Archive for the ‘Frame – Wheels’ Category

XS650: SR500 Rear Wheel Bearing Spacer   Leave a comment

I need one. A bearing spacer. Rear wheel. SR500. Drum brake.

Goes inside the hub. Between the bearings.

If anyone has a spare one handy please drop me a line – reply below.

Seems the drum and disc brake versions are different:




Drum Brake (spoke/mag)



Disc Brake    (mag)





drum brake rear wheel bearing spacer (XS650)

drum brake rear wheel bearing spacer (XS650)



This is from an XS650, but you get the idea.

Thanxs …

Rear Wheel Bearing Spacer


mag/spoke: drum  #275-25317-00


mag/spoke: drum #90560-20135










Ring OD:



Posted December 7, 2011 by xscafe in Frame - Wheels, SR500

Tagged with ,

XS650: Fork Rake Adjustor   Leave a comment

From Cheney Engineering:


Fork Head Adjuster - Cheney Eng.

Fork Head Adjuster – Cheney Eng. … rake adjustors…top, bottom or both


These give you the ability to quickly change your rake.

  • Insert one adjustor in the top of your fork head: -can position this for a +0.50 or -0.50 degrees over 30″
  • Add an adjustor in the bottom of your fork head: -gives an adjustment of ~ +1 or -1 degree over the 30″

Each Adjustor comes with Adjusting Offset, Race and Bearing.

You need to supply the diameter, thickness and length of your fork head.

Your stem probably requires machining to fit the bearing. Or buy one of theirs and press it into your bottom yoke.

They also have some nice trick stuff to adjust your offset-

  • Offsets provide the ability to make incremental adjustments to move your forks closer or away from your fork steering stem. Offsetting forks farther from the steering stem transfers more of the engine weight to the rear wheel…provides better hook-up. By modifying your offsets, you can improve your rear wheel hook-up. The trick is getting the right amount of offset for each style of track.

…and for dealing with shorter inverted forks.

XS650: Caster/Rake and Trail   1 comment

Motorcycle manouverability and stability is a product of many factors: …eg…

  • Front wheel alignment
  • Wheelbase
  • Weight distribution
  • Centre of gravity
  • Position, type and performance of the suspension
  • Size and performance of tyres
  • Riding position

2 of the most critical are Caster or Rake and Trail.


1.. Caster/Rake




The angle created by the vertical through the front wheel centre and the line through the centre of the steering head tube.


2 .. changing caster rake

changing caster rake


3 .. Trail




Take that vertical line through the centre of the front wheel. And follow the Caster/Rake through to the ground. This distance is the trail – how far the wheel trails the rake geometry.

Large Caster/Rake and Trail give better high speed stability-tracking-longer wheel base and poorer low speed handling. Great for straights.

Small Caster/Rake and Trail has the opposite effect. Reducing wheel base. Allowing you to carve through the corners.

In practcal terms it means you can optimise your riding by understanding where you are going to ride. 2 or 3 triple trees drilled to different Casters/Rakes allow you a certain flexibility.

Understand your frame and steering geometry. Know your suspension dynamics. And how to change them for a desired effect..

However. When we talk wheel base, it makes sense to me that not all wheel base is the same. I see 3 types:

  • before the steering head..trail
  • between the steering head and the centre of gravity..rake and stretch
  • after the centre of gravity..traction..probably be able to divide into pre and post suspension points

Easy variables:

  • Fork Length
  • Fork preload
  • Fork Spring Rate
  • Caster/Rake
  • Swingarm Length
  • Rear Shock Length
  • Rear Shock Preload
  • Rear Sock Angle
  • Rear Shock Length
  • Wheel Size and Weight Distribution
  • Tyre Characteristics

And don’t forget the Fork Brace.

It’s simple physics at low cost. And a lot of feeling.

Large return on investment.


