ATZ forks for my Swiss Cilo Mountainbike

Without getting too scientific, which would push the boundaries of my own physics and chemistry knowledge quite quickly, an elastomer is a type of polymeric material that can be repeatedly stretched beyond its original length with little or no permanent deformation. It can also be compressed repeatedly and still return to its original size and shape. This makes it really good for products like suspension on vehicles and specifically for this post, was the core suspension property found in early suspension systems for bicycles.

Over time, elastomers lose their unique properties and go very hard, rendering them useless for damping duties. Some people say that you can bring old and hard elastomers back to life by putting them in hot water…………?

If you search ‘Elastomer’ in your chosen e-music provider, most of the tracks that carry the title are by late 1990s Techno bands. However, there was one that I listened to all the way through and it was by a band called The Flashing Astonishers. You should give it a listen as well.

Anyway, back to suspension bounce. I was ‘lucky enough’ to have some elastomers delivered in the post the other day. It’s not every day that I get a treat like this. In fact, they had been made specifically for me, my weight and their final destination, which is on a very special pair of early Swiss, ATZ mountain bike suspension forks that I have.

A lot of early suspension forks used a mix both hard and soft elastomers to provide the right damping result. However, in comparison to today’s suspension, they are not on the same performance level, but when you didn’t have any suspension at all, they were a big innovation, even if they did go hard in very cold weather!

The suspension forks that my new elastomers will be fitted to were made by a brilliant Swiss engineer and innovator, Francis Glatz. More about Francis and his life as an innovator in a future interview post. These forks proudly carry Francis’ ATZ brand, are made of magnesium and were cast in Italy prior to their assembly in Switzerland. In the mid-1980s, these forks were cutting edge and were used to great success in international races. The first prototype of these forks was actually made in carbon fibre, but a move to magnesium was made for production.

This type of Swiss suspension fork was used in the World Cup events and fitted to a Swiss Cilo mountain bike, similar to mine. You can read about an incident with a bear in one of these races here https://diaryofacyclingnobody.com/cilo-mountain-bikes-and-bears?/

I was lucky enough to get these forks from a friend, and although they had a few unobtainable parts missing, it didn’t stop me from making a quick phone call to their designer, Francis Glatz. He said ‘bring them over and I’ll service them for you’. Excitedly, I jumped in the car a few days later and drove over to Francis’ place so he could service my forks, tell me exactly how to fit them, and set them up. 

Francis replaced all of the bushings, provided the missing parts, but he didn’t have any replacement elastomers. This led me to find John Deverill’s site on eBay, and after a couple of emails and pictures, he made me some. Because these are not ‘off-the-shelf-parts’, John made me two sets of elastomers with different ‘bounce properties’ to have a play around with. There’s a link to John’s site at the bottom of this page.

Fitting these ATZ forks is quite simple, although this paragraph might not sound simple or interesting to some readers, but here goes anyway; The front brakes are removed and then the original forks fitted to the bike are turned around 180 degrees so that they bend backwards, instead of forwards. The old elastomers where removed from the ATZ forks so that the linkages pivoted loosely, and then they’re connected to the bikes original fork legs at the bottom, and where the wheel axle would originally lock in. There is a single bolt on the top of the ATZ forks which then fits into the hole in the crown of the bike’s forks. Care must be taken now to ensure alignment here, and Francis gave me some good advice and shims to help do this. With the forks in place, the brakes are put on the ATZ forks, and then the new, colourful elastomers get fitted. The bounce factor has now truly been introduced to my rigid, Cilo bike. Clear? Have I used the word ‘forks’ too many times in this paragraph? 

These forks also have a very basic lock-out feature, which require an additional control lever adding to the handlebars. By pushing this lever forward, a cable limits the movement of the forks so that they can be (almost) stopped from moving up and down. Pulling the lever back releases the cable and allows the forks to move up and down as the elastomers soak up the bumps.

The December test day dawns grey and cold, and as sung by the White Stripes, Autumn’s ‘dead leaves are on the dirty ground’, which are crisp and white with the frost. The roads are half dry and half wet with black ice sections. The (reliable Swiss) weather forecast says ‘snow at 13:00’ so I head out for a lunchtime ride at noon. I’ve got just the ride thought through to quickly test the bike and it’s new bouncy bits, which is a third road, a third gravelly and rocky track, and a third single track.

On the road, the front doesn’t bob up and down too much. It also doesn’t dive violently or bottom out hard under downhill breaking. My ultimate elastomer test was a descent on an ancient cart track that is full of shiny and slippery rocks, some of which are like icebergs with just the tops being exposed and the rest being all loose. On a modern full suspension bike, I can hammer down this track. On this bike, it requires a line to be carefully picked, or it will get painful and messy.

I rode this old track on the bike prior to fitting the ATZ forks, which wasn’t fast and more ‘slow trials’ than ‘downhill racer’. I must admit, on this second suspended run, I was really impressed with the way the forks worked on this track, and so much so, I went back to the top and rode it again with a mid-track-photo-stop thrown in to capture the moment. 

At this point, you maybe saying ‘so what?’, so let me sign off with a summary. Like a lot of people, I’m looking for great cycling experiences and this one has provided me with some engineering education, an MTB suspension history lesson, a meeting with the innovator who designed these forks, the sourcing of some replacement elastomers that work really well, and finally, getting the chance to re-create and ride a Swiss built, early suspension bike. 

If that’s not enough of a ‘great time claim’, you can also check ‘Elastomer’ as written and sung by The Flashing Astonishers.

Finally, if you need some elastomers for those early suspension restorations for forks like Pace, Manitou, Halson, Votec etc, you check out John Deverill’s site here https://www.ebay.co.uk/itm/Pace-RC35-MCU-Elastomers-also-other-forks-Rockshox-Manitou-Halson-Votec-etc/184524498964?hash=item2af6846814:g:nuUAAOSwhaZeZKnk

Update to this post: I recently visited Francis Glatz for one of my ‘Interesting Interviews’ and he’s fitted a new set of the original elastomers to the forks and also set the suspension up so it operates as it should. I’m a very lucky boy?

All photos by the Author