Brake disc mounting bolts...?

[Gobert23]

Now I, perhaps foolishly, thought that picking out replacement front brake disc mounting bolts for my Ducati would be dead easy; but how wrong could I be...

Having had a nose around, it turns out that there's a whole lot of choice (with a matching number of mixed opinions).

Q. When I'm mounting Brembo discs/rotors to magnesium wheels, is there any particular precautions that I should be taking, to ensure that I don't damage anything?

Q. Is there any advantage with using titanium or stainless steel? What sort of 'head' type is recommended (people have mentioned that the 'allen' type can seize and they're a nightmare to get out)??

It's a critical component, so I want to get this right. Not fussed about the 'show', I really want to be safe and have it working properly... Ultimate lightness would've been nice, but that's looking like a waste of money (given the hassle people seem to have getting the bolts back out)

Help! (I is confused...)

G

[Evilchicken0]

If you use stainless then you need A4 grade. Have a look at Pro-bolt to see what the standard type is. You can use either a bolt head or Allen key but they mustn't foul on the fork legs or speedo drive (if you have one), you need to locktight them but only use the undo with hand tools type.

Oh stainless is magnetic so if your speedo needs a signal then you need to glue a magnet in there somewhere

[lorenzo]

Stainless isn't especially magnetic, nowhere near as much as most other steels. The other thing is, according to people who know (TriGGer, and I trust him), stainless will corrode into the alloy of your wheels. What you want is to sell a kidney and buy titanium...

[Gobert23]

If you use stainless then you need A4 grade. Have a look at Pro-bolt to see what the standard type is. You can use either a bolt head or Allen key but they mustn't foul on the fork legs or speedo drive (if you have one), you need to locktight them but only use the undo with hand tools type.

'Fouling' shouldn't be a worry, with the offset of the disc(?)

Oh stainless is magnetic so if your speedo needs a signal then you need to glue a magnet in there somewhere

It's not a worry, as the drive isn't electrical/electronic... The Duc's still ol' school

<snip> stainless will corrode into the alloy of your wheels. What you want is to sell a kidney and buy titanium...

'Corrosion' or reaction between the different materials is a bit of a worry, as I've not worked with 'mag' wheels before. That's kinda way I'm progressing slowly and wanting to get it 'right' (can't afford an expensive mistake )

Titanium seemed to be the 'obvious' answer, but then 'people' (other Duc' forums) are moaning about the titanium bolts seizing into the wheels (badly prepared?) and serious problems trying to strip wheels back down again

Who's got mag' wheels around there??? Help!?

[Mark/Foggy]

Ok I'll wedge in here, I'd go belt and braces.

Chances are that the screw holes and threads in the re-conned wheels need looking at. Remember that the tension you can get in the thread (i.e. torque) is dependent on distorting the softest material, the Mag Alloy. So first thing is to see if all the threads are sound and if any have been Heli-coiled. If you're really lucky all the threads will have been inserted during manufacture. Now you've got a loverly, potentially corrosive mix of steel and mag alloy into which to stick your fastener.

The problems I've faced before are the usual mix of trying to get the dics screwed home in the most approriate manner yet allow them to be worked on, potentially regularly. I like High Tensile (black) dome heads as they don't cost a lot and will take a bit of allen key butchery before they need replacing. Look gash though and you'll be needing a fair bit of Copper slip in there if you want to get them out after a shitty winter! Where clearance is an issue, we've countersunk the disc carriers and used Ti Countersunk screws of late. They are expensive and the allen key point wears very rapidly, leading to having to carry spares. Where this solution is good is that you've got a lot of 'bearing' in the countersink and as a consequence don't need to do them up bastard tight and you can get away without any threadlock. We mark them with a witness mark to spot if they're on the move and this is a good solution as the corrosion is minimal, once it starts though drilling out is the only option to getting the dscs off.

For me, in your scenario with the dished discs, I'd go for Ti Drilled Hex Heads. With these you can pop some threadlock in, copperslip the shank, fit them at a lowish torque figure and then lockwire them together to stop them walking out. Bastard to keep clean, but will look trick as fook. Obviously if you've got a shoulder screw as standard, you'll be looking at different options, Probolt Ti Yamaha fitment aren't bad.

[Gobert23]

^^ Cheers for that, at least I'm not going complete mad (I'm just not familar with all the technical details, to arrive at a definative 'answer')

It looks like my options are pretty narrow, but I'm going to check the threads on the front wheel (single sided rear), so that I can take the next step.

Options from Pro-Bolt look to be limited to:

1. Pro-Bolt 'Flange' Bolts

2. Pro-Bolt 'Allen' bolts

Getting them 'race' prep'ed for lock-wiring sounds like a very sensible idea.

These are goign to be my 'trick' 'Sunday' wheels, so 'winter' roads aren't a worry...

Thoughts?

G

[Mark/Foggy]

That's useful to see what they look like, I'd be tempted to get the size and look through the pre-drilled section on Pro-Bolt's site. You realy don't want to be doing the drilling.

Could look here as well, exchange rates are getting better and the quality is great.

