Which tire width? (28mm vs 30mm)

Going 28 front and 30 rear is an excellent idea. I don’t expect to be in any sort of a pack where I couldn’t maneuver around holes during the vast majority of my rides. I’ll probably switch out the rear on my current wheels for a 30 as well.

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Hasn’t the strict 105% rule been debunked? I recall one of the key proponents saying that it is no longer that simple. Instead, ask the wheel manufacturer what the most aero width is for their particular wheel. Which makes life more complicated.

Sorry that is vague, I can’t remember the specific references.

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Is this the option you went for in the end? What’s the benefit of going 28mm on the front and 30mm on the back?

I went with 30s for my SL8 with Roval Rapides.

I have a set of wheels I use for commuting with my gravel bike with road tires on them, recently switched from Roubaix 30/32s to 32c Cinturato Velos, when the Pirellis blew up smaller than the Roubaixs I realized the next set will be 35-36 (probably Mondos). Just really enjoy the feel of a big cushy road tire.

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Definitely go with the 28’s. At 80 psi, for example, the rolling resistance advantage of the 30’s will be measured on the order of 10’s of milliwatts. So, de minimus.

However, at yaw the difference in aerodynamic drag between the two will be materially larger. GP5k mounted on an enve foundation 45 will violate the rule of 105. So, most particularly at higher yaw, you’ll experience a few watts difference on each wheel.

Plus, the 28’s will be 20-30 grams lighter than the 30’s. So you’ll have the weight savings all day long.

Go with the 28’s. That’s the clear choice.

I recently switched from GP5000 28mm to 32mm and the comfort difference was huge. Riding a Canyon Ultimate.

I’ll only use the 28mm tires when I know the route is smooth.

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Same. GP5K All Season TR in 32c on Roval Rapide CLX. Really happy with the float over crappy roads on a Tarmac. Tried a lot of tires. These are keepers.

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Definitely don’t go with the 28’s. All of the math is going to boil down to a watt or two. Maybe 5 watts. But over the course of a long Gran Fondo type event, the ability to continue putting down the power in the third, fifth, and seventh hours is worth AT LEAST 15-20 watts, maybe more, if you’re not getting beat up by the vibration. Take the comfort and the suspension benefits of the larger tyre, and you’ll be faster overall.

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Ok. Maybe for you? I’m an ultra cyclist and my experience (and the numbers, as I laid out) definitely point to the 28’s. But, look, it’s possible that one of the reasons I had so much success at ultra cycling is that I’m just more durable than most folks on the bike. Maybe an extra 2mm of tire width really does make that much of a difference for you over a moderate distance. I’m not going to try to invalidate your experience. For me definitely not.

So, let’s tally this us:

rolling resistance: no measurable difference. Maybe 150mW advantage to the 30s.
weight: 60g advantage to 28s
aerodynamics: Enve doesn’t recommend the 30’s. At higher yaw angles, 2-4 watts

I re-iterate, go with the 28’s. No question about it. Or maybe if you just don’t have the endurance to ride a 2mm narrower tire & you should buy a different set of wheels. ;-D For sure, there are wheels that work well with 30mm tires. The FLO Gravel wheels, I know for sure, are very fast with a 30mm or 32mm tire mounted. I’m sure there are others.

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I’d say you really are likely to be “more durable” than most, which would correlate well to you having been successful in these disciplines. And now, given the additional detail you’ve provided, I can easily see why you’d prefer the 28’s.

My comments were geared (1) to the OP’s comment about “not sacrificing comfort” and noting that his bike and wheels are not that expensive, hence inferring that he’s not (speed-wise) at the pointy end of the spear, and (2) to the fact that so far everyone has focused on aero resistance and rolling resistance, but not at all on the benefit of a wider tire, at lower pressure, in helping reduce suspension losses on less-than-perfect roads – which, for longer events, most are.

I believe the reduction in suspension losses and the comfort factor still compellingly favor the wider tire. I understand that you disagree, and why, and that your thoughts are entirely reasonable… and that’s why we are here on a discussion forum, enjoying the conversation. :grin:

I’d fully support your recommendation to use different wheels though if he can afford that or make it happen.

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The advantage of wider tires increases on real roads due to better rolling resistance/traction, especially on bad roads. (Keep in mind that BRR data is valid for ordinal purposes. It shows whether A has better rr B but those numbers can’t be applied on the road or extrapolated).

It’s hard to quantity the point where the aero penalty is greater than these gains. Anecdotally, I’ve seen more and more experts suggests to go wider over aero or the rule of 105 for speeds and roads typical of grand fondos or gravel.

The rule of 105 is relevant even at relatively low speeds (>13-15mph). However, under certain conditions, these other factors dominate.

In an ideal world, we would first pick tires for the occasion and then choose a set of wheels that satisfy the rule of 105. However, most of us are limited by the wheels we have or can afford.

In modern rims with wide external widths (>28mm), it seems using wider tires can benefit most people despite violating the rule of 105 (up to 32mm labeled width).

I don’t have evidence to back this up. However, I’ve seen that even Josh Poertner in some cases recommends going wider over sticking to the rule of 105. I’m almost sure he has answered this question in the Marginal Gains podcast, probably more than once. I don’t remember the episode.

Don’t quote me on this tho. I’ll just take it as a suggestion that it’s worth considering going wider.

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OP…measure your tires and experiment. Interestingly my GP5K cream sidewall 28’s measure just under 32 while my GP5K black sidewall 30’s measure 30 on the same wheel. I prefer the 28’s. I use Silca’s tire pressure calculator fwiw.

For me 28 vs 32mm means no numb hands (median nerve, carpal tunnel like symptoms) and no need to alternate hands to make the numbness go away

We used to train and race on 19mm tires. Then 21mm, then 23mm, then 25mm, then 28mm, and now? 30-34mm?

Some of this discussion makes it sound like riding on 19mm tires was near humanly impossible! :slight_smile:

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Nope. But riding on wider tires, at lower pressures, with more supple casings, is either as fast or faster, and it’s more comfortable. Hence, resistance to sticking to the old ways…

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We were young and stupid. Never going back. I’d rather ride with no chamois than narrow tires and high pressure.

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Back to OP. I would definitely go with 30s. Lower pressure, more comfort, better traction = more fun = more riding.

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J P Ballard (?) from Swiss Side talked about that rule not being a thing any more when Ronan and he did the pit walk at TdU on the Escape Collective podcast. But I did notice Ronan referenced it (the rule) in his catch up with the Zipp guys recently. Side note, it’s interesting having an actual aero expert on a podcast with a not-actual-but-very-knowledgeable aero guy.

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I have 28mm on my rim brake bike as thats all it can take. I have 30mm on another bike. The difference is massive on the terrible UK roads. I pay a slight aero penalty on my Zipp 303s wheels (zipp say they are aero optimised for 28’s) but the increase in comfort over long rides is more than worth it and probably ofsets some of the watts ive lost as i’m not getting shaken to bits.

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My winter bike is rim brake and with mudguards I’m limited to 25s. Brutal UK roads have been killing me all winter.