Wilwood big brake setup

[autotr8er2]

I looked at the Wilwood site and it looks as though you can come up with several setups for brakes with the various hats, rotors and calipers. Are you planning on upgrading the rears as well? I remember you had the calipers and found the rest of the components to fit. Will you have a different approach to building the rears?

[Maxzillian]

I will be doing the rears as well. I am currently held up on measuring the weight balance and center of gravity of the car before I can properly size the rear brake components.

 

The rears are going to pose their own challenge in that they'll require a second set of mechanical calipers to handle parking brake duty. I don't suspect I'll have this done until late summer or fall.

[Cloud81918]

I'm not certain the rears really need upgraded. You can use a proportioning valve to balance the brakes out. They are already pretty healthy vented brakes for the rear of a car.

[Maxzillian]

Well, my intent to upgrade the rear brakes is to minimize the need for a proportioning valve (or balance bar if I go to a dual master cylinder setup as intend). I feel that this will net the best braking performance overall. I can confidently say that after romping the car around Pigeon Forge that the brakes are currently way out of balance. I know, no real surprise, but just letting you guys know.

[old-colt]

I did a Wilwood swap back in the mid 90s using Superlite caliper F&R. I very quickly eliminated the brake booster after flatspotting a second set of race tires. When I put the car back together it will get Dynalites in the rear.

Originally I ran a proportioning valve which was fine once setup but I found the rear pads ran cool, hence the desire to educe the size back there.

The car now has a triple master setup in it which is much easier to live with.

Here is how I mounted the calipers up front, Cut off the upper mount and repositioned it and welded spacers to set the calipers where needed. This fits the common 12 7/8 disc up front nicely.

http://www.vermontel.net/~dcma/Stars/Whity%20strut.JPG

[Maxzillian]

Just a bit of a progress report. I've yet to design the rear brake system, but in the meantime I've been running the car as is and have been doing more research. I've found that the front brakes work GREAT, but because of the piston sizing the car has too much front bias and actually brakes a little worse than stock. This was expected though.

 

However, I was doing some reading on the StopTech website and they explained that the only reason they offer front brake kits is because they size the caliper pistons so that the braking force on the front is close to stock, but use the larger rotors to gain more heat capacity in the braking system. I personally agree with this logic. After beating my head over how to design a rear brake system that incorporates my spare 4 piston calipers as well as a pair of mechanical calipers to handle parking brake duty, I've decided that I'm going to throw my spare calipers on the front of the car instead.

 

The reasoning is that the spare calipers are a 1.38" bore if I recall correctly. The current calipers on the front of the car are a 1.75". After doing some math, I found that if the fronts were changed to 1.38", this should actually drop the effective braking force a little below stock, but should still be much closer than what I currently have. As I never had problems locking up the stock brakes, I don't think this is a problem. I've always felt that our cars don't use enough rear brake anyway.

 

So today I'm going to throw on my 1.38" calipers and run it this weekend at a couple autocrosses. I suspect that in the end I'm just going to leave my rear brakes stock and just use a proportioning valve to balance things out. I honestly think this is the best street solution while still maintaining great brake performance on the track.

 

(I still want to try and fit two piece rotors in the rear though, just so things match. )

 

Edit: Measured my spares and found they were 1.25" pistons. I did find a handy calculator to calculate the effective brake bias:

 

http://www.tceperformanceproducts.com/bias-calculator/

 

Stock: 64.5% front bias

Wilwood 1.75" w/12.75" rotors: 76.2% front bias

Wilwood 1.25" w/12.75" rotors: 62.1% front bias

Wilwood 1.38" w/12.75" rotors: 66.4% front bias

 

So while 1.25" falls slightly below stock, it's not so far that it should have any negative effect (and may be better as more of the rear brakes will be used). The 1.75" calipers were definitely overkill for the stock rears and comes as no surprise that my fronts lock up so early.

 

Looking at the fact that with better traction there is more weight transfer, 1.38" calipers would be best as they slightly increase front bias, but that doesn't factor in how the factory proportioning valve is set. If I'm really lucky, the 1.25" calipers will hit it right on the money and I won't need to change the proportioning valve.

Edited August 26, 2011 by Maxzillian

[TsTKl]

can you list the part number for the aluminum hats? What car is it designed for?

[JohnnyWadd]

Nice work!

[Maxzillian]

can you list the part number for the aluminum hats? What car is it designed for?

 

Third paragraph, first post. If memory serves, they are for a Bel Air. If you search for the part number on Wilwood's site, it should tell you the application.

Edited August 26, 2011 by Maxzillian

[TsTKl]

 

Third paragraph, first post. If memory serves, they are for a Bel Air. If you search for the part number on Wilwood's site, it should tell you the application.

 

my bad, I actually noticed it when I came back to this thread to check if you responed, hahaha.

[JamesR]

Just a bit of a progress report. I've yet to design the rear brake system, but in the meantime I've been running the car as is and have been doing more research. I've found that the front brakes work GREAT, but because of the piston sizing the car has too much front bias and actually brakes a little worse than stock. This was expected though.

