kcash

Hi all,

I'm planning on putting some adjustment screws in my rear horizontal dropouts. My question is: does the Phillips screw side (the end on the left of the picture) go on the inside of the dropouts or the outside? If they are on the inside, I suppose I would need to use some thread-locking stuff on the caps (right side of the picture) so that I could use them to make some adjustments.

FBinNY 

They're designed to be threaded in from the inside of the dropout slot, and out the back. Then you add the knurled nut as a finger adjustment aid.

The spring stays on the screw when you thread it, so it ends up on the part in the slot.

BTW- the best way to get the knurled nut tight enough is to put a wheel in, so the screw can't move and force the nut a bit.

Here's a trick from back when these were in common use. Once you have the wheel set where you like it, either cut the remaining screw off flush, or at least shorten it so the nut only has a bit of room between it and the dropout. This lessens the chances of the screw getting bent accidentally. Trying to remove a bent screw,(even slightly bent) is the number one way folks break the screws off in side, and/or strip the dropout.

kcash

Thanks for the tips. I'll try to avoid getting the screws bent.

FBinNY 

That's almost impossible, so reconcile yourself to it. Just remember to move the screw backward so you can cut off the bend, before trying to remove it.

pmt

You know, I've never understood this. If adjusting with the knurled nut, you'd only be able to move the adjusters further in toward the BB; trying to move them away just unscrews the nut. Then you have to take the wheel out and awkwardly use a screwdriver to adjust them, IF the head of the screw hasn't been deformed by banging the axle against it when a wheel is inserted.

It makes a million times more sense to put the Phillips end on the outside, and the knurled nut on the inside. I can't help but think that the "right way" was a mistake fifty years ago and somehow stuck.

Mark Kelly 

In theory maybe but in practice it works fine as long as there is some lubricant or antiseize on the dropout thread.

As FB says above, the trick is to "set" the screw head by tightening it against the axle. A drop of loctite medium strength doesn't go astray either.

johnlink

I agree. And doing it the "wrong way", is there any need for the knurled nut?

pmt

It's probably better to have the knurled nut against the axle than just the end of the machine screw.

johnlink

I think that's right. I just installed the rear-dropout adjustment screws including the knurled nut the “wrong way”.

Crankycrank

These were designed to have the knurled nut on the outside making the screws easier to turn. You don't need bullet proof ends against the axle as it only serves as a stop when mounting the wheel and it's job is done once the quick release/axle nuts are tightened. You certainly could reverse the screws with no issues but it's just easier to twist the knurled part by hand. And use grease or anti-seize on the threads and give them a few turns every year or so to keep them from corroding and getting stuck in the dropout threads.

johnlink

I changed my mind and reinstalled the screws the usual way.

pmt

Well that's too bad. I can't think of a single situation in mechanics where something is continually impacted against a small screw head; that simply doesn't make any sense. It also makes no sense to have to remove the wheel to adjust them if they gets a little stuck, and we all know they will get a little stuck over time, since the vast majority of bike owners aren't going to do maintenance on those screws on a regular basis.

Unless someone can find the original history of those dropout screws, I think we can be assured that some Pro back in oldyn tymes installed them incorrectly (with the screw heads on the inside of the dropouts) and the fanbois followed suit, making it the mechanically incorrect standard. Maybe the Pro thought it looked better or cleaner, and didn't care that it was mechanically silly to have it that way.

JohnDThompson 

Well, it's not "continually impacted." Once the hub axle abuts the bolt end, it is secured in place by the quick release. If the QR is loose enough to allow continual impacts, the wheel would not be secure in the dropouts. I have dropouts with adjuster bolts installed in that manner that are going on half a century of use, and they're still in fine shape.

BCDrums

I maintain the dropout screws regularly, every thirty years. I took them out of the dropouts for the first time this year to make a little more space for a larger tire at the chain stay bridge. They came right out. Later I put the screws back in, after greasing them. No issues. I restored the nubs on the outer ends, tightly. And for the first time, I realized that I could adjust the screws from the outside of the dropout with the nubs. A revelation!

I'm sure that your theory is correct. Some old Italian probably, maybe his name was Tullio.



He looks pretty pissed off about this.

Fanbois, is that French? Pronounced fan-BWAH? Have a nice day.

johnlink

Which way does Tullio think they ought to go?

johnlink

Which would do a better job of protecting the threads of the axle, the smooth surface of the knurled knob, or the less smooth surface of the screw head?

Crankycrank

I'd say they're both about the same for the job the screws do. Again....once you've positioned your wheel against the screws and clamp the quick release the screws job is done and provides no other function so there is no banging on the axle threads. I rode bikes with adjustable dropouts for 30 years and worked on many others and never came across a bike with dinged up axle threads from these and maybe only once or twice were the screws mounted backwards (knurled heads in the dropouts) by inexperienced owners. One advantage of the screws is that if your wheel or frame got bent in the middle of a ride you can adjust the droupouts so the wheel doesn't rub the frame with the wheel in place so you know how far to adjust it. Try that with the slotted screw end outwards and bare fingers. I also can't remember this ever being debated but if anyone wants to mount the screws backwards I doubt it will hurt anything or anyone will notice either.

JohnDThompson 

Well, from early Campagnolo catalogs, it appears that the head of the bolt goes inside the slot:

pmt

That settles it! The Campagnolo catalog is about an authoritative reference as there could be.

Still doesn't make any sense mechanically, but since we can see what the originators intended, so be it.

alcjphil

If the diameter of the knurled knob is greater than the thickness of the dropout you might not be able to properly tighten the quick release