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Wheel spin happens when the forces applied at the contact patch exceeds the tyres grip. If you try to apply these high forces at low speeds, you generate wheel spin. You, therefore, end up wanting to choose ratio’s that enable you to deliver tractive force as close to that line as possible. More on this in a minute … 2- Traction LimitĪt lower vehicle speeds you can see the tractive forces are very high. The gear ratios, therefore, aim to compensate for this (it is their whole purpose really.) This is because your engine is not delivering peak power at all speeds. The tractive force curve, therefore, informs your limit in terms of what your engine can deliver – it becomes your target. It represents the best your racing car could produce. What it is saying is that if your racing car could generate its peak power at all speeds, then this is how much (tractive) force your racing car would be able to put down on the road. Super important point – this curve is totally independent of your gears. The Tractive Force curve shows you the force your racing car can put down at the wheels as your car increases in speed. On the x axis you have vehicle speed (kph). The primary theory to consider is the concept of Tractive Force. Once you understand these limits you can select optimum gear ratios to match. The following 3 theories combine to define your racing car’s limits. You can take your racing car parameters (and this theory) to then work out the best gear ratios (and final drive) for any track. The good news is that there is some theory and some formulas that you can use. ? If you can change the gear ratios you have the opportunity to run an optimum setup for best performance.īut how do you choose these optimum ratios? Three Bits of Theory One you now need to find!! – as if you are not running the optimum, then you are giving away performance unnecessarily.įlipping that into a positive. If you can change the ratios (and/or the final drive ratio) then there will be an optimum setting for your racing car for each track. When you have freedom in choosing the best gear ratios it can actually become something of a mixed blessing! These restrictions, whilst a pain in terms of pure performance, do have the beneficial effect of often making your gear ratios selections one fewer thing to worry about!
#GEARCITY GUIDE SERIES#
These are either specified by the series you race in or by the gearbox design. With real racing cars (verse simulators) there are always limits on the ratios you can choose. But that is only for those specific gear ratios.
#GEARCITY GUIDE HOW TO#
You already know how to determine your best gear change RPM for each gear ? (no? – seriously have a read because this article builds on that one) And, as you are already shifting gears at the best possible RPM points, you will already be getting the best possible acceleration. You want gearbox ratios (inc a final drive) that ensures you hit maximum speed on the straights, whilst ensuring you have the best possible acceleration at launch and coming out of the corners. Even if your ratios are all fixed it is worth knowing what “ best” looks like and this method and spreadsheet give you that.
#GEARCITY GUIDE FREE#
Knowing you have the best gearing is basically free lap time – or unnecessary lap time loss if you get it wrong. By the end of it, you will have a solid understanding of what goes into defining (and then selecting) the very best possible gear ratios for your racing car. And not only for your racing car on a drag strip (unless that is your thing) but optimised for your racing car on a specific racetrack. If you have a choice, then what you are after is a certainty to know that you are running the very best gear ratios possible. Equally, you have the chance to get it spectacularly wrong with a poor one.
Yes, on the one hand, you have the chance to gain performance with a better choice. Having that freedom to choose can be something of a mixed blessing. One who is also a sim racer it seems, and hence why “total freedom” is a real option. “Samir, how would you go about choosing the best gear ratios for your racing car – if you had total freedom? (or at least some ratio choices …)”Ī deceptively simple question sent in from a reader.