Larger front discs, larger wheels.

[David C]

As I'm planning an engine build (400+HP), so I have to get more stopping power. So next on the list is larger front disc brakes.

My Mach1 has 14" Anser Sprint wheels with discs in the front.
I won't be able to fit larger discs as the callipers are almost touching the wheels.
I'm sticking with Anser Sprint, they offer 15" and 17" wheels.
Any suggestions which way I should go to fit larger front discs, 15" or 17".
If I go with 15" will a I" gain in front disc be worth while?

[booah]

The more disc you have the more surface area for friction and to heat and cool. Bigger is better on the front where mostly the load from braking occurs.

This link may help and there is a link to a diagram for clearance measurements at the bottom.

https://mikemaierinc.com/product/mustang/bundle-dynapro-6-front-big-brake-kit/

http://www.wilwood.com/Images/BrakeKits/WCD_Drawings/WCD_dwg-Large/ds964_wcd-lg.jpg

[BAC]

Any suggestions which way I should go to fit larger front discs, 15" or 17".

Go with 17" - gives you way more options with brakes.  Here's a pic of my '69 Mach 1 with 13" Baer discs behind the 17" Foose alloys:

[shaunp]

The Australian T/A mustangs go faster then we ever will and they have mandated 15" wheel, some of them still run a 4 piston KH mustang caliper on a larger disc. they also have package with a custom hub using a willwood 6 piston caliper that is actually for Corvette. 400hp is just a mild 347 not big to stop that unless you are on a track. Once you lock the wheels its all over no matter what size the brakes are

[Michael H]

Your braking performance is in the caliper, not the rotor.

[Husky350]

Your braking performance is in the caliper, not the rotor.

Sorry man that's not right.

Discs play a massive part in braking performance. The larger the disc, the more mechanical leverage available to stop the wheel moving. If you use the same calipers, and put on a larger disc, the braking performance will improve. In other words, whatever calipers you decided to use, the largest rotor you can use will have the best braking performance.
The other advantage to larger discs is much better heat dissipation in spirited driving, if you do any of it.

The other side to this though is that, although a larger disc is better, you may not need it for your application, and a larger disc will add unsprung weight. And as was already mentioned, no matter how good your brakes you, you need the tires to match them, otherwise you'll just lock up everywhere.

If it was for a street car, a pair of PBR style twin piston calipers with the largest discs you can fit in either 15"(maybe 295) or 17"(around 330) would be a good street system.

[Michael H]

Sorry man that's not right.

Discs play a massive part in braking performance. The larger the disc, the more mechanical leverage available to stop the wheel moving. If you use the same calipers, and put on a larger disc, the braking performance will improve. In other words, whatever calipers you decided to use, the largest rotor you can use will have the best braking performance.
The other advantage to larger discs is much better heat dissipation in spirited driving, if you do any of it.

The other side to this though is that, although a larger disc is better, you may not need it for your application, and a larger disc will add unsprung weight. And as was already mentioned, no matter how good your brakes you, you need the tires to match them, otherwise you'll just lock up everywhere.

If it was for a street car, a pair of PBR style twin piston calipers with the largest discs you can fit in either 15"(maybe 295) or 17"(around 330) would be a good street system.

You are missing the point while trying to state the obvious.

If you have a single piston caliper on a larger rotor, it's not going to stop as well as a 6 piston caliper on a slightly smaller rotor. If you are comparing rotors to rotors, then yes, a bigger rotor will have better performance than a smaller one, all things being equal. Your clamping force is determined by other areas more so than by the rotors. It may well be that just a more powerful booster will do the job with the calipers he already uses. My point for the original poster was that you don't need to buy larger wheels, and therefor, larger rotors to improve braking performance.

[BAC]

you don't need to buy larger wheels, and therefor, larger rotors to improve braking performance.

True, but when weighing up the options of improving braking performance with smaller vs. bigger discs, leaving the wheels out of the equation for the minute it's likely you'll get better bang for your buck with larger discs as the calipers don't need to be as high tech and hydraulic pressures can be lower.  All things being equal, swept area is king.
Plus it gives the OP an excuse to buy some nice shiny new wheels which is always good!   

[Husky350]

You are missing the point while trying to state the obvious.

If you have a single piston caliper on a larger rotor, it's not going to stop as well as a 6 piston caliper on a slightly smaller rotor. If you are comparing rotors to rotors, then yes, a bigger rotor will have better performance than a smaller one, all things being equal. Your clamping force is determined by other areas more so than by the rotors. It may well be that just a more powerful booster will do the job with the calipers he already uses. My point for the original poster was that you don't need to buy larger wheels, and therefor, larger rotors to improve braking performance.

I didn't miss any points. You said braking performance is the caliper, not rotor. That's it. If you wanted to elaborate on what you meant you should have done so.