Wide tyres - I just don't get it

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meanredspider
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Re: Wide tyres - I just don't get it

Postby meanredspider » Mon Nov 12, 2018 14:05 pm

The aero advantage of narrower tyres comes from where?
ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Mon Nov 12, 2018 14:16 pm

meanredspider wrote:The aero advantage of narrower tyres comes from where?

Holmesian deduction, my dear Watson.

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meanredspider
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Re: Wide tyres - I just don't get it

Postby meanredspider » Mon Nov 12, 2018 14:24 pm

First Aspect wrote:
meanredspider wrote:The aero advantage of narrower tyres comes from where?

Holmesian deduction, my dear Watson.


What: because they are narrow??
ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH

Svetty
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Re: Wide tyres - I just don't get it

Postby Svetty » Mon Nov 12, 2018 14:57 pm

meanredspider wrote:
First Aspect wrote:
meanredspider wrote:The aero advantage of narrower tyres comes from where?

Holmesian deduction, my dear Watson.


What: because they are narrow??


Partly due to the reduced surface area but mostly because the airflow across the tyre:rim interface is smoother. Not really an issue for shallow rims but relevant when using deeper section 'aero' rims.
FFS! Harden up and grow a pair :D

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sungod
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Re: Wide tyres - I just don't get it

Postby sungod » Mon Nov 12, 2018 19:18 pm

thegreatdivide wrote:To be fair, a Lightweight Obermayer is a wheel with ancient aerodynamic qualities. It's an overpriced, side wind catching vanity purchase that'll send you into ditch every time a bus overtakes.

if you'd ridden them for years you'd know that with the correct width tyres they don't catch the sidewind any more than other wheels, less in fact than much shallower rims such ambrosio nemesis (though the higher spoke count on those may be a factor there)

in spite of being overtaken by many buses and other large vehicles they show no propensity to send me into ditches, nor off mountain roads, so you are provably wrong there too

obermayers also have great lateral stiffness, astonishing strength, and are light, so very light, no other wheel comes close

but as you are clearly speaking from ignorance, you wouldn't know any of that

sounds more like you are just bitter that you can't afford them
my bike - faster than god's and twice as shiny

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Mon Nov 12, 2018 19:54 pm

meanredspider wrote:
First Aspect wrote:
meanredspider wrote:The aero advantage of narrower tyres comes from where?

Holmesian deduction, my dear Watson.


What: because they are narrow??
Yes I I think that's about it. I'm convinced. I don't even need any evidence.

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thegreatdivide
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Re: Wide tyres - I just don't get it

Postby thegreatdivide » Mon Nov 12, 2018 20:42 pm

sungod wrote:
thegreatdivide wrote:To be fair, a Lightweight Obermayer is a wheel with ancient aerodynamic qualities. It's an overpriced, side wind catching vanity purchase that'll send you into ditch every time a bus overtakes.

if you'd ridden them for years you'd know that with the correct width tyres they don't catch the sidewind any more than other wheels, less in fact than much shallower rims such ambrosio nemesis (though the higher spoke count on those may be a factor there)

in spite of being overtaken by many buses and other large vehicles they show no propensity to send me into ditches, nor off mountain roads, so you are provably wrong there too

obermayers also have great lateral stiffness, astonishing strength, and are light, so very light, no other wheel comes close

but as you are clearly speaking from ignorance, you wouldn't know any of that

sounds more like you are just bitter that you can't afford them


EDIT - I actually couldn't give a flying f*ck.
#f*ckwit

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meanredspider
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Re: Wide tyres - I just don't get it

Postby meanredspider » Tue Nov 13, 2018 00:20 am

Svetty wrote:
meanredspider wrote:
First Aspect wrote:
meanredspider wrote:The aero advantage of narrower tyres comes from where?

Holmesian deduction, my dear Watson.


What: because they are narrow??


Partly due to the reduced surface area but mostly because the airflow across the tyre:rim interface is smoother. Not really an issue for shallow rims but relevant when using deeper section 'aero' rims.


The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm. Whether flow is better, worse or the same over the tyre/rim is just a guess without understanding the exact flow pattern for that tyre, wheel and speed combination.
ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH

neeb
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Re: Wide tyres - I just don't get it

Postby neeb » Tue Nov 13, 2018 01:29 am

meanredspider wrote:The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm..

