Replacing Rear brake disc

[darrsi]

The allen bolt head rounded off, so after a lot of swearing i cut a slot into it but it still wouldn't budge, even using an impact driver.
Mate saved the day again as he had a blow torch and the heat freed it enough to undo it.
Ran out of light so i'll put the new disc on tomorrow now.


Had an issue with my new PR4 tyre as well.
We reckon it may have been at the bottom of a pile of tyres which made it a bit narrow, so even with a ratchet strap my mechanic couldn't get any air into it.
Fortunately he happened to have another tyre there and he put that on for me instead, which was lucky.
In etween dropping it off and picking it back up i spent a couple of hours servicing and regreasing all of the brake calipers so i've had a productive day, albeit a lot longer than intended plus it was bloody freezing outside.


I've decided i'm not going to use threadlock this time, i'm gonna dip the bolts in engine oil then torque them up.
I might check them every few months anyway but i don't reckon they'll budge at all.

[celticbiker]

I would advise against engine oil, as unlikely as it is there is a chance with it being a liquid that it could leak out and get onto the disc.
If you want to lubricate them I would suggest a high temperature soap based bearing grease or some anti squeal brake pad grease.

[unfazed]

The allen bolt head rounded off, so after a lot of swearing i cut a slot into it but it still wouldn't budge, even using an impact driver.
Mate saved the day again as he had a blow torch and the heat freed it enough to undo it.
Ran out of light so i'll put the new disc on tomorrow now.

Did you not read my post

Heat is your Friend when trying to undo the Disc bolts :thumbup

I would not use oil on the bolts either, clean the threads in the wheel and use blue thread lock, as you discovered heat will soften blue threadlock enough to allow you to safely undo the bolts. Is it worth the risk of the bolt loosening, getting caught in the caliper mount and locking the back wheel, I don't think so.

[darrsi]

I would advise against engine oil, as unlikely as it is there is a chance with it being a liquid that it could leak out and get onto the disc.
If you want to lubricate them I would suggest a high temperature soap based bearing grease or some anti squeal brake pad grease.

Brake pad grease is Copper Grease, that messes with torque settings, whereas oil doesn’t.
I’ll dip them in oil then wipe them with a rag, i just don’t want them going in bone dry.

[darrsi]

[quote author=darrsi link=topic=23511.msg271644#msg271644 date=1511629134]
The allen bolt head rounded off, so after a lot of swearing i cut a slot into it but it still wouldn't budge, even using an impact driver.
Mate saved the day again as he had a blow torch and the heat freed it enough to undo it.
Ran out of light so i'll put the new disc on tomorrow now.

Did you not read my post

Heat is your Friend when trying to undo the Disc bolts :thumbup

I would not use oil on the bolts either, clean the threads in the wheel and use blue thread lock, as you discovered heat will soften blue threadlock enough to allow you to safely undo the bolts. Is it worth the risk of the bolt loosening, getting caught in the caliper mount and locking the back wheel, I don't think so.
[/quote]


Yeah, i know, i need to buy myself a blowtorch.


I just can’t imagine these bolts EVER coming loose once torqued up?
Think i only have 222 Loctite, but that should do the trick without causing too much grief.
I must’ve used that last time actually which is why the other 5 came free okay after a whack with the impact driver.

[tommyardin]

The allen bolt head rounded off, so after a lot of swearing i cut a slot into it but it still wouldn't budge, even using an impact driver.
Mate saved the day again as he had a blow torch and the heat freed it enough to undo it.
Ran out of light so i'll put the new disc on tomorrow now.


Had an issue with my new PR4 tyre as well.
We reckon it may have been at the bottom of a pile of tyres which made it a bit narrow, so even with a ratchet strap my mechanic couldn't get any air into it.
Fortunately he happened to have another tyre there and he put that on for me instead, which was lucky.
In etween dropping it off and picking it back up i spent a couple of hours servicing and regreasing all of the brake calipers so i've had a productive day, albeit a lot longer than intended plus it was bloody freezing outside.


I've decided i'm not going to use threadlock this time, i'm gonna dip the bolts in engine oil then torque them up.
I might check them every few months anyway but i don't reckon they'll budge at all.

Sensible man.
But replace engine oil with copper slip or Red Rubber grease. I check all my bolts every few months, I don't crack them up tighter I just apply some pressure to them and it tells me if they are loose or not.
The only part of my bike I apply LocTite to is the front drive chain (Gearbox) sprocket, then I use to one that go rock hard LocTite 620.

[tommyardin]

LOL! As said in another post a few days ago opinions are like arse holes everyone has one.


Best do your own thing that you are happy with, cos one person will say one thing and another something completely opposite.


Just keep a check on the bolts, if one did come loose it is unlikely to come out and lock the rear wheel, they are spinning at an incredible rate of revolutions and the fists bolt that touches the caliper will make such a din you will pull over to see what it is.


(Be like the old clothes peg and piece of plastic you had on your pushbike you had flicking against you spokes as a kid)


My guess would be that the bolt would only come undone a few turns before it touched the caliper and I'm sure all 5 or is it 6  will not all come loose at the same time.


Anyway good luck with whatever you decide to do Darrsi, your the man who makes the final decision, don't take any notice of anything I say as I am a suicide pilot. :eek

[darrsi]

LOL! As said in another post a few days ago opinions are like arse holes everyone has one.


Best do your own thing that you are happy with, cos one person will say one thing and another something completely opposite.


