[adneo]

Originally Posted by Jeroen

Just for context; I don’t think any car manufacturer in the world publishes brake distance data.

Several car program have done all sorts of comparisons. One common theme; all cars tend to brake well within the legal limits. But there are difference.

Here a bit dated Topgear test; the little Peugeot has a better stopping distance than the Porsche!

Jeroen

Originally Posted by fiat_tarun

Thank you for this post. Just having disc brakes at the rear does not guarantee good braking performance.

I recall some colleagues measuring braking distances on the track between an i20 with an all disc setup and a Tata Zest. The Zest was out-braking the i20 by far!

Rear discs have the benefits of better heat dissipation but for regular road cars, as long as it's engineered / calibrated well, a rear drum setup can give good braking performance.

I think the point which everyone is missing is that we need to judge the braking setup on the same/similar car. The Peugeot obviously was lighter than the Porsche which was mentioned as well.

Question is do you think the same car like a Rapid or a City will have the same braking distances with a Disc/Drum setup and an all disc setup?

[Jeroen]

Originally Posted by adneo

Question is do you think the same car like a Rapid or a City will have the same braking distances with a Disc/Drum setup and an all disc setup?

Let's get one thing straight:

Disc brakes do not give you a shorter brake distance than drum brakes. With everything the same, a drum brake can produce the exact same stopping power as a drum brake. If it gives you a longer brake distance, the drum brake is simply under dimensioned. Basic engineering.

However, there are some other pro’s and cons that are to be considered. In order for a drum brake to provide the same braking power as a disc brake on an identical car, the drum brake would be bigger and more heavier than the disc brake. You don’t want these heavy things hanging on the suspension. It degrades performance, road holding and so on. That is one of the primary reason you will find discs up front. And in many cases drums at the rear. The rear brakes need to develop a lot less braking power, so a small drum will do nicely. Drum brakes are also cheaper than disc.

There is some debate about which ones are cheaper/easier to maintain. I tend to go with the drum brakes. Whereas you will find quite a few post on our forum about problems with disc brakes (e.g. squeaks, steering wheel wobble etc) you will need to look really hard to find somebody with problems with drums. Probably partly because disc on the front are more critical in terms of balancing and so then whatever you stick on the rear. To be honest, I have had some suspected problems with the rear drum brake on my wife’s Fiesta:

https://www.team-bhp.com/forum/diy-d...ml#post4668210

But then again there is not a whole lot of difference between maintaining discs versus drum, other than the cost! Check out the above thread and you will see me working on all the disc / drum brakes on all my cars. And some of my friends cars too.

Disc brakes are also less prone to fading. Not a huge thing for most of us, unless you do most of your driving in mountainous terrain.

There is a suggestion that disc work better in very wet conditions.

But the main advantage of disc brakes over drum brakes is that you get much higher stopping power for lower weight on the wheels. On any car that is hugely important.

Jeroen

[adneo]

Originally Posted by Jeroen

Let's get one thing straight:

Disc brakes do not give you a shorter brake distance than drum brakes. With everything the same, a drum brake can produce the exact same stopping power as a drum brake. If it gives you a longer brake distance, the drum brake is simply under dimensioned. Basic engineering.

Jeroen

In a way you have substantiated what i have been trying to say, to replicate the same braking efficiency of a Disc brake under similar situations the Drum brakes have to be bigger and heavier thereby negating the cause.

It would be great if someone can show us data that a EU Rapid with an all disc setup stop at the same distance as one with an all drum setup. At this point we are just speculating based on hypothesis.

Honda went a step ahead and even under tyred the City in India.

The major base for my thread is that in India its a common behavior by most manufacturers toncut corners by swapping discs with drums at the rear which is not the case on their European cousins. Since these cars also get designed in the EU, i would assume that there would valid reasons for the team to have put in Discs at the rear in the first place.

Btw just for info trains have also switched from drum brakes to disc brakes on the LHB coaches.

IR RDSO data clearly show a huge improvement in braking distances with the introduction of Disc brakes on the LHB coaches.


We see rear discs on bikes as well and they are not limited to the litre class bikes.

If you are saying that the engineers and designers dumped the drums at the rears and went with discs just for kicks, then i am not sure.

Coming from my experience on similar platforms like Linea, Seltos, the Rapid/Polo (UK) , i have personally observed that there is an ocean of difference between a disc/drum combo and an all disc setup.

But i respect your views and i appreciate your participation in the debate.

Cheers!

