Spongy Brakes

[Ron Sutton]

Originally Posted by chr2002ca

Here's a simple question. Anybody here running the 7/8" Wilwood master cylinder with a manual brake setup that doesn't feel a little spongy? I have that same setup and mine is slightly spongy also. I was doing some research on it a few months ago and it seems that it's a fairly common side effect as you reduce the bore size on a master cylinder in a manual setup(regardless of the calipers). As you increase the bore size, you get a harder pedal, but less brake pressure.

I'm sure there are plenty of people out there are running this master cylinder and bore size OR have done so in the past that could chime in. Would love to hear from someone who has this exact setup(Wilwood MC, 7/8", manual brakes, 4 disc) and can say they have a hard pedal.

I have a few thoughts & would add, if you're comparing your manual brakes to power boosted brakes, the feel is going to be very different. Power brakes travel shorter & get really hard. If you want factory production street car braking feel, you may want to utilize a boosted system.

I'll preface what I'm about to say ... as this applies to race cars & hardcore PT cars that do track days. You don't need, nor want, that short travel, hard pedal feel in a hardcore performance or track car braking system. It makes it hard to modulate the brakes & they act more like an "on/off" switch.

For racing, hardcore PT cars & track cars ... you need:
1. To be able to easily modulate the braking pressure with pedal position instead of intense leg pressure.
2. You can't afford for the brakes to be all or nothing ... or anywhere close to it. So you need more pedal travel than a street car to have easily controlled modulation.
3. You want to be able to apply moderate foot pressure (say 100#) & achieve serious braking.
4. You don't want the brakes to "wear you out" on an hour session at the road course, braking 10-12 times a lap.

If all of this above does not apply to your type of driving, you may want to consider a more street style braking system with a power booster. If all of this above does apply to your style of braking ... and you don't have enough braking force ... I would recommend you look into ways to increase your braking force without adding more pedal travel ... which is larger rotor size and/or more aggressive brake pad compounds.

Compounds are a much bigger change than people think. Changing to a brake pad with .05 higher CoF adds a little more braking force than going up 1" in rotor size.

[Sieg]

Per usual, excellent point Ron.

We tend to forget that many of the younger generations may have never had any experience with manual brake systems.

My first muscle car ('66 GTO) had manual drums.......Fred Flintstone could stop faster than that car.

[Ron Sutton]

Originally Posted by Sieg

Per usual, excellent point Ron.

We tend to forget that many of the younger generations may have never had any experience with manual brake systems.

My first muscle car ('66 GTO) had manual drums.......Fred Flintstone could stop faster than that car.