Why is Tubeless better.

[patches]

An analogy for those poor folk who continue to labour under the belief that thinner, harder tyres mean less rolling resistance offroad:

 

I drive my 4x4 to the beach to launch my boat. If I try drive onto the beach with fully pumped up tyres, I go straight up to my axles and that's it. Doesn't matter the fact that she's a beast and eats mountains for breakfast. Even if I shed the boat, or the fact that I've got a unichip installed, or huge torque, or the world's most powerful engine, my car is not going another cm. Why? Because of the extreme rolling resistance that my hard tyres have in the sand.

 

But if I drop my tyres to 1.3 bar - hey presto. I sail onto the beach, towing a 1 tonne ski boat with all gear on board and 3 buddies hitching a ride. Why? Because I now have minimal rolling resistance.

 

But then when I am leaving the beach and get back to the tar, I have to pump up my tyres again to the proper high pressure. Why? Because low pressure tyres on hard tar = very high rolling resistance (and increased chance of the tyre coming off the rim).

 

From personal experience, I can tell you (because I actually keep detailed stats of my training and rides) that when I went from high pressure thinner tubed tyres to low pressure wide (2.25) tyres, my ave. speed increased on average offroad by bout 2km/h. Now over a 45km course, that's almost 12 minutes faster.

 

Edit: corrected poor maths

 

I think you have rolling resistance confused with traction and load distribution.

[arendoog]

Although I do agree there are many pros about going tubeless, I was recently on a group ride and one of the guys got a rather bad puncture on a tubeless tire. It literally took them about half an hour to fix it after several puncture plugs didn't do the trick and slim had sprayed everywhere.

Thats why you carry a spare tube if the hole is too big

[tombeej]

I think you have rolling resistance confused with traction and load distribution.

 

 

I agree wider tyres certainly do help to improve grip (traction) in most surfaces, but plays no role in sand. It’s not the answer as to why I can suddenly move forward easily on low pressures, because if it was about traction, I'd just need to install wider tyres with bigger knobs on my car and be able to move onto the beach on hard pressures. Still won't work.

 

Load distribution relates to weight distribution on each axle, and/or on left/right sides of the car. The load distribution of my car does not change if I just let my tyres down equally. So it plays no role here.

 

Again, the reason why I am suddenly able to move forward in loose ground when I dropped my tyre pressure is because I've reduced rolling resistance.

 

There's tons of stuff on the web on tyre pressures and rolling resistance in 4x4’ing. Here's just one of many:

http://www.4x4abc.com/4WD101/abc-combined.html

 

A quote from the above article:

 

Ground Material Resistance

Soft materials like sand, snow and mud build up in front of the tires because the tires sink more or less in soft material. As soon as the vehicle breaks the surface it constantly pushes against the resistance of the built up ground material. The deeper the tires sink in, the higher is this resistance. Deflated tires substantially reduce ground material resistance. In sand deflated tires do not create more traction – they reduce the ground material resistance (since the pressure per square inch is reduced, the sand molecules stay more stable and don’t shear – see note in “Traction” below).

 

Some more on the issue (and why it's not about traction):

http://www.4x4abc.com/jeep101/soft-sand-deflate.html

 

Now I know the next question I'm going to be asked is "So what, why are you talking about beach sand when I spend my time on all types of different surfaces, including dirt roads, etc., but never on the beach."

 

Well I had to use that most extreme of surfaces to explain that rolling resistance moves in a kind of yin-yang way from the one extreme of the very hard (tar/concrete) to the very soft. They are opposites to each other. Opposite rules about rolling resistance apply to each extreme. That's why you need super hard tyre pressures for a road bike and as low as safely possible for the really soft stuff. Now as you move towards the centre of this rolling resistance continuum (e.g. trails with medium hard/soft ground) that's where the real discussion starts.

 

If you want to get a little OCD about it, you'll probably start wanting to set up your tyre pressures differently for each type of trail (or same trail, dry vs muddy). E.g. if you're riding in dry hardpack in Pretoria you’d run higher tyre pressures than when visiting the KZN north coast with our notoriously sandy trails.

 

Then again, if you don't give a sh-t either way and just want to get on your bike and ride, well hey that's cool too. The only reason why I went to the trouble of writing this bladdy novel was that hopefully the misconception about rolling resistance will finally be put to bed.

[patches]

Thanks Tombeej, good explanations

[kingalton]

posted this yesterday - it explains the rolling resistance specific to bicycles tyres..

 

http://www.mtbonline.co.za/info/mtb-tyre-rolling-resistance.htm