×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Brake Design - Road Race
2

Brake Design - Road Race

Brake Design - Road Race

(OP)
I am in need of basic brake layout design for road race car. Master cylinder size for front vrs. rear? Bias bar vrs. proportioner? looking for short throw/hard pedal and ability to adjust bias from front (dry track) to rear (wet track). I have master cylinders 5/8, 3/4 and 13/16 in hand. Also a hydraulic porportioner and a bias bar set up. Calipers are equal on all four corners. Smaller tires on front. Origional design information has been lost. Looking for where to start.

RE: Brake Design - Road Race

Cobra kit car? Do a search on "brake bias bars" and you will find a couple of useful threads.

RE: Brake Design - Road Race

(OP)
No, formula car has been full bodied to sports racer. Thanks.

RE: Brake Design - Road Race

Start with putting the largest one for the front and the smallest for the rear, bias bar at 60/40 and than experiment. It depends highly on aerodynamics. Down force can make rears way more useful at high speeds, but what will happen when you slow down?

I didn’t really understand why you would want more rear braking in wet conditions.

RE: Brake Design - Road Race

It's probably more correct to say you want "less front" braking in the wet. Less deceleration G-force means less forward weight transfer in braking. Whether that's meaningful, compared to countless other simultaneous effects, is another matter. Personally, I want the fronts to lock first no matter what, otherwise one goes spinning off the track.

There are more factors than the original poster has mentioned; center of gravity height and position being most significant. It's easiest to figure out graphically. To get an idea of the front/rear brake balance, draw a scale diagram showing the tire contact points with the center of gravity at the correct location with regards to its height and the fore/aft location in the wheelbase. Draw a line from the CG down to intersect the ground at an angle whose slope corresponds to the maximum expected deceleration G-force (e.g. if you expect 0.75 "g" deceleration then the slope has to be 0.75 inch/mm forward for each 1 inch/mm down - hard to explain in words but if you do the drawing it's easy to figure out). Where that intersects the ground, the inverse of the proportions of the lengths from that point to each tire contact patch gives you how much force is on each contact patch and that's the brake balance. Err a bit on the side of front, and there is your first-guess.

This does not account for aerodynamic effects, which can be significant on winged race cars at very high speeds. If the aerodynamics are right then there should be downforce on both the front and rear ...

RE: Brake Design - Road Race

If braking is in essentially a straight line and the rear tracks overlay the front tracks, rear tire grip may be aided by the evacuation of water provided by the front tires.  Think of this as a split-mu situation turned 90°.


Norm

RE: Brake Design - Road Race

(OP)
The info received here, coupled with that from Wilwood tech dept, results in a 3/4" front M/C, 13/16" rear M/C, bias bar at 50/50 and hydro proportioner in rear line set at "0". I'll start with this and fine tune at the track. Thanks for all the input.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources