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Failed Motolight bolt on brake caliper


bakerzdosen

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bakerzdosen

Because this isn't necessarily Hexhead specific, I figured I'd post here. If it is... well better applied there, feel free to place it there...

 

Tonight I replaced my tires. Rear tire went fine (other than breaking the tip off my Wiko bar frown.gif ). The front tire went fine as well... until I put it back on. I was tightening (torquing) the brake calipers down (for those of you who don't know caliper mount motolights replace the top bolt with their own) and I felt something give. I then tried to back out the bolt, but the thing just snapped off. Now, this presents two problems:

 

1) Is this Motolights' issue?

2) How to fix it.

 

I'll get to #1 in a second. I'm thinking that I can get it the 40ish miles to my local shop by tying or removing the now free-hanging left motolight. Would you guys risk (since I have no easy way of trailering the bike there) riding 40 miles with one good caliper and one caliper that's only bolted with one bolt? It seems pretty benign to me, but I just wanted to ask.

 

I'm thinking this is gonna be a nasty (and pricey) repair that I don't want to deal with. Since this is a motolight part that is less than a year old (dealer installed), should I pursue this with them or not? I'm hoping that this isn't the case, but unless it can be drilled out, I'm guessing the whole caliper is going to have to be replaced.

 

Suggestions?

 

(Planned course of action unless I get other suggestions: Call shop tomorrow to get an appointment and ask them about (they carry motolights too) Motolights "covering" something like this.)

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So your saying you need a new bolt?

 

3 dollars at the most for bolt that and getting out the broken part should only take a few minutes.

 

A local shop can take out the broken part if you can't. They dont't need to be a motorcycle shop either just have simple extraction tools. It will most likely come out very easily since you just had it off. It's just broken in there not frozen.

 

A nice guy shop can do it for free or cheap if you just buddy talk to them.

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bakerzdosen

OK, I suppose I should mention that it's gonna take a LOT of torque to get that out (think 30+ NM). It IS frozen in there - the Motolight was still a bit loose and I was close to the suggested torque value (30 NM) of the bolt. I think it was rusted somehow as the other side showed signs of rust as well. Is that possible if the bolt is drilled out? Obviously I don't know much about bolt extraction in cases such as this.

 

Also, if it is possible, where should I look for a local "shop" to do that? Just a local auto mechanic?

 

I'm cool with paying someone to do that, so "free" isn't that big of a deal.

 

(And I find it ironic that the first reply is from Tony as you've proven that one CAN ride on one brake caliper for a bit if needed. smile.gif )

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HA ha! Yes sir,

Local shop with a drill and easy out is all that should be needed. There are several ways to get a broken bolt out. A good shop knows them all!

 

Some of the best shops to do this are guys that work on old cars. They are familiar with adversity.

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bakerzdosen

Thanks Tony. Info like that is why I post here before doing anything... Someone always knows more than me here.

 

(Next up, my post on boxers... or briefs. tongue.gif )

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ISFA riding it that way, I suspect you will be fine. Is the bolt broken at a point where what is left will still prevent a rotation of the caliper? If so in particular, th other bolt should hold it in place for a short bit.

 

There are a lot of Motolight installations in place, and this is the first I've ever heard of a bolt breaking. And 30 nm isn't really that much torque. Any chance your torque wrench is out of calibration? wink.gif Or you just got the luck of the draw and a bad bolt. Happens I suppose.

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OK, I suppose I should mention that it's gonna take a LOT of torque to get that out (think 30+ NM). It IS frozen in there

confused.gifconfused.gif

 

If the head sheared off then there should not be any torque on the threads.

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James Clark
OK, I suppose I should mention that it's gonna take a LOT of torque to get that out (think 30+ NM). It IS frozen in there

confused.gifconfused.gif

 

If the head sheared off then there should not be any torque on the threads.

 

It sheared while backing out. The threads are galled.

