Best lightweight inner-tube (presta) for 700x25 tyre?

[mig]

…..New tyres are Conti GP4000 700x25

Wheels are Bontrager Paradigm Comp (tubeless ready) rim brake.

Some tubes of a given weight are that weight because they are thin walled, others because they are narrow and they have to stretch to fit inside the tyre. [Since working hysteresis (for small deflections) varies in different rubber compounds, and varies in the same compound depending how strained it is, this means changes (in a way that I don't fully understand) in the Crr depending on what tube is chosen and how it fits.]

I would only make the decision when I'd seen just how tight the blessed things are on the rims; GP4000 are often a pretty tight fit and so are many tubeless ready rims; it could be a 'bad combination'. If the tyres are very tight this

a) may influence your choice of tube; a narrow tube, that stretches to fit, is most likely to puncture in the first place (and when it does the air may come out faster) but is less likely to pinch during installation.
b) you may conclude that changing a tube by the roadside, with that rim/tyre combination, is going to be a major PITA, or even basically impractical, and (from the POV of punctures on casual rides) you arguably might be (and I can't believe I'm saying this) better off with tubeless, relying on the sealant to deal with small punctures and the 'phone home' approach for bigger ones. [but are the tyres in fact tubeless-compatible...?]
c) if you decide to run tubes and yet don't fancy dealing with a roadside puncture, there are other options such as carrying a small canister of aerosol sealant which might get you out of the poop without a massive struggle.

FWIW I have usually been at pains to be sure that when I'm running lightweight tyres the fit of the tyre on the rim is not too tight, so that punctures don't become a nightmare to deal with. Thus for a long time I was very happy with Mavic Open Pro (now open pro C) rims, thin rim tapes, and some types of Michelin tyres, which I knew to be an easy fit, such that tyre levers were not required in many cases. Conti GP4000 (and its successor GP5000) is a nice tyre in many respects but it is a sufficiently tight fit on most rims that I'd probably avoid it if I didn't want a wrestling match with the tyre every time I punctured. IIRC with GP4000 I need tyre levers even on the easiest rims and with (non tubeless) rims that are a bit tight it soon gets into the 'no thank you' range. Tubeless-compatible rims are often tighter than that, well into the 'sore thumbs when fitting, risk of tube/tyre damage during fitting/removal' zone (along with 'are my tyre levers going to break?').

NB one of the issues with tubeless-compatible rims is the lip on the inside which retains the tyre. You need this to be there so that a tubeless tyre doesn't unseat when it goes flat (which it often will do if it isn't pumped up every week). If the tyre fit is tight enough, folk (even with normal hand strength) can find it very difficult to push the bead past this lip and unseat the tyre.

So bottom line; I'd assess the tyre fit (from your POV, with your priorities in mind) with any old tube and then decide what best to do.

cheers

ahhhh....now....this prompts a question! i happily acquired an "open pro c" thinking that it was an exact match for an old open pro. i'm now not so sure that i can resuse the old spokes in a front wheel with worn thin rim. do you have any experience of using the new edition of this 'classic?'

[Manc33]

I found that lightweight (Schwalbe) ones need pumping up far more often than normal (Schwalbe) ones. Pumping up tyres every 3 or 4 days is absurd. With the "heavy" ones (about 125g each as opposed to 80g each) they stay pumped up for three or four times that long. I am talking about 90 PSI+.

[Brucey]

AFAIK the Open Pro C rim is the same extrusion, same eyelets, same everything as before, the only difference is.... the sticker....? It is described as such too. But that said, I have not had one in my hands and built with it as yet.

cheers

[Debs]

I've just placed an order for a few of these:



700c 18-25c

The presta valves are 40mm - which should be just about long enough

[Cyril Haearn]

Who'd a thunk it? For years we've been chasing the holy grail of least rotational weight as we've been led to believe it has the biggest effect overall... I chase low (least) weight all over my light bikes be it me, the frame, the components or wheelsets.

Marginal gains maybe but gains nonetheless.

Placebo, marginal gains, if one believes it is lighter..
If I can save 100 grams rotating weight OR 100 grams non-rotating weight, which should I choose?

[boblo]

Sooooo... The hiararchy has always been: aero, rotating weight then weight but starting with a 'light bike' (if that makes sense?). No point mythering about aero on something that weighs 20kg...

There might be a placebo effect with weight but at least reduction can be measured empirically by us. Aero is a bit of a dark art but the effects are compelling nonetheless.

Now we're told rotating mass is yesterday news... I dunno, given a choice, I'd ride a light aero bike with light wheels over a heavier bike any day - placebo or not.

[thatsnotmyname]

If I can save 100 grams rotating weight OR 100 grams non-rotating weight, which should I choose?

The point is - outside of a few milliseconds on initial acceleration, it makes no difference.

Now we're told rotating mass is yesterday news... I dunno, given a choice, I'd ride a light aero bike with light wheels over a heavier bike any day - placebo or not.

Newtonian physics dates back to the 1600s, so none of this should come as a shock to anyone, really - the physics has not changed. Also, 'light wheels' and 'rotating weight' are not the same thing. By all means have light wheels, but wheels are made up of hubs, spokes and rims and the point being made is that it doesn't really matter where the weight is saved.

[Samuel D]

I came across a typically pithy and imaginative Jobst Brandt post about rotating mass while looking for something else. His prediction in the second-last sentence has held true for 20 years and counting.

[Brucey]

as I have already mentioned upthread, a heavy bike with light wheels will always feel nicer to ride than the same weight bike with heavy wheels because the wheel weight is (provided the frame has any resilience) effectively unsprung weight. The bike with the light wheels will probably roll faster overall; on imperfect surfaces, with the right tyres/frame flex, comfort = speed.

However if all your 'suspension' is in fat tyres, and the frame/fork are rigid (eg steel fork for disc brakes), wheel weight per is much less important, in terms of (real) rolling resistance; it is no longer 'unsprung weight' in the same way. But if you want your bike to ride well and roll easy, you have a choice of only a few tyres.

My idea of utter misery is to ride a bike with rigid frameset (e.g. steel with disc brakes) and puncture proof tyres. If you want any degree of comfort you have to run the tyres so soft it is like pedalling in treacle. By contrast even the same tyres can feel OK (at higher, less inherently draggy pressures) on a suitably springy frame.

cheers