How to safely replace a brake bolt?
04-18-17, 09:15 AM
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How to safely replace a brake bolt?
I got new center pull brakes, the Velo Orange distributed Gran Compe 610:
Dia-Compe 610 Centerpull Brake
But they come with recessed bolts, and my frame is vintage. Ive been using them with the recessed bolts for a while now anyways, but I want a cleaner solution. I can easily just get new bolts, but I'm a bit worried about the strength of the material.
I can't find online what the GC610 mounting bolts are made of, I assume stainless steel or something? It probably would not be wise to replace this with a zinc bolt from a hardware store, correct?
Where can I find something that might be safe to replace with?
FYI: These bolts dont work exactly like other recessed bolts. It comes with no recessed nut. It is literally just a bolt that goes into a threaded hole on the back of the brake body. It looks like this
https://imgur.com/Mr1Rprj
https://imgur.com/uqjSfpb
All I want to do is replace it with a similar bolt that doesn't have that little recessed bit under the head, like this
Plus I need it to be a bit longer, so the benefit will be twofold.
Do I have to be careful? Or can I just go get a standard zinc bolt from the store?
Dia-Compe 610 Centerpull Brake
But they come with recessed bolts, and my frame is vintage. Ive been using them with the recessed bolts for a while now anyways, but I want a cleaner solution. I can easily just get new bolts, but I'm a bit worried about the strength of the material.
I can't find online what the GC610 mounting bolts are made of, I assume stainless steel or something? It probably would not be wise to replace this with a zinc bolt from a hardware store, correct?
Where can I find something that might be safe to replace with?
FYI: These bolts dont work exactly like other recessed bolts. It comes with no recessed nut. It is literally just a bolt that goes into a threaded hole on the back of the brake body. It looks like this
https://imgur.com/Mr1Rprj
https://imgur.com/uqjSfpb
All I want to do is replace it with a similar bolt that doesn't have that little recessed bit under the head, like this
Plus I need it to be a bit longer, so the benefit will be twofold.
Do I have to be careful? Or can I just go get a standard zinc bolt from the store?
Last edited by floyd0117; 04-18-17 at 09:20 AM.
04-18-17, 09:33 AM
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That is a standard allen head bolt- available at many hardware stores. You can use stainless if you like, but it isn't necessary, nor is there anything magical about the fasteners on a bike that would require you to get them from a bike shop.
04-18-17, 09:40 AM
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If i'm thinking of this correctly, the recessed bolt that came as standard is causing cosmetic issues at the point it meets the frame?
The picture you had up there looks like a chromoly steel bolt, which are quite common, much more than Alum or Zinc, depending in what field you're looking for.
You could shop online for bolts that have the same thread size as your stock bolt. Looks like an M6 type bolt here.
I haven't seen bolts quite like that, with the secondary flat-faced countersunk head, I'm starting to believe it's for mounting of mudguards at the front fork on more quirky designed forks. (or just some weird generic bolt?)
I will say, in terms of length -- it is not important as long as there is atleast 12mm+ of engaged thread, you won't strip that out for the life of you.
However, you don't want anything longer than the stock bolts because then you risk bottoming out while torquing up and stripping the threads off, but realistically you could buy a bigger bolt and cut it to size with relative ease. - Additional note; Bolts that are made up to that size are typically met up to a strength standard anyway, so the chance of that bolt being made of some cheap weak material is rare at best.
The picture you had up there looks like a chromoly steel bolt, which are quite common, much more than Alum or Zinc, depending in what field you're looking for.
You could shop online for bolts that have the same thread size as your stock bolt. Looks like an M6 type bolt here.
I haven't seen bolts quite like that, with the secondary flat-faced countersunk head, I'm starting to believe it's for mounting of mudguards at the front fork on more quirky designed forks. (or just some weird generic bolt?)
I will say, in terms of length -- it is not important as long as there is atleast 12mm+ of engaged thread, you won't strip that out for the life of you.
However, you don't want anything longer than the stock bolts because then you risk bottoming out while torquing up and stripping the threads off, but realistically you could buy a bigger bolt and cut it to size with relative ease. - Additional note; Bolts that are made up to that size are typically met up to a strength standard anyway, so the chance of that bolt being made of some cheap weak material is rare at best.
