“Tensile ultimate strength is the stress at which the bolt fails (breaks in half). Tensile yield strength is the stress at which the bolt will receive a permanent set (an elongation from which it will not recover when the force is removed) of 0.2 %. When elongating a fastener prior to reaching the yield point, the fastener is said to be operating in the elastic region; whereas elongation beyond the yield point is referred to as operating in the plastic region, since the fastener has suffered permanent plastic deformation.
High-strength bolts have property class 8.8 or above.” (
http://en.wikipedia.org/wiki/Screws)
This therefore gives 8.8 HT (Standard Fiat bolt) a Min Tensile Strength 800 MPa & Min Yield Strength 640 MPa.
Titanium 6Al-4V:
“Titanium is extensively used in the aerospace industry and increasingly used in general engineering applications especially where high strength/weight ratio and corrosion resistance are major considerations.
Applications include pumps and valves, turbines and airframes, fasteners, automotive components including valves, springs and connecting rods…
Titanium 6Al-4V is a high-strength, alpha-beta alloy which is fully heat-treatable and is the most versatile of the titanium alloys.” (
http://www.maher.co.uk/alloyTitan6AL4V.php)
Min Tensile Strength 897 MPa
Min Yield Strength 827 MPa
Inconel 718:
“Alloy 718 was initially developed for the aerospace industry but its excellent strength and corrosion resistance were recognised by the oil industry and it is now widely used in this field also.
Alloy 718 for aerospace and power generation is heat treated to give maximum strength and high creep resistance with typical hardness values exceeding 42HRC. The major applications are components for gas turbines, aircraft engines, fasteners and other high strength applications.” (
http://www.maher.co.uk/alloy718.php)
Min Tensile Strength 1275 MPa
Min Yield Strength 1034 MPa
“Titanium bolts can replace both grade 5 and grade 8 steel bolts which have minimum UTS requirements of 120,000 psi and 150,000 psi respectively. Metric bolts with an 8.8 rating can be replaced with titanium while bolts with a 10.9 rating can sometimes be replaced with titanium depending on intended use. Any bolts with a rating over 10.9 rating should not be replaced with titanium.” (
http://www.mettec.com/technical.htm)
“New titanium wheel bolts and damper springs increase resistance to roll and dip and have made directional changes more rapid.”
“the 19-inch Challenge-style BBS alloy wheels being secured by titanium bolts and shod with Pirelli P Zero Corsa tyres designed specifically for this car.”
(
http://www.qv500.com/ferrari360p4.php)
As you can see from his sig, Ash has 17” stilo wheels, so PCD will be 98, and I would speculate that they have the correct centre bore also.
If the material has a higher minimum yield, let alone tensile strength there is no way it will shear under tightening before a bolt with lesser values.
At the end of the day there is more than one person on here with “Ferrari in affordable trim” in their signature and no one is going to take your word over that of a 360 Modena Challenge Stradale, or at least that of the design team. If Ferrari utilises titanium wheel bolts then im sure they are more than suitable for any Bravo.
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