Please take this thread with a grain of salt as it's going on 5 years old and the predominant theory has changed dramatically in that time.

You won't see many people on 23s anymore unless they're on old wheels or the frame won't fit anything larger. I believe most on this forum are running 28s or 25s (in that order) with outliers running 23 or smaller, or larger than 28.

The "best" tire width depends on your wheels, your frame, and IMO the course. That said it seems like the prevailing wisdom is that if your frame can support 28s, go with 28s unless you have a good reason not to.

I asked because of the many people here advertising that they use 23s on their HED Jet+ even though the change has been to go to 25s to 28s. I am riding on rim brake Trek Speed Concept and am pretty sure that the rear won't allow a 28. They front might, but doesn't the 105 rule come into play here?

If the time is negligible, I am definitely staying on the 25 front. I honestly feel like the front on a 28 would be too wide and less aero.

I did a lot of digging into this when I recently bought a pair of Jet 9+ wheels. The delta between a 23mm front and 25mm front depends on a few factors:

- actual mounted tire width, as “25mm” labeled tires have a large variation in actual mounted width, and narrower ones (like gp5000 ST R or TdF TT) will have less drag than a wider “25mm”.. Air pressure also changes width by about .3mm per 10 psi.

- crosswinds, where the delta between the front 23 and 25 on HED Jet+ is several times bigger above 5 degrees yaw, compared with less than 5 degrees

- which depth Jet+. I haven’t found aero data specifically on this but I expect that the 9+ has less delta between 23/25 than the Jet 6+. The reason being that the 9+ bulges out to ~29mm max while the 6+ is only about 27mm (HED gives bigger values but this is what I’ve measured across several wheels). The 4+ is closer to 26mm. So the 9+ has the extra width to recapture separated flow from a wider tire, but the 6+ and 4+ do not

- aero features of a tire… again I don’t have data behind this but I expect that 25mm tires with aero features like gp5000 and Pro One TT will act like slightly smaller tires, due to their ability to bend the air around them a little better.

With all that said, as best I can tell from gathering aero data on Jet+ posted over the years, we’re talking about differences of 1-3 watts at mortal speeds around 22mph.

One resource is Thomas Gerlach’s aero data on Jet 6+ with different tires. Note that this is “wheel only”:

https://www.thomasgerlach.com/...corsa-speed.html?m=1

Littlefoot - What did you end up using in the front?

Anyone,

I last really raced before covid and wake up now and find everything is Disc brakes and wide a$$ tires. I'm debating 23mm and 25mm (Conti or Corsa tires) on my HED JET 6+ Front wheel. Does Rolling Resistance trump aero? I last raced a 22mm on it due to HEDs recommendation from a long time ago. I'm definitely running a 25mm on a disc in the back.

Hi there, I can’t give you any recommendation on what tire/type/size/combo to use, as it is an extremely personal choice. However - I have a few sets of HED Jet+ wheels (21mm internal rim width) here, with different tires mounted, and did a quick measurement of tire width (all are 25mm tires, inflated to 80psi, all with tubes, 2xTPU, 1xButyl). Might help you make a decision.

Tires:
Continental GP 5000 S TR - Measured width: 26.5mm
Schwalbe Pro One Addix TLE - Measured width: 27.1mm
Continental GP 5000 (Classic tube type) - Measured width: 27.2mm

Hope that helps!

David

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I love rim brake bikes!

Here's a good site to compare rolling resistance and puncture probability. I have no idea how accurate their data are, but their methodology seems pretty good.


https://www.bicyclerollingresistance.com/