Mechanical vs Hydraulic Brakes

[snowjob]

I am knee deep in our 2019 Build-Off kart and we have finally gotten our first test drive.

Build Off Thread

Our kart came with mechanical calipers and I spent quite a bit of time fabricating bracketry to make them fit our new setup. They seem identical to those you can find on eBay for ~$10

eBay Caliper

The stopping power on our first test drive was horrible. It could be the worn pads, thrashed calipers, hand lever, adjustment or even the rotor mounts, but I am worried that mechanical calipers are near worthless compared to even the cheapest hydraulic system.

I am considering this kit, but would likely just mount the small discs/calipers on the rear for our current setup:

eBay Hydraulic Brakes

Soooooo, in my typical long-winded fashion, who has experience with mechanical vs hydraulic brakes and what is your opinion? I would really like at a minimum the ability to lock up the wheels and stop on a dime (don't want much, I know ;-))

 

[420Racer]

I will always say hydraulic. You will easily lock up the rear tires on that with little effort on the pedal. Are you planning to use the fronts and emergency brake in the future? If not you may be able to save some money and only buy what you need for the rear.

 

[mckutzy]

Off hand I think I can see a bit of a problem.... Most of my experience is from the top liner The Airheart mechanical caliper....but basically the same concept..

On your kart, It looks like the brakes are hard mounted and none float.....
Typically in these systems one or both need to float to help align the clamping forces, or it just puts force on one side of the caliper/disc....

Most of the china brand calipers I have seen are lacking some how, the cam angles and wear surfaces seem soft. the pads also look off, as in they seem like they arent proper brake material...
But for the most part....From what I have seen, the biggest part of the lack in stopping power is from the compatibility of the materials of the pads and disc....

The stock pads of the one above(airheart), need a cast iron or carbon steel rotor to be used with there pads. In your thread showing the caliper and disc, that also might be the problem. Albeit they were sent together, they themselves might not totally know...

On my bikes, the discs are sanded to a rough texture pattern as to gain a biting surface. Also the pads are sanded to the face of the disc as to help bed-in, aswell as keeping the brake pads and surfaces free from all oil and grease of the fingers and alike..Brakleen or the like...

On my bigger bike I built, the original disc I chose to use was from a motorcycle....
The above caliper Airheart/Tolomatic mechanical brake caliper, the pads weren't compatible with the stainless steel disc that it was made of.... I had to switch to a large sprocket of carbon steel... Much better braking power now....

 

[snowjob]

Excellent input, thank you both.

For now, I plan to only use the small/rear discs as we are limited on size due to the tiny wheels and enclosed axle. This may change in the future, but adding front brakes seems like a lot of additional work. It would be great to buy only the two calipers and master cylinder needed, but I have not seen that type of combination cheaper than the kit shown above.

The current rotors do flex quite a bit as they are very thin. Additionally, the calipers have a spring and adjustment screw mounted to the slider, so they can move back and forth as the rotor does. There is some room for improvement on both of these points.

Your comment regarding rotor and pad material is also possibly the issue. The rotors are very shiny, so I would not be surprised if they are stainless steel. Combined with a poor pad compound and I would get almost no stopping power.

The first thing I need to address is that one caliper requires a much longer pull before activating than the other. I attempted to improve this by sliding the cable further up on that caliper, but it is still not great. The pads may be worn, the rotor may not be as well centered or the caliper may be worn, I am just not sure.

I will spend at least a few hours optimizing what I have before throwing money at it. It seems reasonable that I should be able to lock up the wheels with these components if they are working correctly.

 

[mckutzy]

Id sand(SAND NOT GRIND), with a sanding pad light pressure, on the disc's contact pathway. Even and enough to have a good matte finish... dont hog into it as this will put a weakened spot in the disc.

Is this a live axle or dead on the drive axle??

 

[420Racer]

If you are going hydraulic you will need two hubs two work with the rotors your buying. I don't know of any that will directly bolt up to those but I could be wrong. If I were you ( I'm guessing you have a 1" axle ) I would get 1 6 inch rotor and hub to match, and use an atv caliper and master cylinder. Bmi has hubs and discs and you can get master cylinders, calipers and a brake line off eBay for pretty cheap. It would be around 120 bucks maybe a little less for everything I just listed. Mckutzy did post a lot of good info on the mechanical brakes. I haven't used those in quite a while but on a kart that light they should have enough stopping power. I had mechanical brakes on my old Manco Deuce's and they did work but just had to really get on the brake pedal. That was a 6-700 lb machine. So either way you go if you need help finding the right parts feel free to pm me and I can help you get the right stuff. The calipers and master cylinders I use are fairly easy to mount up

 

[snowjob]

I think you would call this a live-axle setup. I have a 1" keyed axle that runs through the rear tube on what is now a solidly mounted swingarm. The bearings have carriers welded onto the ends of the axle tube. The hubs, sprocket, rotors and wheels are all bolted together and then keyed to the axle and fastened with a nut. My son insisted that both rear wheels must drive the kart and I spent a ton of hours custom fabricating to make the existing parts work (especially with an enclosed axle in a tube).

I presume we only need one brake for the axle assembly, but since the original kart was one-wheel drive and had dual discs, we chose to keep both of them. We are pretty space limited since the rotors, calipers and even sprocket must be mounted outside of the axle tube width right next to the wheels.

I'll try deglazing the rotors and seeing if I can better adjust the calipers next time I am working on it.

 

[snowjob]

I chose to go with new calipers. I knew they were going to be a big improvement as they applied force evenly compared to the old ones and I could get the line very taught without applying any braking force, so even mild lever pressure applies braking. Out of the box, they are easily a 100% improvement and I expect they will get slightly better as they bed in. We are now at the limit of the hand brake lever, but the kart slows well enough to be safe. If you really try, you can apply just enough force to lock them up....so it may work great for a younger/lighter driver