How hard is it to find a good mechanic??
in [Aussie Drivers]
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From: Crash Lander on 25 May 2010 17:38 Clocky wrote: > Crash Lander wrote: > > Crash Lander wrote: > > > > > I'm not paying more than the difference between the price to > > > machine them, and new ones. > > > > Well, just got back from Kmart, and the car now has a brand new set > > of DBA rotors on the front. He re-did the wheel alignment, and he > > said they serviced the callipers in case they were having an effect > > on the shaking, which apparently they were not. > > When I called to check it was ready, he said he'd chat to me about a > > price we were both happy with when I got there. So, I arrived and > > let him offer me a figure, which, to my pleasant surprise, was > > exactly what I was willing to pay. The difference between machining > > the original rotors, and the price of the new ones. > > So, at the end of the day, i'm now happy, the car is safe, and > > considering the fair outcome, I'd most likely go back to them. (That > > one at least!) > > Crash Lander > > If the shaking returns in a short time, there is probably excessive > wear on the caliper slides which is far from uncommon on the > Foulcans.. That's what he said they serviced. He mentioned something about slides on the callipers. He said they were fine. Crash Lander --
From: John_H on 25 May 2010 18:44 Clocky wrote: > >In theory braking performance should increase with grooves because you are >effectively increasing the surface area of the disc. In theory, the braking performance should be exactly the same, with or without being bedded in, unless heat transfer is an issue (which would be improved by the scoring). Coefficent of friction is a constant (it's not dependent on pressure) and the same force is spread over a greater area when bedded in, or less when not... meaning that the pressure between pad and rotor is changed but the product of the two (pressure x contact area) remains the same. Force applied to the pad multiplied by the coefficient of friction is the braking force applied to the rotor, irrespective of the contact area. -- John H
From: Clocky on 25 May 2010 19:29 John_H wrote: > Clocky wrote: >> >> In theory braking performance should increase with grooves because >> you are effectively increasing the surface area of the disc. > > In theory, the braking performance should be exactly the same, with or > without being bedded in, unless heat transfer is an issue (which would > be improved by the scoring). > Braking performance is reduced if the pads are not bedded into a scored disc as the pads are only in contact with the upper ridges which reduced the effective surface area of cotact between the pad and the disc surface. > Coefficent of friction is a constant (it's not dependent on pressure) > and the same force is spread over a greater area when bedded in, or > less when not... meaning that the pressure between pad and rotor is > changed but the product of the two (pressure x contact area) remains > the same. > > Force applied to the pad multiplied by the coefficient of friction is > the braking force applied to the rotor, irrespective of the contact > area. Sure, the force may be the same but the amount of friction is reduced by having less contact between the disc and the pad which results in poorer brake performance, until the pads are bedded in that is.
From: jonz on 25 May 2010 19:56 On 5/26/2010 9:29 AM, Clocky wrote: > John_H wrote: >> Clocky wrote: >>> >>> In theory braking performance should increase with grooves because >>> you are effectively increasing the surface area of the disc. >> >> In theory, the braking performance should be exactly the same, with or >> without being bedded in, unless heat transfer is an issue (which would >> be improved by the scoring). >> > > Braking performance is reduced if the pads are not bedded into a scored disc > as the pads are only in contact with the upper ridges which reduced the > effective surface area of cotact between the pad and the disc surface. > >> Coefficent of friction is a constant (it's not dependent on pressure) >> and the same force is spread over a greater area when bedded in, or >> less when not... meaning that the pressure between pad and rotor is >> changed but the product of the two (pressure x contact area) remains >> the same. >> >> Force applied to the pad multiplied by the coefficient of friction is >> the braking force applied to the rotor, irrespective of the contact >> area. > > Sure, the force may be the same but the amount of friction is reduced by > having less contact between the disc and the pad which results in poorer > brake performance, until the pads are bedded in that is. ~~~~~~~~~~~~~~~~~~ too true....but with *badly* grooved rotors this bedding process could take a looong time, leaving vehicle with reduced braking efficiency over the period......could make a difference in an emergency situation. > > -- jonz "Usenet is like a herd of performing elephants with diarrhea - massive, difficult to redirect, awe-inspiring, entertaining, and a source of mind - boggling amounts of excrement when you least expect it." - Gene Spafford,1992
From: Feral on 25 May 2010 20:12
jonz wrote: > ......could make a difference in an emergency situation. Nah. They ALL know better. They're specialist drivers. -- Take Care. ~~ Feral Al ( @..@) (\- :-P -/) ((.>__oo__<.)) ^^^ % ^^^ |