Why is 29 faster than 27.5?

“You can’t gain speed by riding into a dip because you will lose it as soon as you climb out the other side, all this will do is throw you off your pedaling and slow you down.”

????!!!!

You pump into the dip and you suck/pull the bike out of the dip. You’re not pedalling but you’re putting energy into the bike with your whole body, to generate/maintain speed. Pumping is one of the most fun and flowy things in mountain biking and the allegedly reduced pump from bigger wheels is what put off moving from 26 to 27.5 to 29.

However, I think on all but the smoothest trails I prefer how a 29 pumps vs smaller wheels because the “noise” of little bumps/rough is flattened more, momentum is maintained more and you can get on with the fun of pumping the trail. 29″ singlespeed hardtail (with a long dropper post so you can MOVE) is just so much fun on singletrack for this reason.

^^ this is literally pumping in and out to increase speed right?

if unsure, Ben Cathro did some nice videos on it

Pumping is one of the most fun and flowy things in mountain biking

Totally agree.

I find myself trying to pump everything on the trail (gigidy).  No depression or bump is safe and especially in corners I love unweighting on entry and then driving the wheels into the dirt and either drifting or making that nice schralpy sound (or crashing).

I probably look like a chimpanzee having a seizure but I’m having fun which is the main thing 🙂

I found in the transition from 26 (HT and FS) to 29 that the 29 climbs better, rolls better but takes a bit more thought and energy to turn. It’s like there’s more forward momentum keeping a straight line.

Smaller wheels can feel more able to generate speed from downslopes in places but you’ll lose momentum more easily in others. You put in energy to gain speed that you lose elsewhere – zero gain on an average trail (no such thing but you know what I mean). It’s very terrain-dependant outside of a BMX track. Or it’s about how long you ride for and can keep up that bump-pumping riding style.

I’m not even sure if it’s the wheelsize that does it, there’s the reduced BB drop and rear-centre of a smaller wheel bike to think about. If the BB to axle relationship was the same and the wheel weight was the same, the pump could/should be the same – but who’d want 29″ wheels on a pumptrack or 4X course because of the corners, or the longer forks, etc.

You pump into the dip and you suck/pull the bike out of the dip. You’re not pedalling but you’re putting energy into the bike with your whole body, to generate/maintain speed.

If you want to go fast, pedal the bike. When you have a choice of skirting dips and pedaling across the flattest line available or deliberately seeking out dips and pumping, you’ll use more energy and go slower if you pump rather than stay seated and just pedal as hard as you can. Go to a pump track and compare your lap time pedaling with no pedaling.

“If you want to go fast, pedal the bike. When you have a choice of skirting dips and pedaling across the flattest line available or deliberately seeking out dips and pumping, you’ll use more energy and go slower if you pump rather than stay seated and just pedal as hard as you can. Go to a pump track and compare your lap time pedaling with no pedaling.”

I’m not being paid to win races, I’m riding my bikes for fun in my free time. So I shall continue to ride the way I find most fun – which will involve a lot of pumping!

The joy of a 29″ singlespeed hardtail is that it rewards a fun riding style, conserving energy you’ve generated from pumping, converting pumping energy into forward momentum well thanks to the lack of rear suspension, and once you’re going at a decent speed downhill you can’t add speed from pedalling because the gearing is too low, so having fun and not chasing times is the only way to ride it.

I will add that on most of our local singletrack, there is essentially no choice of line. There are a lot of tight corners and ups and downs that can’t be pedalled, so pumping pays off!

Go to a pump track and compare your lap time pedaling with no pedaling.

That’s certainly a unique take.  Have you actually done that?

I haven’t but this is the closest I could find on YT:

If you want to go fast, pedal the bike. When you have a choice of skirting dips and pedaling across the flattest line available or deliberately seeking out dips and pumping, you’ll use more energy and go slower if you pump rather than stay seated and just pedal as hard as you can.

You’re absolutely right, this is why world cup downhill racers pedal out of the gate and don’t stop until they reach the finish line.

Maybe there’s a definitive answer on this thread?

