definitely not 96

Last time I left you on the 29er front I was just off into the shed to fetch out a 26″ front wheel. (http://forums.mtbr.com/showthread.php?t=196263)

I pulled out a 26″ front wheel and tried it. The worlds second 69er.

Instead of looking like a Chopper or a Stingray it looked odd, but definitely no worse than any 96ers out there. Indeed, from the seattube forward it looked a whole lot better. My wife suggested I try two 26″ wheels in there. Not a bad idea. I could ride the bike with the same geometry and angles and the only difference would be bottom-bracket height and fork trail.

Hey! It looked like a well-proportioned bike again. Maybe the bottom bracket height was a bit low compared to what you expect, but it certainly didn’t look that odd.

So I threw the bike and the 29″ wheels in the car and headed off to reride Saturdays trails.

First of all I rode them in it’s 26″ incarnation.

At the front end it was noticeably quicker steering, like my old Spot or the Rocky Mountain Hammer when fitted with Pace RC-30s. Sharp then, but not twitchy.

The rear end was likewise transformed. It had some life, some snap, some feeling! Unsurprisingly, it didn’t smooth the trail out as much as the 29er wheel. It was also less smooth than my wife’s regular 26″ wheeled Spot which runs the exact same chainstay length. Which only tells us that frame material makes a difference. Tell us something we didn’t know!

On the rocky uphills it suffered no loss in traction. On the final climb, I not only rode it past the point where it had stalled on 29″ wheels, it made it clean to the top. Why? Because I could now choose where I wanted the bike to go and pick the smoothest line.

Now I was faced with the downhills, and I wondered briefly about the low bottom bracket height. I’d not had an pedal strikes on the way up, would it ground on the way down? Well, not on the steps it didn’t, so off to the more technical downhill I headed - the Ice Cream Run for those who care about such things. It’s not World Cup DH course technical, but it’ll do. It just felt more manoeuvrable underneath me, I could change lines, I could unweight or lift the front end better, and in the air I could make tiny corrections. With only 80mm of travel the forks had a busier time of it with the small front wheel but the lower unsprung weight and fatter rubber than my normal tyres meant things didn’t get out of hand. A pair of Fox Vanillas on there and I’ve have been laughing.

The rear end bounced around a bit, but followed eagerly enough, and the fatter rubber than I normally run made things better than my regular hardtail.

Back at the car, I checked no-one was around to point and laugh, swapped the rear wheel for the 29er version, and headed back out on the same trails.

At the front the steering was now bang on. There is something in those criticisms of the forks. If the regular 29er steered like this I’d have been a whole lot happier with it from the start.

At the back that old sluggish feeling was, um, back. Over whoops, where I wanted to maintain momentum down one side to get me up the next the 29″ rear wheel definitely helped. The Dirt Demo trails at Vegas with their rolling whoops are favourable to big wheels.

At the top of one climb I looked back and I could see where my two trails rode side by side. The 26″ rear wheel trail showed marked treads where the tyre had dug in as my power had pulsed through the transmission. The 29er trail quite clearly showed how these power lumps had been smoothed out. Again, able to pick a line, I cleaned the final climb.

Only the downhill remained. Now here I have to say that of all three 26/29/69er incarnations this was the one that rocked! The forks could still have done with more travel, some of the manoeuvrability was gone due to the gyroscope effect of the bigger rear wheel, but at least I could pick lines and unweight the front. And the rear end did an excellent job of smoothing the trail. Not 2.75″ of rear travel smoothness, but definitely better than a pure 26er hardtail.

Ideally I would have now tried the bike in a 96er incarnation, but I was running short of time and needed to get home. I may get round to this, but right now it seems a little pointless.

I’m more convinced than ever that if there’s a benefit to be had from 29″ wheels they’re best at the rear. Slap some longer travel forks on the front with a 26″ wheel for manoeuvrability, wheel strength, lack of toe overlap, proper length headtubes, and gain the 29er smoothness at the rear on the downs.

Of course, you could just use a slightly longer chainstay on your steel 26″ hardtail to get mostly the same effect.

Thats some good real-life info Nick, it sounds like some of the "boring" handling was down to the trail given by the fork rake and wheel size, I guess by running 29 / 29 but with longer rake forks (rigid I guess....all the sussy ones are 38-39mm rake) to keep the trail the same as the 29r / 26f but with a bigger wheel.

If only suspension fork manufacturers had made 29er forks with 45mm+ rake to start with :rolleyes:

Its interesting that with a 26" rear wheel and long (by 26" standards) chainstays it still climbed well....there goes 20years of MTB magazine dogma :D My MC ute was a great handling bike but on paper the 17.5" chainstays should have made it climb like a dog!

Slapping long-travel forks on a 29r / 26f would reduce the head tube length a little, probably not as much as a suspension-corrected 29er (in your size...Phil is a special case!) as long as you stayed away from 120mm+ forks....if I get a chance to fire up BikeCAD I might play about with that idea. 100mm travel 26" forks are not far off the same length of 80mm 29er forks.....I wonder....

Keep up the mad-scientist experimentation and I'll see you at the weekend

Alex

definitely not 96

Last time I left you on the 29er front I was just off into the shed to fetch out a 26″ front wheel. (http://forums.mtbr.com/showthread.php?t=196263)

I pulled out a 26″ front wheel and tried it. The worlds second 69er.

Instead of looking like a Chopper or a Stingray it looked odd, but definitely no worse than any 96ers out there. Indeed, from the seattube forward it looked a whole lot better. My wife suggested I try two 26″ wheels in there. Not a bad idea. I could ride the bike with the same geometry and angles and the only difference would be bottom-bracket height and fork trail.

Hey! It looked like a well-proportioned bike again. Maybe the bottom bracket height was a bit low compared to what you expect, but it certainly didn’t look that odd.

So I threw the bike and the 29″ wheels in the car and headed off to reride Saturdays trails.

First of all I rode them in it’s 26″ incarnation.

At the front end it was noticeably quicker steering, like my old Spot or the Rocky Mountain Hammer when fitted with Pace RC-30s. Sharp then, but not twitchy.

The rear end was likewise transformed. It had some life, some snap, some feeling! Unsurprisingly, it didn’t smooth the trail out as much as the 29er wheel. It was also less smooth than my wife’s regular 26″ wheeled Spot which runs the exact same chainstay length. Which only tells us that frame material makes a difference. Tell us something we didn’t know!

On the rocky uphills it suffered no loss in traction. On the final climb, I not only rode it past the point where it had stalled on 29″ wheels, it made it clean to the top. Why? Because I could now choose where I wanted the bike to go and pick the smoothest line.

Now I was faced with the downhills, and I wondered briefly about the low bottom bracket height. I’d not had an pedal strikes on the way up, would it ground on the way down? Well, not on the steps it didn’t, so off to the more technical downhill I headed - the Ice Cream Run for those who care about such things. It’s not World Cup DH course technical, but it’ll do. It just felt more manoeuvrable underneath me, I could change lines, I could unweight or lift the front end better, and in the air I could make tiny corrections. With only 80mm of travel the forks had a busier time of it with the small front wheel but the lower unsprung weight and fatter rubber than my normal tyres meant things didn’t get out of hand. A pair of Fox Vanillas on there and I’ve have been laughing.

The rear end bounced around a bit, but followed eagerly enough, and the fatter rubber than I normally run made things better than my regular hardtail.

Back at the car, I checked no-one was around to point and laugh, swapped the rear wheel for the 29er version, and headed back out on the same trails.

At the front the steering was now bang on. There is something in those criticisms of the forks. If the regular 29er steered like this I’d have been a whole lot happier with it from the start.

At the back that old sluggish feeling was, um, back. Over whoops, where I wanted to maintain momentum down one side to get me up the next the 29″ rear wheel definitely helped. The Dirt Demo trails at Vegas with their rolling whoops are favourable to big wheels.

At the top of one climb I looked back and I could see where my two trails rode side by side. The 26″ rear wheel trail showed marked treads where the tyre had dug in as my power had pulsed through the transmission. The 29er trail quite clearly showed how these power lumps had been smoothed out. Again, able to pick a line, I cleaned the final climb.

Only the downhill remained. Now here I have to say that of all three 26/29/69er incarnations this was the one that rocked! The forks could still have done with more travel, some of the manoeuvrability was gone due to the gyroscope effect of the bigger rear wheel, but at least I could pick lines and unweight the front. And the rear end did an excellent job of smoothing the trail. Not 2.75″ of rear travel smoothness, but definitely better than a pure 26er hardtail.

