Is the weight of the wheels comparable? Are they the same wheels? I think that’s going to make a much bigger difference than tyres. (Even though 25-32 is a big difference)
It’s the same as the difference between driving a Fiat 500 at 70 mph and a Range Rover at the same speed.
One feels really fast and the other like you’re hardly moving.
Mike
[quote=“dhaines83, post:21, topic:11897, full:true”](Even though 25-32 is a big difference)
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Yeah, you could expect roughly 60% increase in tire volume in moving from 25 to 32mm tires.
I bought my Domane back in November and my first impressions of the tires were they really made for a comfortable ride. Due to winter weather I didnt get to ride the bike outside but maybe once or twice a month since then. I did feel the bike felt a bit more sluggish with the 32mm tires on, but I didnt have any trouble really maintaining previous speeds and I did set some PR’s on days where I pushed the pace. To many variables in that to say it was the tires.
I recently took the 32mm off and put my old 28mm Conti GP 4000s on. I wanted to compare the ride quality overall. The ride is marginally less smooth, but the sluggish feeling is gone so I’ve stuck with the 28 since then. Wasnt enough difference to be bothered to swap them back
With that said here is some data I’ve gathered:
The stock Bontrager Affinity wheels weighed in at 2200g on my scale. Not exactly lite.
The 32mm Bontrager R1 Hard Case Lite tires are reported at like 370g (I cant find the 32 on the website anymore, but even the 28 is 350)
So right away my Gp4000 is ~110g lighter per wheel, or nearly half a pound lighter for the set. Which is more than likely why the bike doesnt feel as sluggish anymore.
When the new GP5000 32mm becomes more available I want to try those. They are reported at 295g. So right in the middle of the two. Add tubeless and I think it will be the best of all worlds. Super comfy ride quality with low rolling resistance.
I’m still deciding on wheels. Cutting from a 2200g wheelset to something like 1600g would be huge I feel. I’ve got my eyes on the Bontrager Aeolus 3 Pro right now.
Also make sure that your wheels aren’t measuring more than you think. I had 28mm Conti 4000S2 on my commuter bike and they measured 30mm on the rim. Bought Schwalbe G-One Speed 30mm and they measured 28mm… But 32mm is probably too wide for a road bike. Endurance or not. I’d go for 28mm they’re great.
The ear-opener in that podcast was that pro cyclists swore that the skinny hard tires they were used to were faster than the softer wider ones – and, as mentioned, because of the frequency of vibration. It took accumulated data to prove that the perception was, within limits, lying to them.
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Bumpity-bump: I didn’t think it was worth a new thread.
New bike came with a pair of 28mm Mavic Yksions, and I don’t like how they feel compared to the 25mm GP4000s I had fitted to the previous bike. To me, they don’t feel as supple during cornering. I ran both at the pressures suggested by Silca’s calculator: ~5.5bar.
I have a spare pair of 28mm GP4000s, but can somebody point me in the direction of a suitable tube for them? It seems that I can only find Conti’s standard ‘Race’ tube in the appropriate size for these wider tyres: the ‘Light’ and ‘Supersonic’ variants are only suitable for 25s… or would they stretch to the job?
They would probably stretch, Schwalbe however do an amazing array of tubes (if available in your country) and a lot in their ‘light’ range too.
I don’t know what valve length you need but have a look at Schwalbe SV-18 tubes if 40mm is long enough.
SV-16 is not a ‘light’ tube but is light in weight and you can get in a 60mm.
SV-17 is a 50mm but heavier 150g sort of spec.
If you need longer valves Specialized do some but the tubes start to get heavier again. Sure Conti did some too but I don’t know the part numbers.
There is no reason you should be running 25mm and 28mm tires at the same pressure. In fact, the whole point of going wider is to run the tires at lower pressure. You may have to press the “calculate” button is the Silca calculator when you re-enter the second set of widths to get it to generate a new pressure recommendation.
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According to some online calculators running 32mm on smooth tarmac costs around 7w for the pair vs 25mm pair and that’s not including the weight penalty of around 100g…so yes it definitely sluggish.
Naw, I ‘need’ 60mm. I’d go for 40mm and pop an extender on, but I can’t find either in stock in the local places. 
@mcalista I thought somebody would pick me up on this. I totally agree, which is why I was a little surprised. Thought I’d be dropping ~10PSI! I guess the old tyres took on a more bulbous shape on the old wheels.
On topic I have been experimenting with pressures in a 28mm Schwalbe One on a 17.5mm internal rim recently - they measure 30.5mm externally on that combo.
At 95F/100R, 80F/85R and 65F/70R they are to the best of my ‘measurements’ equally as fast. That’s 28km/h / 17.4MPH average speeds for the same ‘input’.
Just at 65F/70R they are miles more comfortable and I am sure I could even go lower - whether then speeds would fall I don’t know, plus at higher speeds would the aero impact be more I don’t know either (it’s a shallow rim and ‘speed’ isn’t that important to me when bumming about).
Wider rolls faster at the same pressure, but running wider tires at the same pressure is not ideal. At the recommended pressure, wider tires does not roll faster. So 32mm will probably feel more sluggish because it’s heavier and has more rolling resistance.
Check the section almost at the bottom of this article: Continental Grand Prix 5000 23, 25, 28, 32 mm Comparison
Although their information is interesting they use a roller for testing. The roads around my way are a mix of surfaces - none are anything like a roller, all have lumps and bumps, most have cracks and patches.
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I may have been a bit subtle. I checked myself on Silca (lite version), and to get a 5.5 bar (rear) recommendation on 28mm tires, I had to select a system (bike and rider) weight of 210 lbs. When I re-run this weight with 25mm tires, it recommends 6.55 bar (rear).
I recommend you re-run your numbers on Silca. And then on the road.
Yeah, no worries. Notice it asks for the ‘measured’ width, not what the tyre claims it is: https://cdn.shopify.com/s/files/1/0309/9521/files/Measuring_Width.pdf?v=1583842653
Of course, I may have been a klutz with the old callipers, and it could be a case of PEBCAK
This has been talked about a lot, interesting topic. Look at your actual times and see if they are different. Payson McElveen (US Marathon MTB champ and a good Instagram follow if you are so inclined) recently talked about this in one of his posts, that he felt slower but he was knocking out PRs on non-downhill segments with wider, softer tires.
Running lower pressures is the key though as stated above, check out “tire hysteresis” as applied to real-world bicycle wheels and tires
While measured widths can vary between brands, I’d be surprised if the 25 and 28 (nominal), both had the same measured width.