Things that are allegedly ‘science’, but are self-evidently magic

They must be the fastest option otherwise someone in the XCO field would be taking advantage of running 27.5. When was the last time a top level xx race was won on 27.5.
Whether you prefer them or no is personal taste but there’s no denying they are quicker.

I’m not being paid to win races, I’m riding my bikes for fun in my free time. So I shall continue to ride the way I find most fun – which will involve a lot of pumping!

This thread is about whether bigger wheels are faster than smaller wheels, not whether they are more fun. In general, they seem to be faster. Pumping might be fun, but if you want to go fast and have the choice between pedaling across a smooth line and taking a detour to stop pedaling and pump, pedaling will get you there faster.

Whether you prefer them or no is personal taste but there’s no denying they are quicker.

If you want to primarily pedal and you are travelling over rough terrain then I don’t think there’s much question that the answer is the bigger the better.

However, the question wasn’t why is 29 faster in XC racing.  29ers don’t dominate all forms of mountain bike racing.

As I posted earlier, when people have made the effort to keep as much as possible the same and just change the wheel size the actual difference on the clock is marginal.  The difference in feel is more noticeable than any actual increase in speed which makes sense because there is no ‘correct’ wheel size.

You get roughly into the right range of sizes and then it’s a question of compromises to achieve the performance characteristics you want.  Same as any other component on the bike.

“Go to a pump track and compare your lap time pedaling with no pedaling.”

If you’re faster pedalling your doing something wrong.

As I posted earlier, when people have made the effort to keep as much as possible the same and just change the wheel size the actual difference on the clock is marginal.

Most of my bikes are still 26ers, with a 27.5 XC hardtail and 29er commuter hardtail. On my regular training loop, the 27.5er is marginally faster on the road climb (about 20 seconds over 15 minutes) and my old 26″ Anthem quite a bit faster on the descent (about 45 seconds over 7 minutes, all down to better braking over rough stuff). If I was racing, I’m sure that something like a 29er Anthem would knock 30 seconds or so off the overall time, those marginal gains matter if you are racing. I don’t race so I’m not going to spend the money to upgrade to save 30 seconds.

If you’re faster pedalling your doing something wrong

If not pedaling was faster, bikes wouldn’t have chains.

if you’re good at pumping its much much faster over some kinds of terrain (eg a pump track). On the flat it doesn’t help you at all. most mountain bikers are terrible at pumping and can barely do a lap of a pump track without pedalling. if you’re bad at pumping, then yeah, pedalling is quicker

If not pedaling was faster, bikes wouldn’t have chains.

like this?

re, just watch the pump track races at crankworx

the amount of speed they produce on a chainless bike is insane… i don’t think that if i i had a chain on the same course i would be anywhere near them

Most of my bikes are still 26ers, with a 27.5 XC hardtail and 29er commuter hardtail. On my regular training loop, the 27.5er is marginally faster on the road climb (about 20 seconds over 15 minutes) and my old 26″ Anthem quite a bit faster on the descent (about 45 seconds over 7 minutes, all down to better braking over rough stuff). If I was racing, I’m sure that something like a 29er Anthem would knock 30 seconds or so off the overall time, those marginal gains matter if you are racing. I don’t race so I’m not going to spend the money to upgrade to save 30 seconds.

this is what I love about UK mountainbiking, on such a small island we have an amazing variety of terrains (and therefore variety in ideal bike)

Just from this paragraph we have found you have a local 20-25 minute loop with a single tarmac climb and single continuous descent. Your descending speed is only double your climb speed so unless you are climbing like a pro roadie that means the descent is technical enough to be a challenging technical affair and not fully a downhill seated pedal-fest.

Yet the limit to your descending speed is better rough terrain braking of a full suss – so presumably there are parts where you can go quite fast followed by bits where you need to slow, and the ability to brake later or better gives you the ability to hold a better speed on the faster bits.

7 minutes is a long time to be riding at your descending limit*, I wonder if the full suss is less fatiguing even with smaller wheels.

*there’s only 2 ways to make a reasonable stab at comparing your descending speeds against yourself. Either do it as fast as you can, or do it as a pure no-pedal roll down.

If not pedaling was faster, bikes wouldn’t have chains.

On the kind of trails I enjoy pedalling isn’t usually an option.