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OK, I suppose I should mention that it's gonna take a LOT of torque to get that out (think 30+ NM). It IS frozen in there - the Motolight was still a bit loose and I was close to the suggested torque value (30 NM) of the bolt. I think it was rusted somehow as the other side showed signs of rust as well. Is that possible if the bolt is drilled out? Obviously I don't know much about bolt extraction in cases such as this.

 

IF you were close to the recommended torque (big if) and the light was still loose then the bolt was binding in the threads (or bottoming out if it is not a through-hole). It sounds like it would be best to learn more about the basics of how this works before working on something as critical as wheels and brakes.

I'm not trying to be critial of your abilities - Working on mechanical devices is far more difficult than most people think.

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bakerzdosen
It sheared while backing out. The threads are galled.
That's kind of what I was thinking.

 

So far, one shop has declined to work on a motorcycle ("My guys are all trained on BMW cars and I don't know how different brakes on a motorcycle would be. Try a motorcycle shop." eek.gif ) I'm waiting for a call back from our local BMW (Motorrad) mechanic.

 

The other thing I'm thinking is that if I can somehow get the wheel off with the one brake caliper still mounted, then I would be able to just pull the caliper off the fork and with the still protruding threads, I could just use a vice to twist the bolt out.

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bakerzdosen
IF you were close to the recommended torque (big if) and the light was still loose then the bolt was binding in the threads (or bottoming out if it is not a through-hole). It sounds like it would be best to learn more about the basics of how this works before working on something as critical as wheels and brakes.

I'm not trying to be critial of your abilities - Working on mechanical devices is far more difficult than most people think.

Well, I was really surprised that it was binding. If it was cross-threaded or mis-threaded, it would have showed up early on, not towards the end of the insertion. The BMW bolts were easy to take out while both of the Motolight bolts have always been tough to remove (in comparison).

 

And the motolight was loose, but there was friction there - meaning it was close to the point where I should have been torquing it down.

 

Maybe there is some magical secret to handling bolts that I'm missing here.

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Well, I was really surprised that it was binding. If it was cross-threaded or mis-threaded, it would have showed up early on, not towards the end of the insertion. The BMW bolts were easy to take out while both of the Motolight bolts have always been tough to remove (in comparison).

 

And the motolight was loose, but there was friction there - meaning it was close to the point where I should have been torquing it down.

 

Maybe there is some magical secret to handling bolts that I'm missing here.

A couple of pieces of info:

 

It is correct that crossthread would bind almost instantly.

 

If the threads are OK then you should be able to screw the bolt in with your fingers or a very small wrench - lets say way less than 1 lb/ft. Make sure that it is not bottoming, binding or hitting a damaged part just about the time it would normally remove all clearance from whatever you are tightening. When in doubt, make sure it is free past that point by removing a washer under the bolt head or a part and make sure it is still able to be done with finger force. If there is rust/corrosion, clean it up with a wire brush or a tap.

 

I am quite concerned that the Motolight bolts were more difficult to take out than the original bolts. Perhaps they were damaged the last time? BTW, any bolt that has any sign of stretching is junk.

 

I'm not quite clear on how loose the Motolight was when the bolt started to get tight. I was thinking that there was clearance there that you could feel. Perhaps it just could be moved by hand rotationally? If there was "friction there" then perhaps this was fine and I drew a different conclusion from the first post. This is really tough with verbal descriptions. Not exactly easy even in-person.

 

Not "magic" on bolts, just not as simple as most people think it is. FWIW: One of the business I own sells parts for expensive european cars. Not a single week goes by without someone buying oil drain plugs, wheel studs, wheel nuts, etc. that were destroyed due to overtightening. Most done by "professional" mechanics.

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bakerzdosen
A couple of pieces of info:

 

It is correct that crossthread would bind almost instantly.

 

If the threads are OK then you should be able to screw the bolt in with your fingers or a very small wrench - lets say way less than 1 lb/ft. Make sure that it is not bottoming, binding or hitting a damaged part just about the time it would normally remove all clearance from whatever you are tightening. When in doubt, make sure it is free past that point by removing a washer under the bolt head or a part and make sure it is still able to be done with finger force. If there is rust/corrosion, clean it up with a wire brush or a tap.

