I have my custom gearsets pretty much dialed in with my final drive, but l’ve seen power to weight ratios mentioned in determining your final drive ratio. I can’t seem to figure out how to apply this, as sometimes you end up with a 6 or 7 to one ratio. I know it’s relevant, and it’s driving me nuts. Please, don’t tell me not to worry about it, or just use a sport transmission. The race tranny has better shift times, and improves handling and braking, so please, unless you have some insight into my question, keep all of your personal build preferences to yourselves. I have my A class times down to mid to low 3’s for 0-60, and high 7’s or low 8’s for my 0-100, so l’m not struggling to get good launches or accell, and my top speeds are on point with no rev limiting. My gearing is good. I set my tranny gears from scratch using math, and never have to adjust anything, l’m just a perfectionist, and know for a fact that there’s a way to apply your pw ratio to your gear ratio, specifically your diff gears (final drive). Thanks in advance
If you have your gear ratios set how you want them go to the highway and tune your final drive so your car reaches its top speed in your last gear. Your power:weight ratio isn’t necessary.
I figured it out. Not necessary, but it’s butter smooth and fast af. Wasn’t final drive. It’s first gear. Download and try one of my offroad tunes and tell me custom gears aren’t worth the trouble.
Instead of editing my original post, l thought l’d just update it here. It wasn’t final drive. It was 1st gear. I got all my favorites set using my pw ratio for my first gear and differential settings, and it was definitely worth the time it took to figure it out. I have a couple of adjustments on my gear progressions to get closer to a 10:1 in first gear, but my times are getting better. I got my A class barn find escort down to 0-60 in 3.333, and 0-100 down to 7.7 something. With a 170 plus top speed with almost no wheel spin on takeoff or otherwise.
You’re not going to share how you used power to weight ratio in determining gearing?
Bummer, I was really interested in hearing how that’s possible.
I didn’t realize anyone would be interested. Divide total weight by hp, divide total weight by torque. You’ll get two numbers average these and it puts you in the powerband. This is your final drive. Use my method outlined in my “custom gearset” post. I suggest you divide your final drive by .70. The difference between your 1st gear and final drive will also be your differential setting, and 25 to 33 pct seems to be the sweet spot for pretty much every car. On rare occasions the pwr will be too high to apply straight away, so you’ll need to divide in half or by 1.5, to get your pwr to line up with first gear and the powerband. This is the case with some A class cars and/or low hp high weight rides. Raptor A class 10 speeds are super fun.
So, if my car makes 900HP and 900TQ, set my final gear to 9.0?
Only if your total weight is 8100.
Weight/HP = a
Weight/TQ = b
(a+b)/2 = your final drive
Hope it helps.
Proven method:
For cars with standard Forza 6-speed race gear box (2.89, 1.99, 1.49, 1.19, 0.94, 0.78):
Subtract cars power from 400hp, divide by 600 and add it to 4.25:
Example: 325hp
400hp-325hp=75hp
75hp/600=0.125
4.25+0.125=4.375 → Final Drive: 4.38
For cars with custom race gear box:
Subtract cars power from cars stock power, divide by 600 and add it to stock final drive:
Example: 325hp, stock power 300hp, stock final drive 3.30
300hp-325hp=-25hp
-25hp/600=-0.04166667
3.30-0.04166667=3.25833333 → Final Drive: 3.26
Thanks fifty inch. Not gonna lie, though, that is super confusing to me. You the same fifty inch that developed the forza tune apps? And yeah, Bat is right. That was the best method that l found. All that being said, your differential setting is the differential between 1st gear and final drive. I abandoned the whole pw ratio method, and just set my 1st gear and final drive to be 30% apart, while maintaining near optimal 0-60/100 times. You end up with a final drive between 3.60 and about 4.40. The pw method was good for handling and staying within your powerband, but you rarely end up with optimal launch times. My newest method is a great balance. I appreciate the feedback and advice, but l realized the pw method gets you close, but it takes tweaking and you end up with differential settings that are all over the board. Overall performance is good, but launch times are lacking. I like 30% differential because when you adjust accel and decel, it’s linear with your weight distribution. So, on a 60/40 and a 30% diff, my front decel is at 20, and front accel, at 20 or 25. Holds true with any weight distribution. I’m more interested in optimal spring rates right now. I’m happy with my gear methods atm. Great launch/accel, top speed, and always in my powerband. Researching spring rates, lat g’s, and damping. My tunes handle really well, but l’m a perfectionist and know there’s an optimal setting for springs and damp, based on body weight, ride height, etc. I’ve found the info, but my mathematical limitations have become painfully obvious. Equations/formulas look like a foreign language to me. Anyways, thanks again, Happy racing.
Yes I’m the QuickTune man 
From my experience hp is the only factor that impacts gearing in Forza. Think of it like this: when you upgrade to a race gear box Forza needs to calculate exactly the PI impact for each and every engine configuration. Which means Forza needs to have an understanding what the optimal gearing for each engine configuration is. That’s why they’re running a simple hp based model here that scales either to a fixed reference point (400hp/4.25 final drive) for cars with the generic Forza race gear box or to the cars stock configuration (stock power/final drive) for cars with custom race gear box.
Different engines, power curves etc. don’t really matter, just hp. I know that this is a bold statement but I have a lot of proof that it is like that.
