Formula Student (F SAE) Design – Parts 9 & 10

Here we talk about the assembly and the setup of your car.  Before going there, a word or two about aerodynamics.  That’s my specialist area and by now everyone in Formula Student knows that to win you will need to do some work in this area.  HOWEVER – to score points in the dynamic events you need to be running. That means passing scrutineering and ideally it means having done hundreds of miles of testing.  If you turn up with fancy aero bits on the car but don’t make it into the dynamic events, nobody will need to tell you that your priorities were a bit off.

So for those that haven’t run a car at a formula student event yet, leave the wings off the car until you’ve completed the all dynamic events at least once in a competition.  If your car isn’t finished and testing at least a month before your first event, leave the wings off the car and go testing.  You may well score fewer points in the design event but getting the car through the dynamic events is worth it.

The articles that follow (from Neill Anderson as before) are in italics.

Article 9. The Assembly Process

Previous articles have reviewed the basics of determining the requirements of the event, looking logically at the options for solutions and choosing your own one which has now been designed and parts manufactured or procured.

From my past experience, as a Judge at Formula Student and indeed having been around many race car paddocks at circuits and hill climbs around the world, it is very fair to say that car assembly and preparation is often not quite as good as it should be!

Often the reason for this is not simply a lack of the necessary skills or conscientiousness; but more likely a lack of time caused by either genuine unforeseen circumstances (rare), or poor planning (more likely). The former does need to be learnt and the latter can be avoided.

Assembly is the physical process of joining together the many separate parts and components, whether bought in or “home-made” and the underlying connections to make the whole greater than the sum of the parts. Some of this joining will be mechanical (wishbones to chassis), some will be electrical/electronic (engine loom) and some will be hydraulic (fuel system).

Hopefully your design will be such that there are no superfluous parts on the car and therefore, by definition, it will take only one part that fails to cause the whole vehicle to fail.

Preparation is then more to do with getting the best from that assembly process and foreseeing inevitable likely failure points such that reliability is guaranteed….The priorities, in order, are that the finished vehicle be safe, reliable and quick.

Please note the following is information intended to assist: you remain 100% responsible for your own safety and that includes your individual reliance upon your own interpretation of any information.

Remember “Design for Manufacture”?

You will most likely not start with a huge build area and a whole box of neatly labelled parts and a grand instruction sheet like the Airfix kits you had as a child. Rather, in the usual timescales, you will have parts, components and sub-assemblies arriving on a piecemeal basis that get thrown in a corner somewhere. This will often be weeks after you/your talented team drew or bought them and possibly (although quite unlikely) weeks before someone tries to fit them all together.

It is now you learn the golden truth that anything fits together better if some thought to its assembly was included at the design stage. That includes not only general design principles but also tolerances, heat treatment effects etc. and what equipment and facilities you have available. In general there will always be something that you didn’t fully think about/appreciate/include/consider and rectifying it will always take longer/cost more than you ever imagined. But this is character building and educational and teaches not only good practices but teamwork and personal tolerance as well.

Basic Understanding

If you have never actually constructed something before, then any car, especially an FS car, is not the best place to start. Take your bicycle apart, your Dad’s lawnmower or something simple first. And then put it back together again! You need a feel for when something slips neatly in line/together, how to look for interferences preventing proper assembly and the good thing about starting with something already assembled is you know it does actually fit together!

Depending upon how much you have already made, versus bought/sub contracted, you will have some idea now that things don’t always go to plan. Your careful drawings, lovingly dispensed from your shiny computer needed very thorough checking for tolerances etc. and you may now have realised that fits and finishes are not quite how you envisaged them: if the mistake is yours you get to pay for the part anyway! Suppliers can often over promise and under deliver. If you have the equipment and the time included in your master plan then it is worthwhile checking parts, whether “home-made” or bought in (goods in quality control).

If things don’t fit then the most likely solution, in the timescales we have and the real world is to make it fit. Such solutions vary from the elegant to the plain brutal and there is a time for both extremes, sometimes even at the same time. Always bear in mind the potential safety risk and react accordingly: an exhaust silencer falling off is far less serious overall than a brake caliper falling off. But ultimately both will mean you fail to finish.

Why things fail when they shouldn’t

Most FS vehicles don’t fail to finish a dynamic event because of a once off structural failure as a result of under-estimation of the loads involved, or because the analysis was badly flawed. Rather most fail because of small assembly or preparation errors that could perhaps have been reasonably foreseen. The remainder fail due to fatigue, which is usually indicative of a lack of appreciation of some finer detail of a part or the real load cases. Sometimes fatigue is actually an assembly error; for example if you have driveshafts with the same joint at each end (inboard and outboard) and you remove it without marking the normal direction of rotation there is an equal chance of refitting it the “wrong” way round and thus increasing the risks of a fatigue failure (usually at the spline root or circlip groove).

