Logitech G29 & G920 AXC sim brake mod review

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.

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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.


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$20 3DRap for a 3D printed buffer


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$24 Nixim for a dual rated compression spring and buffer


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$30 GTEYE for a dual rated compression spring

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$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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I have this mod and pc2 that is my main goto Sim. I've had a headache with mod for 2 weeks now and think I've finally solved problem... Basically in the calibration on pc2 I press my brake in as far as I feel comfy with to achieve 100% braking but that value is only 40% of the calibration bar I do this because for me to press the pedal in all the way to achieve full travel stroke is near impossible and feels way too hard and unrealistic to a real brake system. I can't imaging Lewis Hamilton having to use his wheel to anchor onto to obtain enough leg power to achieve full brake pressure... Anyhow for weeks I've been having a issue where brake has been flickering on for milliseconds ranging from 10%-70% of braking all by itself... I've pulled my hair out trying to work out why it's doing this hell I even bought a new g29 as thought my 3 year old one was on its way out... Anyhow I confirmed the problem was this by in game calibration I pressed pedal as hard as I could to make sure brake calibration bar hit 100% then I tested it and problem of self braking for milliseconds at a time had gone away.. I also put some weighing scales under my pedals to get a rough estimate on how many kg it took for my unit to achieve full travel and my reading were 35kg of force. I've seen in another post on topic of spring load too high to comfy achieve 100% braking and he also had similar results in fact he reported 40kg of force to achieve 100% travel of mod... I don't know if its just a fault with a small percentage of units but I've read some people are saying it's great feel and some saying way too hard a feel.. I'm guess Rob the manufacturer does test every one he makes to see if spring and I turn the final unit falls within spec of 20kg full travel specification and if this is the case I'm hoping it just some units have slipped through net where its almost double the amount of kg needed to obtain full travel. Anyway I hope this Long detailed post comes in useful for anyone who is experiencing similar issues..
Hi, I've just seen this post. We recently had a few people who contacted us with flickering brakes and it turned out to be a problem with the G-Hub software and not hardware related. Could you contact us via drive@axc-sim.com and we'll do our best to assist you. Thanks
Rob.
 
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