Contour Enthusiasts Group Archives Forums Modifications Brakes Sheared a Caliper Bracket 2 Nuckle Bolt - FSVT - ?

Had a scary little incident happen with my fairly new Focus SVT front brakes last night.

Driving 40 mph down a super busy 4 lane road. Hear a thud, sounds like a flat. Slow down and coast over. As I am pulling over, about 10 mph now, the car screeches and stops in the right lane. I put it in nuetral and jump out to look for visual damage...Nothing I could see. I first thought it was my diff due to previous MTX-75 failures (im on my soon to be 4th trans-x). Traffic died down and I needed to get my car off the road so I tried reverse and it went freely. So I backed about a 1/2 mile to a Bennits BBQ parking lot to check it out. I found my car mag-lite (a must) and saw what happened...

Apparently the top bolt that goes from the steering nuckle to the caliper bracket sheared off, it was gone and only old threads remained! The caliper was resting against the wheel and the bottom bolt was about to go. The wheel was scratched from the caliper dragging and catching the car but nothing too serious. None of the other parts were damaged other then scratches. The caliper would have definitely came loose and ripped the hose in half if I had the factory rubber lines. The Aeroquip/Mocal stainless braided line held up great and didn't show any sign of damage. The steering nuckle wasn't as fortunate. It bent at the mounting tab of the bottom caliper bracket bolt pretty badly. I straightened it best as possible on the road and limped it the 10 miles or so home.

I found a used nuckle for $70 locally and picked it up. The old nuckle is already off and the car is in it's favorite spot, the garage, and on stands. I am going to finish up putting it all back together tomorrow but I am nervous that this will happen again. I assembled all of it using factory hardware and torque specs exactly 3,000 miles a go. It has had no signs of any problems until this. Do you think the increased surface area and braking of the FSVT fronts increased the load on the bolt (Metric 10.9 btw) finding it's weak link? I am going to try a little longer of a bolt since there is room. The factory bolt with the spacer had plenty of thread in the bracket but maybe the length it lost from the spacer (1-2 threads max) was just enough to cause a problem with more load on the bolt. I will post pictures of all of this tomorrow.

To the few others with the FSVT fronts. Did you use longer bolts? If not...How many miles on the front brakes with factory bolts? Maybe I drive my car more and have just been the first one to find a problem with the swap. I am also thinking that the whole idea of spacing the bracket away from the nice solid strong nuckle with a 1/2 washer isn't the best idea. Do the Baer/Wilwood/TCE kits have custom brackets that fit the nuckle or do they use some kind of a "spacer" too? TIA - Sorry for the long read!

NO.

I wondered about this possibility before when first reading about your conversion, let me explain my thoughts:

The caliper bracket has a certain amount of surface area where it is clamped to the steering knuckle. The bolt provides the torque, but it is the friction of the two surfaces that keeps the caliper bracket from sliding. The bolt by itself is not strong enough.
When you put a washer in as as spacer, it would have seriously reduced the amount of contact surface area between the bracket and the knuckle. The new surface area is the size of the washer and this may not be enough to hold the caliper bracket from sliding. Then its just pressure on the bolt that holds it.

The best fix would be to have a spacer made that uses all the surface area on the mounting point. I would even recommend welding the new spacer onto the caliper bracket so you only have one frictional surface to deal with.
You already know the thickness you need, you should take the brackets to a metalworking or machine shop and tell them what you need. Maybe $30-50 later you could have a one piece bracket for you conversion.

Tom

I used new bolts, but not longer ones. The difference in length is minimal, there's plenty of thread on the stock bolts to hold the caliper on. I've got atleast 5 thousand miles on my FSVT brakes with no problems. Sorry to hear what happened and I am glad you were not hurt.

can you provide photos? of what is left of the bolt (I realize most of it is gone, but the broken face of what is left may tell us why it broke . . .)

Longer bolts won't make a difference. They only need to be as long as the height of the material being bolted. Any longer is just excess.

The interference of the parts is true in part, but the bolt still has some sheer aspect to it also. As for spacers, the ones I use are the same diameter of the ears on the knukles at the flat spots. This is usually about 1.000" on most kits.

Welding them in place won't do all the much for you and in fact if you get them too hot you may warp them as they are put in place. We shim calipers all the time and so too do many Wilwood kits, just like your cam sprockets they rely on good clamp loads and interference of the parts.

Sorry to say it, but my money is on one of them not being tightened properly or some debri preventing it from being seated all the way. Be sure the surfaces are clean and free of burs.

Ok, maybe don't weld them. But do you think that I'm on the right track with the surface area being to small with provided clamping load?

warmonger

The surface area being to small is the only problem I can think of. The factory bolts were plenty long and metric 10.9 so they should have beeen fine! I torqued every bolt to factory tq spec and used new caliper brackets that had new clean threads.

I am going to finish re-assembling it soon and will post pictures afterwards. Hopefully this was a freak incident and will not happen again! I do have 1 of the bolts left and can take a picture of it no problem. For now I am going to use the same setup only utilizing bolts that are a hair longer and larger diameter spacers.

Thanks for all the help. I was kinda thinking down the same track. Knowing that Todd and Wilwood use spacers on some of their sweet kits also makes me feel much better!!