This is a help note on getting a trike conversion axle aligned and straight when you’re building you trike and “Trike Wobble”

You would think it would be fairly obvious and it is, but just to state the obvious sometimes helps.

When building the trike you have to think of the height and the mountings (see a previous post about this) but also you must make sure it square to the front and centred. You have 2 wheels at the back which are pushing one at the front which is on a pivot. So essentially you are pushing and riding a triangle. As the front wheel is really the top of the triangle then it stands to reason that unless you are pushing it straight, and it is on as really easy to swing pivot, with an equal amount of force either side of it then it is going to argue with you when you are trying to steer in a straight line i.e. it is going to wobble.

Trike wobble has been pain in the arse to trike riders since the beginning. There are quite a few ways that you can deal with it by tweaking but if you haven’t built the trike square and straight in the first place then you are going to struggle. The most important thing is managing the problem and to do that you have to identify where the problem is coming from so before I go further I’ll just cover a few areas you need to look at if you’re experiencing wobble on your trike. The first one is:

1. You are over reacting to the feedback from the front.

This is often because the rider is new to riding a trike and they don’t know what to expect in real world trike riding. Remember we are taking about a bike that has been triked, not a trike built with a dirty great V8 Jag engine and a 36 foot tiller to steer a front tyre that came off a Volvo dump truck. Nope, The front end of your trike was designed as a bike and as such it feeds quite a lot of info back from the tyre through the handlebars. It’s quite sensitive to road surface conditions, cambers, manhole covers, potholes and cats eyes. You are no longer leaning the bike into corners with one wheel following the other you are steering with a wheel either side behind you. The contact patch of the front tyre is small compared to the wheels at the back and, if you have the bikes original tyre it is likely to have a fairly rounded profile. This means you have not got a huge amount of rubber in contact with the road. So it is sensitive too. Bearing all this in mind you sometimes just have to get on with it and gain experience of what this all “feels” like on the grips. When you first start to ride trike there’s a lot to take in and if it was your bike before, it is quite normal for you to put your feet down when you stop and lean to go round corners. The first one will probably lead to you running over your own toes and the second one will have no effect as you hurtle a 5mph (it feels like 50) in straight line from the safety of your driveway towards the opposite side of the road where your neighbour’s nice new Kia car is parked. Your eyes will go wide and and you will pull the brake on and the clutch (maybe) stopping 2” form the driver’s door (hopefully) with a cold sweat breaking out across your forehead swearing and looking at the trike as if it is its fault. It’s not. Then you will need to peel your hands from the grips which you have held so tight there is in an imprint of your palm in them and hit the kill switch and breathe.

Forgetting the other stuff, it is the grip you need to think about. Most new riders grip too tightly and have stiff arms because it is all new. Try to grip like you did when it was a bike and let your arms act as dampers which keep the trike heading where you want it to go but allow for the feedback you are getting from the front. You will realise that what you thought was a tank slapper was just the front tyre responding to manhole cover or camber in the road and actually didn’t move much at all. Don’t overreact – manage the problem. As time goes on and you build experience it will be your natural state.

2. Tyre pressures can make a big difference.

What are they front and back. Playing about with tyre pressures changes how the trike sits and how much contact you have with the road. There are lots of opinions on this and to be fair it varies from trike to trike. You may have people quoting rears at 10 PSI and a front at 20 and others with 35 in the back and 30 in the front. We normally inflate to 22psi in the rear and see what is occurring with the front tyre although seldom is it less than 26. There is no set formula when it comes to pressures.

3. The frame is not stiff enough.

“Old School” cradles where the engine is slung into the frame can flex when they are converted. Loads of bikes these days have the engine as a “Stressed Member” which actually provides rigidity to the overall build of the bike but some are “Old School” cradle frames e.g. the Triumph Bonneville and the Honda Shadow 750. These have 2 spars that run down from near the headstock and under the engine to form a cradle. These tubes usually narrower then the main frame can flex when the trike is underway. This can introduce and bit of a wobble usually when you are underway and usually around the 20 to 30 mph mark around town. It’s not dangerous and they won’t break but it can be a bit off putting. You can clamp some bracing across them to stiffen them up a bit (remember clamping as there can be no welding to the bike frame for bolt-on conversions)

But the most common way folks deal with this by fitting a steering damper. There are steering damper kits for the Bonneville which you can fit on 10 minutes from suppliers like Norman Hyde.