[silverado]

Originally Posted by adneo

Time and again I have thanked myself for the decision of picking the TJet since with all the morons we get to encounter on the road there are many situations where very less can be done from the driver's perspective other than hitting the brakes and praying to God!

The second feature which comes really handy in such situations is autonomous brake assist

Cars like the Baleno and Ignis in the UK have Radar assisted braking while they were one of the many omissions that Maruti indulged in while launching the cars in India.

Hitting the brakes and Praying to god! It seems like you are driving above speed limits on most occasions.I can understand you enjoying your Tjet

All the tech goes for a toss if "Anticipation" is missing from driving.With years and years of driving in chaotic conditions, we can anticipate better than our western counterparts.

Radar will go crazy in indian conditions hence fully autonomous driving on our roads will never be possible. It would be "System Overloaded" situation for that car.

The biggest risk with 4 disc setup on our roads is Rear-ending , since most other cars cant brake as quickly as you can. Its a welcome feature but not a deal breaker for me.

[Jeroen]

Originally Posted by adneo

But i respect your views and i appreciate your participation in the debate.

So nice of you.

You’re looking at it from the wrong angle. It is not about disc over drums. It is purely about cost cutting.

I you would find two identical cars, one disc/drum and one disc/disc and you would find the disc/drum would have a larger stopping distance you can not conclude drum brakes are inferior and lead to larger stopping distance.

The appropriate conclusion is they fitted under dimensioned drum brakes! So they were cheap in the first place, to install drums, and then they notched up their cheapness by installing too small ones! It is not so much a technology or engineering or design issue, it is purely a cost cutting issue.

if they fitted really tiny disc at the rear they could perform less than the normal drums too.

On small light cars, rear drums can be perfectly adequate. No problems with my wife’s Ford Fiesta.

We see rear discs on bikes as well and they are not limited to the litre class bikes.

If you are saying that the engineers and designers dumped the drums at the rears and went with discs just for kicks, then i am not sure.

There is a very good reason why we see more and more disc brakes, also, especially, on motor cycles. They are much, much more lighter and smaller. That has huge advantages for handling!

My 1974 Royal Enfield bullet has drum brakes, will not stop at all. Not a drum brake issue as such, but it is just impossible to install large enough drum brakes to get a comparable braking to disc brakes.

To put it in a different way: A disc brake gives superior braking performance compared to drum brake, when comparing the weight of the brake to brake performance. That is it single most important criteria. You get better stopping performance per kilogram of installed brake!

For the same weight near your wheel you can get far better braking performance. Or for less weight the same!

Everything else, is accounting.

When weight and size is not an issue, drum brakes give excellent performance. Look at brake applications on for instance ships anchor winches, or towing winches on anchor handling tugs. They will have what is essentially drum brake type of brakes on the winches. Except on the winches that require very long periods of very hard braking. (running anchor chains for oils rigs for instance). Then they suffer from fading and you will see water-cooled disc brakes and such.

On planes, where weight is everything you will find mostly disc brakes.

For a required brake performance, on a car, a ship a plane, it comes down to a few simple parameters, weight, size, cost.

Jeroen

[Kosfactor]

Originally Posted by adneo

Coming from my experience on similar platforms like Linea, Seltos, the Rapid/Polo (UK) , i have personally observed that there is an ocean of difference between a disc/drum combo and an all disc setup.

Your stopping distance in normal driving is going to be dependent on Speed, Weight, Traction from tires in my opinion.

Considering all new cars come with ABS.

ABS system is going to allow maximum braking without locking up the tires or you can call that threshold braking.

What difference is a rear disk going to make?

By the way, Honda may have given City a size smaller tire but just look at the safety equipment on offer.

[nandrive]

I don't know why people think AEB cannot work in India. I drive a car which has AEB along with host of advanced safety features. Whenever I explain these systems to my family and friends, the first thing they say is those would never work in India. It's not that people/drivers in other parts of the world are programmed to follow traffic rules and never do any wrong. In my car I could customize sensitivity of AEB, it first alerts me by audio visual warnings if it thinks there could be a collision if I don't slow down. It brakes only if the collision is unavoidable, in India too we don't want to kill someone just because s/he jumped in the front, do we? I feel AEB is must have, and it would definitely work in Indian conditions. Could save lives of many.

[Jeroen]

Originally Posted by Kosfactor

Y
Considering all new cars come with ABS.

ABS system is going to allow maximum braking without locking up the tires or you can call that threshold braking.

Correct, we have a thread where ABS vv Drum/Disc brake has been discussed:

https://www.team-bhp.com/forum/road-...-wheels-2.html (Does ABS require disk brakes on all the four wheels?)


