Spreading the word on racing on a really tight budget. Sharing knowledge found the hard way.
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Suspension kits worth having cost about £600 upwards, to many of us that is more than the base car cost! But there are some budget options.

Circuit racing
The basic change needed to any road car for circuit racing is to lower the centre of gravity and increase roll resistance so that the tyre is in full contact with the road over its full width. Usually this has to be compromised a bit because of roll and constraints of the base car design.
So, lowering the car is usually the best starting point. Spring kits for some cars can be reasonably cheap, but beware of very cheap parts because the spring rates can vary wildly and upset the cars balance. Best use a brand that other racers of your sort of car go for.
Don’t be tempted to make the springs too hard, Graham Chapman is said to have worked to the principal ‘softly sprung – firmly damped’ in order that a wheel can move effectively and freely enough to do its job.
As a rough guide to rates (as seen at the wheel, so the actual spring will have a higher rate depending on where it is fitted) a standard road car might be 100 lb/in, a sports car about 150 and the old British Touring Cars were in the 300 range at the front. Rears tend to be a lot lower, possibly half the front. My old Rover SD1 ran 300 in the front struts and 100 in the rear coil-overs that used the old damper mounts which are more outboard than the original spring mounts, and it handled beautifully.
Real racing springs are surprisingly cheap, about £10 each depending on size. They come in two main diameters; 2.5 inch or 1.9 inch so you need to do some modification to make them fit. If you have struts then you can weld on threaded tubes, usually about £20 each, which have adjustable spring seats so you can vary the ride height and set each corner up precisely. If you don’t have struts then you would need coil-over dampers, which are very expensive and you end up spending a similar amount to if you had bought the full suspension kit but with the benefit of full adjustability.
Another spring option is to cut a coil off the standard springs, although this does have problems. Cutting one coil off will lower the car significantly and also make it stiffer (going by ratios; if it had 10 coils and you cut one off then it will be 10% stiffer), but the cut end must be profiled to sit in the spring seat properly and this is where the problems start. Most springs are flattened at the end and bent so as to form an even surface, spreading the load across the spring seat. If you just cut one coil off you end up with a point loading on the seat which can damage it and lead to failure. Also any heat applied during the cutting will change the spring stiffness, so if you are not carefull you can end up with different rates on each side of the car. But using a hack saw and a file some people have achieved reasonably acceptable results. Alegedly.
Another option is using standard springs off a different model, on my V12 XJ-S I used the ‘Sports Pack’ springs off the six cylinder model. So look at what other models used the same type of suspension.
Which ever way you choose to lower the car, there will be an optimum ride height, most car suspension changes camber as it moves so if you go too low the wheel will be tilted too far over and you loose grip. As ever the best starting point is to ask other racers what ride height they use.
Dampers are obviousely critical, much more important than the springs. Adjustability is nice but comes at a price, far more important is consistant reliable operation. Because dampers get hot when used their performance changes, cheap adjustable dampers should be avoided as should second hand ones, you just don’t know how worn they are. A good starting point is to use quality non- adjustable dampers, most brands do a ‘sports’ damper for about £40 each.
Of course some times you can grab a bargain from someone elses misfortune, unfinished projects come up for sale far too often and can have lots of nice new bits nailed onto a rusty shell, so keep a look out.
As for rubber bushes, you may be tempted to replace them with polyurethane performance items, but beware as cheap bush sets are very poor quality and can fall apart when used in competition. Decent bush sets will cost above about £150 but new standard rubber items are surprisingly good. Some bushes have a gap or ‘void’ in them to reduce noise, sometimes these can be fitted in a different orientation it stiffen things up, for instance my Jag has void bushes in the trailing arms that link the rear hubs to the chassis, rotating the bushes 90º moves the voids from front/back to left/right and so acceleration and braking forces are transmitted to the chassis more directly. Don’t be tempted to remove all the bushes and make solid ones, most suspension relies on some compliance to avoid locking solid, plus the fact that a little give in the suspension will help prevent things bending when you hit a kerb.

 

Off road racing
Similar rules apply, you need to get as low as you can but still maintain a safe ground clearance, particularly when landing after a big jump.
For Land Rover based racers there is a huge range of standard springs available, from the massive springs of a 130 Defender hi capacity crew cab to the light spring from and original Range Rover. Other manufacturers also have a range of springs from different applications.
Dampers for off road racing get a hell of a hammering and so get very hot indeed, I used Fox 2.0 dampers on my Tomcat and they were too hot to touch after just a few miles of competition, bigger dampers with remote reservoirs are better but then costs just get silly with each damper costing about £200 upwards. A better budget option is to use quality standard dampers (about £40) but doubled up, or in extreme cases use three, thus sharing the work and heat between them. Obviously this needs some mods to the axle and chassis but they are usually not too difficult. Again see what other racers in your chosen class do.
Which ever way you go the secret to good off road suspension is long wheel travel, the art is to keep all wheels on the floor no matter what shape the terrain is. This makes anti-roll bars problematical, it is usually better to engineer in a reasonable amount of roll resistance into the front suspension, but keep the back end supple enough to drop into big holes or off side slopes without causing a front wheel to wave in the air. This can be done by running higher spring and damper rates at the front but also suspension geometry can help, for instance the Range Rover style front ‘hockey sticks’ bind up in roll giving inherently high roll resistance and so firmer bushing will increase this.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

©Ralph Hosier