anybody go to 28mm tires, and NOT like the switch?

[moyboy]

ZIPP 303 NSW Disc are 21 mm internal now... the non-disc ones are 19mm

Good to know. I've only seen people saying Conti bulbs out like 10%. As i run tubular only, i have noted several tires are even a tiny bit smaller than spec.
Wonder if i rode clincher, that would mean i should use 23mm tires to get actual 25mm width!?

BTW, NSW is 19mm internally not 21mm.

[bilwit]

28mm (measured) is definitely more comfortable and feel great when on rough road.. but also makes me feel like I'm driving a bus in comparison to "skinny" tire. 25mm (measured) is the sweetspot for me

Can you be more specific?

Does the steering feel heavier? Does a big soft tire just feel vague because there is less sense of the road surface? Technically, a taller tire will increase trail which will result in steering that is more responsive to bike lean, so in a sense the bike will steer more with less lean - the opposite of the "bus" feeling. Of course the difference is so small it shouldn't be noticeable. The contact patch is larger at lower pressures, so perhaps that is what causes the more sluggish feel. Just harder to turn the bars. But once in motion that should be a non-issue.

I do notice a difference in handling but it's hard to describe. Like the bike is less darty with bigger tires, but not because there is less response to steering inputs. Rather it's more as if larger softer tire kicks back against road imperfections much less when I am cornering. Everything just gets dulled and neutralized - which is sort of the goal.

It just feels less lively and less twitchy (which makes sense since the contact patch is horizontally larger rather than vertically stretched). Eating up and absorbing all the imperfections and bumps on rough terrain is appreciated, but when on regular roads that dullness feels amplified and turns dead, disconnected.

For me 28mm (measured) is the perfect tool for the job on my rain bike. On my normal "fast" bike I'll stick with 25mm (measured). At 61kgs, 25mm pumped up to 70/75 PSI (even 65/70) is plenty fat and plenty plush for normal riding. That said, I will definitely never be going back to truly skinny tire pumped up to 100+ PSI.

[Dan Gerous]

I went back to 25mm on my main/light/fast bike... I didn't feel enough of a difference in grip, speed and comfort to add a bit more rotational weight. Actually, I should rather say I'm not placing comfort that high in my priorities and don't like to feel too isolated from the road (I also don't like wearing gloves, using too thick bar tape and I was fine riding older super stiff alloy bikes for hours even on rough roads). I also thought that light tubes were getting more stretched and easier to puncture in 28mm tires so I was using heavier or bigger tubes than in 25mm tires.

But I used to ride 28mm on my endurance bike and went to 32mm there as I use it more for gravel than paved roads and it now feels like the two bikes complement each other better across different uses.

[Calnago]

Same as @Dan Gerous, I gave it the old college try with 27mm Vlanderen tubulars. Super comfy of course, but it was like driving a Cadillac instead of a Porsche. I just like the “feel” of the 25’s better on the nice road bikes and feel more connected to the road. On my touring bike I ride 32mm clinchers and it gets loaded up at 95lbs (gear and bike) before I sit on it. I tried 37mm on it but again, on paved roads just didn’t need it. And even with the 32mm and all that weight, many gravel roads were traversed. So until further notice, I’m on 25mm tubulars on all my road bikes. Just my preference.

[spdntrxi]

I dont feel 28 are too bad... not cadillac anyways. I have 650x47 WTBs on my AllRoad.. that is straightup couch, but fun as hell. I run 28 @ 60psi and tubeless and handling is very good. My WTB's are 30psi... it's crazy I dont even feel disconnected with those. (but they are heavy)

[Shrike]

Did you guys notice less punctures on 28s than on 25s?

[Dan Gerous]

Did you guys notice less punctures on 28s than on 25s?

I had more punctures with 28s but that's partly explained by using the same size tubes so they were more stretched as mention above. But, even with properly sized, thicker tubes, I had more flats on the 28s, I think it's more because my 28s were Vittoria Corsa G+ and my 25s were Conti GP4000. The Conti are pretty resistant while Corsas are more prone to punctures, those grooves in the thread seem to pick little debris and keep them there and as you roll they eventually make it through... A theory, maybe the rubber is just easier to pierce or it's just luck or lack of.

[Nefarious86]

The punctures would have been down to the Corsa being a horribly fragile tyre not the "tube stretch"

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[cunn1n9]

Tubeless has been an eye opener for me. It was a pain to learn to do. I made lots of mess and swore at the tyres that can be very hard to put on. BUT since moving to them:
- I have never had a puncture on the road.
- my spares kit is a dynaplug pill, a CO2, a mini pump. No tubes no levers nothing else. I know this is sufficient to repair anything as I have used this to repair my CX tyres out on gravel rides. So my spares kit is much smaller as well. More marginal gains...