There are many books that deal with car preparation (available from the usual suspects via the usual outlets) so this is only a brief roundup.

If we look first at mechanical attachments we can point out a few things that may not be totally obvious until we think it through looking for problems. As an example consider the ubiquitous suspension wishbone: this will usually connect to the chassis and/or the upright where the suspension “leg” terminates in a spherical bearing. Quite often the inner race of the spherical bearing is clamped between two “ears”, likely to be an aluminium clevis that is basically a channel section.

All bolted joints rely on the clamping force induced by the strain in the bolt to hold them rigidly together. If that “stretch” of the bolt be reduced then the clamping load and rigidity of the assembly falls off. This happens way before the bolt becomes loose and the nut parts company with the bolt with attendant disastrous consequences. As the stretch in the bolt is very small you only need a very small reduction in the “width” of the items being clamped for rigidity to disappear. Once that happens you are relying on the bolt to be a pin, it being a good fit in the clevis and spherical, there being no thread to mill through the clevis etc.

We usually use cap head (Allen socket head) set screws (bolts have thread for the full shank but I shall use the term bolt here for simplicity) and only if we are super rich can we use aircraft specification (NAS) bolts where we can precisely dictate the plain shank length. We use them because the heads are smaller and neater than standard hex heads and so less room is needed to install and tighten them. However this is also their Achilles Heel: the small diameter head means a small bearing area underneath it and so it will dig into your aluminium clevis, especially if you turn it while tightening it! You really need an adequately hard washer under it of adequate thickness. The same usually applies to the nut, the expensive but beloved K-nuts have an integral washer for greater area. But at least such bolts have a good underhead radius to the shank. Again if not using a washer then the part the bolt goes into needs a small chamfer to clear this radius….

In a similar manner the inner race of the spherical bearing presents, by design intent, a very small surface area. To get the angularity we will have spacers either side of the bearing and ideally, for ease of assembly, these will spigot into the bore of the inner race. As that contact area is small the spacers need to be of a suitable material, alloy spacers will not do. The end faces of the spacers (i.e. those in contact with the spherical and the clevis) need to be flat and parallel. The overall assembled width of the spherical with spacers needs to be just less than the open jaw width of the clevis.

So as you can see there is a lot of attention to detail needed. If you have any coatings, e.g. paint and you clamp up on that then the paint will be the first thing to “relax” and all your hard work will have been in vain. As ever, think carefully what the parts are there to actually do, and then think about what could happen to stop them doing it. And then work to ensure that does not happen.

With bolted connections pay attention to thread length and overall bolt length: the last thing you want is to be tightening the bolt or nut against the end of the threaded portion and thus not actually clamping up the joint. Finally Nyloc nuts are reusable assuming the threads they run down are not damaged: you only want two or three threads showing on the free side so you will be carefully cutting off the excess won’t you?

Your grand design should be capable of generating quite high forces, possibly around 1.5g in most directions. As such all of the components that are not fixed rigidly are going to be tempted to move in response to those forces. A radiator pipe carrying coolant has a not insignificant mass and therefore is subjected to significant forces, in all directions. Keeping that in place is not the job of the hose clips that join the pipe to the radiator or engine via flexible hoses. Even beading the ends of the pipe doesn’t do that. So consider carefully all the items like pipes, wiring looms, cables etc. and make sure that you mount them properly and carefully.

Most wiring connectors have terminals that are retained by some form of mechanical “lock” to ensure that the terminal cannot escape the connector body. Make sure that you use them and insert them fully home. The connectors themselves will almost certainly have a mechanical fastening to ensure they do not become inadvertently disconnected: but again they only help if you use them! Wiring looms can become quite bulky and heavy and so needs careful support. It doesn’t take much repeated movement to chafe through the wire insulation and cause all sorts of problems, up to and including fire.

In that regard it is worthwhile remembering that carbon fibre, and its dust, is conductive. So be careful with your electrical boxes etc. when doing that last minute trimming etc. on a composite tub.

Braided hoses, e.g. brake lines, oil pressure hoses have a propensity to be able to cut through almost any material over time: again it is a matter of checking clearances and envisioning potential problems and eliminating them before they happen.

