I recently moved to the US, but since my kart is still in shipment process from Europe, I rented a race kart from a track local. It’s a Birel S15 2022 chassis with a Rotax Max engine. The kart drives very well, but there is one small problem: the brakes have a very weird feeling. There is minimal travel in the brake pedal and it feels on/off, with no in between feel. I cannot brake at the normal braking points (or trail brake entirely, for that matter) on the track or the brakes lock up. I bled the brakes, checked for wear on the pads and rotor, everything seems fine so it’s not a mechanical issue.
I drove another kart on the track, a 2023 LN chassis (with the same engine). The brakes felt fine, I was able to brake comfortably at the normal braking points and even later and the kart felt much more comfortable.
Is there any adjustment I can make to fix this issue? I’ll be renting the kart again next week and I want to put in some good laps.
Some brakes are more “light swich”, but you could try moving the actuator rod to a different (lower on master) actuator hole, or to a lower hole on brake pedal. The human body is wired to respond to pressure impulse, not distance moved, so you may find that a short pedal but trained pressure sensitivity on foot is more consistent in the long term… I like a super-firm pedal with little movement. This can be tricky on a bumpy track, however.
ADDENDUM: if the master cylinder isn’t the original one, it could be pushing more fluid than the original…would be an odd case, but it’s possible.
I usually prefer a firm pedal as well, but with a bit more travel so I can brake more progressively. With this pedal if I apply the pressure I usually apply on my own kart for braking into a slow hairpin, I’ll spin out.
It’s probably a matter of getting used to it, at the end of the day I was “only” 1.5s of what is considered a good laptime with two 10-15min sessions. Hopefully I’ll find more time in the next session.
Brakes aren’t like a throttle and shouldn’t be modulated by travel. Brakes are modulated by pressure. There should be a tiny bit of travel as the pads move towards the rotor and then everything should have very little movement. The rest is pressure modulation
Of course it won’t have as much travel as the throttle, but compared to the OTK brakes it has almost half the travel and it makes a huge difference. I might try moving the cable to the lowest hole on the pedal to increase the travel slightly and see if it makes a difference in feel.
A different compound of pad can help too. A harder pad will allow more pressure before lock-up where a softer pad tends to grab more readily.
I find Birel and Parolin brakes to be really sensitive and difficult for a few laps, but eventually you build the muscle memory and you naturally adapt. OTK and KR systems have a stiffer pedal and allow more modulation before lock-up in my experience.
Try moving the rod down on the master cylinder actuation arm. That was always my default. I found the default Compart/Birel took too little force and was hard to modulate.
You are probably on a larger disc as well from what you are use to on OTK. So the Birel can apply more torque meaning more stopping power.
Otherwise if you want more throw/movement you need to move up on the brake pedal.
Lastly you can give yourself a bit of a dead spot and more travel by checking the rod between the pedal and master cylinder. I hate any sort of dead spot so I would have the rod slightly too short where I would need to actuate the master cylinder a very small amount to get the bolt through it. You’d want to do the opposite and lengthen the rod as much as you can.