Last edited by bazooka115; 04-18-17 at 09:49 AM.
04-18-17, 09:40 AM
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Of course, I know all of that, I just didn't know if I should be using a stronger material than typically offered. But thank you!
04-18-17, 02:05 PM
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There are many grades of bolts. What you buy at Home Depot may be a good bolt, or it may be a poor one. Ideally, they'd offer ASTM 574 type socket headed cap screws (SHCS). If not, I'd look for an SAE J429 "Grade 8" SHCS.
IF the original part is stainless, you could try a stainless SHCS. Stainless bolts are (generally) not as strong or fatigue resistant as high-strength steel alloys. So if the original part is plated alloy (that is, non-stainless) steel, I'd stick with steel.
IF the original part is stainless, you could try a stainless SHCS. Stainless bolts are (generally) not as strong or fatigue resistant as high-strength steel alloys. So if the original part is plated alloy (that is, non-stainless) steel, I'd stick with steel.
04-18-17, 02:23 PM
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There are many grades of bolts. What you buy at Home Depot may be a good bolt, or it may be a poor one. Ideally, they'd offer ASTM 574 type socket headed cap screws (SHCS). If not, I'd look for an SAE J429 "Grade 8" SHCS.
IF the original part is stainless, you could try a stainless SHCS. Stainless bolts are (generally) not as strong or fatigue resistant as high-strength steel alloys. So if the original part is plated alloy (that is, non-stainless) steel, I'd stick with steel.
IF the original part is stainless, you could try a stainless SHCS. Stainless bolts are (generally) not as strong or fatigue resistant as high-strength steel alloys. So if the original part is plated alloy (that is, non-stainless) steel, I'd stick with steel.
Most Home Depot stuff is grade 2. My local True Value offers grade 2 and grade 5 as well as 8.
A grade 2 bolt is fine for virtually any bicycle application with a yield strength of 57K psi. A grade 8 is money wasted. I personally usually use stainless and most hardware store ones are 18-8 302 or 304
It's a bike - virtually no fasteners on it are under any real stress that would require anything other than a common nut or bolt other than maybe in the BB.
04-18-17, 02:53 PM
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04-18-17, 03:38 PM
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04-18-17, 03:39 PM
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Most Home Depot stuff is grade 2. My local True Value offers grade 2 and grade 5 as well as 8.
A grade 2 bolt is fine for virtually any bicycle application with a yield strength of 57K psi. A grade 8 is money wasted. I personally usually use stainless and most hardware store ones are 18-8 302 or 304
It's a bike - virtually no fasteners on it are under any real stress that would require anything other than a common nut or bolt other than maybe in the BB.
A grade 2 bolt is fine for virtually any bicycle application with a yield strength of 57K psi. A grade 8 is money wasted. I personally usually use stainless and most hardware store ones are 18-8 302 or 304
It's a bike - virtually no fasteners on it are under any real stress that would require anything other than a common nut or bolt other than maybe in the BB.
04-18-17, 08:12 PM
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Antisieze or grease the bolt before install, especially the black steel variety. It will rust and sieze in place.
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04-19-17, 12:49 AM
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04-19-17, 01:58 AM
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Sounds like OP found a solution
but I'll offer this:
Drill out the backside-only of the mounting holes on you frame/fork to be a few mm larger than the frontsides; so they now work with the recessed bolts. (and recessed nuts common on other calipers)
but I'll offer this:
Drill out the backside-only of the mounting holes on you frame/fork to be a few mm larger than the frontsides; so they now work with the recessed bolts. (and recessed nuts common on other calipers)
04-19-17, 07:49 AM
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Drilling out the back of the fork crown is easy but the rear brake bridge is a bit trickier since the seattube prevents using a normal drill. I've clamped a short 5/16" drill bit sideways in a Vise-Grip and rotated it a fraction of a turn at a time to enlarge the hole.
04-19-17, 08:43 AM
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Most Home Depot stuff is grade 2. My local True Value offers grade 2 and grade 5 as well as 8.