 

I am quite concerned that the Motolight bolts were more difficult to take out than the original bolts. Perhaps they were damaged the last time? BTW, any bolt that has any sign of stretching is junk.

 

I'm not quite clear on how loose the Motolight was when the bolt started to get tight. I was thinking that there was clearance there that you could feel. Perhaps it just could be moved by hand rotationally? If there was "friction there" then perhaps this was fine and I drew a different conclusion from the first post. This is really tough with verbal descriptions. Not exactly easy even in-person.

 

Not "magic" on bolts, just not as simple as most people think it is. FWIW: One of the business I own sells parts for expensive european cars. Not a single week goes by without someone buying oil drain plugs, wheel studs, wheel nuts, etc. that were destroyed due to overtightening. Most done by "professional" mechanics.

Once loosened slightly, the original bolts can indeed be removed by hand. However, the motolight ones have always needed to be loosened the entire way using some sort of "aid" - be it a socket wrench or my t-handle allen wrench. I don't know how they went in initially as the dealer put them on. However, the bolts have never "moved" with just 1 lb/ft of force when in the threads.

 

I have to admit, I wasn't really thinking "how much torque am I putting on this socket wrench" when installing the bolt. It felt just like the other side did until it started showing signs of stronger resistance. At that point, I swapped it out for the torque wrench and started using that. That's where things were a bit different. It took more rotation to get to the point where there seemed to be friction (enough to hold the light steady once aligned). I then started looking more intently at the torque value. (It hadn't gone over 30NM to this point.)

 

And yes, I should have cleaned the rust. That was a mistake on my part. And I've definitely overtightened bolts before, but I'm pretty sure that wasn't the case here.

 

Anyway, I may just "punt" here after all. I have an appointment next week at the local shop, so if I can't get the bolt out on my own, I'll just let them deal with it. I'll have them replace both bolts.

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What's keeping you from getting some reverse drill bits, an extractor and a tap ( to chase the threads and clean them up after you extract the snapped bolt )

 

BTW, a Dremel with a grinding head will grind extractor if you snap it off. DAMHIK.

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bakerzdosen

So, I just thought I'd post an update.

 

The other side was nearly seized/galled as well. The motolight bolts are stainless steel and as they are being used with Aluminum calipers, that's not a good combination without using some sort of anti-seize. So, I'm out probably $500 for what was originally a dealer error (but since I didn't know, I perpetuated the error by not putting any on last time I changed the tires.) The one caliper will probably have to be heli-coiled and the other is going to have to be EDM drilled (two week backlog). Not fun.

 

I've finally been bitten by their service dept (I was the last person I knew of that hadn't).

 

I'm just at a loss why the bolts were stainless to begin with.

 

Live and learn.

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Well stainless is perceived as "better" by many folks and in many cases may well be..... until something like what happened to you comes about.

ugh bncry.gif

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Thanks for posting your update. How long were your Motolights on your bike? I just installed mine last month. I'll have to check them because I don't believe I put anti-seize on the caliper bolts when I installed my lights. I know I used it on some of the connectors, but I think I forgot the caliper bolts (now that you mention it). crazy.gif So it sounds like the dissimilar metals (steel/aluminum) were subject to electrolytic corrosion, which is good information to know.

 

Sorry to hear of your misfortune.

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bakerzdosen
Thanks for posting your update. How long were your Motolights on your bike? I just installed mine last month. I'll have to check them because I don't believe I put anti-seize on the caliper bolts when I installed my lights. I know I used it on some of the connectors, but I think I forgot the caliper bolts (now that you mention it). crazy.gif So it sounds like the dissimilar metals (steel/aluminum) were subject to electrolytic corrosion, which is good information to know.
I had the motolights put on when I bought the bike early last July. The bike's seen 16k or so miles since and the bolts have been removed twice for tire changes and once for a brake bleed.

 

That's what I'm here for, a guinea pig. tongue.gif

 

Sorry to hear of your misfortune.
Not as sorry as I was... lmao.gifbncry.gif

 

Funny thing is that I've read on here many times about how using anti-seize on a torqued bolt is bad news, so the thought would have NEVER crossed my mind unless I'd read about this somewhere else (obviously that never happened.)