4. You’ve lost your bearings.

The front end needs looking at and maybe refreshing. If the head bearings are not properly greased or are loose or worn this can cause the problem. Check for play and that they are greased. What about the fork springs? Are they weak or maybe the oil is past its best. Changing the fork oil for a thicker grade say 15 weight may help (it will also help against diving under front braking)

5. The Fork Angle is not ideal.

We all know that bikes come in different flavours in terms of riding style. Some are pin sharp turners like the hyper sports bikes designed to turn quickly with clip on handlebars and where your bum is nearly over your head height. Others like the Pan European are “Tourers” with luggage and a more upright posture for the rider, Naked bikes tend to have a “Sit-up-and-beg” position and other that are Cruisers where feet are forward, seats are low and handlebars wide. Each has their own steering characteristics sharp, neutral, lazy and so you when building your trike you should consider that.

Needless to say the fork angle can create a tendency to wobble.

There’s more to this than I will cover here but generally speaking changing the angle of the forks can dial out the wobble and make the trike much lighter to steer at the same time. But that’s the subject of a whole other article I’d say. If you have any questions about this have a chat with someone who knows about these things there are many out there in Facebook-and trike groups who will have experience may be even for the bike you are looking to trike

6. The front tyre, wheel or brake disks are crap.

Bulges, tyre wall strength, worn tread pattern, over and under inflation, section profile, unbalanced wheels, buckled wheels, loose spokes or wheels that are just not strong enough, can all be an issue. The wheel turns and if it is not true and strong enough or is buckled or warped it will cause a wobble. Check it out, have it balanced. Old or weak tyres will never be right and no amount of tweaking elsewhere will sort it. So as a matter of course do not assume the front tyre is OK because you never had a problem on the bike. There are trike tyres out there and again there’s load of experience in the triking community just ask.

Brake disks can be warped although you may have noticed this already as if you have pulsing feedback when you pull on the front brake lever it’s a good indicator that a disk is warped. A disk doesn’t need to have done thousands of miles to warp, If the bike has been standing along time on a side stand it can do it.

7. OK here we are the biggie – The axle was not mounted straight when it was built.

During the trike building process probably the most time consuming and important part of setting up is getting the rear axle straight and in line with the centre of the bike frame. At Casarva it is something that can take a long time and we have been at it for over 20 years. Not only does it need to be centred and square, it needs to stay that way whilst you are working on the mountings.

How?

We build IRS trikes with a cradle that carries the differential and wishbones that pivot off it. So for us the main thing is that cradle being straight and at the right height (I covered setting the height in a previous article)

Because it is so important we make a centre line on all the kits we supply to DIY trike builders. When we are lining it up we have a laser line on a tripod. They are only a few quid and are worth the money. We also: having taken the seat, cowl and the tank off the bike, mark the centre of the frame on the bike with a visible light coloured marker and on the headstock nut. Then with the laser line lined up from the rear of the bike and shining down those marks, we offer up the cradle making sure the laser line passes through the scribed marks on it both front and back. Because there is a gap between the front and back of the trike frame this also ensures that the cradle is square.

That is all well and good but a solid axle doesn’t have that frame does it? No. You are going to need to find the centre of the axle and mark it on it. You need to accurately measure the width of the axle and find the centre. Set it up so that you have the height right and once it is centred you are going measure from exactly the same point on either side to a symmetrical point on the bike, that is to say, one that is in the same position on both sides of the bike. Don’t assume that foot pegs are exactly in line with each other on either side of the bike, in fact don’t assume anything. Make sure whatever place you choose is the same. I would say so long as the front wheel is absolutely central and pointing straight ahead then you could measure to the front wheel spindle or if it’s more convenient the same point either side on the bottom of the headstock.

Take your time.

I can’t guarantee that any of this will solve your wobble problem. If the trike has been built already and it’s not straight then that is a big problem. Other causes not so much.

I don’t claim to have the answers to every problem and there will be folks who read this saying that I’ve missed something and I probably have.

Seek out as much experienced advice as you can and if you go through the points above then hopefully you will have solved the problem.

Anything that is violent, going to spit you off, get into a tank slapper or be dangerous to you or other road users’ needs sorting and not whilst riding it on the road. There are lots of experienced and good trike builders out there with years of experience but if someone who tells you that “That is just the way it is” or you say it yourself ask “Why?”

Disclaimer: This article is not a workshop manual. It is just some advice based on experience. Of you are not confident in making any changes or adjustments yourself then do not do it. Get someone who knows what they are doing and most of all stay safe.