Suspension: All these changes cost is a little time

Published: 24 June 2002

You don’t have to spend a fortune on bolt-ons to make a real difference to the performance of your bike.

Kawasaki has endowed the 7R with excellent suspension components and getting them set-up correctly will perfect your ride on road and track. The 43mm inverted Kayaba forks and Uni-Trak rear shock are both fully-adjustable – for pre-load, as well as compression and rebound damping.

Sorting them to suit you could help you lap a track more quickly and boost your confidence on the road.

The ZX-7R has such finely-tuned components that a single click of compression or rebound damping can transform the way it handles. One man’s settings won’t suit another.

We used two riders at opposite ends of the weight scale – 10-stone racer James Doherty and 16-stone MCN road-tester Keith Farr. Each set-up was carried out at Bruntingthorpe, Leics. Odds are you’ll weigh somewhere between the pair, so use their settings as a guide.

What you’ll need: A tape measure, a 17mm open-end spanner, a flat-blade screwdriver, a rear shock C-spanner, pliers/cable snips, and two medium-sized cable ties. You’ll also need a clear understanding of the following terms.

Pre-load: Forks and shocks settle into a natural position when a bike is static. When you brake, accelerate, or corner, they slide (travel) on their damper rods or stanchions. This is the suspension working. Setting the pre-load means controlling how much of the suspension’s maximum travel you want to use. There is an optimum and it takes trial and error to find it. The spring has a pre-determined springing rate – how firm it is. Altering the pre-load doesn’t affect this – it merely determines where the suspension begins to work and how it moves.

Rebound damping: Controls the rate at which the suspension returns once compressed. Too much and it returns too slowly. Hit a sequence of bumps like this and your suspension will " pump down " until it remains compressed. This makes the bike highly unstable. Dial in too little and you’ll get " chatter " – where the suspension returns too rapidly to the start of its stroke, upsetting the chassis.

Compression damping: This controls the rate at which the suspension compresses.Too much and the bike " kicks " off bumps. Dial in too little and the bike dives unnecessarily easily.

Standard settings:

Forks: Pre-load: Six-and-a-third rings show.

Rebound damping (top of fork): Seven clicks from fully in.

Compression damping (bottom of fork leg): Five clicks from fully in.

Rear shock: Pre-load: 24mm active thread wound down.

Rebound damping (bottom of shock): Position two.

Compression damping (left front of shock): 14 clicks from fully in.

Step 1: Assess suspension travel:

The more suspension, front and rear, a bike uses without bottoming out, the more efficiently it’s working. We want to set the handling so the forks and shock are doing all the work, instead of the tyres.

To work out how far the suspension is travelling, you will need to fit a cable tie around one fork inner leg and the other around the rear shock’s damper rod, snipping the excess off once they are secure.

Push both cable ties upwards up the fork leg and damper rod. As their travel is used, the ties will be pushed downward. As long as they’re firmly in place, they’ll remain in the positions they’re pushed into, allowing accurate measurement.

It’s pointless working on your compression or rebound damping until the pre-load is set correctly.

Keith: I only needed three laps of Bruntingthorpe to find out that the front was not right for me. The pre-load was only wound in about a quarter of the way, but it was already too firm. You’d need to weigh about 50 stone to ever need to wind the front pre-load adjusters all the way in. The rear was vague but felt in the ball-park. Afterwards our first ride we checked the cable ties and measured 33mm of unused travel at the front, and 8mm at the rear.

That is the distance between the cable tie and the bottom of the suspension’s stroke. Ideally, I’d like 25mm at the front and 5mm at the rear. These are rough but work well with most sportsbikes, as thousands of racers, trackday enthusiasts and suspension experts have discovered from years of trial and error.

James: What a difference six stone makes. I ended up with 47mm of unused travel on the front, even after braking like a demon, and I had 12mm unused travel at the rear. Both ends felt solid to me and needed seriously loosening up.

Step 2: Adjust front and rear pre-load

With both ends too firm, we needed to find the right settings for both riders. It’s pointless experimenting with a bike’s damping until you know the suspension is travelling the right distance. The greatest gains are made from getting the pre-load right. Damping adjustment is fine-tuning.

Keith: The stock six-and-a-third rings-setting makes the front too stiff, so I wound the front pre-load adjuster out until seven-and-a-half rings were showing which, when we measured how far the forks were travelling as a result, translated to 24mm travel unused.

That, as it turns out, is the point at which the ZX-7R’s front end bottom’s out – you can’t use all of the fork inner’s travel, it runs out of movement before that. So, I firmed it back up again until just seven rings were showing at the top of both fork legs. I then had 27mm travel unused – the original 24mm plus another 3mm to provide a cushion against bottoming if I hit any unexpected bumps.

Total front end travel on a superbike, in most racers’ experience, should be around 120mm. We measured it. With 27mm travel unused, we were using exactly 121mm of active travel – the amount of stanchion the forks are actually sliding up and down on. To measure this, lever the bike on to its sidestand and tip backwards, until the front wheel leaves the floor.

