Will I benefit from 25/28c tyres

[Brucey]

I'm astounded. Absolutely astounded. Fitted the new Continentals today. They only just make 28c when inflated to 8 bar. ...

glad they are comfy but the pedant in me is forced to point out that the tyres are '28mm'
not '28c' which is a misappellation (albeit a commonplace one).

The French tyre specification was originally '700C' (note; not '700c') as opposed to 700A, 700B etc. Strictly speaking any 700C tyre should be 37-622 (in ISO designation) by definition. However different tyre widths on a 622mm seat rim are made and these are often labelled 700 x 28C etc although they should be known as 28-622 in ISO. In all cases the C should be upper case and the 'size' when expressed as 700x28C is only nominal, not actual, and anyway will vary when the tyre is fitted to different rims.

The pressure and width both affect the spring rate of the tyre, but the comfort is at least as much related to the absolute pressure as it is the size of the tyre IMHO; this is because small bumps will push into a tyre instead of lifting the whole bike, which is uncomfortable. It is easier to push in at low pressures than high. It is just that if you (say) run a 23mm tyre at 80psi you will soon wreck it if you have any real weight on it, and the rolling resistance is likely to be higher than with a wider tyre at the same pressure/load. Horses for courses.

cheers

[iandriver]

Nice to read above that I'm not the only one using one size larger on the rear wheel. I run the same pressure front and back, but the back is 3mm larger, so I guess that counts.

I do the opposite and have a larger at the front, BECAUSE SHELDON SAID SO.

As opposed to what was lying around in the garage in my case. Decided I liked it and stuck with it.

[tim-b]

Hi

belgiangoth wrote

Not a fact.

It's a true statement of reality. It may not satisfy the scientists, but it's a fact

Regards
tim-b

[belgiangoth]

Hi

belgiangoth wrote

Not a fact.

It's a true statement of reality. It may not satisfy the scientists, but it's a fact

Regards
tim-b

He has done some tests and then given his conclusions. That's doesn't make it true, let alone a fact. If it doesn't satisfy "the scientists", you're just repeating what I said - it's no better than someone's opinion from allegorical evidence.

[tim-b]

Hi

Take the example of the project that exhumed Richard III http://www.le.ac.uk/richardiii/archaeology/backgroundproject.html

"probably" "provided" and "local legend" are amongst the words used to describe where he lay, and yet the team found his remains. Just because something isn't recognised as fact doesn't mean that it isn't a fact

The Higgs boson is another example, theorised in 1964

We could go around in circles on this, as the Higgs boson did at CERN in 2012

Regards
tim-b

[mjr]

But neither Richard III's burial site nor the Higgs boson were accepted as fact until proven. There are far more rumors and theories disproved than proved.

And 28 still isn't wide. 50 is wide.

[freeflow]

glad they are comfy but the pedant in me is forced to point out that the tyres are '28mm'
not '28c' which is a misappellation (albeit a commonplace one).

Opps I stand corrected. My numbers were however based on approximate measurements.

In any case I rode my first 300k audax yesterday using the new tyres. As this is only a sample of 1 its hard to give absolute opinions but I did feel that the ride was smoother without any noticable loss in speed (but at my audax speeds that isn't really an issue). I also think I had less severe shoulder ache at the end of the ride compared to my recent 200k rides. What was very clear was that the occasional sunk manhole or small pothole that was ridden over was much much less jarring that on the Pro 4.

Looking at the tyres this morning they do seem to be a much tougher breed of tyre as they appear unmarked. I've just about worn off the rubber flashing around the centre of the tyre, its still there on the front tyre. No other damage is apparent. With my Pro 4 there would almost certainly have vbeen a number of small flints stuck in the tyre and a few more small cuts.

All in all I'm quite happy with performance so far. What this spot for further updates.

[belgiangoth]

Take the example of the project that exhumed Richard III http://www.le.ac.uk/richardiii/archaeology/backgroundproject.html
Just because something isn't recognised as fact doesn't mean that it isn't a fact

The Higgs boson is another example, theorised in 1964...We could go around in circles on this, as the Higgs boson did at CERN in 2012

1 - History isn't science
2 - It's only a theory
3 - The Higgs boson didn't go round in circles, that was protons.

[tim-b]

Hi

1 - History isn't science
2 - It's only a theory
3 - The Higgs boson didn't go round in circles, that was protons.

1) In the strict definition of the words
2) Both are facts, something that is actually the case, and have been for over 500 years in the case of Richard III and however long for the Higgs boson. That we didn't recognise them before is something for us to improve upon; it would save a load of time
3) Didn't make myself clear, I was referring to the 27km ring that is the Large Hadron Collider, and no, I haven't the faintest idea whether the particle beams complete a full circle(s)

Regards
tim-b

[mjr]

Isn't the way to improve it to do the research sooner? So you know what to do about the BQ claims...

[OnYourRight]

I don’t doubt that wider tyres can roll faster than narrow tyres: they bulge less, providing less opportunity for hysteresis losses (losses caused by the tyre not rebounding to its original shape with as much force as it resisted deformation in the first place). Wheel Energy in Finland has consistently shown fatter tyres to roll better.

If the wider tyre is run at a lower pressure than the narrower tyre it swaps greater hysteresis losses for lower suspension losses, again resulting in lower rolling resistance for the wider tyre (on rougher surfaces).

The question that Jan Heine doesn’t answer to my satisfaction is the speed at which the aerodynamic advantage of a narrower tyre becomes more important than its typically small disadvantage in rolling resistance. It seems implausible to me that there could be no aerodynamic advantage on normal non-aero rims, though certainly I believe it could be small – especially at the rear where bits of the bike and rider have already accelerated the air and anyway the air is ‘dirty’.

There is also the concern that wider tyres typically weigh more, not least because their weight is rotating weight and therefore especially harmful to acceleration. However this effect is small and really only worth worrying about if you must keep up with someone else when they accelerate, i.e. if you race.

[reohn2]

The question that Jan Heine doesn’t answer to my satisfaction is the speed at which the aerodynamic advantage of a narrower tyre becomes more important than its typically small disadvantage in rolling resistance. It seems implausible to me that there could be no aerodynamic advantage on normal non-aero rims, though certainly I believe it could be small – especially at the rear where bits of the bike and rider have already accelerated the air and anyway the air is ‘dirty’.

Aerodynamics with a human being sat on top of the bike becomes a moot point IMHO,fit mudguards and it all becomes insignificant.
IMHO you'd also need to ride a pretty high average,upward of 20mph(?) to see any significant gains.
Obviously racing is a completely different kettle of fish.

There is also the concern that wider tyres typically weigh more, not least because their weight is rotating weight and therefore especially harmful to acceleration. However this effect is small and really only worth worrying about if you must keep up with someone else when they accelerate, i.e. if you race.

Agreed.
I find a difference in acceleration between light narrow HP 25,28mm(23,25 actual size) tyres and the 37(35mm actual) lightweight tyres I now ride,but it's small by comparison to the comfort the larger tyres afford and overall average speeds aren't much different(within 1 mph).
The difference at the end of a ride is incredible though,and I'm constantly surprised how fresh I still feel after riding the bigger tyres.

[mjr]

There is also the concern that wider tyres typically weigh more, not least because their weight is rotating weight and therefore especially harmful to acceleration. However this effect is small and really only worth worrying about if you must keep up with someone else when they accelerate, i.e. if you race.

I suspect there may be a "sweet spot" on the width-weight relationship curve, below which narrower tyres need to be proportionally thicker to keep their shape and accept the higher pressures needed and above which wider tyres are already at their minimum useful thickness and so just get heavier for extra width.

I know they're a controversial example, but http://schwalbe.co.uk/tour/marathon/ has a pretty wide width range in 622mm so I can look at the steps between them for a range:

• 23mm wide is 440g (19g/mm rounded 0dp)
• 25mm is 520g (+2mm +80g or +40g/mm, total 21g/mm)
• 27mm is 560g (+2mm +40g or +20g/mm, total 21g/mm)
• 32mm is 640g (+5mm +80g or +16g/mm, total 20g/mm)
• 37mm is 730g (+5mm +90g or +18g/mm, total 20g/mm)
• 42mm is 810g (+5mm +80g or +16g/mm, total 19g/mm)
• 47mm is 985g (+5mm +175g or +35g/mm, total 21g/mm)
• 50mm is 1080g (+3mm +95g or +31⅔g/mm, total 22g/mm)

