Fully Adjustable Rear Suspension

I had a month out from blogging, but that didn’t mean I was idle. Everything I had done on the rear suspension had been removed, re-done, then tweaked, then modified and finally mocked up before I went ahead and fully welded everything.

The first problem I had was I wanted to reduce the amount of anti-squat I had. Previously, I had set everything up for about 95% anti-squat. My theory, at the time, was I had read about several low slung racers that had 100% anti-squat and the Haynes Roadster is a light, low slung kit car with  50/50% weight distribution. The standard Haynes Roadster had 0% anti-squat and my decision was playing on my mind. So, I kept reading, in particular Herb Adam’s ‘Chassis Engineering’, this book basically confirmed my fears. Although many racers have 100% anti-squat, they are driven on perfectly smooth, grippy tarmac and not every car has a double A Arm. According to Herb, the limit for a road car with an IRS is about 25%. Any more and under hard acceleration, the back wheels will hop and try to walk. This action places enormous forces on the Arms and mounts.

Bring out the disc cutter!

Unfortunately it bit into the metal, jumped out of my hands and took a sizable chunk of my hand with it. DOH!

With all the mounts removed I cranked up Kangaloosh and recalculated my mounts. Luckily, the whilst removing the mounts I found I had made the upper arms wrong. Somehow, between looking at the co-ordinates on my laptop screen, writing them down and making the arms, I had managed to loose exactly the width of a tube somewhere.

Anyway, it is all back together and despite being only tack welded, remarkable solid. The whole assemble moves up and down freely and I have several degrees of adjustment in toe and camber.


The uprights’ rear attachment points, join to A Arm that have 2 attachment points. This gives these points great strength in the forward aft direction. However, having these two points alone would not stop the toe in/out angle moving around freely. Therefore, there are 2 additional mounting points. The top A Arms have a turn-buckle links. These links have opposite handed threads at each end, so to adjust the length, you simply loosen the lock nuts, give a few turns and re-tighten the nuts. Due to the Anti-Squat angle of the top arm being different to that of the bottom arm, the caster angle of the rear upright changes as the wheel rises and fall. This mean the front turn-buckle link needs to be able to move up and down very slightly. This is why I have used a rose-joint rear the turn-buckle joins the Arm and not a Clevis joint.

Haynes Roadster Rear Upper A Arm

The lower rear suspension A Arm also need to be pretty strong. The urethane mounts that link to the chassis have Clevis type arrangements that allow adjustment yet can be bolted up solid, to provide a strong, inflexible link. The A Arm also has a Clevis joint. This allows the lower rear mount to be move back and forth.

Fully Adjustable Haynes Roadster Suspension

Fully Adjsustable Haynes Roadster Rear Suspension

Kit Car Adjustable A Arm Suspension

The http://speedwaymotors.com A Arm set-up above, is designed for oval track racers. The ball joint mount (top of picture) can be moved both closer to the front or rear of the car and out-wards or in-wards. One of the ball joint mounts is a threaded stud and the ...

Toe In / Toe Out

The amount of toe is expressed in degrees, as the angle from parallel of the front wheels. Sometimes Toe is expressed as the difference between the track widths of the leading and trailing edges of the front wheels. Toe adjustment can be used to overcome handling difficulties in the car. ...


There are loads of terms that are used to describe suspension and car technology: Ackermann Camber Caster Roll Centre Scrub Scrub Radius Slip Steering Axis Inclination (SAI) / Kingpin Inclination (KPI) Toe in / Toe Out So why are they important ? With donor parts taken from a number of manufacturers, chances are ...

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Haynes Roadster Rear Upright

This isn't the standard Haynes Roadster Rear Upright. I've modified several of the dimensions to get a small degree of anti-squat. Because the chassis is 4 inches wider than stock, some of the other dimensions have changed too. I wanted the A-Arms as long as possible, so the mount holes for ...

Haynes Roadster Rear Suspension

The turnbuckle link is shown for demo purposes only and is not the real item. I've finally started the rear A Arms. I spent hours checking out tons of options but went with my first attempt. I wanted a design where I could loosen a lock nut, twist a turn-buckle ...

Anti Squat Rear Suspension

Making & welding the rear suspension brackets has been slow. What is Anti Squat Rear Suspension all about? When you plant the pedal at the lights or accelerate out of a bend, weight is transferred to the rear of the car. The front wheels lift and loose traction and the ...

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