Be careful and make sure you get a mate to help. Once the suspension settles, measure the distance between the top of the fork inner and the bottom side of the cable tie. You can’t measure this if the front wheel is flat on the ground. The bike’s own weight uses up a lot of initial travel.

Next, I backed the rear pre-load off until only 22mm active thread – the amount between the top of the shock and the point at which its locking rings sit – was wound down. This reduced unused rear travel to between 5 and 6mm – perfect.

James: I got mine spot on first time, based on Keith’s experience, by backing the front preload off until seven-and-a-half rings of the possible eight-and-a-half rings were showing. My 47mm unused front travel became a much more acceptable 28mm. I backed the rear off to 20mm active thread wound down and got the unused travel down to 6mm.

Step 3: Adjust front compression

We wanted to get the front feeling roughly right before we turned our attention to the rear. If needed, we’d go back and sharpen the front again if it needed further attention after completing work on the rear.

Keith: I took the compression damping from five clicks out to just three. Suddenly, the front felt composed and I became more confident in the front tyre’s abilities. I knew it was right because I suddenly got a much better feel what the tyre was doing. And the bike became more composed.

James: I took the compression damping to four clicks out from hard, of the possible eight. It instantly dialled the front end in. I didn’t need to touch it again and was able to brake harder and later with confidence.

Step 4: Adjust front rebound

Keith: I went from the stock seven clicks from hard to five from maximum and instantly wished I hadn’t. Dialling in more rebound, as I’d just done, slows the rate of return of the forks once they’ve been compressed. Being heavy, I compress them a lot under braking and, because the return was slower, the rate at which weight transferred from the front to the rear was slowed dramatically. Position six wasn’t much better. I put it back to seven.

James: I was able to go to position five from maximum without a problem. As I’m a lot lighter, I don’t have as much impact on weight transference, so the unstable rear Keith experienced was avoided.

Step 5 Adjust rear rebound

With the front behaving itself, we turned our attentions to the rear and decided to set the rebound first as it’s the adjustment that governs rear end wallow – something that many complain about on the ZX-7R.

Keith: I pulled an instant second a lap (of Bruntingthorpe, this is) off my time by clicking the rebound to position three, instead of two. The rate at which the suspension returns to normal after being compressed is slowed and, at my weight, that dramatically cut the wallow I was experiencing exiting corners.

James: I didn’t need to move from position two. I tried three but it slowed the return down too much. Standard is fine for me.

Step 6 Adjust rear compression

Rear compression is the adjustment that governs how quickly the shock travels when it’s being compressed.

Keith: I needed to slow it down, as well as firm it up, so I went from 14 clicks from hard to 12 from hard. Suddenly, the ZX-7R felt like a race bike, albeit a heavy one. It was completely planted, absolutely didn’t need a steering damper and wasn’t phased one bit by overbanding, drains, ruts or bumps. Riding it hard on totally smooth Tarmac was great. In this trim, it’s ideal for trackdays for me.

James: I left the rear compression as it was. We’ve got different riding styles and I’m lighter. But I’d say, if it still doesn’t feel quite perfect to you, look between settings of 15 and 11 from hard. You’ll find the right one there if you weigh anything close to average.

Step 7 Revisit front

Often you’ll need to go back and make final adjustments to the front as a result of changes made to the rear.

But in our cases we were both happy with the settings and just got on with some serious lapping.

From early morning starts of 1 min 24 seconds, we managed to get our times down to 1 min 16 seconds on Bruntingthorpe’s newest, tighter-than-before, variant of its track. That was down to the suspension improvements – we both know the track well and usually hit our best times within minutes of arriving.

Mid-corner speed around the one left hander on the circuit increased from an indicated 108mph to 119mph for Keith and from 109mph to 120mph for James. Keith’s end-of-straight terminal speed, which is dictated by how fast you can exit the chicane and how late you can brake at the end, rose from 140mph to 150mph. James’ went from 140mph to 152mph.

Final Settings:

Keith

Forks: pre-load Seven rings showing

Rebound damping: Seven clicks from hard

Compression damping: Three clicks from hard

Rear shock: pre-load 22mm active thread wound down

Rebound damping: Position three

Compression damping: 12 clicks from hard

James

Forks: pre-load:Seven-and-a-half rings showing

Rebound damping: Five clicks from hard

Compression damping: Four clicks from hard

Rear shock: pre-load 20mm active thread wound down

Rebound damping: Position two

Compression damping: 14 clicks from hard

The ZX-7R has all the attributes needed to handle brilliantly. It doesn’t need better parts, unless you’re a seriously fast rider, you’ve damaged the stock items, or you just want to look flash. If that’s what you’re after, take a look at our Bolt-Ons: Handling section. If you swap a series of lighter parts for stock, don’t forget to go through the suspension set-up sequence from scratch.