Why do disk rotors use torx bolts?

Why not use Allen bolts? Is is because they sit slightly more flush?

And don’t round as easily…

Hope used to use bolts that took 4mm Allen key and they used to round off and fail a lot.
T25 bolts seem far better and now only have to remove busted ones when people either use the wrong tool or over tighten them.
Iirc it’s about 5 nm for rotor bolts

I was to slow

Factories like them as they are easier for robots to use… you’ll notice they stay on the torx driver better than a bolt does on a hex key.

To really wind you up because I’m sorry but torx bots round far, far easier than allen bolts. I don’t care what a load of research at a university says, my experience is it’s easier to round a torx bolt than an allen bolt. Rounded off loads of the former, none of the latter.

ANd… why do disks need to stay on so tight anyway? It makes no sense. You’ll notice a couple of loose bolts very quickly on a disk. Only one bolt on your seatpost needs to fail slightly and bingo, you’ll be in pain. You’ll notice that your seatpost bolt is an always will be an allen key. Why is that, I though they rounded off too easy…

Marketing bollocks.

Because cap head screws have a deeper insertion depth, so hex does the job fine in that application. Rotor bolts tend to be button head (due to clearance issues) which are much shallower.

Don’t think I’ve ever rounded off a torx screw, maybe you’re not doing it right 😉

I’m with Samuri on this one – chewed up dozens of the little buggers!

Utter tosh SRAM have it right torx should become the standard fit esp given the amount of alloy and ti bolts
Hex is fine on larger bolts but rubbish on smaller ones.

How have you killed a torx bolt ? Torque wrench time maybe

Torx are easy to round out if they’re dirty- shallow insertion means mud in the bottom becomes an issue faster than it does with hex. User error in that case obviously. Also, they tend to get used in fiddly jobs- like, you might say Formula brake torx are a bit easy to round, but that’s because they’re bloomin tiny and sometimes in alu heads, not because they’re torx.

(also, the bits tend to have a slight taper- though I’m never sure if that’s part of the torx standard or not, I’ve got some straight-sided torq bits and some tapered)

Never come close to rounding a torx – and I encounter them quite often at work, not just on the odd disc. Cack handed buggers! 😉

legend – Member
Because cap head screws have a deeper insertion depth, so hex does the job fine in that application. Rotor bolts tend to be button head (due to clearance issues) which are much shallower.

Don’t think I’ve ever rounded off a torx screw, maybe you’re not doing it right

+1 sensible reason for having them, if you’re managing to round them, clear the crap out before you tighten up and stop being such a gorilla FFS.

Rounding off a torx is easy if you use cheap tools that don’t have good enough tolerances or too soft metal.
Generally speaking, its much easier to round a 4mm allen head than a torx t25.

Why the hell do orange use pozi drive screws for there hangers.Absolute crap idea.Who uses pozies on an mtb…Apollo perhaps. 😆
I rounded one strait away with a brand new dewalt bit in a hand driver.Now gone and replaced with Ti torx…. 😉

i took a T25 torx bit and ground about 1mm of the bottom, this takes of the very slight taper and leaves you with a tool that engages fully in the very shallow disc heads. No problems anymore!

Like for like on a button head screw, Torx wins every time over a hex head. If your still rounding them off, you really are doing something wrong.

I was warned by the mods a few years ago for an obscenity-ridden rant. I’d just finished a brand new build (except attaching the disc rotors). It was midnightish, didn’t have a T25 and couldn’t ride my new toy!

However, I love torx. Far less easy to round. Just swapped a hope stem (hex) for a Crank Bros (torx). There was noticeably less wobble in the torx ‘connection’. That was using an expensive set of ball-head hex keys in ti bolts vs a cheapo Stanley set of torx keys.

Northwind, the straighter sided ones you have will be Torx +.

I used to work for the fastener co which did the r&d on the patent for it. There is some very compelling science/engineering for using Torx of whatever variety over just about anything else.

Ball end hex will never be good for puting a high load through.
Good for running bolts in but not the finally tighnhing.

More driving surfaces to spread the load …
It matters when you are in smaller bolt sizes – stops rounding off

samuri – Member
ANd… why do disks need to stay on so tight anyway? It makes no sense. You’ll notice a couple of loose bolts very quickly on a disk. Only one bolt on your seatpost needs to fail slightly and bingo, you’ll be in pain. You’ll notice that your seatpost bolt is an always will be an allen key. Why is that, I though they rounded off too easy…

Marketing bollocks.

because the seatpost bolts head is about 3 times as deep

edit: doh should have read the rest of the replies

It would be nice if manufacturers would pick a bolt type/size and stick with it: my Ragley grips use a 3mm bolt at one end and a 2.5mm at the other; my Shimano cable disk calpier uses two different sizes as well.

IIRC, for his Great Divide bike, Aiden Harding replaced a bunch of bolts on his bike so he had to carry just one size of allen key.

Anyone got any numbers?