Exhaust manifolds are prone to fatigue due to their environment: heat cycles and vibration, often hand fabricated without full consideration of the filler wire/rod and often mounted poorly. Leaving the silencer hanging off the end, unsupported is asking for trouble.

Why things feel bad

Another area that can often be a let-down and can be a general assembly and preparation problem is the control systems. We are regularly disappointed by the feel and precision of the control systems when we sit in cars to try them: massively excess free play (“slop”) in the steering, excess free travel or compliance in brake pedals, stiction in throttle action and gearshifts. All of these controls have safety implications as well as driver confidence impacts. Sticking throttles, failing steering and a loss of brakes are all disastrous events.

Throttle action is very much personal in terms of travel and force but no one ever said anything good about a throttle with stiction! Almost unanimously every driver likes a brake pedal that travels very little and feels rock solid. Getting a silky throttle feel requires a pedal pivoting on a proper bearing and with enough stiffness not to bend including sideways when heel and toeing. A stiff throttle stop is required and it also helps to have a return stop (this can stop the cable leaving its abutment when least expected). Set both accurately and check them from time to time because cables do stretch. Route the cable with generous bends and away from heat (many have liners that melt easily). You can arrange for the throttle action to be progressive, usually easiest to do at the throttle body end with a cam action lever, have a look at many production (those older ones with mechanical throttle bodies!) cars for examples. The simple inclusion of long throttle travel can mitigate a peaky power curve to a small extent.

Cut the cable to length neatly: the best way is usually with a flame as this quickly melts the open strands together, a good plumber’s blowtorch can sometimes be enough, and if not a TIG arc “flash” will do it. Cut the outer casing square and neatly and deburr inside. Blow through with the airline and if the cable has a low friction lining (good bicycle shops sell some good quality control cables) don’t use any oil. A push-pull cable takes up more room, is bulky and heavier and requires more open bends but has the advantage of being able to close a throttle by hooking a foot under the pedal. This may just be enough that one time to save the accident…. Also be sure to check the action of the throttle return springs at the throttle body to ensure they don’t go over centre and they cannot jam up on anything. Carry a spare throttle cable, already cut to length and ready to fit, complete with adjusters and end fittings etc.

The brake pedal needs far more structural consideration than the throttle (recall the Rule about pedal load capability) but also needs to pivot on a proper bearing and be stiff in all planes. Most of you will have front/rear split systems with separate master cylinders and a balance/bias bar. Again it is essential that everything slides together neatly, without binding and without any free play. It is most likely that the actual travel used in each master cylinder will be different and so you do need to set the system up so that when decent force is applied to the pedal the balance bar is square to the master cylinder axis. This may lead to a slight angle on the bar at rest, which is fine. Make sure you tighten all lock nuts and that the pushrod is not protruding through the balance bar clevis such that it interferes. Don’t have more than a small gap needed between the inside faces of the clevises and the balance bar housing/pedal sides. This is because in the event of a total failure on one circuit you need the clevis to jam against the side of the pedal assembly to ensure that the remaining good circuit can still take load. As with all these things it pays to try that when first assembling the car and most suppliers provide advice when you buy their balance bar assembly. Finally ensure that the pedal at rest allows both master cylinders to be fully “released” (sometimes does no harm to have a light spring pulling the pedal back against a stop) as otherwise the internal feed ports won’t be open and bleeding the brakes or pushing the pads back will be impossible!

The steering mechanism, from steering wheel to road wheel/tyre must be both strong and stiff enough. You will be surprised at just how much force you can exert via the steering wheel multiplied by the various leverage ratios to the rim! You will also be surprised at how much things flex and how quickly free play develops. You ideally need to support the column/shaft either side of any universal joint (UJ), in all planes and stiffly too. In general all supports will tend to add friction so again you need to consider this carefully. The universal joint cannot perform miracles and the greater the operating angle the less miraculous the result will be: greater shaft velocity variations, greater wear, strange tight spots etc. The beloved “helicopter joint” requires some good detail design to affix it to a tubular shaft such that it does not quickly develop play: just drilling a hole and tightening a bolt won’t do. Splined joints requires thought as to how you will assemble them, how you prevent the shaft from pulling back out etc. You also need to consider the weld area if welding the spline stub into the tube, filler rod etc.

