Mountain Bike Forks & MTB Suspension Guide

Advice Buying Front & Rear Suspension for Mountain Bikes

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Most mountain bikes and some hybrid bikes now come with suspension of one form or another. As with most things to do with bikes there is a whole jargon specific to suspension. Things are further complicated in this field by manufacturers attempting to copyright many of the terms involved, and to blind us with science about why their design is better than everyone else's. Here are some of the key terms

1) Travel - this is the amount of movement in a fork or rear shock. Basically how far it can be depressed when pressure is put onto it. On more expensive forks and shocks travel can be externally adjusted. On forks this is normally done by turning a knob on top of one of the legs. More travel being better for downhill, less for climbs.

2) Rebound - this is the rate at which the fork or shock bounces back after it has been depressed. This can be adjusted on most forks and rear shocks so as to alter the feel of the bike.

3) Lockout - this also has various brand specific names such as ETA. Basically the lockout allows you to turn your fork or shock off for road use. Whether this is a good thing or not is negotiable though. You normally have to pay more for lockout when the truth is that if you mainly ride off road and you have bought a decent shock or suspension design you should never need it. Indeed some critics see lockout as a way for lazy designers to bodge bad suspension designs.

4) Pro Pedal, Stable Platform Valve (SPV) etc - these are brand specific terms for manufacturers attempts to reduce BOB.

5) BOB - this is movement in the fork or rear shock induced by pedalling. Reducing and eliminating unwanted bob is the holy grail of suspension design.

6) Sag - this is the amount that a fork or shock depresses when you sit normally on the bike. This is especially important with air shocks and is integral to properly setting up rear air shocks. This is normally done by measuring the sag on your bike, consulting the manufacturer's recommendations and then putting more air into the shock or releasing air.

7) Elastometer - basically a big lump of rubber which is used to provide the suspension on cheaper forks.

8) Damping - this is a way of controlling the movement of shocks (especially coil ones). It is normally done with oil or air.

9) Crown - normally double or triple. This is the piece of metal which links the two legs of your forks together at the top. On most forks it will be single crown. Some downhill and freeride forks are triple or double crown. These are the ones where fork legs come right up to the handlebars.

10) Chain growth/stretch/tension - this can happen on some full suspension bikes. Basically as the rear wheel moves in relation to the frame so the back of the chain moves in relation to the front - while you are pedalling. This can cause the chain to jump and skip or jam. Most manufacturers claim that their suspension system prevents or reduces this problem. A genuine explanation of this from one of the worlds biggest manufactures of suspension bikes reads as follows: “Through the trapezoid rear triangle system, the distance for the chain, the chainlength will always kept the same. This provides optimum riding effeciency, because in that way, pedal-bob is avoided.” Much clearer now isn't it?

11) Single Pivot/Contact system/four bar/VPP/quad link/Maestro - are a collection of generic and brand specific suspension designs. Basically it's all about how you join the rear shock, frame and rear wheel together. The various systems claim smoother travel, less bob and less chain stretch.

This is just a quick guide to some of the main jargon. The newest topics for design refinment appear to be the arcs and curves of the rear shock movement and the effect of braking on rear suspension designs.

As always every manufacturer claims their system is the best. The truth is that if you spend £1000 plus on a bike that is more or less designed for the type of riding you want to do it will probably do that job very well. And as a wise man once said: “Let's be straight here - there's no such thing as a "no compromise" suspension design.

Everything's so inter-related and there are so many variables that it's essentially impossible. But what you can do is find a really good compromise.” As always the best thing to do is ride as many bikes as you can until you find one that you like.

Bikes Suspension - General As we said above probably the most important thing about buying a suspension bike is choosing one designed for the type of riding that you do.

On Hybrid and city bikes this tends to be in the form of suspension seat posts and short travel suspension forks. These are designed to take some of the lumps and bumps out of a ride and add extra comfort.

On Mountain Bikes suspension is designed not only to take some of the bumps out of the ride but to make the ride possible in the first place. As with most things in mountain biking there are numerous different types of suspension depending on the type of riding you are doing.

XC Suspension Bikes - One of the disadvantages of full suspension bikes is that you can loose a little bit of power on each pedal stroke with the power being absorbed into the rear shock (this is commonly known as bob). This is becoming less and less of a problem as suspension designs advance but can still be a factor for some riders. Similarly, although full suspension bikes are getting lighter and lighter a good quality hard tail will generally weigh less than a similar quality full suspension bike. Therefore if your interest is speed and lightness a hardtail bike with a short travel front fork is often the best option. If however your riding takes you off the racetrack and into the wilderness or onto the built trails of Wales and Scotland you may want to try out a full suspension bike.

Full sus Suspension Bikes Cross country bikes generally have between 3 and 4.5 inches of travel. Although a full suspension bike will allow you to go faster downhill than a hardtail their main advantage can often be on climbs and flat sections. Although many people think of suspension as a way of soaking up bumps it also has another advantage. Because the bike can ride over bumps more easily your wheels can stay in contact with the ground more easily. Not only this but many suspension bikes are now designed to push the back wheel into the ground as you pedal. The combined effect of this is that a full suspension bike can often give a rider much greater traction, power and speed than a rider on a hardtail bike even when going uphill. Combine this with the more forgiving ride and greater downhill speed and for all but the quickest XC whippet a full susser is the way forward.

