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Front brake pad install (overheated bolts ?)

2K views 6 replies 5 participants last post by  The Astute Reader(tm) 
#1 ·
I just changed my worn front brake pads on my '06 Wing. I have 45,000 miles and the right pads were worn to near the minimum, but the left side was worn to almost the metal. I understand this is normal for the left side to wear more. I have something I'd like to share with others who may change their brakes. On the right caliper are two mounting bolts, 12 mm wrench size. The torque on these bolts are 23 ft. lbs. I have a good ( I think ) torque wrench and tightened the top bolt to spec, but the bottom bolt wouldn't set off the torque wrench click. It seemed to just slowly turn like it was stripped or something. I am not that big a klutz to just snap a bolt off but the damn thing just broke in two. So now I have to get it out, luckily enough thread was showing. I examine that bolt and also removed the top bolt to compare them. They look stretched ( from heat? ). My thinking is that they were stressed from heat, the calipers do get quite hot. I went to the Honda shop and they didn't have the right bolts. I put some bolts in from my spare parts box but I won't ride the bike until I get the right bolts. I am afraid the heat may crack a weaker bolt. I just want to say that in the future I will always put in two new bolts on the right caliper when I change the brake pads. Any comments please? Thank you.
 
#2 ·
Honda makes those bolts soft and advises you to replace them after one use. Rotor bolts are the same, soft and will break off easily.
 
#3 ·
Honda makes those bolts soft and advises you to replace them after one use. Rotor bolts are the same, soft and will break off easily.
I went back and read the manual, Honda does say to replace the bolts each time. So many manuals say that ( replace with new bolts ) that I guess I just read right past that and didn't retain it. In this case it is certainly important. This was the first time I replaced my brake pads, however I have taken the right caliper off many times to remove the front wheel. Each time I used my torque wrench to tighten the bolts. I might add that yesterday I had my torque wrench checked and it is right on. Thanks for the reply John.
 
#4 ·
It is interesting to me that at one time bolts were built to be reused a few times.

Todays bolts must be replaced after one use in more and more applications. Did engineers forget how to build - design a quality bolt?

I swapped out a flywheel on a 2006 VW Jetta. The bell housing bolts were spec'd out for replacement after one use.
 
#5 ·
It is interesting to me that at one time bolts were built to be reused a few times.

Todays bolts must be replaced after one use in more and more applications. Did engineers forget how to build - design a quality bolt?

I swapped out a flywheel on a 2006 VW Jetta. The bell housing bolts were spec'd out for replacement after one use.
Tony, I don't know for sure but I have a theory on maybe why the Honda bolt is soft. The caliper mount female threads are in aluminum, maybe it was designed for an overtightened bolt to fail rather than the thread. When I felt the bolt slip I said a four letter word thinking I stripped the thread, I was relieved to see I only broke the bolt instead of the $190.00 caliper mount. A tempered steel bolt could certainly be made for this application but there must be a reason...unknown to me. I'm just a throttle jockey.
 
#6 ·
It is interesting to me that at one time bolts were built to be reused a few times.

Todays bolts must be replaced after one use in more and more applications. Did engineers forget how to build - design a quality bolt?
It would seem on the surface that they are being cheap, but it is actually the lightweight, soft aluminum used today that requires bolts of this type.

Years ago, when everything was heavy cast iron, it was not only strong, but fairly stable at higher temperatures. You could use high strength bolts and crank the ***** of of them.

But aluminum and other lightweight metals have a problem. It expands a great deal when it heats up. That bolt you crank down to 23 ft-lbs has an equivalent torque much higher than that when the caliper heats up. If you used a hardened bolt, it wouldn't stretch, and the threads could get damaged.

Since the bolts are steel, once they stretch, they stay stretched. If you try and re-install them, they stretch even further the first time the caliper heats up. Eventually the bolt can snap, and it may not happen during installation.

I have never seen this requirement for a caliper before, only on engines. And its not like they are being torqued very tight. But then again, cars still use cast iron calipers, not the lightweight aluminum ones that bikes use.

I'm glad I saw this topic. Next time I do my brakes I think I will order new caliper bolts. Thanks for bringing it up.

BTW, it wasn't heat that damaged the bolt directly. Anything hot enough to take the temper out of a bolt would boil the brake fluid.
 
#7 ·
It is interesting to me that at one time bolts were built to be reused a few times.

Todays bolts must be replaced after one use in more and more applications. Did engineers forget how to build - design a quality bolt?

I swapped out a flywheel on a 2006 VW Jetta. The bell housing bolts were spec'd out for replacement after one use.
No, they didn't forget anything. In fact, they remembered something - that almost no one in the automotive and motorcycle industry is going to bother keeping a log of life-limited components as is done on aircraft and spacecraft. That leaves exactly two choices: design the connection for an infinite service life, which will be bigger and heavier, or specify a one-shot service life for the fastener.

In the past several months, there have been at least a dozen posts in this forum that reveal widespread use of poor maintenance techniques and scant knowledge of how a bolted connection is supposed to work.

Given the extreme lack of appreciation for our efforts, we engineers would almost be perfectly happy to let you find out where you went wrong the hard way. Except, of course, that your estate would try to sue us for not warning you, even though you habitually ignore what we tell you.
 
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