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I just checked my wife's 03 GT & I don't think the Motolights supplied caliper bolts are stainless.

BMW does not put anti-seize on at the factory and I'm not convinced that the lack of it caused you any problems.

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The other side was nearly seized/galled as well. The motolight bolts are stainless steel and as they are being used with Aluminum calipers, that's not a good combination without using some sort of anti-seize.

 

I'm just at a loss why the bolts were stainless to begin with.

 

STAINLESS???? I doubt it. Caliper bolts are normally a high strength steel. I looked at the ones on my RT but they are marked with markings that I don't recognize but they have the "feel" of the high grade I would expect (harder to tell when they are not loose). I expect grade 10.9 or 12.9. The best quality stainless bolts, grade 80, are much lower strength, about 30% less than a 10.9, as I recall. If they are substituting stainless for a high strength bolt on a caliper, they may have a big problem, even if using the best available material. I would just be amazed that a manufacturer would downgrade a caliper bolt to mount a light.

 

ALSO, stainless builds up a thin oxide coating, which is how it resists rusting. This gets sheared off when tightening a bolt and can result in galling. This makes stainless even less appropriate for something that is removed and replaced several times. Antiseize is SOP for anything stainless that needs to be tightened firmly. You generally use stainless in a corrosive environment like a boat where you need corrosion resistance and then just size up the hardware size to compensate for the strength lost.

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bakerzdosen
STAINLESS???? I doubt it. Caliper bolts are normally a high strength steel.
Well, I have no way to verify that. I just know what the repair shop told me (as I no longer have the bolts in my possession). They weren't shiny at all though. More of a dull gray.

 

And for the record, I can only "assume" that the bolt was provided by Motolights. BMW of SLC did the install, but they seemed to be as described.

 

But yeah, high strength steel sounds more like what I remember from them. However, they were (although they were longer) lighter in feel/weight. Motolight.com says that they come with a "supplied zinc plated, grade 12.9 socket head cap bolt." Someone is wrong here, but it probably isn't me as I'm just the messenger... smile.gif (I'm also the poor schmuck who gets to pay for it.)

 

OK metallurgy experts, assuming it was a "zinc plated, grade 12.9 socket head cap bolt", would one want to use anti-seize? If not, how did the things corrode so quickly? What should I have done differently? It's not like the instructions said to do anything differently than I did. I must have done something right as the BMW supplied bolts were fine and BOTH motolight bolts corroded, galled and failed.

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ShovelStrokeEd

Do you still have the head of the bolt? Grade 12.9 fasteners can be identified by markings on the head. One or two dots or a small circle, as I recall.

 

Stainless would certainly be inappropriate for this application, reasons already mentioned.

 

I'm not sure that zinc would be a good idea. You would then have zinc and aluminum in contact, two highly reactive metals that would tend to bond to each other. A cadmium plated fastener would have been a better choice if appearance was a factor. Black oxide coating is the norm for these high strength fasteners and that is what I would have used.

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bakerzdosen

Do you still have the head of the bolt? Grade 12.9 fasteners can be identified by markings on the head. One or two dots or a small circle, as I recall.

 

I had it on me when I dropped the bike off and showed it to them. The mechanic kinda "oh'd" and "aw'd" over it, but I left it there. I'll ask if they've still got it so I can look.

 

Stainless would certainly be inappropriate for this application, reasons already mentioned.

 

I'm guessing (now that you all have slapped me back to reality and I'm not just blindly agreeing with the shop mechanic) that he just noticed that it reacted badly with the Al and then just ran to what he knew: Al and Stainless don't play nice together.

 

 

I'm not sure that zinc would be a good idea. You would then have zinc and aluminum in contact, two highly reactive metals that would tend to bond to each other. A cadmium plated fastener would have been a better choice if appearance was a factor. Black oxide coating is the norm for these high strength fasteners and that is what I would have used.

