Gear Ratios - How to Choose?

Gear ratios act as leverage, allowing the engine to multiply torque at the wheels at the expense of top speed. The reason we have multiple ratios is so we can reach our desired top speed, while putting down the maximum torque possible for any given gear. For road cars, this also increases efficiency at cruising speeds, usually by reducing revs.

In theory, why not use as many ratios as possible to maximize torque at the wheels, while retaining high top speed?

The first constraint is weight. More gears means more weight, negatively impacting both performance and economy. It also requires more space to house a larger gearbox. This is shown by the Koenigsegg Regera, which used a single speed gearbox to save weight since its powertrain produced enough torque to propel it from 0-250mph.

You also end up shifting gears too much. Every gear change requires time not spent delivering power to the wheels, hurting performance. This couples with suitability - too many close gears means you won't use the full range of an engine's torque curve, wasting potential. However, there are exceptions, like the 10-speed in the Lexus LC. It shifts in 0.12 seconds, around 1/10th the time of a manual. This keeps the V8 at peak torque while enabling efficient cruising with extra gears.

Ideally, gearing would perfectly match the engine torque curve, utilizing its full width and changing at the right rpm each time. But perfection isn't possible due to manufacturing constraints. Ratios must work for many engines in varying states of tune.

So how do you choose the best ratios for a given car or track? Ask an aftermarket transmission manufacturer and they may provide guidance. They likely know if your 1st will be too long or short, and your top gear should max out just above your fastest achievable speed. Then space evenly in between. It's a solid approach that has worked for years.

We take a slightly different, data-driven approach based on decades of experience to find the ideal options. First, we analyze your engine dyno graph, a constant. Then your tire size, as you may have multiple options. Also the final drive ratio, as there may be a few choices. And finally, the gear ratio possibilities.

We also factor your desired maximum speed and the speeds you'll be at most often. Our program is designed to maximize torque at the wheels in your typical speed range while meeting the top speed requirement. We provide rpm shift points per gear, as these may vary given the engine torque curve and rev drop.

The result is gearing tailored precisely for your engine and intended use - whether general street driving or per racetrack. This is a standard service for our customers, but we also offer it as a standalone consultation for race teams, drivers, and anyone serious about optimizing their vehicle.

The process provides an initial consultation, data on all the possible options, with their respective top speeds per gear, ideal shift points, and torque delivery between common speeds - ranked by torque and acceleration gains. We compare and select the one yielding the highest acceleration across your typical operating range. This is followed up with a written report and conversation to ensure you're satisfied and address any questions.

Anything less is guessing. Even on a popular Quaife 60G, there are 38 possible 1st-6th gear ratios. It may be an educated guess, but still a guess. Nothing replaces hard data, and for thousands spent on a gearbox or kit, isn't it worth doing properly to maximize performance?

This is where our bespoke gear ratio consultancy service comes in. For race teams and drivers, we dig deep into the data to find the ideal ratios for your exact engine, tires, and intended use - whether that be all-around road performance or optimized for certain racetracks.

Our decades of experience allow us to take a data-driven approach based on your engine's unique torque curve, the speeds you'll run most often, and your goals - be they maximum acceleration, top speed, or cruising rpm. We identify the ratios delivering the greatest torque to the wheels when you need it most.

The process begins with an initial consultation where we learn your goals and gather key data like engine dyno graphs and potential tire and final drive options. From there, our optimization software crunches the numbers on all the gear ratio possibilities.

You receive a detailed written report with all the data - the torque and acceleration available in each scenario throughout the rev range you'll use most often. We walk you through the findings over a follow-up call to explain the results and ensure you understand how we arrived at the ideal ratios for your application.

The benefits of this bespoke consultation include:

Gearing optimized for your engine's unique torque curve & operating rpm range

Maximized acceleration when you need it most, e.g. exiting corners

Ideal cruising rpm range for efficiency & drivability

Higher overall torque to the wheels through meticulous ratio spacing

Detailed data-driven analysis versus guesswork with off-the-shelf gear kits

Written report explaining the methodology and how we identified the ideal ratios

While off-the-shelf gear kits provide a starting point, they make compromises to fit a wide range of applications. In contrast, our analysis ensures your transmission is truly tailored to your vehicle. We match the gear ratios precisely to your torque curve, tires, final drive, and intended use.

For instance, on a 1800kg sports car with a 400 hp V8, we may determine an ideal 1st gear allowing aggressive launches while preventing premature redline. The ratios would be narrowly spaced in 2nd through 4th to keep the engine in its torque peak around the track. 5th and 6th might enable efficient 70-80 mph cruising at under 2,000 rpm.

The result is a transmission purpose-built for your car, delivering maximum acceleration and drivability. And the detailed report provides insight into how the ratios deliver superior torque compared to off-the-shelf options. Our goal is to educate enthusiasts while providing value through bespoke service.

Shifting gears does require time, thus not transferring power to the road, hurting acceleration. But modern dual-clutch transmissions like those in the LFA and latest Ferraris shift in just 50-100 milliseconds. This keeps the engine in its ideal operating range while eliminating the compromise between acceleration and top speed necessitated by manual transmissions with just 6 gears.

The Lexus LFA's incredible naturally aspirated V10 redlines at 9,000 rpm. Its 6-speed automated sequential gearbox utilizes close ratios in the first 5 gears along with a taller 6th to achieve a top speed of 202 mph without sacrificing acceleration from its high-revving engine. The LFA hits 60 mph in just 3.5 seconds thanks in part to gearing keeping the engine in its powerband.

So while often beneficial, more gear ratios do have tradeoffs. Additional gears increase transmission weight and complexity. More ratios also raise the likelihood of undesirable gear hunting, slowing acceleration as the computer struggles to choose the optimal gear.

These downsides often outweigh the benefits beyond 8-10 ratios for most applications. But data-driven analysis can reveal whether additional gears offer meaningful torque and acceleration gains for your exact vehicle specs and intended use. Our consultations provide the hard data necessary to make this judgement call.

We take a scientific approach based on your goals, data, and experience. In contrast, trial and error testing to find ideal gear ratios requires enormous expense and time investment. Short of extensive testing, computer-aided analysis using accurate models is the best way to simulate real-world performance with various gearing options.

Our optimization software combines vehicle dynamics physics and proprietary engine maps to predict acceleration, top speed, and fuel efficiency with a given transmission configuration. We input key data like engine torque curves, vehicle weight, aerodynamics, and intended gear shift points. The software models performance in extreme detail - accounting for factors like transient torque loss during shifts.

This modelling enables simulating all gear ratio combinations to determine the ideal setup long before cutting steel. The end result is a detailed report recommending the optimal gearing for your situation. We discuss the findings to ensure you understand the methodology and results in practical terms. This bespoke service offers tremendous value for money spent on transmissions.