Here is a very interesting article on the Ford Fiesta ABS and rear drum brake set up:

https://www.brakeandfrontend.com/201...sta-brake-job/

Ford claims to be using drums to help solve a brake problem on smaller cars:

The standard rear brakes on the Fiesta are a self-adjusting drum system. You might think they did this for cost or weight, but it is Ford’s solution to stop rear brake wear problems that has plagued the rear disc brakes of small cars with electronic brake distribution (EBD).

EBD provides more control over the brakes during normal stops by using the rear brakes more and in different modes. This gives the vehicle better pedal feel, less nosedive and prevents rear brake lock up. But, wear rates for rear disc brake pads was in some cases half the life of the front brake pads.

Several manufacturers tried to correct the problem with new reflash programming procedures and friction materials, but Ford had a different solution for the Fiesta.

Ford stuck with rear drum brakes (ST models have disc). Drum brake shoes typically last longer than brake pads on a rotor of a similar size because there is more friction surface area between the shoe and drum. By doing this, Ford has avoided the problem of rear brake pads wearing out faster than the front pads.

In case anybody still thinks drums are inferior to discs. They do have their use!

Jeroen

[Karvel]

Originally Posted by a4anurag

After driving almost 87,700 kms with disc+drum combination in the Creta, recently got a chance to drive the 2020 Creta Diesel SX(O) equipped with discs all around.

The difference that I could notice was day and night. I was in love how the car responded to brake pedal inputs and also tried emergency braking couple times from 60kmph, 80kmph and 100kmph. The 2020 Creta just stopped with least drama!

I wish Hyundai had given discs all round from Day 1 of Hyundai Creta in India.

Completely agree. In my recent trip to Rajasthan, on NH, a bovine stepped out from a bush from the divider suddenly. I was doing triple digit speed and had to do emergency braking. The rear discs did help a lot and could feel the difference as we had good amount of luggage as well as rear passengers.

All additional safety features, over and above basic items, should be given as option, so that whosoever wants can pay and get them. Denying this has to be relooked.

[agambhandari]

Originally Posted by adneo

The feature which i want to highlight is Rear Discs. Whole buying our sedan, one of the main 3 reasons other than power, handling was braking which led me to drop the Rapid and pick up the Linea TJet. The Vento was dropped immediately after TD because of the pathetic brakes. The Rapid though sharper than the Vento simply couldnt inspire the confidence of a 4 Disc setup found on the Linea. Interestingly both the Rapid and Polo were being sold in the UK with similar engines along with rear discs.

I agree with the fact that the stock brakes on a Rapid/Polo are underwhelming but the reason isn't the lack of rear discs. It's the small front discs!!
The stock ones are 256mm and upgrading to 288mm (Big brake kit) is the easiest way to improve brake feel and have better stopping power. Many members on the forum including me have done this mod and the results are fantastic and i have no qualms with the brakes now. And all this is with the rear brakes still the good old drums.

[adneo]

Originally Posted by Jeroen

Correct, we have a thread where ABS vv Drum/Disc brake has been discussed:

https://www.team-bhp.com/forum/road-...-wheels-2.html (Does ABS require disk brakes on all the four wheels?)


Here is a very interesting article on the Ford Fiesta ABS and rear drum brake set up:

https://www.brakeandfrontend.com/201...sta-brake-job/

Ford claims to be using drums to help solve a brake problem on smaller cars:



In case anybody still thinks drums are inferior to discs. They do have their use!

Jeroen

Firstly I really appreciate your enthusiasm on the topic.

That entire piece from Ford seems very much like Hyundai. The EBD is doing just what is expected, reduce the load on the front rotors, minimize weight shift and maintain brake bias. If the problem mentioned by Ford was the issue , they could have played around with the Brake Bias rather than kicking out the discs altogether. And this time i have some data to prove the hogwash.

The only difference was Hyundai said customer didnt want it, and Ford wanted to sound the hogwash very technical without being technically correct!

2012 - Fiesta - Braking distance - 34.7 m
https://www.which.co.uk/news/2012/05...tances-285596/

2019 - Fiesta - Braking Distance - 43m

https://www.guideautoweb.com/en/make...tions/s-sedan/

I have some observations from your previous post as well but got too much on my plate now.

Will respond at night once i am a bit free.

[Jeroen]

If the problem mentioned by Ford was the issue , they could have played around with the Brake Bias rather than kicking out the discs altogether

No. Adjusting brake bias would not have resolved the issue of pad wear. It would have simply moved it forward. And they did not want to touch the bias, (that would have change the brake performance), just solve the wear of the rear pad whilst keeping the brake performance identical.

