It\u2019s strange that the first question people ask when they\u2019re checking out modified cars is often \u2018How much power has it got?\u2019 It\u2019s all well and good being able to say it\u2019s got 400 bhp, but how much weight is that power having to shift? If the car weighs two tonnes then you\u2019ve only got 200 bhp per tonne, which is suddenly less impressive. That\u2019s only equal to a 100 bhp engine in a 500 kg car. The thing is if you tell people you\u2019ve only got 100 bhp they\u2019ll snigger and walk away. \u2018Pfff, my Mom\u2019s Corsa has got more power than that\u2019. The conversation\u2019s over before anyone mentions weight.<\/p>\n
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Weight goes far beyond the simple bhp\/tonne figure though. Bigger engines will often produce more than enough power to compensate for their extra weight. Carrying a hoofing great engine around does nothing for the handling though. The overall weight of a car will make a huge difference to how it accelerates, brakes and turns into a corner. The distribution of the weight in the car is just as important and can be used to either tune or ruin the handling characteristics.<\/p>\n
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It\u2019s fairly obvious that having a light car means you can accelerate and brake faster, there\u2019s less weight to move around. But just as important is how the weight is spread out across the cars tyres. Each tyre is actually holding up a different weight. In most road cars with the engine up front, the front tyres are holding up a lot more weight than the rears. Likewise with only the driver in, the off side tyres are carrying more weight than the nearside. Amongst other things, the amount of weight (or down force) a tyre has on it will dictate how much grip it can produce, up to a point. From that you could think a heavier car could corner faster. The problem is that the cars weight also acts sideways in a corner and it takes some of the available grip of the tyre and pulls it sideways, causing the tyre to \u2018scrub\u2018. All tyres scrub sideways when turning, it\u2019s known as the slip angle.\u00a0 Push the slip angle too far and you\u2019re sliding, push the slide too far and you\u2019re spinning. Heavier cars increase slip angles faster than light ones so they run out of grip faster.<\/p>\n
To help ensure each tyre is carrying an equal load to start with, cars can be corner weighted. That involves raising the spring heights so more load goes onto the corners where there was less. Unless you have a very well balanced car the weight distribution will always be biased in one direction or another, but it helps to spread the cars weight as evenly as possible. This means each tyre is doing it\u2019s fair share of clinging your car to the road. Corner weighting a car doesn\u2019t necessarily move the weight distribution in the car, it just alters how the car\u2019s suspension supports it.<\/p>\n
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Of course all that talk of spreading the weight out on the tyres is massively over simplified. There\u2019s so many other factors influencing how the car\u2019s suspension behaves, and all we\u2019ve considered so far is how the weight is supported across the four corners. We should also spare a thought for where the weight is in the car. Rather than just say the car has weight, the weight distribution around the car can all be added up and said to have a centre of gravity. It\u2019s basically the balance point for all the weight in the car. If the car was hung from a rope attached at the centre of gravity it would always be balanced. The centre of gravity also has a height within the car. The higher the centre of gravity the more a car will lean as it corners. It leans, or rolls because opposing forces act on the centre of gravity as you corner. It\u2019s those forces you can feel when you are pushed out of your seat as the car brakes or corners. This is called weight transfer. The more it rolls during a corner the more it takes load off the inside tyres reducing the overall grip available to the car.<\/p>\n
The centre of gravity rolls around a pivot point called its roll centre, which is set by the cars suspension pick up points. Unless you\u2019re planning on moving the suspension pick up points the best way to reduce the amount of roll a car has is make it lighter and get the weight as low down in the car as possible. Stiffer suspension springs will resist body roll. Generally you\u2019ll always want the softest springs possible for traction but stiff enough to stop too much weight transfer. Assuming your tyres are up to the job of transmitting the load then sometimes a bit more weight transfer in a straight line (pitch) helps push them into the road surface and get more grip. For example if you have a rear wheel drive car with the engine at the front you\u2019ll need a bit of weight transfer to get the driving tyres to grip properly. Generally though too much weight transfer reduces grip and ruins the balance in the car, especially during cornering (roll). It\u2019s that balance that everyone\u2019s trying to find when they set a car up. How much weight your car has and where it\u2019s distributed will affect how much weight transfer you have, how much work your suspension is having to do and so how hard you can push your tyres when accelerating, braking and cornering. Performance driving techniques are all developed around shifting the balance around the tyres to get the best grip for the longest time. It\u2019s all of these factors and more that we focus on when developing a car, and it\u2019s driver.<\/p>\n","protected":false},"excerpt":{"rendered":"
It\u2019s strange that the first question people ask when they\u2019re checking out modified cars is often \u2018How much power has it got?\u2019 It\u2019s all well and good being able to say it\u2019s got 400 bhp, but how much weight is that power having to shift? If the car weighs two tonnes then you\u2019ve only got […]<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[106,27,29],"tags":[95,107,114,31,34,42,32,48],"class_list":["post-733","post","type-post","status-publish","format-standard","hentry","category-aa-sport","category-news","category-race-news","tag-4-wheel-alignment","tag-driver-training","tag-practical-performance-car","tag-race-car","tag-shell-preparation","tag-suspension","tag-track-day","tag-weight-saving"],"aioseo_notices":[],"_links":{"self":[{"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/posts\/733","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/comments?post=733"}],"version-history":[{"count":1,"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/posts\/733\/revisions"}],"predecessor-version":[{"id":734,"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/posts\/733\/revisions\/734"}],"wp:attachment":[{"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/media?parent=733"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/categories?post=733"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/aasilencers.co.uk\/blog\/wp-json\/wp\/v2\/tags?post=733"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}