Author Topic: Replacing Brake Rotor Bolts  (Read 1057 times)

Online Dirk_S

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Replacing Brake Rotor Bolts
« on: January 17, 2022, 10:25:41 AM »
When replacing brake rotor bolts, can any grade steel be used, or does the high torque and the hubís alloy threads dictate a certain softness/give for bolt threads?

The V7ís rotor bolts are a flange-head type, no recess in the rotor that I recall. The ham-fisted utilitarian wants to replace them with hex head bolts, knowing that rotor bolts can sometimes get stuck and strip their heads. Maybe external hex head style is overkill.

Regardless of head type, would stainless steel bolts be OK to use? Regardless of material, Iíll plan on using blue threadlocker.
« Last Edit: January 17, 2022, 10:43:03 AM by Dirk_S »
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Offline John A

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Re: Replacing Brake Rotor Bolts
« Reply #1 on: January 17, 2022, 12:21:39 PM »
Stainless Allen heads, property class 70 or better is ok . 80 is overkill but donít use 60
« Last Edit: January 17, 2022, 12:23:30 PM by John A »
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Offline John Croucher

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Re: Replacing Brake Rotor Bolts
« Reply #2 on: January 17, 2022, 01:49:20 PM »
Stainless Allen heads, property class 70 or better is ok . 80 is overkill but donít use 60

McMaster Carr is a good source. 

Offline Old Jock

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Re: Replacing Brake Rotor Bolts
« Reply #3 on: January 17, 2022, 02:28:01 PM »
The advice AFAIK is not to use stainless for disc rotor bolts due to the lower yield stress, and use either carbon steel (or titanium)

I've used stainless bolts for a long time in brake rotors and not experienced any problems but there are quite a few threads warning of dire consequences

Perhaps others know more than I do, but personally I wouldn't be worried about changing the head type as long as it covered the same area (or greater) on the rotor.

If the flanged heads use an Allen key, I find these bolts a PIA as they usually utilize one key size down from a normal cap screw of the same bolt thread so round off the hex a lot easier.

That said it's usually quite easy to remove them if they round off by cutting a slot into the domed head the use a small chisel (or old screwdriver) and whack the fastener with a small hammer to shock the screw out.

If you want to use a hex I'd just purchase flanged hex bolts instead

That's just my experience, there might be some engineering reason for the head type, but I'd guess it's more likely for cost/aesthetic reasons

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Re: Replacing Brake Rotor Bolts
« Reply #3 on: January 17, 2022, 02:28:01 PM »

Online Dirk_S

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Re: Replacing Brake Rotor Bolts
« Reply #4 on: January 17, 2022, 04:20:12 PM »
Just for clarity, the V7 uses flanged external hex head, not a socket cap (Allen). My Uralís rotors used socket caps, and it freaked me out when trying to remove them and found the mating to be corroded. Went through 3 different Allen wrenches before I found one tough enough to break the corrosive bond. I was thinking that the flanged hex might simply be more aesthetically pleasing over a bulky looking, larger diameter standard hex head bolt.

There could be some type of clearance issue, but that side on both wheels also has the ABS sensor wheel attached and sticking farther out.

Another thought that came to mind is that perhaps a smaller head is correlative to the amount of torque that bolt is specified for. Smaller head = donít overdo it, dummy.

I have to spend some time learning more about steel / bolt grades.
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Online Mike Tashjian

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Re: Replacing Brake Rotor Bolts
« Reply #5 on: January 17, 2022, 04:53:07 PM »
I thought a propane torch was needed to soften the Locktite on some brake rotor bolts.  I think 450 degrees was the temperature that you aim for.  And it really doesn't seem to bother the paint if you aim for the bolt head.   

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Re: Replacing Brake Rotor Bolts
« Reply #6 on: January 17, 2022, 06:38:10 PM »
The factory fasteners for brake discs are one time use. If Iím concerned about clamping under the head with a smaller diameter, I use AN 560 (5/16) aviation washers. I attempted to drill the heads on some property class 80 stainless Allen heads that I use for discs . I was using them elsewhere and needed to safety wire them so itís a simple task to drill them. Not so with class 80ís, even going up to a 40 (large)drill bit.  Iíll order some 70ís, they are roughly equivalent to a grade 5 and are at least soft enough to drill.
« Last Edit: January 18, 2022, 09:10:15 AM by John A »
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Offline rschrum

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Re: Replacing Brake Rotor Bolts
« Reply #7 on: January 17, 2022, 06:50:40 PM »
I like the titanium offerings from ProBolt.
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Offline John A

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Re: Replacing Brake Rotor Bolts
« Reply #8 on: January 18, 2022, 09:20:58 AM »
Metric stainless has a different marking and specs system. It goes like this: 40 is soft, 70 and 80. similar to SAE grades 2,5,8
https://www.fastenal.com/en/76/metric-system-and-specifications
« Last Edit: January 18, 2022, 09:31:17 AM by John A »
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Re: Replacing Brake Rotor Bolts
« Reply #9 on: January 19, 2022, 06:57:53 AM »
Appreciate all the replies!

