What is the reasoning behind torx bolts?
 

Is there a specific reason why engineers decided to use so many torx bolts on the new MB models? My W140 requires a torx bit to remove the transmission pan. It requires an external torx socket to remove the covers to change the spark plugs. The intake manifold is secured with hex bolts, but the two bolts closest to the firewall are torx bolts.

Is there any engineering reason for using torx instead of hex or is MB simply trying to make it inconvenient for owners to work on their vehicles? I've never seen any torx bolts on my W201. It's not that big of a deal anymore now that I have the torx sockets, but those external torx sockets were a bit hard to find. I don't see why an external torx bolt would be superior to a hex bolt just to hold down the plastic covers over the plugs and coil packs.:confused:

I think they are used because the tool can hold the bolt when the car is being made on the assembly line.

IMHO. torx heads are the sex of bolt heads. i am sick and tired of Philips screw drivers. they are an old and outdated technology that refuses to die.

hex heads are good also but ive broken of so many of my ball headed ones trying to break intake manifold bolts. im just tired of it.

torx just makes everything easier except when all the bolts aren't torx, as in your case.

i just took apart my cell phone today to get at a broken piece that was vibrating. stripped every single Gdamn philips screw in there. if they were torx that wouldn't have happened. because you can apply so much more torque to them.

if someone has ever stripped a torx head. please tell me

i concur! stripped heads are more a pain than locating torx tools. :) they're A LOT easier to apply force to... no angling problems whatsoever

I agree TORX is the way forward - it would be nice to buy a second hand car for once where someone before me has not rounded off screw heads and then put them back...

That has not always been the case. In the seventies, Torx tools were tough to find and expen$ive when you found them.

As one who was around long before Torx bolts came into vogue I think I can offer a different perspective.

When Torx fasteners came along, they were made available to all sorts of manufacturers at literally a give away price. In service manuals or ANYWHERE that you saw the name Torx, it had the registered trademark logo. The only people that could legally make and sell the tools had to do so under license to the Torx people.

These people made a FORTUNE by creating demand for an item (the Torx tools) that NO ONE except themselves could legally supply.

In the beginning these were only found on non automotive items, such as electronics, computers and such, but once they got the car makers signed on it was a steady trip to the bank.

They followed the Xerox business model. When Xerox came out with the photocopier, they would not sell the machines, they would only lease them and at a reasonable price. In the beginning, however, the people who leased the machines, signed an exclusive contract so that toner and paper could only be purchased from Xerox.

Torx fasteners in the proper application do provide a better fastener/tool combination, than many other choices. There are SOME applications, where a bolt can get frozen in place where they are NOT good choices. Anywhere near exhaust components is a good example of this. These are usually difficult to access and once the center of the hole is stripped out, the only alternative is grinding, drilling, ease outs, etc.

TORX has twice as many surfaces, and at a better angle to the force, than hex-heads. It is a better design, provided the correct tool is used and if an internal torx, the hole is clean.

As I understand it, you can put more torque on a fastener with a torx head than with an allen head.

Nope. Torque is torque. The size/composition of the bolt shaft determines the amount. Now, grip, on the other hand is enhanced by the use of the Torx socket.

I think that Mike makes the necessary distinction. The Torx head can increase the grip, but not the torque applied to the threads of the fastener.

That said, a proper fitting key in a hex socket head has the necessary grip for its size. The advantage of Torx fasteners is not for the person removing and reinstalling the fasteners. The advantage is for the tool makers. Once the patent runs out, they will find something else.

I'd love it if everything was torx on the car, I'd go right out and get the tools for it.

Be careful what you ask for, because you might get it. There are many applications where Torx is convenient, but there are places where you DO NOT want Torx.
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First off they do not lend themselves well to large application. Secondly, you do NOT want them in high heat areas like exhaust.

When a hex head bolt rounds off or otherwise gives trouble there are many things you can do. With a large Torx, once it strips you're (pardon the pun) screwed.

I worked for a while on a large fleet of electric fork trucks of which the manufacturer obviously took advantage of the low cost of Torx fasteners. This was equipment that was heavily abused, so I was digging out broken bolts all too often. I would rather deal with a buggered up hex head bolt or screw rather than a Torx any time.

I suppose.....but why is a Torx bolt any cheaper than a hex/allen bolt?

Personally, I don't like fasteners where the engagement surface is on the inside. Unless they're grade 8 or above, they're too easy to strip or break.

I also don't like head bolts. Any race engine I build (non-MB so far) gets studs mounted into the block/head. Every time you torque and untorque a fastener, you weaken the overall clamping power. I can't remember specifically, but by the time you do it 7 times, reliable clamping power has been reduced by like 90% or something. You see, when you screw something in, you're deforming the threads on both the fastener and what you're fastening too. Think bending a wire hanger back & forth.

It's much cheaper/stronger to use a highly hardened stud with a "softer" nut to secure something, because nuts are cheap. Of course, given space limitations, this is not always possible. I think this is why torx has become popular, because it offers the most engagement surface to transfer the torque from your hand/air tool to the fastener, which also allows the fastener to be fastened at a higher torque than say an allen head, for example.

You have to take into account the size of a hex head and the space required for the socket required to manipulate it. Sometimes there's just not enough space.

Obviously, none of you people have to deal with these blasted Torx bolts & screws, enough to fully appreciate all of the set backs these damned things create. I work all day with Torx heads, and the son of *****es constantly round out, or cause you to snap off the head of the Torx bit, because though they make torx bolts, nobody has the technology yet to figure out that they need to make the bits out of a harder steel. Even the Snap-On, and Mac bits break off. I hate Torx, Allen head, and most of all those damned funky spline type ones that VW uses all over their cars, including their lug-locks and even the damned head bolts on the engine... WTF!!!!???? Give me good old flat head, Phillips head, and Hex head nuts & bolts any day of the week.