handling dynamics of CARS. I know car tires well, motorcycle tires not so well.

That's why I'm asking questions. If I read your post correctly (trying to tell where your answer began ) you are saying that the rear tire would have a greater slip angle and tighten the turn?

I wasn't talking about slip angle. Motorcycle tires are differnet because you have the lean factor too and this whole tire shape issue and I don't know how that factors in. And I'm not talking about maximum cornering. Just the effect of the shape on handling.

Could you re state your answer so I'm clear on what you are saying?

Thanks

 

[fog]

Fog is grouchy again! ;D You never know which one will show up nice Fog or the other one.

Fog, I certainly appreciate all your expertise; it has been such a help to me on the Ex500.

I have worked with auto tires for years, modified the suspension and tires of every vehicle I've ever owned. I currently autocross a car that I rebuilt the whole suspension. I've read about and taken SCCA classes involving handling dynamics of CARS. I know car tires well, motorcycle tires not so well.

That's why I'm asking questions. If I read your post correctly (trying to tell where your answer began ) you are saying that the rear tire would have a greater slip angle and tighten the turn?

I wasn't talking about slip angle. Motorcycle tires are differnet because you have the lean factor too and this whole tire shape issue and I don't know how that factors in. And I'm not talking about maximum cornering. Just the effect of the shape on handling.

Could you re state your answer so I'm clear on what you are saying?

Thanks

On the slip angle part. The rear could slip more or less than the front. That's what the Nascar analogy was for. If the front has a greater slip angle than the rear you have a Understeer condition and the opposite if the slip angles are reversed Oversteer. As an Auto crosser you should understand those things well (BTW in the 60s and 70s Me and My Lotus elan were virtually unbeatable in autocross in the new England Region).

On Motorcycle tires the same rules apply. The desired condition is a neutral one where both ends slip about the same. Subtle differences in Tire slip due to cord winding or Self aligning torque are what rides are referring to when they talk about tires. In many cases just a air pressure adjustment will completely reverse almost any given condition. Except unlike cars most modern Motorcycle tires gain traction as pressure is reduced.

For the street Neutral is best. But when weight transfer is considered you can go from full understeer (Lowside) to full oversteer(Highside) in the blink of an eye.

Earlier you wrote
"From reading other posts it appears that by up sizing the tires, the cross section becomes more peaked because the rim is narrower than the tire is optimally intended for. It is this peaked shape that leads to the increased turn in, because the bike tips off the peak more quickly so to speak. The stock size tires have a more dome shaped cross section, and so the bike tends to more gradually and progressively lean into the turn."

Not so: a nice rounded tire when pinched onto a smaller rim remains rounded albiet at a smaller radius. The triangle shaped tire is made that way at the factory, and is not altered much by a similar pinch, except to steepen the triangle shape a bit. The purpose of such a design is not to cause it to tip in easier but to generate a greater contack patch when leaned over.

Generally speaking when a bike is going down the road with the tire straight up and down , nothing matters except to keep the rim up off the ground. Everything happens at some lean angle or other. and then the forces involved are beyond this discussion.

FOG



FOG

 

[2001ex500]

OK, I think I understand you now. I certainly understand understeer/oversteer; you couldn't make any suspension adjustments without it(especially tire pressue during a race). I see I have completely misunderstood the effect of the shape of the tire and that was throwing a whole other force into the equation that I couldn't get a handle on. ???

Can you help me there? So it's not the shape. Why does a bike with these pinched tires turn in quicker as people keep saying?

Thanks Fog!