29ers

mattpage

bennett_346 wrote:

If 29 inch wheels are so good for speed why don't roadies use them?

They do.

bennett_346

mattpage wrote:

bennett_346 wrote:

If 29 inch wheels are so good for speed why don't roadies use them?

They do.

I thought they used 28 inch.

supersonic

They are 700c rims. Same as 29er. But with the tyres, of course, the overall diameter is a lot less.

bennett_346

supersonic wrote:

They are 700c rims. Same as 29er. But with the tyres, of course, the overall diameter is a lot less.

Thats what i mean. Stupid measuring standards.

mattpage

The MBUK article goes some way to trying to explain all the confusion. Mixing metric, imperial and diameters with or without tyres has created lots of confusion.

scarbs85

I find it a little sad that nobody from within the industry seems to be able to find a good thing to say about 26ers at the moment.
I don't consider myself oppose to 29ers or denying their advantages. I just want SOMETHING to hold onto so I don't feel like my current 26inch bike is an inferior piece of kit in every respect.

andy_welch

The industry exists to sell bikes. Why would they tell you that your current bike is fine?

I find the 650B results interesting. I don't believe that the difference in size over 26" is enough to make a difference, yet it was faster uphill than the 29er on 3 of the 4 uphill sections and 2 of the 4 overall laps. That suggests to me a bit of observer bias (which is pretty much impossible to exclude in a bike test). Mountain biking is all about confidence. If you think the bike will roll over stuff better then you will attack a section with more confidence and be faster (whether the bike really is better or not).

The average power is also pretty meaningless as any racer knows it's not just how much power you can put out that matters, but where you apply that power. The fact that the variance is so low is also a bit suspicious as it suggests that the rider was getting feedback on the average power output during the test.

ddraver

Sorry andy, but why do you think there is not much difference between 26 and 27.5, what you ve written suggests that the reality is that you don't want to believe there is a difference.

That the rider had feedback on average power is specifically said in the methods Matt pointed out on pg 2

How would you suggest testing the differences between different wheel sizes?

mattpage

andy_welch wrote:

The average power is also pretty meaningless as any racer knows it's not just how much power you can put out that matters, but where you apply that power. The fact that the variance is so low is also a bit suspicious as it suggests that the rider was getting feedback on the average power output during the test.

Yes of course I was getting feedback, the power meters relay the information to the Garmin Edge 500.
I was able to see exactly what the power output was per second, also per 30 seconds and per segment. They were the only measurements being shown on the screen. I had no timing information, or heart rate or anything else. That allowed me to keep it extremely accurate across all bikes. If average powers were vastly different then the whole test would have been flawed.

You don't believe the difference is great enough, yet I bet you have not ridden a 650b bike - let alone 3 bikes of each different size back to back.

If you had read the article, which you clearly have not then you would know why the 3rd and 4th downhill times were different to the first and second.

I suggest you get your facts right before accusing me of being biassed.

ddraver

:P

andy_welch

Steady on mate. I'm not accusing you specifically of being biased. I'm saying that observer bias is almost impossible to eradicate from any experiment. That's why all drugs have to go through properly blinded trials before they can be sold, for example.

Despite how it may sound that's not meant as a criticism of you. I can't think how you could design a test of different wheel sizes that would in any way qualify as scientifically rigorous either. I reckon you've done about the best that can be done as it happens and anyway MBUK doesn't claim to be a science journal. It's all just for fun.

The fact that you had instant feedback on the power meant that you could adjust it to make the average power the same. Again that's not a criticism, it's how you designed the test. But a 1-2 watt variance in average power in a rider who can see their average power on the screen in front of them is not the same as a 1-2 watt variance from a rider who is blinded to the power output.

bennett_346

andy_welch wrote:

The fact that you had instant feedback on the power meant that you could adjust it to make the average power the same. Again that's not a criticism, it's how you designed the test. But a 1-2 watt variance in average power in a rider who can see their average power on the screen in front of them is not the same as a 1-2 watt variance from a rider who is blinded to the power output.

