AM Classics with Ti bolts

[droo]

For the amount of weight you'll save using Ti rotor bolts, rather shake off properly after your pre-race pee. Far safer and far cheaper.

[Meezo]

For the amount of weight you'll save using Ti rotor bolts, rather shake off properly after your pre-race pee. Far safer and far cheaper.

 

and what about the "banned substance" in my pee?

[ChUkKy]

For the amount of weight you'll save using Ti rotor bolts, rather shake off properly after your pre-race pee. Far safer and far cheaper.

 

Just dont shake too much otherwise you end up like George Michael on a public indecency charge

[droo]

Just dont shake too much otherwise you end up like George Michael on a public indecency charge

 

Moderation is the key to many things...

[kosmonooit]

I don't think the issue is corrosion. Ti is successfully used as bolts in many other bicycle parts without any issues at all.

 

I think it has to do with Ti's weak shear strength, compared to steel. Disc bolts are constantly subjected to shear forces and Titanium (depending on the specific alloy) has a shear modulus of 41400 MPa whereas steel is 793000 Mpa. Steel is thus twenty times stronger.

 

What I found out this am is that the galvanic potential between Ti and Al is twice+ than that of between steel and Al, and its ref'ed as a factor in many discussions and articles on the net, hence the need for the compound.

 

And, I doubt the sheer stresses on an mtb disc bolts are anything near to being a factor or close to those you cite, but that's just intuition.

 

Finally, aren't most Ti bolts and components are some type alloy? So that must factor in terms of strength parameters.

 

(for example are terms as Scandium components only have a very small fraction of the element Scandium, the rest is Al ect)

[Eldron]

I don't think the issue is corrosion. Ti is successfully used as bolts in many other bicycle parts without any issues at all.

 

I think it has to do with Ti's weak shear strength, compared to steel. Disc bolts are constantly subjected to shear forces and Titanium (depending on the specific alloy) has a shear modulus of 41400 MPa whereas steel is 793000 Mpa. Steel is thus twenty times stronger.

 

Johan - I think you got a decimal wrong. Most steel are in the 80,000Mpa range - twice as much as Ti. Most bicycles use stainless steel which is a bit lower in the late 60s early 70s Mpa range.

[Johan Bornman]

Johan - I think you got a decimal wrong. Most steel are in the 80,000Mpa range - twice as much as Ti. Most bicycles use stainless steel which is a bit lower in the late 60s early 70s Mpa range.

You're right. Thanks. I always say that Ti is approximately half as strong as steel and twice as strong as aluminium, but that leaves me open to the definition of strength.

 

I got the 79300 from a spec sheet I have here for a brand of hi-tensile bolts.

Edited August 16, 2013 by Johan Bornman

[Johan Bornman]

What I found out this am is that the galvanic potential between Ti and Al is twice+ than that of between steel and Al, and its ref'ed as a factor in many discussions and articles on the net, hence the need for the compound.

 

And, I doubt the sheer stresses on an mtb disc bolts are anything near to being a factor or close to those you cite, but that's just intuition.

 

Finally, aren't most Ti bolts and components are some type alloy? So that must factor in terms of strength parameters.

 

(for example are terms as Scandium components only have a very small fraction of the element Scandium, the rest is Al ect)

 

Yes, there is galvanic potential but like I said, it doesn't seem to be an issue elsewhere on the bike. Upper end Campag and Shimano components are full of Ti bolts and grub screws and I don't ever find the seized. Hence my speculation and looking for other reasons. Maybe AC is just playing it safe, who knows?

 

And, since it is only speculation, I just took the MPa for the most common Ti alloy, the one with Aluminium and Vanadium. I wish warnings would come with reason, so that we know how we can ignore them.

[Skylark]

Just a heads up - my torx head rotor bolts where getting a little tired so I went to the Bolt and Tool shop this afternoon and got 34 stainless steel allen key ones for R19 - what a bargain!!!!

Got some extras, only needed 12 but at that ridiculous price why not get some spares, look nice and spiffy too. Take a sample though to match the size, most are 5mm by 10mm long with a dome Allen key head.

 

[milky4130]

 

Geoff Kabush has sponsored medical insurance! And him having a catastrophic crash will get 15 000 000 you tube and TV hits.... Good for sponsor coverage!!? Personally, i think running 3 bolts per rotor is grounds for a Darwin award.

 

AM hubs come with a red reinforcing ring for use with unsuported rotors ie. rotors with no meat on the rotor between the bolts (formula rotors). This is because the hub also lacks meat around the rotor bolt mounts. There is nothing wrong with the AM hubs if you follow the instruction advice.

 

I cant remember, but i think it also warns against the use of Ti bolts.

sadly that nice looking red reinforcing ring doesn't fit the XT Ice tech rotors but Shimano do supply their own ring/washers.

[milky4130]

Thanks for all the feedback & advise guys, I'm a daredevil descended so will not be chancing 3 ti bolts per rotor, nor 3 Ti-3 Stainless Steel, nor will I will use the Ti bolts with the AM hubs in case they bond, wheels didn't come cheap either so last thing I would want to do is incur more costs later on.

[milky4130]

So I sent them a message on their FB page & this was their reply

 

"Hi M, Good question! Ti bolts stretch and come loose. Aluminum bolts are not strong enough. The steel ones are the only ones that work. Have a nice weekend! AC"