Skinny in the rear

"Jerry Everetts" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

is this a normal practice in the MTB world?

Yes, for the reasons you said, and because some frames can't fit much tire in back (I've had an old
one that couldn't even fit 2.1" tires). The downsides are these:
1. A fat rear tire adds cushioning
2. Our bike's steering angles are sometimes too slack already (from a long fork), and that just
makes it a little worse.

David said:

"Jerry Everetts" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

is this a normal practice in the MTB world?

Yes, for the reasons you said, and because some frames can't fit much tire in back (I've had an
old one that couldn't even fit 2.1" tires). The downsides are these:
1. A fat rear tire adds cushioning
2. Our bike's steering angles are sometimes too slack already (from a long fork), and that just
makes it a little worse.

The irony, of course, is that skinny tires don't roll faster. They tend to be lighter, and
therefore quicker to get up to speed, but skinny tires actually have a higher rolling resistance
than wide ones.

Miles

miles todd said:

David said:

"Jerry Everetts" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

is this a normal practice in the MTB world?

Yes, for the reasons you said, and because some frames can't fit much tire in back (I've had an
old one that couldn't even fit 2.1" tires). The downsides are these:
1. A fat rear tire adds cushioning
2. Our bike's steering angles are sometimes too slack already (from a long fork), and that just
makes it a little worse.

The irony, of course, is that skinny tires don't roll faster. They tend to be lighter, and
therefore quicker to get up to speed, but skinny tires actually have a higher rolling resistance
than wide ones.

Miles

Try telling that to the riders in Tour de France.

--
Perre

You have to be smarter than a robot to reply.

"miles todd" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

David said:

"Jerry Everetts" <[email hidden]> wrote in message

"]news:[email hidden]...

Quoted message said:

Quoted message said:

Quoted message said:

is this a normal practice in the MTB world?

Yes, for the reasons you said, and because some frames can't fit much tire in back (I've had an
old one that couldn't even fit 2.1" tires).

The

Quoted message said:

Quoted message said:

downsides are these:
1. A fat rear tire adds cushioning
2. Our bike's steering angles are sometimes too slack already (from a long fork), and that just
makes it a little worse.

The irony, of course, is that skinny tires don't roll faster. They tend to be lighter, and
therefore quicker to get up to speed, but skinny tires actually have a higher rolling resistance
than wide ones.

Miles

Gross oversimplification... but yeah, *generally* two tires, perfectly smooth, at the same psi, the
wide one will roll faster. Crazy how that works, innit?

Jon Bond

Jon Bond said:

"miles todd" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

David said:

"Jerry Everetts" <[email hidden]> wrote in message

"]news:[email hidden]...

Quoted message said:

Quoted message said:

> is this a normal practice in the MTB world?

Yes, for the reasons you said, and because some frames can't fit much tire in back (I've had an
old one that couldn't even fit 2.1" tires). The downsides are these:
1. A fat rear tire adds cushioning
2. Our bike's steering angles are sometimes too slack already (from a long fork), and that just
makes it a little worse.

The irony, of course, is that skinny tires don't roll faster. They tend to be lighter, and
therefore quicker to get up to speed, but skinny tires actually have a higher rolling resistance
than wide ones.

Miles

Gross oversimplification... but yeah, *generally* two tires, perfectly smooth, at the same psi,
the wide one will roll faster. Crazy how that works, innit?

Jon Bond

Well if I put 35 psi in my 700-23 racing tires I wouldn't get very far, but I rode all day today
with 35 psi in my MTB 2.1" UST tires. Since nobody does that but stays within the recomended max and
min psi, you will have to say that a skinny tire has less rolling resistance than a fat one.
Otherwise you are just playing games that has nothing to do with really riding those tires.

--
Perre

You have to be smarter than a robot to reply.

"Per Elmsäter" <[email hidden]> wrote

Quoted message said:

Quoted message said:

The irony, of course, is that skinny tires don't roll faster. They tend to be lighter, and
therefore quicker to get up to speed, but skinny tires actually have a higher rolling resistance
than wide ones.

Miles

Try telling that to the riders in Tour de France.

Within certain bounds, wider tires can indeed be faster than skinny.

Equal pressure, equal construction, equal rubber compound, and the wider tire has a wider, shorter
contact patch. Same size in sq inches, but different shape. So theoretically, the fatter tire loses
less energy in flexing the sidewall as it rolls along.

The trick is finding a high end wide tire of equal construction as a high end skinny.

The skinny also wins in terms of wind resistance.

