Fat tyres - what are the benefits and short commings.

[motogman]

To continue this thread with a little different direction and some more fat tire questions...

I just picked up a 74 Eldorado that has 16 " rims and wide / fat tires.  I just picked the bike up today and left it at a shop and have not deep dived what I have yet - that comes later this week.

But...

In my other post or somewhere ...  some one indicated that the CHP Eldos used 16" rear tires - and I think somebody said they were 5.10s - which would equate to something like a 130.  Mu guess is that the police bikes got these rear tires because they were carrying more weight (radio, siren, guns & ammo, donuts etc.).

For the time being...  I am going to keep these rims but the tires are probably 30 years old.  Does anybody have any experience with 16" fat tires on an Eldo?  What current tire would work on this bike?

[Kev m]

Fat/bobber front tires weigh more so effect the handling of your steering.  It's like you have a flywheel on the front rim and you can't ignore it.  With a front end like that there's no way you are going to be able to haul ass thru a corner like I can on my MuZ 660 single w/a 110/70-17 front tire.   

AND...

fat tires slow the steering and make the bike less flick-able.

...I think these are true statements, but the second better reflects the sliding scale and the subjective nature of how much it matters.

I'm sure there's a tipping point for everyone, as even I have stated that I've made changes to narrow tires on some of my bikes for a handling feel that I prefer.

But the truth of the matter is whether most bikes will haul ass through a corner or not on the street is probably limited by the rider not the bike. I mean, yeah, there are some that are just too fat, too low, too long, etc. for real aggressive street cornering, but even most "lowly" Harleys can be hussled through corners on the street to surprise the less experienced riders on much more capable bikes.

So in the end it all comes down to the individual and what they want/enjoy.

[oldbike54]

 So Kev , ya callin' Harley riders fat 

 Dusty

[Kev m]

So Kev , ya callin' Harley riders fat 

 Dusty

I believe it is grammatically clear enough that the statement was in fact about the bikes. 

[oldbike54]

I believe it is grammatically clear enough that the statement was in fact about the bikes. 

 Dunno , sometimes it seems we speak a different dialect of the Queen's own language here, than is employed along the Eastern Coast . (Danged emos)

 My understanding is that it isn't so much the slight weight difference in a larger tire that slows down the steering , more to do with profile and resistance to roll .

 Dusty

[agoldfish]

My understanding is that it isn't so much the slight weight difference in a larger tire that slows down the steering , more to do with profile and resistance to roll .

 Dusty

Its both!!! I have a ... fanatical friend back in the UK and he weighs EVERYTHING that goes on his bike!!! A few years ago now he was work for Petronas Racing as one of the telemetry guys, had access to a huge selection of tyres and being the way he is, weighed them all. At the time Michelin had the lightest tyres over Dunlop, Pirrelli and Bridgstone. The rear Michy being a whopping 450gm lighter than the heavy Dunlop.

For any of you that has ever spent money on lighter wheels for a track bike, 450gms is ALOT!!!

Mike is still a fanatic, and has been building his own hub center steered bikes for years now.
http://www.tryphonos.com/

Width also varys from brand to brand. A 180 Bridgstone BT23 is wider than the 180 Metzler that was on the bike when i bought it. It rubbed the hugger! Now i have a 170 on there that is the same width as a 180 Metzler.

Profile also is in the mix. The old front Pilot Race i used to use for track days was basically a triangle!!!

Chris

[LowRyter]

I know one rider that tells me if you go for a wider tire with the same profile, that it makes a steeper profile in the curve of the tire and makes the tire handle quicker.  (more sidewall and less on top)

I take the opposite position believing the 10mm+ width increment is a greater factor than the marginally steeper crown.  My riding experience validates that. 

I would like someone to "prove it" with actual numbers (smarter than me). 

[Kev m]

Dunno , sometimes it seems we speak a different dialect of the Queen's own language here, than is employed along the Eastern Coast . (Danged emos)

 My understanding is that it isn't so much the slight weight difference in a larger tire that slows down the steering , more to do with profile and resistance to roll .

 Dusty

Yes, completely different dialects.

Let's examine:

We were talking about how fat tires may affect handling and I started to turn the conversation about rider preferences and rider skills:

"I'm sure there's a tipping point for everyone, as even I have stated that I've made changes to narrow tires on some of my bikes for a handling feel that I prefer.

