Your motorcycle suspension questions answered by Öhlins

The most famous name in the motorcycle suspension world, and an OE supplier to many, if not all, of the leading manufacturers is the Swedish firm, Öhlins, recognised for its gold forks. We spent a little time at the firm’s HQ in Stockholm recently to explore their incredible facility but also to address some of the top questions from our BikeSocial members, Facebook Group members and BikeClub members. Magnus Wallén, M.Sc., Öhlins Chief Engineer spoke to our regular contributor, Adam ‘Chad’ Child.

If the rear of my bike has lots of suspension travel what are the advantages over not much travel?

By having a lot of available travel you have the possibility to handle the energy that the suspension will see when hitting big bumps and obstacles, but still use quite a soft spring to have a smooth ride and good grip riding on smaller ripples, etc.

Longer travel can cope with big obstacles and bumps, think Enduro or Motocross, but race bikes have shorter travel, and harder springs as they don’t have to cope with large obstacles.

What does unsprung weight mean?

Unsprung weight includes the parts of the chassis that is on the ‘road side’ of the suspension. In the front, this includes the weight of the wheel, brake caliper, and moving parts of the fork (lower lubes and part of the spring). In the rear, you include the weight of the wheel and 2/3 of the swing arm. Some manufacturers include 50% of the swing arm and linkage.

How long does a shock absorber last and what makes them wear out?

Firstly, oil. This you change during a regular service. Secondly, piston band and piston rod seal. This is due to wear from the movement. To ‘wear out’ you need to start wear on the inside of the cylinder tube, scratch the piston rod, etc. Still, on an Öhlins shock, most parts are replaceable, and we have shocks from the early 80’s that are still running. Our OE-shocks are designed to last 30,000 km (18,600 miles) in between services, but of course it is better to service more often.

Some Öhlins customers are still using old shocks and forks from the 90’s as long as they are serviced and maintained. Fork oil is like engine oil, therefore if the bike is stored and not moving for 3-5 years, Öhlins would suggest changing the oil.

When I hear people talking about a ‘click’, like add 3 clicks to the rear, what are they talking about?

To adjust the suspension you usually turn an adjuster screw. To keep the adjuster in position during use they are usually ‘locked’ by a design to prevent it from turning, still making it possible to turn the adjuster when needed. This locking function is usually felt like a ‘click’ when turning the adjuster. Between 4-8 clicks per turn is normal. To keep track of the adjuster position you count the clicks from fully closed position.

If you want to adjust or play with your suspension by changing the clicks, make a note of how many clicks, then it’s easy to revert to standard. If you’re unsure contact your local dealer or handbook and they should be able to provide the standard ‘base’ settings. When adjusting you can feel the clicks, rather than hear the clicks.

How does electronic suspension calculate bumps so fast that by the time the front wheel has hit an imperfection, the IMU has assessed the info and made adjustments to the rear shock? And what exactly does it do?

It is pretty much a question about foreseeing what is happening next. For example – on a race track, after hard braking you start to introduce some lean angle, then you know cornering followed by acceleration is ahead. You then have some time to make the adjustment. The algorithms have to be predictive, not reactive.

The algorithms, the calculations on what is happening is predicting, rather than just reacting – that is the clever part. And the more sophisticated the suspension, the more calculations it can perform and at a higher speed. Years of Öhlins experience allow the team to work on these algorithms. Years of painstaking data gathering means the Öhlins team can work out what the bike is doing and what the requirements of the suspension are, but each bike is very different, and off-road bikes are very different. 

What are the components of a set of forks – is there an actual spring?

Outer tube, inner tube, top cap, fork bottoms, seals, bushings, springs, and damping system (cartridge).

NB: some forks have air springs no coil springs for example WP AER48 on the KTM Enduro bikes.

How do I know if or when my front suspension needs oil?

If you have a visual leak – you need to service/repair the fork and exchange the oil. If you are looking for more support at the end of the stroke (bottom out resistance) you can add oil to make the air spring more progressive. The recommended (and allowed) amount of oil is described in the user’s manual.

Forks can be serviced by a local dealer, adding more oil gives more support at the end of the stroke – think very hard braking on track, but not overall support.

I’ve heard the expression ‘fork seals have gone’, but what does it mean and how can I check?

The expression is used when you detect an oil leak between the inner and outer tube. Check your fork seal on a regular basis.

Not only will poor fork seals affect the quality and feel of the suspension, but it can also be dangerous as oil can run down the fork on the front disc or tyre.

What’s a spring rate and as a regular road rider on a sports tourer, do I need to worry?

The spring rate describes the stiffness of the fork or shock spring. Unit is [N/mm], describing how many newtons it takes to compress the spring 1 mm. You can change the spring rate to adapt to rider and bike weight.

