Rolling resistance

[brianj]

hey all,

going to change tyres before Sani... the bike came with maxxis Minion DH tyres, and they have definitely made the training tougher. Going for a Crossmax which should be easier going across most (reasonable) terrain. Is there a standard measure of rolling resistance? i.e. should i expect things to get 1% better or 5% better? here's hoping....

[Sardine]

Crossmarks will be easier going than your Minions if the ground is firm, but if it rains you will soon find the Crossmarks will clog-up with mud and you will have no traction. No traction may be ok when riding a short distance on  non-technical terrain, but over 80+ km with some pretty technical bits, it will be a nightmare.

 

If you want to change tyres then try a compromise tyres like the Continental Speed/Mountain Kings, which have wide tread that sheds mud better than the Crossmarks, but are still much lighter and fast rolling than your Minions. Or try a fast(er)-rolling mud tyre like the Bontrager Mud X. If you want to stick to Maxxis, the High Roller (26 x 2.1") is a good allround tyre, but probably is not as fast-rolling at the Mud X or Continentals.

 

[Brakkies Sport Fotos]

Hutchinson UST Phyton Lights xc

[Johan Brits]

Maxxis Crossmark - Awsome tyres!!

[brianj]

the decision is already made - crossmarks - but thanks for the opinions / options..... I will be doing my 'anti rain dance'.

back to the question, is there a measure of resistance?

[paulvs]

What is the terrain like out there @ sani? Very rocky or just roads... ?

[Johan Brits]

Good Choice!!

[Racer X]

Maxxis Larsen Mimo's are your'e best all round option. Good on the dry and grippy in the wet, Brandon and Kevin thought they were good enough to win on ,so, I spose they are good enough for the rest of us.

[The Guy in Pink]

.... I will be doing my 'anti rain dance'.

back to the question' date=' is there a measure of resistance?

[/quote']

 

None that I know of; 

A Standard measure would imply that the tyres are pumped to a standard pressure on a standard surface, with a standard loading.

(The most efficient wheel/road combination in everyday use is the railway carriage - steel wheel on steel road) 

 

You can lessen the rolling resistance of most tyres just by pumping them harder.

 

 

[Johan Bornman]

the decision is already made - crossmarks - but thanks for the opinions / options..... I will be doing my 'anti rain dance'.

back to the question' date=' is there a measure of resistance?

[/quote']

Someone else already answered the question of whether there is a measurement or not and he's right, there is no measurement.

 

However, since we know that RR is caused by knobbly squirm, you can examine the two tyres and say with reasonable confidence that there will be a 50% or 20% improvement. Rolling resistance on a slick is very, very small but increases dramatically as those knobblies get bigger. The worse ones will be long, loosely-spaced ones and the best ones, tightly-packed as in a Crossmark's centre ridge.

 

Thus, check the two tyres with the eye,  assess the relative size and density of the knobblies, suck your thumb and guess. You'll be no less accurate than all the claims made by tyre companies.

[brianj]

Thanks for all the replies, they have helped firm up my thinking...

Incidentallly i did research the issue a bit, there are 2 measures out there:

- measuring the 'run out' distance a tyre will run with a consistent rolling start (consistent surface and pressure)

- measuring the drag force with fixed load and standardised pressure (this is probably more scientific) The results of such a test look like this one I found.

 

 

It looks like there is up to 15% variation in the drag force apart from the one outlier. The pic is reference so the work can be googled for more info..

 

 

[Sequoia]

Am I being stupid, or are the tyres used in this test WAY too narrow for practical purposes?

[Thug]

 

Am I being stupid' date=' or are the tyres used in this test WAY too narrow for practical purposes?[/quote']

 

Nope and Yes.

 

Also why only a 30kg load ?

 

 

 

 

[NotSoBigBen]

Am I being stupid' date=' or are the tyres used in this test WAY too narrow for practical purposes?[/quote']

Nope and Yes.

Also why only a 30kg load ?

 

You right even LBB weighs more than that!

[brianj]

I would be interested to see what the load distribution would be between front and back wheels.... 30kg is brobably not that far off for a 75kg rider / bike combo on level surface.

I dont think the test is practical either, but at least there is some attempt being made at quantifying this.

[MintSauce]

Am I being stupid' date=' or are the tyres used in this test WAY too narrow for practical purposes?[/quote']

 

 

Those sound like CycloCross tyres to me.

 

 

Had a look at the Bontrager Dry X the other day. Similar to the Mud X, smaller, lower profile knobs, closer spacing.

 

Looks very interesting. Back in the day Gary Fisher made a tyre with good old square knobs, evenly spaced. Keep it simple, eh....they rocked