But the truth of the matter is whether most bikes will haul ass through a corner or not on the street is probably limited by the rider not the bike. I mean, yeah, there are some that are just too fat, too low, too long, etc. for real aggressive street cornering, but even most "lowly" Harleys can be hustled through corners on the street to surprise the less experienced riders on much more capable bikes."

So first I gave a disclaimer that even my relatively conservative preferences are for skinnier tires in some applications because I enjoy the feel.

But then I added that I believe in most cases it's rider skill and not tire size or bike that determines ultimately how fast a bike will corner in street situations. By that statement I say that most bikes, even with fatter tires, are probably more capable than most riders, especially given realistic limits for street riding.

Then I added a disclaimer that yes, there are some (meaning bikes themselves) which are just too fat, too low, too long etc. for real aggressive street cornering but even the most "lowly" (meaning looked down upon by many in this conversation) Harleys (again therefore talking about bikes) can be hustled...

More Clearer Now? 

[oldbike54]

 Well sure , maybe , possibly , dunno 

 Dusty

[Bulldog9]

I bet for sedate rational street riding, there is no difference between those two front tires on the V9 other than styling.  Hit the track and you'll want the fatter front tire. Why? larger contact patch means better grip, but also greater rolling resistance and slower to lean. It is a balancing act. Most sporting bikes have gone to the 120/70 17 front tire and 180-190/70 17 rear. These run what at least for now is the best compromise. 

Looking at the V9, looks like a goldilocks issue to me - - - 'too fat - - - too skinny'   But in the end, given the choice between fat or skinny, for performance and looks, I'll bow to Freddie Mercury and his crew on this....   https://www.youtube.com/watch?v=-D99n9f3vU4

[rodekyll]

Its both!!! I have a ... fanatical friend back in the UK and he weighs EVERYTHING that goes on his bike!!! A few years ago now he was work for Petronas Racing as one of the telemetry guys, had access to a huge selection of tyres and being the way he is, weighed them all. At the time Michelin had the lightest tyres over Dunlop, Pirrelli and Bridgstone. The rear Michy being a whopping 450gm lighter than the heavy Dunlop.

For any of you that has ever spent money on lighter wheels for a track bike, 450gms is ALOT!!!

Mike is still a fanatic, and has been building his own hub center steered bikes for years now.
http://www.tryphonos.com/

Width also varys from brand to brand. A 180 Bridgstone BT23 is wider than the 180 Metzler that was on the bike when i bought it. It rubbed the hugger! Now i have a 170 on there that is the same width as a 180 Metzler.

Profile also is in the mix. The old front Pilot Race i used to use for track days was basically a triangle!!!

Chris

Yes, 450g = 16 POUNDS.  Is your friend saying there's a 16# DIFFERENCE between the weight of a Michelin tire and a Dunlop tire?  These are otherwise equivalent motorcycle tires he's comparing, right?

[Toecutter]

No, 450g is a hair under 1 pound. Did you mean to write "16 ounces"?

[rodekyll]

Sorry -- yes, ounces.

I meant "it's a hair over a full pound heavier!"  (with an implied YIKES!)

I could see that with perhaps a metzler 880 (6-ply) on one side of the equation . . . but with standard sidewalls that's a big difference.

[agoldfish]

Sorry -- yes, ounces.

I meant "it's a hair over a full pound heavier!"  (with an implied YIKES!)

YEP!!! He was surprised too, this was about  .... 8 years ago though. But still, its a BIG difference. I would love to know how tyre weights have changed, or not, since then. Perhaps we should all weigh our new tyres?  :S

[Aaron D.]

Just so you know, wider tire = lower rolling resistance..

[PJPR01]

Just so you know, wider tire = lower rolling resistance..

How so?  Take a Mountain bike with fat tires compared to a road bike with skinny tires...significant ly less rolling resistance with skinnier tires than the fat ones.

[oldbike54]

 The maximum force of friction is the product of the coefficient of friction times the weight applied to the contact patch .

 Dusty

[Kev m]

The maximum force of friction is the product of the coefficient of friction times the weight applied to the contact patch .

 Dusty

And is rolling resistance the same thing as maximum force of friction (which sounds to me like total available traction say for propulsion forces, as opposed to just how much it resists turning).

[oldbike54]

And is rolling resistance the same thing as maximum force of friction (which sounds to me like total available traction say for propulsion forces, as opposed to just how much it resists turning).

 No they are independent .

 Dusty

[Aaron D.]

How so?  Take a Mountain bike with fat tires compared to a road bike with skinny tires...significant ly less rolling resistance with skinnier tires than the fat ones.

Dude! Seriously...

