The TFB Blog

Wheel sizes for shorter riders – part 3

27.5 – 29er – Mullet. Which is the suitable wheel size?

In the previous two parts, I was talking about possible injuries because of components and how I tested three wheel sizes to decide whether or not the Mullet was the way to go for me.

How to turn your bike into a Mullet?

I made the mistake of starting to read blogs by keen weekend warriors, who calculated everything on paper and were adamant about certain fork travels (and certain things in general). These blogs left me more confused than enlighten. As an ex-elite DH racer, who after retirement looked after the Australian National DH team for 2 years, I thought I should resort to some of the trusty Aussie pro racers. I will not start name dropping here, but contacted three of them who I knew had experience with Mullets. Two of them came back with – “you are just over thinking it, put the smaller wheel in it, start riding it and do the changes as you ride it.” These boys are regularly in the top 10 at world cups & it just shows we need to be a bit more flexible sometimes. Of course, they have the fine skills to adjust to anything using their extraordinary abilities, to the point where they would be quicker than most of us even on a Kmart ‘bike’. So, maybe we do need to be particular with our set up, but not as much as some of the bloggers.

Anyway, I have tried to put together a digestible journey of my transition from 29er into a Mullet. Here we go:

It is cheaper to turn a 29er into a Mullet. In my opinion, what you need to consider are the head tube angle of the frame, offset of the fork and the length of the cranks.  I ordered a 2020 Giant Reign Advanced 1 29er, small size. I knew I would not use the rear rim, so instead of a whole wheel, I just purchased a 27.5” rim and spokes through my local shop and Cycle Station Albury built it up with the original hub. When you are downsizing with the rear wheel the geometry will change and the bike ends up with more rake angle at the front. More rake means more trail, and if you have an enduro bike, that will create an even more sluggish steering feel. My Giant Reign came with a 65 degree head tube angle, which makes it stable and raked out enough already, before adding the ‘mullet factor’. Therefore, I checked the offset of the fork, to see if that had any potential. It is a Fox suspension unit with a 51 mm offset fork, which means the rake is the steepest possible for that brand and make the bike nimbler & closer to the feel & manoeuvrability of a 27.5” steed. It is worth noting here that we now have the option in general terms, of ‘slackening’ our bike any time we want (for steeper terrain), should it have 51 mm forks as standard; by changing to front suspension with 42 or 44 mm offset. Not an issue in my case because I am looking in the other direction with this mullet.  If you are unsure about the offset of your existing Fox fork, there is a 4 letters ID on the left lower leg, close to the seal. Visit the Fox website, punch the numbers in and it will let you know what your offset is. The other major brand is Rock Shox & they have the offset on the fork at the right lower leg side under the seal. Rock Shox 29” forks have the choice of 42, 44 or 51 mm. I am not familiar with the rest of the fork brands, so if you have anything else other than Fox or Rock Shox, please do your own research.

Although my new bike arrived with a good set up for ‘mulleting’- aka the steepest fork offset with a good, stable head tube angle; I was concerned about the bottom bracket drop that results from fitting the smaller rear wheel. I rode a Rocky Mountain Instinct demo bike for over a month as a Mullet set up and even with the steepest Mino link setting in the frame, the pedals often caught on rocks while I was pedalling. A new phenomenon, that rarely happened before. So, I opted for an angled headset on my new ride. Most of the manufacturers who produce angle headsets bring them out in 0.5, 1 or 1.5 degrees range. I got the 1.5 degree headset, and the cup has been set up to increase or steepen the head angle on my Giant Reign and that therefore brings the bottom bracket higher up. I had twelve 10 plus km rides on it in the last 3 weeks and it looks like the offset headset has eliminated any possible pedal bashing. If you still have a problem with pedal clearance, I would recommend opting for shorter cranks. Mine arrived with the shortest length, 165 mm being the fitting for the small frame; with medium frames generally fitted with 170 mm and large frames with 175 mm length cranks.

On the crank length, obviously there is reason for the different lengths, but studies have proved that going shorter with cranks length does not negatively affected riding performance. For us, MTBers who are constantly in & out of the saddle, as well as changing pace and gears all the time; a shorter crank can even be beneficial.

Turning a 27.5” bike into Mullet

You need a 29”er fork, otherwise you will have clearance issues with the 29”er wheel and the lower leg arch of the 27.5” fork. Again, it is important to look at the head tube angle of your frame to decide which offset you need to order. Hopefully, you read my rumble about turning a 29er into Mullet above, if not please do, more info about geometry there. Obviously, you need a 29” front wheel or a rim and longer spokes to use with your existing front hub. With the new fork and bigger front wheel, the geometry will slacken, and you will end up with bigger trail and more sluggish steering. An angled headset may come in handy here too, however that is just in relation to steering; as there is less of a concern around the pedal clearance, as the bottom bracket ends up higher.

Just for the record, I got a Works Components branded angled headset, being half the price of Cane Creek. Time will tell if the quality is half as good or not. When you purchase an angled headset, you will end up with two settings. In my case, we set to steepen the head angle but if I flip the top head cup around the head angle will slacken. I will try the latter set up on steep trails, like Bright or Thredbo to work it out if it is suitable to my riding style there.