Race Bolts - US

[Evilchicken0]

Where this solution is good is that you've got a lot of 'bearing' in the countersink and as a consequence don't need to do them up bastard tight and you can get away without any threadlock. We mark them with a witness mark to spot if they're on the move and this is a good solution as the corrosion is minimal, once it starts though drilling out is the only option to getting the dscs off.

My Bimota uses c/s bolts - you can see why I said about the speedo drive, if you use anything else it fouls

[Gobert23]

I've got a similar front end (well, discs as least) at the moment, but doesn't use the counter-sunk bolts...

Linky: Duc' on my BikePics page...

[Evilchicken0]

Yes - I've changed to those calipers ... nice aren't they.

[wombat]

Ok I'll wedge in here, I'd go belt and braces.

Chances are that the screw holes and threads in the re-conned wheels need looking at. Remember that the tension you can get in the thread (i.e. torque) is dependent on distorting the softest material, the Mag Alloy. So first thing is to see if all the threads are sound and if any have been Heli-coiled. If you're really lucky all the threads will have been inserted during manufacture. Now you've got a loverly, potentially corrosive mix of steel and mag alloy into which to stick your fastener.

The problems I've faced before are the usual mix of trying to get the dics screwed home in the most approriate manner yet allow them to be worked on, potentially regularly. I like High Tensile (black) dome heads as they don't cost a lot and will take a bit of allen key butchery before they need replacing. Look gash though and you'll be needing a fair bit of Copper slip in there if you want to get them out after a shitty winter! Where clearance is an issue, we've countersunk the disc carriers and used Ti Countersunk screws of late. They are expensive and the allen key point wears very rapidly, leading to having to carry spares. Where this solution is good is that you've got a lot of 'bearing' in the countersink and as a consequence don't need to do them up bastard tight and you can get away without any threadlock. We mark them with a witness mark to spot if they're on the move and this is a good solution as the corrosion is minimal, once it starts though drilling out is the only option to getting the dscs off.

For me, in your scenario with the dished discs, I'd go for Ti Drilled Hex Heads. With these you can pop some threadlock in, copperslip the shank, fit them at a lowish torque figure and then lockwire them together to stop them walking out. Bastard to keep clean, but will look trick as fook. Obviously if you've got a shoulder screw as standard, you'll be looking at different options, Probolt Ti Yamaha fitment aren't bad.

Too true, I just replaced my old worn out rotors on the TRX for a set of S3 Performance Chinese made wavys. Was worried about the stories of the corrosive qualities of of SS bolts, so I too bought a set of high tensile black dome heads from the local engineering shop. Think it cost me less than $10 for 12 bolts, to buy the same number from Pro Bolt would've cost me over $100 Aussie.

only downside is, especially with us having a wet winter is the amount of surface rust they are attracting. I 'spose the solution is a slight wipedown with a bit of WD40, especially inside the allen head socket. Other than that I'm pretty happy!

Bob

[svingel]

Too true, I just replaced my old worn out rotors on the TRX for a set of S3 Performance Chinese made wavys. Was worried about the stories of the corrosive qualities of of SS bolts, so I too bought a set of high tensile black dome heads from the local engineering shop. Think it cost me less than $10 for 12 bolts, to buy the same number from Pro Bolt would've cost me over $100 Aussie.

only downside is, especially with us having a wet winter is the amount of surface rust they are attracting. I 'spose the solution is a slight wipedown with a bit of WD40, especially inside the allen head socket. Other than that I'm pretty happy!

Bob

You can get them nickel plated for not a lot of $, that'll keep corrosion at bay.

[svingel]

Ok I'll wedge in here, I'd go belt and braces.

The problems I've faced before are the usual mix of trying to get the dics screwed home in the most approriate manner yet allow them to be worked on, potentially regularly. I like High Tensile (black) dome heads as they don't cost a lot and will take a bit of allen key butchery before they need replacing. Look gash though and you'll be needing a fair bit of Copper slip in there if you want to get them out after a shitty winter! Where clearance is an issue, we've countersunk the disc carriers and used Ti Countersunk screws of late. They are expensive and the allen key point wears very rapidly, leading to having to carry spares. Where this solution is good is that you've got a lot of 'bearing' in the countersink and as a consequence don't need to do them up bastard tight and you can get away without any threadlock. We mark them with a witness mark to spot if they're on the move and this is a good solution as the corrosion is minimal, once it starts though drilling out is the only option to getting the dscs off.

For me, in your scenario with the dished discs, I'd go for Ti Drilled Hex Heads. With these you can pop some threadlock in, copperslip the shank, fit them at a lowish torque figure and then lockwire them together to stop them walking out. Bastard to keep clean, but will look trick as fook. Obviously if you've got a shoulder screw as standard, you'll be looking at different options, Probolt Ti Yamaha fitment aren't bad.

Tests done at Vestas have shown that copperslip, beside the normal known effect, actually made it possible to lower the torque values used on bolts in the wind turbines. This was due to ..... hmmm something I can best descibe as a kind of hydraulic lock effect (very specific, huh?). Question is would it be enuogh for disc bolts? If so, then the corrosion issue should be a thing of the past.