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[Mr.Gib]

The punctures would have been down to the Corsa being a horribly fragile tyre not the "tube stretch"
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The consensus seems to be that GP4000 is better at resisting punctures than the Corsa. Oddly I have done much better with the Vittorias than the Continentals. Fewer cuts, fewer punctures. The Conti's always ended up with tons of little cuts and I was constantly digging bits of crap out of the rubber. I have worn bald Corsas that have zero cuts. I have tens of thousands of km on each so a really good sample. The only thing I can think of that might be a factor is I run the Corsas at much lower pressures than I used to run the GP4000s (and also use a latex tube instead of butyl). It's true that debris seems to stick to the Corsa more when it is new, but that hasn't resulted in any punctures. Might just be the nature of the debris on the roads in my area.

[ducman]

Which corsa type did you use?
Do they 'roll' as fast as GP4000?

[Mr.Gib]

Which corsa type did you use?
Do they 'roll' as fast as GP4000?

Just the regular Corsa, in all sizes 23, 35, and 28.

As fast as GP4000? No way to tell of course. Didn't get dropped riding the GP4000, still not getting dropped riding the Corsas Lab tests give the edge in speed to the GP4000. On the road - who knows? In theory the Corsa will be faster on rough roads due to greater suppleness. But again, no way to be certain. Let's just say they are fast enough.

[Dan Gerous]

Which corsa type did you use?
Do they 'roll' as fast as GP4000?

Just the regular Corsa, in all sizes 23, 35, and 28.

As fast as GP4000? No way to tell of course. Didn't get dropped riding the GP4000, still not getting dropped riding the Corsas Lab tests give the edge in speed to the GP4000. On the road - who knows? In theory the Corsa will be faster on rough roads due to greater suppleness. But again, no way to be certain. Let's just say they are fast enough.

Couldn't tell if one rolled faster than the other either, grip is also similar, excellent on both. The Corsa do feel different though, they even sound a little different, the cotton casing is very smooth... but, they don't last as long, they puncture easier and they're much heavier than the GP4000... well, they're heavier than most high end clinchers, even more so when you consider the 25mm GP4000 is about the same size as a 28mm Corsa...

[ducman]

What about the current 2.0 version...

[joshatsilca]

Has any other study been conducted on the topic?
I for sure know that Michelin did test tires over different surfaces for like forever (the axial at least) but never recall anything published confirming silca “blog” whom science appeared very doubtful at times (recall the wheel/tire vertical stiffness that had little solid ground)


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Tom anhault came up with the same findings independantly. Also... the guys on mountain bikes intuitively have known the same data without actual formally studying it... forever. To a lesser degree, same with race car drivers (but that is a bit different, but “higher is fastest, or lowest is fastest” is the reality they discovered is not true). The rougher the surface, the lower the pressures... the faster you are. But not too low. The trick is to find that sweet spot for every rider/condition.

What is the fastest tire/wheel combo? It is influenced by many factors:
- Wheel weight
- wheel shape (aero)
- mounted tire width
- tire pressure
- tire pressure effects mounted width
- tire width effects aero performance (too wide is bad)
- tire construction (rolling resistance)
- road surface (how rough)

The silca “blog” is worth the read... i say it is essential reading. As is the related “marginal gains podcast.” Josh was a big part of the zipp wheel development process. He also has been and advisor for many pro tour teams (currently EF, prevously with bora/sagan, wiggins 1hr record, etc). When the smartest person in the room speaks, we become smarter by listening.

Also, check out slowtwitch, as it is full of people in competition, many of whom are on the cutting edge of “best practices”. I was learning about tire pressures over there (pre reading the five part silca articles on the topic)... and i started quoting bike rolling resistance numbers (good source, but does not take into account impedance losses from rough surfaces), and someone basically told me... “keep your pressures up if you wish, i just hope you are conpeting in my age group.”

RocketRacing, thanks for the kind words. As for C36, Tom Anhalt has data nearly identical to ours and the wheel/tire vertical stiffness data that you call doubtful was replicated almost identically by Damon Rinard and to my knowledge there is nobody else that has even tried it much less refuted it. While I understand scepticism and still have tons of it myself on all of these topics, the data from an instron pushing things into tires is pretty straightforward and has little room for interpretation. What we do with the data or think it means is another story..
Josh