Idle musing at work so indulge me!

The recieved wisdom is, bigger tread, bigger volume is slower on harder surfaces, Narrower tyre and higher pressures roll better right? As the ground gets rougher, lower pressure an bigger tread rolls and grips better.

So if you were doing on/off road mixed riding/commuting whats the best compromise?

More aggressive tread, higher volume tyre at a higher pressure

or a less aggressive, smaller volume tyre run at a lower pressure?

I’d look at compound too – can have as much affect as width and tread, ime.

Fair point, so softer compund gives more grip but higher rolling resistance right?

There’s lots of t’internet stuff about cx tyres but mostly focussed on riding cx bikes in races which is pretty much exclusively tame off road and limited to 32c.

With all the current excitement about “all roads” bikes like the tripster, arkose etc which take 40c (or biger) tyres and that people are using for “mixed media” rides, it seems like a useful discussion?!

Tubes and soft compound

Received wisdom is wrong (unless you ride on a velodrome)

Have a read of this…

And a read of this….

If you’ve not ate your own head by now then you may this interesting….

And finally………

Thanks soma – some very interesting stuff I’d not seen before.

Wow, thanks, that’s genuinely fascinating!

So in basic terms, tread and suppleness appear to be more important than width and pressure for rolling speed but wider gives more comfort and grip which might allow you to stay off the brakes more!

Interesting links – seconded thanks Soma

So 42mm tyres are no slower on smooth roads than 25mm at moderate speeds and quicker on rougher roads.

Theres evidence for a wide tyred Tripster right there!

Yep!

My charge cx bike gets either 32 clement x’plor mso

Or cheap schwalbe cx comps at 38mm

The schwalbes are definitely smoother and faster off road the rougher it gets, I thought they would be slower on road, I’m not so sure now……. Although I guess the more aggressive tread might affect things

There’s an element of suck it and see tempered by the obvious I think.

My 37c W106’s are noticeably draggier than 35c Race’s or Cyclocross Race contis, and 32c Razes seem even faster. 28c Grand Prix’s are much faster than all though- same route, bike otherwise unchanged.

However, the W106’s are much softer (45a I think?) and need a much lower pressure. The 35’s and 32’s I tend to run similar pressures around 40f/60r off road, 60/80 on. They’re all relatively hard – similar to a Schwalbe ‘performance’ . The Grand Prix’s are the outlier though. Black Chili is awesome stuff. Grippy and fast.

Unscientific, but personally I’m finding stickier knbblies are harder work and proper slicks are a different category. Not entirely unexpected….

And to think i used to punish myself with the belief that i’m gonna go faster on my rigid fat tubed alloy mtb running Hutchinson 25mm slicks pumped up to 120psi, bouncing over every imperfection in the road surface. Bah!…I could’ve saved the discomfort (and hellish sketchy road handling) and fitted some big comfy 40mm slicks at 60 psi whilst being just as slow 😉

Interesting reading for sure and there is no reason to doubt their interpretation of the data as Bicycle Quarterly are rather particular with regard to correct reporting.

I’m running these 35mm Vittoria Voyager Hyper’s on my tripster but i have a hankering to try The Compass Barlow Pass Lightweight in 38mm from Velo Vitality , these are some of the tyres developed by Bicycle Quarterly as in the links above – rather expensive but still less than the various Clements i also use.

I used to run 20mm tubs at 140psi on my TT bike, on not very smooth roads before I saw sense. I presume I must have seen something about the issue of getting bounced around, but to some extent came to the conclusion by myself that what I gained in less energy loss in the tyres was more than lost by energy loss in generating vertical motion. I’m not sure they’ve quite got the reason right for the loss of speed on rough roads though – the suggestion seems to be that it’s energy lost in the rider’s body due to vibration. However even a motorised bike would be slower on rough surfaces, as creating vertical motion loses energy through damping which might have otherwise gone into forwards motion.

More recently I’ve run 110-120psi in those tyres, it looks like that might even be too high (I’ve also got slightly wider tyres now).

I’m not sure they’ve quite got the reason right for the loss of speed on rough roads though – the suggestion seems to be that it’s energy lost in the rider’s body due to vibration.

It’s interesting isn’t it, all that ‘suspension loss’ stuff. I always thought it was more to do with the way the bike and rider get bumped upwards as you mention, that vertical motion wastes energy and momentum far more than the flex of a tyre sidewall, but the suspension losses discussion may be valid too. I don’t know. But light-casing tyres at lower pressures do ride well. They also flat quite easily, if they tyre can deform around things more then perhaps not as easily as the same casing with more pressure. Generally I do like the bigger+softer tyre thing but I’ve not been as blown away by light casing tyres as the BQ articles suggests. There’s a balance between casing stiffness and pressure that is durable and feels smooth / rolls fast whatever the terrain but no amount of smooth ride feel will get me on really light casing tyres off-road. Too thorny/flinty round here and having to be too gentle on the bike is no fun.

Some more interesting information from one of the ‘horses’ mouths ,fat is faster and/or comfier in nearly all circumstances . 🙂

http://www.schwalbetires.com/tech_info/rolling_resistance#why

I’d say that carcass construction is one of the biggest factors.

To be honest, I think the skinny hard tyres are faster idea is from the school of designing things that ‘lookright’. Roadie calipers won’t have helped as wider tyres cause big problems here (thank you whoever for disc brakes for this and many other reasons …). . There is sense behind higher pressures for preventing punctures – snakebite is obvious but Road debris damage is also minimised. As mentioned, too much pressure and you lose all your effort into constant correction although a soft full sus bike with poor platforming will also do this. Obviously pressure and volume are linked, but as high volume tyres have traditionally been ‘bad’ this probably hasn’t drifted universally yet. . Equally, in perfect conditions, skinny hard is fine. As with fat bikes at the other extreme, a tyre isn’t suspension really. It has no damping control, only squish. In limited amounts this is fine but you just need to trundle a Fatty at speed with off road pressures along a tarmac road to feel the unsettling movements as the same tyres that were super awesome minutes ago barrelling down that muddy hill suddenly squirm and squish and generally leave you feeling the rim will be eating gravel any minute.

I’m told 28c offerings used to be universally bad, but honestly I can’t recommend my 28c Grand Prix’s highly enough. Mid volume, mid pressure, awesome compound and sensible money. Seems like a sweet spot to me.

For road, add in the 15% theory (if Soma’s not already done so)

80kg, 75-90psi in 25mm tyres (TLR/UST) = comfort central.

EDIT I see Soma’s articles go beyond the 25% rule.

I’ve skim read them in 15m