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PostPosted: Tue Mar 20, 2018 5:42 pm 
Retro Guru

Joined: Mon Apr 03, 2006 5:11 pm
Posts: 1179
I think this ProFlex has been sitting in a shed unused for 26 years.

When it came to me the chain was rusted (never been oiled?), cables seized and there is some corrosion on bolt heads. Its also a little scratched on the decals etc.

However the cassette and chainrings have zero wear, and the BB spins beautifully.

When I dismantled the pivots and bushings,there was no wear evident.

The original elastomer had melted out as they do onto the rear tyre.

Tyres are the original double smokes, and the fork holds air.

Missing cap off bottom of "shock" but I substituted with a piece of inner tube to keep dirt out. Pedals I would like to keep.

I replaced: Chain, brake pads, cables and elastomer to make it rideable. Seat and post were missing so I replaced with avocet o2 air and cheap post and shim. I greased up the hubs and headset and took it for a spin.

Rides great!

However, time to part with it. As I say this is functionally like new, except for storage damage and some surface corrosion on bolt heads and rear qr lever etc.

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Original Smoke hardly worn + remains of original elastomer....
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Cheap post and Avocet Ti saddle I had knocking about.
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See no wear to teach, and no scuffs to arms, just a little corrosion on bolt heads.
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Brake levers still black!!!
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Fork seems to hold air, see reflector still present on wheel. Front smoke no wear really.
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Melted elastomer and functional brake rocker.
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Cassette with no wear and plastic guard still present.
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Just like the advert:
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£250


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PostPosted: Tue Mar 20, 2018 10:47 pm 
Retro Guru

Joined: Wed Nov 14, 2012 7:04 am
Posts: 411
What did you use for a rear elastomer? How well does it work?


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PostPosted: Wed Mar 21, 2018 8:46 am 
Retro Guru

Joined: Mon Apr 03, 2006 5:11 pm
Posts: 1179
Well.....

As an engineer I wanted to put the correct spring back in. And I wanted it to look right.

The originals used were MCU, micro cellular urethane elastomer.

This stuff is not common anymore, despite being used on every 90's suspension bike.

Most replacement you can get now are made of solid urethane.

MCU has bubbles of air or voids in it, meaning it has very different spring rate and damping properties to solid urethane (and rubber land rover bushes commonly used).

Also but less of a concern here, MCU compresses in on itself, solid urethane bows out- this is a concern for suspension forks with small cavity for the spring.

So I sourced some MCU in the correct dimensions from an industrial supply. This stuff is rare, but used in machines on rollers with give or in pressure forming machines.

As I was only buying a tiny amount, I was stuck with the 90 shore hardness.

This is harder than original, but not a big deal as the bike is not being used as hard.

With this, the proflex is more of a soft tail, taking the edge off trail buzz. But it also bobs a lot less.....


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PostPosted: Wed Mar 21, 2018 12:44 pm 
Retro Guru

Joined: Wed Nov 14, 2012 7:04 am
Posts: 411
I have the suspensionforkparts polyurethane elastomer on mine; a softtail is an accurate description for that as well. Wish someone could find a good source for MCU!


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PostPosted: Wed Mar 21, 2018 2:26 pm 
Retro Guru

Joined: Mon Apr 03, 2006 5:11 pm
Posts: 1179
It can be ordered, but need to order lots of it.

You can buy the chemicals to cast your own, would need to make a former and do some experiments, I just didn't have time.


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