How do 27.5"s feel?

Angus Young

Thewaylander wrote:

Just a quick one,

Isn’t the pressure in the tire the pressure of air against the inner surface area of the tire not the tire area to the ground?

Aren't the two directly connected?

Thewaylander

Angus Young wrote:

Thewaylander wrote:

Just a quick one,

Isn’t the pressure in the tire the pressure of air against the inner surface area of the tire not the tire area to the ground?

Aren't the two directly connected?

All other factors being equal I’d say yes, but when you get different stiffness in side walls (due to bigger tires and so on) there will be a lot of other factors effecting the contact patch as it were. it's not really my area these days so would be just interested in a more knowledgeable person opinion.

rockmonkeysc

Sidewall stiffness may account for slight differences in the internal/external pressure but it's going to be very minor if you think about how easy it is to crush a deflated tyre by hand.

BloggingFit

RockmonkeySC wrote:

Are you and your friend similar weight? Greater momentum will account for faster rolling on smooth ground. Faster rolling tyres and different pressures will also have an effect. On smooth ground wheel size can't make it roll faster.
Geometry is probably the most significant difference between the two bikes.

I'm heavier but we were pretty even when both on 26" and if anything his lighter Giant rolled a little quicker.

BloggingFit

Rim width and tyre width can also be factors. Then there's the physical construction of casing and tread as to what cross section you get. Air temp can be a factor as air is a spring of sorts under load. Lots and lots of variables.

rockmonkeysc

BloggingFit wrote:

RockmonkeySC wrote:

Are you and your friend similar weight? Greater momentum will account for faster rolling on smooth ground. Faster rolling tyres and different pressures will also have an effect. On smooth ground wheel size can't make it roll faster.
Geometry is probably the most significant difference between the two bikes.

I'm heavier but we were pretty even when both on 26" and if anything his lighter Giant rolled a little quicker.

Heavier will maintain speed better when rolling.

Thewaylander

RockmonkeySC wrote:

BloggingFit wrote:

RockmonkeySC wrote:

Are you and your friend similar weight? Greater momentum will account for faster rolling on smooth ground. Faster rolling tyres and different pressures will also have an effect. On smooth ground wheel size can't make it roll faster.
Geometry is probably the most significant difference between the two bikes.

I'm heavier but we were pretty even when both on 26" and if anything his lighter Giant rolled a little quicker.

Heavier will maintain speed better when rolling.

though with a greater cross section this will increase wind resistance and slow you down more

rockmonkeysc

Thewaylander wrote:

RockmonkeySC wrote:

BloggingFit wrote:

RockmonkeySC wrote:

Are you and your friend similar weight? Greater momentum will account for faster rolling on smooth ground. Faster rolling tyres and different pressures will also have an effect. On smooth ground wheel size can't make it roll faster.
Geometry is probably the most significant difference between the two bikes.

I'm heavier but we were pretty even when both on 26" and if anything his lighter Giant rolled a little quicker.

Heavier will maintain speed better when rolling.

though with a greater cross section this will increase wind resistance and slow you down more

It will take a lot of extra wind resistance to counteract the increased momentum.

Angus Young

Fat people have more wind resistance? Who knew?

Thewaylander

Angus Young wrote:

Fat people have more wind resistance? Who knew?

I guess that depends on the amount of fat, also on how much curry they had the night before aswell.

rockmonkeysc

A rounded belly and a good lump of back fat could improve aerodynamics. A big nose might help even more.

Thewaylander

but solid fart and a match may aid acceleration greatly?

The Rookie

RockmonkeySC wrote:

Sidewall stiffness may account for slight differences in the internal/external pressure but it's going to be very minor if you think about how easy it is to crush a deflated tyre by hand.

May be true for a road type tyre but what about knobblies where each knob will cause a deflection as it pushes in the carcass locally, I would imagine that could get quite significant on tyres with a stiffer carcass.

rockmonkeysc

The Rookie wrote:

RockmonkeySC wrote:

Sidewall stiffness may account for slight differences in the internal/external pressure but it's going to be very minor if you think about how easy it is to crush a deflated tyre by hand.

