Logitech G29 & G920 AXC sim brake mod review

cteters

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As a disclaimer, I received this product at no charge for my honest and unimpeded review.

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Description

TrueBrake is manufactured by AXC-Sim, with what appears to be the company’s first attempt at entering the sim racing market, where prior to this, they manufactured drone equipment. This piece of hardware replaces the stock brake system for the Logitech G29, G920 and is also likely compatible with the G25 and G27.

It has a linear motion potentiometer used in conjunction with a spring and piston that requires 20kg of force to move 3mm. All the components are housed in a very strong cylinder made from billet aluminum manufactured by a CNC machine to fit inside the pedal assembly. The stock travel-based system is replaced by measuring an applied amount of force to the brake, to better mimic actual braking systems found on a vehicle.

This unit is currently being sold for $65 and ships from England. Bulk orders are also an option, so it is possible that dealers might one day keep it in stock as well.


(Can't seem to get this animated gif to work here yet)

The hardware

It seems they found a way to make a 20kg rated button load cell work, as opposed to Ricmotech’s 45kg version and passed those savings on to the consumer. It is described as “a halfway house between the stock setup and a solid state load sensor.”

The product is an electro-mechanical load cell that attempts to simulate the feel of a hydraulic braking system. The brake pedal engages with a spring-loaded piston, while movement is detected by an encapsulated potentiometer. Applied brake pedal force is considerably increased and is directly proportional to the braking applied in a simulation.

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The two custom manufactured polyurethane buffers are interchangeable and providing for a difference of 3mm before pedal engagement between the two.

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The provided compression spring

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Top view of the cylinder housing


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Side by side comparison of the hardware

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The whole unit can be installed with very little effort, requiring no permanent modifications to the original hardware and can just as easily be returned to factory condition.

Initial impression

After installing the hardware, I first ran up DIView to have a look at the sort of feedback it provides to the system. It displayed 255 steps of travel, the same amount of resolution for both the stock potentiometer and even the Ricmotech loadcell for that matter, so I’m not sure if that is a Logitech firmware thing, or just coincidental to all three meters.

Also, speaking of firmware, I’ve heard that it is believed Logitech’s firmware for the G29 will spike with an aggressive curve to the potentiometer toward the end to help mimic load-cell like characteristics, but I witnessed no interference when watching the readings. There were in fact 255 steps in total and each engaged linearly as I slowly increased pressure to the brake.

The brake now feels much more natural and no longer feels spongy at any point and does not behave as if it enters different stages of pressure. It is all one linear flow of pressure that stays consistent to all 255 points that it is capable of detecting. That is approximately 0.39% of total movement between each step of pressure. More than what we could ever possibly sense on our own. This makes for a very natural feeling progression and removes much of the guess work on the track.

On the track

So far, I’ve only had a couple days with the product and so I will need to expand my thoughts on how it has changed my experience as I have more time with it. My experience so far has been a positive one. It eliminates the two-stage feeling that the stock brakes have from the dampening buffer. It has a much more natural and linear range of motion; requiring a greater amount of applied force to such a degree that I can quickly determine a few ranges in a pinch. I now feel as though I have more control over applying more precise amounts of submaximal force.

When I used the older hardware prior to this, I relied on feeling from the transitioning between the different stages of pressure as my cue for applied pressure, so I will be interested in seeing how that feels once I try it again in the stock configuration some time, down the road.

I have a lot more experience with the smaller buffer cap so far and can't yet notice a difference between the amount of pressure needed to engaged between the two. The documentation advertises that they differ in the amount of pedal travel before buffer engagement, so that might only translate to sensitivity, rather than resistance.



$20 3DRap for a 3D printed buffer



$24 Nixim for a dual rated compression spring and buffer



$30 GTEYE for a dual rated compression spring


$130 Ricmotech for a 45kg load cell, spring, buffer and basic PCB amplifier

Pros
  • Creates a linear range of pressure to the braking system that can be mapped more accurately.
  • High quality manufacturing.
  • Reasonably priced.

Cons
  • Although a bargain at the price, one unit will not upgrade your throttle and clutch pedals and so it might not be the upgrade preferable for those on the market for a full pedal system upgrade.

Overall

Most would agree, one of the first things worth upgrading in a simrig is the braking system. The stock combination of a rubber dampener, spring and potentiometer forces drivers to focus more on distance in travel, rather than applied pressure on the brake pedal. AXC-sim, along with a few other mentioned companies provide a solution to this known issue at different ranges of price and quality.

