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How wide is too wide for tires?
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I’ll start off by mentioning that I’m talking about road bike tires and not for use on triathlon/TT.

When I first started cycling (which wasn’t as long ago as many of you) 19-21 mm tires were the norm and 23mm was considered a wide comfort tire. Then 23mm became the norm for a number of years. Then it seems like people stared gravitating to 25’s and greater. Now we’re at a point where two of the more venerable tire choices, Conti 5000 and Schwalbe Pro One, are offered at 32mm and 30mm. Noticing now that there are also a number of road rims out there with 25mm Internal width in order to better mate with these wide tires. And to think, I used to think about 10 years ago the Hed Belgium and Velocity A23 which were 23mm External were considered the new big thing.

So at some point are a majorly of people going to be riding 50mm slicks on their road bike? (assuming the bike had clearance and tire rime widths continues to grow). Or is there a point of diminishing returns. What would I be ‘losing’ by running a 30mm tire on a 25mm internal with vs 25mm tire on 21mm internal? Increased weight and decreased aerodynamics. But less rolling resistance with the wider setup? Any other issues width going as wide as possible? Or is the trend to go wider overkill at some point?

Thoughts?

Matt
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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Wider with lower pressure may be faster when the surface warrants it but the actual optimum tyre width is dependent on how good or bad the surface is, the specifics of the tyre/tube/wheel being used and the weight of the rider, for starters. That's before even taking aerodynamics into account. Furthermore, when you're talking about tyre widths, the number on the manufacturer's label is just a notiona value, as I'm sure you know. The actual measured width will vary significantly depending on the specific make/model of tyre and the dimensions of the rim you mount it on.

In short, as always...... It depends.
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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hi, whilst the wheel choice will have an important influence as will the road conditions, your question is basically about the tipping point for use of wide tire. One way to investigate this, is to use this calculator where you are vary the size of the tire but keep the make the same and examine the effects on rolling resistance vs aero....link is https://fft.tips/tyre2. However, this calculator is somewhat theoretical so alternatively you can investigate using this website for an example tire such as GP4000sII : https://www.bicyclerollingresistance.com/...-gp4000s-ii-23-25-28. Returning to the wheel, yes you want to match the wheel and tire in actual width +/- 5%, there is a calculator for this but I cannot locate it right now, so you might as well measure your own preferred wheel max width (external) and then match it with a suitable tyre. This doesn't answer the question of comfort and grip when, yes larger is always better...so I guess there is always a compromise. regards AG
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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Joshatsilca recently talked on his podcast estimating that tires will level out at 30-32 for most road bikes and the pros will be riding 28-30's. I think that is pretty spot on. I think that 28-32 range is the sweet spot between comfort, speed and aero.

Trackie

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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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Chemist wrote:
So at some point are a majorly of people going to be riding 50mm slicks on their road bike? (assuming the bike had clearance and tire rime widths continues to grow). Or is there a point of diminishing returns.

Of course. There's only so much rolling resistance that can be eliminated, but things like weight and aerodynamic drag have no upper bound as you make tires bigger.

I do think that super-wide slicks are much less slow than most people think, but I doubt that paved road bikes are going to keep expanding their tire widths all that much. It's worth noting that the current situation isn't historically abnormal: forty years ago, typical road tire labelled widths ranged from 25mm to 32mm. The current "wide tire" trend is as much correcting course from the late 1980s as anything else.
Last edited by: HTupolev: Sep 26, 19 10:02
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Re: How wide is too wide for tires? [KrispyK] [ In reply to ]
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KrispyK wrote:
Joshatsilca recently talked on his podcast estimating that tires will level out at 30-32 for most road bikes and the pros will be riding 28-30's. I think that is pretty spot on. I think that 28-32 range is the sweet spot between comfort, speed and aero.

I'll have to give that a listen. Do you know which episode it was? I'm wondering if he meant labeled width, or the actual measured width. I have a 25mm GP 4000 which measures almost 28mm on my rear HED Jet 6+ wheelset (25 external/21 internal). This makes me wonder if I get a 25mm internal width rim what a 28mm Conti 5000 or 30mm Schwalbe Pro One what they would balloon out to.

The author of this blog (which comes from Bicycle Quarterly) wrote that it doesn't make sense to run anything more narrow than 38 mm which seems excessive....

Matt
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Re: How wide is too wide for tires? [KrispyK] [ In reply to ]
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Agree with Josh and Krispy. 32mm seems to be the top end of speed and comfort as much bigger and you feel like you are pushing rubber on pavement. Great sweet spot on mixed surface riding seems around 38ish to me. I remember Clement silks coming in around 28-30mm seemed like riding on clouds a long time ago. Cry if they flatted early in their lives.
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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Chemist wrote:
KrispyK wrote:
Joshatsilca recently talked on his podcast estimating that tires will level out at 30-32 for most road bikes and the pros will be riding 28-30's. I think that is pretty spot on. I think that 28-32 range is the sweet spot between comfort, speed and aero.