Pete

Quoted message said:

Equal pressure, equal construction, equal rubber compound, and the wider tire has a wider, shorter
contact patch. Same size in sq inches, but different shape. So theoretically, the fatter tire
loses less energy in flexing the sidewall as it rolls along.

Someone claimed that traction is equal too, given two different sizes at the same pressure. This one
I can't believe.

--
Phil, Squid-in-Training

Jerry Everetts <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

Not your little sister, my bike tires. is this a normal practice in the MTB world? I used to do
this on my BMX bikes, for the reason that a skinnier tire rolls faster, but you need a bit more
traction up from to keep the front end from washing in corners.

Jerry

Being a big fan of drag racing, I've got a skinnier IRD Mythos 1.95 in the front and a signficantly
fatter 2.1 FireXC in the back for the same reasons as dragsters. No, not really. Though that is my
tire setup. Why? Because they were cheap and they work. /s

Per Elmsäter said:

Well if I put 35 psi in my 700-23 racing tires I wouldn't get very far, but I rode all day today
with 35 psi in my MTB 2.1" UST tires. Since nobody does that but stays within the recomended max
and min psi, you will have to say that a skinny tire has less rolling resistance than a fat one.
Otherwise you are just playing games that has nothing to do with really riding those tires.

--
Perre

You have to be smarter than a robot to reply.

That's intentionally missing the point. Comparing two different wheel sizes, along with radically
different tire design, introduces factors that outweigh the skinny vs wide discussion.

A fair consideration would be a 700x20 Michelin Axial Pro to a 700x28 Michelin Axial Pro. Same wheel
size, same air pressure, same construction. The bigger tire would roll faster. However, it would
weigh more, too, so a racer might be willing to give up a tiny bit of rolling resistance in favor of
better climbing or quicker acceleration.

Miles

Phil said:

Quoted message said:

Equal pressure, equal construction, equal rubber compound, and the wider tire has a wider,
shorter contact patch. Same size in sq inches, but different shape. So theoretically, the fatter
tire loses less energy in flexing the sidewall as it rolls along.

Someone claimed that traction is equal too, given two different sizes at the same pressure. This
one I can't believe.

It's closer than you might think.

The contact patch (the amount of rubber actually touching the trail) is determined primarily by the
tire pressure. At the same pressure (and assuming fairly firm trail conditions), a skinny and a fat
tire pumped to the same pressure will have about the same amount of contact with mother earth.

Thing is, as much as I'd love to believe I need a 2.35" mega-knobbie rear tire to handle my massive
power output, there are really very few places where I couldn't make do with a 1.9" semi-slick
(especially if I am careful not to be lurching all over the bike pedaling like I'm riding a pogo
stick). And there's no doubt about which of those two tires is actually faster in the other 99.5% of
the terrain I ride...

The front is a little different though - the semi-slick can be "interesting" on the front flying
through a sandy wash...

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

Mark Hickey said:

Thing is, as much as I'd love to believe I need a 2.35" mega-knobbie rear tire to handle my
massive power output, there are really very few places where I couldn't make do with a 1.9"
semi-slick

The fact that a 1.9" works as wellas a 2.35" surprises me less than the fact that you have no
problem with a semi-slick. I wouldn't want to try to climb up Mormon Loop with a semi-slick on the
back (but since you are posting, no doubt you have!).

("massive power" - hehe)

--
-BB- To reply to me, drop the attitude (from my e-mail address, at least) "It's a shallow life that
doesn't give a person a few scars" - Garrison Keillor

miles todd said:

Per Elmsäter said:

Well if I put 35 psi in my 700-23 racing tires I wouldn't get very far, but I rode all day today
with 35 psi in my MTB 2.1" UST tires. Since nobody does that but stays within the recomended max
and min
psi, you will have to say that a skinny tire has less rolling resistance than a fat one.
Otherwise you are just playing games that has nothing to do with really riding those tires.

--
Perre

You have to be smarter than a robot to reply.

That's intentionally missing the point. Comparing two different wheel sizes, along with radically
different tire design, introduces factors that outweigh the skinny vs wide discussion.

A fair consideration would be a 700x20 Michelin Axial Pro to a 700x28 Michelin Axial Pro. Same
wheel size, same air pressure, same construction. The bigger tire would roll faster. However, it
would weigh more, too, so a racer might be willing to give up a tiny bit of rolling resistance in
favor of better climbing or quicker acceleration.

Miles

But. A racer would *not* ride these two tires you propose at the *same* air pressure. He would have
considerably higher pressure in the 700*20 and therefore he would be rolling faster with the
thinner tire.

