jattgunman

iTrader: (1)

For some reason my car keeps breaking off the front caliper bolts! The first time it happened was to the front right and it was a pain in the *** to fix because all the threads are gone and retapping to a bigger size in cast iron SUCKS!!! and today on the highway I hear a huge clunk and whenever I hit the brake the caliper would twist into the wheel...So why does this keep happening?First the right and now the left

wssix99

iTrader: (5)

Where did you get your replacement caliper bolts? How did you torque them?

jattgunman

iTrader: (1)

They were the stock bolts that came with the SS...last time I changed the pads was welll over a year ago and im almost positive I checked them when I fixed the first sheared bolt..This car is at the point were its just all maintenance

wssix99

iTrader: (5)

So what was the "clunk" that just happened? Was it not another bolt?

leadfoot4

iTrader: (1)

IIRC, the spec is 25ft/lbs.

Major_Lee_Slow

iTrader: (1)

Which bolts broke? The bolts which attach the caliper to the caliper pins which are inserted into the caliper bracket, or the caliper mount bolts which attach the caliper and the caliper bracket to the upright?

Based on your description it sounds like the caliper bracket bolts ripped the threads out of caliper bracket (If I remember correctly the bolt threads into the caliper bracket in the front and the bolts thread into the axle brake bracket in the rear). If that's the case, throw away those brackets and buy two new ones as well as new bolts. Then torque the bolts to the proper spec.

Note the ft*lb spec in the GM shop manual for 98's is way to high and is actually wrong. I've always torqued mine to 75 ft lbs and never had a problem until this last year when the rear came loose. I corrected this by replacing all the brake fasteners on the front and the rear and blue loctited all of them in place. Mine came loose because I had cycled the bolts on and off too many times over the years.

Conservative thinking should always take precedent over cost savings when it comes to brake repair. If a part fails once replace it, don't band-aid it. Also bear in mind that there is a possibility the corresponding part on the other wheel may also experience that same failure, so be preventative and replace that one as well.

jattgunman

iTrader: (1)

The clunk was the bolt falling off the car and hitting somewhere under the vehicle.. The two main bolts that hold the caliper to the spindle are the one that keep breaking themselves loose...ideally I would like to replace both the calipers plus the spindle that the rotor sits on

00 Trans Ram

iTrader: (5)

Happened to me about 4 years ago. 3 times in 6 months. I took the stock bolt to a shop that sells only bolts and bought brand new, Grade 8 bolts. Torqued them all to spec. Never had a problem since, even though I've been road racing with them for 2 years now.

Major_Lee_Slow

iTrader: (1)

Your in luck, it is how I remembered. The bolt passes through the upright and threads into the caliper bracket. (One benefit of having the car's suspension half way torn apart it's easy to confirm things like this)

Go ahead and buy new caliper brackets, caliper bracket bolts, Caliper Guide pins and Caliper Guide pin bolts all from your local dealer or GMpartsdirect. Install all bolts to the proper torque spec and you will not have any more problems with this issue.

If you need new hubs (the thing the brake disk attaches to) you can pick up a set from autozone. They sell the Timkins where are made by Delphi. Delphi was/is the OE supplier for GM for this part. Other people have had luck with other brands. Unfortunately for you, Autozone raised their price by $30/hub within the last couple of months.

All brands of hubs wear out almost immediately for me, but I autocross the car, and an Autozone is within 5 miles of my house and they always have two in stock ready for my warranty exchange. Although I have high hopes for the latest two I just received because they are from a newer lot and I learned that there was a quality issue with the lots that have a date code which starts with 6. If you are just street driving your car, you'll be fine and you'll have nothing to worry about.

wssix99

iTrader: (5)

For the bolts that attach the bracket to the spindle, 25 isn't tight enough. If I recall correctly, the factory manual for my '99 calls for something close to the 75 that Major Lee points out above.

The bolts need to be at the proper torque in order to stretch the bolt and develop the proper force/friction on the threads. (So it doesn't come out.) If the bolt is properly torqued and it won't stay put, (locktite is not necessary for these bolts if they are in good shape) then the bolt is permanently stretched out because it has started to fail. (And thus will not develop the proper friction on the threads.) If you have failed bolts, they will be succeptible to vibrating out or shearing under load.

If you are not the original owner of the vehicle, I'd echo Major Lee's suggestion to buy new bolts/hardware. (You can't get the correct high-strength bolts from a hardware store! You'll have to go to the dealer, most likely.) If you are torquing properly and the bolts are failing in normal driving, then a previous owner may have overtorqued the bolts or caused them to fail in some other way.

leadfoot4

iTrader: (1)

I was referring to the bolts (pins) that attach the caliper to the brackets, when I mentioned the 25 ft/lbs number.

jattgunman

iTrader: (1)

Thanks for all the help guys..I know I should of done it the right way by changing all the parts for new ones, but I decided to just tap the holes to a little bigger bolt size seeing that I have never track raced or autocrossed im hoping that everything will hold up fine..

wssix99

iTrader: (5)

The bolts that secure the bracket to the spindle are critical and need to be high-strength. If you do not use high strength bolts, your rig may not hold up and you could have a very dangerous situation. If you check the old bolts, they should have some lines and letters/numbers stapmed in to the head. (That stamping corresponds to the grade of the bolts.) You should make sure the new ones are the same grade of bolt to be safe.

wht01ws6ta

iTrader: (45)

If you need hubs I found the Timkins at O'Reilly for $113 which was a lot cheaper than AutoZone or Advanced.

+3 on making sure you're using grade 8 or 10.9 bolts to hold your brakes on!

Major_Lee_Slow

iTrader: (1)

I'd only replace these bolts with OE bolts because they are safety critical. Don't even think about buying some hardware specials. Plus the OE bolts come with the OE adhesive patch already applied to the treads.

chupr0kabra

iTrader: (10)

Does anyone have a part number for the bolts in question? I am looking for the ones that attach the caliper brackets to the backing plates in the rear. I called my local dealership and they ordered them, but when I got there, they handed me the bolts that thread into the sliders. The guy at the counter and I spent about 30 minutes looking at every exploded view he had and NONE of them showed these bolts. They're the last parts I need to get my car back on the road.


Thanks,

-Mike

Major_Lee_Slow

iTrader: (1)

Oh man, I'm sorry, I didn't record the part number the last time I bought them I wish I did because the parts guy and I had to search like crazy to find them.

wht01ws6ta

iTrader: (45)

I could at least find out the size and thread pitch and I think I have a set of those bolts from my 10 bolt if you want them. I would have to go out and check... If you're just after the part number I don't have that.

wht01ws6ta

iTrader: (45)

They are M12x1.75 and 35 mm long and they are 10.9 hardness of course. The head is flanged like this:

I don't have any spare but maybe check out a Fastenal local to you and they may have them or may not but they can definitely order them since you have the correct size and hardness.

jattgunman

iTrader: (1)

Dont worry I made sure the bolts I used are a grade 8 plus I used red loctite