Disc to hub bolt

[Ross_328i_sport]

I am looking to replace the bolt holding the disc to the hub could anybody tell me the thread length and thread size.

I am looking to replace with titanium bolt to reduce weights would there be any reason why this would be a bad idea from a materials point of view? (i.e. strength, too brittle)

Thanks

[DCL]

Titanium is a very bad idea. It would not be anywhere near as strong as a graded steel bolt. Titanium is only better on a weight by weight basis but as the density is only around half that of steel, size for size it is much weaker. [edit - reading this again, do you mean the the hub nut that holds the hub to the axle, or the bolts that hold the disc to the hub?]

Edited by DCL on Tuesday 7th July 15:31

[BertBert]

Well if it's the hub nut it's a daft idea for the reasons given. If it's a bolt to locate the disk on the hub, it's a daft idea as you could save more weight by eating one less mars bar a year

[Ross_328i_sport]

It is the bolt that holds the disc to the hub. There are 4 off holding each disc to the hub.

Every little bit helps...

[one eyed mick]

Just take 2 0f them out and bin them you will save perhap 1/2 oz or take all 4 out and save a whole 1oz which will make the car 0.000000000001 % faster or make sure you have pee before you drive it

[harry b]

You can leave them out all together since the disc is kept in place by the wheel studs.
Only if you take of a wheel the disc would wobble, but who rides without a wheel?

[Canuck7]

Hi;
A grade 8 steel bolt runs roughly 150,000 psi tensile strength. Grade 5 Titanium bolts run 140,000 psi tensile strength, and a grade known as Micro64 does 160,000 psi. There's a reason they use ti for turbine blades. lol. It's light, it holds together really well, it is resistant to cutting, and withstands high temperatures. For a bolt its only weakness is probably its flexibility.
You'd have to ask an engineer to be really safe, but a good Ti bolt is probably better and lasts longer than a run-of-the-mill steel bolt. Since it is spinning weight, it does make a bit of a difference. I used to use Ti bolts and nuts and axles on my mountain bikes. I used to bend and break axles a lot, but not with the lighter Ti stuff. If you are fastening it to steel or aluminum you do have to watch for a sort of corrosion, they tend to weld themselves in place if no anti-seize is used.

As for no bolts; the usual ancient caterham design doesn't use the wheel bolts to hold the front brake discs in place. The discs are held on to the back of the hub with 4 separate bolts. Not efficient or very Colin Chapman, as in one part doing double duty - but since they are "borrowed" from a Triumph spitfire, it isn't his fault. ;-)

[KN02LEY]

Don't use Cadmium plated tools on Titanium (not that there should be many about these days) as it can lead to stress corrosion and inter-crystaline cracking.