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Old 13th March 2016, 21:10   #31
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Default Re: Automotive misconceptions demystified

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Would increasing the pad dimensions (not disc diameter) increase braking 'efficiency' in a disc brake system?

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Yes, and that's what's done often, but I guesstimate there is a loss of pressure (keeping the same net force, increasing the pad-disk contact area). Pads are often in light contact with the disc anyhow, so it takes a bit of pressure to generate enough friction force. When stronger braking is required, the number of pistons may be increased rather than make the pistons larger - such as 6 piston callipers on 1200cc+ bikes whereas 600-1000cc bikes have typically 4 piston callipers. Piston size , to my knowledge, doesn't vary much between 250cc and 1200-1400cc bikes , with 32-34mm being the usual range. Some modern callipers may employ separate pads per piston than a single conjoined pad over 2 or 3 pistons per side.
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Old 13th March 2016, 21:41   #32
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Default Re: Automotive misconceptions demystified

^^^
Was talking of pad contact area, not pistons.

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Old 13th March 2016, 23:40   #33
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Default Re: Automotive misconceptions demystified

Thanks for such a lovely thread, I can forward the link of this thread to so many people who have such misconceptions and i usually don't even try making them understand verbally.
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Old 14th March 2016, 08:45   #34
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Yes, and that's what's done often, .
I'm not so sure that increasing the size of the pads will increase braking. I'm pretty sure it doesn't actually. With disk brakes it is all about clamping force. As the clamping force remains the same the braking action will remain roughly the same.

To your earlier point, you need to increase the calliper dimension pistons or find a way to increase the pressure (in a hydraulic brake system) e.g. booster, multi piston or just push the brake pedal harder.

If you increase the diameter of the rotor and keep the same pads, that would certainly increase braking effectiveness.

http://stoptech.com/technical-suppor...rade-selection

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Old 14th March 2016, 08:56   #35
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Thanks for this amazing thread, 5 stars!. Puts a lot of misconceptions to rest. Especially the bull bars part. A couple of friends of mine had to work on their chassis to pull it back to proper shape after a head on collision with the bull bar attached. The problem is, even after the repairs, the chassis had issues which was noticeable with the unstable ride quality which wasn't present before the incident. I guess, unfortunately these extra attachments cause permanent damage to an extent depending on the collision which can only be rectified to a point.
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Old 14th March 2016, 09:17   #36
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Default Re: Automotive misconceptions demystified

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Originally Posted by Sutripta View Post
Would increasing the pad dimensions (not disc diameter) increase braking 'efficiency' in a disc brake system?

Regards
Sutripta
Sure. Braking force is a function of friction and friction is proportional to the cross sectional area between two surfaces.

This is the reason behind the pad's curved design to capture as much disc as possible. Also you can notice massive pad size used in high performance cars; however there is a relation of cooling disc as well which restricts complete coverage.
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Old 14th March 2016, 10:05   #37
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Default Re: Automotive misconceptions demystified

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Thankfully, premium branded fuels have disappeared from pumps in India.
Premium petrol have been reintroduced in most pumps again.

Premium petrols were never really discontinued. They were removed from most pumps when prices of petrol rose as the demand for premium petrol substantially reduced with the hike in prices. They were still available at a few company owned pumps.

Now that prices have reduced, they have become available at regular pumps too albeit not to the extent they were available earlier.

When premium petrol was introduced they had a higher RON rating than regular premium. Premium was at 91 RON whereas regular was at 87 RON. Now regular and premium are both at 91 RON.

Performance on using premium petrol used to increase in cars that had knock sensors on account of the higher RON rating.

Last edited by VeyronSuperSprt : 14th March 2016 at 10:18.
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Old 14th March 2016, 11:15   #38
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Default Re: Automotive misconceptions demystified

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Premium petrol have been reintroduced in most pumps again.
Premium petrols were never really discontinued.
+1.

They just cannot take them away after having invested. They just disappeared for a year or two when the cost was high.

But the tactics remain yet. When you ask for premium petrol, they give you the lamest excuse such as:

1. Credit card payment for that dispenser will not work sir.
2. Operator is not available.
3. Problem with dispenser.
4. Closed the dispenser.
5. No stock. Even though they have it.

Premium fuels have their benefits which is very evident. We just cannot dismiss them as snake oil story. For a person who has been using premium fuel regularly, the difference is not noticeable when they shift to normal since their system is cleaner. Difference will be noticeable only after few fills. But for a person who shifts from normal to premium will notice within couple of tank fills.

Same goes with synthetic and mineral engine oils. Synthetics are much much superior to their mineral peers provided engine has been maintained in its top condition.