XS650: Frame Dimensions


Early:256, 306
Mid:447, except 78-9 french
Rake 27° 27° 27°
Length: Steeringhead bottom to swing arm pivot 685 688.7 688.7
Swingarm pivot to upper shock mount, rear 302 311.5 300
Height Steeringhead  bottom to Swingarm pivot 434.6 409.5 409.5
Steeringhead top to frame bottom 816 811.1
Swing arm pivot to upper shock mount, rear 311 311.5 291.5
Swingarm length: To centre of adjuster
Rear-shock length: On bench, spring fitted
On bike,at rest:
On bike, with rider:
Sag: rear
Rear shock: Spring rating
Front Forks: Rake
Fork length: At rest
With rider
Sag: front
Wheel and tyre height: Front
Weight: Frame
Bike, dry
Bike, wet
Rider and gear




Somewhere in the back of my mind comes a voice telling me that european models after ’75 had a reduced rake, 26.5°. Trail being reduced from 115mm to 108mm. Is this correct? I don’t know.

What I do know is that frame modifications meant drastic weight gains. Ride improved.

XS650: (Un)Sprung Weight   Leave a comment

Some would say I’m coming unsprung. Some that I’m unhinged. Others don’t even see me. Me? I can get along with myself most of the time. And that’s all that really matters. In my own way I’ve found my balance. The theory of multiple intelligences makes sense to me.

It’s not so clear cut however when it comes to my bike.

My grandfather always quoted the 4 B rule. You don’t lend your Bundle, your Better-half, your Bike, or your Bum. As for my Bundle? What the Better-half doesn’t get the Bike does. And my Bum spends a lot of time on the Bike.

Which brings me closer to my point. Your bike is basically for you. You ride her. You put your trust into the bond you have with her every time you ride. You. Your bike. The road. The conditions.

Really, she is set-up for you.

Parts of the matrix making up your ride experience. Your mass. Your type and style of riding. Determiners of basic geometry:

  • Rake. Neck height. Trail. Wheel-base. Fork length. Centre of gravity…All factors in how she handles.
  • Tyre size. Rear shock angle. Spring rates front and rear. Preload. Compression dampening. Rebound. Oil weight….factors relating to how well she handles surface variations and cornering.

Major considerations are Sprung and Unsprung Weight.

Force the wheels up and down. What moves is Unsprung weight. Your suspension forces this into contact with the road. Reduce this weight and your suspension has less work to do keeping it all in contact with the ground. Releases the suspension for the other part of its’ job. Dealing with the G-forces experienced in cornering, acceleration and deceleration. Giving you , the rider, a softer ride:…

  • Front Wheel:  tyre, tube, valve, rim, spokes, hub, wheel bearings…
  • Brakes: rotors, calipers, caliper mounts, pads, hoses … drum, shoes, linkages…
  • Forks: lower legs, guard, brace, damper rods, fluid, axle, speedo drive…
  • Rear: tyre, tube, valve, rim spokes, hub, sprocket, cush drive, axle, adjusters, rear of chain, rear of swing arm, brakes-disc or drum, drum plate lock, end of chain guard…

Sprung weight moves with the frame. Held by your suspension, isolated by it from the road. Includes: motor, transmission, you-the rider. With gear. Mass. Means energy.

Some are both, one end fixed to the frame, the other tracking the wheels:…

  • fork spring, swing-arm, shock absorber, coil spring, suspension linkages, some rear guards, chain guard, rear chain or drive-shaft,…
  • Weight split isn’t 50/50, division has less to do with center of gravity than centerline from the pivot point…
  • unsprung swing-arm rears are lighter than the sprung front.

All of it you need to push.

Then you have Rotational Weight, which can be either sprung or unsprung.

Why is this important? Well, if you’re my dog, and something moves, you nail it or bite it. Even better, both.

There’s inertia. The resistance of any physical object to a change in its state of motion or rest. Want to move something from rest? Change its’ velocity? Or direction? Stop it? Acceleration and deceleration. Find some energy.

Do this around a pivot. Angular Momentum.

Things that go round are kind of a double whammy. They need to be accelerated forward, and rotated.

Every gram of mass in the tyre or rim has the same effect as two grams in the frame. The tyre’s angular intertia is approximately equal to its linear inertia.


Cruising? Weight is pretty much irrelevant. Air drag followed by frictional forces due to rolling resistance of tyres, bearings, etc.are your primary concerns.

