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Brake Upgrade in GT

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will the EBC 330x28mm grooved and dimpled vented discs fit on my 1.9 jtd GT. (2010, Cloverleaf) using brake callipers from 166
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hey, i can talk to some guys to check, as i know you cant buy adapters in the store, you need someone to make them for you from technical drawing with measurements. try to buy used one from someone, in my country guys are selling them very often, complet set - calipers, adapters and everything needed, you can choose 310mm or 330mm

edit: complet used set is about 500-600euros here
 

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The linked video (above) explains that OE brakes are specced to be perfectly adequate to cope very well with any reasonable demand in normal road use. I more or less agree with this, but it should be noted that the factory fitted pads will not be rubbish, unlike some cheap aftermarket pads.

A few years back I had an instance of cheap pads fading badly during an emergency stop from about 100kmh or so. The initial 'bite' and braking effect was acceptably OK for maybe 30 metres or so, but then the pads 'outgassed' and the braking effect decreased dramatically, with the car failing to stop as required (would have hit an animal had I not been able to steer around it). I binned those pads and fitted new ones (TRW) then deliberately repeated the 'test', with a hugely improved result, the pads didn't fade and car pulled up in a far shorter distance...

Regards,
John.
Thanks this is exactly what I’m looking for but can you please send me the exact link for where I can buy the adapters because I don’t understand the language, thanks a lot:)
I think it also possible with 305x28 disc for GTa and 916 24V: in that case you dont have to change anything on the discs.
It is done many times on 916's (Gtv/Spider) using 166 calipers andcthecright brackets.
 

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Larger front brakes (on a FWD car) will only improve the car if looked at in their entirety. It's no good just bolting on a few upgrades, even if they're good quality, because each component needs to be matched to its neighbours. Larger discs are fine, so are bigger calipers (and double-sided calipers are ALWAYS superior to single-sided ones in every respect)... But are the calipers now mismatched to the master cylinder? The ratio for swept volume - the relationship between the caliper pistons and the master cylinder's ability to move them - has to be correct otherwise you could actually make the brakes less efficient by fitting larger calipers...... Luckily for us the master cylinder on our cars is large enough to work with 4-piston Brembo calipers.

I have 166 calipers on the front of my car, sprayed a dull gold to mimic Brembo's racing range. I made the brackets so I can bolt them to standard uprights and used Integrale 330mm discs with the PCD re-drilled. I used Lancia discs because they're a little lighter and anything you can do to reduce rotating mass is good. I've also fitted braided hoses, Carbon Lorraine pads and use Motul 600 fluid. Rear brakes are totally standard.
Luggage and bags Bag Wood Gas Automotive design


Are they any better in normal road use? Probably not but then I don't drive like a knob very often.

Are they better on the track? Yes, by a golden mile. Modulation is great, I can feel what they're doing. Power is strong and predictable and, most importantly, there's very little fade.

Bigger brakes are better, but only if thought through carefully.
 

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I agree that ratio of swept volume is very important, and shouldn't be altered significantly at the risk of making the brakes worse. When substituting floating calipers with fixed calipers, the cumulative area of all the caliper pistons should remain about the same (fixed vs floating caliper).

Most commonly the 'new' fixed calipers will have four opposed pistons compared to the floating caliper having only one non opposed piston (though of course some fixed calipers have more than four pistons, and some floating calipers more than one piston). The multiple pistons in the new fixed calipers should have a diameter that is quite a bit less than the diameter of the pistons in the original floating calipers, in order to maintain a similar total piston area as the original floating calipers.

If the piston area in the new fixed calipers is too large relative to the old floating calipers, then the fluid displacement at the MC piston will increase and cause the pedal travel to become longer, as well as changing the fundamental front / rear brake bias. This should be avoided unless we want to pretty much re-engineer the design of the entire braking system, or suffer less effective brakes...

