choddo

I think you guys need to watch Alex Howes here talking about all these 25mm tyres he ran at 100psi last year

PeteHski

Nice one 😂
Obviously took DM’s sage advice.

FL_Gator

Well.. the Tyre Glider was no match for the GP5000s, had to revert back to my Schwalbe tri levers, it just couldn’t get the Contis on.
30/32 mounted now though, hoping to ride Sunday.

choddo

Did you spray the last area of the rim with mucoff or similar to let the glider slide more easily? Hold the wheel and tyre in your left (if right handed) hand at the end of the unfitted section, with the wheel braced against your body so that portion of the tyre can’t progress round the rim as you chase it :-) and then push the glider with the heel of your right thumb, fingers pulling on a spoke. I do it here (this tyre was easier than a gp5000 so I didn’t need to pull on a spoke) from about 2 minutes.

FL_Gator

No, I didn’t try that, I was trying to simulate how it would be if I was changing a flat out on the trail. I tried and tried and could get the glider under the edge of the old tire to get it off. Struggled with sliding the new one on without any spray but wouldn’t have spray on the trail.
The video is helpful, I have a couple more tires to do so I might try it with your tips. Thanks!

choddo

Oh don’t use it to get them off. It’s fairly crap at that. Park Tool levers are way better. It’s brilliant at getting them back on though. And outdoors I rely on Dynaplugs and never take the tyre off but if it came to it, a bit of spit might suffice

FL_Gator

Ok, got a good test in. Personal feel, they are super super smooth on a typical cracked pavement flat Florida bike trail… and also feel very fast. However to check my confirmation bias I have two nearly identical test runs to compare.

It’s a 12.5 mile flat loop through the woods that is very circular. 2 loops 25 miles total. Same kit, helmet, socks, shoes, bottles, etc.. all identical. Temp within 5deg. Tried to keep similar body position, no drafting. All tires are GP5Ks.

RUN 1, 28mm front and back 74/76 psi:
25 miles
Avg 20.2mph
Avg 232w

RUN 2, 30mm front, 32mm back 70/65psi:
25 miles
Avg 20.9mph
Avg 208w

The only real variable here was wind. Both days had moderate wind, however since it is a circular loop I feel like you get equal benefit and penalty as you go around the loop that should essentially offset. Thoughts?

terrymorse 

Wind doesn't work that way. On a loop or out-and-back course, higher winds produce higher penalty.

tomato coupe

It might seem counterintuitive, but even with a perfectly circular course in a constant wind, the wind will hurt you more on the upwind segments than it helps on the downwind, and it will slow you down on more than half the course. (The double whammy is due to the non-linearity of aerodynamic drag.)

genejockey 

You never get back from a tailwind what you lose to a headwind.

genejockey 

It's a start! Certainly it looks like there's no penalty. I'd suggest just riding the 30/32s for a few weeks on the roads you have been riding and see what you see.

I can tell you that I noticed the difference between the 32mm Corsas and 28mm GP5Ks in a single ride. The fact that you have power numbers, too, helps a lot. I don't. All I have is RPE.

terrymorse 

It's just one example of the laws of thermodynamics:

1. You can't win.
2. You can't break even.
3. You can't get out of the game.

FL_Gator

All the wind comments make sense, no real way to mitigate that in real world riding comparisons. So I’ll just ride a few more of my normal courses and compare as I go. Definitely didn’t seem to be any slower today at least.

Mtracer

The majority of the difference in power you are seeing cannot be from the rolling resistance of the tires. At those speeds, the entire rolling resistance would be on the order of 30 W. So, the difference you would get from tire width would obviously be a fraction of that.

As already mentioned, wind doesn't cancel going in a circle or an out and back.

The reality is it is very, very difficult to make these types of comparisons in the wild. Especially with single runs at different times under what will always be different conditions to some degree. It takes many runs to be able to make statistically significant comparisons. Though I don't fault you for trying.

I've tried to compare performance at different speeds, in an effort to extract CdA and Crr from data. Even though I did multiple runs with one immediately after another, very flat course, and no obvious wind, it was difficult to to come up with anything that appeared accurate. It's simply a very tough problem. Crr (rolling resistance) itself is pretty easy, it's just that aero drag dominates at all but the slowest speed. And aero drag is always significant. Also, aero losses are super sensitive and complex. Air density has a direct relationship to aero losses and varies day to day and throughout the day. Even humidity is a factor.

In the end, there is enough data and information out there to support that wider tires, in the ranges we are considering, do not hurt significantly under controlled conditions, and likely have a net benefit in the real world with varying surfaces conditions we find on our rides. Then factor in the much improved comfort and wider tires for the win.

I think what might prove more useful over time is ride the wider tires, collect ride data, and then compare that to the, presumably, many rides you did on the narrower tires. A generally faster average speed for similar power may emerge from the data. Or if nothing else, you'll prove it didn't hurt to go wider and gain the comfort.

Complicating this is the effects of rougher roads and selecting tire pressures. The ones you used would be high for me. And I'm not a light person at 190-195 lbs. I'm running close to 60 PSI on 28 mm GP 5000 (measure 30 mm). It's slightly lower than the Silca calculator recommends for poor pavement. But the penalty for running a lower than optimal pressure is very small, while the penalty for running too high a pressure is much higher. I.E., better to optimize for the worst surface condition you spend any significant time on and err on the side of too low rather than too high a pressure.

Nice thing is, we get more comfort at these lower pressures, and unless you hit a lot of potholes, there's just little downside to the wider tires and lower pressures and they may actually be faster.

tomato coupe

Yep.

PeteHski

As others have said, the speed difference will be mostly from wind variation. But the smoother ride is certainly valid and I doubt there would be any speed penalty. You could probably run lower pressures too without any penalty. Now you need to try some 23 mm tyres at 110 psi!

RChung

Yep.

Not always, though it depends on what you consider "many." If you do it right and you're lucky, maybe three runs of a couple of minutes each, for each tire combo. But it's easier to do indoors on rollers in controlled conditions, so I completely understand that people do it that way. (It's even easier than that to forego testing and instead read bicyclerollingresistance.com)

FL_Gator

Fun thing I just validated.. my 2010 Specialized Roubaix (stock 23mm tires) was able to accept the 28mm tires I just took off of my main bike. Specialized told me a few years ago that only 26mm would fit that old frame but the 28s with some deep section carbon wheels looks and fits great!

genejockey 

My Battaglin (early 90s frame with 2006 Chorus) barely fits 25s, but that's mostly because the Velocity Fusion rims have 13.9mm internal width so I can't really open up the brakes wide enough.