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Alignment on hand-built/classic/non-mass-production cars

Motorsport Wheel Alignment Fundamentals

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Hi all,

I have a TVR (British hand-built sportscar) and am in the process of putting it back together after refurbishing the suspension. I've been trying to set the geometry and noticed I have to dial in a different amount of pre-load in order to achieve the same ride height on both sides. Also, when the car is on axle stands there's a different amount of droop from one side to the other by 10mm or so (measured the distance of the lower control arm to the ground). I've checked the dampers and they have the same maximum travel and seem to be functioning correctly.

When I was re-attaching the wishbones and hubs I noticed that there were inconsistencies in the suspension mounts requiring a different number of shims/washers/spacers in certain places from one side to the other. Never more than a mm or two difference though.

So my question is: How does it affect the way you approach alignment when working on a hand-built car or classic with less precise manufacturing tolerances than modern mass-produced stuff? Are the inconsistencies I see expected? Will the discrepancies be ironed-out once I set the ride height, camber, castor and toe?

Thanks in advance,

Jon

It's a little unclear if the actual chassis mounting points are out of true, side to side - if so, as TVRs were made over several decades, I expect the quality of jigs/fixtures varied over that time, so it's possible it was built that way. However, I would think it more likely that at some point it has had a mishap and hasn't been rebuilt correctly witht he spacer/shim issue supporting that - before going any further you should try and get the chassis as square as possible and this may require some surgery.

That said, if there is a difference, it will have some affect, what and how much will depend on what the geometry difference is. All you can do is get it as close to an acceptable compromise as you can, but if you're using period - higher profile and less 'grippy' tyres - it may not be as much of a problem as with some more modern wheel/tyre setups.

Thanks, it's a 2003 car so in theory should be quite straight. No evidence of any mishaps that would affect the front end geo.

I think I'll spend some time working out where the inconsistency comes from and see what's different side to side. Not sure the best way to do that, maybe make up some sort of jig in aluminium profile.

Hi Jon,

When working with a car like this it's a good idea to get a baseline to understand where the discrepancies are coming from. It's hard for me to comment too specifically without me being there and seeing everything you're talking about in detail but it does sound like you may have some poorly jigged pick up points there.

First thing is to decide on your references. What is the bottom of the car/where you are measuring ride height from for example. What defines the centerline of the car etc etc

From there you can use a combination of plum bobs, a laser level, rulers and some patience. I think it is a topic we'll include in a future course, but essentially you need to setup the car on jack stands, use a plumb bob and fixtures to mark out the position of each essential pickup point by putting tape on the ground and marking the plumb bob intersection. You can use a laser level to project along the centerline of the car and also to measure the vertical distances relative to your reference and coordinate system.

Does that make sense? It seems quite reasonable to me to expect to have to check/measure and shim to get the pickup points where they need to me with a car of this nature.

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