Cycling UK Forum

I am soon to change the tyres on my summer bike, but it's a bit of a jungle out there for inner-tube choice!

New tyres are Conti GP4000 700x25

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

I don't use anything too light because of the risk of puncture during change-over, so use Vittoria Ultra-Lite or Continental Light, both of which seem to be about the same thickness.

You quickly go off very light inner tubes if you keep puncturing them during fitting.

As above. You can go lighter, I fit latex tubes on my TT bike, but I wouldn’t use them on a ‘summer’ bike.

Hi

New tyres are Conti GP4000 700x25

What was the outcome with the GP5000, or are these on another bike?
Regards
tim-b

Hi
And in answer to the quiz...
The GP 4000 is a comparatively chunky tyre, a great all-rounder and if you want to save weight then I'd start with my choice of tyre.
In general latex is more supple and has less rolling resistance but they don't maintain air pressure as well as butyl, so with GP4000 I'd go with butyl
Regards
tim-b

You are worried about inner tubes with those tyres?

How may one avoid the risk of p****ing tubes when fitting?
..
I hardly know nor care what tubes I have

Not sure the wrong tyre is being discussed up there ^... Conti's GP4000 was top of their lightweight wired on (clincher - <sigh>) tree until the GP5000 came along. Low ~200g. Worth putting something light in to maximise gains...

I use Conti Supersonic's in that sort of tyre (Conti's or Schwalbe's equivalent) as I'm not keen on constantly pumping up latex though I appreciate the potential decrease in RRR and improvement in ride quality. Avoid pinching by using your prehensile thumbs to fit the tyre. More practice = better technique.... or stronger thumbs

Is it really a “GP4000“ or the recently discontinued Grand Prix 4000 S II? The latter is a fast, lightweight tyre on which many people raced until a couple of years ago. Still do, probably. It’s only “chunky” compared to extreme-Crr tyres.

The weight of a tube doesn’t count against the 1000× greater weight of the cyclist. But the weight varies with the tube’s wall thickness, and this has a more significant effect on speed by changing the rolling resistance.

On this basis the Continental Supersonic is probably the fastest butyl tube available, but it’s miserably thin-walled. I had a spate of punctures with these for a variety of weak reasons: wear on folded corners in jersey (once two holes when I needed it – that was a long patching session – and another time when I offered my spare tube to a woman on the roadside), a slightly rough spoke bed, and even a couple of unexplained punctures. So I gave up on them.

Latex tubes are not especially light – not that that matters, as I said – but have significantly lower rolling resistance, similar to moving to the next class of tyre construction. That and their low cost-per-watt-saved make them essential for a bicycle with racing pretensions and tube-type clinchers.

The ~70 g butyl tubes are a reasonable compromise. They don’t match latex for rolling resistance, but they approach the Supersonic and with fewer practical problems. They hold air better than latex, so they’re a good choice for a bicycle you might ride every day (for a long commute, say) or if you have an aversion to inflating two tyres before every ride. I find latex tubes give me that aversion after a while, so I have swapped between the Michelin Air Comp Ultra Light butyl and Air Comp Latex every few months, often with the seasons.

Recently I’ve started to see reports of differences in rolling resistance of tubes of similar weight, something I hadn’t really expected. I suppose this shouldn’t be surprising, because the tube acts like an internal tread, and we all know the tread compound plays a role in rolling resistance.

For butyl, Continental seems to do clearly better than Schwalbe, while Vittoria latex beats Michelin latex by a smaller amount. Presumably this reflects differences in the rubber compound that may also affect air-tightness, tear-resistance, ageing, etc.

Finally, there exists such a thing as an ultra-light latex tube, essentially the sort of tube that would normally belong in a tubular. They are made by Vredestein and weigh about 50 g. Since latex tubes barely contribute to rolling resistance anyway, these are not likely to offer a significant improvement even to racers. Reviewers have described their walls like those of a balloon. These were totally uninteresting to me until I saw the Crr difference between Michelin and Vittoria and remain fairly uninteresting despite their alluring natural-latex tan colour.

Aye it's funny how we zero in on the 20g of inner tube weight saving vs the 80kg of meat sat on the bike which in itself is going to be north of 7kg...