Ok, l gotcha now. I’ll definitely try it out. I can’t argue with the logic of hp being the sole factor. I’m using a standard gear progression with a set differential, so the final drive is the only figure l need. I’ll have no problem staying within the torque curve. I was having trouble with the logic of it. Like where did the numbers come from, but now that l see the reasoning, l realize it’s worth wrapping my head around the math. I shoulda payed more attention to the maths in school…lol Care to share a layman’s spring rate formula? My method is super close, but l doubt it’s anywhere near optimal. I realize fine tuning is a preference, but l’d like to start at absolute optimal for load/travel, then work from there. But again, the formulas l’m finding are hard for me to interpret. Check out any of my “Grp.1 or Grp.a” named offroad tunes, and give me a little feedback as well if you don’t mind. Everything l do is based on basic math, too. Very little “feel tuning”. Taking them through telemetry tonight. Working on contact patch and getting the suspension and ride height dialed into the sweet spot, so it hovers around the center. Thanks for the advice. I’ll get back to gear work in a few days, l’m sure. I’m always tweaking and exploring new concepts. Gg bro
One note though: the method works best if you leave the gears itself untouched. Just change the final drive.
As for spring rates: there is no one formula that suits all cars. Instead you need to chose spring rates that match the car type (body type) and drive train of a car. Have a look at my tuning guide, I’ve written it for Forza 7 but most if it applies to Horizon 4 as well.
I like this, fifty, seems similar to what most of my tunes have been so far. Lately I’m trying to use stiffer springs and dampers, see if I’ve been erring on the soft side of things too long. I used to think anything over ~6 bump was stiff enough to cost significant grip; I’ll do some laptime testing today and take stiffer tunes into PVP to see if I feel more settled while still placing well.
(From: Forza 7 Tuning Guide | QuickTune - Professional Tuning Calculator for Forza Motorsport 7 and Forza Horizon 4)
"Usual ranges (RWD):
- Production cars: Rebound: 7-8 / Bump: 4-5
- Race cars: Rebound: 8.5-9 / Bump: 4-4.5
- Prototype race cars: Rebound: 9-11 / Bump: 5-7
- GP race cars: Rebound: 9-13 / Bump: 5-9
Usual ranges (AWD/FWD):
- Production cars: Rebound: 6.5-7.5 / Bump: 3.5-4.5
- Race cars: Rebound: 8-8.5 / Bump: 3.5-4
- Prototype race cars: Rebound: 9-11 / Bump: 5-7"
Update: Been testing with an S1 2013 RS4 Avant, V10 swapped and 50% weight, 305 tires all around, presumably a good choice for this sort of test.
8.5/8.5/8.5/8.5 dampers on ~850lb springs, my best lap of 2 flying was slower, than 10/10/10/10 dampers, which also seemed more intuitive to push hard.
All 11, little slower, worse response. All at 12, everything suffered. 13/13/7/7 ran similar times as all 10, just lazier.
Idk. It’s hard to stay focused on tuning my dry road cars when matchmaking puts me in dirt, cross country and wet road races, that all require vastly different tunes. Any time I play ranked I end up in a cycle of, X discipline, X car needs something, go back to SP, tweak it a bit, enter matchmaking… totally different discipline/PI. Repeat.
Please note that the tuning guide is intended for F7 (gonna make an update for H4 soon).
Damping and Diff are actually the biggest differences between F7 and H4. You need to run slightly higher bump and much higher rebound in H4 compared to F7. Also reference point for diff in H4 is 75/75 compared to 70/35 in F7 which means you need to run slightly higher accel and more than double decel in H4 compared to F7.
I’m pretty sure that QH4 bump figures are under 50% of the rebound for everything I’ve used it on… Sometimes it is way under 50%. This comment really surprises me.
Well it doesn’t contradict my statement. You’re right bump is usually under 50% of rebound, still both bump and rebound need to be set higher in H4 as compared to F7 mainly because H4 uses a larger range (1-20 instead of 1-13) for race suspension at least.
I see. I just used that 50% as a sort of standard because of the in game menu’s suggestion of 50-75%, but I understand those menus haven’t changed much over the years. I’m usually getting rebound figures in the 8-12 range and bump in the 1.5-4 range. I wasn’t sure if something was off with my builds or not.
Just noticed this post. I feel that, and line corrections upset the chassis less.
Since discovering the origin of the tuning menu’s suggestion of “50-75% bump ratio” I believe it is archaic and irrelevant to modern dampers tuned for racing. All of my tunes are currently equal or less rebound than bump to perceived positive effect. Compared to older setups with more rebound, they are more grippy, agile, progressive past their limits, and predictable.
Ignore the ranges. Dampers only need enough resistance to control chassis movement during driver inputs. Too much will reduce grip (sometimes, that can be useful). Use whatever rates you like… take note however of the relationship between damping and spring: 4 to 8 is my typical range for road damping, 2 to 4 offroad, road springs 300 to 700, offroad 150 to 300. I have yet to use as much as even 9 damper on a tune I could comfortably recommend to anyone.
The weakest link in my performance/experience is still the gamepad steering algorithms IMO. Been thinking that since FM4.
Having seen a couple of GreatFlea’s posts, I’ve been testing higher bump than rebound… (circa 1.1rebound)
And I’ve run my best lap times. Especially on dirt it seems - much better “gliding” over small bumps while maintaining traction.
Seems to enable lower spring rates vs. running bump at. 67rebound, which enhances traction out of corners.
However, I’m definitely getting some stacking/packing (fully white suspension bars - fully extended) on off road surfaces, and losing traction when I shouldn’t. Seems to vary by car.
Definitely interested in reading other perspectives /testing on this. I re-tuned 3 TVR speeds, 3 Ford gt05s, a Toyota Baja, a Maserati gts and a mosler. Tested the first 7 with about 10 laps each. More testing today hopefully.