--
Perre

You have to be smarter than a robot to reply.

Per Elmsäter said:

miles todd said:

Per Elmsäter said:

Well if I put 35 psi in my 700-23 racing tires I wouldn't get very far, but I rode all day today
with 35 psi in my MTB 2.1" UST tires. Since nobody does that but stays within the recomended max
and min
psi, you will have to say that a skinny tire has less rolling resistance than a fat one.
Otherwise you are just playing games that has nothing to do with really riding those tires.

--
Perre

You have to be smarter than a robot to reply.

That's intentionally missing the point. Comparing two different wheel sizes, along with radically
different tire design, introduces factors that outweigh the skinny vs wide discussion.

A fair consideration would be a 700x20 Michelin Axial Pro to a 700x28 Michelin Axial Pro. Same
wheel size, same air pressure, same construction. The bigger tire would roll faster. However, it
would weigh more, too, so a racer might be willing to give up a tiny bit of rolling resistance in
favor of better climbing or quicker acceleration.

Miles

But. A racer would *not* ride these two tires you propose at the *same* air pressure. He would
have considerably higher pressure in the 700*20 and therefore he would be rolling faster with the
thinner tire.

--
Perre

You have to be smarter than a robot to reply.

Commonly believed to be true, but also pretty much a myth. Tires are designed to run at a certain
air pressure, and engineered for optimum performance at that specified pressure. Some years ago I
spoke at length with an engineer for Continental tires about this subject. He told me that (barring
a few specialty models) their road tires are designed for optimum rolling resistance at a pressure
high enough that when the rider is on the bike, the tire has a 15% drop. If it's 2cm tall with no
weight on the bike, it should deform to 1.7cm with a rider on board. If the pressure is
significantly higher, he explained, the carcass of the tire does not conform well to road
irregularities. Instead of rolling smoothly along, it jars and bumps as it travels down the road,
actually causing greater rolling resistance.

Miles

"miles todd" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Per Elmsäter said:

But. A racer would *not* ride these two tires you propose at the *same*

air

Quoted message said:

Quoted message said:

pressure. He would have considerably higher pressure in the 700*20 and therefore he would be
rolling faster with the thinner tire.

Quoted message said:

Commonly believed to be true, but also pretty much a myth. Tires are designed to run at a certain
air pressure, and engineered for optimum performance at that specified pressure. Some years ago I
spoke at length with an engineer for Continental tires about this subject. He told me that
(barring a few specialty models) their road tires are designed for optimum rolling resistance at a
pressure high enough that when the rider is on the bike, the tire has a 15% drop. If it's 2cm tall
with no weight on the bike, it should deform to 1.7cm with a rider on board. If the pressure is
significantly higher, he explained, the carcass of the tire does not conform well to road
irregularities. Instead of rolling smoothly along, it jars and bumps as it travels down the road,
actually causing greater rolling resistance.

You couldn't tell me this BEFORE I headed out door up to Del Mar (racetrack loop) this afternoon?

Bill "rock hard*" S.

*not just a saddle endorsement

Quoted message said:

Per Elmsäter said:

Well if I put 35 psi in my 700-23 racing tires I wouldn't get very far,

but

Quoted message said:

Quoted message said:

I rode all day today with 35 psi in my MTB 2.1" UST tires. Since nobody does that but stays
within the recomended max and min psi,

you

Quoted message said:

Quoted message said:

will have to say that a skinny tire has less rolling resistance than a

fat

Quoted message said:

Quoted message said:

one. Otherwise you are just playing games that has nothing to do with

really

Quoted message said:

Quoted message said:

riding those tires.

--
Perre

You have to be smarter than a robot to reply.

That's intentionally missing the point. Comparing two different wheel sizes, along with radically
different tire design, introduces factors that outweigh the skinny vs wide discussion.

A fair consideration would be a 700x20 Michelin Axial Pro to a 700x28 Michelin Axial Pro. Same
wheel size, same air pressure, same construction. The bigger tire would roll faster. However, it
would weigh more, too, so a racer might be willing to give up a tiny bit of rolling resistance in
favor of better climbing or quicker acceleration.

Miles

Well, that settles it... I'm going with 2.7's front & rear!
--
Slacker

Slacker said:

Quoted message said:

Per Elmsäter said:

Well if I put 35 psi in my 700-23 racing tires I wouldn't get very far, but I rode all day today
with 35 psi in my MTB 2.1" UST tires. Since nobody does that but stays within the recomended max
and min
psi, you will have to say that a skinny tire has less rolling resistance than a fat one.
Otherwise you are just playing games that has nothing to do with really riding those tires.