Originally Posted by adneo

2012 - Fiesta - Braking distance - 34.7 m

2019 - Fiesta - Braking Distance - 43m

In order to compare the two we need to understate how the braking distances were measured. Whereas the 0-100 km/h is a relative simple measurement and is done pretty similar across the world, the same is not necessarily true for braking distances.

The obvious question is at what speed where these two Fiesta’s travelling for this brake test? Unless they are equal you can’t really compare anything. Other than concluding they both had disc at the front and drums at the rear.

The intricacies of measuring brake distance:

https://racelogic.support/01VBOX_Aut...t_and_Accuracy

Enjoy and keep braking!

Jeroen

[adneo]

Originally Posted by Jeroen

No. Adjusting brake bias would not have resolved the issue of pad wear. It would have simply moved it forward. And they did not want to touch the bias, (that would have change the brake performance), just solve the wear of the rear pad whilst keeping the brake performance identical.





In order to compare the two we need to understate how the braking distances were measured. Whereas the 0-100 km/h is a relative simple measurement and is done pretty similar across the world, the same is not necessarily true for braking distances.

The obvious question is at what speed where these two Fiesta’s travelling for this brake test? Unless they are equal you can’t really compare anything. Other than concluding they both had disc at the front and drums at the rear.

The intricacies of measuring brake distance:

https://racelogic.support/01VBOX_Aut...t_and_Accuracy

Enjoy and keep braking!

Jeroen

The 2012 article does mention it was from 62 mph which is again a standard in the UK since there its more of 0-60 and 60-0 which is close to the 0-100 and 100 - 0. They also mention about GPS being used. The 2019 article talks about 0-100 and then braking distance which i would assume to be same, because inspite of kmph or mph people always baseline similarly. Just like 0-100 kmp becomes 0-62 mph in the UK.

Another fun fact I dug out is Ford proudly claiming that they give rear disc brakes on all cars above 100bhp for the 2017 versions though and 8 percent advantage in braking distance.

https://media.ford.com/content/dam/f...verview_EU.pdf

This just keeps getting better!

Brake baby brake!

[Jeroen]

Originally Posted by adneo

Another fun fact I dug out is Ford proudly claiming that they give rear disc brakes on all cars above 100bhp for the 2017 versions though and 8 percent advantage in braking distance.

The 2019 Fiesta in your original link above claims to have drums at the rear, even though it is over 100BHP?

Originally Posted by adneo

This just keeps getting better!
!

Actually, they are getting worse, a modern Fiesta apparently has a much longer brake distance than the older (by seven years).

2012: 34.7m (disc/drum)
2019: 43m (disc/drum per spec or disc/disc per Ford notes?

Also, as far as I can make out that 43m is an estimation, not measured?

According to your article this Fiesta might have had discs all round and the new suspension. But even if it did not, measured or estimated, why would there be such a huge difference? If it did have the new suspension and discs all round, the difference is even more remarkable?

Of course, new suspension can have a big influence on handling and thus also braking. The way I read it the 8% is related to the new suspension not the discs. (It’s a bit difficult to get 8% improvement on braking distance from rear brakes only!

But irrespective it is odd that a modern Fiesta seems to have much less stopping power as the older one. (remind me, but I think the 2012 and 2019 are essentially the same Fiesta Model, weight and so on)

The plot thickens!

Jeroen

[Kosfactor]

Originally Posted by adneo

Another fun fact I dug out is Ford proudly claiming that they give rear disc brakes on all cars above 100bhp for the 2017 versions though and 8 percent advantage in braking distance.

If there are two models of the same weight, chassis, suspension, abs system, tires, one brake system tuned to work with drum in the rear and one tuned to work with disc in the rear. Chances are the differences are going to be within the margin of error.

Brembo once published a list of 35 best braking cars , they were of course exotic cars and their braking distances while being short were within a few meters of each other.

Link

All those exotic brands would have claimed the heaven and earth in their marketing about the brakes (Carbon ceramic , Kryptonite etc), yet they hardly varied which suggests that braking is more about, Speed, Weight and Traction.

Imagine this, when they first made cars, the brakes were in the rear - Only!
They had not figured out a linkage that can work on wheels that need to steer. If all they needed to do was to increase braking power in the rear, we now would not have any brakes in the front of the cars at all. But they knew the physics and eventually got to adding massive drums on the front axle, 4 wheel brakes as we know now.