I thought a propane torch was needed to soften the Locktite on some brake rotor bolts.  I think 450 degrees was the temperature that you aim for.  And it really doesn't seem to bother the paint if you aim for the bolt head.

I know red loctite is the type that requires heat, but the blue stuff usually pops off with a little extra twist. I'll have to check the service manual for what they recommend.

I'd caution you about using stainless for that purpose.  They are soft and not intended for high torque applications.

This is exactly why I asked the question, because I was thinking maybe softer bolts were better, otherwise why would so many factory manuals call for replacement if they could simply use harder, more brittle bolts with higher tensile strength.
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Offline Groover

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Re: Replacing Brake Rotor Bolts
« Reply #10 on: January 19, 2022, 07:26:44 AM »
I'd stick with the original type. I thought stainless was the answer, then I reverted everything back after I had a few cases of galling using SS. Happens with SS, especially in high torque areas. Low torque, maybe it's ok to use.


Just wanted to mention.


https://www.boltdepot.com/fastener-information/materials-and-grades/thread-galling.aspx



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Offline dxhall

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Re: Replacing Brake Rotor Bolts
« Reply #11 on: January 19, 2022, 08:53:49 AM »
Not sure I understand the need for high strength bolts in this application.  These arenít rod bolts, which are subject to tensile loads - theyíre rotor bolts, which are only loaded in shear.  Maybe our engineers can weigh in on this.  Wouldnít any bolt work in this application so long as it didnít come loose?

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Re: Replacing Brake Rotor Bolts
« Reply #12 on: January 19, 2022, 09:27:11 AM »
 To get past the galling issue,I use antisneeze on them with schnoor washers and use the correct torque. I check them at tire changes and never have found a loose one in hundreds of thousands of miles. If I was a manufacturer and had to ensure they would never come loose and never be checked during the life of the disc or risk a strong liability lawsuit by someone who has trouble operating a paper clip, Iíd lock tite them. Iíve had loctited rotor bolts pull threads even heated for removal. If Iím doing the work for someone else Iíll locktite them as well but for myself I prefer to use the antisneeze method if I have the choice but I recommend anyone else to use new factory fasteners and their retention methods.
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Re: Replacing Brake Rotor Bolts
« Reply #13 on: January 19, 2022, 12:39:53 PM »
To get past the galling issue,I use antisneeze on them with schnoor washers and use the correct torque. I check them at tire changes and never have found a loose one in hundreds of thousands of miles. If I was a manufacturer and had to ensure they would never come loose and never be checked during the life of the disc or risk a strong liability lawsuit by someone who has trouble operating a paper clip, Iíd lock tite them. Iíve had loctited rotor bolts pull threads even heated for removal. If Iím doing the work for someone else Iíll locktite them as well but for myself I prefer to use the antisneeze method if I have the choice but I recommend anyone else to use new factory fasteners and their retention methods.

John,
Isn't Loctite *supposed* to prevent galling since, in theory, it eliminates metal to metal contact? Not doubting your experience, just surprised it's never happened to me.  :laugh:

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Re: Replacing Brake Rotor Bolts
« Reply #14 on: January 19, 2022, 07:00:00 PM »
John,
Isn't Loctite *supposed* to prevent galling since, in theory, it eliminates metal to metal contact? Not doubting your experience, just surprised it's never happened to me.  :laugh:





Add a little corrosion next time and maybe you too can enjoy installing a thread insert in your favorite wheel  :evil:
« Last Edit: January 19, 2022, 09:59:20 PM by John A »
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Re: Replacing Brake Rotor Bolts
« Reply #15 on: January 19, 2022, 07:09:16 PM »
I remember reading how Russian Locktite was a saltwater dip before assembly. I am getting old.

Offline Tusayan

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Re: Replacing Brake Rotor Bolts
« Reply #16 on: January 19, 2022, 07:30:00 PM »
The reason many manufacturers use locktite on brake disc bolts is because they so often use weird button head screws (or low profile heads of some other sort) that canít be torqued properly.  I use socket head cap screws and anti-seize, have never used locktite over 30+ years and many bikes/disc replacements and never will.

