Anti-Lock Brake Systems

[Adventurewagen]

Anybody add ABS to their bus? My buddy added it to both front and rear, but I think he later removed the rear and left only the front. I might try and get his spare unit for my bus but I was wondering if anyone has added it to their bus too?

[vwlover77]

There are aftermarket systems for this? How do the wheel speed sensors work? How do the hydraulics have to be modified? What master cylinder is used??

[Amskeptic]

Anybody add ABS to their bus? My buddy added it to both front and rear, but I think he later removed the rear and left only the front. I might try and get his spare unit for my bus but I was wondering if anyone has added it to their bus too?

If any removal was performed, I hope your buddy actually removed the front and kept the rear.
Colin

[Adventurewagen]

I stopped by my buddies the other day and got to see the one he took off and how it worked. It's a nitrogen actuated mechanical ABS unit that attaches right to the master. When the pressure gets high the unit begins to oscillate which keeps the brake fluid moving so the breaks don't lock.

He did take the fronts off. The rear drums work better with it I guess since drums are more easily locked. The fronts were ok, but gave him too much sensation with it on the fronts. The units at the time were 600 for the pair but he got them off ebay for 10 bucks cause nobody knew what they were. I'll see if I can't find them online but it sounds tempting to try something like that. Probably good to do though with a new master in there.

[Amskeptic]

He did take the fronts off. The rear drums work better with it I guess.

You want the rear of the vehicle to track. If you ever have to make any sort of decision about tires or brakes, you want the rears to have less brakes and more traction than the front. The front is more controllable with the steering wheel. I put the better tires in the rear. And if I had to choose which axle to provide with ABS, it would be the rear.
Colin

[Adventurewagen]

Even in the rears were to lock up would they still track? Its like the brake strips on semis, a little different scenario with a trailer and all, but many of them have the brake strip rolled up in front of the rear set of axles. If they really need them they drop the roll which effectively locks up the rear tires by sliding under the tires and becoming a sled of rubber.

He also created a jig for the front discs that you can mount then drill out perforated holes like later model disks for better cooling which he's done on both front discs. His bus can stop better than any bus I've ever driven.

[Amskeptic]

Even in the rears were to lock up would they still track? Its like the brake strips on semis, a little different scenario with a trailer and all, but many of them have the brake strip rolled up in front of the rear set of axles. If they really need them they drop the roll which effectively locks up the rear tires by sliding under the tires and becoming a sled of rubber.

He also created a jig for the front discs that you can mount then drill out perforated holes like later model disks for better cooling which he's done on both front discs. His bus can stop better than any bus I've ever driven.

You don't want the rears to lock. Once the mass of the vehicle starts coming around with locked rears, your ability to control it is disappearing.
With your example of the semi, the brake strips are working on the front of the load. You really really don't want the load coming around sideways!

There are no ventilated disks in the air-cooled line-up. Are you speaking of ventilated disks like on later model cars? Ventilated use two disks with vanes in the middle, plenty of heat-sink in that design. Drilling single disks on a 75 mph top-speed GVWR 4,961 lbs vehicle for cooling, seems a little boy racer to me, you are cvertainly losing heat sink. My factory stock stopping distance is 123 feet from 60 mph. I'd be interested to know if his braking is better than that.
Colin

[Adventurewagen]

I will have to go test his stopping distance with him

I guess the semi example just wasn't a good one then. I've seen the strips located on their rear set of axles which made me wonder. Either way he's got the anti-lock device on the rears to keep them from locking up. I wish I could find the devices again, but I don't think they took off. Too expensive for what you got with them for a small number of vehicles.

As for the discs he designed and ventilated his stock 71 discs for the hell of it

But as for losing your heat sink by drilling some holes in your disc, you really aren't losing that much material. As a total guess on material removed and considering I don't happen to have rotor in front of me to measure, humor my estimates we can correct them later. Lets say we drill 12 holes, 1cm in diameter on a 1cm thick rotor which comes to 9.42cm3 of material. Assuming the rotor is 25cm in diameter and the ring is maybe 5cm wide you've got 314cm3 of material in just the outer portion. That means you've removed 3% of the material by volume in the rotor which isn't much of your heat sink lost especially considering its low since the center portion is also a heat sink of material.

Obviously to truly test this mod you'd need to measure the brake rotor temps under operating conditions and you'd need to plain test the stopping power. Either way I'm suprised there aren't more "new" rotor style kits available for the buses.