Agree on this.

andy_welch

ddraver wrote:

Sorry andy, but why do you think there is not much difference between 26 and 27.5, what you ve written suggests that the reality is that you don't want to believe there is a difference.

That's just my bias

I guess part of the reason is that, as I understand it, 650B isn't 27.5. That's just a marketing ploy to make it sound half way between 26 and 29, when in fact it's much closer to 26".

I'm not anti 29er by the way. I'm currently off the bike after yet another OTB, so I'm pretty interested in the idea that they might not get stuck in so many wheel traps for a start. I also spent a couple of months doing an extended test of a 29er HT (as the shop lent me one while they took an age to fix my 26" Trance). I rode it on loads of trails, loads of times and tried to compare the times against those that I'd done on the full suss Trance, but I still couldn't get a difference that was statistically significant.

In answer to the question of how I'd design the test. The answer is pretty simple. Unless I could think of a way of designing a test where the rider didn't know what wheel size they were riding I wouldn't bother. Once you know what you are testing it's just not possible to conduct a fair test. But, as I said, it doesn't really matter. It's all just a bit of fun.

supersonic

I'm looking forward to the 'new' 26 and 1+1/4 size (597mm - 25mm smaller than the 700c - 650B is 25mm larger than a 26er), and the 'in the middle' 26 x 1+3/8 (590mm).

;-)

To be serious though, I am surprised the latter size was not chosen to be pushed forward. But as 650b is more established, I guess this is the one that was concentrated on for the inbetweener size.

mattpage

andy_welch wrote:

The fact that you had instant feedback on the power meant that you could adjust it to make the average power the same. Again that's not a criticism, it's how you designed the test. But a 1-2 watt variance in average power in a rider who can see their average power on the screen in front of them is not the same as a 1-2 watt variance from a rider who is blinded to the power output.

Perhaps you don't understand the design of the test.
The power was controlled, the resulting difference in time was intended to show any difference in wheel size. Every variable that it was possible to control was controlled.

I don't know why you would want a rider to be blinded from the power output?

It might be interesting to do another test while blinded from the power output and ask the rider to go flat out on each lap and see the difference in time and power, but that wouldn't be a controlled test.

andy_welch

The downside of having feedback on your power output is that it gives you the theoretical possibility to manipulate the test. Let me give an example. You could put out a bit less power on a difficult uphill section, losing a chunk of time. Then put out a bit more power on an easier (faster) section. That would give you the same average power but a lower overall speed due to the old problem of wind resistance increasing with the square of the speed. I'm not accusing you of doing this or of trying to deliberately bias the test in any way. But when you are trying to design a test you should always be asking yourself "how can I design this test so that I can't cheat".

Personally I'm not sure why you need to control power as long as you measure it. If you tended to put out more power on one bike than another that would have been interesting and since you are not a robot (now there's an idea) you can't really put out the same power at each point on each lap (just try to compensate for differences after the event so to speak).

But I really think I've flogged this horse long enough. I wasn't trying to have a pop. As I say it's very hard to design a decent test. I think you've done the best job so far and I'm grateful to you. It's certainly given us something to talk about.

Cheers,

Andy

ddraver

I can see what you mean andy, but you ve kind of hit the nub of the matter.

For example you could have an identical e-bike that put out a specific amount of power through the pedals at set points through the course, triggered remotely so that the rider just had to steer. But then people would still argue that the rider was not "blind". But then part of riding the bike is choosing lines, so would you make the rider ride the same lines on each bike, or lines that best suited the bike? Would the rider have control over braking? could the rider move their weight around? In the end, you'd be better off just running the wheel over a bump in a lab, but then people would claim that that wasnt "real world" anymore

I can't think of a test that would be accepted by people that are as anti big/bigger wheel as some of them are...

njee20

I think what Matt did is the most accurate way of doing it by far, I personally don't think that not having sight of the power output would make it any more accurate (quite the opposite).