 

However, I was doing some reading on the StopTech website and they explained that the only reason they offer front brake kits is because they size the caliper pistons so that the braking force on the front is close to stock, but use the larger rotors to gain more heat capacity in the braking system. I personally agree with this logic. After beating my head over how to design a rear brake system that incorporates my spare 4 piston calipers as well as a pair of mechanical calipers to handle parking brake duty, I've decided that I'm going to throw my spare calipers on the front of the car instead.

 

The reasoning is that the spare calipers are a 1.38" bore if I recall correctly. The current calipers on the front of the car are a 1.75". After doing some math, I found that if the fronts were changed to 1.38", this should actually drop the effective braking force a little below stock, but should still be much closer than what I currently have. As I never had problems locking up the stock brakes, I don't think this is a problem. I've always felt that our cars don't use enough rear brake anyway.

 

So today I'm going to throw on my 1.38" calipers and run it this weekend at a couple autocrosses. I suspect that in the end I'm just going to leave my rear brakes stock and just use a proportioning valve to balance things out. I honestly think this is the best street solution while still maintaining great brake performance on the track.

 

(I still want to try and fit two piece rotors in the rear though, just so things match. )

 

Edit: Measured my spares and found they were 1.25" pistons. I did find a handy calculator to calculate the effective brake bias:

 

http://www.tceperfor...ias-calculator/

 

Stock: 64.5% front bias

Wilwood 1.75" w/12.75" rotors: 76.2% front bias

Wilwood 1.25" w/12.75" rotors: 62.1% front bias

Wilwood 1.38" w/12.75" rotors: 66.4% front bias

 

So while 1.25" falls slightly below stock, it's not so far that it should have any negative effect (and may be better as more of the rear brakes will be used). The 1.75" calipers were definitely overkill for the stock rears and comes as no surprise that my fronts lock up so early.

 

Looking at the fact that with better traction there is more weight transfer, 1.38" calipers would be best as they slightly increase front bias, but that doesn't factor in how the factory proportioning valve is set. If I'm really lucky, the 1.25" calipers will hit it right on the money and I won't need to change the proportioning valve.

 

I bought Oscar's first original brake upgrade back in 2003 and had the same exact issue. It also came with 1.75' bore wilwoods. My fronts would sometimes lock up on the street and autocrossing was really bad. I even had my adj. proportional valve set to mostly rear bias and still had issues. After a few years (around 2006) of trying to find a master cylinder upgrade (me, Oscar, and Art tried for along time for a solution) I did the similar research and came up with the same solution and switched to a 1.38" bore caliper. The guys at Precision Brakes which designed Oscar's kit said the 1.38" was too small and would not work and no one believed it would work. BUT IT SOLVED MY BRAKE ISSUES!!!!! And NO need for a bigger master cylinder. My pedal feel is STIFFER THEN STOCK, but thats how it like it. It's very similar to my RX-7 which is my normal autox car. I haven't had an issue since. Years ago when I last talked to Oscar, I believe he was switching to 1.65" bore which was a new size for wilwoods at the time.

 

Keep us updated on the 1.25" bore.

[Maxzillian]

Thanks for that James, it's good to know I'm looking the right direction. It'd be one thing if I were sticking with my original plan of developing an upgraded rear brake system, but it seems in my best interest just to leave it alone. A lot of the driving force behind this was figuring out that a bias bar is really only good for situations where you're always using maximum braking while a proportioning valve offers better braking performance in low to mid braking situations while still forming the same purpose as a bias bar.

 

Not to mention that I've never gotten the rear brakes hot, so why bother to upgrade them and run the penalty of more rotating mass, more expensive parts, and more unsprung weight? Didn't seem to make sense to me.

 

A full wilwood setup would have a nice wow factor though.

 

I didn't get to try the 1.25" calipers this weekend as planned. Turns out I forgot they were for .8" rotors and don't fit on 1.25" rotors worth a damn. Whoops! Luckily Wilwood makes their calipers in two halves so I'm just going to fabricate a spacer for at least a temporary solution. Possibly permanent depending on how it works out.

[D_Venable]

keep this info coming guys, I've got the Precision Brakes 13" kit sitting here, and it'll find it's way onto my Durban, eventually, and all this testing/info will be beneficial to me soon.

[TsTKl]

I was under the impression that the more simple proportioning valves just "turned down" your rear braking force by restricting flow to the rear. If your problem is too much front braking force you wouldn't be able to adjust it rearword at all. It depends on your set up though. I guess technically you could put one on both the front and the rear and then reduce pressure to the front. Either way though, your adjusting your brake bias at the cost of increasing pedal effort. I like the idea of a bias bar better because your mechanically changing the force going into each individual master cylinder. With a stock style master cylinder your line pressure will be the same in both lines unless you restrict flow in one.