--
Perre

You have to be smarter than a robot to reply.

That's intentionally missing the point. Comparing two different wheel sizes, along with radically
different tire design, introduces factors that outweigh the skinny vs wide discussion.

A fair consideration would be a 700x20 Michelin Axial Pro to a 700x28 Michelin Axial Pro. Same
wheel size, same air pressure, same construction. The bigger tire would roll faster. However, it
would weigh more, too, so a racer might be willing to give up a tiny bit of rolling resistance in
favor of better climbing or quicker acceleration.

Miles

Well, that settles it... I'm going with 2.7's front & rear!

Me too. Especially on my roadbike.
--
Perre

You have to be smarter than a robot to reply.

BB said:

Mark Hickey said:

Thing is, as much as I'd love to believe I need a 2.35" mega-knobbie rear tire to handle my
massive power output, there are really very few places where I couldn't make do with a 1.9"
semi-slick

The fact that a 1.9" works as wellas a 2.35" surprises me less than the fact that you have no
problem with a semi-slick. I wouldn't want to try to climb up Mormon Loop with a semi-slick on the
back (but since you are posting, no doubt you have!).

I rode Ritchey SpeedMax tires (2.1" though) up and down National a few times. It actually worked out
surprisingly well - in fact, only on a couple really loose climbs were they any less capable than
"real knobbies", and I did have to take it easy on the fast, wiggly sandy sections (the front tends
to wash out a bit). But they hooked up on the rock sections better than any knobby I've ever ridden.

Quoted message said:

("massive power" - hehe)

Yeah, I can't wait for THAT to be a problem...

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

"Per Elmsäter" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Slacker said:

Quoted message said:

Per Elmsäter wrote:
>
> Well if I put 35 psi in my 700-23 racing tires I wouldn't get very far, but I rode all day
> today with 35 psi in my MTB 2.1" UST tires. Since nobody does that but stays within the
> recomended max and min
> psi, you will have to say that a skinny tire has less rolling resistance than a fat one.
> Otherwise you are just playing games that has nothing to do with really riding those tires.
>
> --
> Perre
>
> You have to be smarter than a robot to reply.
>
>

That's intentionally missing the point. Comparing two different wheel sizes, along with
radically different tire design, introduces factors that outweigh the skinny vs wide
discussion.

A fair consideration would be a 700x20 Michelin Axial Pro to a 700x28 Michelin Axial Pro. Same
wheel size, same air pressure, same construction. The bigger tire would roll faster. However,
it would weigh more, too, so a racer might be willing to give up a tiny bit of rolling
resistance in favor of better climbing or quicker acceleration.

Miles

Well, that settles it... I'm going with 2.7's front & rear!

Me too. Especially on my roadbike.
--

Balderdash! The optimum pressure for the 28 at would be less than the optimum pressure to run the
20. At equal pressure the 20 would be obviously underinflated and roll poorly.

Selwonk said:

"Per Elmsäter" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Slacker said:

> Per Elmsäter wrote:
>>
>> Well if I put 35 psi in my 700-23 racing tires I wouldn't get very far, but I rode all day
>> today with 35 psi in my MTB 2.1" UST tires. Since nobody does that but stays within the
>> recomended max and min psi, you will have to say that a skinny tire has less rolling
>> resistance than a fat one. Otherwise you are just playing games that has nothing to do with
>> really riding those tires.
>>
>> --
>> Perre
>>
>> You have to be smarter than a robot to reply.
>>
>>
>
> That's intentionally missing the point. Comparing two different wheel sizes, along with
> radically different tire design, introduces factors that outweigh the skinny vs wide
> discussion.
>
> A fair consideration would be a 700x20 Michelin Axial Pro to a 700x28 Michelin Axial Pro. Same
> wheel size, same air pressure, same construction. The bigger tire would roll faster. However,
> it would weigh more, too, so a racer might be willing to give up a tiny bit of rolling
> resistance in favor of better climbing or quicker acceleration.
>
> Miles

Well, that settles it... I'm going with 2.7's front & rear!

Me too. Especially on my roadbike.
--

Balderdash! The optimum pressure for the 28 at would be less than the optimum pressure to run the
20. At equal pressure the 20 would be obviously underinflated and roll poorly.

Finally. Somebody understands. If it hadn't been for you I might have been talked into riding my mtb
tires on my roadbike and who knows what else 😉

--
Perre

You have to be smarter than a robot to reply.