Other Observations

There are often adjustable links with a left and right hand thread at opposite ends of the link. They are commonly used in suspension links to adjust the toe, used as push or pullrods to actuate the suspension and to hold wings (aerofoils) in place at the correct angle of attack. In theory such links are very purely loaded in tension or compression and so simple to analyse. They commonly have simple rod ends, one left and one right hand threaded, with locknuts. They are usually fabricated from a stock tube size with an insert welded (or sometimes bonded) into the ends. When done professionally the threaded inserts have a flat machined onto them to allow each locknut to be properly tightened.

Why explain that in so much depth I hear you ask? Well, it is very easy with poor assembly and poor preparation adjustment to end up with one of those links failing catastrophically. What happens is that the flats are not provided and the locknuts are tightened without full consideration of the actual relative positions of the rod ends to each other. So the locknuts only tighten because the two rod ends are “held” by their respective mountings. Usually the link then ends up with zero capacity to accommodate the angular displacement that dictated the use of the rod ends to start with. So as soon as the suspension moves up and down the lack of angular travel either tends to undo the rod end and locknut, or even worse, creates a large bending load in the exposed threaded shank and the rod end mounting clevis.

So now the carefully minimalist link and small rod ends are no longer loaded in pure tension/compression but instead will fail from fatigue in bending. As these rod ends are usually quite small and of metric thread form (often M6 in typical FS suspension toe links) such failure is usually both swift and dramatic. And often final.

When you assemble any components that move relative to each other always run the final assembly through its full range of travel to check for fouling. For a suspension corner without spring and with damper adjusted fully soft, and one link of the anti-roll bar disconnected there should be almost weightless fluidity to wheel travel. Equally on full lock there should be no restrictions caused by lack of capacity in the rod ends or spherical bearings; the inside of the rim should clear all the suspension links; the inside face of the disc musty clear all the suspension wishbones etc. The rack lock stops are there to limit the total steer angle.

Article 10. Car Setup

As usual with these articles this is aimed at first year teams and tries to steer you from the usual beginner mistakes and also tries to stop you panicking about things which are really not that difficult, time consuming or important. We can be business-like and call it “prioritising” if you wish.

By now you might have actually assembled your beast and hopefully ironed out the basic sub systems functionality. Time is very tight, maybe even non-existent and there is probably little left in the bank either. But before you can do even a shakedown run of your creation you do need to check again that it is safe and whilst doing that (spanner checking assemblies, wiring and plumbing checks etc.) you may as well take a little bit extra time to square it up so the wheels (and therefore tyres) are at the “correct” angles.

Despite popular myth you don’t need expensive equipment, a flat floor or lots of time to do a good enough job (for this sort of car in this sort of event). I would estimate if you have not done this before you need a space big enough to walk/kneel around the car, 4 axle stands, some string, a spirit level and two straight edges (or lengths of tube that by eye are straight), one that is approx. the tyre diameter in length and one that is about equal to the wider track width of the car. And a reel of cotton thread. Two lengths (2m each) of 15mm copper plumbing pipe is helpful.

You will also need something to weight the car with and to level the floor area locally under the tyres: vinyl floor tiles are great for this or even glossy magazines which can also serve as “turntables” under the front wheels. As your creations are going to be quite light then for about ￡30 you should be able to but 4 bathroom scales each of which will accommodate about 150kg.

I am assuming that you don’t have lots of time and so I suggest the following is order of priority: all measurements and adjustments need to be finalised for the vehicle complete with “average” mass driver and healthy complement of fluids on board. If time really runs out use the same order but do all measurements by eye: it’s amazing how good the human eye is for seeing lack of symmetry especially. The tyre supplier will provide some guidance on preferred angles and pressures and you should of course have understood those recommendations at the design stage…

It makes sense to quickly scheme up a “Set Up Sheet”, examples abound on the Internet but should be graphically obvious as to which is the front of the car. When undertaking his first set of adjustments you may have time to note the adjustment sensitivity, i.e. one full turn of the tie rod changes the toe by x mins or mm. Note this on the Set Up Sheet.

How to do these is explained after the list:

1.              When you assembled the car you should have set all the various adjustable parts equal side to side, and to your design specification.

2.              Level the floor under the tyre contact patches

3.              Ensure tyres are fitted correctly and symmetrically to the right ends of the car!

4.              Pump the tyres to something close to a hot (warm?) running pressure (note that this will likely be a few psi higher than the recommended cold starting pressures).

5.              Check each wheel/tyre for run out: rarely are wheels truly straight. Mark two diametrically opposite point in the rim of equal runout: these will be the positions you measure from.