I find TrueBrake to be very reasonable priced and a solid solution from the stock design. This won’t for instance transform a G29 into a PT2 pedal set, but it will provide for that much sought-after edge that racers so much desire in their hardware, without breaking the bank. We all would like to transition into much higher-grade everything for our rigs, but honestly that is an unreasonable consideration for most of us, where this, an alternative from going broke, while still having a slight bit of edge.

I'll try to keep this a live document for a while with updates and field any questions I can while there is still not a lot of information available for this new product.

Cheers!
 
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smasha

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Mar 1, 2010
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Just wondering if it works well with the Leo Bodner cable but I suppose you might not own one,nice bit of kit I must say at a great price.
 

cteters

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Just wondering if it works well with the Leo Bodner cable but I suppose you might not own one,nice bit of kit I must say at a great price.
The USB adapter to make the pedals standalone? Yeah, there is no reason that it should not. The mod replaces the existing poteteometer and installs in-line with the existing electronics, so it functions as a component of Logitech itself.
 

GeekyDeaks

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Dec 26, 2019
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Have to say this is a very keenly priced piece of kit and looks like a lot of effort has gone into the design. I have been DIYing my own load cell mod and the work involved is not insignificant, so I would recommend anyone considering a DIY mod primarily for cost to take a close look at this first.

I am curious if they allow any adjustment of the deadzones? I know you mentioned that the mod still reports the whole 8bit / 255 steps, but that is just the G29 resolution. On my model, I found it is only sampling between approximately 3.1v through to 1.9v, so it causes unwanted deadzones if you tried to use the whole voltage range. Anyone who has tried removing the rubber block will have noticed this as the last 10-15mm of travel this makes available does not have any effect. I suspect the mod is compensating for this quirk.
 

cteters

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After doing research on how much it would cost to build a Ricmotech style load cell, I also found this to be a bargain. The 45kg load cell used in Ricmotech’s costs between $45 and $67 dollars, while this one uses a 20kg and can cost less as an entire assembly. No guess work either. Just plug and play.

There is an adjustment available for the deadzone by selecting between one of the two polyurethane buffers. It changes the adjustment in gap between the pedals and piston for a difference of 3mm. I'm currently using the larger of the two and haven't noticed much of a difference to be honest, or at least upon my initial impression.

I didn’t think of sticking a multimeter to it but did run the thing up in DIView and found that each one of the steps engaged linearly. There is still a deadzone present before the pedal is fully bottomed out though. I don’t have the means to measure the distance of travel, but it requires a great amount of force to get to that point. More than I’m comfortable applying to it at a normal angle anyway.
 
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GeekyDeaks

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Dec 26, 2019
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First up, thank you for taking the time (or paying someone to take the time!) to show the inner details of your mod. That is very helpful in understanding how it works.

I am going to question the claim that you are now measuring load and not the position of the pedal though. I appreciate that cteters felt the mod was an improvement, but I cannot see how the linear pot is going to do anything other than measure displacement of the piston. I also realise that a true load cell 'technically' measures displacement due to the deformation of the material that the cell is comprised of, but the displacement is minute in comparison.

Still impressed with the engineering though. I can see how you have properly designed a true two stage feel via the two springs and the buffer instead of the half baked rubber block approach logitech came up with. That aluminium must look super nice if you have taken your pedals out of the original case too.
 
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Panicpete

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Nov 18, 2017
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Well they are somehow measuring the deformation of the main spring inside the spring housing. This is similar to how many bathroom and kitchen scales worked before cheap ICs became available, which made digital scales a lot cheaper. Applying a load to a spring of known spring rate and measure/display the displacement.

The big difference to the stock setup is, that the don't measure the displacement of the pedal itself, which is basically independent form the force applied to the pedal (the pedal displacement for a given force is determined by the spring setup). So I can see this as a big improvement compared to the stock setup and the known spring/buffer upgrades relying on the stock potis. You probably won't actually feel any difference to a "true" load cell. And you do actually want some displacement in the pedal for varying brake pressure because that's how it feels like in a real car. That's why you still have a spring/buffer in a good load cell pedal.

There are two big advantages i see in normal load cell setups:
  • You can easily adjust the sensitivity of the pedal when you use a trimmer poti in your amplifier circuit. With the setup shown here you have to adjust it on the software side (using deadzones and thereby losing some resolution) or replace the main spring. On the other hand, you may also want to replace the spring/buffer in a load cell setup when you change the sensitivity.
  • There are no sliding contacts which can create false readings when they are worn and/or dirty. Most stock Logitech pedals have a spiking throttle and/or brake pedal sooner or later, which requires you to take them apart and clean or replace the potis. This is highly dependent on the used poti however, and high quality parts can make a huge difference in durability.
 
