Fabia vRS Combi 312mm brake conversion

[group 3]

I don't know about the fluid but good pads make a massive difference to braking ability. Because you haven't increased the swept area of the pads the gain made from bigger disks is around 8% - you would have got that from better pads alone. The change in pedal feel is likely unrelated. It will definitely look better though.

The change in pedal feel is entirely the point of going to the 312mm and 256mm discs, I doubt that the car stops in much if any shorter distance than before, my gripe was that the standard brakes have a very low bite point before they really seem to do any work. Better pads probably would've improved it somewhat but I doubt it would've given me the same results.

But if you don't want to take my word for it this is what AP racing have to say on the subject;

AP Racing Formula Brake Kits come supplied with large diameter discs. The ventilated discs have either 24, 30 or 48 cooling vanes depending on the application, to draw air through the centre of the discs. They are handed left and right, and are cross drilled or grooved, again, depending on the application, to allow gasses that build up on the surface to escape. Where cross drilling is used it is more restrained than on the face of our full race discs, as pad longevity is more important on a road car than weight saving. The discs are wider and of a larger diameter than standard. The extra material controls heat build up and the larger diameter means that the caliper can be mounted further away from the centre increasing the leverage effect, which increases braking torque while decreasing effort required on the pedal.

[benoz11]

Yup, about 8% less. You would have got the same effect with better pads.
I'm not saying it's not worthwhile - if you combine the bigger rotors with better pads you will have a great track day setup as the improvements will add together and as you say they look better I'm just pointing out that there is a cheaper easier option for others.

Personally I don't think there is anything wrong with the stock pedal feel but with brakes you need to be comfortable that they will do the job

[gavs]

I think you're putting a lot of faith in brake fluid and pads if you really believe that makes all the difference, I used ordinary off the shelf Dot 4 fluid and a set of everyday Bendix pads. I tried the VCDS change and wasn't overly impressed and yes I did replace the calipers.

I think you're ignoring the increased leverage effect that the larger discs have on braking performance and feel.

About the only thing I do agree with in your post is the increase in unsprung weight.

Your pedal feel is dictated by the electronics that the car sends back to the pedal. I have driven 3 6r polo gti's and 2 had great pedal feel and the last was rubbish, all in stock setup but with different software versions. Same as the steering weight can be adjusted, brake pedal feel can be adjusted.

Yes, I put MASSIVE faith in just fluid and pads because they are the 2 major factors in making you stop shorter for longer.

Yes you just bought generic DOT4 fluid off the shelf and bled and refilled the reservoir but let me ask you this... How old was the brake fluid to begin with that you drained out? Regarding pads, bendix make pretty bloody good pads for the coin and VAG pads are more oriented at comfort and refinement rather than performance so you don't get squealing etc.

Yes the ability to have a stronger handle force will retard the rotation quicker but the extra weight that has been added will offset this effect. My tip would be that when you get some free coin, buy some lightweight 3 piece rotors with aluminum top hats. You can save up to 3 kgs per corner just by going to lightweight hats. This will help offset the fact that you have added all the extra rotational mass which means that the car is working harder to spin those wheels. Like adding bigger tyres on a 4x4 makes it considerably easier to snap axles, adding bigger discs makes it harder to spin the wheels.

[noone]

Yup, about 8% less.

Its a funny debate / idea, personally I think the added weight is worth it. Addition of unsprung weight is only relative to the front wheels as its a fwd car.

I have 312's on the front of mine, have tried a few different sets of pads, etc. about to do the rears, I ended up with quattro carriers for the rears which don't fit (not even with the ECS spacer kit), propper ones just arived this week. I understand what people say about changing the pads, fluids, etc, but IMO the feel of the 312's is totally different to the stock front brakes which felt rubbish, even with better pads. Looking forward to the balanced set.

I don't agree with the percentages, or examples of what works on another car (eg software tweaking, I've not tried on mine). Brake feel is something somewhat personal, how do you measure feel in a percentage? I know when I use my brakes I barely have to touch them to quickly stop, worth the money over the stock system which always felt inadequate. The stock system could pull up just fine, but for feel and tracking (where the repetition of heat buildup makes little differences feel huge) the added bite really helps. Again, each to their own, the fastest Polo @ wakefield (owned by a person, not a tuning company) runs stock brakes with better pads, fluids, rotors, etc. There is much more to brakes than the rotor size, if I really wanted to do it properly, I'd ditch the basic single pot floating caliper design for something like the porsche 6 pot design (sexy and bitey).

Each to their own, for less than $1k I have a fully upgraded braking system to my needs, some will spend that on a nice set of pads, fluid and rotors.

[benoz11]

Well I for one think you've improved the car and given yourself scope for further improvement down the track if need be.

[BrashDaniels]

Great Thread OP - excellent info and just the setup I was considering - anyone got a brand / distributor recommendation?