Doing my 300mm disc conversion for R15 windmill wheels I've ran in to some problems not reported elsewhere or downplayed. Thought some might find it useful and save some quid.
I've used :
3mm spacer
ST170 Ford Focus Mk1 discs (the base plate is ~1.3mm thicker than that of a Puma)
Ford Mondeo Mk3 calipers
Carriers
Had to grind the carriers to a thickness of 6.5mm. That is almost half of the thickness and left a gap of ~2.5mm between the carrier and the rim.
Also the corners of the carrier had to be rounded off. Beware, the iron wall of the slider pin tunnel gets really thin, quite easy to overdo if you rush it.
Calipers
If the brake pads are worn to only few millimeters, then everything fits. Yet, if you install new or only slightly worn pads, the caliper itself sits so far outside you'll also have to grind ~3-6mm of the caliper itself. Truth be told, I haven't grinded the caliper. When I tried fitting the wheel, to my eye, there seemed such a big gap between the wheel and disc, that I lost hope.
ST170 disc and Mondeo caliper mating
I apologize the photo quality is not great. So much of the disc is left unused, I wonder if a 280mm conversion doesn't offer as much heat dissipation with less excess weight.
Its not as bad on the side closer to the center, however, again, ~3mm of the disc is unused:
Weight
Unsprung weight is an important characteristic of a car.
Calliper: Mondeo Mk3 – 5.3kg vs Puma 3.7kg
Disc: ST 170 – 7.1kg vs Puma 3.8kg
Total difference: +4.9kg per corner
Brake balance
A wonderful, detailed article is written at turnfast.com
http://turnfast.com/tech_brakes/brakes_balancing" onclick="window.open(this.href);return false;
In short, bigger brakes are only for heat dissipation. You don't get better stopping by increasing the brake size. The front has as much braking power as the front tires have. If you put bigger brakes at front and do nothing to the rear, you gain nothing at the front and loose stopping power at the rear. Because now, when you press the brake pedal, say, halfway - the front already starts to lock-up, but the rear is no-where-near it maximum braking point.
These are purely theoretical and VERY rough at that, I used the formulas provided by turnfast.com.
Say 2% (according to Nissan engineers) of the car's weight moves to the front when braking and the standard puma brakes are spot-on for that brake balance - 65-35. So the front and rear would lock up at exactly the same moment.
300mm disc are way more powerful than the standard 236mm. So I guess that 300mm disc at front and standard drums at the rear would provide a brake power balance of maybe 90 – 10. Front still has the same braking force/stopping power, so I calculated roughly how much braking force I would lose at the rear with these numbers.
Standard front 270 rear 158
90/10 front 270 rear 30
True the rear tires do less work at braking, but now they almost do nothing at all. Again this is only to illustrate a point not to provide exact numbers/data. I recommend reading the turnfast.com article and drawing conclusions for yourself.
I've used :
3mm spacer
ST170 Ford Focus Mk1 discs (the base plate is ~1.3mm thicker than that of a Puma)
Ford Mondeo Mk3 calipers
Carriers
Had to grind the carriers to a thickness of 6.5mm. That is almost half of the thickness and left a gap of ~2.5mm between the carrier and the rim.
Also the corners of the carrier had to be rounded off. Beware, the iron wall of the slider pin tunnel gets really thin, quite easy to overdo if you rush it.
Calipers
If the brake pads are worn to only few millimeters, then everything fits. Yet, if you install new or only slightly worn pads, the caliper itself sits so far outside you'll also have to grind ~3-6mm of the caliper itself. Truth be told, I haven't grinded the caliper. When I tried fitting the wheel, to my eye, there seemed such a big gap between the wheel and disc, that I lost hope.
ST170 disc and Mondeo caliper mating
I apologize the photo quality is not great. So much of the disc is left unused, I wonder if a 280mm conversion doesn't offer as much heat dissipation with less excess weight.
Its not as bad on the side closer to the center, however, again, ~3mm of the disc is unused:
Weight
Unsprung weight is an important characteristic of a car.
Calliper: Mondeo Mk3 – 5.3kg vs Puma 3.7kg
Disc: ST 170 – 7.1kg vs Puma 3.8kg
Total difference: +4.9kg per corner
Brake balance
A wonderful, detailed article is written at turnfast.com
http://turnfast.com/tech_brakes/brakes_balancing" onclick="window.open(this.href);return false;
In short, bigger brakes are only for heat dissipation. You don't get better stopping by increasing the brake size. The front has as much braking power as the front tires have. If you put bigger brakes at front and do nothing to the rear, you gain nothing at the front and loose stopping power at the rear. Because now, when you press the brake pedal, say, halfway - the front already starts to lock-up, but the rear is no-where-near it maximum braking point.
These are purely theoretical and VERY rough at that, I used the formulas provided by turnfast.com.
Say 2% (according to Nissan engineers) of the car's weight moves to the front when braking and the standard puma brakes are spot-on for that brake balance - 65-35. So the front and rear would lock up at exactly the same moment.
300mm disc are way more powerful than the standard 236mm. So I guess that 300mm disc at front and standard drums at the rear would provide a brake power balance of maybe 90 – 10. Front still has the same braking force/stopping power, so I calculated roughly how much braking force I would lose at the rear with these numbers.
Standard front 270 rear 158
90/10 front 270 rear 30
True the rear tires do less work at braking, but now they almost do nothing at all. Again this is only to illustrate a point not to provide exact numbers/data. I recommend reading the turnfast.com article and drawing conclusions for yourself.