Booster or no booster?

[Nick.V70]

Just finishing up a Wilwood 14" front and back kit and also a Wilwood brake master cylinder, question is should I be looking a getting a booster also or not really needed with a big brake kit? I see alot of cars with just the master cylinder so is it for a cleaner look on the fire wall over function?

[Apogee]

You have three options, all of which have their own pros and cons.

The simplest and typically least expensive option is to run manual brakes. They work the same regardless of whether the car is running or not, they're the lightest of all three and they don't require vacuum or power steering to operate properly. Additionally, a properly set up manual system provides the most modulation control and driver feedback since there is nothing between the driver and the master cylinder except for the pedal. The downside to manual brakes is that they typically require more effort to achieve the same brake torques as a boosted system and the pedal travel tends to be longer due to higher pedal ratios and smaller bore master cylinders.

Vacuum assist brakes are good options for cars that make reasonable levels of vacuum at idle. These are relatively simple and fall in between manual and hydroboost in terms of cost and weight as well as boost levels. That said, not all boosters are the same as there are various sizes and configurations, most of which have different effective areas and therefore boost levels for any given vacuum level. The most common booster sizes from smallest to largest effective diaphragm areas are single-9", dual-7", single 10.75", dual-8" and dual-9" configurations. Long duration, high-overlap cams kill vacuum levels, so rumpity builds aren't the most conducive to running vacuum assist brakes. By the time you add an auxiliary vacuum pump and accumulator along with the proper master cylinder and booster, you're nearing the cost of a hydroboost. If you can't muster at least 12 inches Hg at idle, then you're probably wasting your time...I prefer to have at least 14 inches Hg myself. Booster diameter greatly improves pedal feel and feedback, however it also tends to interfere with valve covers, ignition coils and inner fenders, so those tend to be additional limiting factors to running a vacuum booster. Looks are a subjective thing...it looks like a booster.

Hydroboost uses either the power steering pump or an auxiliary electric pump to boost the brake system. Due to the inherently higher pressures involved with these sytems, you have substantially more potential to increase gain than with any vacuum driven system. These units are commonly use in OE applications where there either is no vacuum (like with a diesel) and high boost levels are required/desired. The up side to to these is that pedal travel tends to be minimal and pedal effort is low. The down side is that modulation can be more difficult than either of the previous two options due to the level of boost, particularly with higher coefficient of friction pads, making these systems prone to locking up the tires in some setups with some drivers. Driver skill/technique can go a long ways towards addressing this, but it definitely takes some getting used to and can be difficult in auto-x type environments where you are typically making very quick pedal transitions.

You didn't say what bore size master cylinder you have, which Wilwood calipers (Superlite, W6A, etc) you're running, or the pads...all of which should be taken into consideration when figuring out what you intend to do at the firewall to best suit your needs. No one way is right or wrong, but everything tends to be a compromise, so you need to evaluate your needs and decide what will work the best for you and your budget.

HTH,
Tobin
KORE3

[rjsjea]

Apogee, thanks for taking the time to post

[Nick.V70]

Awesome info and thanks for posting. I will try it mow that it's already together and look at the options from there. I have never ran a set up like this before so I am not sure what option I would want based off what you are saying. Again thanks, should have a test drive some time this coming week, can't wait!