Ideally I would have now tried the bike in a 96er incarnation, but I was running short of time and needed to get home. I may get round to this, but right now it seems a little pointless.

I’m more convinced than ever that if there’s a benefit to be had from 29″ wheels they’re best at the rear. Slap some longer travel forks on the front with a 26″ wheel for manoeuvrability, wheel strength, lack of toe overlap, proper length headtubes, and gain the 29er smoothness at the rear on the downs.

Of course, you could just use a slightly longer chainstay on your steel 26″ hardtail to get mostly the same effect.

29" wheel in back and 26" up front? that front end must have handled quick!

Usually people run them the opposite way with the small wheel in back for acceleration and the big wheel up front for smoothing things out and getting up and over logs and rocks and roots and whatnot.

Post up some photos sometime so we can have a visual of your experimentation process.

Sort of throws XX years of off-road motorcycle and cycling progression out the window. The increasingly steep HTA under damper compression is just frightening.

I just can't imagine it being of value other than for novelty.

Usually people run them the opposite way with the small wheel in back for acceleration

When you accelerate your back wheel, your front wheel will also accelerate by the same ammount unless:

a) The front wheel locks and skids across the ground, and then you are still accelerating it in a linear direction

or

b) Your frame gets a lot shorter as the back wheel catches up with the front!

I have not run the numbers but the linear acceleration of a human body would, I imagine, be more of a factor than a couple of hundred grams on the wheels....right, break out the calculator! :eek:

and the big wheel up front for smoothing things out and getting up and over logs and rocks and roots and whatnot

This is a factor but only really with rigid forks, with a suspension fork the suspension action should isolate the rider from the trail impacts, although a lower andgle of attack 29er wheel would help this / allow the use of shorter travel forks for the same percived comfort.

Post up some photos sometime so we can have a visual of your experimentation process.

Ah, but its a secret bike! :D

29" wheel in back and 26" up front? that front end must have handled quick!

No, with two 29er wheels this had been a barge - probably due to lack of offset in the RS Rebas - so with a 26er front wheel it was fine.

Sort of throws XX years of off-road motorcycle and cycling progression out the window.

Remember the Honda XL 500 and the fuss about that and it's piss poor handling when it came out? That was a 96er.

The increasingly steep HTA under damper compression is just frightening.

That's the sort of argument that was around back in 1996 when folk were saying that 80mm was long travel and beyond that we'd be pitched over the bars. Now we have 5" travel forks on modern day hardtails. On a 69er there would be no more change in HTA than on a regular 26" wheeled bike.

Usually people run them the opposite way with the small wheel in back for acceleration and the big wheel up front for smoothing things out and getting up and over logs and rocks and roots and whatnot.

I saved this 'til last because this is where I think the 69er scores over the 96er.

Which wheel do you mainly stall on obstacles? Me, it's usually the rear. The front I can unweight and finesse over obstacles more easily on a 26" wheel than a 29" wheel. At the front end of a bike the arguments between using a 5" travel fork and a 26" wheel versus a 3" travel fork and a 29" wheel come down firmly in favour of the long fork/small wheel for me.

At the rear the large rear wheel does provide that trail smoothing experience that folk are after. Not as well as short travel suspension and a 26" wheel, but certainly more efficiently. Ellsworths excepted, because we all know they're 100% efficient right?

And now I can save Alex some math. The energy possessed by a 26"/29" wheel combination is the same, whichever wheel is in back. The effort expended getting them up to speed is the same, whichever wheel is in back.

And now I can save Alex some math. The energy possessed by a 26"/29" wheel combination is the same, whichever wheel is in back. The effort expended getting them up to speed is the same, whichever wheel is in back.

Sorry Nick, my bad writing strikes again! As I said, both wheels need to be accelerated to the same linear velocity, so 29/26 or 26/29 does not matter!

I meant to compare 29/26 vs 29/29 vs 26/26 in terms of inertia / angular acceleration.

As a means of seeing how important it is in the over all system, calculate the total energy neded to accelerate the rider and bike as a whole....I am not sure how much more energy the bigger wheels would need, or if any other factors like rolling resistance / angle of attack would partially compensate for it.

If I am really bored tonight I might do this but I have a load of stuff to get ready for the weekend! At best I can calculate it based on a "perfect" model, ie perfectly smooth surface, solid tyres, rigid frame, no spoke wind-up....all those pesky real life things that get in the way!