[JamesR]

 

 

I didn't get to try the 1.25" calipers this weekend as planned. Turns out I forgot they were for .8" rotors and don't fit on 1.25" rotors worth a damn. Whoops! Luckily Wilwood makes their calipers in two halves so I'm just going to fabricate a spacer for at least a temporary solution. Possibly permanent depending on how it works out.

 

I think wilwoods are available in different widths depending on part numbers. It's been awhile since I've looked at the catalog. I could be wrong though.

[Maxzillian]

I was under the impression that the more simple proportioning valves just "turned down" your rear braking force by restricting flow to the rear. If your problem is too much front braking force you wouldn't be able to adjust it rearword at all. It depends on your set up though. I guess technically you could put one on both the front and the rear and then reduce pressure to the front. Either way though, your adjusting your brake bias at the cost of increasing pedal effort. I like the idea of a bias bar better because your mechanically changing the force going into each individual master cylinder. With a stock style master cylinder your line pressure will be the same in both lines unless you restrict flow in one.

 

The proportioning valve basically allows equal pressure front to rear up to a certain pressure before pressure to the rear is reduced at a linear rate. Under low braking where little weight transfer occurs, this is better than a bias bar where the braking force is linear and only set to provide the correct brake bias at full braking. For example, just to throw numbers around, a proportioning valve could distribute 60/40% braking at 20% power while a bias bar may be 70/30. Meanwhile at full braking, the proportioning valve could be set to meet 70/30 braking and be equal with the bias bar.

 

What this boils down to is that at moderate braking, a bias bar is actually giving too much front bias. You'd likely never see a problem on the race track, but on the street it can help reduce wear and tear on the front brakes and maybe make a difference in low traction situations.

 

I think wilwoods are available in different widths depending on part numbers. It's been awhile since I've looked at the catalog. I could be wrong though.

 

They are, but I've got these 1.25" bore calipers sitting around and making spacers is much cheaper than buying another pair of calipers.

Edited August 29, 2011 by Maxzillian

[TsTKl]

I hear ya, and thats all and good, but I can just turn the knob on my bias bar for street driving

[Maxzillian]

I like to set it and forget it.

[TsTKl]

I'm putting my adjustment knob where the controls for the rear windsheild whiper used to be. It will be so close to my right hand it will be hard not to toy with it while driving. Plus keeps idiot passengers from turning it to see what it does. In my dsm my innovate LC-1 wideband calibration switch was next to the shifter. You'd be surprised how many people want to press a red button just to see what it does....

[Maxzillian]

Heh, I can't say I've had that problem! Aside from people dicking with the radio controls in the back of my Malibu, but that was intentional.

 

I've got a LC-1 on my car, but the calibration button is at the top forward portion of the ECU cover and pretty difficult to tag with a foot.

[ucw458]

 

I bought Oscar's first original brake upgrade back in 2003 and had the same exact issue. It also came with 1.75' bore wilwoods. My fronts would sometimes lock up on the street and autocrossing was really bad. I even had my adj. proportional valve set to mostly rear bias and still had issues. After a few years (around 2006) of trying to find a master cylinder upgrade (me, Oscar, and Art tried for along time for a solution) I did the similar research and came up with the same solution and switched to a 1.38" bore caliper. The guys at Precision Brakes which designed Oscar's kit said the 1.38" was too small and would not work and no one believed it would work. BUT IT SOLVED MY BRAKE ISSUES!!!!! And NO need for a bigger master cylinder. My pedal feel is STIFFER THEN STOCK, but thats how it like it. It's very similar to my RX-7 which is my normal autox car. I haven't had an issue since. Years ago when I last talked to Oscar, I believe he was switching to 1.65" bore which was a new size for wilwoods at the time.

 

Keep us updated on the 1.25" bore.

 

 

What size rotors are you using? I have oscars kit with 1.75 calipers and 11 7/8" rotors. Rotors are raybestos part # 96329. Is yours the same?

[JamesR]

 

 

What size rotors are you using? I have oscars kit with 1.75 calipers and 11 7/8" rotors. Rotors are raybestos part # 96329. Is yours the same?

 

I bought oscars first group buy which came with 1.75" calipers. I'm not sure what the rotor part number is, but they were for a BMW and where redrilled to the starquest bolt pattern.

[ucw458]

 

I bought oscars first group buy which came with 1.75" calipers. I'm not sure what the rotor part number is, but they were for a BMW and where redrilled to the starquest bolt pattern.

 

 

Can you measure the diameter for me? If they are 12" rotors then I may buy the smaller calipers and put my brake kit on.

[Maxzillian]

A little late on this update, but ultimately I fixed the brake balance problem by doing to a dual master cylinder setup. By carefully selecting different bore sizes between the front and rear brakes as well as using a balance bar to fine tune it, I've managed to bring balance back to the brakes of the car. Typically I have them set to have as much rear bias as I can handle without the brakes throwing out the rear end on corners at autocrosses. On the street this balance seems to work well without problems. See the link below for details (last page for final photos).

 

http://www.starquestclub.com/forum/index.php?showtopic=131151