Technical Disk Brake Performance

[mhatzis]

I have just installed disk brakes on the front and was hoping someone else that has installed them can tell me how they perform as I find them sluggish and not great braking ability. I have bleed the system, any advise would be appreciated.

 

[PuntoHowTo]

If you’ve only just installed them they will take some miles to bed in as a first thought

 

[ClassicFiat500]

Hi I have discs all round, they were fitted before I bought the car 12 months ago, unfortunately I haven’t used the the car this year apart from a 6 mile drive when we moved to a new apartment. I noticed all 4 brakes were starting to bind, I am hoping this is only from not using the car enough since buying it.To release or ease the binding I have sprayed all the pistons with break cleaner. DEFINITELY DON’T fit them on the rear as the guy before me did, it makes the handbrake useless, I have to lock it in gear to hold on a slope, No more handbrake turns as I used to do when I was 18 nearly 60 years ago, when I first bought a 500 in 1966 then another in 69. Best cars for fun after going through 78 cars (including a Bristol, Aston & Porsche’s since then. That’s why I bought this one last year as a last fun project FORGET THE REAR DISCS THOUGH!! CHECK THEY ARE NOT BINDING.
Best of luck but don’t fit them on the rear

 

[fiat500]

No more handbrake turns as I used to do when I was 18 nearly 60 years ago, when I first bought a 500 in 1966 then another in 69. Best cars for fun after going through 78 cars (including a Bristol, Aston & Porsche’s since then. That’s why I bought this one last year as a last fun project

That's the best few lines I've read in a post on here for quite a while...a true enthusiast for the 500. Apart from not having had the benefit of such a wide range of brilliant cars as you and being about half a generation behind you in age, I can re-iterate your main point in that the Fiat 500 is the best car for fun.

 

[Bleeding Knuckles]

I have just installed disk brakes on the front and was hoping someone else that has installed them can tell me how they perform as I find them sluggish and not great braking ability. I have bleed the system, any advise would be appreciated.

Hi Mike, The braking effect of disc brakes on a light car such as the 500 will depend on several factors. Most if not all disc brake mods originate from heavier, if not larger, cars and they may be vacuum assisted in some way. If you drive a modern car the effort your thigh muscle has to impart to brake is far less, so you mentally and physically don't push hard enough to get the same effect. The disc size and type is important as a plain disc is not as efficient as one that is vented or cross drilled (but they are for higher performance applications) and the pad material may not perform until some heat is introduced into them (please note that pad material does vary widely depending on the required use) You will probably find (if your pads are new) that the brakes WILL require bedding in before they perform well. The average bedding in process involves slowing the vehicle from 30mph/50kph to zero multiple times over some 100-200 miles depending on application, but, you must be careful not over do it and allow high levels of heat to dissipate before repeating the process. Most pads have a coating on the material surface that must be worn off and the bedding in process assists in doing this. I have just replaced my original pads (Galfer 139 FF) that are Spanish in origin they were very dirty in use and I'm hoping that a change to Ferodo FDB29 will help with this, but I've yet to start the bedding in process. All in all be prepared to strain your right thigh muscle to get decent braking
Ian.

 

[the hobbler]

What master cylinder have you used? If you have retained the original master-cylinder you will probably have to change the rear wheel cylinders to the SMALLEST (5/8in) available. The calipers use more fluid on an application than wheel cylinders, so you effectively get a 'soft' pedal. When I initially fitted front discs (similar size master cylinder to the original) I had great trouble getting a decent brake pedal until I, as suggested, fitted the smallest rear wheel cylinders, which don't seem to have effected the braking ability of the car to a noteable degree---and it does stop well! And no, I don't have enlarged leg muscles.