All Mountain/Freeride lite Suspension Bikes - All mountain and free ride bikes tend to have more travel than XC bikes, generally somewhere around 5-6 inches. As well as being stronger and heavier than XC bikes they also tend to have slacker angles. This more laid back riding position combined with the longer travel is deigned to make these bikes handle better on the downhills and on technical terrain. The over engineering which results in the greater strength but heavier weight of all mountain and freeride bikes is designed to handle the bigger hits and greater speed the extra suspension encourages. On the downside the heavier weight and slacker geometry of all mountain and freeride bikes can detract from their climbing ability. Although these bikes will still go uphill they will not do so anywhere near as quickly as an XC bike. Having said this if you want steady uphilling and fast, fun, downhilling an all mountain/freeride bike may be the way forward for you.

Freeride/DH Bike Suspension Bikes - Put simply many downhill and freeride courses cannot be ridden on a non specific bike by anything other than the most talented and brave riders around. Here we are talking 8 foot drops, doubles and 20 foot gap jumps within one 3 minute run. These bikes will not go uphill but they will handle anything you can through at them with gravity's assistance. Be on the lookout for anything from 6-10 inch travel front and rear with monster tyres and massive brakes. These bikes are not for the faint hearted.

4X & Jump Bikes Suspension - Although 4 cross and jump riders fly through the air at massive heights and great speed they tend to opt for shorter travel bikes than many of their freeride and DH counterparts. In fact most jump riders use hardtails with the short travel fork. Similar bikes are used by most 4X riders although many of them are also now using 3-4inch full suspension bikes. Although the kind of travel these riders are using is like that of an XC bike their bikes are not. Like DH and freeride bikes these machines are massively over engineered to handle big jumps and hits.

Forks One of the most popular ways for people to upgrade their bikes is with a new suspension fork. As with suspension bikes forks can be divided into XC, freeride, DH and so on.

XC Suspension Forks - Cross Country forks tend to be light weight and short travel. They are nearly always single crown and typically have between 80 and 100mm of travel. Increasingly cross country forks are air sprung. That means that instead of relying on springs or elastometers as older forks have they rely solely on air pressure. This helps to keep the weight of the fork down and also makes them very easily adjustable. Having said this some manufactures still prefer coil and elastometer sprung forks as they are much simpler to maintain and can take a bit more abuse.

All Mountain/ Freeride Lite Suspension Forks - These forks have a bit more travel than cross country forks, often tipping toward then 5-6 inch mark. As you would expect this makes them a bit heavier as well and makes the lockout all the more important. In this category people start to opt for coil rather than air sprung forks. This does make them heavier but it also makes them more reliable and capable of taking bigger hits.

Freeride/DH Suspension Forks - Here we enter into double crown forks with anything up to 10 inches of travel. Most forks in this category will be coil sprung so that they can take bigger hits. This also has the advantage of enabling you to swap out springs to get the kind of travel you want. A note of warning however. Do not put one of these forks on your cross country bike. It is not designed to take the pressure these forks will exert and your frame will snap!

4X & Jump Suspension Forks - These are generally short travel (80-100mm) forks and are often coil sprung. They are designed to take the sting out of a big landing without the front end compressing too much and thereby providing a stable platform to line up the next move. These forks are heavy but indestructible.

Headshocks & Cannondale Lefty's - Suspension designs used exclusively by Cannondale (although other manufactures are now also playing with the lefty idea). The headshock provides a highly reliable fork with all the internals tucked up inside the frame. The better versions also have a lockout at the base of the stem which makes them very easily adjustable. The lefty's come in a number of different versions. Some are oil sprung and some oil but their distinctive design (where you have one fork leg only) applies across the board. The idea behind the design is a simple one. With a 2 leg fork the bottom of both legs should be level when on flat ground. If you go over bump on flat ground both legs should compress by the same amount. Now the problem with this is that on a mountain bike you are rarely on flat ground. Now imagine going around a corner or riding along a steep hillside. There is going to be more force on the inside leg and it is going to compress. Now go over a bump while on that corner. All the force will be in one leg but crucially both legs have to move together! Think about the forces involved in that. It's a mess. The lefty idea is simple. Only have one fork leg. All the forces are in the same place. This makes the fork more responsive, more active and makes it track better. It's a classic Cannondale idea. It looks strange but it is clever.

Rear Suspension Shocks Thankfully rear shocks are fairly simple. These days they come in 2 varieties, coil and air. Coil for big hits. Air for XC and shorter travel bikes. Many rear shocks come with rebound control and lockout. Most will also come with the manufacturers patented and copy written anti-bob system. If you are considering changing your rear shock you should try and go for something as close in travel to your old shock as possible. Most full suspension bikes are now designed around the rear shock so swapping out the one the highly qualified designer put in for one you read a good review of the other day is not always a good idea. Changing the shock can completely change the ride and feel of your bike in both good and bad ways. So it's a decision to be taken carefully.

Bicycle Suspension Manufacturers The four major fork manufacturers are Marzocchi, Manitou, Fox and RockShox with smaller brands such as Pace bringing up the rear on high end bikes while Suntour and RST provide good budget options. Manitou, Fox and Rockshox also provide a lot of the better rear shocks now on the market.
Have Fun - all at Bonthrone Bike Shops Online UK.

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