Chris Porter Talks: GeoMetron 29" Prototype
I think the big wheeler might need a hug after reading this.
I took a first ride on the Nicolai Mojo GeoMetron earlier this year. Since then I borrowed another similar version from one of the Nicolai engineers, which I put through it paces over a couple of weeks on the Italian Riviera. Passing through Risca recently, I dropped into the Mojo unit for a chat (coincidentally my forks were due a service, and I needed a coffee) and there she was: Hanging majestically from the work stand, I lay my eyes upon her, having no idea of her credentials. Hang on a minute, are those 29" wheels? Chris replied "Yes, it has just come in, I still hate them, but I wanted to build one to shut you, Steve Jones (from Dirt Magazine) and Alan Muldoon (MBR) up, as you guys never stop going on about how much you love 29ers. I'm going to prove they're not better." Over the course of drinking my americano, I persuaded Chris to let me take it on my onward journey to Madeira for a couple of days. It took a while to fit it into the bike bag, and further issues came when trying to get it out of the bag, getting it to fit on the bike shuttle, in the public bus and into the hotel room – even some of the streets struggled with its size. I had a great time on it, and would love to do some back to back runs with both sizes in the future. For now, here's the caffeine-fuelled chat as we watched Paul the technician gently ramming the monster into the bag.
 | Yes, it has just come in, I still hate them, but I wanted to build one to shut you, Steve Jones (from Dirt Magazine) and Alan Muldoon (MBR) up, as you guys never stop going on about how much you love 29ers. I'm going to prove they're not better. |
How have sales and feedback been from the 27.5" bike?Sales of the 27.5" version have exceeded all expectations. We’ve sold more in six months than we planned for the first year. The general acceptance has been amazing! No-one has ridden it and not liked it (Alan Muldoon from MBR had some criticisms, but he was riding the wrong size and using his ‘test ride’ as a geometry experiment – we weren’t in control of what changes we made, he was asking for them). In fact, the number of people who have bought bikes following test rides is amazing. Quite a hit rate!
Do you think people have gotten over the initial shock of the 'crazy' angles, and now accept this as a viable option?I reckon the fact that all of the Nicolai staff have been using versions of our GeoMetron and they have released the Pinion gearbox equipped bike with our ‘crazy angles’ shows a level of acceptance. A real production bike with our angles. Everyone that rides it accepts the geometry without question. After an initial “it climbs OK, turns well, seems pretty good in tight corners” period, they all just shut up and ride! The major feedback I get is when people go back to their normal bikes and email me afterwards to say how awkward, small and twitchy they feel.
We talked a lot about wheel sizes when I came to test the GeoMetron. You seemed very anti-29" at the time. What has changed, why have you built this?I’m still not a fan of 29-inch wheels. There’s too much gyroscopic effect at speed. They feel OK in certain circumstances but when it gets fast and direction changes are at speed they feel very limited. The reason I built it was literally to show that the 27.5 version is better! There was quite a bit of talk amongst 29er fans of how much better this bike could get if it had 29-inch wheels. That’s why I built it.... The 27.5 GeoMetron has a lot of the good traits of 29er's (speed over rough ground, speed through turns, calmness of steering, etc...), but also steers well at speed and is very much more dynamic than the 29ers.
"Looks good from afar, but far from good"...
...the opposite is true with the Nicolai, she's a beauty in the flesh.
Can you explain why you think that the 29" bike won't be as good as the 27.5?The 29" version has a much lower bottom bracket in relation to the front axle, so front wheel braking traction and turning traction (at the corner entry point) will be compromised as the weight transferred to the bike from the feet is pushing under the axle and pushing the bike forwards. The lower BB height also means you can’t manual and hop properly. Basically, anything other than an SPD pull-up to lift the bike takes more effort and more time to achieve and time doesn't always allow for this on the trail. It encourages a wheels on the ground riding style. I feel that you have to lift the body to change direction... It’s just a feeling but it is definitely harder to change direction from one side to the other and it feels like it’s a fight. I think that’s precession (gyroscopic effect). I find it nervous in a straight line until it's up speed then it's great. But then at speed, it won’t turn.
The GeoMetron looks suspiciously normal with the big wheels.
Will you be putting these into production? We’ll build them! I’ve sold 3 of them already, if people want to buy them they are still an interesting bike, they share pretty much all of the geometry numbers of the original, just adjusted for the wheel size. It’s not like we just built a Tall Boy copy!
