New to MTB Buyer’s Guide – Wheel Size, Travel & Suspension
Welcome to the second section of our New to MTB Buyer’s Guide. Missed the first? Jump back to it here. Ready to start looking at the actual components? Well here we go.
Let’s go over the key differences on a mountain bike setup.
New to MTB Buyer’s Guide – Wheel Size, Travel & Suspension
Wheel Size
Modern bikes feature 27.5″ or 29″ wheels. It used to be a world of “taller than X’ Y” you’re on this wheel…” Not anymore. Updates in bike geometry and design have produced bikes which cross over height, within reason.
The 27.5″ wheel is considered more “playful and poppy” on trail. It’s smaller radius will “re-accelerate” a bit more quickly as it has less weight leverage. Typically they have slightly smaller wheel bases (distance between the front and rear wheel) although these tend to be converging a bit as well. Riders in very steep terrain may prefer the 27.5″ wheel as they can get a bit lower on the bike. Riders who are say, 5’8″ or smaller and plan on riding aggressive terrain should consider the advantages of the 27.5″ wheel.
29″ bikes have developed from names like Yeti’s “Big Top”, the name playing on the 29er’s “circus wheel” size at the time to the production of Yeti’s SB130 an SB150 – acknowledged class leaders. Guess the 29 wasn’t a circus setup after all! 29ers popularity has grown exponentially over the past few seasons. This is thanks to updates in geometry, suspension and tires. Modern 29’s can be just as much at home in the steeps as the smaller wheel options. They roll over obstacles more easily due to the increased wheel radius. 29ers might take just a little bit more to turn though. This factor isn’t as noticeable in the longer wheel base L or XL offerings. Which has more and more riders over 5’10” landing on the 29’s even for aggressive riding. 29″ wheels are faster across the flats as they maintain speed better.
There’ isn’t hard line in the sand as much with wheel size. Your height, riding style (or aspirations if you’re totally new) as well as terrain factor in. A 5’4″ rider may enjoy the forgiveness of the larger 29″ wheel while a 6’4″ might like the poppy, playful feel of the 27.5″.
Wheel size is a good place to ask questions of a qualified resource to help define what setup you’ll enjoy.
The Ibis Ripmo is a chassis at home in Trail / Enduro as well as light All Mountain riding. Ibis utilizes DW suspension and this frame has the Fox X2 rear shock.
Frame
The frame of a mountain bike consists of the front and rear triangle as well as the suspension linkage and shock. Most of a bike’s personality comes from the frame geometry and suspension.
Suspension Travel
Travel refers to how far the wheels move between full extension and full compression. The amount of travel, from industry leaders like Yeti, Ibis, Alchemy & Transition, dictate the type of riding style or terrain the bike is designed for. Lesser brands may have to run more or less suspension per category to make up for design inefficiencies.
Due to 29″ wheels providing a feeling of “false suspension” from the larger wheel / tire combo a 29″ Enduro bike tends to have 15-20mm less travel than a personality equivalent 27.5.
Newer riders often look at smaller travel bikes with a “I’m not going to push it that hard” mentality. I tend to prefer to slightly over-bike, or at least over-tire a newer rider. A bit more traction from the tire and forgiveness in suspension is great for the learning curve confidence. I would rather run out of talent than travel personally!
The most popular bikes are Trail / Enduro style these days. Bikes in this category are designed to be efficeint pedaling bikes with plenty for the downhill. Cross Country / Trail bikes are the second most popular. True Cross Country, or XC bikes, tend to be a bit nervous for new riders.
This Alchemy Arktos 27.5″ frame utilizes Sine Suspension design with a Fox DPX2 rear shock.
Rear Suspension
Not all suspension works the same. The best are confident riding platforms across a wide range of speed and skills.
Suspension system is designed to be plush over the small bumps while supportive in bigger, gnarly terrain. Add the need to be quick and efficient when pedaled! Balancing it together is the difference between the have and the have not’s in the suspension world.