 

[the hobbler]

I also agree with "ClassicFiat500" with regard to rear discs. When braking hard, the rear end of a 500 comes so 'light' that even with drum brakes on, you can lock the rear brakes. And of course there is always the 'hand-brake' problem or rather, lack of (how DO you get that through an MOT?).
What front suspension have you got on your car "CassicFiat500"?
For many years I helped run a M/Benz dealership and the most common 'brakes' item to be changed?--the rear discs. Even on a car the weight of a Mercedes (even a small one) the lack of work done by the rear brakes prevents them from 'self-cleaning' as the front discs do, and therefore they corrode badly and the pads seize in the caliper. Nope--can't recommend rear disc brakes on a 500 for just 'road'use, although some Forum members have fitted them.
I think that it was J Leno who once said that you will get more fun driving a slow car as fast as you can, than you will out of driving a fast car slowly. Having driven some VERY fast cars (as a job) in my life, I heartily agree with his comment. My 500 always puts a smile on my face when driving it

 

[ClassicFiat500]

Re the MOT I have never had one done there was one done in 2016 by the previous owner, but there is no way it would pass one now due to the rear brakes. Regarding the suspension , as you see in the photos there is no identification mark on any of it, but I managed to obtain new bushes last year from someone i think from the south coast. I can fid the details if anyone wants them, (they will supply any to your spec & size)

Totally agree with the comment “driving a small car ( & engine) hard, is far more fun than driving a big engine hard. (more likely to kill yourself) “You are controlling the power rather than the power controlling you”
Happy Days!

 

[mhatzis]

Hi Mike, The braking effect of disc brakes on a light car such as the 500 will depend on several factors. Most if not all disc brake mods originate from heavier, if not larger, cars and they may be vacuum assisted in some way. If you drive a modern car the effort your thigh muscle has to impart to brake is far less, so you mentally and physically don't push hard enough to get the same effect. The disc size and type is important as a plain disc is not as efficient as one that is vented or cross drilled (but they are for higher performance applications) and the pad material may not perform until some heat is introduced into them (please note that pad material does vary widely depending on the required use) You will probably find (if your pads are new) that the brakes WILL require bedding in before they perform well. The average bedding in process involves slowing the vehicle from 30mph/50kph to zero multiple times over some 100-200 miles depending on application, but, you must be careful not over do it and allow high levels of heat to dissipate before repeating the process. Most pads have a coating on the material surface that must be worn off and the bedding in process assists in doing this. I have just replaced my original pads (Galfer 139 FF) that are Spanish in origin they were very dirty in use and I'm hoping that a change to Ferodo FDB29 will help with this, but I've yet to start the bedding in process. All in all be prepared to strain your right thigh muscle to get decent braking
Ian.

Thanks Ian,

when we got back from the first drive to the cake shop!!!!!! I realised I had a leak. on closer inspection the hose connecting to the calliper was not done up tight enough and after a few left and right turns it loosed off enough to spray fluid over the tyre. I also forgot to bed them in. so ill have to get on to that tomorrow.

Cheers

 

[Pete145]

Lots of good and relevant answers to the thread already, and it seems like you've found the problem (which is great) but I thought I'd share my experience having converted to front disc brakes a few years ago.

It's already been said that it'll take a little while to bed the pads and disc but, having said that, I noticed an immediate, huge improvement on the standard drums that the disc brakes replaced.

Before the conversion if I'd been driving the 500 for a while and jumped back into a modern car I sometimes used to almost put my chest into the steering wheel from braking too hard! That doesn't happen now and, although not as sharp as a modern car still, the disc brake conversion was instantly much, much better.

Once you fix the leak I'm sure you'll be pleased.

 

[Toshi 975]

Lots of good and relevant answers to the thread already, and it seems like you've found the problem (which is great) but I thought I'd share my experience having converted to front disc brakes a few years ago.

It's already been said that it'll take a little while to bed the pads and disc but, having said that, I noticed an immediate, huge improvement on the standard drums that the disc brakes replaced.

Before the conversion if I'd been driving the 500 for a while and jumped back into a modern car I sometimes used to almost put my chest into the steering wheel from braking too hard! That doesn't happen now and, although not as sharp as a modern car still, the disc brake conversion was instantly much, much better.

Once you fix the leak I'm sure you'll be pleased.

I had pretty much the same experience as you and over the years there have been a couple of occasions when I was pleased to have the discs fitted. I also have no problems using the original master cylinder.

 

[chris3234]

Perhaps it's just the photo but the hole on that disc look extremely large Which can't be good for brake with the reduction of surface area and I wouldn't have thought the discs on a classic 500 would ever get hot enough to require cross drill discs
Or is there a reason for having them.on then car that anyone knows of?