KiwiTR6 Posted September 12, 2018 Report Share Posted September 12, 2018 Waldi, I understand your point, but if the driver cannot press hard enough for "adequate" braking, that is not a fault of thre brake system. I agree, for anyo who is in that position, a servo can be useful, but it cannot make braking better.' And there is a limit to the servo effect as show below, Servo brake effect.jpg John John, your graph doesn't appear to support your argument With 40kg pedal pressure, no servo produces approx 48 Bar of hydraulic pressure vs 80 Bar with the servo! As clamping force = pressure x area (piston, not pad) then clearly having a servo significantly increases the braking effect for any given amount of foot pressure - surely? Gavin Quote Link to post Share on other sites
TriumphV8 Posted September 12, 2018 Report Share Posted September 12, 2018 (edited) There was a simple reason for me to use the double diaphragm booster: The luvly laidi in my household claims the car is not running well because the brakes do not work properly and she feels unsafe. The reason is simple: Modern cars have ABS what invites the engineers to increase brake boosters size. So they require less forces than earlier cars because overbreaking is no longer a topic. The ABS simply will start to work and the car keeps stable on the road. So a swap between two cars becomes a pain because it is so different. For me it was the other way round. driving wifes Skoda Yeti always creates a happy moment when braking first time. I simply forget the difference and the car is breaking very hard- All I can say is that besides very soon the skilled driver adapts to the required braking forces its a very nice add on to drive the TR6 with reduced pedal forces. Many years ago we tried to reduce pedal forces on a race car by swapping to a small master cylinder. The result was really bad because the pedal travel increased what overall gave a millisecond longer time for travel to the braking point and a weak pedal with bad feeling under brakes. So all swaps to big calipers must be seen with great care. If the braking requires less force after that two things will happen: The pedal travel gets longer and weaker and the rear brakes get less braking force. The overall braking ability gets worse because the rear does not add its work as it could. Addionally our TR is set very save/conservative and the rear brakes very poor what can be improved with the bigger Morgan wheel cylinders. The reason is that we can not change brake balance and it must be set for the worst situation to avoid overbreaking of rear where the rear will become loose and try to overtake the front. That is a very unsafe situation but the engineers did a little bit too much from my view. So adding the four pots is opposite what I would expect and the driver thinks to have better brakes but in danger the total way to stop the car will increase. Edited September 12, 2018 by TriumphV8 Quote Link to post Share on other sites
Tim D. Posted September 12, 2018 Report Share Posted September 12, 2018 Sage words from Andreas. Worth pointing out that the main reason ABS is fitted to modern cars it to allow steering under extreme braking. If you lock your brakes you also loose steering which can be an issue if you want to avoid hitting the thing you braked for.. I discovered this on the autoroute on the way to Spa. Car in front braked heavily but had no brake lights... by the time I noticed it was almost too late.. braked hard and locked the brakes of the TR.. luckily something in my head said "cadence braking" and I released the brake, regained steering and shoved the car down the hard shoulder.. with ABS I could have just steered the car with my foot full on the pedal still.. Have to say, takes balls to come off the brake in that situation! Cheers Tim Quote Link to post Share on other sites
john.r.davies Posted September 12, 2018 Report Share Posted September 12, 2018 John, your graph doesn't appear to support your argument With 40kg pedal pressure, no servo produces approx 48 Bar of hydraulic pressure vs 80 Bar with the servo! As clamping force = pressure x area (piston, not pad) then clearly having a servo significantly increases the braking effect for any given amount of foot pressure - surely? Gavin Gavin, The servo just amplifies the foot pressure, up to a limit. That brake system pressure is not the end of the story, and a servo will not 'cure' a poorly functioning system, or make the braking "better". Triumph brakes are perfectly adequate, if properly serviced, for road use. If someone who does not suffer from arthritis or another disability that limits their foot pressure feels that their brakes are not adeqaute, then a servo should be their very last resort, after sorting all the other ills that brakes are heir to. JOhn Quote Link to post Share on other sites
KiwiTR6 Posted September 12, 2018 Report Share Posted September 12, 2018 (edited) Gavin, The servo just amplifies the foot pressure, up to a limit. That brake system pressure is not the end of the story, and a servo will not 'cure' a poorly functioning system, or make the braking "better". Triumph brakes are perfectly adequate, if properly serviced, for road use. If someone who does not suffer from arthritis or another disability that limits their foot pressure feels that their brakes are not adeqaute, then a servo should be their very last resort, after sorting all the other ills that brakes are heir to. JOhn John, Yes the brakes need to be in good working condition in the first instance, no question. However, in this day and age when one and his beloved others are jumping between vehicles it's desirable that the response to pressure on the brake pedal is vaguely similar rather than miles apart (ABS aside). I'll stick with the booster on my road car and leave the un-boosted brakes for my race car Cheers Gavin Edited September 12, 2018 by KiwiTR6 Quote Link to post Share on other sites
Tim D. Posted September 12, 2018 Report Share Posted September 12, 2018 I have a midget without a booster and I would agree with you Gavin. The first few applicaitons of the brake can be scary as you do need to use leg power to get decent retardation! Quote Link to post Share on other sites
Waldi Posted September 12, 2018 Report Share Posted September 12, 2018 I had a 69 MGB-GT (and yes I love them, and not hiding now, and no, no shawls or sheepcoats for me????) it was my daily driver, had no servo, and it was not needed then. In fact the majority of my classics did not have one, and I never missed it. But one gets older, and the difference in brake-efficiency with modern cars has increased over the decades too. The MGB was only 12 years old when I bought it so relatively modern technology then. Waldi Quote Link to post Share on other sites
mike3739 Posted September 12, 2018 Report Share Posted September 12, 2018 I have thinking about dropping this comment in as the thread progressed. On my 1971 TR6 I fitted Wilwood four pot calipers with larger vented discs around ten years ago before going down to the South of France. The difference was & still is amazing more progressive braking with no fade. A few years later I went to Wales with a fellow TR6 owner I was the lead car that morning & I had to brake quite sharpish to avoid hitting a pheasant my friend unaware why I had braked on a clear road, just managed to stop with all four tyres smoking!! Shortly after that he also fitted 4 pot calipers. I will confess to also owning an MG TF 2005 which has disc brakes all round with AP Racing 4 pot calipers on the front with larger vented discs, on the rear the calipers are standard. The brakes are servo assisted with ABS as standard for a mid-engine car which is fairly light in comparison to the TR the stopping power is superb. Just my thoughts on the subject. Cheers Mike Quote Link to post Share on other sites
nigel62 Posted September 14, 2018 Report Share Posted September 14, 2018 Burton now do reproduction princess calipers. Quote Link to post Share on other sites
john.r.davies Posted September 14, 2018 Report Share Posted September 14, 2018 As Homer pointed out on page 1! and they come with spacers fitted ready for Capri 2.8 vented discs, just right! http://www.burtonpower.com/new-4-pot-princess-vented-calipers-pair-ford-escort-rs-capri-cal4potv.html The discs may need some work to fit Triumph hubs. John Quote Link to post Share on other sites
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