RX100 dual pivot caliper.What is the small adjuster screw for?

[Paulus]

I throw myself on the collective here.
I have had the bike from new, 26 odd years now, with these RX100 dual pivot brakes. But, I have never known what the adjuster screw on the top actually adjusts as I have never touched them.
Can someone please enlighten me.

 

[Ian H]

To align the brake blocks, set them equidistant from the rim.

 

[Paulus]

To align the brake blocks, set them equidistant from the rim.

Thankyou. So it is of a centering adjuster.

 

[Ajax Bay]

it is a sort of a centering adjuster.

For the sophisticated. Like my bike of similar age to yours, but only 10 years ownership, my RX100s (which btw have a useful drop cf 'groupset' calipers) have (mostly) stopped me on demand. I have centered them when needed by brute force. As, I assume, have you.

 

[Paulus]

For the sophisticated. Like my bike of similar age to yours, but only 10 years ownership, my RX100s (which btw have a useful drop cf 'groupset' calipers) have (mostly) stopped me on demand. I have centered them when needed by brute force. As, I assume, have you.

I have centered them by moving the main bolt with an Allen key and moving the caliper with the other hand, the old fashioned way.
They are very good calipers with lots of stopping power.

 

[si_c]

I have centered them by moving the main bolt with an Allen key and moving the caliper with the other hand, the old fashioned way.
They are very good calipers with lots of stopping power.

Yeah that'll work too but it's easier and quicker to centre using the screw. Basically it adjusts the spring tension which moves them left or right as needed.

 

[Yellow Saddle]

I have centered them by moving the main bolt with an Allen key and moving the caliper with the other hand, the old fashioned way.
They are very good calipers with lots of stopping power.

That screw would give you fine centering adjustment once you've centered it as you described. Important note, that screw is not philips, but JIS (Japanese Indiusgtry Standard).

Like this: https://www.sealey.co.uk/product/5637750680/jis-screwdriver-set-4pc

Doing the centrering screw wil a philips driver will either mess the screw or the driver. Especially if it is a tight as they normally are.

The set will not be wasted, it'll allow you work on Japanese cars and motorbikes and cameras and all sorts of Japanese products none of which I can think of now.