However, this is not really touring bike territory but once you get a yen for weight saving, it's hard not to look at all the opportunities. When I take my road bikes climbing, I usually lose 4-5kg before going to avoid dragging it up the hills with me that's as well as being reasonably focused on kit weight.

Can't say I've ever noticed any difference - actual, imagined or otherwise - between any make or type of inner tube that I've ever used. Notwithstanding latex's propensity to shed a few psi.

I think we can file it under 'what is the best cable crimp?'...

boblo wrote:[…] once you get a yen for weight saving, it's hard not to look at all the opportunities.

All the same, you gain much more from the lower rolling resistance of Supersonic tubes compared to 100 g butyl ones than you do from their weight-saving of 0.1 kg, even when climbing a French Alp.

You can get a feel for this by going to Bike Calculator and leaving the options at default except for changing the Grade to 7 (%). Speed will plummet to 8.64 km/h. At that speed, since rolling resistance is roughly proportional to speed, the AeroCoach data (for 45 km/h) suggests a saving of (8.64 / 45) × 4 W = 0.8 W by going from Continental Race 28 (100 g butyl) to Supersonic (50 g butyl) tubes.

That 0.8 W reduction in rolling resistance can be simulated by adding 0.8 W to the Power field, which increases speed to 8.68 km/h.

Then, to simulate the weight-saving effect instead, put the power back to 150 W and reduce the Bicycle weight field by 0.1 kg (to 8.9 kg in this case). Speed barely moves to 8.65 km/h.

So even with a light rider and a 7% gradient, the lower rolling resistance is worth about 4× more than the lower weight.

Meanwhile, on the flats the weight doesn’t matter at all and the rolling resistance counts more. If you weigh more than Bike Calculator’s default 70 kg, the weight-saving matters less. If you go to latex tubes instead, the weight saving is less and the rolling-resistance benefit is greater.

Moreover, the less power you’re putting out – for instance, because you’re touring all day – the more the rolling resistance matters to your speed (or distance covered or ease of travel depending on how you see things), because proportionally more of your power is being spent to overcome rolling resistance. A powerful racer battles almost pure wind resistance but a tourist does not on common touring tyres.

On these grounds I think most cyclists would do better to choose their tyres and tubes with more concern for rolling resistance. Instead they often worry about weight, electric shifting, or some esoteric concept of stiffness. I have even seen long-distance racers argue for puncture-resistant tyres that give up many minutes with which you could fix multiple punctures.

thatsnotmyname wrote:I think we can file it under 'what is the best cable crimp?'...

That’s the emblematic view.

Debs wrote:…..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

Hi
I'll confess to assuming that "Conti GP4000" is the Grand Prix 4000S II ('cos that's my 3-season tyre ), and I stand by it being comparatively chunky and a great all-rounder and you can save 20g per tyre quite easily
The 4000RS is 15g lighter than the 4000S, which is similar to the weight of a 5000
Confusion unconfused, hopefully
Regards
tim-b

Samuel D wrote:Is it really a “GP4000“ or the recently discontinued Grand Prix 4000 S II?

Thanks for your informative post.

I have a pair of Grand Prix 4000 S II

They're maturing nicely in my spare parts cupboard, bought them over a year ago to replace the Bontrager R3 that came with the bike; 2017 Trek Silque SLR 6 (rim brake). The R3 tyres have done really well, and seem to be lasting for ever, but after 3 years and almost 5k miles they ought to be replaced very soon in the interest of dependability.

The inner-tubes i'm currently using are Conti Race, but these weigh in at a hefty 145 gm each!
Has to be something out there better than that, and it doesn't need to be ultra lightweight.

I've also noticed that Tour and Race Conti inner-tubes are subject to quality control issues, a good batch tube is cheap & cheerful and reliable for years, but a bad batch will split easy, or the valve seat rubber splits - usually when pumping up the tyre just before a ride.

My bets are on a good lightweight Butyl inner-tube weighing in at around 80g.
That would equate to a weight saving of 65g per wheel, and 130 gram of revolving weight saved will be noticed on a brisk hilly ride.
I weight in at 64 kilo, with a healthy BMI of 21, so don't need to worry about my body weight