# Torx vs. Hex



## r1Gel (Jan 14, 2004)

I'm not sure if this is the appropriate forum to ask this, but here goes...

What are the inherent advantages, if any, of Torx heads over Hex/Allen heads? I would think that the small teeth on the Torx head would be more prone to stripping than the larger sides of the hex head. Are Torx bolts better able to handle higher torques (thus the name?) than Hex bolts?

That said, I'm wondering why the standard bolt used for IS disc rotors are the Torx kind. How come no other bolt on my bike has Torx bolts?
I've just recently purchased new rotors for my Avid BBs and promptly stripped some of the Torx heads using my CB17 multi-tool while attempting to remove them. Granted, I probably should've used a proper Torx wrench, but if the Torx standard were any good, I should've at least been able to remove the bolts without this happening. Or are Avid disc bolt heads notoriously weak?

It's pathetic that I have to bring my bike to the shop just to have my disc rotors changed (yes, I failed to do so).

I was about to dismiss center-locks due to the lack of rotor and hub choices, but after this experience, I'm having second thoughts...

PS
I thought about this post before I stripped my Torx heads.


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## Squash (Jul 20, 2003)

*A Torx head can...*

actually accept more torque for a given size bolt than a hex head as long as the proper torx bit is used in conjunction with the bolt! It's the same principle as a philips head screw as opposed to a slot head. The torx pattern has more bearing surface area to spread the torque force over. The more surface area the more torque it will handle. The torx is a system that also lends itself well to applications that require a "shallow" bolt head as in disc brake rotors. In order for a hex head to work and not strip out it requires quite a bit more depth for the head, the torx requires about 30 to 50% less depth. So they are well suited to applications that require a thinner bolt head to prevent clearance issues. This is the primary reason they are used as rotor bolts. The draw back to the system is the wrench and bit used MUST be highly stable and care must be taken not to rock the wrench/bit while applying force to the interface. Also the bit teeth must be in good shape and precisely manufactured and this goes for the bolt head interface as well. If any of the forgoing aren't correct then you run the risk of damaging (stripping) the bolt head interface, as you've found out.

The bottom line is, there is nothing inherently wrong or weak aobut a torx interface. You simply have to understand it's application and use the proper quality tools when dealing with it. Also the reason that you see the torx only on the rotor bolts is, that's the only place that it is actually needed on a bike. Any place else the "standard" hex head bolt aren't likely to create any issues, and they are cheaper to manufacture.

Good Dirt


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## PCC (Sep 5, 2005)

One thing I have noticed with Torx is that you can fit one or two size Torx wrenches smaller than the actual bolt you are trying to remove and this will strip it for sure. If the fit is loose then it is wrong. With an Allen wrench the next smaller wrench will not grab the bolt head so you know to grab the next larger size wrench.


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## r1Gel (Jan 14, 2004)

Squash said:


> actually accept more torque for a given size bolt than a hex head as long as the proper torx bit is used in conjunction with the bolt! It's the same principle as a philips head screw as opposed to a slot head. The torx pattern has more bearing surface area to spread the torque force over. The more surface area the more torque it will handle. The torx is a system that also lends itself well to applications that require a "shallow" bolt head as in disc brake rotors. In order for a hex head to work and not strip out it requires quite a bit more depth for the head, the torx requires about 30 to 50% less depth. So they are well suited to applications that require a thinner bolt head to prevent clearance issues. This is the primary reason they are used as rotor bolts. The draw back to the system is the wrench and bit used MUST be highly stable and care must be taken not to rock the wrench/bit while applying force to the interface. Also the bit teeth must be in good shape and precisely manufactured and this goes for the bolt head interface as well. If any of the forgoing aren't correct then you run the risk of damaging (stripping) the bolt head interface, as you've found out.
> 
> The bottom line is, there is nothing inherently wrong or weak aobut a torx interface. You simply have to understand it's application and use the proper quality tools when dealing with it. Also the reason that you see the torx only on the rotor bolts is, that's the only place that it is actually needed on a bike. Any place else the "standard" hex head bolt aren't likely to create any issues, and they are cheaper to manufacture.
> 
> Good Dirt


Brilliant! Makes perfect sense. Thank you so much for this! Very enlightening indeed. I love these boards  
I suppose it was silly of me to use my multi-tool for the task. I examined my CB17 and noticed that the T25 teeth aren't properly shaped. Heck the construction on the T20 bit on a small,unbranded ratchet kit for the car is more refined than that. I guess I need to invest some more on better quality tools :blush: 
I hope the shop mechanic can still salvage my stupidity :madman: 
Again, many thanks :thumbsup:


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## WTF-IDK (Feb 23, 2009)

An Allen wrench can usually be fitted into a striped out torx headed bolt to remove said bolt.