Thank you for Roger Derrick for editing my writing, Beau Proctor & Darcy Wilkinson from Cycle Station and my Hunstrian friend – Matte Cser with the initial bike set up and parts order.

Wheel sizes for shorter riders – Part 2

27.5 – 29er – Mullet. Which is the suitable wheel size?

Hopefully, you read the first part of my post from last week. If not, I highly recommend doing so. I was talking about the occurrence of injuries because of low cadence – hard gear pedalling and components which may prevent it. Also, I established my credentials that hopefully, enable me to rumble about things like that. In this second part, I will write about the results of my 3 months of testing of 3 different wheel configurations.

Being a racer and coach, hard facts and numbers are everything for me. I did all the testing back to back, using the different bikes on the same track on the same day. In 4 MTB parks, 10 familiar enduro tracks were used at pretty much race pace. Time recorded by an action camera mounted on the handlebar. Bikes were not tested on pure, dedicated climbing tracks. Both test bikes are 140 – 160 mm travel and with these types of MTBs you tend to just get it done on the uphill bits and you are not aiming for being the best climber in town.

I can’t publish a paper of my testing because I could not use the same models for my ‘experiment’. For 27.5” bike I used my own race bike for 2 years, a Giant Hail Advanced 0 with 160 mm travel. For 29”, I used the demo bike, a Rocky Mountain Instinct with 140 mm travel. For Mullet, I used the rear wheel from my 27.5” seamlessly fitted into the 29”er. However, my aim was not to write an article or publish a paper but to test the handling and manoeuvrability of different wheel sizes for my clients and possibly settle for a different bike for myself. I found the results so interesting, I thought I should share with TFB’s followers. So please, read it with this in your mind and refrain picking on different tyre compounds, geometries, or brake brands etc.

Handling differences of a 29”er compared with my usual 27.5” wheel set up:

29”er felt very measured, almost as the trail features were coming up in slow motion. I like to spin, so I had to shift more often otherwise stuck in a hard gear too long out of corners. I was game to enter rock gardens faster because the bigger wheels felt they were rolling over rocks with more ease. I had to be more aggressive with the initiation of the turns but once the front wheel was in the corner, it was tracking with more stability & I had to do fewer fine corrections. Being 164 cm, the rear wheel zipped on my bum a couple of times on very steep sections, which is unpleasant and sometimes frighting, even though I don’t need to worry about jiggling man parts 😊.  Also, on very tight turns, I really had to swing my body sideway to make sure I will make the corner. On high speed jumps (talking about over 40 km/h) the front end was rotating forwards more than I preferred but assumed that with a change in body position, I could get used to it over time.

Time wise, the 27.5” and 29”er were in the same second on 4 trails out of the 10. For Riverina locals: ‘Generator’ & top half of ‘Flow Town’ at Falls Creek and ‘Short Course DH’ & ‘Don’t Be a Hero’ at Beechworth. These 4 trails have combination of big, smooth rock roll overs, fast open sections, and some quick direction changes.

The 27.5” was faster on two trails, ‘Glock to Home Run’, which is the most technical descend in Albury. The other one is ‘High Voltage’ at Falls Creek. Both trails are very busy, constantly corners and rock features are coming up.

The 29”er was faster on 4 trails. ‘Vortex’ and bottom half of “Flow Town’ at Falls Creek and ‘Rock n Roller’ and ‘Hunchy loop’ at Wodonga. These trails are more open and high speed. Also, the elevation is greater so, instead of pedalling out of the corners, often enough just let the brake off earlier and the bike picks up the speed instantly because of the steep terrain. I could get off the brakes earlier, because the more stable front wheel feeling in the corners.

So, both wheel sizes scored well and have pros and cons but you, the reader, probably knew this already. Numerous articles have been written about the two wheels sizes, although not too many from a short rider, under 172 cm perspective.

And then the Mullet testing:

I was planning to get a new enduro race bike, but I was not overly sold on the 29er. I checked the hub and axle width and my 27.5” rear wheel smoothly fitted into the 29er, creating a Mullet. It was mid – March and the Covid – 19 travel restriction arrived, with the closure of the Falls Creek MTB park. It reduced my testing trails to 5 but still left me with a good variety of tracks to test on.

The handling of the Mullet was the best of both worlds. The stable, almost slow motion feeling of the 29er had been kept but without the sluggishness. I have an aggressive riding style with good core strength, to keep the bike fast and leaned in a corner but don’t have the acceleration leg strength of a man. However, with the 27.5” rear wheel I do not have to, as the exit speed stayed the same lively set up that I was used to. Although I had the same branded cassette with the same gear ratio on both wheel sizes, I always felt between two gears with the 29er. Either too much spinning or too low cadence. Of course, this can be fixed with a different front chainring, but can take toll on the hardest gear set up. Anyway, this feeling was completely eliminated with the 27.5” rear wheel. Other positive handling point was jumping. I always felt the 29er too long on the jumps and had to initiate the bike press earlier to get the desired height or length. Certainly, with a changed riding style, I could get used to that but the 27.5” rear wheel flicks around with more ease; so why would I?

