Many people will tell you that the rear brakes on a Sprite aren’t that important. Forward weight transfer under braking is dramatic, so the front brakes do most of the work. And the back end of a Sprite is already light, so how much could rear brakes actually do?
Turns out, they matter more than you might think (maybe that’s why perhaps every new car has rear disk brakes). For the past few months, I have been doing some informal testing to measure stopping distances. The cars with rear disk brakes stop considerably quicker than those with drum brakes. This testing has made me a believer! If you are into performance, rear disk brakes are worth the investment.
My testing was informal. “Zippy” (red) and “Goldie” (you guessed it) are our test subjects for this post. Both of these cars shown have GPS speedos, so at 30 mph indicated when crossing a chalk line, I applied maximum braking and measured the stopping distance to the center of the front wheel. Goldie has new 165 tires. Zippy has 13 year-old but wider 175 tires. Call their rubber equal? Not the work of the Road & Track technical department but it still provided the information needed. Zippy out-braked Goldie every time.
There are multiple problems with rear drums. Foremost is the shoe to drum interface, which is often less than optimal. Remove any Spridget rear drums and you’ll notice the size of the actual contact patch is often less than 100 percent of the total brake shoe area. They need time to mate, but the shoes often get contaminated with oil or brake fluid before they ever get a chance to marry to the drum. We don’t use our cars enough for the new shoes to wear in such that 100 percent is contacting the drum. Most rear brakes are out of adjustment, which doesn’t help. And we no longer arc or machine our shoes so that they fit the drum on day one.
Add to the mix stuck wheel cylinders, missing steady springs or incorrectly fastened springs and the odds are that your rear brakes are not doing a lot to stop your car. (And if you have old and dried out tires, your braking performance will suffer even if your rear brakes are working properly!
Rear disks guarantee consistency. Every application produces the same results. The pads mate with the disk rapidly, for 100% of the contact patch available. There are few contaminants in the mix that can ruin performance. And they are self-adjusting.
It’s not cheap to convert to rear disks. But the first time you have to make a panic stop to avoid damaging your precious classic car (and/or your passengers), optimal braking is priceless. You can check out our kit by clicking here. Or we’ll be happy to pick up your car anywhere in the country and upgrade your braking system (and your whole car if needed).
And of course you should start with a front disk brake upgrade, which you can do with our kit listed here.
If you are still skeptical, a few months ago, we tested Zippy with the same wheels and tires and rear drum brakes and the best we could do from 30 MPH was 46 feet. Rear disks (see photos above) shaved 10 feet off the braking distance at this speed. You can see that earlier post by clicking here.