Hmm, I'm looking at my bike right now and it seems that between a third and a half of the wheel is below the BB level.. And that's not considering the extent to which the aerodynamics of the wheel and frame are separate or otherwise.

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meanredspider
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Re: Wide tyres - I just don't get it

Postby meanredspider » Tue Nov 13, 2018 07:41 am

neeb wrote:
meanredspider wrote:The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm..

Hmm, I'm looking at my bike right now and it seems that between a third and a half of the wheel is below the BB level.. And that's not considering the extent to which the aerodynamics of the wheel and frame are separate or otherwise.


If you do the maths, you get about 5cm2 by my reckoning - or, what, a couple of postage stamps?? You’d probably get something similar if your helmet is tipped back slightly or your jersey isn’t fully zipped.

As for shape effects, the wider trailing edge of the front tyre might (who knows) improve airflow transition to the down tube or around the forks...

Honestly, I don’t really care, but personally I doubt any noticeable/measurable difference is down to aero.
ROAD < Scott Foil HMX Di2, Volagi Liscio Di2, Jamis Renegade Elite Di2, Cube Reaction Race > ROUGH

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Tue Nov 13, 2018 07:51 am

meanredspider wrote:
neeb wrote:
meanredspider wrote:The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm..

Hmm, I'm looking at my bike right now and it seems that between a third and a half of the wheel is below the BB level.. And that's not considering the extent to which the aerodynamics of the wheel and frame are separate or otherwise.


If you do the maths, you get about 5cm2 by my reckoning - or, what, a couple of postage stamps?? You’d probably get something similar if your helmet is tipped back slightly or your jersey isn’t fully zipped.

As for shape effects, the wider trailing edge of the front tyre might (who knows) improve airflow transition to the down tube or around the forks...

Honestly, I don’t really care, but personally I doubt any noticeable/measurable difference is down to aero.
But narrower tyres feel faster. So do wider tyres, depending on what you were expecting. The thing to do is alternately fit tyres you are told are faster.

neeb
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Re: Wide tyres - I just don't get it

Postby neeb » Tue Nov 13, 2018 08:48 am

First Aspect wrote:
meanredspider wrote:
neeb wrote:
meanredspider wrote:The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm..

Hmm, I'm looking at my bike right now and it seems that between a third and a half of the wheel is below the BB level.. And that's not considering the extent to which the aerodynamics of the wheel and frame are separate or otherwise.


If you do the maths, you get about 5cm2 by my reckoning - or, what, a couple of postage stamps?? You’d probably get something similar if your helmet is tipped back slightly or your jersey isn’t fully zipped.

As for shape effects, the wider trailing edge of the front tyre might (who knows) improve airflow transition to the down tube or around the forks...

Honestly, I don’t really care, but personally I doubt any noticeable/measurable difference is down to aero.
But narrower tyres feel faster. So do wider tyres, depending on what you were expecting. The thing to do is alternately fit tyres you are told are faster.

Nope, I expected wider tyres to feel faster when I first fitted them and they quite distinctly didn’t. They were expensive tubs too, so I had plenty investment in wanting them to feel faster (not to mention be faster, which they weren’t either).

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Tue Nov 13, 2018 11:29 am

neeb wrote:
First Aspect wrote:
meanredspider wrote:
neeb wrote:
meanredspider wrote:The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm..

Hmm, I'm looking at my bike right now and it seems that between a third and a half of the wheel is below the BB level.. And that's not considering the extent to which the aerodynamics of the wheel and frame are separate or otherwise.


If you do the maths, you get about 5cm2 by my reckoning - or, what, a couple of postage stamps?? You’d probably get something similar if your helmet is tipped back slightly or your jersey isn’t fully zipped.

As for shape effects, the wider trailing edge of the front tyre might (who knows) improve airflow transition to the down tube or around the forks...

Honestly, I don’t really care, but personally I doubt any noticeable/measurable difference is down to aero.
But narrower tyres feel faster. So do wider tyres, depending on what you were expecting. The thing to do is alternately fit tyres you are told are faster.