If I was forced to go round in circles on an XC bike I’d quit riding.

You can’t gain speed by riding into a dip because you will lose it as soon as you climb out the other side, all this will do is throw you off your pedaling and slow you down.

Have you not heard of a pump track?

Just from this paragraph we have found you have a local 20-25 minute loop with a single tarmac climb and single continuous descent. Your descending speed is only double your climb speed so unless you are climbing like a pro roadie that means the descent is technical enough to be a challenging technical affair and not fully a downhill seated pedal-fest.

Yet the limit to your descending speed is better rough terrain braking of a full suss – so presumably there are parts where you can go quite fast followed by bits where you need to slow, and the ability to brake later or better gives you the ability to hold a better speed on the faster bits.

7 minutes is a long time to be riding at your descending limit*, I wonder if the full suss is less fatiguing even with smaller wheels.

That is an excellent analysis. I am impressed. Yes, a very technical descent, some fast parts, some slow tight stuff, some sandy sections, some rock gardens, fast sections braking across roots into tight corners, etc. A 26er with a short wheelbase helps massively through the tight stuff. Being able to brake late into the corners really makes all the difference, that’s where the hardtail just loses a fraction of time on each corner.

On the kind of trails I enjoy pedalling isn’t usually an option.

If I was forced to go round in circles on an XC bike I’d quit riding.

I enjoy doing both (and actually my local is probably part way between the two).

Now if I was forced to ride round a flat XC loop on a long travel monster with soft DH tyres, that would make me quit riding.

Have you not heard of a pump track?

We’re not talking about pump tracks, we’re talking about riding normal trails. If you pedal into and out of a dip, the energy you gain going in is lost on the exit. If you avoid a smooth pedaling line to divert to something you can pump, you stop pedaling to pump it and you’ll go slower than if you pedaled across the smooth line. The idea that a smaller wheel will make you go faster because you can pump out of dips is just silly unless you only want to ride around pump tracks. Bikes have chains and gears because pedaling is a much faster way to get nearly anywhere than pumping.

Yes, a very technical descent, some fast parts, some slow tight stuff, some sandy sections, some rock gardens, fast sections braking across roots into tight corners, etc. A 26er with a short wheelbase helps massively through the tight stuff. Being able to brake late into the corners really makes all the difference, that’s where the hardtail just loses a fraction of time on each corner.

sounds amazing. if that was my local terrain I’d be doing 2 or 3 laps a night all summer. My bike collection is a Bird 29 hardtail and Santa cruz 5010 130/140 travel full suss. I’d take the santa cruz for I guess the same reason – short and agile by modern standards but probably long and ponderous if you are judging against a 26er anthem.

If you avoid a smooth pedaling line to divert to something you can pump, you stop pedaling to pump it and you’ll go slower than if you pedaled across the smooth line.

Well, yes, if you ride like me and pinball around the trail looking for stuff to pump through then you will probably arrive at the bottom slower.

But at the same time if you divert away from the bumps and dips so you can keep pedaling then you’ll also get to the bottom slower.

However, if you ride like a regular human and just take advantage of the natural undulations you’ll probably end up going faster and/or use less energy as Neil Donoghue showed in the video I posted above.

But as someone else said above, most mountain bikers aren’t great at pumping. Probably because they don’t practice it enough.

If you can’t do something then there is no doubt you are going to be faster if you stick to the thing you can do.  But in the long term, avoiding developing all your trail riding skills is going to lead to you being slower than someone who does take the time to develop a complete skillset.

And I think the reason bikes have chains and gears is because it’s pretty much universally accepted that pumping up a hill or on a smooth road is pretty tough rather than because it is faster in absolutely every situation you will find yourself on a mountain bike.

I was a late one to change from 26 to 29, but can’t see me ever going back. But definitely understand that smaller wheels suit other folks more.

I definitely get plenty of extra speed by pumping along an undulating trail compared to just seated pedalling. Allows you to be more ready to get the odd bit air too. Smaller bikes (with no suspension) are better at pumping, hence bmx racing on snall wheels.

However, if you ride like a regular human and just take advantage of the natural undulations you’ll probably end up going faster and/or use less energy as Neil Donoghue showed in the video I posted above.

