What Are These Adjustment Screws On Wheel Mountings (Hangers??) For?

[Citius]

On bicycles with forward-facing horizontal dropouts, the adjuster screws are only there to accurately position the axle - the axle nuts have to be strongly tightened to stop the axle being pulled forward by chain tension. This is why vertical dropouts exist: a quick-release skewer is not as strong as axle nuts, and so the axle would be pulled forward if the dropouts weren't vertical.

You know those horizontal dropouts are used with QRs, don't you?

 

[snailracer]

You know those horizontal dropouts are used with QRs, don't you?

Sure, but I would only be confident if the QR was of good quality and in good condition, and you were strong enough to really tighten it down. The axle nut is the more foolproof solution.

 

[Citius]

You're missing the point - which is there is no issue with using those dropouts with QRs. The internet is awash with pics of old steel bikes, with those dropouts and derailleur gears.

 

[snailracer]

You're missing the point - which is there is no issue with using those dropouts with QRs. The internet is awash with pics of old steel bikes, with those dropouts and derailleur gears.

Sheldon Brown:
"If you are going to use a quick release with a fixed gear, you should make sure to use a good quality enclosed-cam skewer."

 

[Citius]

Sheldon Brown:
"If you are going to use a quick release with a fixed gear, you should make sure to use a good quality enclosed-cam skewer."

The point is (which I'm making again) - those are not fixed/ss dropouts.

 

[Andy_R]

 

[youngoldbloke]

Rear facing 'fork ends' (the correct term) are used on track frames and dedicated single speed fixed/frames.
Adjustment screws on dropout ends allow you to set up the position of the rear wheel so that it can be easily replaced in the correct position in the dropouts. They perform NO function on a frame with dropouts used as fixed or single speed, other than allowing you to replace the rear wheel accurately in the dropouts. They were a desirable feature on bikes until vertical dropouts were introduced. My first 'proper' bike in the early sixties had 'Campag Ends' so equipped.

 

[snailracer]

The point is (which I'm making again) - those are not fixed/ss dropouts.

OK, what stops them from being used as such? As they have been since (at least) the 1970's?

 

[Dogtrousers]

Sheldon's point about using good quality skewers at the back with horizontal dropouts applies just as much to geared bikes as it does to fixed/SS. You have to be careful to get a decent tension in when closing the QR or you can end up pulling your back wheel out of line while riding. Or at least, that's my experience.

Not that this has anything to do with the OP's question, really. The adjusters just make getting the wheel alignment done a bit easier. I've never had a frame with them I've always thought they were just are a sign of a posh frame.

 

[Citius]

OK, what stops them from being used as such? As they have been since (at least) the 1970's?

They can be used with fixed/ss (as can vertical dropouts too, with a tensioner) - but your assertion that they are designed or intended for fixed/ss use is wrong.

Just take the correction and move on.

 

[snailracer]

...Adjustment screws on dropout ends allow you to set up the position of the rear wheel so that it can be easily replaced in the correct position in the dropouts. They perform NO function on a frame with dropouts used as fixed or single speed, other than allowing you to replace the rear wheel accurately in the dropouts...

Frame makers have no problem accurately placing dropouts. However, the ability to position the axle in different positions along the slot enables chain tension to be accurately maintained as the chain and chainset wears. This function is performed by an eccentric bottom bracket on a SS/fixed/hub geared bike with vertical dropouts.

...They were a desirable feature on bikes until vertical dropouts were introduced. My first 'proper' bike in the early sixties had 'Campag Ends' so equipped.

Well this is making me nostalgic.

Did your bike have the ability to run either fixed/SS or derailleur?

 

[ayceejay]

For 'chain tensioners', like the ones shown to work the wheel axle must go through the hole and the part with the writing on attached to the frame as the screws are turned the wheel is pulled back and the chain tightened and the tension released when the wheel is removed, they serve a different purpose from what the OP shows and only work with track ends.

 

[Pale Rider]

Some hub gear bikes have horizontal drop outs because, absent an eccentric bottom bracket, there is no other way to tension the chain.

Most hub gears have a solid 15mm axle, which if the nuts are kept tight is usually sufficient to keep the wheel in place.

However, the pressure of pedalling can still pull the drive side of the axle forwards.

Bracing the axle from the rear of the drop out is a popular solution.

I wonder if the pic in the OP is of an incomplete version of one of these:

http://en.hollandbikeshop.com/brand...ioner/batavus-chain-tensioner-45mm-bolt-30mm/

 

[snailracer]

They can be used with fixed/ss (as can vertical dropouts too, with a tensioner) - but your assertion that they are designed or intended for fixed/ss use is wrong...

I don't think so. Such frames have been designed so that you can use them either fixed/SS or derailleur. One modern example from the Surly website:

"Rear Dropouts
Semi-horizontal dropouts give you singlespeed compatibility and wheelbase adjustability. Adjuster screws are included to keep your wheel in the right place for optimal shifting if you go with derailleurs."

http://surlybikes.com/bikes/cross_check/frame_highlights

 

[Citius]

Frame makers have no problem accurately placing dropouts. However, the ability to position the axle in different positions along the slot enables chain tension to be accurately maintained as the chain and chainset wears. This function is performed by an eccentric bottom bracket on a SS/fixed/hub geared bike with vertical dropouts.

Chain tension on a derailleur-geared bike is taken care of by the spring on the jockey wheel cage. - it is not something you would need to adjust at the dropouts. Such an adjustment would have no effect anyway.

Well this is making me nostalgic.

Did your bike have the ability to run either fixed/SS or derailleur?

The frame I am referring to was built specifically for road/racing. By someone that knew what they were doing.