FlashBazbo

To simplify this thread, assume that I want tubes. (I know that will be extremely difficult for some of you. I've got tubeless on another bike. I've done tubeless for a long time. But I know I want tubed on this bike for a number of reasons.) I've read all the conflicting articles, reports, etc. about tire width, comfort, and rolling resistance. But they all assume equivalent tire constructions (which don't really exist among different sizes, even of the same brand). And a lot of them assume tubeless tires -- i.e., much lower pressures.

So . . . assuming a mix of glassy smooth roads and rough-ish chipseal, would you go with 25mm or 28mm width? (I'm thinking Conti 5000's, if that matters.) Comfort really isn't as important as speed.

datlas 

How much do you weigh?? If you are not heavy, I would go with 25 but either is reasonable.

hefeweizen

What about riding with a 25 front and a 28 rear?
25 front might be a better aero pkg with your front rim.
28 in the rear should give you a more comfortable ride
and not sacrifice much if any speed.

FlashBazbo

Great idea! I hadn’t thought of mixing sizes. Makes sense, though.

(I weigh 175 lbs.)

bruce19

I can't speak to the 28s but I have run 25s on both my road bikes and it's worked well. I know my Guru couldn't accommodate 28s but maybe my CAAD12 . In season I weigh 187 lbs. (FWIW, I discovered Mavic USTs so I don't do either now.)

datlas 

I think either way will be fine. Don't over-inflate them. You probably are looking at 80-ish PSI if running 25's, 75ish for 28's. Most common mistake is pumping up the "max" on tire. Agree 25F28R is also reasonable.

Stormsedge

I like 28s, but it is definitely frame dependent. I'm 210 and run 70-75f/80-85r.

Rides4Beer

If you can fit them, I love my 28mm GP5Ks with Conti Race tubes, comfortable, fast, and handle great. Mine measure 30mm on 20c rims. Haven't noticed any loss of speed over my previous "aero optimized" setup with 23mm tires. What I have noticed is that I can actually ride faster through rough sections without getting beat up.

Kabuki12

I only have one bike left with 23's and when those tires wear out or I get tired of the fatigue, I will change them to 25's. I have 28's on my Windsor pro and that bike rolls real well , of course that could be due to the Phil Hubs. I like wider tires nowadays comfort is king! I remember thinking that skinny tires were faster and I really don't believe it any more. I do more distance riding now so fatigue = slower , comfort= faster for longer. It does depend on the conditions, bike , and , really important is tire pressure. I was running my tires at 85-90 lbs and now I have backed off to 80 lbs and I feel the difference . I weigh 155.

Cypress

Which wheels are they going on? 25mm GP5K's measure out to damn near 29mm on my HED Ardennes Black wheels (21mm internal width).

FlashBazbo

Of course, one wildcard is what the respective tires will actually measure on 19mm internal rims. Conti's usually measure a couple mm wide. Maybe a 25mm IS a 28mm. (On my BMC's 21mm internal wheels, 25mm tubeless Conti 5000TL's measure a little over 28mm.)

EDIT: Cypress, I guess I was still typing when you posted your reply. Good point.

For reference . . . I'm putting these tires on my OPEN as a pure road situation. Plenty of tire clearance and I've got wider tires for when that's best (all the way up to 47mm). I'm trying to stay 28mm or narrower for this situation.

Cypress

Sounds like you're roughly in the same position I am. I went with 25's because the aero profile with the rim is way smoother. A 23 would probably be even better, but then I'd lose some smoothness over chipseal.

Rides4Beer

Go for the 28s. I did the same thing with my gravel bike, road wheelset with 28s, liked it so much I switched my road bike to 28s, and won't go back. Might be giving up a couple of watts in a wind tunnel, but real world, they're fast, I have no problems on A+ group rides with my 28's that measure at 30mm.

cycledogg

I have never had a problem with 23s, so I'm out.

mstateglfr 

Everything ive read(up to cypress' comment) is that the 5k tires measure out relatively true on rims that are 23ish external(so 17-18ish internal). This is different from the 4k tires that are comically larger than stated on basically any rim width.

Not sure if you have seen these, but consider them for tubes. They are lighter and stronger than butyl or latex tubes. Less rolling resistance right there.
https://www.tubolito.com/en/


https://www.bicyclerollingresistance...000-comparison
So the 28mm tire rolled better than the 25mm tire at all PSI.
A 25mm tire at 100psi has the same rolling resistance as a 28mm tire at 90psi, which is closer to how tires will be ridden(wider tire at lower psi). And a 25mm tire with normalized comfort drop to a 28mm tire has the same rolling resistance.


Given that they are effectively the same rolling resistance for multiple tests, why not go wider for more comfort and use the tubolito tubes to reduce rolling resistance even more?

ThermionicScott 

28mm (actual) is the smallest I run on any bike. Haven't gone tubeless on anything yet.

FlashBazbo

I have seen those advertised, but I don't know anyone who has actually tried them. Have you? What do you think?

big john

They are $35. It would be hard to justify if they flat like other tubes. We have had a lot of goatheads this year, flats on all my bikes.

FlashBazbo

Wow. I didn't see that. At $35, there are a lot of more compelling options.

Cypress

Running a 25 at 100 PSI on a modern wide rim sees a decrease in performance, and it would ride like junk. My HED's claim that 90 PSI is the max for any size tire on their Plus rims. In HED's tests (which jive with the BRR results) a person of my weight (164 lb) has an ideal 25mm tire pressure of 67 psi.

Cypress

I was about to taste the Kool-Aid until I saw the price

mstateglfr 

I havent. Ive thought about it since I almost never flat so in theory there is little risk, but no I havent tried them. Suggested it since you early adopt.

FlashBazbo

I only early adopt when a product appears to make sense. $35 for an inner tube doesn't pass the "makes sense" test.

mstateglfr 

I dont disagree that a 25 at 100 would be firm for many. It also wouldnt be too firm for some, since weight is the factor here and many cyclists in the US weigh more than the average woman.
The reason I listed 25 at 100 is to compare it to 28 at 90 since wider tires are run at lower pressures. I then also included the comfort drop comparison since that measures both tires running at 'proper' psi for the tire size.

mstateglfr 

haha, touche there.

...though I do at times see saving 100 grams and lower rolling resistance being chased on this forum for more cost than $70.