I'll have to give that a listen. Do you know which episode it was? I'm wondering if he meant labeled width, or the actual measured width. I have a 25mm GP 4000 which measures almost 28mm on my rear HED Jet 6+ wheelset (25 external/21 internal). This makes me wonder if I get a 25mm internal width rim what a 28mm Conti 5000 or 30mm Schwalbe Pro One what they would balloon out to.

The author of this blog (which comes from Bicycle Quarterly) wrote that it doesn't make sense to run anything more narrow than 38 mm which seems excessive....

Pretty sure it was Ask Josh anything #7. One way or another it is a recent episode. If I remember correctly, he thought in the US we would settle on 30 and the Euros would settle on 28, based on the silly notion that they are more old school.

I just started using 25s, so I guess I am way behind the times. I am also skeptical of the 30 really working for TT/Tri options. Any Crr gains past 23 or 25 seem to be pretty small and I don't think you can reduce Cd enough to offset A.
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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Chemist wrote:
The author of this blog (which comes from Bicycle Quarterly) wrote that it doesn't make sense to run anything more narrow than 38 mm which seems excessive....
Heine's tire testing has produced some compelling information, but I'd note some caveats with interpreting his Marymoor test data and conclusions.

His methodology requires testing in calm conditions. This minimizes yaw, which tends to minimize the scale of aero disadvantages, and should therefore be expected to benefit the wider tires relative to typical real-world results.
Similarly, his methodology uses steady riding on flat ground. That means no acceleration or climbing, which again should benefit the wider tires relative to real-world results, even if only to a very tiny degree.
So, even if we take the "tire width had no impact on performance" conclusion at face value, we could reasonably expect the super-wide stuff to perform worse than the narrow stuff when used in more interesting riding.

Also, there's obvious opportunity cost associated with choosing a super-wide tire: nobody makes high-end aero racing equipment to pair with it. The wider the tire, the wider and deeper the rim needs to be to achieve a comparable drag coefficient to a wheel using a skinny tire. There are plenty of rims designed to enjoy good aerodynamics when paired with a 25mm tire; what's a good aero rim to pair with a 700x38mm Barlow Pass?

//===================================

The other big consideration, if we're talking about super wide stuff, is that bike design has to accommodate it in ways that aren't always convenient.

For example, the 52mm tires on my gravel bike...



With my triple setup, the driveside q-factor is 83mm from bike centerline. I can't reduce that at all without the chain rubbing against the tire in small-big, unless I switch to a crank with less space between the big ring and the crankarm (but this would still only save a millimeter or two). If the crankset was symmetric, the overall q-factor would be 166mm, and pedaling this bike would feel like riding a horse. By taking advantage of the crankarm position versatility of square taper, I've brought the actual q-factor down to 156mm. But that's still be a far cry from my other road triple, which has a delicious 142mm q-factor.
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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It's not really tire width itself that matters with aero, but rather the tire/rim system. Specifically, the EXTERNAL width of the rim should be at least 105% of the measured width of the tire - if the rim is narrower than this, you start losing the aero advantages of deep rims. So for a 28 mm measured tire, the external width of the rim should be at least 29.4 mm.

Many of the rims currently available are not wide externally enough to maintain aero benefits at 28mm, and are instead optimized for 23-25mm tires. A handful of manufacturers have 28mm compatible rims, but this is generally only their latest releases. If you start talking 30mm tires, the list of compatible deep rims gets even smaller.

The INTERNAL width is irrelevant to aero, but can have some handling implications if you get outside the recommended range.
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Re: How wide is too wide for tires? [mcalista] [ In reply to ]
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mcalista wrote:
It's not really tire width itself that matters with aero, but rather the tire/rim system...
It's both.
While the profile is important, the scale is also significant.
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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I have not seen the bicycle quarterly test. But the test sounds like it has more than a few issues if it got the results claimed.

Because, on smooth surfaces, wider tires do NOT have lower rolling resistance than narrower tires when each tire is run at appropriate width specific pressures (i.e., pressures that create appropriate tire footprints for the tire width).

Then, unless the laws of physics have recently been revised, all other things being equal, wider objects always create MORE aero drag that similarly-shaped narrow objects.

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Last edited by: DarkSpeedWorks: Sep 27, 19 7:39
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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Having just bought a new Madone, I've been wondering how wide to go on tires as well. I know a lot of people think about the tire/wheel system, but on these aero bikes (venge, madone, systemsix, etc.), what tires were they optimized for? Nobody seems to test or talk about that. It gives me pause when looking at these rims with huge external diameters (>30mm) because while it might be the most aero choice for tire/wheel, it makes me wonder if is terrible for the bike/tire/wheel system as a whole
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Re: How wide is too wide for tires? [mcalista] [ In reply to ]
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mcalista wrote:
The INTERNAL width is irrelevant to aero, but can have some handling implications if you get outside the recommended range.

