Wider tyres !

[Cugel]

I'm always a bit suspicious of those tests that are done in a lab on some sort of idealised surface, particularly drums of regular surface. These are not like typical road surfaces. Nor are the test-tyres in a bike or otherwise operating in real-world circumstances.

In practice, it seems very difficult to arrange "scientific" tests that emulate real world conditions without interference from several other factors confusing which of them (besides the tyres) are effecting speed or whatever other parameters are used to measure the tyre's efficiency.

Theoretically, large squishy tyre with supple sidewalls, run at an optimum pressure for the weight they bear and surface they roll over can outperform the same tyre in a narrower width with a higher pressure, for a variety of mechanical reasons. In practice I seem to find this - although who knows if it's the tyres or other factors that enable me to roll down hills faster under only gravity, with my squishy 30mm tyres at 60psi, than most of my club mates on their rock 'ard 23mm tyres?

I do know that I can't easily tolerate a long ride on hard narrow tyres whilst I can on soft wider tyres. But that's just me.

Cugel

[robc02]

My ,' tests' have shown 37mm Hypers at 45f 65r on a Salsa Vaya touring bike weighing 12.5kg with 85kg onboard to be remarkably more comfortable than a Thorn Audax MK3 weighing 10.5kg with the same weight on board,on various various 28mm tyres, at around 70f and 100r, and 1mph or less slower on a flatish course with one significant climb of about a mile long in it.The tarmac on that route is mainly average with quite a bit of chip n seal and quite a bit of crapmac.

......I will say that big supple tyres run at optimum pressure for load,feel slower due to less or no high frequency vibration,which IMO many cyclists equate with speed,but the numbers don't lie,the other plus is to be able to descend far quicker on the bigger tyre and to be able to take to gravel at speed with far more confidence with the bike feeling far more planted and predictable despite Hypers being slick.....

I also experience getting on for 1mph difference between 37mm Hypers (40-622) and high quality 28s (Continental GP4000S II) - the Hypers being slower. In my case the Hypers are on a Surly LHT and the GP4000S II on a 531 framed Woodrup, so there are other factors to take into account as well as tyres, but I would say that my Surly is a fairly light build and has an almost identically aggressive riding position as the Woodrup.

So, does circa 1mph constitute a big difference? In a racing (or similar) situation it is disastrous, but, for me, in most other situations, it is neither here nor there.

Comfort is a bit more difficult. On smoothish lanes / B roads I find the GP4000S II just as comfortable as the Hypers - they feel different (or at least the bikes they are on do) but I would rate them both as being comfortable. However, on broken surfaces the Hypers are much better at absorbing the big thumps. I am happy to just ride through bumpy bits that I would try to dodge on narrower tyres.

I don't know what type of Roberts and Surly the OP is talking about, but my Woodrup and LHT might be comparable, and they are very different feeling bikes. There is more than just the tyre difference to consider.

[foxyrider]

I was out on my CX bike today which runs, for me, fat tyres, 28 Gatorskins. I did my ride @ 2kph faster than i've been doing on my steel audax bike with 23 Rubino Pro's on despite the CX being a good kilogram heavier. So wide is faster? (I ride the same roads year round on all my steeds so I can easily make comparisons)

Well not neccesarily, the riding position on the CX is subtely different to the audax, closer to my carbon machine and feels a lot more comfortable than the audax. (gearing is almost identical, 50/34 compact with 10 speed 12-30 cassette although the exact sprockets may vary a little) The 28's at @ 85psi felt pretty much the same as 23's at 100psi, I felt every lump and bump just the same.

No the difference is simply the comfort of the cockpit, the tyres making no real impact. The closer to optimal riding position let's me get more watts out.

[reohn2]

Form the record,all my bikes have the same riding position.