7 replies to this topic

[Todd Green]

Most are probably aware that the upper guide pin on the rear calipers likes to work itself out and should be checked, but have any had it actually shear?  We've had it happen three times now in a year on one car.  My other car hasn't had any issues (though it has Xidas on it which deal with the rumbles much better).  It is the right (passenger) rear and we're a counter-clockwise track, so it is the one that takes the brunt of the rumble strips.  The car has a stock motor (+ header and SM intake), 190K+ mile original bushings on it and the RR upright bushing is definitely shot, cheap eBay Chinese coilovers, stock sway bars.  The caliper was replaced at the end of last year (though ran a 6 hour enduro and ~4 race weekends), the bracket does't look bent (via holding it up to another bracket).  New bushings are in the works, and hopefully a better suspension if I can get my codrivers to go for it. 

 

[Bench Racer]

I have a 1990 and have never had either of the rear caliper bolts loosen or break. I understand folks have the bolts loosen, but shear 3 times in one year.

Same caliper?  .350 inch/9mm bolt. What do you torque the bolt to? No notes in FSM for tighten torque spec. Is someone over tightening the bolt, and that's the issue? Only throwing out a potential for causing the issue.

[wreckerboy]

Thanks to dire warnings on this website about this I checked the pins on my 1.6 the other day. These are the same brackets that have been on the car since it was built in May of '89 (I'm the second owner). I've never had a pin loosen up, and I did change the pins out due to galling a few years ago. Pins are tight, but I took them apart, cleaned and Loctited them, thus guaranteeing they will now become a maintenance nightmare.

[Todd Green]

I have a 1990 and have never had either of the rear caliper bolts loosen or break. I understand folks have the bolts loosen, but shear 3 times in one year.

Same caliper?  .350 inch/9mm bolt. What do you torque the bolt to? No notes in FSM for tighten torque spec. Is someone over tightening the bolt, and that's the issue? Only throwing out a potential for causing the issue.

Doh, meant to say the caliper was replaced, not rebuilt.  They are allen heads, so I just use a key and don't put much torque on it.  The replacement bolt I just put in (Raybestos from RockAuto, the others were Mazda parts) already had some red paste on it, so I didn't add loctite. We'll see how long it lasts.  This last caliper that broke came with the bracket and pin so who knows what the torque was.

 

It's probably a combination of slamming through the Attitudes (imagine Laguna Seca Corkscrew), crappy suspension, and bad bushings allowing flex.  But I was curious to see if others have had issues.  I'm going to raise the ride height this weekend (we have quite a bit of rubber in the front arches at the top from rubbing) and replace the worse bushing.  (I have to order others.)

[Neil O]

I've snapped several at summit point over the years.  In both a 1.8 & a 99.  I think the turn 10 rumble strips can loosen them up.  We now check them every day.

 

Not fun when they break...

[G-LOC Danny]

Three times in a year is pretty rare for sure.  If you like to ride on the bump stops, and you have some rough FIA curbing you continue to pound through, then I can see how you would break a guide pin.  It's not unheard of to break one every once in a while, but three times in a year....

 

I would go through everything and replace the bushings.  If all three pins snapped with the same caliper then I would replace that caliper right away and toss in the garbage.  My two cents. 

[Todd Green]

Thanks for the advice Danny.  Already replaced the caliper and broke a pin on the new caliper (that was the 3rd one/pin).  I've raised the ride height, replaced the worst bushing (upper one in the spindle) and the car will race this weekend with various drivers so we'll see what happens.

[Jspaid142]

Speak of the devil... I just had one fail on me at Summit Point this weekend going into Turn 1 at full speed and absolutely no brakes. Good thing that gravel trap works well.

I am now checking them thoroughly every race, and replacing every couple events.