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## karpiel666 (Jan 7, 2005)

Squash said:


> actually accept more torque for a given size bolt than a hex head as long as the proper torx bit is used in conjunction with the bolt! It's the same principle as a philips head screw as opposed to a slot head. The torx pattern has more bearing surface area to spread the torque force over. The more surface area the more torque it will handle. The torx is a system that also lends itself well to applications that require a "shallow" bolt head as in disc brake rotors. In order for a hex head to work and not strip out it requires quite a bit more depth for the head, the torx requires about 30 to 50% less depth. So they are well suited to applications that require a thinner bolt head to prevent clearance issues. This is the primary reason they are used as rotor bolts. The draw back to the system is the wrench and bit used MUST be highly stable and care must be taken not to rock the wrench/bit while applying force to the interface. Also the bit teeth must be in good shape and precisely manufactured and this goes for the bolt head interface as well. If any of the forgoing aren't correct then you run the risk of damaging (stripping) the bolt head interface, as you've found out.
> 
> The bottom line is, there is nothing inherently wrong or weak aobut a torx interface. You simply have to understand it's application and use the proper quality tools when dealing with it. Also the reason that you see the torx only on the rotor bolts is, that's the only place that it is actually needed on a bike. Any place else the "standard" hex head bolt aren't likely to create any issues, and they are cheaper to manufacture.
> 
> Good Dirt


I always end up twisting the splines on my torx wrenches. 
Never working on a bike though, and only with smaller sizes with siezed bolts.

I have used hex head bolts on my rotors for ages, simply because I needed new bolts one night and the hardware store was still open.


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## Jerk_Chicken (Oct 13, 2005)

Bondhus and Wera are good sources for the highest-end Torx keys you can get.

One criticism I have about Torx is that often times, manufacturers think they can get away using a shallower bolt. This shallow engagement area then leads to stripping many times, especially where only a slightly higher than normal torque is needed, such as in dissimilar metal interfaces.


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## mtnbiker4life (Sep 19, 2005)

In the M5 button head hardware the Hex size is 3mm compared to Torq size T25 in the same size hardware. If you buggered up a T25 then you would certainly F up a 3mm. Most likely their are two reasons why they use button head fasteners is low head height and increased faying surface over a socket head cap screw. Using the correct tool for the job will reduce any possibility of buggering up any fasteners. See the samples enclosed.


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## r1Gel (Jan 14, 2004)

karpiel666 said:


> I have used hex head bolts on my rotors for ages, simply because I needed new bolts one night and the hardware store was still open.


What exact kind of hex bolts are you using? The same as those posted by mtnbiker4life below?


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## r1Gel (Jan 14, 2004)

mtnbiker4life said:


> In the M5 button head hardware the Hex size is 3mm compared to Torq size T25 in the same size hardware. If you buggered up a T25 then you would certainly F up a 3mm. Most likely their are two reasons why they use button head fasteners is low head height and increased faying surface over a socket head cap screw. Using the correct tool for the job will reduce any possibility of buggering up any fasteners. See the samples enclosed.


It would seem that 3rd bolt (hex head) would work as a T25 replacement. I eyeballed my fork (WB RockSolid) and have about 2-3mm clearance between the bolt heads and dropout.


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## 4JawChuck (Dec 1, 2008)

r1Gel said:


> I'm not sure if this is the appropriate forum to ask this, but here goes...
> 
> What are the inherent advantages, if any, of Torx heads over Hex/Allen heads? I would think that the small teeth on the Torx head would be more prone to stripping than the larger sides of the hex head. Are Torx bolts better able to handle higher torques (thus the name?) than Hex bolts?
> 
> That said, I'm wondering why the standard bolt used for IS disc rotors are the Torx kind. How come no other bolt on my bike has Torx bolts?


Torx button head bolts are lighter for the same bolt size compared to other fasteners, quite a bit lighter too.


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