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What type of sealant do you use and why?
1. Eclipse 15%  15%  [ 3 ]
2. Stans 35%  35%  [ 7 ]
3. Home made 35%  35%  [ 7 ]
4. UST Standard [non ust tires with sealant] 5%  5%  [ 1 ]
5. UST standard [ust tires] 5%  5%  [ 1 ]
6. UST standard [ust tires with sealant] 0%  0%  [ 0 ]
7. Nagesti [non ust tires] 5%  5%  [ 1 ]
8. Nagesti [nagesti or ust tires] 0%  0%  [ 0 ]
9. Nagesti [nagesti or ust tires with sealant] 0%  0%  [ 0 ]
Total votes : 20
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 Post subject:
PostPosted: Fri Feb 27, 2004 12:36 am 
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So several people have mentioned rolling resistance. This confuses me.

If your using a 2.0 tire with a tube in it and have it inflated to 40psi you would have a certain amount of rolling resistance (call that X).

Now if have the same exact tire with no-tube and are using some sort of sealant instead and have it inflated to the same pressure (40psi) how can it have lower rolling resistance??

This doesn't make any sense to me. Mostly because I have ridden the same tire with and without a tube in it (at the same pressure setting). When you use a sealant you get more grip, because you have a larger contact patch with the ground (because you don't have a tube in there supporting the tire keeping in a certain shape). So if you have a larger contact patch, wouldn't you have a greater rolling resistance? The to top it all off people say they like using Stan's or Eclipse because they can run lower pressure. Wouldn't lowering the pressure increase the rolling resistance even more?

Maybe, I'm just not understanding this?? Don't get me wrong, I love using Stan's and will never go back to tubes, but the whole point about rolling resistance doesn't make sense to me.


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PostPosted: Fri Feb 27, 2004 12:57 am 
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Xterra, when you use a tube there is a certain amount of friction between the tube and tire each and every time the tire deforms ...this resistance to deforming essentially is a rolling resistance

yes, on smooth pavement lowering your air pressure would increase rolling resistance but on a rough trail the less you are bouncing around the better and smoother the ride i guess ...so you can keep pedaling which makes you go faster ...also the greater contact patch of lower pressures gives better handling on the corners


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Posted: Fri Feb 27, 2004 12:57 am 


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PostPosted: Fri Feb 27, 2004 4:29 pm 
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Maybe I still don't get it...

If you compare apples to apples you get the following:

Senerio - Same trail (doesn't matter if it's rough or not), same test tires, one with notubes and one with tubes, same pressure settings:

Result - Tire with tubes will have a smaller contact patch than the tire without tubes. So the tire with tubes will have a lower rolling resistance.

I understand you have more control with a larger contact patch (like when running notubes or just running at lower pressure settings in either case), but control doesn't equate to rolling resistance. It's not the same thing.

You are corect that rolling resitance is the amount of friction, but it's the amount of friction created between the tire surface and the ground. So the more contact patch a tire creates the more rolling resistance there is. Take a MTB tire and pump it up to 65psi....yes you have control issues but you also have low rolling resistance. Take the same tire and drop the pressure to 35psi, you have more control, but also more rolling resistance.

I understand the better control and better cornering and better grip and all that stuff, I'm just questioning people saying better rolling resistance.

Am I wrong on this??


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PostPosted: Fri Feb 27, 2004 4:54 pm 
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well you have rolling resistance from the friction of the tube and tire and between the tire and the ground (the contact patch) ...but for identical tires on varying terrain, the friction between the tire and ground for various air pressures isn't as significant as the rolling resistance generated from the friction of the tube and tire ...not even close ...it is getting the tube out of the equation that makes all the difference in the world ...i am yet to try riding tubeless but i already understand how beneficial it is

i also ran 70psi one race and while sure, i probably had the lowest rolling resistance (tire with ground) of anyone else who may have been riding on that exact tire, it was not beneficial at all because the course was very rough so i bounced around like a basketball ...and their was plenty of friciton inside between the tube and tire

in effect, anything that prevents the tire from deforming to the surface of the terrain is rolling resistance ....i don't know if you get what i'm saying


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PostPosted: Fri Feb 27, 2004 7:14 pm 
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I get what your saying but I don't think it's right.

