Disk Brake Rotor Botls

scottneilson24

Hi, today i was swapping my old, black, corroded rotor bolts for new shiny blue ones. When i was removing the old bolts every bolt except one of both rotors wouldn't come loose and as a result the head of the bolt was rounded off. I was just wondering if this was a problem that many other people get? I did remove them about 3 months ago and they came loose but for some reason they will not this time around. Does anyone have any easy methods for removing these bolts?

Ouija

If your not planning on using them anymore you can do what i did and just grind the mushroom shaped head away with a dremel to get the rotor off. With no pressure on the thread the remaining screw just comes out with a pair of plyers.

Can also try drilling them out with the appropriate tool (which you can get at most DIY stores).

cooldad

Shiny blue ones presumably means anodised aluminium bolts. Not my idea of ideal rotor bolts, but once you've got the old ones out, tighten the new ones bit by bit, tweaking opposites up each time. don't tighten one fully, then the next.

scottneilson24

Yeah they are, and i tightened them one by one opposite until they were secured. Do you think it could have originally been caused by tightening them up wrong?

cooldad

Overtightening probably.

njee20

Just corrosion I'd say. Combined with cheap tools damaging heads.

Alloy rotor bolts aren't great though, shallow heads make rounding very likely in future.

CitizenLee

If you dont have a Dremel you can use a jr hacksaw to saw a groove in the bolt head then use a flat head screwdriver. Or sometimes you can jam a torx bit in and get enough grip to remove it.

scottneilson24

Managed to get it out, i hammered an old drill bit into the screw and then used an allen key

Kowalski675

scottneilson24 wrote:

Yeah they are, and i tightened them one by one opposite until they were secured. Do you think it could have originally been caused by tightening them up wrong?

If they're steel screws (they're only bolts if the shank is partly blank) into an ally hub then your problem is probably galvanic corrosion. Moisture promotes a chemical reaction that basically welds the two different metals together. Using copper grease (or similar anti seize product) stops this happening.

njee20

they're only bolts if the shank is partly blank

I'm calling boLOLocks on that. Agree with the rest though.

cooldad

njee20 wrote:

they're only bolts if the shank is partly blank

I'm calling boLOLocks on that. Agree with the rest though.

I saw what you did there.

bennyy

It's true, bolts have a non threaded section, fully threaded are called set screws

stubs

Strictly speaking set screws are for fixing things like pulleys to shafts. Cap Head Screws or Cap Head Bolts is what thay are properly called but it makes about 0.00% difference.

Scozz76

and this discussion is "riveting" ;-P

Kowalski675

njee20 wrote:

they're only bolts if the shank is partly blank

I'm calling boLOLocks on that. Agree with the rest though.

Far be it for me to try stop you from parading your ignorance to the world, fill your boots.

If the shank's fully threaded it's a machine screw, if the shank has a blank section it's a bolt. This is fact, whether you know it or not (which, evidently, you do not).

Kowalski675

stubs wrote:

Strictly speaking set screws are for fixing things like pulleys to shafts. Cap Head Screws or Cap Head Bolts is what thay are properly called but it makes about 0.00% difference.

A cap head screw (or bolt) just refers to the head type - it's another word for an allen head screw.

njee20

Please - parade my ignorance, find me a definitive definition that that is the difference.

cooldad

My definitions.
A bolt is cylindrical and screws into a nut or threaded part.
A screw has a pointy bit.

stubs

There is no universally accepted distinction between a screw and a bolt. Machinery's Handbook describes the distinction as follows:

A bolt is an externally threaded fastener designed for insertion through holes in assembled parts, and is normally intended to be tightened or released by torquing a nut. A screw is an externally threaded fastener capable of being inserted into holes in assembled parts, of mating with a preformed internal thread or forming its own thread, and of being tightened or released by torquing the head. An externally threaded fastener which is prevented from being turned during assembly and which can be tightened or released only by torquing a nut is a bolt. (Example: round head bolts, track bolts, plow bolts.) An externally threaded fastener that has thread form which prohibits assembly with a nut having a straight thread of multiple pitch length is a screw.

There that makes it utterly obvious you can call it a screw or a bolt no one gives a flying censored

cooldad

So what I said.

stubs

cooldad wrote:

So what I said.

Yes

jimothy78

Back to the original question, is it possible you used the wrong tool? MOST rotor bolts/screws (hedging my bets, here) use a T25 Torx bit, but SOME use an allen key, and if you didn't look closely, you might have picked the wrong tool, which would increase the chances of rounding out the hole.

njee20

The alu ones I had used a T20 head, which was just a pain.

Kowalski675

cooldad wrote:

My definitions.
A bolt is cylindrical and screws into a nut or threaded part.
A screw has a pointy bit.

WALOB.

Kowalski675

njee20 wrote:

The alu ones I had used a T20 head, which was just a pain.

Why? Torx heads are a very good design - they'll take much higher torques than allen heads before rounding off (particularly on soft ally fasteners).

cooldad

Because T20 is rather small.

Kowalski675

Maybe if you have sausage fingers. Smaller fasteners benefit more from a Torx head than larger ones.

njee20

Kowalski675 wrote:

njee20 wrote:

The alu ones I had used a T20 head, which was just a pain.

Why? Torx heads are a very good design - they'll take much higher torques than allen heads before rounding off (particularly on soft ally fasteners).

Because everything else is T25, so I had better quality T25 bits than T20, and a bike covered in T25 heads (SRAM XX is all torx) with some rotor bolts needing a different tool. I'm well aware of the advantages of torx fittings thanks.

Still waiting for your example of the bolt/screw definition?

Kowalski675

njee20 wrote:

Because everything else is T25, so I had better quality T25 bits than T20

Not the bike's fault that your tool collection's lacking, lol.

JohnBurt

A bolt has an unthreaded portion of shank below the head and a screw (more technically a machine screw) is threaded all the way up to the underside of the head. Full definitions are available on the web.

njee20

They're not though, it's not that clear cut. In fact virtually every source says 'there's no absolute definition'.