If being a cack handed bugger renders the science pointless then the technology is also pointless. I’ll hold my hands up to not being a great mechanic so I need some foolproof technology to stop me cocking things up. Allen keys and bolts seem to work for me.

My experience with torx bolts is that the key has to be absolutely perfectly aligned to make it work, little big of dirt in the bottom or I haven’t, god forbid, got my torque wrench with me out on a ride and it’s round off time. Never, ever had these same problems with allen bolts.

YMMV

5mm bolt on brakes 4mm for shifters…this winds me up everytime… Just stop

Agreed, why “mix n match” bolts, why not use a similar size for similar uses??? 🙄

I’ve nerfed a few torx disc bolts, resulted in drilling them out grrrrrrrrr 😈

I’ve never had an issue with Torx disc bolts but some people do…I remember sorting a fair few out when I worked in a shop.

Those old 4mm Hope ones were made of cheese though so at least they were easy to drill out when the roadnded off.

Noticed that chainring bolts have started to come with torx too. A hundred years of hex bolts apparently no longer good enough. Bit of a pain as I now need a T40 in my bike box.

the people who have managed to round off a torx – maybe the tool is damaged? i only use 3/8″ drive ratchet type bits on a screwdriver handle extension. the allen key types are harder to use – by this i mean keep the torx key perpendicular to the head of the bolt. There is not as much engagement as an allen key so you need to support the tool when you lean on it. not so much an issue if you use a ratchet type tool.

my pet hate is worn mutlitools – as soon as there is any damage at all on the tool (particularly allen/hex keys), throw it away, because it will screw up the fastener.

Almost always when I’ve seen someone round a torx bolt, it been as a result of using the wrong size bit (usually the size below the size you need will still “work”) and/or poor insertion of the tool followed by a massive application of force rather than an incremental one.

i’ve rounded both T25 and hex bolts on my rotors, but it seems hex bolts are easier…its probably to do with me subconsciously thinking i can swing on them like i would on any other hex bolt on the bike…
the only advantage with T25 on a rotor are the clearances you get…but if they get rounded then they’re a PITA to remove…at least if you round a hex bolt you can still remove it pretty easily…just tap a T25 bit into it and then unscrew the bugger…

Marketing bollocks.

That’s the Grand Torx Key Association marketing to the bike companies then, is it? 😆

Hope used to use bolts that took 4mm Allen key and they used to round off and fail a lot.

Very true for me – just the other month I finally managed to painstakingly extract the body of a Hope disc bolt where the hex head had sheared clean off.

Was replaced by a nice new Torx bolt.

T25 bolts seem far better and now only have to remove busted ones when people either use the wrong tool or over tighten them.
Iirc it’s about 5 nm for rotor bolts

I only recently got a torque wrench and I was surprised at how little 5nm is. It’s not nearly as tight as I guestimated.

This may or may not be related to the incident above 😳

Maybe it’s just me, but I’ve sheared off more torx bits than any other tool (can’t remember ever rounding one though). I put it down to too many sharp edges giving cracks chance to propogate and the surfaces trying to drive perpendicularly (which relies on a perfect match between the tool and the head, which rarely happens) rather than spreading the load allong the edge of the hex key (look at good sockets, the heads are star shaped, not hexagon so the driver pushes along the edges rather than on the corners).

Their N#1 advantage though is getting out rounded hex screws!

What you have in those bike companies (and here, clearly), is a load of anal engineers all rubbing their thighs at surface area graphs and total load charts and selecting the bolts based on that. Forget what it’s actually like for idiots like me in the field, if you use a set square, label your tools properly and replace them after you’ve used them once, Torx is **** brilliant!

What you’ve just described is pretty much the exact reason that it’s considered a bad idea to use anything smaller than 1/2″ fasteners (i.e about the size of car wheel nuts) on oil field equipment, regardless of what you are using them for. Anything smaller will get broken but 1/2″ and up is unlikely to be stripped by hand and anything that’s too big to do by hand will get done with proper torquing gear so it’s safe. Weight is slightly less of an issue than it is for bikes though…

Sorry, double post.

Torx bolts fine on rotors for me, haven’t rounded one out for years – since I bought a Park T25 tool coincidentally.

I do get very annoyed to see torx bolts on chainsets though. Anyone know whay Shimano do this now? I don’t want to carry a torx tool that big out with me as well as my allen keys.

For what it’s worth I prefer torx on the rotor bolts too, I find them more resistant to rounding out.

I do get very annoyed to see torx bolts on chainsets though. Anyone know whay Shimano do this now? I don’t want to carry a torx tool that big out with me as well as my allen keys.

I think the bolts are aluminium these days aren’t they? Probably because of that. Given how tightly chainring bolts can stick in, the chances of getting an aluminium one out with a plain hex would be slim I’d say. The size of the socket is small for the diameter of the threads too.

I thought we had allen and torx bolts so we had to have more tools in the toolbox. Mmmm, tools.