Ven04 -> ven05 upgrade rear brake

Im looking to upgrade my rear brakes on my crg road rebel. I want to get the ven05 and found a rear brake package for pretty cheap.

Would they directly bolt on?

How much of a difference would they make compared to the ven04. The ven04 i have are very thin.

You’ll have to compare the caliper mounting patterns to see if they’ll plug in. VEN05 is among the best kart brakes I’ve ever sampled. Subsequent iterations going forward since have essentially been an evolution of the VEN05 design. The ventilated disc solved the heat problems the VEN04 could sometimes encounter.

Yeh I’ve heard they are among the best brakes out there. My only problem is i dont have the caliber in hand or have access to one.

Wanted to see if anyone has one they could maybe take some measurements?

Curious why you feel you need ventilated brakes? Are they getting soft during a run because the rotor is glowing and overheating the pad?

The VEN04 series uses a thin MC style disc, that tended to get hot.

The 05 solved that by going to a ventilated disc.

ETA, found this thread: CRG - Making Ven05 brakes fit a Ven99 chassis

1 Like

I guess this another thing I don’t understand about karts coming from a car racing (mostly crew) experience. For reference, iron rotors start to glow about 930F. That’s just starting to get hot.

This is why I don’t understand the purpose of ventilated rotors on a tiny kart. There is so little mass to stop compared with the surface area. Warm to hot with racing brakes is good (cold is BAD). So long as the pads are in the window, the main differences between them are how aggressive they grab, leaving it somewhat up to driver preference so long as they will last the race distance.

I know CRG sells some different colored pads, but I can’t find anything that provides any information like you would find with pads for any other motor sports showing temperature vs coefficient of friction (Mu), such as this graph for Hawk pads.


Even though my electric kart will be quite heavy, with both front and rear non ventilated rotors I don’t see how I would ever need anything more. I’d say that kart pads are just crazy soft, yet mine hardly wore during an entire season with the 80cc shifter (only rear brake).

Brake loading on starts is one thing not represented in the graph. It’s pretty easy to bake things on a rolling start, definitely been there.

I also think the rhythm of kart driving - particularly the shifter category - works brakes enough to potentially be an issue. There must be a reason the ventilated rotors starting from VEN05 are the de rigueur spec after all this time. I doubt they are cheaper to make than a stamped sheet of spring steel (VEN04).

Karts have a really small hydraulic system so a small amount of expansion of brake fluid can cause the piston push out slightly causing brake drag. Interestingly synthetic brake fluid has higher boiling point, but has higher thermal expansion below boiling. At a track with a long straight away, by the end of session the brake would be dragging slightly. This was before you could find brake ducting for karts. I made one from some car intake runner. The brake stayed cool and did not drag. Around the same time Birel came out with a caliper that was cantilevered. The pistons were not directly behind the piston and that resolved it as well.

Yeh i saw that but i couldnt figure out the ven99 chassis…older?newer? Same mounting points as mine. I might just get them and make them fit lol

My hunch is they might be compatible, maybe with an adapter bracket. I’d check with a CRG vendor, or even contact CRG directly. I had really a good experience with Parolin. Response time took a while, but I got the answers I needed by going to the source.

Would there be a big difference in performance? I feel like the ven04 are soft and dont have a great bite. Stops quickly but i feel like it can be quicker.

I honestly found VEN04 to be very good. Almost too good if you’re in slick conditions. If they feel soft, something in the system isn’t quite right.

I’d agree that in wet conditions the VEN04 is a little hard to modulate. I never had any issues with them getting soft, although I had a dual master setup.

Are you sure it is bled well?

Definitely should check for air in the system.

Personally, I really like the modulation feel of VEN05. The ventilated discs are the main improvement from the 04 to mitigate heat.

They have a good grab but the pedal seems quite soft compared to others ive compared it to. Honestly i have bled the system in over a year so maybe it’s time.

I would definitely try that then.

A trick I’ve used to make sure all the fluid is replaced is to alternate natural and colored fluids. After super blue fluid was banned I made my own colored fluid with a tiny amount of Methylene Blue added.

That seems like a very long time for kart brakes. IIRC I was doing it every 2-3 meets. I do like a very firm brake, though.

Well i dont get out too often. I dont race either. I probably have like 4-5 actual driving hours this whole year. We spend half a day at the track but do like 3-10-15min sessions each time.

You could always take dimensions and have a metal fabricator make you a custom bracket. I did this for my mcp system I bought for my Birel build. It worked out nicely!