Quote:
in effect, anything that prevents the tire from deforming to the surface of the terrain is rolling resistance ....i don't know if you get what i'm saying


So your saying that if a tire conforms to the ground you have less rolling resistance? (By what you said "prevents the tire from deforming".

This doesn't make sense to me. If you have more deformation of the shape of a tire that means you have more contact between the tire and the ground. I thought this was an increase in rolling resistance.

So if your running tubes you have support within the tire casing that prevents deformation, thus decreases rolling resistance verses the same tire without a tube. If your running the same pressure in each, you have more deformation of a tubeless (the reason why you get more grip) resulting in more rolling resistance.

On a different point...I understand you will have friction between a tube and tire, but I can't imagine this is substantial enough to measure verses the friction between the tire and the ground.

My whole point to all of this, is prove or disprove those who say one of the advantages to running tubless is less rolling resistance.

Not trying to be argumentative....just trying to find the real story.


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 Post subject: Rolling Frictions
PostPosted: Sat Feb 28, 2004 7:25 am 
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Another form of rolling resistance is the internal flexability of the tyre (how hard it is to deform/rebound). This is one that matters to the No-Tubes situation in how it lowers the amount of slowing down a tyre does when it hits a bump. This is why a tyre needs a minium size depending on conditions.

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PostPosted: Sat Feb 28, 2004 7:53 am 
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i am not good at explaining things ...that is the problem here

but you are right, obviously lower air pressures equate to more tire contact with the ground which means increased rolling resistance ...there is no denying that ...but i think that this increased rolling resistance is more than offset by not having the friction between the tube and tire

one way to put it is if you had identical tires and identical air pressures ....except one wheelset has tubes and the other is tubeless they will not have the same rolling resistance ...i can guarantee you that ...the tubeless set-up with the exact same tires and same air pressure will be much faster


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 Post subject: Explination difficulies
PostPosted: Sun Feb 29, 2004 6:25 am 
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This is hard to type but easy to demonstrate :(

There is a bump size that will not be absorbed by the tyre and be transfered to the bike. The softer (and larger) the tyre the larger the obsticale can be before the bike recives the slowing force. The maximum obsticale size/ lowest tyre pressure combination is when the tyre bottoms out on the rim. With a tube this can/will result in a pinch flat. The tubless advantage is that the tyre /rim impact will/should not result in the tyre going flat, as a result the tyre can be run softer to absorb more irregularaties- and therefor roll faster.

This made sence to me when I typed it :wink:

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 Post subject:
PostPosted: Sun Feb 29, 2004 6:38 pm 
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As others said before me, this is easy to demonstrate, but hard to type.

The more width a tire has, the lighter is the roling resistance.

I think this pretty much covers cyco's story.

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 Post subject:
PostPosted: Mon Mar 01, 2004 5:24 am 
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Tubeless decreases rolling resistance of a tire because it decreases the amount of energy lost to interaction between tire and a tube. Here's a German Bike magazine rolling resistance test (top one) which amongst other things tested the effect of tubeless vs tubes rolling resistance. You can see that Schwalbe Racing Ralph with Eclipse scored lowest rolling resistance whereas the same tire with a tube is about 5 W more few placings to the right.

Lowering the tire pressure will most certainly increase rolling resistance but offroad this indeed will make you faster as opposed to higher pressure because on each small bump, instead of the entire weight of the bike and yourself being lifted up across the bump (converting your kinetic energy [ie speed] into potential energy [ie 'climbing' the bump]) a tire will deform instead thereby not 'climbing' the bump and wasting energy in lifting your mass up across the bump. Here tubeless would be superior to tubed especially, as we increase and rely on tire deformations hence want to minimise energy lost there which tubeless does.