Somebody builds a one-off bike to 'prove' it's not as good as another, but then sells three of them with zero advertising or promotion – what does that tell you? Specialized had a good stab at long legged big wheelers with the Enduro 29, then seemed to back off the offence as they put more effort into 650b and plus sized tires. A few other brands have had a pop like Banshee, Evil and On-One for example. But nobody has really gone all in, yet, with designers seeming to make things shorter and steeper compared to their little brothers to offset the supposed negatives of big wheels, or maybe just to make numbers look more controllable on paper. Time will tell, but interesting times are here. - Paul Aston
MENTIONS: @mojosuspensionmedia / @paulaston
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I appreciate all wheel sizes, and totally enjoy the playfulness of 26ers, but saying 29ers can't corner is just plain wrong. Yes, it may be a more on-the-ground riding style, and yes, not everyone might like that, but they are crazy fast. BB drop is actually a good thing, too, and today's brakes can handle the front wheel very well.
I think maybe super slack 29ers like this one may well be not work so well.
I often forget I'm riding the little bike until I hit a bunch of rocks..
www.pinkbike.com/photo/11528213
roll over an obstacles carying speed ,the smaller wheel will carry the same speed but will also go in and out , up and over very much like a pump track....smaller wheels are just as quick , slower in certain conditions but also quicker in others
*if so, go all in and make a lower and slacker PP Shan out of titanium
Not that I prefer bigger wheels though.
Buy one of our frames. They roll over stuff better than anything out there, and they are still 26"
It might be a little bit harder to break loose but when it does it's a lot easier to keep it sideways throughout the turn.
You can easily lower it to 140 (which I prefer) or 130/120mm by replacing the air piston. Should cost around 30 euros if you do it yourself.
www.youtube.com/watch?v=WPVRU7jSYkQ
That aside I still wait with baited breath for the review from Paul.
1) ...riding in the manner that he is talking about
2) ...think 29 is good just because it's 29.
They also tend to mimic that same old crap from the guy who sold the bike to them about how it rolls over crap and goes faster. Blah, blah, blah...... I would be more impressed if they took that thing to their or it's limit then gave feedback based ON THEIR OWN EXPERIENCE.
I actually think some 29's are rockin' and seriously looked at a couple before getting a Canfield Balance.
-Man's gotta eat.
Cheers!
One thing I'm surprised about here, though - he seems not to understand that the gyroscopic effect problem he talks about is a matter of scale. I'm a 230# rider - so to lean over a 29er at speed is proportionally no harder for me than it is for a lighter rider to do so with their smaller bike. A smaller wheeled bike actually leans over way to quickly and easily for me - leading to a twitchy sensation I don't like very much (and yes, there's a difference between twitchy and playful - I like the latter, loathe the former). I bet if he were to look at the people who like his new 29er, he'd find their bigger dudes who can take advantage of the advantages of the bigger wheels without being hamstrung by the big wheels being overly stabilizing at speed.
Err, nope, as far as traction is concerned, physics says otherwise. It's about the relationship between the centre of mass and the tyre contact patches (i.e. BB height and distance behind front contact patch), not the relationship between the centre of mass and the front axle.
When cornering off the brakes (i.e. assuming no rear-> front weight transfer due to braking) , force (weight) is only transferred to the ground through the tire contact patches, and it makes no difference to traction where the axle height is in relation to the total system (rider & bike) centre of mass.
When braking, the weight transfer is a function of where the centre of mass is in relation to the front contact patch, and (as long as you don't lock up the front wheel) is also independent of the axle height. [Once you lock up the front wheel and start going OTB your contact patch becomes a 'VPP', in which case wheel diameter does make a difference - the larger the wheel diameter, the more your lever arm grows as you roll up onto the front of the wheel].
In racing terms, the bike is more likely to push in this circumstance.
You referred to the physics while upright and braking, and while cornering off the brakes. I did not see a specific mention of that period of turn in under heavy braking (because we're only going to get significant weight transfer along the longitude under heavy braking).
"What happened to not braking in corners?"
Let's ask two questions instead of one.
1) What happened to not braking in corners?
I'd have to agree that's not always the best thing to do, but that may depend on circumstance (did you overcook the entry or is the corner radius decreasing?) and the dynamics of the bike you are on (some motorcycle guys like to use the rear brake mid-corner to help settle the back end or control wheel spin). Another reason to use it may be mid-corner attitude adjustment.
On a mountain bike, I'm game for mid corner braking with the rear, if I feel I need it. I stay away from the front mid corner. Going through the limit of front traction while leaned over sounds like a good way to end up on your head.