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GeekyDeaks

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Dec 26, 2019
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Good points - I had neglected to consider that the pedal is no longer connected to the pot directly which makes a huge difference. That was a bit daft of me :)
 
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AeroxGreen

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Jan 6, 2020
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Good points - I had neglected to consider that the pedal is no longer connected to the pot directly which makes a huge difference. That was a bit daft of me :)
:thumbsup:
Was just about to reply but then realised Panicpete already had! Thankyou Panicpete!

I've been having some real trouble getting the principle of TrueBrake across to people but I think it's getting there bit by bit...


Cheers
Rob
 

AeroxGreen

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Jan 6, 2020
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The TrueBrake potentiometer has 5+ times the life rating of the stock Logitech pot. Its also a sealed unit so no dust is going to get in there to mess things up. Should you manage to wear it out within the warranty period we'll arrange repair or replacement. We also have spare parts and a repair service.
 
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Sep 25, 2019
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I've been having some real trouble getting the principle of TrueBrake across to people but I think it's getting there bit by bit..
I think that is showing a lot in people's comments on Reddit with confusion about it being a load cell or not and the benefits of switching to a system like this.

I've just placed an order so look forward to giving it a try and aim to report my findings.
 
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Medilloni

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The TrueBrake potentiometer has 5+ times the life rating of the stock Logitech pot. Its also a sealed unit so no dust is going to get in there to mess things up. Should you manage to wear it out within the warranty period we'll arrange repair or replacement. We also have spare parts and a repair service.
Thanks for all the explanation Rob, looks like an excellent upgrade :thumbsup:

My question for you is, do you sell the original black toothed crown and pinion as a spare part? The reason I ask is that I bought this part from 3Drap (https://www.3drap.it/product/potentiometer-replacement-kit-logitech-pedals/ pic below) due to the original wearng out, and whilst they say you need to re-calibrate your pedal, it still doesn't have the range to work in the ACC settings (it's OK in AC). If you do then I'd consider your kit to upgrade my knackered G920 pedals.

<thinks> if your kit is replacing the original potentiometer, would this even matter - apologies for the numpty question!
potentiometer_kit_logitech_pedals_3drap_22.jpg
 
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GeekyDeaks

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Dec 26, 2019
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You are correct in your last sentence Medilloni. The TrueBrake mod replaces the Logitech pot in the circuit, so the toothed parts are no longer required as they will be driving an unconnected pot (and a tiny spring). This relates back to the mistake I originally made in my evaluation of the mod. I forgot to consider that the TrueBrake pot was no longer directly driven by the pedal, but by the rate of compression of the spring inside the mod. (Apologies Rob!)
 

AeroxGreen

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Jan 6, 2020
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My question for you is, do you sell the original black toothed crown and pinion as a spare part?
No but I have been considering designing a repair kit.
<thinks> if your kit is replacing the original potentiometer, would this even matter - apologies for the numpty question!
As GeekyDeeks just mentioned, if you install TrueBrake then you don't need the old potentiometer and gears. On my own set of pedals I removed the logitech pot and gears to keep as spares for the accelerator and clutch.
 
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Sep 25, 2019
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Received my truebrake yesterday and got it installed, I'm really impressed with it.

The smaller rubber stopper has an ideal amount of travel before it stiffens up and the feel of pressure from there is perfect.

I'd gotten pretty used to my stock g29 brake but after a few laps of Laguna seca I felt like I was modulating my braking more, being able to take it closer to the locking up point more reliably and with better trail braking control than before. None of the 2 stage braking the stock unit gave.

The lack of travel in the brake means my heel toe throttle blipping was completely off but I'll get used to that in no time.

First impressions are very good, I think it does exactly what it says it will and hits that middle ground perfectly, it's miles above a simple spring mod and requires an ideal amount of pressure for those of use using playseats or solid rigs that can't handle braking forces over 30kg.

I've got lots of time over the weekend to give it a go and see how much I can improve lap times and if there are any negatives but so far I can't see any.
 
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ZXCS

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Feb 1, 2020
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I received and installed my true brake a while ago, I have tried it playing F1 2019 on Xbox, I am having a hard time to get the right settings, it’s very hard to reach 100% brake, don’t know why, maybe someone have any suggestions?
 

cteters

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I received and installed my true brake a while ago, I have tried it playing F1 2019 on Xbox, I am having a hard time to get the right settings, it’s very hard to reach 100% brake, don’t know why, maybe someone have any suggestions?
There is a very short band of motion at the end, just before it bottoms out that doesn't actually register. That deadzone requires an uncomfortable amount of pressure though, so you likely are reaching 100% brake. I can't tell you how I would go about testing that on the console however? I would check to see if the settings menu displays what is actually being registered, somewhere in the controller config section.