Grand Bois Extra Legere tires now available

Discuss light weight issues concerning road bikes & parts.
xrs2
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Joined: Mon Nov 07, 2011 5:46 am

by xrs2

I have no idea how good these tires are in the extra legere version, but the weight is pretty spectacular. 181 grams for the 23 mm tires and 232 grams for the 32 mm version.

I've used the regular versions of both the 23 and 32 and they are really nice tires. Hopefully the extra light versions will be just as good.

Estelja
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by Estelja

The same place that sells those tires has some good information on rolling resistance:

http://janheine.wordpress.com/2012/06/1 ... -of-tires/

by Weenie


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djconnel
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by djconnel

I regret they're not available in 26 mm. I'm sold on 26 versus 23. The regular Grand Bois are really good tires: supple and decent puncture resistance until the tread wears too thin, then they become puncture prone. But I've gotten good life out of the ones I've gotten.

xrs2
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by xrs2

Agree. 26 mm extra legere would be nice. If it helps any, though, the regular Col de la Madelaine 23 mm tires actually measure 24.5 mm on Enve 3.4s freshly mounted, and the Grand Bois tires have a tendency to expand a mm or two over time. Haven't measured them recently because I moved and can't find my caliper!

John

fdegrove
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by fdegrove

Hi,

Estelja wrote:The same place that sells those tires has some good information on rolling resistance:

http://janheine.wordpress.com/2012/06/1 ... -of-tires/" onclick="window.open(this.href);return false;


They seem to have convinced themselves allright...... :?

A mild case of not seeing the trees for the forest if you'd ask me.

Ciao, ;)
Being a snob is an expensive hobby.

NGMN
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by NGMN

I don't know exactly what fdegrove is saying, but I will say this; I wouldn't automatically throw width out the window as the article seems to, if you are interested in fast paced riding. The difference between say a 23mm tire and a 27mm tire on the FC Zipp 303s can even be pretty huge, like 10 watts at 10-15 degrees of yaw, which at least from data I've seen is typically larger than the rolling resistance differences between a same brand and design 23 and 27mm tire.

fdegrove
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by fdegrove

Hi,

That's just one aspect, one which you'll need to take into account once you're reaching a certain level of wind resistance.
I would not be surprised to learn that the difference in wind resistance as seen by say, a 23mm compared to the 27mm version of the same tyre is far bigger than 10 to 15 Watt at higher speeds in a wind free environment already.
Either way, let's just assume that windresistance was not the target of the test.

If you want to measure rolling resistance than the protocol should be the same for every tyre within the apples to apples and oranges to oranges range. Carrying out such tests is far more easy to do and far more precise in a controlled environment.
From that prespective the lab tests as carried out by Tour magazine are scientifically far more valid than any such test carried out on a road.

Whether or not the tyre sees a fixed load (brick of lead fror instance) or a rider + a road as load isn't relevant at all for measuring rolling resistance either for as long as the load is the same for all devices under test. Something you can't be sure of when testing outdoors on a strip of road.
Point is that the relative order of difference between the test participants should and will be absolutely the same in both tests. The absolute figures may differ yet the differences should remain.

In short, there are a number of remarks and conclusions in that article that just goes to show that there's nothing new under the sun; setting up tests is one thing, drawing the right conclusions is quite another....

Plus ca change.....

Ciao, ;)
Being a snob is an expensive hobby.

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prendrefeu
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by prendrefeu

Just someone tell me what the ultimate tire and wheel combo to buy for all conditions at all times and under all riders.

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Bingomck
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Joined: Sun Nov 25, 2012 5:45 am

by Bingomck

Anyone planning on getting the 23s? Curious how they would compare to say Conti 4000s's

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SWijland
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by SWijland

I agree with fdegrove. This kind of testing is pretty silly.

HillRPete
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by HillRPete

From a bird's eye perspective, the testing protocol doesn't seem less in touch with reality than rolling on a steel drum. What do you not agree with specifically, SWijland?

xrs2
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by xrs2

Agree. Testing on a steel drum may be more accurate and reproducible, but it has little, if any, relationship to real world use.

You can poke holes in Jan's methodology, but how else are you going to perform the experiment under conditions approximating actual roads? Although they didn't specify their methods, one of the testers is a statistician and ran a presumably valid statistical analysis on the results. The differences were significant. This is a powerful argument that the results that they are seeing are highly likely to be real.

I haven't seen the Tour steel drum test (and I can't read German, anyway) but I'm betting that their experimental methods were shakier than Jan's, and I'm also willing to bet that they did not do a statistical analysis of their results.

I'd suggest that you read the actual papers before passing judgement. Although I disagree with a significant amount of what I read in Bicycle Quarterly, Jan and his fellow testers deserve to be commended for actually attempting to do an analysis that approximates actual riding conditions.

NGMN
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by NGMN

xrs2 wrote:Agree. Testing on a steel drum may be more accurate and reproducible, but it has little, if any, relationship to real world use.


That's funny because people have found high correlation between Al Morrison's extensive roller data and use in field testing...

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WMW
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by WMW

fdegrove wrote:Carrying out such tests is far more easy to do and far more precise in a controlled environment.
From that prespective the lab tests as carried out by Tour magazine are scientifically far more valid than any such test carried out on a road.


That "road" test simply has too many confounding variables... wind being a huge one, plus body position, different wheels, etc. These are easily great enough to swamp any Crr numbers.
formerly rruff...

xrs2
Posts: 228
Joined: Mon Nov 07, 2011 5:46 am

by xrs2

NGMN wrote:
xrs2 wrote:Agree. Testing on a steel drum may be more accurate and reproducible, but it has little, if any, relationship to real world use.


That's funny because people have found high correlation between Al Morrison's extensive roller data and use in field testing...


Could you please point out the study where they correlated roller data and use in field testing. I'd love to see the methodology because I haven't seen these data.

by Weenie


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