Fitting Replacement Risc PC Rubber Feet

by David Thomas on

If you have a faithful Acorn Risc PC kicking around you might have found that the rubber feet on the bottom of the case have started to crumble, like mine:

A close-up picture of the underside of an inverted Risc PC with a crumbling rubber foot.

In some cases the rubber feet can even liquefy and leave you with a wonky computer sitting in a pool of grey goo.

You’ll be pleased to know that you can lever off the old ones and replace them with a new set of Bumpons (that’s what they’re called) from 3M.

A grid of 4x3 new rubber bumpons.

The specific ones you want are 3M Bumpon SJ5023 in grey. They’re 20.5mm² wide by 7.6mm high. The datasheet is here. I bought my replacements from an eBay seller. Note that the greys seem harder to find than the black and clear variants. [2021 update - RS have them:].

Once you have your replacements, start removing the broken feet. Avoid damaging your antique computer by working a blunt knife in at the corner closest the edge. Then push up to lever the old foot out.

A close-up picture showing the removal of one of the crumbling rubber feet from the underside of a Risc PC.

This is made easier since the holes for the case locking pins go right through the case and leave a void under the foot; the bumpon’s flat base never entirely adheres to the full square.

An inverted Risc PC with a single rubber foot removed. Old glue remains.

Once removed, clean the old glue off using some isopropyl alcohol. I used a toothpick too for the harder gunk.

Applying isopropyl alcohol to remove the old glue.


With the rubber foot and glue removed the aperture is now clean and ready for the new bumpon.

Then you can peel off the new feet/bumpons/tapered squares/trapezoidal prisms from their backing paper and fit them:

The Risc PC on its side showing four new rubber feet fitted.