Contrary to what many seem to believe, increasing clamping force at the pads is not why changing from floating to fixed calipers is generally a 'good thing'. Rather, any significant increase in clamping force is likely to be problematic as it will affect the fundamental brake bias, and so any significant change in clamping force should be avoided...

The actual reasons why fixed calipers are generally superior to floating calipers has nothing to do with increased clamping force, but is actually because fixed calipers:

  • Are typically more rigid. A more rigid caliper body reduces pedal travel due to decreased 'sponginess' and free play in the caliper.
  • Can accomodate larger pads, so the pad material runs at a cooler temperature and wears less.
  • Can accomodate more pistons. Multiple pistons acting on each pad causes clamping force to be spread more evenly over the entire pad area (which becomes a bigger deal the larger the pads are).
  • More evenly distibuted clamping force causes the pads to wear more evenly (i.e. reduce taper wear). More even pad wear means the pad faces remain more parallel with the backing plates and so the distance from pad faces to disc faces is more consistent, which means the pedal free play is less affected as the pads become worn.
  • More even pad clamping means that the average pad temperature tends to be lower and more even over the pad area.

(Note: If the substitute fixed calipers were to have only two opposed pistons, then they should both be of the same diameter as the single piston in the oiginal floating calipers because in a floating caliper the piston is in effect 'double acting' in that fluid pressure pushes the piston one way while simultaneously pushing the caliper body equally in the opposite direction. This doesn't happen in a fixed caliper, the fluid pressure only exerting force in one direction.)

Regards,
John.
 

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When new brake pads are fitted in place of old taper worn pads (and taper wear is typically 'normal', usually in two planes along and across the pads, typically more so the shorter the pad length happens to be), there will be an improvement in brake feel due to the new pads having friction faces that are perfectly parallel to the backing plates (unlike the old pads...).

And also, when new discs are fitted there will be an improvement in brake feel due to the new discs having faces that are perfectly flat and parallel to each other (and so both faces at 90° to the action of the caliper), i.e. not worn thinner toward the circumference of the disc (and less worn nearer the hub), as is typical for a worn disc.

Both new pads and / or discs will contribute to a reduction in pedal free play and a more pleasing and confidence inspiring brake feel, independant of whether or not retardation is actually improved (i.e. much of the affect may be subjective, but well worth having none the less since the car feels so much nicer for it...).

I proved this again to myself last week after I noticed that my brake pedal travel seemed to have become noticably greater than it used to be and the brakes no longer felt to be as 'sharp' or generally working quite as well as I recalled some months ago.

Checking the front brakes I extracted the pads and measured thickness with a Vernier caliper. Both pairs of pads had about 0.25mm taper wear in two planes (i.e. along the length and across the width). Using a surface plate with 60 grit emery glued to it, I sanded all four pads until the friction faces were parallel with the backing plates (outside and wear a mask, don't breathe the dust, it probably doesn't contain asbestos but it can't be good to breathe it in whatever it is...). I then checked the rear pads, which were all perfectly parallel to their backing plates (wearing 'flat' I think due to my modification to eliminate the excessive OE slider pin clearances).

Pads refitted and the difference was immediately apparent at the first brake application, with pedal free play reduced to about half (or less, maybe) and significantly decreased sponginess. The brakes just felt so much more 'together' and confidence inspiring than they had previous to 'adjusting' the worn pads.

I've done this quite a few times to various cars over the years, and the result is always the same, i.e. a quite significant and immediate decrease in pedal free play and sponginess, and a strong subjective feeling that the brakes now perform quite a lot better than before. An added benefit appears to be that 'correcting' pad parallelism every now and again during the life of the pads appears to promote more even disc wear, i.e. less 'groove' wear and the disc faces seem less 'tapered' toward the circumference (given some time the newly flat and parallel pad faces tend to 'flatten' slightly uneven disc wear).

I suspect that this is an affect that helps to convince many people that their new 'upgraded' brakes have a bigger affect than they actually do, i.e. the new upgraded pads are flat and parallel with their backing plates, new discs are nice and flat too, so the pedal feel is greatly improved over the worn out parts that have just been replaced. Just fitting new standard parts may well have a had a fairly similar affect.