For example, a 150N/mm spring means you need 150newton or 15kg to move the spring 1mm. 100N/mm spring means you need 100 newton or 10kg to move the spring 1mm. If a hotel bed was made of 200N/mm springs it would be a hard bed for a light person, but softer for a heavier person. If it was 100N/mm it would be softer, but probably too soft for the heavier person.

You can change the spring rate if you are a heavier rider, but remember on a big bike, the bike is 220-240kg and you are less than half of the weight of the overall bike, therefore you have less effect on the bike. But on a small light bike, MX or small race bike, the rider is more than half the weight of the bike for example 65kg rider and 95kg MX bike, then changing the spring rate will have more of an effect.

I get confused with rebound, preload, compression and damping but don’t they all mean the same thing?

Compression damping: the energy absorbed by the shock or fork when moving inwards. Rebound damping: the energy absorbed by the shock or fork when moving outwards. Preload: sets the height of the vehicle. Added preload makes the bike higher. Preload used to adjust the geometry of the chassis. 

Öhlins underlines changing pre-load changes ride height, and not the stiffness, which is changed by changing the spring (see above). Preload compresses the spring but does not add extra weight.

I ride a tourer sometimes on my own, sometimes with my wife and panniers which I guess adds another 70-80kg to the bike and I assume the rear suspension takes the brunt – but do I need to make adjustments to the front as well?

Usually the main part of the passenger and pannier load is concentrated on the rear. By adjusting preload on the shock you can compensate the chassis geometry to a certain extent. If changing the spring rate in the rear you might need to make changes also to the front to compensate.

I use my road bike on track sometimes, but it feels like a pogo stick in the faster corners – do I need to change some suspension settings or tyre pressures?

Always make sure you ride the correct tyre pressure according to tyre manufacturer recommendations. If feeling like a Pogo stick you are too soft in rebound damping. Make sure the shock is functional, then adjust the rebound clicks to standard position according to the owner’s manual. From there, try to close the clicks in steps of 2 clicks.

Trying to get a road or race bike to handle on track can be easy, but you need to start at the recommended base settings and make sure everything is correct, and working, the correct tyre pressures, and fully serviced suspension. I often chat to track day riders complaining about the handling of their bike on a track day, but this is usually because the tyres are worn, the suspension hasn’t been serviced, etc. Also, if the bike is new to you, go back to base settings - start from base and move forward making small adjustments – remember to make notes.

Should I maintain my suspension forks and shock absorber?

In the same way you change oil in the engine you should change oil and service the suspension. Check the owner’s manual of the suspension or vehicle to get information about service intervals.

Does changing the rake and/or trail affect the suspension?

Trail and rake will change the chassis geometry. These changes, especially if big, could call for an adaption of the suspension.

Changing the rake and trail will not change the suspension, compression, rebound or preload – but it will change how the suspension feels, depending on how extreme the changes to chassis geometry are.

How does the significant increase in power and torque over the last 20 years affect suspension performance? At what point does an OE suspension manufacturer talk to the bike manufacturer to make sure everything will work together?

The OE suspension is set up and tested in the close relationship between the suspension and bike manufacturer. This cooperation often starts already when the bike project starts. The increased power has affected the bike chassis geometry, stiffness, tyres, wheels and also the suspension. This goes hand in hand. The most important about higher power is the engine management system to make the bike rideable, usually full power is only available in the higher gears.

We’ve seen plenty of sportsbikes being fitted with aerodynamic wings recently, do the standard manufacturer suspension settings have to be adjusted to compensate?

The wings are used to maintain downforce during high speed. Usually, you compensate by spring rate if needed. Chad – modern wings work at very high speeds and don’t so much push the bike down, but stop if lifting – therefore it maintains the same position at 180mph for example. They also add to stability and corner entry, but again you need high speeds to move air over the wings.

What is the average rider weight, and what are standard bikes set to?

Each manufacturer is different, and it does depend on the bike, but usually around 75kg for a Japanese manufacturer.

Is it harder to produce OE suspension for a road bike, race bike, or adventure bike?

Adventure bike by far. Street bikes have changing parameters, but not huge. Race bikes have just one job, and you have a lot of time to make the suspension work for one task. On an off-road bike or adventure bike you never know what is coming up, so many parameters. If you think what a big adventure bike must do it’s incredible Ölins can make it work. It must be stable at 150mph fully loaded with luggage and a pillion but also be able to take on jumps off-road! 

If you’d like to chat about this article or anything else biking related, join us and thousands of other riders at the Bennetts BikeSocial Facebook page.

 Have you adjusted your suspension? Have you replaced it? Tell us about it, or ask us questions about them at bikeclub.bennetts.co.uk.