Anglefire Posted February 22, 2019 Report Share Posted February 22, 2019 26 minutes ago, JohnD said: Why is it that "As the discs got larger, the effort to press the peddle with enough force and not have too much travel got to the point that a servo was needed to make the driver feel better." A larger disc has a greater lever on the wheel/tyre. Try thought experiment - a disc MUCH larger than the wheel. Yes, it would need a trench to travel in, but you could stop it with your fingers if it were large enough. And pedal travel would be the same, surely? If the master and piston cylinder diameters were the same But educate me, please - it is concievable that I am wrong! Hum. You've got me thinking now. I don't know. I shall take my Spit out for a little drive in the sun and ponder. Wonder if its pad size to disk size? Bigger pad, needs more effort to squeeze the disk. I do know the Discovery 2.7TDI discs are smaller than the V8 discs - the pad size is the same but the braking "Power" is better with the V8 setup. So your thought experiment is not just thought, but practice too. Link to comment Share on other sites More sharing options...
JohnD Posted February 22, 2019 Report Share Posted February 22, 2019 Anglefire, Pad size, counterintuitively, is irrelevant! Frictional force = force squezing the surfaces together x Coeff.friction Squeeze force is in kgs/m^2 (or lbs/in^2 or whatever) Make the pad bigger and leave the hydraulics the same, and the force/unit area FALLS! BUT, you have a larger pad, so multiply it back again - and you get the same number for friction as you started with! A multi-pot caliper is often thpugh of as 'better, beacuse of the bigger pad'. Not so, see above. But a wider, less tall caliper can be mounted further from the hub, so more leverage. The same frictional force will stop the car better. Another reason for tall wheels and narrow tyres, more room for a wider disc. Your Landies must have servos, yes? So 'better' braking is more in the hands, or pencils, of their designers. John Link to comment Share on other sites More sharing options...
Rabbit Posted February 22, 2019 Report Share Posted February 22, 2019 I remember the Citroen braking! Did the same and nearly went through screen. The system on this car was used to pump up the suspension so probably this made the brakes more 'efficient?' Certainly never had problems stopping it. Incidentally I have just replaced the servo on my Spitfire MkIII with a 5 1/2 inch unit which sits on the bulkhead where the old one sat. Don't worry what purists say, it requires less effort and is more like my modern cars for feel etc. The old servo was still working although approximately been onfor 15 years but had just started drinking moderately brake fluid. To finish, it's MY car and I will do what I want to it! Link to comment Share on other sites More sharing options...
Anglefire Posted February 22, 2019 Report Share Posted February 22, 2019 25 minutes ago, JohnD said: Your Landies must have servos, yes? Oh yes! Nearly 3tonnes of vehicle takes a bit of stopping! Especially from high speed or downhill at 45' or more! Multipot is probably "better" due to more even pressure on the pad/disc. Interesting discussion though. Some reading to do at some point! Link to comment Share on other sites More sharing options...
dave.vitesse Posted February 22, 2019 Report Share Posted February 22, 2019 Does Power Steering make the steering any better. Well it can make it worse if it lacks some feel and feedback. But generally it makes driving the car easier, is not the same true for the servo. Dave Link to comment Share on other sites More sharing options...
Anglefire Posted February 22, 2019 Report Share Posted February 22, 2019 Having a servo certainly makes driving easier - whether it is a required can only be determined by the driver - I wouldn't fit one to my Spitfire as I don't find the brakes overly difficult to use - but yoof is on my side possibly - and I'm 6' and overweight - but if I was a little senior and of slighter build I might consider it. Horses for courses and no real right or wrong - I wouldn't have a modern without one - but then they generally weigh twice as much and are designed to have one! Link to comment Share on other sites More sharing options...
JohnD Posted February 22, 2019 Report Share Posted February 22, 2019 Steering is a different Q. If you want to steer easily, without heaving on the wheel when manoevering to park, then a 'slow' steering rack, with lots of turn stop to stop is needed. A 'quick' rack may leave the slight driver struggling. So most moderns will have a quick rack and power steering. It can't make it 'worse' or 'better', unless of course it needs repair! Some cars have electrically assisted steering, that reduces in assistance as you speed up, usually giving none at all above 30mph. Some just have an electric pump on the hydraulic PS, but others have a pure electric servo (!) on the steering column. Some may be good to transplant to other cars, and could go into Triumphs. John Link to comment Share on other sites More sharing options...
dave.vitesse Posted February 22, 2019 Report Share Posted February 22, 2019 Mark, I always thought the Spitfire brakes felt that you didn't need too much foot effort to stop the car. The larger brakes on the GT6/ 2 Litre Vitesse without a servo do need much more push on the pedal. John, As you know a slower rack was fitted to the GT6/Vitesse due to the extra weight of the engine in an effort (no pun) to reduce heaving on the steering wheel. Not too sure it worked, must be the modern tyres! Also If you remember early power steering lacked feel and feedback, plus it also got a reputation for unreliability. Though I hate to think of want it would be like to drive a modern (with big brake and tyres) without both a servo and power steering. Anyway, sports cars with servo's and power steering. What next Automatics! Dave 1 Link to comment Share on other sites More sharing options...
dougbgt6 Posted February 22, 2019 Report Share Posted February 22, 2019 I've bump started my GT6, on my own, admittedly on the flat and 40 years ago. It's a VERY light car and yet Triumph decided to fit a servo as standard. Triumph liked it, I like it. 12 minutes ago, JohnD said: It can't make it 'worse' or 'better', unless of course it needs repair! Better can simply mean I like it. Improved might be a better word. Richard at East Berks has power steering on his Spitfire, width of tyres seemed to be the primary incentive to change! There's an MX5 auto, might well be my next modern. Doug Link to comment Share on other sites More sharing options...
dave.vitesse Posted February 22, 2019 Report Share Posted February 22, 2019 25 minutes ago, dougbgt6 said: I've bump started my GT6, on my own, admittedly on the flat and 40 years ago. It's a VERY light car and yet Triumph decided to fit a servo as standard. Triumph liked it, I like it. Better can simply mean I like it. Improved might be a better word. Richard at East Berks has power steering on his Spitfire, width of tyres seemed to be the primary incentive to change! There's an MX5 auto, might well be my next modern. Doug Doug, Not to sure of the latest MX5 model but the one before had an auto options with gearshift on the steering wheel. Fast change paddles. Dave Link to comment Share on other sites More sharing options...
Anglefire Posted February 22, 2019 Report Share Posted February 22, 2019 My modern is an auto - its not officially a sports car - but will launch from rest to 62mph in under 6 seconds and go onward to 155mph limited - and has paddle shift on the steering wheel - which when in sport makes for a blisteringly quick gear change!. Oh and is a diesel - and it goes around the bends a lot quicker than the Spitfire (Mostly because it has quick power steered steering 😂) 54 minutes ago, dave.vitesse said: without both a servo and power steering. Yes I forgotten I'd no power steering when I was recovered off the mountain 😂 Wasn't too bad once moving! Most modern very quick sports cars have auto boxes - My BMW is not available in manual trim - the engines torque is too great for most available spanish boxes. The petrol 3ltr is though. One reason for auto boxes these days is so that they can keep the engine at peak operating revs - 9 and 10 speed autos are not uncommon. Mine is 8! Trouble is more than 8 and they never seem to be in the right gear! Link to comment Share on other sites More sharing options...
johny Posted February 22, 2019 Report Share Posted February 22, 2019 I like my Triumph cos its different from my modern and as long as its not too unsafe (its definitely not as safe but is within what I find acceptable) Im happy to do without power anything.... 1 Link to comment Share on other sites More sharing options...
dougbgt6 Posted February 22, 2019 Report Share Posted February 22, 2019 Brain power? Sorry, didn't mean it, Pete Lewis made me say it. Doug Link to comment Share on other sites More sharing options...
johny Posted February 22, 2019 Report Share Posted February 22, 2019 Ha hes not wrong when you think about driving a car thats 50 years old with 10 times as many other road users and a spear inches from your heart for a steering column! Link to comment Share on other sites More sharing options...
Pete Lewis Posted February 22, 2019 Report Share Posted February 22, 2019 Dear Doug , Why did i guess its was my fault Would you like B&B for twiddle day , i can sweep the shed ??? Pete Link to comment Share on other sites More sharing options...
Anglefire Posted February 22, 2019 Report Share Posted February 22, 2019 1 hour ago, johny said: I like my Triumph cos its different from my modern and as long as its not too unsafe (its definitely not as safe but is within what I find acceptable) Im happy to do without power anything.... Exactly. I enjoy driving it - though I filled up today and have only done 100 miles since filling up in the summer last year. Must try harder! And it isn't about driving fast or anything like that - its simply roof off and country roads. Link to comment Share on other sites More sharing options...
TomL Posted February 23, 2019 Report Share Posted February 23, 2019 On 22/02/2019 at 16:28, dave.vitesse said: Anyway, sports cars with servo's and power steering. What next Automatics! Automatic transmission... That would never happen on a Vitesse, surely? Link to comment Share on other sites More sharing options...
JohnD Posted February 24, 2019 Report Share Posted February 24, 2019 oooooooooooooh yes it could! https://www.britishpathe.com/video/the-gearless-car-glasgow/query/Triumph Whether you should is another matter..... JOhn Link to comment Share on other sites More sharing options...
Adrian Cooper Posted February 24, 2019 Report Share Posted February 24, 2019 John, have a close look at Tom's avatar picture, I think he has a story to tell! Adrian 2 Link to comment Share on other sites More sharing options...
dougbgt6 Posted February 24, 2019 Report Share Posted February 24, 2019 2 hours ago, JohnD said: Whether you should is another matter A chap in Canada contemplating converting a Spitfire to automatic explains...…. "It's just so hard to drink beer, smoke cigarettes, and shift all at the same time." db Link to comment Share on other sites More sharing options...
johny Posted February 24, 2019 Report Share Posted February 24, 2019 On 22/02/2019 at 22:27, Anglefire said: Exactly. I enjoy driving it - though I filled up today and have only done 100 miles since filling up in the summer last year. Must try harder! And it isn't about driving fast or anything like that - its simply roof off and country roads. Thats disgraceful! I thought you could be stripped of your membership if you do less than a 1000 miles a year😵 1 Link to comment Share on other sites More sharing options...
Anglefire Posted February 24, 2019 Report Share Posted February 24, 2019 I did do 70miles yesterday and 10ish the day before. 😃 Link to comment Share on other sites More sharing options...
johny Posted February 24, 2019 Report Share Posted February 24, 2019 ok we'll let you stay in as long as you promise to keep it up.... 1 Link to comment Share on other sites More sharing options...
Anglefire Posted February 24, 2019 Report Share Posted February 24, 2019 I also did over 650miles last week in my modern - mostly in 2 days. Must put some more fuel in that too! Link to comment Share on other sites More sharing options...
johny Posted February 24, 2019 Report Share Posted February 24, 2019 No sorry miles in a modern dont count so youve had your first warning🤗 1 Link to comment Share on other sites More sharing options...
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