2) What happened to not braking INTO corners?
Ever heard of trail braking? Read this --> en.wikipedia.org/wiki/Trail_braking
On a mountain bike, I trail brake with the rear, unless it's a berm. On road motorbikes, I trail brake in on the front. If I wanted to go in deeper, I also backed it in using engine braking (as opposed to the rear brake). Check this out. --> www.youtube.com/watch?v=P4A91t2RQKg
I guess I'm trying to say that there is no absolute hard and fast here. While some things may not be suggested, there are viable reasons for doing them from time to time.
And it's fun. :-)
Source: 4 years of studying this stuff + another 4 years working on vehicle handling professionally.
Edit: I can see how people would not understand why this is. Your centre of mass does push down through the BB as it is more or less directly above the BB in a static standing position; in this case the force acting on the centre of mass (gravity) is in line with the BB. However, it doesn't "push forwards through the BB" under braking (or cornering) loads because those loads are applied through two planes, which are the ground (which we'll call horizontal) via the contact patch of the tyres, and a parallel plane at the same height as the CoM (via the inertial forces of the CoM as a reaction to the tractive force of the tyres). Neither of these lines/planes of force are related to the axle height or BB drop.
As @dsut4392 points out, once the rear wheel lifts off the ground under brakes, THEN the BB height relative to axle becomes somewhat relevant (and still in no significant way IMO) because then the BB is actually moving slightly/more rearwards as it pivots around the front axle (not the front contact patch as it was trying to prior to the rear wheel lifting), which will shift the centre of mass in a different manner according to differing axle heights.
Did Chris describe it in terms that are sensical or correct? I'll leave that to you guys. But the real crux of the conversation is behaviour at turn in while trail braking, and I suspect he's right, regardless of how he described it.
1) Let's let the whole "push under the axle" thing go. If you keep in mind the context, the greater question is "are larger diameter wheels more likely to push during turn in while trail braking"?
2) You and dsut seem to be focused on weight transfer. Particularly along the bikes longitude and in a steady directional state. I'm pretty sure that what Chris is talking about is behavior WHEN CHANGING STATE! The moment you initiate a turn you begin to transition and continue to do so until you reach the needed or desired lean angle. This is a critical phase made more so by the fact that your available front end grip is finite, and complicated yet more when the brakes are still on. Considering that it's good practice to slowly release the brake means the act of doing so is another mechanism that's affecting the constant state of change.
3) If wheel diameter doesn't matter then there is no such thing as centrifugal force? Or are you saying that the weight of it is such that it's a non-issue? Or perhaps the load variation makes up for any negatives associated with centrifugal force. I mention this because you CAN overwhelm front traction by expecting it to do too much.... braking too hard at the approach and/or turn in too a corner. Wouldn't more centrifugal force have an affect on the contact patch, and more? I can't stress enough that there is only so much traction.
Once again, I'm not saying you and dsut are wrong. You guys are right! But I don't think you caught what he was really talking about.
What I will say is that I've experienced front end push as a result of poor conditions (wet or contaminated with oil or coolant), bumpy surfaces, over cooking the entry, power oversteer (which never happens on a bike), too much dive on the front, and simply being too exuberant at the bars when initiating a turn in. Never mind sidewall stiffness, tire pressure, fork flex, tread pattern, compound, and on and on and on..... It's a huge issue! In this case, it's one that's probably best solved by good and extensive testing with tightly controlled conditions and variables (as much as possible).
As far as i know, more weight transferred = more traction. Especially when transferred forward as he mentions. Absolutely all bikes i've ridden, lower BB meant more traction, especially in turns.
2nd, if there's one good trait i do love about 29ers is the ability get good traction, partially due to their BB being lower than the axle. I'm running tires so worn out / slick on my 29er that i would've got me killed on my 26".
So what am i missing here? i guess he knows what he's talking about, but it makes no sense to me...
But I agree! :-)
Here is their 29er with 140mm of travel and a wheelbase of 1314mm in size large and a headangle of 64.5 :
www.polebicycles.com/bicycles/mountain/enduro/evolink-140-en-29
M'kay...
Every product this guy has ever designed sells out despite their obvious flaws
There's genius at work somewhere here
www.pinkbike.com/news/canfield-brothers-riot.html
Just work your noggin' buddy
Is ordering one as easy as contacting Mojo UK?
www.vitalmtb.com/product/guide/Frames,7/Banshee-Bikes/Rune-V2,13585 exact same job