May be true for a road type tyre but what about knobblies where each knob will cause a deflection as it pushes in the carcass locally, I would imagine that could get quite significant on tyres with a stiffer carcass.

It will be insignificant. I understand what you are trying to say about the deflection but the knobs wont have that sort of effect as it would only be sidewall stiffness that could cause a pressure differential and to be honest I'm starting to doubt that now, I need to get my old mechanics textbooks out and refresh my memory. I rely too much on modelling software (Siemens NX) these days, I have got a bit lazy.

2_chickens

Knobs, belly fat and ignited farts - do all threads go this way in here.

rockmonkeysc

2_chickens wrote:

Knobs, belly fat and ignited farts - do all threads go this way in here.

No, there was one about bikes as a midlife crisis purchase. I got that one on to boobs.

Thewaylander

mmmm boobs...

thats what i would describe riding a 650b as... riding on boobs

rockmonkeysc

Thewaylander wrote:

mmmm boobs...

thats what i would describe riding a 650b as... riding on boobs

I would describe my Cane Creek as like floating on a cloud of titties

BloggingFit

Thewaylander wrote:

mmmm boobs...

thats what i would describe riding a 650b as... riding on boobs

Plastic or natural?

Fox = Plastic
Rockshox = Natural

...?

Thewaylander

I go natural :P

rockmonkeysc

BloggingFit wrote:

Thewaylander wrote:

mmmm boobs...

thats what i would describe riding a 650b as... riding on boobs

Plastic or natural?

Fox = Plastic
Rockshox = Natural

...?

Manitou = botched boob job.

Wily-Quixote

Angus Young wrote:

supersonic wrote:

What is your opinion on 650b, Angus?

....

As for 26ers, it's difficult to make a case for the 26 inch wheel given that it's a purely arbitrary size choice (note, this is not the same as saying there's anything wrong with it). Maybe they just got lucky and picked the best size wheel for mountain biking purely by chance? So then it comes down to nothing more than, 26 is best, everything else is evil because I've a ton of legacy spares in my shed.....

That's an interesting point: 26ers evolved purely arbitrarily and, consequently, formed mountain bike trails evolved around the 26 inch wheel. it's no accident that a 29er feels unwieldy around a bike park designed around the 26inch wheel and wheelbase. had the 29er wheel been the original standard then mountain bike trails would have been designed with more flow, less tight radius turns and so forth. The 26 inch wheel feels 'perfect' because it is perfect for trails designed around it.

None of these things occur in nature they are purely designed around the attributes of the wheel, the bike geometry and wheelbase. Of course, as bike design evolved in capability (suspension geometry etc) the trails became more difficult to suit, which prompted more aggressive bike design. an arms race, if you will, between the capabilities of the bike and the design of the trail. The older readers here would remember that DH trails in the 80s were pretty much the same as x-country courses now.

Chunkers1980

You really think trails are designed around a wheel size?

A 29er is just as arbitrary as a 26", perhaps 650b is the only researched size?

felix.london

Wily-Quixote wrote:

None of these things occur in nature they are purely designed around the attributes of the wheel, the bike geometry and wheelbase. Of course, as bike design evolved in capability (suspension geometry etc) the trails became more difficult to suit, which prompted more aggressive bike design. an arms race, if you will, between the capabilities of the bike and the design of the trail. The older readers here would remember that DH trails in the 80s were pretty much the same as x-country courses now.

What in God's name are you talking about man? Get a grip, you need to be taken by the shoulders and shaked (shaken?) and possibly slapped round the face til you come back to your senses. Stop thinking about it so much and ride man!

benpinnick

RockmonkeySC wrote:

BloggingFit wrote:

Thewaylander wrote:

mmmm boobs...

thats what i would describe riding a 650b as... riding on boobs

Plastic or natural?

Fox = Plastic
Rockshox = Natural

...?

Manitou = botched boob job.

yeah but they are fixing it now... I have 2 sets of Mattocs for testing, and now I have bothered to figure out the settings (it has 4 adjustments that have big effects) they are pretty sweet. Still have the crown on the wrong side but hey ho.