6.              Ballast car or fit average mass driver

7.              Get ride height somewhere near and ensure that you have legal suspension travel in bump and rebound and are unlikely to bottom out severely anywhere when running. It should be equal left to right and usually the rear will be higher than the front for a variety of reasons (more complaint rear for traction, greater rear mass bias, aero, need to have a “pointy” front feel on turn in etc.)

8.              Set the front camber angles and then the rears. There is a massive difference in requirements between radials and cross plys. Many camber adjustment designs also influence toe, so do camber first.

9.              Set the castor angle at the front: if you don’t have much time at least get it equal side to side.

10.            Set the toe for each wheel, i.e. angle in plan view.

11.            Check camber again.

12.            Set corner weights accepting that if they are a long way off and using soft springs then you may have changed the ride height a lot and thus need to go round the car again from Step 8.

13.            Bolt anything loose back up tight. Every time, otherwise inevitably you forget to go back and torque it up.

How to do it

Almost everything you adjust will have associated influence: usually as you adjust castor you will also affect bumpsteer etc. Bear this in mind if you make significant changes.

1.           It is probable that to adjust some things you will need to jack the car up. For repeatable consistency you need the car to settle back to the same position each time. So you need to set all dampers full soft, and disconnect one anti roll bar link at each end to allow the car to be as supple and independent as possible.

2.           Roll the car into the working area, draw or mark around the tyre locations and move the car away. Using the level, shim the marked areas until the floor is level side to side. It is useful to mark on the floor the thickness of shims required to level the floor.

a.           If you prefer you can add the shims on top of the scales and do all the adjustments on the scales. You gain some clearance but lose the ability to roll the car back and forwards.

3.           Note tyre details

4.           Note tyre pressures

5.           You will do camber first so set the two marks to be vertical

6.           Add the driver or bags of sand!

7.           Measuring to the floor, or when really uneven, to a stretched piece of string stretched between the tyre/shim (ground) interfaces, set the ride height to your design specification. A ruler is adequate for this.

a.           If you don’t know the ride height then it makes sense to aim for about 30mm, as the Rules require an inch of travel and no bottoming out

b.           In almost all cases this will be done by adjusting the spring platform height to compress the spring.

c.           If you have some progressive connection (push or pull rods) then you really need to set the pushrod length initially to get the rocker in the design position and then adjust the spring collars to suit and then go round the loop again to keep the rocker in the right position at the correct ride height.

d.           Be aware that springs are notoriously poor quality and that that the end coils are “dead”, i.e. contribute little to the overall support. They are also quite variable despite what is marked on them, variances of over 5% are quite normal even in “good” springs.

8.           Camber next, and whilst a nice digital gauge is convenient you can make do with a spirit level or even a plumb line. And whilst it improves accuracy to measure over the greatest distance the tyre will bulge at its base and so it is usually easier to measure to the rim, where we earlier marked the two equal runout points.

a.           Calculate a simple angular camber to be a lateral measurement from true vertical across the rim diameter, e.g. 1 deg on a 13” rim is about 6 mm. hold the level against the straight edge touching the base rim point and when the level is vertical measure the gap to the upper rim point. Or vice versa if positive camber exists.

b.           Cross ply tyres work best almost vertical, radials need a lot more initial static negative camber generally, more so again at the front. 3 deg negative is not uncommon.

9.           Castor is hard to measure directly but you have the advantage that you probably know the relative locations of a feature on the front uprights, e.g. caliper mounting bolts. You can therefore measure directly the angles of these features in side view and relate back to the kingpin axis. Simpler still, and if in a hurry is to lay a straight edge across these bolts, one each side and simply adjust until they appear equal when viewed together across the car! A simple eyeball from above of the upper and lower balljoints will tell if you have any castor at all.

a.           If you have proper castor gauges they work by measuring the camber angle for a given steer angle at the rim. So you need some way to measure steer angle which can be lines chalked on the floor using a protractor! Glossy magazines under the front tyres will allow them to steer without moving the car.

10.         Now for the time consuming part. If you don’t have the fancy laser gear this is where it takes you a bit longer. What you are going to do is to create a perfectly square rectangle around the car from which you can measure in to the rims (the marked points) so roll the car ? of a wheel turn to get the marks horizontal. The simplicity of this method is that the string rectangle is referenced to the wheels and not to the chassis and thus allows for any asymmetry in link lengths etc. In other words it squares up the tyres’ direction relative to the other tyres, which is after all the important point.

a.           The reference rectangle will be constructed from stretched string, cotton thread in a contrasting colour to the workshop floor is best and it needs to be fairly non stretch. This needs to be at rim centre height.

