Building a trike – Get the right Attitude  / Stance

Getting the trike to sit right i.e. with the right attitude or stance is important. Unless you are after a particular stance then it is a good idea to go through a few things before you actually start to mount the rear up and sometimes it can get forgotten in the desire to get going on the build. So here are a few points that you may want to think about starting with: The bike height.

Before you take the back end off the bike, take a few moments to take some measurements with bike upright on its two wheels. On flat level ground take a tape measure and measure the distance from the road / floor to at least two points that will still be on the bike once you have removed the back end say to the top fork yoke and the top shock mount (easier if it’s a twin shock bike) or a point on the frame near the seat. This will then tell you how high they should be once you have the trike axle on the back.

The trike axle needs to be fitted so that the measurements you have taken stay about the same when it is on 3 wheels.

Here’s a diagram you can save to your phone / computer / tablet if it helps:

What makes the height of the axle? The radius of the wheel and tyre on a fixed beam axle does that but with Independent Rear Suspension you need to take into account the suspension set up. With our kits there is a mark on the cradle which tells you where the centre line of the wheel and tyre should be. You can work it out by either measuring the wheel and tyre you have or do a few sums.

Here’s an example:

Assuming you are going to run a wheel that has 17” rim and a 225/50 r17 tyre.

One thing with wheels and tyres is they mix millimetres with percentages and then throw in inches just for shits and giggles.

On a 225 / 50 r17 tyre the 225 is in millimetres and is the width of the tyre section (across the tread.

• The 50 is the wall height of the tyre which is in %. So in this case 50% of 225mm is 112.5mm.
• The 17 is the wheel rim diameter in inches. So we need to convert the 17” to millimetres.
• There are 25.4mm in an inch so multiply 17 x 25.4 and you get the diameter of the rim in millimetres which is 431.8mm.

We can do away with the .5 and the .8 and call the dimensions are:

Tyre wall height 112mm
Rim diameter 432mm

As we are going to need the measurement from the centre of the wheel to the outside of the tyre i.e. the radius, we need work out  half the rim diameter and add it to the tyre wall height:

• Radius of the wheel rim: 432 / 2 = 216mm
• Then add the tyre wall height of 112 to 216 and get a wheel and tyre radius of 328mm.
• So the centre of our axle needs to be 328mm in this example.

That’s all find and dandy BUT in the real world it is likely that once you have taken the back end off your bike you have it securely mounted on jacks. And if you have done that it is likely that you have increased the height of it from the road / floor.

So now what?

Well you need to measure the points again on the bike frame to see how much they have changed by jacking it up  and hopefully they have increased by the same amount which might not be the case if you ratchet strapped the front down and compressed the forks (so let it off  a bit). But let’s say they are the same and both have increased by 25mm. This shows that the bike frame is 25mm higher than it was when it was on its 2 wheels.

To compensate for this when you are fitting your axle height you need to add that 25mm to the 328mm you worked out / measured so you know where the centre of your trikes wheel hub needs to be. In this case 328mm + 25mm = 353mm this is the height from the road / floor / ramp or wherever you have the bike frame strapped to, that the hub centres of your trike need to me. In the case of a Casarva kit this is what the height mark of the differential cradle need to be set at when you are sorting out the mounting tubes to bolt to the bike frame.

I know tyres are squishy and the weight of the trike will affect them but if you follow this routine you should end up with a trike when it’s on its wheels which has the same attitude/ stance as it did when it was a bike

I’ve attached a little drawing that hopefully helps you just make a quick note of the measurements of the bike.

The comments made here are only our opinion and others may think differently and that’s OK. We are just trying to help with a bit of info and if you need more just ask.  If we don’t know the answer we’ll say so.

Happy building

Cheers