Assuming those claims are fairly accurate (and that 23mm weight looks suspect put in this context), the weight penalty is roughly linear from 25mm to 42mm, then gets heavier quicker. If I remember rightly, rolling resistance improvement and aerodynamic losses are both square-order, so that would make me go for the low side of the middle of the linear increase but I'm guessing from imaginary sketches of graphs and haven't even tried to do the maths properly (sorry - my physics isn't good anyway so I'd probably get it wrong anyway). A year or so ago, some local riders suggested the 35s (Schwalbe label the 37-622 as 700x35C which causes some irritation if mudguards only just accept 35s) as the best of those tyres.

[OnYourRight]

Aerodynamics with a human being sat on top of the bike becomes a moot point IMHO,fit mudguards and it all becomes insignificant.
IMHO you'd also need to ride a pretty high average,upward of 20mph(?) to see any significant gains.

Certainly the aerodynamics of the wheels are far less important than the aerodynamics of the vastly bigger rider. But wheels still cause some drag. Your estimate of 20 MPH as some sort of cut-off speed would roughly coincide with my guess, but mine at least is a pure guess. What if it’s 16 MPH and even affects long-distance tourists? Or it might be 24 MPH and irrelevant to all but the very fastest solo riders.

Most tests I’ve seen with wind-tunnel data consider the drag of aero wheels at high speeds (i.e. the case of the triathlete). That’s not very relevant to me.

I agree that the comfort of wider tyres is a real benefit (likely far more important than any other consideration for many cyclists).

Mjr: interesting observation. However, I don’t think my bike would take tyres wider than 28 mm, so I’m essentially not interested in weight and mostly interested in comfort, rolling resistance, drag, and grip. I am currently using narrow 23 mm tyres, partly to see for myself whether I notice any drag benefit, as unlikely as that might be.

[reohn2]

Certainly the aerodynamics of the wheels are far less important than the aerodynamics of the vastly bigger rider. But wheels still cause some drag. Your estimate of 20 MPH as some sort of cut-off speed would roughly coincide with my guess, but mine at least is a pure guess. What if it’s 16 MPH and even affects long-distance tourists? Or it might be 24 MPH and irrelevant to all but the very fastest solo riders.

I really don't know of any scientific data regarding tyre width/aerodynamic effects,so my observations are purely anecdotal and I can't say I've noticed any effect of wind drag with the bigger 35mm actual size tyres,these are slicks BTW.My average speeds tested against 28s on a 70mile circuit in similar conditions are very similar 15 to 16mph.

Most tests I’ve seen with wind-tunnel data consider the drag of aero wheels at high speeds (i.e. the case of the triathlete). That’s not very relevant to me.

Nor me.

I agree that the comfort of wider tyres is a real benefit (likely far more important than any other consideration for many cyclists).

I'm a bit more sensitive to comfort than most as I have Osteo Arthritis related joint pain(fingers joints,shoulder,left knee,lower back) and will shortly need a hip replacement,I've been offered it now but I'm trying to leave it as long as possible to lessen the chances of further replacement later,I'm 61.
Wide supple lightweight tyres are far more comfortable without any drawbacks all for me.
In fact for my type of cycling(tarmac and rough stuff)I found my Thorn Audax MK3 on 28s limited me to mostly tarmac with only the mildest off road sections being able to be ridden due to comfort issues and tyre worries.So I sold it.
With the bigger tyres one thing that is immediately noticeable is the absence of high frequency vibration on tarred and chipped road surfaces and the ability to just roll over bad tarmac and mild potholes without issue or pain,something that's become normal for me these days.This comfort/plushness has the effect of making the bike seem slower but it's not in reality.
I rode with a chap for some 20miles a couple of week ago,he was half my age,fit(ish) and weighed about the same as me (83kg), on 23s on stripped down Scott sportive type bike,we were taking turns into a 10mph head wind in the high teens mph,he remarked that he had to skip around what I was riding over and openly said he couldn't quite believe the bike was so quick.
I'm no athlete.
I believe Jan Heine is though,rides PBP on 650bx42mm Hetres and comes in with the first group.