The pro road racers have all moved up to 25mm. I have 22mm on one bike, 28 on another-you can feel the difference.

Estimates are the difference in a 40km time trial, based solely on rolling resistance, is near 40 seconds. The difference comes from the shape of the contact patch.


Really, mountain bike tires..

[atavar]

larger contact patch means better grip

This is somewhat of a myth.  Traction depends on downward force and composition of mating surfaces and has *nothing* to do with contact patch. If there is any traction gain from a wider tire it is because of the higher weight/mass of the tire or because the wider tire is made of softer rubber. 

http://www.engineeringtoolbox.com/tractive-effort-d_1783.html

[oldbike54]

This is somewhat of a myth.  Traction depends on downward force and composition of mating surfaces and has *nothing* to do with contact patch. If there is any traction gain from a wider tire it is because of the higher weight/mass of the tire or because the wider tire is made of softer rubber. 

http://www.engineeringtoolbox.com/tractive-effort-d_1783.html

 Exactly , contact patch doesn't even come up in the equation . The reason for race bike tires increasing in width has to do with the increase in lean angle generated by modern bikes . A wider tire is simply necessary to keep a fairly gentle decrease in effective radius while keeping the tire running surface on the pavement .

 Dusty

[PJPR01]

Dude! Seriously...

The pro road racers have all moved up to 25mm. I have 22mm on one bike, 28 on another-you can feel the difference.

Estimates are the difference in a 40km time trial, based solely on rolling resistance, is near 40 seconds. The difference comes from the shape of the contact patch.


Really, mountain bike tires..

Too much coffee this morning chief or you're just not understanding the analogy I am using?  Fatter tires vs. skinnier tires is the subject. 

I'm running 29 x 2.1 on the mountain bike and 700x23 on the road bike....I've got more rolling resistance on the mountain bike tires...they are fatter/wider than the road bike.  Same analogy as the motorcycle.  You're saying that's incorrect?

[oldbike54]

Too much coffee this morning chief or you're just not understanding the analogy I am using?  Fatter tires vs. skinnier tires is the subject. 

I'm running 29 x 2.1 on the mountain bike and 700x23 on the road bike....I've got more rolling resistance on the mountain bike tires...they are fatter/wider than the road bike.  Same analogy as the motorcycle.  You're saying that's incorrect?

 Some of the change has to do with harder compounds and vertical forces . Oh hell , you guys are gonna make me have to contact my physicist buddy 

 Dusty

[PJPR01]

No need for that...just assume for all intents and purposes that all other factors are the same...a controlled experiment.

One bike with fat tires, another bike with skinny tires, both bikes exactly the same weight and component wise, you don't need to be a physicist to know after riding bikes for 40 years which one has more rolling resistance...

[atavar]

Give him a call.  I know for muscle cars the reason for bigger tires is so they can use softer rubber to get more traction, but the softer rubber requires more rubber (translates to wider) so it is strong enough that it doesn't self destruct when you put the ponies to it.  Really sucks when you tear the rubber off the carcass.
On motorcycle tires I imagine the wider tires make it easier to use a softer compound on the sidewalls where you don't have as much wear, effectively giving you more traction when heeled over in a curve.  At the same time they can leave a harder rubber in the center of the tread to give the tire longer life on the superslab.

[atavar]

Rolling resistance is a whole different color horse.  Bigger diameter tires will be deformed less and have less resistance to road deformations and obstacles.  I know for a fact that a 29" fat tire bike will easily overcome a curb or gravel that would stop a 26"x1" bike in it's tracks.
There are many many other factors at play here though, or we would be seeing fat tire bikes in the Tour.  It takes power to haul those heavy fat tires around.

[LowRyter]

For racing and for sportsbikes, those fat (rear) tires are to put the power (250+ hp) to the ground. 

Rolling resistance is not an issue when you are clawing for traction.

[atavar]

yep, and with the softer rubber compounds you need a lot of it to withstand the 250+ HP without tearing apart.  The tire gets bigger for strength, not because bigger grips better but because softer grips better.

[Tom]

Okay.....going with wider tires for better handling because of the wider contact patch and that allows for more of a lean angle in a turn.  The 1400 Eldorado handles a lot better than the Custom or the Tourer.  Don't know about the Audace or MGX21.  But, I suspect the Audace might be the best handling of the new breed.  The combo of the rake of the steering neck and 16" weenies make it and the Eldo better handling.

Yes, a wider tire = wider contact patch for more effort to get down the road.  That effort may be small and not very apparent for a motorcycle however.