Mullet timing:

All right, this wheel set up feels good but what does the time say? The Mullet was FASTEST on all 5 trails. The time was between 2 & 15 seconds faster, depending on the length of the test tracks. On the ‘Short Course DH’, a bit longer than 2 minutes trail the Mullet was 7 (!) seconds quicker than the two other wheel sizes. This is when the video timing comes in handy. I put the onboard footage of the 29er and the Mullet side by side and started the video together to work it out where I gained this huge advantage. This Beechworth track has a looooong rock garden. Maybe 400 m long. Starts with small rocks and ends up with step downs while the rider needs to change direction to avoid boulders and trees. I advanced around 5 seconds in that rock garden because I could manoeuvre the smaller rear wheel around. Another 2 seconds was taken off the clock in 3 fast but flat corners with jumpable rollers between them. I could accelerate out of the corners quicker and keep my speed up to be able to jump the rollers.

Decision made, I will have a Mullet as my new enduro race bike! Being a reasonably new phenomenon, the next question raised. Do I turn a 29er or a 27.5” bike into a Mullet? What different parts I need to keep the geometry? Do I need to set up my suspension differently?

My findings will be in part 3. Stayed tuned for next week…

Wheel sizes for shorter riders – Part 1

27.5 – 29er – Mullet. Which is the suitable wheel size?

This multiple part post will consider the needs of an emerging, but it seems to me, slightly forgotten market: riders under 172 cm – which is realistically majority of females and junior boys under 14.

I will start with an intro about myself, for non The Fastline Bikademy (TFB) clients.

I am an OG MTBer, who started riding in 1993. A DH / DS & 4X World Cups and Champs veteran, with world cup podium, continental champion and multiple Word Games and I have a National Champs title under my belt. In the last couple year, I started GE racing. At the age of 40, I still won the Australian GE national series in elite women. I am a full time MTB coach, my skills coaching company – The Fastline Bikademy is working with an average of 70 kids weekly ; age between 8- and 18-years of age. I also have a Bachelor of Science degree specialising in coaching, which allows me to work with higher level gravity athletes. For years, I looked after the Australian U19 and non-professional elite racers in the downhill national team. My height is 164 cm or 5.4”. I am a bike brand ambassador, but I am not obliged to push the product. TFB only works with brands which we are happy with and ones we can form honest opinions about.

What wheel size?

For years I swore 27.5” wheels were the right choice for junior riders up to age 16 and ladies with average fitness.

In road bike racing, the large chainring gets locked out until generally age 16. In BMX Cross certain chainring / sprocket / crank length are recommended for certain ages. Both disciplines try to promote spinning, aka higher cadence for the juniors. However, to my knowledge, there are no gear restrictions or chainring recommendations in MTB racing.

The idea behind spinning is that the majority of the juniors don’t have good leg stabilizer muscles. Asked them to do a squat for you and their legs will act like a baby giraffe’s. They will go in any angles except straight up and down. If a junior pulls a hard gear, their legs are working against bigger resistance. With weak leg stabilizer muscles, instead of the power transfer straight to the pedals, it is partially lost & the body functions will suffer. The flexible parts, such as ankles – knees and hips will give in and start moving sideways. It may cause ligament and joint strain with juniors, particularly if they are doing longer distances for training. Not ‘pleasant’ injuries for anybody but particularly not for growing bodies. Also, higher load aka hard gear – low cadence pedalling fatigues muscles quicker. Adults are not safe from injuries like this also. I often see baby boomer riders with side way flexing knees because after years away from any sport, they discover cycling, but their leg stabilizers have wasted away. If you recognise yourself or your child from the above description, please see a physio, fitness or MTB coach and ask for help with strengthening your leg stabilizers.

Beyond changing your cadence, you can do some modifications on the bike as well. What also can slow the cadence down is chain stay length, wheel size, crank length and chain ring size. The longer or bigger are these parts the more chance to pull a harder gear by accident. In numbers, 470 mm length for a chain stay is considered to be long. Crank lengths generally are 165 – 170 or 175 mm on MTBs. To promote spinning I would recommend a 28 or 30 tooth chainring on a 1 x 12 gear with a 10/50 cassette. And then the wheel size. For years I used and recommended 27.5” wheel bikes for juniors and recreational female riders. Adult ladies with average fitness tent to spin more because harder gears fatigue the muscles quicker and they often have less muscle mass compared with their male counterparts.

However, with the refined geometry of the newer 29” bikes and the appearance of the Mullet (29” front – 27.5” rear wheel), I was keen to do some testing. Luckily for me, my trusty local bike shop Cycle Station Albury, organised a demo bike for 3 months. So, which is the suitable wheel size for junior riders and riders under 172 cm?

Please stay tuned and next week I will discuss the results of my 3 months testing of the three wheel sizes.