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Discussion Starter #1 (Edited)
I noticed another thread here about a brake repair on their Bolt. I got the same suggestion from a Chevy dealer. The winter salt has done a job on these, see picture. They wanted $450 to do a brake job, so I gave it a go. Now I read online the Caliper Brackets use TTY bolts. Does anyone know the rear torque specifications both ft-lbs and angle?
224947C6-5C62-461A-BB57-E556B7DC4596.jpeg
 

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1. Gnarly. Where do you live? when I lived in Maine the whole underside of my car looked like that in no time. It was terrible.
2. Maybe ask the auto parts store about the spec. On top of that, and please correct me if I'm wrong, but don't the fasteners ( in the case of tty) themselves determine the amount of torque you need to apply until they start to stretch/yield? Obviously if you're using the spec screw then you would just torque to the number in the manual. I guess you'd probably just torque to that number anyways but my point is is that the fastener may be rated to a torque, precisely because of their nature, which, lacking better information from the service manual, It's probably the right number to land at for the bolts.
 

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Discussion Starter #3
1. Gnarly. Where do you live? when I lived in Maine the whole underside of my car looked like that in no time. It was terrible.
2. Maybe ask the auto parts store about the spec. On top of that, and please correct me if I'm wrong, but don't the fasteners ( in the case of tty) themselves determine the amount of torque you need to apply until they start to stretch/yield? Obviously if you're using the spec screw then you would just torque to the number in the manual. I guess you'd probably just torque to that number anyways but my point is is that the fastener may be rated to a torque, precisely because of their nature, which, lacking better information from the service manual, It's probably the right number to land at for the bolts.
Upstate NY. I’ll have to stop by a dealer parts shop to order a few, maybe they come with specs. I hardly use the brakes so the pads were almost full, the new rotors are a little thinner than the rusted ones. I’m not really worried about them breaking but I am concerned about them loosening. 36 months and 19,000 miles.
 

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but don't the fasteners ( in the case of tty) themselves determine the amount of torque you need to apply until they start to stretch/yield? Obviously if you're using the spec screw then you would just torque to the number in the manual.
Many (most?) TTY fasteners are torque plus angle values - so an example spec may be 35 lb pounds and then 120 degrees further rotation . However some torque plus angle are not TTY.
 

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Discussion Starter #5
From what I am told these are not TTY bolts but they are single use. The front caliper bracket bolt should be tightened to 118 lb ft, and the back 74 lb ft. If anyone needs this info
 

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From what I am told these are not TTY bolts but they are single use. The front caliper bracket bolt should be tightened to 118 lb ft, and the back 74 lb ft. If anyone needs this info
Hmm, any idea why they would be single use, if not TTY? If not TTY there would be no appreciable stretch, so little fatigue over a 100,000 miles. Mercedes makes some single use / non-TTY fasteners, but these are for fasteners with thread lock-like material on them. Last I read GM tech guidance, I think I remember allowing reuse of similar bolts using Blue thread lock.
 

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Discussion Starter #8
Hmm, any idea why they would be single use, if not TTY? If not TTY there would be no appreciable stretch, so little fatigue over a 100,000 miles. Mercedes makes some single use / non-TTY fasteners, but these are for fasteners with thread lock-like material on them. Last I read GM tech guidance, I think I remember allowing reuse of similar bolts using Blue thread lock.
In my opinion they must function as TTY bolts but according to the service manual I see no mention of a post torque angle of turn.
 

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Sorry for your problems. Since the Bolt rotors get so little use, did you check on having them turned? That was SOP for the first forty years of disc brake repair, but this century most shops prefer to sell you new rotors because it's quicker in-out and more parts is more profitable.

We have magnesium chloride liquid put down as a de-icer and it's nasty on aluminum, but thus far has done no damage to our 2017 rotors. I just installed winter tires and the rotors were still shiny, clean, perfect.

jack vines
 

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Discussion Starter #10 (Edited)
Sorry for your problems. Since the Bolt rotors get so little use, did you check on having them turned? That was SOP for the first forty years of disc brake repair, but this century most shops prefer to sell you new rotors because it's quicker in-out and more parts is more profitable.