Alex

Yeah, but MMcG seems to be implying that 29/26 has some advantage over 26/29. It doesn't.

It's funny how there are so many different opinions out there. I guess we all find what works for us from bike fit to brakes to tires to handle bars to suspension to no suspension to wheel size.
My experience is the exact opposite of Nick's. Is he wrong and am I right or visa versa? I don't think so. All Nick needs to do is to find a bike that works for him and it appears it is a 26er. Just make sure your wife likes it, is all I have to say. People have gotten divorced over much smaller matters!:D

Yeah, but MMcG seems to be implying that 29/26 has some advantage over 26/29. It doesn't.

I was just saying that the usual way to do the two different size wheels is to go with the smaller wheel in back and the larger up front.

I found it intersting that you went the other way with the big wheel in back and the small wheel in front.

I'd still like to see a photo of the bike in that configuration - it would be a new look for me to see and for many others on this board I presume.

How's about throwing up a photo or two Nick??

It's funny how there are so many different opinions out there. I guess we all find what works for us from bike fit to brakes to tires to handle bars to suspension to no suspension to wheel size.
My experience is the exact opposite of Nick's. Is he wrong and am I right or visa versa? I don't think so.

Bang on. There should be no such thing as dogma. At the end of the day it's all just riding bikes.

Just make sure your wife likes it, is all I have to say. People have gotten divorced over much smaller matters!:D

She rides the same size as me, so she has an ulterior motive :D

Is this the bike? or is this the other bike with the 29er in back and the 26er in front?

http://www.simonbarnes.net/tmp/69er.jpg

Perhaps that is the other bike since it looks like you are running a Reba up front based on the photo on your blog site.

http://www.32sixteen.com/26er.jpg

I'd love to see a full shot of your bike with the 29er in back and the reba with the 26er up front.

Nick, that bike whatever it is, is all wrong for you. Even with 26" wheels, the handling is too slow for your liken EVEN DOWNHILL. That's not good. You seem to like things nervous. Going from 26/26 to 29" Rear, steepens the angles on the bike by ~1.6º. More than there is a difference between 99% of all XC 26" offerings. Also, the front end becomes much more weighted. With a 26" rear wheel, 29" front, you're going to hate handling, as it's another ~1.6º slacker than 26/26, weight on the rear wheels to the front will wander on climbs.

You are now ready for a real bike. Demo an On-One Inbred29, it's got 29"-specific geometry and stuff. Don't tell us about it though, as we wouldn't know what you're comparing it to.

No, the On-One CX bike most definitely isn't mine, just someone that was poking fun at my initial 69er idea.

With a 26 in front of the 29er it was steeper, but not too steep. Front end was easier to unweight/lift with the small wheel.

I already have another 29er lined up that won't be subject to these wheel experiments.

Curious - but were you testing the bike out at the request of a specific manufacturer, hence the mystery behind the brand and all?

And will you be carrying out the reverse experiment on thie bike with the 29er up front and the 26er in back just for shits and giggles if nothing else?

This idea makes the most sense to me.

The only thing no one said was the fact that damping trumps rolling. A good fork will get you more that a bigger wheel in terms of smootheness. On a hard tail a big rear wheel will get you better rolling since there isn't any suspension.

If you have dual suspension, and a good design, and a good shock, I'm not sure I see the need for a larger wheel. But then I'm not sure I see the need for dual suspension. Or front suspension for that matter. I'm 100% sure I see the need for monkeying around with ideas though.

-M

Curious - but were you testing the bike out at the request of a specific manufacturer, hence the mystery behind the brand and all?

No, I was trying it out for myself, but my source of bike was dubious - though not illegal I hasten to add - and revealing it's identity could get other folk into trouble.

This idea makes the most sense to me.

The only thing no one said was the fact that damping trumps rolling. A good fork will get you more that a bigger wheel in terms of smootheness. On a hard tail a big rear wheel will get you better rolling since there isn't any suspension.

If you have dual suspension, and a good design, and a good shock, I'm not sure I see the need for a larger wheel. But then I'm not sure I see the need for dual suspension. Or front suspension for that matter. I'm 100% sure I see the need for monkeying around with ideas though.

-M

Agree absolutely.

Rigid, hardtail or suspension depends on the trails for me and whether I'm out for a quick on the ragged-edge blast, or some all day trail comfort.