I hope that came across legibly but basically when riding low pressure you are not faster because of lowered rolling resiance (which is in fact higher) but improved suspension abilities of the tires. In either case running tubeless will reduce losses from the tube making you faster at any pressure.


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PostPosted: Mon Mar 01, 2004 7:37 am 
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thanks Boj, you explained it much better than i was able to!


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 Post subject:
PostPosted: Mon Mar 01, 2004 4:56 pm 
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Ok....boj makes the most sense here about this whole debate (plus he has scientific proof).

If you compare apples to apples your going to get a 5 watt decrease in rolling resistance when using the same tire at the same pressure under the same conditions when comparing tubes to tubeless systems.

However, if you drop the pressure you negate this advantage (granted you get better control).

So for all of us we now know the truth.....to say one of the advantages of using a system like Eclipes or Stans, is nothing more than marketing hype. The reason being a 5 watt advantage is hardly signigicant and most people will drop their pressure settings anyhow and negate that advantage to opt for much better control without the risk of a pinch flat (the real advantage to tubeless).


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PostPosted: Mon Mar 01, 2004 5:21 pm 
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I don't think I will drop my pressure settings...


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PostPosted: Tue Mar 02, 2004 3:27 am 
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Xterra Racer wrote:
So for all of us we now know the truth.....to say one of the advantages of using a system like Eclipes or Stans, is nothing more than marketing hype. The reason being a 5 watt advantage is hardly signigicant and most people will drop their pressure settings anyhow and negate that advantage to opt for much better control without the risk of a pinch flat (the real advantage to tubeless).



The suspension abilities of the tire at low pressures have nothing really to do with tubes or tubeless. Ie you run both tubes or tubeless at lower pressure to get suspension or high pressure to get good rolling resistance, it doesn't matter which system you use. Its just a matter of achieving a perfect balance where there is least rolling resistance for best suspension performance.

Tubeless however is faster at any pressure because it will generate less rolling resistance than equivalent tubed set up at the same optimal pressure. There is no trade off where you have to run tubeless at low pressure - you run them low for reasons mentioned above, just like you'd run your tube at same low pressure for the same reason. However you'd still roll faster with no tubes.

Below is a spreadsheet which calculates my speed difference (how many seconds faster/slower I'd go for the same effort) around a XC track near me for varying rolling resistance and weight properties of bike and tires. For the record I complete this track in around 10:30 sec a lap average for a XC race.

Below it is set up using data from the Bike mag test shown above for rolling resistance for the two racing ralphs, one with tubes and one with Eclipse. So you can see that effect of tubeless on both wheels saves about 5 seconds a lap on this particular track. Across a race this would equate to about 40 seconds faster, which is pretty sweet.

Image


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Posted: Tue Mar 02, 2004 3:27 am 


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PostPosted: Wed Mar 03, 2004 12:41 am 
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Boj,

I agree, but your not factoring in that you can run tubeless lower than you can run tubes.

When I go out and ride a local trail I know that I can run tubes at a certain pressure and not pinch flat (say 40-45psi). But if I ride the same trail with tubeless I know I can run lower pressure (35-38psi) and get better control and obviously not have to worry about pinch flats. If I tried to do that trail with tubes at the lower pressure, I would pinch flat more times than not.

So I conceed that comparing the same tires, one with tubes and one without and running the same pressure gives you the rolling resistance advantage to the tubeless. However, you not going to run tubes at low pressure because of pinch flats, so you can't make the comparison. The advantage of running tubeless at lower pressure is the control factor, not the rolling resistance.

For example: You run Conti tires with tubes at 40-45 psi on X trail. But when you run tubeless you run lower pressure 33-38psi because it allows you more control. You don't have a rolling resistance advantage with the tubeless because you can't run tubes at that pressure and expect them to last.

People that claim rolling resistance with tubeless as an advantage also do this in the same breath they say you can run lower pressure. You don't get both advantages at the same time, because you would never run the tubes at the same low pressure settings.


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