We have magnesium chloride liquid put down as a de-icer and it's nasty on aluminum, but thus far has done no damage to our 2017 rotors. I just installed winter tires and the rotors were still shiny, clean, perfect.

jack vines
There is enough thickness for them to be turned, I’ll save these and use them next time. I have done many brake jobs in my life so it’s not a big deal for me. It’s just a bit of a surprise and it will cost most owners quite a bit to fix, for brakes you hardly use. I guess I just want to warn people that if you live in a winter wonderland these brakes will rust badly. I probably did too much one pedal driving in low and the brakes just didn’t get used enough. So if you drive in a lot of snow and salt, use the brakes more. On mine the inside of the rotors were much worse than the face so look at the back side once in a while.
 

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...I probably did too much one pedal driving in low and the brakes just didn’t get used enough. So if you drive in a lot of snow and salt, use the brakes more.
Just a reminder that the hydraulic brakes aren't used in "L more or "D" mode unless you're braking so hard that you exceed the car's regen capacity. So it'll take some pretty hard stops to engage the rear brakes. Either that or charge to 100% where there's very little regen available.
 

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Discussion Starter #12 (Edited)
Just a reminder that the hydraulic brakes aren't used in "L more or "D" mode unless you're braking so hard that you exceed the car's regen capacity. So it'll take some pretty hard stops to engage the rear brakes. Either that or charge to 100% where there's very little regen available.
Yes I notice that the regen really does most of the braking. It looks like I’ll be turning my rotors every 3 years
 

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Discussion Starter #13
4BF46017-0C24-4AFF-A2F5-5027600A6EB9.jpeg


The inside of the front rotors were bad too! The surprising thing is that outside looks fine, I guess the guide pins needed grease. I’ll have to regrease those more often.
 

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I guess the guide pins needed grease. I’ll have to regrease those more often.
The caliper slider pins have been the source of brake problems on several of my cars:
gassers, hybrids, PHEV and now my Spark EV.

In Salt Country I think they should be disassembled, cleaned and regrease maybe every 2 years or so.
You definitely can't wait until the pads wear out.

I bought a big tube of the special grease, although you can get it in the 'ketchup packets' at the checkout of auto parts.
It's not a bad job if you catch it before they start to lock up with rust.
I pack the Hay-L out of them. It seems that they only get a 'hint O'grease' from the factory.
 

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Discussion Starter #15
The caliper slider pins have been the source of brake problems on several of my cars:
gassers, hybrids, PHEV and now my Spark EV.

In Salt Country I think they should be disassembled, cleaned and regrease maybe every 2 years or so.
You definitely can't wait until the pads wear out.

I bought a big tube of the special grease, although you can get it in the 'ketchup packets' at the checkout of auto parts.
It's not a bad job if you catch it before they start to lock up with rust.
I pack the Hay-L out of them. It seems that they only get a 'hint O'grease' from the factory.
You are right there wasn’t much grease on the pins and it was somewhat dry. I’ll have to increase my pin maintenance routine. 35 months and 19,000 miles didn’t seem that long for disk brakes but I think the EV low use was a factor in this.
 

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Just a reminder that the hydraulic brakes aren't used in "L more or "D" mode unless you're braking so hard that you exceed the car's regen capacity. So it'll take some pretty hard stops to engage the rear brakes. Either that or charge to 100% where there's very little regen available.
Another time there is no regen is in reverse. I keep my rotors shiny when I reverse down my very steep driveway every day.
 

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I’ve given up driving in L and use D all the time, now. The efficiency loss is far less than the cost of a brake job.

Use your brakes to maintain them.
 

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Discussion Starter #19
I’ve given up driving in L and use D all the time, now. The efficiency loss is far less than the cost of a brake job.

Use your brakes to maintain them.
Yeah, I’m not using L anymore and trying to drive more like the ICE drivers. But boy they really like to use their brakes no wonder their wheels are covered with brake dust.
 

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I’ve given up driving in L and use D all the time, now. The efficiency loss is far less than the cost of a brake job.

Use your brakes to maintain them.
If the decel rates are the same in L and D there is no difference in efficiency.
The Brake Pads start working after the Regen power is maxed out when braking in D.

To remind your Pads and Disc what their job is:
Once in a while when exiting a highway, shift to N and wait to brake hard to a stop.
Get those components warm to hot once in a while! They like it!! ;)

But this does not help with salty water getting into the caliper slider pins.
These components need routine maintenance.
Chevy doesn't call this out, but I think I read that Brand T is now recommending this service.
 
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