New Wilwood compact master cylinders

[Christopher Crowe]

Wilwood is now marketing a compact master cylinder (short casting, remote reservoir), the 260 series. Inexpensive and really nice for packaging in a formula car.

Anybody know anything about these units? Also, has anyone used Wilwood masters otherwise? I've seen their calipers used, but have no idea if the masters are a known quantity in the light formula car community...

Any thoughts on Wilwood masters would be great!

[ghickman]

The Wilwood master cylinders work very well. I've been using them for several years now with zero issues. I carry spares with me but never had to use them.

I believe all of the PRW cars are using them.

One thing I really like about Wilwood is their customer service; they are one of the better brake makers in this area. I can't say that about some of the others I've worked with.

No experience with the compact master cylinders.

[thomschoon]

I have them on all three of my cars, only issue is the caps as sometimes they just dont seal, went to a really blingy billet cap which ended the issue, the last ones I bought seemed to have a revised cap so maybe the issue was solved.

[nulrich]

No experience with Wilwood, but we've been very happy with Tilton's products. The 75 or 76 series would be comparable to the "compact" master cylinders you're considering. Here's a link to all their master cylinders.

If you want something really trick, you could also consider the 77 series. The body has a spherical bearing installed in the rear and the rod is rigid (no ball joint). That significantly reduces hysteresis and variations in brake balance during a braking event. Here are two plots showing a braking event (for Turn 1 at Lime Rock). The red trace is conventional master cylinders (on a Van Diemen), the black trace is 77 series master cylinders (on a Radon).

They are beautiful parts, very small and light, but they ain't cheap.

Nathan

[kea]

The Tilton 77's sound a lot like AP Racings CP5855 series. Or maybe the CP5854 trunnion mounted series.

[Wren]

The tilton 75/76 series are very nice master cylinders for a reasonable price. They are also available in a lot more bore sizes than the Wilwoods appear to be.

I would be hesitant about the Wilwoods.

[starkejt]

Yes, the Tilton 77 are functionally similar to those APs that Keith mentioned. There are a few things about the Tilton 77 series to think about before deciding to use them. First, the price. They usually go for almost $400 each. Sometimes they aren't on the shelf anywhere in the size you need, so it may take a little longer to get one, which can be a pain if you need it ASAP. And you can bet no track vendor will have one, so you better carry a spare. Also, you have to either use the Tilton needle-bearing balance bar that is specific to the 77 series, which is very nice, but costs I think $800 off the top of my head, or have the wherewithal to design and build your own like the Radon. Finally, while you can get a rebuild kit for the 77 series, the outer pushrod seal can only be replaced at the factory. They also must be disassembled carefully to avoid damage to the seals, and you have to pay attention to shim and crush washer thickness when reassembling. All that being said, they are very cool pieces, and I like using them.

[nulrich]

The Tilton 77's sound a lot like AP Racings CP5855 series. Or maybe the CP5854 trunnion mounted series.

Exactly the same concept. Alcon also has a version (MAR5200 series) and Brembo does as well. Dimensionally the Tilton were the most convenient, and they are a bit less expensive (which you'll find hard to believe when you see the SRP on a 77 series part!).

Nathan

[starkejt]

Picture doesn't do justice to the difference in quality between the two parts, but here is a 76 next to a 77. Both 3/4". The 77 feels like it weighs half as much.

[Christopher Crowe]

I think for a start I'll stick with my West Coast Bro and give the Wilwoods a try (you know, buy American and etc.). We'll see...


Nathan, I'm not sure I understand your graph. Is that the pressure differential f to r? If so, what are the increments on the graph? And them, what would cause the wicked fluctuations in the VD's output? Are those pressure hiccups caused by stiction and general mayhem in the VD's balance-bar and fixed master mount-system (as pedal pressure is being modulated in the is full brake mode)?

Thanks again ---

Chris

[Rick Ross]

Chris,

I am sure that Nathan will clarify, but with most data acquisition software, the brake bias plot shows the ratio of front brake system pressure to the sum of the front and rear system pressures. For example:

Brake Bias = Front Pressure / (Front Pressure + Rear Pressure)

Note that these are the measured hydraulic line pressures, not the forces being produced at the calipers.

[nulrich]

Rick is correct. Note that the brake bias is independent of brake pressure, and the bias is forced to zero when brake pressure falls below a certain value.

The initial spike in the black trace is not important, it's just a transient as brake pressure is applied. What you are seeing in the red (Van Diemen) trace is variation in brake bias as pressure is applied and released. It's an artifact of balance bar design and hysteresis caused by off center loads on the master cylinders. Obviously this is not a good thing, since it will affect the balance of the car entering a corner, and prevent you from adjusting the brake bias to the optimum level.

It's not going to make a huge difference in lap time, honestly, but it will make the car more stable and predictable. A sensitive driver will notice it immediately.

I don't have anything bad to say about Wilwood, but you should be aware that Tilton has been designing and building race car parts since 1972, and is based in Buellton, California. I'm pretty sure the 77s are made in the USA.

Nathan

[starkejt]

It's not going to make a huge difference in lap time, honestly, but it will make the car more stable and predictable. A sensitive driver will notice it immediately.

They will also report much better control of the brakes in the wet. The other feedback has been if you lock up the brakes at one end or even just one corner, you can release it much easier without having to back off the pedal as much. Even if you can't measure a huge gain in lap time, giving the driver more confidence in the brakes isn't going to hurt.

[Purple Frog]

Now i get to spend the winter trying to retrofit 77s on my Reynard.

Here is an example of 77s installed....sweet.

[starkejt]

Here's a more "homemade" installation:

Master Cylinders

[Purple Frog]

Josh,
Knowing you and your driver's concern about weight, do you think the middle partition in your assembly is really needed?