Having ploughed the engine and then shifting to synthetic and crying that there is no noticeable effect is like a corrupt politician seeking penance for all wrong doings in life. No matter what you do, the result will be same and no difference.
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Old 14th March 2016, 11:23   #39
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Engine oils

just remember to change the engine oil sooner than your car's manufacturer recommends. And stick to the recommended grade, viscosity and specification of oil as mentioned in the owner's handbook.
I'm doing the exact opposite here.
Honda city 3rd gen oil change recommendation is 5000 kms with regular oil, but I've switched to 10000 and synthetic, does that mean I'm damaging the engine or reducing it's life? Did quite a bit of research on this and also had a brief discussion with Honda tech guys, and only after getting positive answers I started doing so.
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Old 14th March 2016, 12:05   #40
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I'm doing the exact opposite here.
Honda city 3rd gen oil change recommendation is 5000 kms with regular oil, but I've switched to 10000 and synthetic, does that mean I'm damaging the engine or reducing it's life? Did quite a bit of research on this and also had a brief discussion with Honda tech guys, and only after getting positive answers I started doing so.
Is the guy going to pay for the repair of your engine if it falls to bit?

When it comes to oil, stick to the original Manufacturers specification.
The brand of oil is of no importance, really, the compliance to the specification is!
- Only switch to to synthethic if you have it in writing from the manufacturer. E.g. the owners manual mentions it, or there is an official service bulleting.
Don't believe to much when it comes to oil advise on the internet. Very few of us have the insight or access to real data to make a meaningful contribution.

Did you stick to changing the oil filter at the original 5000 km or are you changing that at 10.000 km a swell. If you do, that is likely to be your biggest 'exposure' on wear and tear long term.


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Old 14th March 2016, 12:17   #41
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Default Re: Automotive misconceptions demystified

The braking efficiency;in terms of force for a given braking effort; is dependent on the friction area. So yes increasing the area will increase braking, but then the pressure (force/area) on the pads decreases, hence you will have to increase the hydraulic mechanical advantage to achieve better breaking with larger pad area. This is done in a number of ways for performance cars
. Have longer pads, but that requires better designed calipers otherwise excessive length will cause flexing at the ends negating the longer pads.
. Having broader pad. This requires larger diameter disks.
. Having two sets of calipers. This is most efficient as you need not change the disk diameter or any other thing.

That said, you can also boost breaking power by having more force act on the pads - increase the number of calipers. That will also ensure that the longer pads do not flex.
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Old 14th March 2016, 12:38   #42
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Default Re: Automotive misconceptions demystified

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  • Switching off the engine at short stops actually consumes more fuel to fire up the engine again, than if it was allowed to idle.
  • Repeatedly starting and stopping engines (especially turbo-charged engines) causes more expensive harm than a paltry saving in fuel consumption can compensate for.
Does this apply to the new Ertiga SHVS as well? Because it has this functionality as a feature! I understand that it has ISG for restarting the car but will there be any side-effect on turbo-charged engine?
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Old 14th March 2016, 12:50   #43
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Default Re: Automotive misconceptions demystified

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Originally Posted by skyliner34 View Post
I'm doing the exact opposite here.
Honda city 3rd gen oil change recommendation is 5000 kms with regular oil, but I've switched to 10000 and synthetic, does that mean I'm damaging the engine or reducing it's life? Did quite a bit of research on this and also had a brief discussion with Honda tech guys, and only after getting positive answers I started doing so.
Follow the service manual / warranty conditions of Honda. Oil grades and oil change intervals should be as per manufacturer conditions ONLY if you want to save warranty partly. In any case the blame of part failure will again be on you and you have to prove your innocence similar to IPC 498A or dowry harassment cases.

If you are planning to go synthetic, it is recommended to for 7500 Km drain period. I drain the oil poured by Maruti during my service within 2 - 3 weeks and pour in synthetic of my choice. This way I save my warranty and limit to minimal blame.
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Old 14th March 2016, 13:47   #44
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Driving for fuel efficiency[*]Switching off the engine at short stops actually consumes more fuel to fire up the engine again, than if it was allowed to idle.[*]Repeatedly starting and stopping engines (especially turbo-charged engines) causes more expensive harm than a paltry saving in fuel consumption can compensate for.[/list][/left]
[/center]
Brilliant work! Another one of those supremely informative and well put together threads to have spun on the forum!

My friend's XUV has had a change of turbo TWICE in 3 years! I strongly suspect the start-stop system to have a major hand in the turbo failures. A case of penny-wise, pound foolish?
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Old 14th March 2016, 14:43   #45
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Default Re: Automotive misconceptions demystified

Excellent informative thread SS-Traveller. Rated 5 stars. Would like to hear about your take on some other topics like heavier cars are safer, FWDs cannot be as much fun as RWDs.
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