It kind of does though as the internal width will dictate how wide the tire will balloon on a given rim. So when you pick a tire width to optimize aero you have to consider both your internal and external widths to determine how wide the tire will be on your wheel. Per Slowman from another similar thread I had a while back.

re: https://forum.slowtwitch.com/...e_P6854041/#p6854041

slowman wrote:
i just left a schwalbe launch. (i'm awaiting for my next flight in madrid right now, so, i *just* left that launch.) what they said, about the new Pro Ones about to be announced (i hope i'm not breaking the embargo) is that their tire widths are normalized for 19mm internal (a 28mm tires measures 28mm on a rim with a 19mm internal. the narrower the rim, the narrower the tire (which probably means the taller the tire). the wider the rim, the wider the tire. not by a ton, but by some. i think it's 1mm wider for every 2mm of extra rim width, which would mean a 28mm tire would be 29mm on a HED plus rim (21mm internal), if i understand right.

That being said, for me the question is more about a road bike where I'm going to spend a lot less time going 40+ km/hr do more interested in ride quality, grip with the tire profile, etc, etc so I don't feel overly compelled to following the classic 105% rule.

Matt
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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I just took a recent bike/tourist trip to France and for the six months leading up to it, I was considering which bike to take. I have a road bike that was likely designed around 23mm tires in 2007 and my all-road bike that is really a hybrid of a mtb frame with road components so I can use big tires. Over the last year I have really become sold on big tires (run tubeless) for my riding which generally includes about even proportions of dirt and pavement. I eventually opted for my all-road bike but I changed out the tires for a GP5000 rear and a 47mm 650b WTB Horizon up front.
The roads in France are generally very good so I wondered if the size up front might be overkill, but after three weeks and a dozen new cols, I have to say that running a 47mm large volume tire up front is awesome. I kept experimenting and was riding it as low as 22 psi up front with 45-50 psi in the rear. I only wish they made the GP5000 tl in even bigger volume tires than the 32mm—like a 38 or 42. The WTB tire is a good tire, for sure, but that new Conti tire is a REALLY good tire.
Why did I like the big front tire? It is so smooth that it just erases most bumps and when you are descending in the dark (once) and in low light with overhead tree cover (i.e. lots of dark/light transitions) it was really nice to have that big tire eat up any unforeseen cracks, bumps or road deformities. I never really intended to take it off road, but I could have handled light gravel riding easily. The one time that I chased a roadie down a pass (col du Glandon) I kept up just fine and that big front tire really grips.
As for speed, I’ve done some power meter testing with a GP4000Sii in 25mm against a G-One Speed in 2.0/50mm and a Conti mtb Raceking in 2.2 and they were all very close in time when tested on a steep climb over broken pavement. I’ve ridden my gravel bike in a paceline and not had any issues, nor would I expect to feel slower because the fastest gravel/mtb tires don’t give up much if anything to a road tire.
I suspect there is going to be a lot of resistance from roadies to bigger tires, but when you try them out, the light comes on and you wonder why you have been riding skinny tires for so long. Whether a big road tire standard ends up at 38 or 42 or 47, I don’t know, but I will certainly not riding anything smaller than that in the future except on my tri bike for races.
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Re: How wide is too wide for tires? [cdw] [ In reply to ]
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If it's just general riding on the road the wider tyres will give better comfort, and for general riding that's no 1 priority.

28c seems the the min width to me for this type of riding. That's max I can get in my Volare.

If I was to buy a new frame today I would probably get one that would take a 35c tyre and run g-one tubeless. Comfort is king when training and generally riding about. Other factors are just irrelevant.
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Re: How wide is too wide for tires? [Chemist] [ In reply to ]
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I've got two bikes -- one set up with 25mm tires on 21mm internal rims. The other set up with 32mm tires on 22mm internal rims. Mounted, both tires are 3 or 4 mm wider than marked. But some of the assumptions relative to rolling resistance go out the window. Why? Because even with the same brand and model tire, the constructions appear to differ between the two sizes. Also, wider offers less rolling resistance AT THE SAME PRESSURE. Between 25mm and 32mm, there aren't many desirable pressures in common.

I'm running both tires tubeless and I run them 10 psi apart in pressures. And the differences are pretty dramatic . . .
  • The 32mm tires (at 60 psi) are MUCH more comfortable to ride. Cadillac. We're talking 70's vintage Cadillac. Smoooooth! (And I never worry about looking for potholes when I'm riding these tires.) I occasionally run these at 55 psi, but I don't see the point in going lower.
  • The 25mm tires (at 70 psi) are MUCH faster. No comparison. Not even close. Miles per hour don't generally mean much, but the difference on the same roads is significant. I generally average between 1 and 1.5 mph faster on the 25mm tires on the same workout and same wattage. I have ridden these at 80 psi but, again, don't see the point. I'm not sure another 10 psi gets more speed.

I don't know if the speed difference is aerodynamics or tire construction or what. Ultimately, it doesn't matter. I do not ride the 32mm tires on group rides -- too slow. But if I'm in the mood for a comfort ride, they are the only choice.
Last edited by: FlashBazbo: Sep 27, 19 13:30
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