Sure, but the benefits from a smaller wheel on pumping are so insignificant that they make no difference on overall speed compared to the faster rolling of a bigger wheel. It’s fine to enjoy pumping, but this thread is about which wheel size is faster. I think the evidence is that a 29er is slightly faster overall, but it will depend on the particular trail. Having the right tyres for the conditions and optimal tyre pressures will make more of a difference than the wheel size.

“Bikes have chains and gears because pedaling is a much faster way to get nearly anywhere than pumping.”

I’ve never seen any evidence of people pumping bikes before pedals or chains were fitted to bikes in the 19th century – what a silly statement, peak STW?!!

I (and much more talented riders than me) will continue to use a mix of pumping and pedalling (bear in mind that you pump corners as well as humps and dips) to ride fast/fun/smooth/controlled/etc down trails.

I (and much more talented riders than me) will continue to use a mix of pumping and pedalling (bear in mind that you pump corners as well as humps and dips) to ride fast/fun/smooth/controlled/etc down trails.

Sure, but it’s a marginal gain. Nobody chooses their wheel size based on pumping, the main consideration is rolling resistance (i.e. pedaling efficiency) compared with packaging/geometry/bike handling. That’s what this thread is about. 29″ seems to be a good compromise, rolls well but not too unwieldy. The contribution of pumping over a multi-hour ride is so tiny that it’s not a consideration for the overall speed.

Sure, but the benefits from a smaller wheel on pumping are so insignificant that they make no difference on overall speed compared to the faster rolling of a bigger wheel.

Sure the benefits are small but I suspect someone (think it was jameso) may have nailed it when they said it’s less to do with the wheel size and more to do with the shorter wheelbase.

I’d argue that it’s the same with the bigger wheels.  Yes, there is some improvement in roll over but these differences are eclipsed by the fact the wheelbase is also generally longer on bigger wheeled bikes along with the multitude of other geometry changes.

Wheel size is one small factor in terms of how fast a bike is but for some reason it has been held up as an example of an absolute.  Very few people would argue that a 2.25″ tyre is faster than a 2.4″ tyre. Or that 150mm of fork travel was faster than 140mm.  Most would say you pick what’s right for you and the trails you ride.

I can’t think of any other component where people are so adamant there is a ‘right’ answer to what is faster.

The contribution of pumping over a multi-hour ride is so tiny that it’s not a consideration for the overall speed.

Last time I was somewhere with a chairlift pumping was very much my preferred mode of propulsion.  Could have quite happily ditched my chain.

In fact. last time I was on a local ride I snapped my chain.  I just kept riding for another hour pushing up and pumping down.

Yes, there is some improvement in roll over but these differences are eclipsed by the fact the wheelbase is also generally longer on bigger wheeled bikes along with the multitude of other geometry changes.

How does a longer wheelbase make you faster? A larger wheel will have lower rolling resistance but a longer wheelbase won’t change the efficiency of your pedaling. If it did, racers would have run much longer wheelbases.

I can’t think of any other component where people are so adamant there is a ‘right’ answer to what is faster.

It’s not that there’s a right answer, it’s that there’s a best compromise for most situations. If you look at F1 (literally, now), the Monaco GP is basically a race around an expensive gated community. If teams could design a car specifically for that circuit, it would be completely different to a car optimized for Silverstone or a car optimized for Monza. But they can’t so they have to design a middle of the road car that works on fast circuits and slow circuits, and then they adjust is as best they can for each track (so, for Monaco, they run the biggest wings they can put on because it’s such a slow circuit.)

It’s the same with bikes, if you designed a bike for enduro racing in the Swiss Alps, it would be quite different from something optimized for XC racing in a jungle in Malaysia. But, you can’t design a different bike for every situation, you have to choose one basic design that works reasonably well across the full range of contexts. It’s not that 29ers are the “right” answer, it just seems like they are a good compromise. (Coming from someone who mostly still rides 26ers because the gains from a new bike would be so marginal that they would make no difference.)

 I just kept riding for another hour pushing up and pumping down.

If pumping beats pedaling, why didn’t you pump up the hills?