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bike alignment
luke2152 - 4/10/21 at 10:56 PM

Far from locost related but I'm sure an appropriate audience:

I'm building a Yamaha TRX 850 with a Triumph speed triple rear end on it (and a host of other bits from other bikes). It is a single sided swingarm which if I'm honest serves little practical purpose but I like the engineering behind it.

I've test fitted it and the rear wheel is offset to the right a bit. I've tried to string line it and it seems to be 10mm ish plus or minus a couple of mm but I want to be more precise, ideally within 1mm. Any suggestions as a method? I'll be either getting the wheel skimmed or the swingarm depending on what works best for the chain line.

pewe - 5/10/21 at 10:36 AM

IIRC correctly flourescent light tubes are die straight.
HTH. Cheers, Pewe

coyoteboy - 5/10/21 at 11:43 AM

What's your centre reference feature and how are you sure the front wheel is centred on it?

bi22le - 5/10/21 at 10:59 PM

I have never had to solve this problem so I am literally typing as I think.

When I have three type of datum issues I really to triangles and pythags, coz maths don't lie!

So, measure the distance from your front axle to your rear, that's one side of the triangle.

Jack up the front of your bike and remove the wheel, put a broom stick or something in the forks replacing the front wheel axle. Measure out a distance along that broom sideways from the bike.

You now have 2 sides and a right angle. Calc the hypotenuse and see if it hours the rear axle.

This will help to check if your front wheel is pointing straight and how in line your rear wheel is.

Ink guessing it would anyway. . . .

luke2152 - 6/10/21 at 12:43 PM

quote:
Originally posted by pewe
IIRC correctly flourescent light tubes are die straight.
HTH. Cheers, Pewe


Interesting. I don't think I've got space on the left side of the wheel for a flourescent tube but I'm going to remember that fact for next time it comes in handy!

luke2152 - 6/10/21 at 12:46 PM

quote:
Originally posted by bi22le
I have never had to solve this problem so I am literally typing as I think.

When I have three type of datum issues I really to triangles and pythags, coz maths don't lie!

So, measure the distance from your front axle to your rear, that's one side of the triangle.

Jack up the front of your bike and remove the wheel, put a broom stick or something in the forks replacing the front wheel axle. Measure out a distance along that broom sideways from the bike.

You now have 2 sides and a right angle. Calc the hypotenuse and see if it hours the rear axle.

This will help to check if your front wheel is pointing straight and how in line your rear wheel is.

Ink guessing it would anyway. . . .


I like the idea. I suspect that it would be skewed by the slightest degree of steering input which is kind of the point but hard to protect against.

Fred W B - 7/10/21 at 11:16 AM

To do this, assuming you are referencing to the frame:

Clamp or bolt a suitable length of aluminum angle or channel as a straightedge to the frame at half wheel height using suitable spacers to clear the engine etc.

Check straightedge datum is parallel to the frame.

Measure from straightedge datum to reference points on frame left and right to determine dimension to centerline of frame from straight edge = Dimension A.

Measure from straightedge datum to front and rear of rear wheel rim wheel and align wheel until dimensions from wheel to straight edge are equal front and back = Dimension B.

Add half of rim width at measuring point to dimension B = dimension C.

Difference between dimension A and C is how much you have to move the wheel.

You can also use measurements from the straightedge datum to the front and rear sprockets to align those components.

Cheers

Fred W B