[Closed] Old marzocchi forks for a kids bike?

They don’t work that well with superlow pressures required at kids weight. It’s probably due seal friction?

I recall that rider weight needed to be about 50kg before fork started to work properly.

They don’t work that well with superlow pressures required at kids weight. It’s probably due seal friction?

Not sure if you were referencing this specific fork, or suspension in general, but it does depend on the fork being considered. I know that 90% of forks I see on kids bikes are just weight for them to push around, rather than something that will improve their riding.

My son is just over 25kg and runs some Fox 32 Factory forks which I picked up on the Bay for around £200. I shortened them to 80mm travel and use thinner damper oil than would be normal and they work an absolute treat. I think in this case, new seals (which I fitted when I bought them) and the Kashima coating really help to keep the friction low so the fork is responsive with his relatively light weight. That and running them at very, very low pressure indeed! 🙂

We had some Marzocchi X-Fly forks that were the best forks for our kids of all of them that we had. Nice and plush, easy to drop new oil in, looked and shiny silver and bling. 8)

The Fox's were good - but you were up against low pressures in them. Simple service. Don't get the TALAS, they just are not as plush.

The Manitou Mars were nice and plush, but even with kid on board you can see how flexible they are. No spares when the seals wore out....

as a lightweight adult* i would not have any fork that was not air as some of them are literally useless at my weight- i can barely move them even doing moderate drops [ 8-12 nches ]. At the lower weights of a child this will be even worse

you may be able to get it work using lower viscosity oils but basically a fork designed for the weight of an adult wont work with the weight of a child hence you need the adjust ability of air

* middle of the BMI for my height which is skinny these days apparently.

I think the issue with some of the cheaper Marzocchi's is that the air spring wasn't particularly sophisticated, so might not be great at low pressure.

Some older dual air Rockshox might work, as you could pump up the negative air chamber a bit more to make them more supple. If you give them a lower leg service and soak the foam ring in oil they should work well?

I think the issue with some of the cheaper Marzocchi’s is that the air spring wasn’t particularly sophisticated, so might not be great at low pressure.

I think that's true of the slightly later forks (Z1SL, AM1/AM2 etc), but in reality it was actually worse for heavier riders as they were 'air assist' so lighter riders got the lovely coil sprung plushness, but as soon as you added air the seals tightened up and the whole fork became rock hard.

But the earlier ones were great because there was no seal.  The air pressure just acted directly onto the oil bath and all the sealing was done by the oil/dust seals on the legs. I had Z4's (the ones with a cast arch but still 3 piece lowers) and later some MX-Pro's (which as far as I can tell were still the same just in a better chassis).

I did look at older (late 90s/early 00s) 28mm SIDs which come in an original 63mm travel version and are nice and light, but prices seem to still be a bit on the high side due to the potential retro/kids bike market...

And I did eye up some early 00s Float 30s again these go a bit pricier and being older foxes I could foresee potential stanchion wear and other issues, plus they also seem to attract a premium and I didn't want to spend too much on this.

I think the issue with some of the cheaper Marzocchi’s is that the air spring wasn’t particularly sophisticated, so might not be great at low pressure

To me that's precisely the benefit for this use, these are about the simplest fork Marz ever made, to make them a bit more responsive I could go as low as 2.5wt oil (stock was 7.5wt IIRC), possibly a reduced amount to increase the spring volume slightly, plus being air sprung I have pretty much infinite spring adjustment.

To clarify here, we're not talking about an advanced rider who's going to hucking Gnats and blasting through rocks and roots, She's 9 in a few months and likes a relatively sedate ride...

For £20 it's a worthwhile experiment, they are a bit heavier that I would like, I'll see what I can do about that later...

[quote="junkyard"]as a lightweight adult*

*makes obvious joke about being a vegan*

To make Old Marz air forks work well, drop all the pressures for pos and neg air springs. The manuals alway gave  v high pressures for all the cambers.

I run a set of AMSL1’s at at about 23psi with the Par spring set at 9psi. Which give me about 30% sag and lots of small bump sensitivity.

I think My old ones were Z5 Flylight 80's, which I upped to 100 with a change of top out spring, the only real difference was they had a machined out lower leg brace (bolt on jobs) I've had 32mm All mountains, Z1 Drop offs, a couple of pairs of 30mm MX comps and I think I've still got a pair of ~15 year old 32mm old DJ3s in the Garage with a busted air valve on top of one leg, IIRC I did at various point run those with a single coil spring/no springs and even as just Air forks, if I could find a cheap replacement top cap those would be a workable fork. But I'll probably just pull them apart, individual parts for old Marz forks now seem to be popular on fleabay...

I never had any issues with sealing or stanchion wear on any of these forks, and I generally found them all plush/compliant enough, the damping being basic simply means they might get swamped on rougher trails but TBH it's not really a concern right now.

These days I'm riding a solo air Reba which when you get down to it is a pretty simple fork too...

As said above, you can take a coil spring out and just run one spring. I have a set of z1s that work better with one spring and more air.

My reply was specific to Z5 as that was the model we tried. Damping oil was mix of 2,5w and 5w.

Older coil ‘Zocchis worked well because they had springs in both legs - just remove one and and you had fork fit for kids.

Well I'm pretty sure the one's I have coming are some flavour of Z5, possibly 98/99ish, silver lowers with the non-machined (heavier) brace.

I recognised the chromed stanchions and what looks like the same caps for aid valves, the description mentions that they still hold air, but doesn't say if they're air or coil and air... Either way I reckon they can be softened and shortened for use by a child...

Well they turned up and they are 80mm travel, Z5 flylight airs date stamped 99.

So I've just spent a very familiar half hour stripping them down.

They hold air but the RH wiper seal has started to perish, so I'll be getting a new seal kit (turns out there is an Enduro low friction kit available...

And while they're apart I'll reduce the travel and do a rattle can respray of the lowers to match her frame...

I reckon these will be a goer...

Try running them with all the pressures lower than the manual says. Are they all air? As you might be able to reduce the travel by using the negative air spring

There is no negative air spring, there's a top out spring, So I'm just planing to add a spacer or another longer top out spring to lower the ride height, ideally by about 25-30mm.

I should also be able to reduce the oil volume, I found the old tech manual online and notice it says to run 15cc less oil in the 80mm than the 100mm travel version, so a similar proportionate reduction would make sense, possibly a bit more to increase the spring volume, I did notice when I drained the fork it appeared to have been over filled with oil in both legs and the old oil has clearly thickened up a bit...

One thing I might do is just run it with one leg pressurized at ~15-20psi, and possibly vent the other leg whin compressed so that a full extension it's pulling a slight vacuum (I did something similar with my old DJs), that might help overcome any initial stroke stiction a little, a similar effect to a negative spring...

I reckon I can milk some sensitivity out of these things...