Assuming a linear comparison is the best case scenario for the tubs. Any non linearity will make the weight difference even less significant.

Whereas the force required to accelerate weight at the rim isn’t so you can’t compare linearly.

So don’t compare linearly then. I was trying to simplify things – I can do proper maths if you want, but it won’t come out any more in favour of the tubs.

Is the point you’re making that weight at the rim counts double for acceleration? So for all those times when you have more than 500W spare going into acceleration advantage to the tubs?

I think my issue (sorry if I came across blunt, actually genuinely interested in this stuff) is that rolling resistance is key on mega flat TTs/velodromes with only one acceleration off the start but most riding isn’t like that. It feels like I’d rather gain (haven’t done the maths either) <3W rolling resistance but be able to accelerate or climb more easily. 2.8W is nothing, 200g rotating weight feels like a lot.

Can Rocco confirm the type of rider he is and whether he will benefit from all that applied mathematics up there or is he the typical biffer on a bike that could lose 20kg and not even notice but it’s the wheels that are slowing him down?

Which is where the numbers come in. It might “feel” like 200g rotating weight is a lot, but in reality in a proper double blind test the only way any rider would be able to tell the difference is because of the way the bike handles and/or responds to sideways movements. There is zero chance of you being able to detect the difference it makes in acceleration.

Also in reality for riding you have that 2.8W loss all the time (actually a varying amount, IIRC rolling resistance is directly proportional to speed and that 2.8W will probably be at ~20mph, but I CBA checking as it’s not going to make any difference to the conclusion). The maths tells you that the extra weight will only cost you that much for a tiny, tiny fraction of your ride even if you have a very high power output.

So that 2.8W might seem like nothing, but the cost of the extra weight is even more nothing.

The maths tells you that the extra weight will only cost you that much for a tiny, tiny fraction of your ride even if you have a very high power output.

But not in a crit where you are accelerating or braking the whole time or when riding up a hill. Like you say, the numbers are the way to see.

Whilst I wouldn’t countenance riding my Corsa Speeds for general road use (think tyres of 30 years ago robustness), there is no doubt that they are significantly faster than other tyres I’ve tried. (it’s 2.8 W per wheel remember) so six free watts over the tubular variety is not to be sniffed at, if you only have 250 to play with.

the speed difference will be 1.02^1/3 = 1.0066 or 24 seconds for a one hour 25. If you are national level, assume 400 watts and the effect is 1.004 or 12 seconds for a 47 minute 25. Championships have been closer than this.

Rolling resistance is everything on a flat TT course. Aero trumps weight at 30 mph by some margin. Otherwise we’d all be riding mavic reflex not disc wheels 😉

2.8W per pair at 120psi according to the tests.

And I don’t disagree with the logic on a flat TT but like I said most riding or even racing isn’t a flat solo TT. There’s a reason why Team Sky riders have superlight tubular climbing wheels for the key mountain stages yet Tony Martin and a few others have used Turbo Cotton clinchers with latex tubes on their flat TT wheels.

Except the proportion of your power going into acceleration is still far less than you think – I doubt there’s any point in such a race where the extra power required to accelerate the wheels is greater than the power lost due to RR.

or when riding up a hill. Like you say, the numbers are the way to see.

In which case we’re back to only 0.25% difference, hence 1000W power output required before the advantage swings to the tubs.

It’s quite possible they’re using hard track glue, hence getting rid of those extra power losses – remember they get a spare wheel if they puncture and the mechanics get to change the tub later. Though unlike mere mortals their power outputs are also high enough that the weight difference becomes more significant.

first day on clinchers in 2 months today – punctured – twice
🙄

How long did they take to fix?

11mins 37 and 11 mins 45

I am off my game big time

sweet, can you change a tub in the same time?

My friend works in a bike shop and is putting a new tub on my wheel for me. He just send me a photo of his finger with a hole in it from that job. I am very pleased not to be doing this job.

stevious – Member

My friend works in a bike shop and is putting a new tub on my wheel for me. He just send me a photo of his finger with a hole in it from that job. I am very pleased not to be doing this job.
Is it a cyclocross wheel?
Gluing cross tubs is a bit of a ritual alright. Taping tubs up for the road, though, is just trivially easy. Takes 5 mins if you’re being careful. Hope he’s not charging by the hour…

He’s doing it for me as a favour and I think it’s from removing the old glue. I bought the wheels second hand with tyres already on and the previous owner was a bit keen with the adhesive I think.

That is a ballache of a job right enough. If you can bodge some way of immersing the whole rim surface in white spirit then an hour’s soak would have them brand spanking. Never found a particularly good way of managing this myself, and always end up doing it bit by bit.

2.8W per pair at 120psi according to the tests.

It’s per wheel. They don’t mention doubling losses anywhere on the test protocol.

MTB-Idle – Member
sweet, can you change a tub in the same time?

far quicker

but only once per ride 😕

No one’s mentioned you can run flat on a tubular whereas you’d probably trash a carbon clincher rim doing the same – the main reason why pros stick with them. Carbon tubular rims are lighter and stronger. I’d only used tubs on carbon wheels for road racing, particularly due to potholes causing impact punctures on clinchers and still managed to break a few rims – I could generally get away with a pair of Vittoria CX for a season of racing. Tubulars still rule the roost in CX as you can’t run clinchers at lower pressures where grip is king. The issue now is the number of ‘leisure’ cyclists who ride lightweight carbon wheels and expect them to have the durability of a regular wheel.

It’s per wheel.

From the link you sent, 9.1-7.7 = 1.4w per wheel. so 2.8/pair.

Fair enough. Except I’m running mine at 90 PSI not 120. Interpolation makes that 1.75/wheel or 3.5 Watts. In one TT I ended up running the front one at 30 PSI for 15 miles after a puncture and still managed a PB. A tub would have seen me a lot slower 😉 . I also vastly prefer alloy rims to carbon, although my wheels are also available in tubular with alloy. The weight difference for alloy is more than made up for by the confidence in braking for those sharp 90 degree corners.

And in my last road race my team mate punctured her Corsa tub after about 20 km. She had to borrow a bike as there was no neutral service. She had to borrow a wheel the following day too because the Pit Stop would seat enough to ride but not hold any decent pressure she didn’t have any tub tape.

Latex inner tubes and open tubulars every time for me on the road. Tubeless for TTs. Until Vittoria update their Corsa G+ to tubeless. THen tubeless for everything.