FH6 Gearing Guide — Gear Ratios for Every Track

Gearing is the difference between a car that pulls hard out of every corner and one that bogs down or bounces off the rev limiter. It costs zero PI to tune, and unlike suspension settings where personal preference plays a role, gearing has mathematically correct answers for any given engine and track combination. I've built a gearing calculator methodology that I use on every car I tune, and it's worth 0.3-0.8 seconds per lap compared to the stock gear ratios. Here's how it works and how to apply it.

How Gearing Works in FH6 — Ratios vs Final Drive

Individual gear ratios set the spacing between gears — how much RPM drops when you upshift. The final drive ratio multiplies all gear ratios together, effectively shifting the entire gearset up (numerically lower = taller gearing = more speed per RPM) or down (numerically higher = shorter gearing = more torque multiplication = faster acceleration but lower top speed per gear). Think of individual gear ratios as setting the shape of your acceleration curve, and the final drive as sliding that entire curve up or down the speed range. A 3.73 final drive makes every gear shorter than a 3.31 final drive on the same transmission. Two cars with different final drives can have the exact same gear spacings but completely different top speeds and acceleration characteristics.

The relationship between your engine's power band and your gear ratios is what determines acceleration. Every engine has an RPM range where it makes peak power — for naturally aspirated engines this is typically 7,000-9,000 RPM, for turbo engines it might be 5,500-7,500 RPM. Your goal with gearing is to keep the engine in this power band as much of the time as possible. When you upshift, RPM drops by an amount determined by the ratio gap between gears. If the RPM drop is too large, the engine falls out of the power band and acceleration dies. If the gap is too small, you spend too much time shifting — each shift takes about 0.3 seconds where you're not accelerating at all.

Tuning Gears for Specific Track Types

Short Tracks — Close Ratios, Lower Top Speed

On tight circuits like Guanajuato or the technical street routes through the city sections, you never reach top speed. The fastest cars on these tracks spend most of their time in 2nd-4th gear between 40-110 mph. For these tracks, set the final drive so the car hits redline in top gear at roughly the maximum speed you actually see on the longest straight. Then space 2nd through 4th gears close together — a 15-20% RPM drop between gears keeps the engine in the power band through the constant upshift-downshift cycles of a technical track. 1st gear should be tall enough to avoid wheelspin on launch, and 5th gear can be an overdrive that you never use. The goal isn't top speed — it's minimizing the time spent below the power band after each upshift.

Highway / Top Speed — Tall Final Drive, Wide Spacing

Highway pulls and top speed runs are about one thing: maximum velocity at the end of the straight. Set the final drive so the car hits its power peak (not redline — peak power RPM specifically) at the speed you're targeting. If your engine makes peak power at 7,200 RPM but redlines at 8,200, tune 6th gear to hit 7,200 RPM at your target speed, not 8,200. The car will continue accelerating past peak power, but it accelerates hardest at peak power, so you want to spend the most time there. Gear spacing on highway builds should be wide — you're not doing much shifting, and the time spent between gears matters less than having the right ratio in top gear. The tuning calculator visualizes this relationship between gear ratio, final drive, RPM, and speed.

Three Common Gearing Patterns

60/40 split: The first 60% of your gear ratios are close together for acceleration, and the remaining 40% are wider for top speed. This is the most common pattern for balanced circuit cars in A class and above. Example on a 6-speed: 1st through 3rd have small RPM drops (1,500-1,800 RPM), 4th and 5th have medium drops (2,000-2,500 RPM), 6th is a tall cruising gear. This gives you snappy acceleration out of slow corners with the close low gears, and enough top end for the straights.

Linear spacing: Every gear change drops the same RPM. On a car with a 7,500 RPM redline and linear spacing, each upshift drops to 5,500 RPM regardless of which gear you're in. This is mathematically optimal for cars with a very flat torque curve — electric cars, turbo engines with broad torque plateaus, and supercharged V8s all benefit from linear spacing because the power band is wide enough that the same RPM drop works everywhere. It's also the simplest pattern to tune: just set each gear so the RPM drop is identical.

Progressive spacing: Gears get progressively wider as you go up the gearbox. 1st to 2nd has the smallest drop, 5th to 6th has the largest. This pattern accounts for aerodynamic drag — at higher speeds, acceleration slows down anyway because of air resistance, so spending the RPM budget on close high gears provides diminishing returns. Progressive spacing puts the tightest ratios where acceleration is fastest (low gears) and saves ratio budget for top speed in high gears. This is the pattern I use on 90% of my road racing builds.

How to Identify Gearing Problems

Hitting the rev limiter before the braking zone: your gearing is too short. The car is topping out in the gear before you reach your braking point, which means you're coasting at redline for the last 100-200 feet of the straight. Every moment on the rev limiter is lost acceleration. Lengthen the top gear or raise the final drive until you're just kissing redline at your braking point.

Bogging out of corners: your low gears are too tall. When you exit a slow corner in 2nd gear and the engine RPM is below the power band (typically below 4,000 RPM on most engines), the car struggles to accelerate until the revs climb back up. Shorten 2nd gear or lower the final drive so corner exit RPM lands in the meat of the power band. The difference between exiting a corner at 3,800 RPM and 4,800 RPM can be half a second down the next straight.

Frequent shifting in the same track section: your gear spacing is too close. If you're grabbing 4th gear for half a second before braking for the next corner, 3rd should have been longer. Each shift costs time — about 0.3 seconds per shift in FH6 with manual w/clutch. Over a lap with 20 shifts, that's 6 seconds. Over a 3-lap race, that's 18 seconds of not accelerating. Proper gearing minimizes unnecessary shifts by covering the speed ranges you actually use.

Using the Gearing Calculator — Start with Final Drive

The tuning order matters: final drive first, then individual gears. Set the final drive so the car's theoretical top speed (at redline in top gear) is about 5-8 mph higher than the maximum speed you actually reach on track. This gives you a little headroom for the draft and ensures you're not on the limiter before the braking zone. Then adjust individual gears starting from 1st: set 1st gear so you can launch without excessive wheelspin — a bit of spin is fine, but if 1st gear is all wheelspin and no forward motion, lengthen it. Set 2nd for the slowest corner on the track — you should exit that corner near the bottom of the power band in 2nd. Set 3rd and 4th for the medium-speed sections and the exit of faster corners. Set 5th and 6th for the straights — these are your speed gears. Use the FH6 tuning calculator to model the RPM drops between gears before you hit the track. It saves you from doing the math manually and lets you visualize the entire gear curve.

The best gear tuning advice I can give: tune for the track, not for the spec sheet. A car that looks good on paper with a high theoretical top speed might be slower on a technical track than a car geared 15 mph lower that stays in the power band through every corner exit. The best cars by race type all share one trait — their gearing is matched to the specific demands of their discipline. A drag car's gearing would be terrible on a road course, and vice versa. Always tune gears for where you're driving.