Angus Young

Wily-Quixote wrote:

That's an interesting point: 26ers evolved purely arbitrarily and, consequently, formed mountain bike trails evolved around the 26 inch wheel. it's no accident that a 29er feels unwieldy around a bike park designed around the 26inch wheel and wheelbase. had the 29er wheel been the original standard then mountain bike trails would have been designed with more flow, less tight radius turns and so forth. The 26 inch wheel feels 'perfect' because it is perfect for trails designed around it.

None of these things occur in nature they are purely designed around the attributes of the wheel, the bike geometry and wheelbase. Of course, as bike design evolved in capability (suspension geometry etc) the trails became more difficult to suit, which prompted more aggressive bike design. an arms race, if you will, between the capabilities of the bike and the design of the trail. The older readers here would remember that DH trails in the 80s were pretty much the same as x-country courses now.

Mmmm... no.

Wily-Quixote

Chunkers1980 wrote:

You really think trails are designed around a wheel size?

A 29er is just as arbitrary as a 26", perhaps 650b is the only researched size?

Of course trails designed for mountain bikes are designed around the 26 inch wheel size, or at least they were until recently. Do you think that tight radius turns and switchback singletrack occurs in nature? Or for motor vehicles?
The first mountain bikes were converted cruisers using the 26 inch wheel size. As MTBs evolved the trails were designed around them... It wasn't as if MTB trails were just sitting there waiting for. Bike to come along.
Have you never noticed that foot trails, animal tracks and backcountry roads are quite different to MTB trails to ride on?

felix.london

stop being silly.

BloggingFit

Wily-Quixote wrote:

Chunkers1980 wrote:

You really think trails are designed around a wheel size?

A 29er is just as arbitrary as a 26", perhaps 650b is the only researched size?

Of course trails designed for mountain bikes are designed around the 26 inch wheel size, or at least they were until recently. Do you think that tight radius turns and switchback singletrack occurs in nature? Or for motor vehicles?
The first mountain bikes were converted cruisers using the 26 inch wheel size. As MTBs evolved the trails were designed around them... It wasn't as if MTB trails were just sitting there waiting for. Bike to come along.
Have you never noticed that foot trails, animal tracks and backcountry roads are quite different to MTB trails to ride on?

It's all true.

All the potholes left in the road network is an attempt to get all larger size wheel formats away from the 26" specific bike parks and use the tarmac trails instead.

It's a conspiracy man.

kajjal

Wily-Quixote wrote:

Angus Young wrote:

supersonic wrote:

What is your opinion on 650b, Angus?

....

As for 26ers, it's difficult to make a case for the 26 inch wheel given that it's a purely arbitrary size choice (note, this is not the same as saying there's anything wrong with it). Maybe they just got lucky and picked the best size wheel for mountain biking purely by chance? So then it comes down to nothing more than, 26 is best, everything else is evil because I've a ton of legacy spares in my shed.....

That's an interesting point: 26ers evolved purely arbitrarily and, consequently, formed mountain bike trails evolved around the 26 inch wheel. it's no accident that a 29er feels unwieldy around a bike park designed around the 26inch wheel and wheelbase. had the 29er wheel been the original standard then mountain bike trails would have been designed with more flow, less tight radius turns and so forth. The 26 inch wheel feels 'perfect' because it is perfect for trails designed around it.

None of these things occur in nature they are purely designed around the attributes of the wheel, the bike geometry and wheelbase. Of course, as bike design evolved in capability (suspension geometry etc) the trails became more difficult to suit, which prompted more aggressive bike design. an arms race, if you will, between the capabilities of the bike and the design of the trail. The older readers here would remember that DH trails in the 80s were pretty much the same as x-country courses now.

I have seen the changes you mention. We used to go to coed y brenin when it first opened with 26" hard tails. It was very different to the trails in the hills and mountains we were used to riding. I now tend to ride red trails on my 29er hardtail which is good to learn smooth fast riding. This comes in handy when riding tracks and trails in the middle of nowhere but is not quite as technical or uneven.

Some of the full suspension bikes now for me take the fun and challenge out of riding off road. They are very easy to handle, smooth out the rough stuff and are easy to jump / land. We used to ride rigid bikes with really poor cantilever brakes on trails people now bomb down on FS bikes.