A grade 2 bolt is fine for virtually any bicycle application with a yield strength of 57K psi. A grade 8 is money wasted. I personally usually use stainless and most hardware store ones are 18-8 302 or 304
A grade 2 bolt is fine for virtually any bicycle application with a yield strength of 57K psi. A grade 8 is money wasted. I personally usually use stainless and most hardware store ones are 18-8 302 or 304
* I can't believe how small are the screws holding the derailler hangers to the frame.
04-19-17, 01:48 PM
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good points. I agree, but i'm not sure how close to "grade 2" the hd bolts really are. The issues below are real:
So, to begin with you have a yield strength difference of 57ksi to 130ksi, then you have the fact that the "grade 2" bolts may in fact be "grade minus 1" (that is, they're crap and don't even meet the grade 2 specs).
i agree pretty much with that and rarely buy big box hardware. I've snapped off too many 1/4 -20 hex heads of that stuff tightening them. I mostly buy at the hardware store or fastenal.
for most bikes, yeah. For some of the ultralight bikes, i think that they're getting to the point of optimizing bolt size, so we may be creeping up on low design margins between service and yield. We are certainly at a point where service life is in the range exceeding fatigue limits*. Do i think you're right, that the op will have good luck with a stock bolt from the hd bin? Yup. But for one bolt, the "money wasted" is a matter of cents. I'd get the grade 8 bolt (which, as i've said, would itself not be good enough for some of the systems i've engineered - but that's a personal prejudice built up over time). well they did say they were putting new brakes on a vintage frame so i figured it was not some ultralight thing and it's a brake mounting bolt which shouldn't be stressed that much. Working in underground construction i'm a big fan of ss and use it almost exclusively on my bikes. I rarely use any grade 8 except in auto suspension, snow plow mounting, and known critical strength applications.
* i can't believe how small are the screws holding the derailler hangers to the frame. but you do want that to break rather than the dropout. I just wish they didn't have 500 different ones.
So, to begin with you have a yield strength difference of 57ksi to 130ksi, then you have the fact that the "grade 2" bolts may in fact be "grade minus 1" (that is, they're crap and don't even meet the grade 2 specs).
i agree pretty much with that and rarely buy big box hardware. I've snapped off too many 1/4 -20 hex heads of that stuff tightening them. I mostly buy at the hardware store or fastenal.
for most bikes, yeah. For some of the ultralight bikes, i think that they're getting to the point of optimizing bolt size, so we may be creeping up on low design margins between service and yield. We are certainly at a point where service life is in the range exceeding fatigue limits*. Do i think you're right, that the op will have good luck with a stock bolt from the hd bin? Yup. But for one bolt, the "money wasted" is a matter of cents. I'd get the grade 8 bolt (which, as i've said, would itself not be good enough for some of the systems i've engineered - but that's a personal prejudice built up over time). well they did say they were putting new brakes on a vintage frame so i figured it was not some ultralight thing and it's a brake mounting bolt which shouldn't be stressed that much. Working in underground construction i'm a big fan of ss and use it almost exclusively on my bikes. I rarely use any grade 8 except in auto suspension, snow plow mounting, and known critical strength applications.
* i can't believe how small are the screws holding the derailler hangers to the frame. but you do want that to break rather than the dropout. I just wish they didn't have 500 different ones.
04-20-17, 10:38 AM
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Dedhed, I like your posts for two reasons. First, it's clear that you know your way around mechanical stuff. That could be machinist, auto mechanic, engineer, tool and die maker... whatever. Experience derived knowledge, shared generously, is all good. I learn from your posts.
Second, you're a SE Wisconsinite. I grew up in Racine. Studied engineering at UW (Madison). Great place to live.
Second, you're a SE Wisconsinite. I grew up in Racine. Studied engineering at UW (Madison). Great place to live.
04-20-17, 12:39 PM
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They are small for a purpose as you want them to fail before the frame is damaged. Sort of the bicycle equivalent of shear pins on an outboard motor or on some industrial drives. A built-in weak point to save more expensive stuff.
04-21-17, 10:48 PM
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Uh, looking at the images you posted of the original brake bolt it loks like it's stepped down betwwen the Allen head and the threads. If that's the case the pure Allen head bolt you included the image of in the post will be a loose fit in the hole in the brake.
Can't a bike shop get you a proper replacement bolt?
Cheers
Can't a bike shop get you a proper replacement bolt?
Cheers