This is not to say that fixed calipers are not sigificantly superior to floating calipers, I think they are and a worthwhile upgrade. But, when changing from floating calipers to fixed calipers, the apparent and real improvement may not be entirely due to the upgraded calipers, much is probably the result of nice new flat pads and discs.

I also suspect that fixed calipers very probably contribute to (compared to floating calipers) their pads wearing more evenly with less taper in either plane of wear, so are likely worth it from that perspective alone...

Regards,
John.
 

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Short answer here:
The Brembo 4 pot callipers have different sized pistons to prevent (or reduce) taper wear. That is the case with most multi piston callipers.

The leading pistons are smaller so they push less on the leading part of the brake pad.
 

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Short answer here:
The Brembo 4 pot callipers have different sized pistons to prevent (or reduce) taper wear. That is the case with most multi piston callipers.

The leading pistons are smaller so they push less on the leading part of the brake pad.
Yes. I did imply earlier that muliple pistons acting on a pad would more evenly distribute the clamping force over the pad area, but this was a simplification, for the sake of avoiding lengthy explanation...

I'd expect most multi piston calipers (i.e. floating calipers with two pistons or fixed calipers with two or more pistons per side) would typically use different sized pistons to partially compensate for the the self energizing effect created at the leading edge of the pad. Different sized pistons actually cause the hydraulic clamping force to deliberately be unevenly distributed, in an attempt to compensate for the inherent self energizing effect.

Ideally, the lesser clamping force created by the smaller pistons, added to the self energising effect (which acts most strongly nearer the smaller pistons, and most weakly nearer the larger pistons) will combine to become near equal to the clamping force created by the larger pistons (or thereabouts considering that the self energising effect is not a constant but diminishes as the pad wears).

A geometrically created self energizing effect inherently exists in all calipers. This can be compensated for by using different sized 'staggered' pistons, but this only works to an approximate degree because the self energising effect changes from stronger to weaker as the pads become thinner. Pads wear in a longitudinal tapered pattern (as opposed to radial taper wear) due to the variable self energizing effect, which cannot be eliminated, only partially mitigated, as evidenced by pad taper wear being more or less ubiquitous, only differing in degree with different calipers, despite the number of pistons or their relative diameters.

Some calipers may have multiple pistons of the same size, in which case the hydraulic clamping force will be evenly distributed, but, the self energising effect will also add to pad force at and near the leading edge, so in the end the pad will not be evenly pressed against the disc (other than perhaps transiently at a certain pad thickness).

Having noted this, I expect that multi piston calipers with uniform piston diameters would still most probably press the pads more evenly against the disc than single piston floating calipers or dual piston fixed calipers...

Regards,
John.
 

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Best brake upgrade I did was accidental. Brakes seemed a bit variable in weight/effect. I noticed the vacuum pump cover was distorted and leaking some oil. Replaced that with new = more servo effect, and also the turbo became more linear and predictable.

With good disks and pads, and braided lines, I've never felt the stock 147 284mm fronts were inadequate, never had fade.
 

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Not sure that counts as an "upgrade", more of a 'repair'...

Regards,
John.
Quite right :) but a weak vacuum pump on a diesel can (and did, here) go unnoticed, and the reduced servo effect = apparently weak brakes. So seemed worth mentioning.

The pump (on the end of a camshaft) depends on engine revs. The only symptom I (eventually) noticed was brakes getting heavier in stop/start traffic when revs were consistently low, and the vacuum in the servo reservoir became depleted by repeated applications.

When I bought the car I thought the brakes were OK, but at times lacked confidence. It passed MOT with no trouble, yet I thought they should be better. Discs were worn and I changed them and fitted new pads (all Ferodo) and braided lines, new rear calipers and fluid, but changing the pump (about 6m later) fixed the confidence and consistency that had been missing.
 
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