The stress applied to brake disc bolts isnít that high, one of them would be plenty to carry the torque, stainless is fine but you may as well use good quality bolts so the heads donít round out easily someday.
« Last Edit: January 19, 2022, 07:33:52 PM by Tusayan »

Offline John A

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Re: Replacing Brake Rotor Bolts
« Reply #17 on: January 19, 2022, 08:02:14 PM »
I think the property class 80 stainless Allenís are about like 10.9 ferrous Allenís . Or maybe thatís class 100. They donít often round out but the 70ís donít either. I dislike those low head ones and would only use them for clearance issues, I canít think of a spot.
Edit :Maybe aerodynamic but I donít have anything fast enough, Iím disappointed to say.
« Last Edit: January 19, 2022, 11:04:21 PM by John A »
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Re: Replacing Brake Rotor Bolts
« Reply #18 on: January 20, 2022, 07:17:37 AM »
"I have never used locktite over 30+ years and many bikes/disc replacements and never will."
I haven't either. Fasteners should be designed to stay under stress and not back off. When I had my Harley I was constantly in fear of rounding out those stainless cap screws mainly due to that blue crap they put on everything. HD must buy it by 55 gal drums and fasteners by how they look and not by function.
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Online Mike Tashjian

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Re: Replacing Brake Rotor Bolts
« Reply #19 on: January 22, 2022, 08:41:05 AM »
I use Lock tight whenever I need it.  Just another tool in the box.  It works well for it's intended purpose as does other methods of nut and bolt retention.  A well stocked work bench should be able to take care of most jobs you are comfortable tackling.

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Re: Replacing Brake Rotor Bolts
« Reply #20 on: January 22, 2022, 09:11:42 AM »
I use Lock tight whenever I need it.  Just another tool in the box.  It works well for it's intended purpose as does other methods of nut and bolt retention.  A well stocked work bench should be able to take care of most jobs you are comfortable tackling.

Absolutely agree. Unfortunately, Iím a single dude living in a small apartment with no shed/garage to work on the bike during crummier weather. At least gifted enough to have off-street parking, so I have something to be thankful for :)

The materialist in me (MORE TOOLS!!) is constantly at struggle with the pragmatic (how often will you USE it?) and minimalist (any more tools, Dirk, and youíll have to sleep out on the porch). Hence why I choose to not buy the bearing puller mentioned in my Replacing Bearings thread.

This thread doesnít seem to have any unanimous consensus regarding bolt material Ď strength. I think Iíll spend some more time searching around. My thinking based off everyoneís comments tells me that flexible is better than brittle, weather resistance wins out above all, and that bolt head type really only needs to satisfy clearance. And I ride in winter here in New Hampshire, so perhaps the brine on the roads is a good enough threadlocker :D
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Re: Replacing Brake Rotor Bolts
« Reply #21 on: January 22, 2022, 03:43:18 PM »
Absolutely agree. Unfortunately, Iím a single dude living in a small apartment with no shed/garage to work on the bike during crummier weather. At least gifted enough to have off-street parking, so I have something to be thankful for :)

The materialist in me (MORE TOOLS!!) is constantly at struggle with the pragmatic (how often will you USE it?) and minimalist (any more tools, Dirk, and youíll have to sleep out on the porch). Hence why I choose to not buy the bearing puller mentioned in my Replacing Bearings thread.

This thread doesnít seem to have any unanimous consensus regarding bolt material Ď strength. I think Iíll spend some more time searching around. My thinking based off everyoneís comments tells me that flexible is better than brittle, weather resistance wins out above all, and that bolt head type really only needs to satisfy clearance. And I ride in winter here in New Hampshire, so perhaps the brine on the roads is a good enough threadlocker :D

If it's of any use to you all my bikes both road and track use grade5 titanium rotor bolts with a copper based lube and no loctite. In all the bikes I've worked on in 50 years from WSB's, race bikes at the IOM and road bikes I've never used loctite on rotor bolts and never had one come loose or fail, steel or Titanium.

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Offline Motormike

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Re: Replacing Brake Rotor Bolts
« Reply #22 on: January 23, 2022, 12:15:53 PM »
Speaking of thread lock, has anyone used a product called Vibra-Tite?      https://www.vibra-tite.com/
Since the product is non-hardening, it sounds to me like a more suitable product for many applications than traditional Locktight.



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Re: Replacing Brake Rotor Bolts
« Reply #23 on: January 23, 2022, 08:03:25 PM »
Speaking of thread lock, has anyone used a product called Vibra-Tite?      https://www.vibra-tite.com/
Since the product is non-hardening, it sounds to me like a more suitable product for many applications than traditional Locktight.



+1 on the vibra tite. Itís specified in some Enstrom helicopters in the maintenance manual. Donít recall on what but it is good stuff. Doesnít hurt plastics, generally.
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