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> Tell us more about this "rolling road" test equipment that measures > braking. What, exactly, is it measuring during braking? > Hi Toby, Take a look at http://www.motuk.co.uk/ to see a garage layout with the rollers visible in the floor, and http://www.boschautoparts.co.uk/teBrak1.asp?c=2&d=3 to see the readout of the roller brake tester. Each wheel on the axle sits cradled by its own pair of rollers, which can be powered independently. The braking force exerted on the rollers by the tyre being braked against the roller motor is registered on its own dial. You can check for binding brakes by starting the rollers and seeing if there's a significant reading on the dial, then gently increase the pedal pressure to show if a piston is sticking, and watch how the needles increase simultaneously to check for brakes pulling one way or the other. As you release the brake pedal, you can see if one is tending to stick (ie if there's pressure remaining in the system). The dials read in kilograms force, and adding the total you can calculate the maximum deceleration from F=Ma. Using force in kgf and mass in kg, you would actually get the result in 'g's. I believe with normal equipment, 0.7 - 0.8 g is considered pretty good (no sticky tyres on mine). I don't worry too much about the actual reading, as long as they are well up the dial and move evenly and together, but I have noticed the Type 3 Variant locks the fronts up around 120/130, and the rears maybe get up to about 200-250 before the tester stops pushing the pedal, since they are performing well enough. I don't think I've ever actually seen the rears lock-up, but I'm busy watching the dials for problems or reassurance. It's lovely when they move up smoothly together. Conversely, the Golf Variant went over 300 on the fronts, and maybe 150 on the rear. In this case, the rears always lock on the machine. Our Polo, VWs water-cooled entry-level car back in the 80s, does something similar, but the figures are more like 200/100 front/rear, as it's quite a light car. Since the test is done in the workshop, there is no way to measure changes due to 'weight transfer'. The effect of that is enormously different depending on the vehicle speed and the braking force exerted (I know a bit of basic Physics, too!). The Golf has an automatic brake balancer that I think works on the deflection of the rear suspension, while the Camper has a ball-bearing pressure-limiting system for the rear to reduce lock-up when the 'van' is lightly loaded. You don't usually need this system on the Type 3 Variant, though the front wheels sometimes lock up rather easily on a slippery road! While the annual MoT test (like the TUV in Germany) is often dreaded, it can show up potentially dangerous problems, and personally I'd rather know about these than pretend they don't exist, even if it does cost about $50. I can't get as good a look at the underneath at home as the tester can get with a ramp and lead lamp. One year he failed it on a small crack in the camper front axle 'cheek', but it was actually horrifically rusted in the ends of the beam, which i found as I cleaned off small spots of surface rust. The corrosion that caused the crack hadn't actually spread sideways at all. Dave. UK VW Type 3 & 4 Club http://www.hallvw.clara.co.uk/ ------ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ List info at http://www.vwtype3.org/list | mailto:gregm@vwtype3.org