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Switching from 25mm to 28mm tires?

Road Cycling “It is by riding a bicycle that you learn the contours of a country best, since you have to sweat up the hills and coast down them. Thus you remember them as they actually are, while in a motor car only a high hill impresses you, and you have no such accurate remembrance of country you have driven through as you gain by riding a bicycle.” -- Ernest Hemingway

Switching from 25mm to 28mm tires?

Old 04-16-17, 07:37 PM
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12strings
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Switching from 25mm to 28mm tires?

Hey, has anybody switched from 25's to 28's (of a same or similar quality/type of tire)...and noticed any speed loss?

I'd like the extra grip and cushion on chip seal and other bad roads, but also have a lot of good roads too...our group rides take us through both.

I'm thinking of both flat pacelines, and climbing...will doing this slow me down?
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Old 04-16-17, 07:40 PM
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Not materially, if at all. On some surfaces it could be faster.

The only drawbacks to wider tires are higher weight and slightly higher wind drag. OTOH, at the right pressure a wider tire actually has lower rolling drag than a narrower tire (all other things being equal).
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Old 04-16-17, 10:02 PM
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Continental Grand Prix 4000S II 23 25 28 mm Comparison

“One accurate measurement is worth a thousand expert opinions.” - Adm Grace Murray Hopper - USN
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Old 04-16-17, 10:25 PM
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If you're currently running aero rims that are specifically made to work with a 25mm tire, the 28mm could break up the shape and cause some performance loss.

Otherwise, shouldn't really matter.
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Old 04-16-17, 11:15 PM
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B. Carfree
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Originally Posted by gl98115 View Post
Continental Grand Prix 4000S II 23 25 28 mm Comparison

“One accurate measurement is worth a thousand expert opinions.” - Adm Grace Murray Hopper - USN
As I understand the issue, that test isn't measuring what it needs to measure. The primary energy loss we call rolling resistance is apparently due to vibrating the body on the bike, so isolating the tire isn't the best way to look at rolling resistance.

Personally, I have experienced what appear to be large decreases in rolling resistance by going to wider tires, if speeds on slight descents is any indication. Perhaps this is less of an issue for people with less body mass.
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Old 04-17-17, 01:40 AM
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I have been switching between 23, 25 and 28mm tires for several years, and using a power meter, and have been analyzing my numbers for all that time. I can not see the slightest evidence for any speed loss caused by wider tires, and I run my 28mm tires at 70 psi which makes them much more comfortable, but it probably depends on the surface you ride on. If you ride on a perfectly smooth indoor track, then there could be a case for narrower tires with higher pressure, but in reality most tarmac is so rough that wider tires do a lot to reduce rolling resistance.
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Old 04-17-17, 06:16 AM
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It depends. As with most bicycle things these days, the gains/losses are miniscule and not measurable by 99% of cyclists. Another variable can more than eliminate the rolling resistance benefits of wider tires. Depending on who is selling what, the rolling resistance gains of a wider tire either overwhelm the additional aero drag or are overwhelmed by it. It depends on pressures. It depends on road surface. It probably depends on wind direction and how heavily the tires are loaded.


I'm not denying the potential benefits of a wider tire -- for three years, I held a road Strava segment KOM where I was riding 38mm tires at 55 psi! I'm just saying that there is little, if any, way to know for sure what the NET impact will be. The gains/losses are so very small that it almost doesn't pay to think about.


But if your primary objective is added comfort . . . go with the wider tire at a lower pressure. Comfort is something you can sense. (And who cares if it makes you 0.3 mph slower?)
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Old 04-17-17, 06:39 AM
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If you can run 'em, try em. I'm running 30c tires - they feel neither slower nor more sluggish than 23/25c tires I've used in the past (though, in fairness, this is also on a new wheelset, lighter/stiffer than I've owned before, and tubeless, so there's multiple factors), but they definitely feel better and faster on choppy sections of pavement.
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Old 04-17-17, 07:48 AM
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try them & see how you like them. what's the worst that can happen?
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Old 04-17-17, 08:07 AM
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Originally Posted by rumrunn6 View Post
try them & see how you like them. What's the worst that can happen?
+1

My buddy rides 23s at 120 psi. I ride 25s at 75/80 psi; who do you think is more comfortable? Try the 28s, my bet is you will love them.