Nope, I expected wider tyres to feel faster when I first fitted them and they quite distinctly didn’t. They were expensive tubs too, so I had plenty investment in wanting them to feel faster (not to mention be faster, which they weren’t either).
did you take any actual measurements though? Speed, for example.

Svetty
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Re: Wide tyres - I just don't get it

Postby Svetty » Tue Nov 13, 2018 13:33 pm

meanredspider wrote:
Svetty wrote:
meanredspider wrote:
First Aspect wrote:
meanredspider wrote:The aero advantage of narrower tyres comes from where?

Holmesian deduction, my dear Watson.


What: because they are narrow??


Partly due to the reduced surface area but mostly because the airflow across the tyre:rim interface is smoother. Not really an issue for shallow rims but relevant when using deeper section 'aero' rims.


The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm. Whether flow is better, worse or the same over the tyre/rim is just a guess without understanding the exact flow pattern for that tyre, wheel and speed combination.


This guy is an aerodynamics engineer with Airbus - he probably knows a little bit about these things - not as much as you though clearly :roll:

https://www.hambini.com/blog/post/bicyc ... s-fastest/
FFS! Harden up and grow a pair :D

neeb
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Re: Wide tyres - I just don't get it

Postby neeb » Tue Nov 13, 2018 14:25 pm

First Aspect wrote:
neeb wrote:
First Aspect wrote:
meanredspider wrote:
neeb wrote:
meanredspider wrote:The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm..

Hmm, I'm looking at my bike right now and it seems that between a third and a half of the wheel is below the BB level.. And that's not considering the extent to which the aerodynamics of the wheel and frame are separate or otherwise.


If you do the maths, you get about 5cm2 by my reckoning - or, what, a couple of postage stamps?? You’d probably get something similar if your helmet is tipped back slightly or your jersey isn’t fully zipped.

As for shape effects, the wider trailing edge of the front tyre might (who knows) improve airflow transition to the down tube or around the forks...

Honestly, I don’t really care, but personally I doubt any noticeable/measurable difference is down to aero.
But narrower tyres feel faster. So do wider tyres, depending on what you were expecting. The thing to do is alternately fit tyres you are told are faster.

Nope, I expected wider tyres to feel faster when I first fitted them and they quite distinctly didn’t. They were expensive tubs too, so I had plenty investment in wanting them to feel faster (not to mention be faster, which they weren’t either).
did you take any actual measurements though? Speed, for example.

Yes - I have multiple average speeds and average power figures for a couple of 30-40 mile routes - not controlled conditions obviously and doubtless not enough repetitions to be statistically robust given the other significant variables (basically wind and 2 or 3 traffic lights), but strongly indicative.

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Re: Wide tyres - I just don't get it

Postby apreading » Tue Nov 13, 2018 14:42 pm

If you are just looking at aerodynamics, you are only looking at one of many factors though.

Obviously the smaller frontal area the better aerodynamics, only a fool would suggest otherwise.

But comfort and rolling resistance also contribute to speed and/or energy conservation. See here for more than I can be bothered to type:

https://road.cc/content/feature/182519- ... ider-tyres

Wider rims are being made to support the move to wider tyres, not the other way around, and the move is based on the holistic appraisal of a variety of factors, of which aero is only one.

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Tue Nov 13, 2018 16:32 pm

...
Last edited by First Aspect on Tue Nov 13, 2018 17:06 pm, edited 1 time in total.

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First Aspect
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Re: Wide tyres - I just don't get it

Postby First Aspect » Tue Nov 13, 2018 16:36 pm

neeb wrote:
First Aspect wrote:
neeb wrote:
First Aspect wrote:
meanredspider wrote:
neeb wrote:
meanredspider wrote:The reduced frontal bluff area difference is minuscule as many (most) frames are a broader section than the tyre so the width difference only influences that figure below the BB level - a few square mm..

Hmm, I'm looking at my bike right now and it seems that between a third and a half of the wheel is below the BB level.. And that's not considering the extent to which the aerodynamics of the wheel and frame are separate or otherwise.


If you do the maths, you get about 5cm2 by my reckoning - or, what, a couple of postage stamps?? You’d probably get something similar if your helmet is tipped back slightly or your jersey isn’t fully zipped.