Just keep a check on the bolts, if one did come loose it is unlikely to come out and lock the rear wheel, they are spinning at an incredible rate of revolutions and the fists bolt that touches the caliper will make such a din you will pull over to see what it is.


(Be like the old clothes peg and piece of plastic you had on your pushbike you had flicking against you spokes as a kid)


My guess would be that the bolt would only come undone a few turns before it touched the caliper and I'm sure all 5 or is it 6  will not all come loose at the same time.


Anyway good luck with whatever you decide to do Darrsi, your the man who makes the final decision, don't take any notice of anything I say as I am a suicide pilot. :eek

I shredded my rear caliper pad pin using copper grease with a torque wrench, even though it was set at something daft like 10Nm.
Copper grease really fooks up torque readings, i've posted on here before about it, but the findings were that if engine oil is used instead then torque settings remain accurate.
I don't know anyone who's ever had a disc bolt come loose if they have been torqued correctly, i just can't see it happening, and as my bike's a commuter plus the fact i'm more pedantic than most at checking things then i'm very confident i would never have an issue.
Add to that i'm lucky if i can hit 40mph going to and from work then i reckon i really won't have any grief.
If i was racing or generally ride like a maniac then i would reassess, but FOR ME that's simply not a problem.


I'll dab a spot of Loctite on and be done with it, but from experience those bolts are a bastard to undo with brute force, so thinking that one may work itself loose just doesn't seem like reality to me.


I admit prevention is better than cure but in this case i just don't see a problem.
If shit happens i'll be the first to shout about it, but there is that chance i will be the first on here!

[darrsi]

I s'pose you really have to take in to consideration that when things go wrong the owner has to take responsibilty too.
We hear of things going bad, but if everything's torqued correctly for example then things should be fine.
I bet there's a lot of people on here that don't even own a torque wrench?

[darrsi]

Just took the bike out to try and scrub the tyre in a little bit while the roads are dry as it was so shiny and slippery i dread the thought of what it would be like in the wet.
It was worth all the effort though, a new tyre always feels great anyway and spending a few hours cleaning up and regreasing the calipers a couple of times a year works wonders in the long run.
Job's a good'un 

[tommyardin]

Sounds like you have it nailed

[Jamieg285]

If it makes you feel any better, I tried to do my front discs yesterday.  11 bolts fine.  1 bolt rounded out. Smacked in a slightly bigger imperial allen head socket and had a go with that, and it sheared the bolt - below the level of the wheel hub  :'(

Attacked it with a drill, got the centre out and tried some bolt extracters.  Got them to bite on the bolt, but it's stuck fast  :'(

Drilled out out as far as I could without going into the threads, but still no joy.  I've been out and bought a 6.8mm drill bit and an M8 tap to try as a last resort.


The PR4s are a toughy to fit.  I've had 2 and neither wanted to seal the 'normal' way.  The trick I used (borrowed from a fitter) is to fire a burst of un-restricted compressed air down the bead rather than through the valve.  There's a proper tool to do it (Bead Cheater?), but that's expensive, so I just hooked up a piece of hose pipe to the compressor outlet and it worked just as well.

[darrsi]

If it makes you feel any better, I tried to do my front discs yesterday.  11 bolts fine.  1 bolt rounded out. Smacked in a slightly bigger imperial allen head socket and had a go with that, and it sheared the bolt - below the level of the wheel hub  :'(

Attacked it with a drill, got the centre out and tried some bolt extracters.  Got them to bite on the bolt, but it's stuck fast  :'(

Drilled out out as far as I could without going into the threads, but still no joy.  I've been out and bought a 6.8mm drill bit and an M8 tap to try as a last resort.


The PR4s are a toughy to fit.  I've had 2 and neither wanted to seal the 'normal' way.  The trick I used (borrowed from a fitter) is to fire a burst of un-restricted compressed air down the bead rather than through the valve.  There's a proper tool to do it (Bead Cheater?), but that's expensive, so I just hooked up a piece of hose pipe to the compressor outlet and it worked just as well.

The bolt heads are so soft it's a joke, but I learned from before to make sure I have spares before even attempting to remove any.

[Jamieg285]

I bought the spares ahead of the job, but that's not the problem - It's being able to put it them in again.

Browsing ebay for spare wheels locally now...

[darrsi]

I bought the spares ahead of the job, but that's not the problem - It's being able to put it them in again.

Browsing ebay for spare wheels locally now...

I know it's not something most people have, like me for example, but putting a blowtorch on mine really worked wonders in a couple of minutes to soften the Loctite. If you have an extractor and you've already got it to bite then it may be worth giving it a go.

[Hugh Mungus]

A blow torch is a pretty cheap thing to buy. It's worth getting one to make the job a whole lot easier.
I wouldn't attempt to undo disc bolts without heating them up first.

[Disorderlypunk]

if i ever buy another blow torch i will buy the one with the piezo igniter cause sods law the moment you need it you wont find a lighter
-and when you turn to the backup matchsticks that have sat in the drawer for 3 years you realise they got damp and wont light

[Hugh Mungus]

Yep, and now I have stopped smoking the ciggies I don't carry a lighter around all the time. You can bet the one in the garage will go missing when someone borrows it to light their fags.

[Jules-C]

Also check eBay for left hand drill bits the heat from drilling softens the threadlock and the left-handed turn can start to undo the bolt at the same time

[Jamieg285]

Too late now.  The 6.8mm got the remains of the bolt out and I cleaned up the threads with a tap.  All looked good until I tried to torque them and the thread gave way.

I'll have a look at threaded inserts next, but I'll have to get another wheel, as I need to be back on the road next week.