The fact Matt had the data in front of him the whole time no doubt meant he kept the power consistent the whole time, rather than sprinting up the climb and then thinking 'aah, bugger, need to soft pedal to get the average down now', so it's a completely flawed observation surely?

Not knowing the power (and keeping it constant) means it's just another variable and is totally meaningless. You may as well also use the test to find out which the fastest base layer and pedal combination is. The whole point is that power was a constant...

andy_welch

Well if Matt can ride up or down a tricky section while looking at his power meter then he's a better man than me My concern with having the power feedback is that you attempt to compensate for the fact that you didn't put quite enough power out in one section a bit later on, which keeps the average the same but isn't really the same thing. But let's not over do this. It doesn't really invalidate the test, it's just part of the design and needs to be taken into account when discussing the results. The problem is that, as ddraver points out, none of us can design a "real world" test that is scientifically rigorous enough to convince a sceptic.

Personally I'd be tempted to give this guy a call and see if he can tell the difference

http://youtu.be/TndKV1qhljA

Cheers,

Andy

The Rookie

Yes Trolcyd, but a rider will always know what wheels are fitted, it's obvious, however the garmin didn't know, so that covers the timers! As for lots more riders or circuits, impratical. The data is certainly statistically significant in showing 26ers to be slower.

ddraver

Further to The Beginners point - A rider has to know what wheels he is riding so he can adjust the optimum line to what best suits them to make the test applicable in the real world - line choice is part of bike racing after all....

What amuses me slightly through all of this is that people seem to think that all this was done before 26in wheels appeared. No, Keith Bontrager just cut out 2in from a 28in road rim and welded it back together? You think the Klunkers did double blind studies to scientifically establish the best wheel width for off road riding? Like, whatever dude, Come on!

mrmonkfinger

ddraver wrote:

You think the Klunkers did double blind studies to scientifically establish the best wheel width for off road riding? Like, whatever dude, Come on!

I'll have you know Keith Bontrager, Gary Fisher and Tom Ritchey were some of the finest scientific minds produced during the 20th century.

EH_Rob

The Beginner wrote:

The data is certainly statistically significant in showing 26ers to be slower.

I can just see a table with times in it and a bar chart. To claim statistical significance requires a test. Whereabouts have you got this from?

rockmonkeysc

Surely a test carried out by a magazine which relies on advertising from manufacturers who are putting all their efforts in to selling bigger wheels could never be trusted as 100% accurate. MBUK, MBR and all the others have to keep their advertisers happy and would put that before honest reviews.

ddraver

I feel a standard, we don't give favourable reviews to advertisers comment coming out way....

njee20

Surely a test carried out by a magazine which relies on advertising from manufacturers who are putting all their efforts in to selling bigger wheels could never be trusted as 100% accurate. MBUK, MBR and all the others have to keep their advertisers happy and would put that before honest reviews.

Except Matt doesn't work for MBUK and doesn't make his money nor have any real affiliation with them...

rockmonkeysc

ddraver wrote:

I feel a standard, we don't give favourable reviews to advertisers comment coming out way....

The Specialized Hardrock used to win every beginners bike under £600 test despite being a bag of sh1t (I bought one) which is incredibly poor value. Specialized spend a lot on advertising with MBR/MBUK

njee20

Ok, but that had nothing to do with this test, at all.

rockmonkeysc

No but it does suggest that magazines print what their advertisers what to see and they want people to read that their latest big wheel bikes are better than your old 26" piece of shit

ddraver

RockmonkeySC wrote:

ddraver wrote:

I feel a standard, we don't give favourable reviews to advertisers comment coming out way....

The Specialized Hardrock used to win every beginners bike under £600 test despite being a bag of sh1t (I bought one) which is incredibly poor value. Specialized spend a lot on advertising with MBR/MBUK

In your opinion.

I rode my Dads version of something like that and was very impressed for what it cost....