Use the following as a guide to tire pressure:
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Old 04-17-17, 08:13 AM
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rm -rf
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Some dual pivot brakes, some road frames, or forks don't have quite enough clearance for 28c tires.

My previous bike barely fit 25c -- I picked up some damp stone dust on a new chip-sealed road, and the thin layer stuck to the tires was lightly scraping the fork.
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Old 04-17-17, 08:17 AM
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I've run a wide range of tire widths on my bikes and I keep detailed records of my average speeds. In general, wider tires are slower for me, assuming that they are also heavier. If a wider tire weighs the same or less than a narrower one, then the extra width is just as fast or faster. However, most wider tires are heavier and thus slower. Some tires also have treads or compounds that are slower rolling, and that can also be a factor. In sum, in my experience, weight and rolling resistance are the biggest factors in the speed of tires. On rougher surfaces, a wider tire probably gains some advantages or narrower ones, but the roads are pretty decent where I ride, so it has not been a big factor for me. In my experience, wider tires are not a magic cure for increasing comfort AND speed. There are always trade-offs. I now run wider tires on most of my bikes (28s-35s) for comfort purposes, recognizing that they are also slower than under most conditions than narrow tires would be.
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Old 04-17-17, 11:01 AM
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Originally Posted by B. Carfree View Post
As I understand the issue, that test isn't measuring what it needs to measure. The primary energy loss we call rolling resistance is apparently due to vibrating the body on the bike, so isolating the tire isn't the best way to look at rolling resistance.
High pressure skinny tires are fastest on a smooth velodrome. Low pressure mtn bike tires are fastest on the roughest pave of Paris-Roubaix. And it's a continuum in between. The testing mentioned doesn't isolate the tire as the wheel is loaded with a fixed load and rolled over a non-smooth surface.
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Old 04-17-17, 01:13 PM
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Wider tires are now becoming mainstream.

My commuter bike sports 35c tires and my gravel road bike runs on 42c tires.

Its just the comfort factor. Originally, people could ride tires as skinny as 18c but the road norm became 23c.

In the old days, the reason for skinny tires was what caliper brakes allowed between the fork and rear stays.

With modern disc brakes, that not an issue.
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Old 04-17-17, 02:04 PM
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12strings
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Thanks for the replies...I may just try the 28s next time I need them. My bike has long reach calipers, and I already run a second set of wheels with 30mm cyclic Ross tires on occasion, so clearance is there.
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Old 04-17-17, 05:00 PM
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I squeezed some 28mm Panaracer Gravel King ties onto my bike for a road race I was doing that had 10-12 miles of dirt and gravel. I'm not sure having the Conti 2k's on there would have made much of a speed difference. But I was very happy for the extra bit of width and tread pattern for a little extra confidence in the mud and snow. I left those same tires on for my crit race last Tuesday. Perhaps switching over will net some difference, imperceptible to my clod head, but it's more about the engine. As always.
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Old 04-17-17, 06:18 PM
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I run Specialized Turbo Cotton 26. Don't need any more, don't want any less.
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Old 04-17-17, 06:26 PM
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Keep in mind that the tire essentially forms a circle when inflated. While for many frames, width at the rear chain stays is the limiting factor, on my 2013 Specialized Secteur (Roubaix geometry) that I have 28 mm Gatorskins mounted on, the limiting factor is the frame bridge to which the rear caliper is attached. Thus, tire height and not width is the limiting factor for that frame, I have enough clearance for at least 32's everywhere except there. 32's would be too tall.

To the OP: I haven't noticed any speed difference between 23, 25, and 28 mm tires on my road bikes. Of course, the 28 has a smoother ride.
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Old 04-18-17, 04:24 AM
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Anecdotally, going from 26s to 28s upped my smiles per mile by at least 0.6. I noticed no decrease in speed, and my 2011 on 25s seems less zippy than my 2017 on 28s. That said, however, the 2017 has a fresher zip bearing, whereas the zippiness of the 2011 has started to leak a little.
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