First off all, the rims of a zx7r are heavy!

Bloody heavy... I bet there are boat anchors who are lighter than these rims.

By now, we all know that it's a good thing to loose some weight on that zx7r, to make it faster.

But there is is difference between unsprung and sprung 

Whuuut?

 

Sprung weight is the mass of those parts supported by the suspension: engine, frame, battery, fairings,...

Unsprung weight is the rest: wheels, tyres, brakes,...

When you put your bike on a weight-reduction plan, it is important that you remember the 6-to-1 rule. It is said that a 1 kilo reduction in unsprung weight is equal to a 6 kilo reduction in sprung weight. Thus, if you’re going to spend money on lightweight hardware, concentrate on unsprung weight!

 

6 to 1? That's huge! Tell me more...

 

For example, the unsprung mass of a wheel offers a trade-off between a wheel's bump-following ability and its vibration isolation. Bumps and surface imperfections in the road cause tire compression, inducing a force on the unsprung mass. The unsprung mass then reacts to this force with movement of its own. The motion amplitude for short bumps is inversely proportional to the weight. A lighter wheel which readily rebounds from road bumps will have more grip and more constant grip when tracking over an imperfect road. For this reason, lighter wheels are sought especially for high-performance applications. However, the lighter wheel will soak up less vibration. The irregularities of the road surface will transfer to the cabin through the suspension and hence ride quality and road noise are worse. For longer bumps that the wheels follow, greater unsprung mass causes more energy to be absorbed by the wheels and makes the ride worse.

 

Changing the unsprung weight has no direct effect on springing (as it's not supported) but reducing it can make a big difference to the ease with which a bike can change direction!

Lighter wheels produce smaller gyroscopic forces.

Lighter tires, tubes, rotors, hubs, spokes, rims and sprockets reduce the gyroscopic effect of the spinning wheels. With less gyro, the bike steers lighter, handles better and accelerates harder. This is something that even the most oblivious test rider can feel.

 

Better handling? Yes please! Were do I begin?

If you are interested in reducing unsprung weight, you should know that some kinds of unsprung weight are worse than others. For example, the further away from the swingarm pivot the weight is located, the faster and farther it moves and the quicker it’s forced to change direction. You need to concentrate on lessening unsprung weight that is at the furthest end of the fulcrum arm. Conversely, the closer the weight is to the swingarm pivot, the less it affects suspension performance.

 

OK, back to those stock rims made out of bricks

Yes, back to business!

There are some options to choose from:

Get those beautifull brandspanking new Dymag wheels.

They will reduce almost 2 kilo in the front and 3 at the rear!

But they will cost you about 3.000€ for a set. I bet you paid your bike less than that.

What are the pre-owned options?

 

Sometimes you can find a set of Marvic magnesium rims.

looks great but be carefull... 

Magnesium wheels are susceptible to corrosion. Magnesium sits at the very top of the galvanic table, just above zinc. When it reacts (corrodes) with another metal it is unfortunately always the donor material!

Corrosion can track and worm-hole through magnesium and can go unnoticed under paint (particularly powder coat). Corrosion around dissimilar metals could in extreme cases cause things like brake discs and sprockets to part company with your wheels under the worst possible circumstances.

So when you find a set of magnesium wheels, it's always a good choice to get them X-rayed in search of cracks.

 

Sounds like a lot of hassle...

 

An easy and cheap mod  however is to get a set of zx6r wheel form the G/J series (98-00 or 00-02).

Front wheel:

Almost a straight swap!

It has the same axle size and rotor offset, so can use your zx7r axle and brakediscs.

unfortunately, the zx6r speedometer get's its info from the front sprocket, the zx7'r from the front wheel...

So you will lose your speedo with the zx6r wheels.

You only need a set of spacers, preferably in aluminium.

The right one is the same size, the left one is a replacement for the speedo pick-up

With the lighter wheel and spacers, you save about 1 kilo in the front!

 

Rear wheel

this is more work...

You can still use your zx7r axle and sprocketholder!

But you need to space out your rear sprocket by 3mm to keep the chain in line.

now for the rearbreak...

zx6r brakedisc: 4 mountingpoints  and 220mm

zx7r brakedisc: 5 mounting points and 230mm

 

 

 

zx7r wheel: 5,3 kg (wheel incl bearings)

zx6r wheel: 4,5 kg (wheel incl bearings)

That's an easy 0,8 kg reduced!

 

44th:

Front

zx7r: 5,0 kg

Dymag: 3,3 kg

back

zx7r:8kilo

Dymag 5,0 kilo

 

sam green

Front

zxr750 4,8

zx6r:4,4

back

zxr750 6,6

zx6r 5,4

marvic penta

front 2,9

back3,77

 

 

 

To make them fit, U will need other spacers.

You can buy them here:

https://www.projection-components.co.uk/zx6r-gj-front-wheel-spacers-for-zx7r-front-end-124-p.asp

zx7r spacers en speedo pick up: 255gr

zx6r alu wheels spacers: 55gr

That's another 200gr reduced

Total: 1 kilo!

 

You also get rid of the speedo cable wich is 200 gr but that is not unsprung weight...

 

You want to reduce more?

Replace the OEM breakdisc with aftermarket ones

OEM disc: 1,8 kilo

...... : ..... kilo

Less weight en more braking power!

 

Bolt these disc on your zx6r wheel with titanium bolts and you save another 80gr

 

Titanium bolts: 70gr (10 pieces)

OEM bolts: 150 gr (10 pieces)

 

Keep in mind that you can save some extra weight with the 4 pot mod

Nissin 4 pot brake caliper: 950gr each

Brake pads:  CL: 219 gr per set

 

 

zx6r spacers in alu: 55gr per set

zx7r spacer en speedo pick up: 255gr

speedo kabel: 201gr

 

 

 

 

 

 

 

zx6r j model, zzr600 (05-08) zx9r (00- 03) have the same front wheel.

98-99 zx9r uses a 20mm axle! stay away from that year

96-03 zx7r uses a 25mm front and rear axle

 

02-03 zx9r uses 320mm rotors like the 96-03 zx7r.

they bolt right on