As for shape effects, the wider trailing edge of the front tyre might (who knows) improve airflow transition to the down tube or around the forks...

Honestly, I don’t really care, but personally I doubt any noticeable/measurable difference is down to aero.
But narrower tyres feel faster. So do wider tyres, depending on what you were expecting. The thing to do is alternately fit tyres you are told are faster.

Nope, I expected wider tyres to feel faster when I first fitted them and they quite distinctly didn’t. They were expensive tubs too, so I had plenty investment in wanting them to feel faster (not to mention be faster, which they weren’t either).
did you take any actual measurements though? Speed, for example.

Yes - I have multiple average speeds and average power figures for a couple of 30-40 mile routes - not controlled conditions obviously and doubtless not enough repetitions to be statistically robust given the other significant variables (basically wind and 2 or 3 traffic lights), but strongly indicative.
strongly indicative eh? On a good day in the summer I'm about 5 to 7% faster on the same bike over the same route than on a bad day. How much faster are you on 23c tyres than 25's exactly, because I'm sure as hell buying a set of your 23c tyres if you can really tell the difference over that much scatter in your data.

nachetetm
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Re: Wide tyres - I just don't get it

Postby nachetetm » Tue Nov 13, 2018 16:42 pm

neeb wrote:Just back from a ride after replacing the 25mm tubular on my front wheel with a 23mm again (which is what I was using until about a year ago). More or less dry roads so a rare outing for the best bike at this time of year. These are Vittoria Corsa tubs and the 23mm is actually only a bit over 22mm actual width, so quite a bit narrower than your average 23mm clincher on a wide rim. My suspicions were confirmed - the ride was sublime, the handling felt sharper and it was just plain faster. I'd been a little disappointed with the 25mm on the first few rides after installing them but had put it down to other factors - wind, fatigue etc. But now I'm sure that my intuition was right - the narrower tyres are just faster and feel better (at least on the front). It didn't feel any less comfortable either, although perhaps that was down to pressure - I'm running the front 23mm at 95psi while I'd been riding the front 25mm at 90psi which is effectively a little higher relative to the tyre width, but not by much (I'm 64kg). In both cases the rear 25mm was at 95psi.

Maybe it's the aero effect? The wheels are Campagnolo Boras with 24.2 outer width so the 23mm tubs (actually about 22.5) are just about perfect given the "at least 5%" rule for how much narower tyres should be than rims. The 25mm Corsas on the other hand are almost exactly the same measured width as the rims when fitted (24.2mm).

I do have experience of "properly" wider tyres (if not mega wide) - I run 25mm clinchers (Corsas again) on another bike which measure practically 27mm when fitted on H plus Son Archetypes. They're fine, but they're not faster. I run them at 85 front and 90 rear. In terms of comfort there's certainly a significant difference over properly bumpy surfaces such as cobbles, pot holes etc, but I don't really notice much difference on rough vs. smooth tarmac. In practice "comfort" just really isn't a factor for me on the roads I ride on, there are some bits that are worse than others and I notice that but it doesn't really impact on my riding experience.

I suppose if I was planning a ride on wet roads that involved a lot of cornering I'd take the bike with the wider clinchers for the extra security of more rubber on the road, and certainly if I was going to ride on cobbles. But for any other situation, based on my experience, I just don't get the wide tyre thing.

What am I missing?


How do you know you are faster with the narrower tire? In other words, what is your approach to measure it?

zefs
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Re: Wide tyres - I just don't get it

Postby zefs » Tue Nov 13, 2018 16:56 pm

About comfort, I tested today between my bikes back to back.

Bike 1: Race geometry - 17c internal with 25mm tires (26mm actual) -> Hutchinson Performance Tubeless
Bike 2: Endurance geometry - 19c internal with 25mm tires (28mm actual) -> GP4000sii with butyl tubes

Bike 1 was more comfortable at same psi (80 - 90) despite Bike 2 being an endurance Giant Defy which is supposed to be more forgiving. I think tire casing plays a big role, GP4000sii is known as a more stiff/harsh tire.

That said for simple tarmac I think 25mm tires are still optimal.


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