DW, Switch Infinity and Sine Suspension each allow a central riding position while controlling both front and rear wheel wheels.
Less balanced designs require riders to move around much more depending on the conditions. This can be disconcerting particularly for newer riders.
Want to learn more about suspension? Here’s our first “rabbit hole” set of links for you!
Progressive versus Linear MTB Suspension: Falling/Rising/Mixed Rate Mechanical Design
DW Suspension (Used by Ibis Cycles) Extended Test Ride
Switch Infinity Suspension (Yeti) Extended Test Ride
MTB Suspension Setup
The SB150 is the longest travel 29″ offering from Yeti. This bike is shown with the X2 rear air shock but it can be built with the DHX2 Coil as well.
Rear Shock
Along with the mechanical design of the suspension a quality damper is important. Shocks will have rebound as well as air pressure (unless it is a coil spring) adjustments. More advanced models will have compression settings and even high and low speed adjusters as well.
A poorly performing shock absolutely will compromise suspension’s performance. However, even the best shock is extremely hard pressed to fix mechanical suspension designs.
An oversimplified look in a shock: air spring to support your weight at a % of sag into the travel. Hydraulic rebound and compression circuits to control shaft speed in and out. How complex the tunes are vary – but that’s what’s going on in there.
Ironically marketing a magic bullet shock isn’t unfamiliar in our world. I believe it is Trek’s new shock that claims F1 racing parallels. Now, I like F1, but even as a MTB rider and F1 fan I can’t come up with any similarities. Just marketing goobly goop. I know I wasn’t thinking “plush, compliant performance” when Vettel flat spotted his tires in Bahrain this year AND THE VIBRATIONS RATTLED OFF HIS FRONT WING. Look as I might I also can’t find the heave damper on any of Trek’s models although I suppose we only have 2 wheels not 4…
In short it’s important to balance the suspension performance with the shock.
Rabbit Hole: Compression Tuning Basics
Geometry
Bike marketing pushes really hard on reach, bottom bracket and headtube angle. The long and short: bike geometry matters A LOT. Category leaders have it nailed while the “almost” brands don’t.
But copying an established geometry isn’t a recipe for success. How geometry pairs with suspension goes a long way to generating a bike’s personality.
Class leading suspensions have geometry variations. But these can be accommodated with cockpit fit, etc to produce a balanced riding bike.
Rabbit Hole: Comparing Enduro 29 Geometry
Materials
Typically carbon or aluminum are used for MTB frames.
Carbon has some performance advantages. It will help dampen trail feedback, is light, strong and resilient. Carbon also allows designers more freedom with pivot placement, etc as more complex shapes can be produced.
Aluminum frames are less expensive to manufacture. If you’re on a super tight budget the right aluminum frame can be a great option to review.
Some manufacturers use a carbon front triangle with an aluminum rear triangle. The issue is these manufacturers often list these frames as “carbon” rather than, say, half carbon… If it’s got welds it’s not carbon. The half and half frames are typically used to achieve a price point for marketing or accounting. I personally would ride either aluminum or carbon. Whether it’s simply the marketing of a “carbon” frame being in part aluminum or not I don’t know – but it bothers me. The couple hundred dollars to make a quality carbon rear triangle is worth it…
Carbon vs. Aluminum
Let’s put cost aside for a minute and look simply at performance.
Carbon is a weave material which helps dampen trail feedback. Think of it as rounding out the very end of a sharp input. Carbon is actually stiffer than aluminum, but because it’s able to transfer energy in and out of a weave it has less “spike” through it.
Aluminum will eventually work harden during use. Oversimplified work hardening is when the material begins to flex more. The larger and more aggressive the rider the quicker this will occur.
Putting cost back into the equation – I would ride a quality aluminum bike, one with proper suspension design etc, over a cheesy carbon offering if my budget was squeezed.
Thanks for the read! If you have questions about getting into MTB reach out to our expert team. Everyone at BikeCo rides and we are serious about dialing in each of our clients. Keep an eye out for the next post to this New to MTB Buyer’s Guide series!