Hardtails…no suspension, zero effect.

  • Rotating mass affects acceleration.
  • Total mass requires work to accelerate, decelerate, change direction or elevation.
  • Extra unsprung mass has a negative effect on a bikes’ ride.

That is why rotating weight is an issue. Rotating weight includes anything that turns: .. wheels, tyres, brakes. Also, engine parts: the flywheel, crank, clutch, cam, transmission, chain, …..

When accelerating you put energy into two things beyond that needed for a constant speed for the given riding conditions…

  • acceleration, F=ma. (linear momentum). Mass of the bike, wheels and rider.Rectilliner acceleration, Increasing kinetic energy
  • rotational acceleration- (angular momentum).extra to the energy required to accelerate in direction of travel.

Though static weight matters, pursuing rotating weight matters more.

Minimum weight is just that. Minimum. Should your bike be lighter, add ballast. Where you want it. Low.

Light has it’s advantages. Rotating weight has more.

There are practical advantages aside from better acceleration and deceleration.

Look at the variables. Type of track. Your style. How much brake you use. How much the course will require. What and where are the G-forces. Reduce rotating mass, you could use smaller brakes. Lightness means the whole range of components get an easier time. Tyres. Shocks. Springs. Brakes. Rider.

Smaller brakes are easier to manage, generate less heat. The weight can go elsewhere.

You could go to the effort of laser cutting new crank discs from modern lightweight materials. Expensive. While you’re at it do it right. 270°. 256 crank discs were commonly drilled and filled with lead, from factory. When these plugs started falling out they stopped. Cranks are finely engineered. Be careful. A well balanced crank is what you really want. Drilling for lightness is a compromise between structural integrity and performance. Crossing the finish line last is better than not at all. Cheaper too.

Running total-loss? Have a range of rotors, drilled, for different weights. Swap them in and out to suit. Could even have several sets of wheels, having different diameters and weight distributions. For that matter, if sharing a bike it could be a good idea to have several sets of forks, and rear shocks, all having different spring ratings, dampening profiles, preloads, actions. Even different length swingarms. If your forks are a little longer, moving them up and down in the triples trees gives easy geometry adjustment. Several sets of triple trees-predrilled for different rakes, trails, wheelbases. Doesn’t take long to swap any of these in and out for individual riders.

Short-tracks are easier. Narrower rev range. Cornering is more predictable. Easier set-up. Larger tracks, are a little different. Corner and straight combinations. Rpm. Velocity, Cornering dynamics. All more complex.

With lighter rotating components, you get up to speed at a faster rate.

Start at the front. Reducing weight with the largest parts first. Drilling shafts is expensive and the gain is very close to the centre of rotation. Little gain for the cost.

Lower friction bearings. Lighter grade oils changed frequently. These may give better results than taking components to their structural limits.

How far do you go? There are breaks. And there are breaks waiting to happen. Always at the wrong moment. Strain, power loss, or vibration. Vibration will literally eat horsepower. Rear wheels never see it.

Power to the wheels is always very important. The more power getting to your tyres, the faster you’ll go. Assuming you and your bike can handle it.

Unsprung vs sprung weight have the same efect on acceleration and top speed.

Lighter wheels, tyres, brakes, rotors have gains due to the lower ammount of power required to rotate them. Lighter springs can be used. Frames are less disturbed by surface irregularities. Gains frequently, improperly attributed to unsprung weight.

Weight removed from unsprung components such as rear wheels may affect traction if the wheel is not under control.

Require precise control of wheel movement? A low percentage-45:55-of unsprung weight is an advantage, giving faster lap times, higher top speeds. Because traction is improved.

Unsprung:sprung ratios affect wheel control. Especially on uneven and road racing surfaces. Of lesser importance for dirt track and little value for drag racing or hardtails.

The rest is up to you. How much are you prepared to spend? Reliability vs performance. Strictly racing? Maybe you sacrifice reliability for performance.

The lightest and fastest bike is only as good as it’s rider’s training and technique.

Together you move this.

You. Your body weight. Your motor. United. With machine.

Bio-mechanic body language.