b.           I find it easiest to get two 2m lengths of 15mm copper plumber’s pipe, and about 25mm in from each end and exactly the same distance apart (WFront and WRear in the sketch) on each pipe, I create a groove using the cutting tool designed to cut such pipe, the ones with the little roller knife wheel. Make a slight groove on the pipes without cutting through the tube wall, enough to locate our thread.

c.           Position an axle stand about two foot forwards and one foot outboard of each wheel front wheel and the same in reverse at the rear. We can then rest these pipes across the two rear stands and across the two front stands. They serve to keep the two threads equidistant from each other which saves a lot of time.

d.           Stretch the thread front to rear each side and ensure they are taught.

e.           Now measure from the thread each side to a fixed point on the wheel hub area, at centre height, e.g. to the flat face at the centre bore, to a brake disc face or similar. Note the measurement to about half a millimetre (this is quite possible with a steel rule and stretched thread).

f.            Get this dimension equal left to right at the front. LF and RF in the sketch.

g.           Don’t let anyone trip over the thread or kick the axle stands

h.           Do the same at the rear, the rear distance to the hub will most likely not be the same as at the front. LR and RR in the sketch.

i.            Go round in a few iterations until the car is central in the string box to within ? millimetre measured to the wheel centres

j.            Don’t let anyone trip over the thread or kick the axle stands

k.           Now simply measure the distance between the thread and the forward rim (marked point) and the rearward mark for each wheel. Write these down as you go for each wheel, toe out is when the forward reading is smaller than the rearward reading for a wheel.

l.            As a staring point perhaps aim for about 15 mins (15 mins is about 1.5 mm on 13” rim, quite convenient to remember) toe out per wheel for a pointy car. Bear in mind that any compliance that causes a wheel to wobble between some to in and some toe out will feel awful so where you have flexibility have enough static toe to avoid it going past centre etc.

m.         Adjusting the toe will sometimes cause the car to ”re-align” within the box, especially if you need to jack it up. Simply reset the box as per steps (e) to (j) again and remeasure. Note the sensitivity of the adjusters.

11.        If you made significant adjustments you need to check camber again.

a.           This may then entail another round of setting the toe!

12.        Corner weighting is again not mysterious or hard, just time consuming and easy to get frustrated by! Essentially you are looking to balance the car’s mass across the 4 contact patches, the basic accuracy of which is dictated by the car’s design mass distribution. However, at the expense of “perfect” ride height, you can adjust the individual corner weights by raising or lowering a corner: raise the ride height at a corner to increase the load carried by that tyre.

a.           With pushrod/pullrod linkages you want to do this on the link to keep the rocker at the desired geometrical position (most have significant rising rate in their geometry). For outboard suspension raise or lower the spring collar to change the spring preload.

b.           You should be able to do this whilst the car is on its wheels: if you need to jack it up then sometime sit is hard to be consistent and repeatable because of the dampers and any friction in suspension pivots.

c.           From a driver confidence perspective it is usual to prioritise minimising the difference between the two fronts but if you have limited rear droop travel and a weak LSD then it may be beneficial, performance wise, to prioritise the rears. Depending on the basic mass distribution you probably won’t get much better than 5kg difference across an axle.

d.           If you changed the ride height much, and depending on your camber gain characteristics you may need to go round again from Step 8.

13.        Reconnect the anti-roll bar links, ensuring they are adjusted to fit without any preload: they may well now be different left to right.

a.           Check everything is tight.

b.           Reset the dampers to where they were/should be. If in doubt err on the soft side as it is easier to feel excessive softness than the other way round.

c.           Check travel to the bumpstops: there should be some! Cheap bumpstops tend to be pretty solid and with minimal progression, proper ones can be used effectively as they are very progressive (rising rate). Very simply the more conical the bumpstop the better. Note the internal shape of the spring cap also influences the rate of the bumpstop.

d.           Measure the fitted length of springs, pushrods, adjuster links etc. and record them along with the car and driver mass and distributions. These will come in very handy should you take the car apart at any time.

If you really want to check things thoroughly then you can do a bumpsteer check, i.e. measure change in toe at each wheel at every ride height increment. You can do this inside the string box but you will need to remove the springs and have a jack or blocks of wood etc. under the car to support it.

It’s worthwhile doing if you have time but only if you have some method/adjustment available to correct it: usually this means shimming the vertical position of the steering rack or toe link pivot.

End of Neill's text.

Both Neill and I would like suggestions about how to improve this series of posts.

For my other posts see - https://www.dhirubhai.net/today/posts/willemtoet1 

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