motorcycle suspension

TDR #9 Optimising your Motorcycle Suspension

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What is the first thing you do when you buy a motorcycle? The first thing you spend your money on? A fruity exhaust to make it sound better? Some wavy discs? Some nice machined footpegs and levers? Or, how about a rear shock or cartridge kit for the front forks? It may not look sexy, but sorting out your motorcycle suspension will do more to improve your riding experience than anything else.

I’ve not had a lot of bikes, but I got to know each one extremely well. I gradually and progressively pushed their limits until I found them wanting, and invariably ended up buying the latest rubber, and then found myself in a suspension workshop having forks and shock revalved and resprung.

My first bike, a Suzuki SV650s had little in the way of adjustability, so thicker fork oil was added, and the rear shock was replaced with rejected nearly new OEM items.

My second bike, an ‘02 CBR600F was transformed into the best road bike ever, forks and rear shock were tweaked by Motorcycle Technics in Stowmarket (http://mctsuspension.com/Home.html), Suffolk. Darren also worked on my ‘05 GSX-R 1000 with equally great results. It was plusher and yet more controlled.

Brands Hatch GP

My brand new ‘08 KTM 990 supermoto came with fully adjustable WP suspension which allowed for endless tweaking.

KTM 990SM : Madder than a GSX-R1000?

My most recent bike, a 1998 VFR800 was bought as a stopgap bike to commute to work on after the gixxer was stolen. The £1500 VFR was getting on a bit suspension wise with 42k on the clock, so I rode it for a few thousand before sending the forks off to Maxton Suspension to have them resprung and revalved. Maxton provide suspension to a lot of the road racers at the Isle of Man TT (Connor Cummings, Dan Kneen, Ian Lougher). In place of the OEM Showa rear shock, I procured a rebuildable shock off Ebay; the Nitron Sport  which has a singe adjuster for compression and rebound damping. These two mods transformed the bike. The fork rebuild wasn’t cheap, I think it was around £600-700, which was nearly half the bike’s value.

When I later sold the bike for £1,000 with 74k on the clock, I took off the Nitron shock and Maxton forks and sold them separately on eBay. If you look at it this way, suspension mods aren’t that expensive, especially if you can save some money and service your own bike yourself.

So I heartily recommend getting your suspension sorted for your weight and your riding style. It will make you faster, give you more feedback and will ultimately make you a safer rider.

So if you have recently bought a bike with adjustable motorcycle suspension, where do you start?

The ‘Average’ Rider
You need to realise that bikes are designed for a wide range of bodies (45-135kg) and ability (novice to experienced) so you can’t just expect to leave it on the stock settings and have it work optimally, unless you’re the average person.

Preload
Preload adjustment, (which even basic bikes have) makes sure that the spring is working in its middle two thirds of travel when riding. Adding pre-load to the forks pre-loads the springs which means that it will take more force to get the spring to deflect from its initial position.

If your forks are bottoming out, you need to add preload (put a cable tie on the fork stanchion and check how far it moves). Conversely, if you are struggling to get the forks to deflect, if they are right at the top of their travel, you need to reduce the preload on the forks. If you add all the available preload and your forks still bottom out, you need stiffer springs for your weight and riding style. If you can’t get the forks down in the usable 2/3 range by removing all available preload then the springs are too stiff and you will need to insert a softer spring.

A setup can work well on track, where speeds are greater, braking more powerful and greater cornering forces loads up the suspension more, and not so good on the road where speeds are lower and you may struggle to get the suspension into its working range.

Rebound
The next adjuster you’re likely to encounter is rebound damping. Again, as speeds increase, so does the amount of rebound damping needed. The faster the wheel hits a bump the more energy it needs to absorb. The spring absorbs the energy, but then releases it. The rebound damping allows the release of that energy in a controlled manner. Too little rebound damping and the front end will oscillates, too much and the wheel never returns optimally to the road surface remaining in the air for longer than it should.

You can test the rebound damping with the bike stationary pushing down on the saddle. It’s best to have a friend hold the bars or put the bike in a wheel chock to hold it upright. Both front and rear should compress, raise and then settle.

Compression
Compression damping (if you have it) should also increase as your speed increases. Those bumps are hit at faster speeds meaning the wheel jumps up more quickly, requiring greater compression damping lest the forks bottom out. At some point you will exceed the limits of your fork or shock’s valving and you may require thicker oil or more sophisticated valving in your forks and rear shock to provide the control you need.

As you can see this is not a basic subject, but with a will you can start to tune your bike, and not fear the adjustment available, instead try out new settings and see how they feel to you. You want to be as comfortable as possible in the saddle. Start some research online, see what resources are out there and have the confidence to give it a try.

Changed your tyres to a new brand or type? Then you will need to tune your suspension again. Not changed your fork oil for a while? You will likely need to tweak the damping to get the same response as the viscosity of used fork oil will vary much more than fresh, especially when hot. Best to change your fork oil regularly to keep as many things as consistent as possible.

Don’t be frightened to try things out. Like all things motorcycle, knowledge is Power, and when you understand how the changes you’re making are affecting your bike, and use a test bit of road to try out the different settings, you can make your bike the best it can be while you save up for the next step.

Learn the way of the Zen Rider…….