 

Appearance isn't that big of a factor. Function (to me) is all that matters here. And whatever it is (assuming zinc at this point after your response,) that came in contact with the aluminum, it reacted in a very undesirable way.

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The bolts that Motolight supplies with their lights are not stainless.

 

This whole think smells. Either the original installer used the wrong bolts, just grabbed something, and/or grossly overtightened them. In 100s and 100s of caliper mounted Motolight installations that are out there, I've never heard of this issue.

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Jim VonBaden
I just checked my wife's 03 GT & I don't think the Motolights supplied caliper bolts are stainless.

BMW does not put anti-seize on at the factory and I'm not convinced that the lack of it caused you any problems.

 

I agree that the bolts are not likely the problem. I have removed and installed dozens of Motolights with the supplied bolts (Stainless? Probably not), with no issues yet with any I have done.

 

I would not put anti-seize on a bolt not speced for anti-seize.

 

Jim cool.gif

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OK metallurgy experts, assuming it was a "zinc plated, grade 12.9 socket head cap bolt", would one want to use anti-seize?

 

I'm not a metallurgy expert.

 

BUT- if you are going to use anti-seize on a bolt that has a torque spec calling for a clean dry bolt, you will have to modify the torque spec a little or a lot (depending on the anti-seize) to get the correct bolt tension.

 

As an example:

 

bolt torque modification multiplier

 

Clean dry bolt 1.00

motor oil (20w) 0.80

molybdenum film (dry) 0.60

Never-Seize brand anti seize: 0.45

 

 

This is to say w/ a torque spec of 100 ft-lbs, if you use Never-Seize, you should set your wrench to 45 ft-lbs because the lubrication properties of the anti-seize allow the bolt to turn much more easily in the threads, and the bolt has the same tension at 45 ft-lbs as it had at 100 ft-lbs dry. If you used 100 ft-lbs with anti-seize you could over tension, overstretch or break the bolt.

 

 

 

This information comes from the Pocket Ref book by Thomas J. Glover - a handy little guide to all sorts of useful information. You can get it at that huge internet bookstore place for around $15. Good tables of info on fasteners. I have no affiliation.

 

 

PS: BMW of SLC? RUN AWAY!

 

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I seem to recall the Motolight installation instructions did not call for putting anti-seize on the caliper bolts. They ship a small packet of anti-seize with the lights. I'll have to find the installation instructions and verify my recollection. grin.gif

 

I did pull one of the bolts on my lights last night and I hadn't used anti-seize when installing the caliper bolts (and atypically I did follow the instructions). wink.gif

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bakerzdosen

Well, just FYI, I called motolights (now that I'm pretty much calm about the situation). I'm still waiting for a call back from their tech, but the bolts they supply are apparently zinc coated stainless bolts (according to the first person I talked to there. She said that they've never heard of a case like this (not surprisingly). The more I think about it, the more odd that sounds, but I'll ask more questions when I talk to their tech.

 

Regardless, motolight does not recommend using anti-seize.

 

I just didn't want to start a panic on the matter. I know this is atypical for them.

 

I'll post more when I talk to the tech.

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...but I'll ask more questions when I talk to their tech.

 

Regardless, motolight does not recommend using anti-seize....I just didn't want to start a panic on the matter...

I'll post more when I talk to the tech.

 

Good idea. Thanks again for sharing the information. wave.gif

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bakerzdosen

Well, I talked to the tech. Long story short: He doesn't have a clue what would have caused it either. If he had the caliper/bolt in front of him, he could tell... Regardless, he'd never heard of such a thing, but questioned if the dealer had put the correct threads in the caliper to begin with.

 

He said the zinc could eventually corrode to the caliper, but that would take 6 months of sitting near the ocean, not Utah desert-like climate. He'd never heard of a single bolt failing like that and that loctite isn't necessary if you're going to be removing the bolts once a year anyway. It shouldn't cause things to freeze like mine did.

 

Regardless, he didn't know how it could have been caused (other than a dealer mistake), so I'm no closer to a resolution than before. I'll just put new bolts in and go from there I guess. frown.gif

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