Tyre width question

[the jackel]

I have some LB46 21/28 wheels that I currently run a 25mm pirelli p zero with a tubolito tube. The tyre comes up at 29mm @70psi. Unfortunately this combo is extremely tight at the chainstays.

I read somewhere on here, unfortunately can no longer find it, that some tubeless tyres on similar rims were measuring a lot more true to size. I'm guessing this may because they stretch less?

Anyone know if this true or have direct experience to confirm or refute this thought process?

Thanks

[alcatraz]

It depends on the manufacturer (and sometimes model).

A clincher isn't a closed system. It depends on the rim a lot. That's why it's hard to predict the final width. It's also the reason (I think) the tires aren't called 25mm but 25C (which isn't 25mm).

You can ask around what tire would result in 28mm external width on a 21C rim. People can help you.

Sometimes it's a 25C tire, sometimes a 28C, depending on the manufacturer

And as a little sidenote I want to add that it doesn't matter what width it says on the casing. If a 25C and 28C measure the same real width, they are equivalent. The 28C is not more comfortable etc.

[ghostinthemachine]

Didn't someone start a thread on tire width Vs rim width last year?

[jlok]

I have some LB46 21/28 wheels that I currently run a 25mm pirelli p zero with a tubolito tube. The tyre comes up at 29mm @70psi. Unfortunately this combo is extremely tight at the chainstays.

I read somewhere on here, unfortunately can no longer find it, that some tubeless tyres on similar rims were measuring a lot more true to size. I'm guessing this may because they stretch less?

Anyone know if this true or have direct experience to confirm or refute this thought process?

Thanks

You better look for measured width of different tires in the LB thread.

[Hexsense]

Old Pirelli P-zero Velo are large. Vittoria (current version) is also large. So avoid these.

Small tire club:
Continental GP5000 25c (slightly small)
Schwale Pro One Addix (TLE or non TLE, but must be Addix version) 25c (real small)
Pirelli Pzero Race (TLR or non TLR) 24c and 26c are both small.

[the jackel]

Thanks everyone, appreciate you responses.

The LB thread is so long it felt like a needle in a haystack but just found you can search within a thread. Seems obvious you could do that but never knew until now.

@hexsense - just what I needed. Like my current pirelli so will try and hunt down a 26 to start with. Thank you.

[Aesch]

I changed a pirelli velo old 25c version (which blew up to 29.5mm) for a new p zero race 26 and that goes to 27.5mm after a few weeks and rides. I have the same rim!

[JoO]

Veloflex is also on the narrow side.

[basilic]

That's why it's hard to predict the final width. It's also the reason (I think) the tires aren't called 25mm but 25C (which isn't 25mm).

The C refers to the diameter of the rim, it's not tire size. It's some ancient sysem, pre ETRTO. 700x25C says one hopes for a wheel diameter of 700mm and a tire width of 25mm. It leaves the rim bead seat diameter (622mm) unspecified. ETRTO 25-622 is more accurate, same thing as 700x25C.

[alcatraz]

That's why it's hard to predict the final width. It's also the reason (I think) the tires aren't called 25mm but 25C (which isn't 25mm).

The C refers to the diameter of the rim, it's not tire size. It's some ancient sysem, pre ETRTO. 700x25C says one hopes for a wheel diameter of 700mm and a tire width of 25mm. It leaves the rim bead seat diameter (622mm) unspecified. ETRTO 25-622 is more accurate, same thing as 700x25C.

Cool!

[pmprego]

Kind of reviving the thread to avoid to create a new one.

I'm planning on buying a set of wheels from LB and the decision will also be dependent on which tires I'll use.

Context: my rides are 99% of the times below 30kmh even though I try to ride fast. I tend to put some elevation gain in them (last ride was 1600d+ in a 65km ride) and the "competition" among friends is also when going uphill.

Should I go 26c (most likely some pirelli pzero) or 28c?

The wheel that I'll end up choosing will obey to the 105% rule but I'm trying to understand people's opinion on that trend that is going wider and wider. Basically, will a 28c tire be faster than a 26c tire in the context that I've presented?

What "wins"? Better rr? Lighter option? 26c will be more aero (this one I can say that will actually count for nothing given the type of ride that I do).

[Hexsense]

Both.
26 front and 28 rear.

But for proper analysis, your weight matter too. If you are heavy, then front is also 28.
If you are exceptionally light (<135lbs) then 26 on both front and rear.

[pmprego]

Both.
26 front and 28 rear.

But for proper analysis, your weight matter too. If you are heavy, then front is also 28.
If you are exceptionally light (<135lbs) then 26 on both front and rear.

OK, thanks for the reply. 150 pounds. So I'd say 26f and 28r

[PeytonM]

Mixed feelings on this, I prefer 28's front and rear on most rides especially descending. I notice no negative affects climbing, however most of what I consider climbing is out on rural roads that are predominantly chip seal.

However, I still prefer 25's when racing and for my regular training loop. I find them more willing as the speeds increase particularly over 40kph. The road surface is good quality in the above situations.

So I would decide based on the quality of the roads you ride.