25 vs 32 mm fast road tires

Ok…I know that’s a big spread…but bear with me haha.

I’m looking to get some fast (leaning tubeless) road tires for my 23mm internal 50mm deep road wheels I use on my N=1 Lynskey gravel bike. I want to squeeze out a bit more speed, but I’m a bigger rider and there are plenty of potholes around me so I have to keep that in mind.

I can get GP5000 TL in 25mm or 32mm…28mm everything is sold out right now. I’ve never ridden a 25mm (on measured 35mm tires now). I understand that you always need to work on the engine (doing that now with TR!)…but I’m trying to get some reasonable gains where I can.

Comfort needs to be a priority since I have some centuries planned so that makes me think 32mm, but the 25mm will probably be more like 27mm measured so it’s not ridiculously skinny.

Any tips are appreciated. Thanks!

Define bigger. If you’re around 200lbs or less you’ll probably be faster overall on the 25mm at the cost of some comfort. 32 is simply too wide for your rims to be that aerodynamic. 28mm would be best so maybe consider other brands of tubeless

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32 on the Front will likely f‘ with the aero benefit of your deep section wheels.
I ride 28 front and 30 rear, and I am happy man. But that is on a climbing bike.
My aero bikes are equipped with 25c and I can’t complain about comfort.
I’d recommend going 25c first, see how that feels and try getting a 28c on order, that would add a lot of comfort on your rear wheel.

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I ride a lynskey backroad as my primary daily driver and run GP5kTLs in 32 during the season when the dirt is not liquid or white. It feels exactly as fast as my felt on 28 tubed gp5ks but noticeably less bumpy ride on crappy roads. The air volume difference between 28 and 32 is noticeable, 25s would probably feel like i was riding a wooden wheel after so long on bigger tires. I am sure I lose out on aero but on all the small farm roads I ride the energy savings of not getting beat the hell up trumps small aero changes (at least in my mind).

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On a 23mm internal rim, I’d guess that a 25mm tire will measure 28mm or more. I have 25mm GP5000s on 19mm internal rims and they measure around 27mm wide. My rims are 25mm wide external.

I’m 200lbs. I ride the 25s at 80/85psi. They are pretty comfortable. Heck, I used to ride 20mm tires and then when 23mm wide tires came out we all thought it was a comfort ride.

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North of 200lbs and 6’5" … 28mm almost anything has been virtually impossible to find.

what is external width of rim? Which rims do you have?

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I’ve been riding 30c Vittoria Corsa Controls for the past 2 years and have nothing but good things to say about them. I live in SE Michigan where the roads are either gravel or asphalt so bad you wish it was gravel (maybe a slight exaggeration) and they are very comfortable and I’ve been doing fast road rides and crits on them and they don’t feel slow or anything.

I’m 180lbs and I’ve been running them tubeless at ~60psi.

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31mm outer, 23 mm inner I think.

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I have GP5000TL in both 25mm (tri bike) and 32mm (N=1 Ventum GS1 bike). I am a bigger rider (6’3", 215 lb) and the 32mm are drastically more comfortable on crappy potholed roads. Smooth roads it’s near a wash.

According to BRR, the CRR is similar across sizes so the it comes down to aerodynamics. If you are TTing or worried about fast solo efforts, the 25mm will (likely) be more aero. If you are riding in a group and are able to sit in a draft and rotate through, it won’t make that big of a disadvantage IMO.

For reference: 25mm, I run at 85-90 psi on 21mm and they measure out to 28mm. 32mm, I run at 65/60 psi on and they measure out to 33mm. Both are mounted on 21mm internal width rims.

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Hey @FrankTuna…I would go with the 32s. That way if you ever do find yourself on a little gravel you can let that Lynskey unwind. Let fast horses run!

And you’re not giving up as much as you think. Give the last Flo Cycling podcast (on Crr) a listen. He talks some good inside baseball on that podcast…and it’s not too long. In fact their last three podcasts have been outstanding, IMO. Some really good easter eggs in there if you’re listening.

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yup, 31mm external width. If you follow the rule of 105%, then keeping inflated tire width around 29mm (as measured) is better for aerodynamics.

The FAQ on that page states:

I’m also north of 200lbs and have the 32mm external width Aeolus Pro 3V and current tires measure 38mm inflated (35x622 tires). I’m going to try 32c and 30c tires next.

I’m of the same opinion, my Pirelli Cinturato Velo tubeless measure out to 38 and look ridiculous at Wed night worlds. But it doesn’t seem like I’m giving up too much, and they were fantastic on California gravel/dirt roads. For example on a local ~10 minute Strava segment coming back into town with a 10mph tailwind/crosswind assist:

  • Aeolus Pro 3V with 35c Cinturato Velo tires did 10:32 / 24mph / 246W in June 2021
  • Deeper Enve 5.6 with same tires except in 26c did 10:23 / 24.3mph / 256W in April 2020

different bikes with similar geometry, and that segment runs 1.8 miles west, then 1 mile north, and 1.4 miles west and the tailwind was West / Southwest. Different days but similar wind conditions. Not same-same testing but similar times.

For Wed night I definitely want to run with some faster rubber, the Cinturato have incredible puncture resistance and roll faster than Gatorskins, but definitely not the fastest tires. So I’m going to try two race tires in 30 and 32. For everyday riding on crappy roads I’m very happy with larger volume tires.

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I have been very happy with my recent switch to tubeless. I went from 25mm gator skins to ‘Schwalbe One Performance Tire - Tubeless 28mm’. Google them now and you can buy 28mm from back country.

Conti GP5000s in stock in 28mm. Personally I wouldn’t go 32 front and back, but that is me.

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I have 32mm GP5000 (team tube inside) on Bontrager Aeolus 3v (25mm inner and 32mm outer rim width) wheels. The measure about 33mm.

I weigh about 77kg. They are super comfortable due to the ability to run lower pressures. I blow through rough pavement which much less hesitation than my 23mm tires. I also feel like I can descend better/more confidently with them. And I feel more comfortable riding down random gravel/dirt roads I happen upon.

The downside is they weigh more and are less aero. It just depends on your priorities.

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32 mm, no question. Run them at lower pressures and tubeless if you can.

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Currently running GP5000 TL’s - 28mm on the front, 32mm on the back, pretty plush ride. (Although I’m using Hunt Limitless wheels which measure 34mm externally, so still within the rule of 105.)

The rear wheel is in dirty air, so strict aero is less important. So even if your wheels measure out to only 31mm externally, the comfort and smoothness and speed benefits of 32mm rubber on the rear may still make sense. Staying within the rule of 105 for aero is more important on the front wheel.

Even if you can’t get GP5000’s in 28mm, can you get some other brands? iirc Schwalbe Pro One TL’s are pretty close to the Conti’s in terms of performance.

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Same - kind of. Business in the front, party in the back. I run GP 5000 25mm front (measure 26-27mm) and 28mm back on a 28mm rim. But I also have a second wheelset for the gravel bike with 47mm tyres.

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I have almost this exact same setup (I am 6’1" 190). The GP 5000 TLs 32mm on my road/gravel Domane are awesome on the road (I have different wheel setup when riding gravel).

I don’t think I could ever go back to < 32mm on the road it is just so comfortable.

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