raise a glass to the CVA shock

[Saito2]

I was rebuilding some CVA shocks yesterday when it dawned on me just how long lived this particular part (in one form or another) has been around and how well it still works. Until the Hicap came out, they were THE Tamiya oil filled shock from the Fox onward, a signifier that the buggy/truck they were on was a bit more than the usual basic fare. After messing about with earlier unique designs, Tamiya bought out this simple, yet effective shock to use across the board, adjustable and functional.

I remember how the magazines would commonly swap these out for metal bodied options whether it be Kyosho, Associated, Trinity, etc. Their reasoning often being that the Tamiya CVA would expand due to heat from use making dampening inconsistent. I my head, I often wondered if this wasn't partly the author trying to explain his need to put a little bling (before bling was a thing) on a project car (while tossing another manufacturer's product into the discussion). They fact was, many of those aftermarket options didn't fit exactly right and I have a feeling the more pedestrian CVA worked just as well (while fitting our Tamiyas perfectly) unless competing at higher levels.

Today many of those better quality metal shocks are gone. There's an abundance of not-so-good quality metal bodied shocks available from the far east. They look cool, are cheap and tempting but as many have found, the old CVA (1 or 2) was just fine (and often better) to begin with. If I go through the collection of shocks I've amassed over the years many of those metal ones aren't in the best of shape. Some have captured o-rings making rebuilds impossible. Every CVA I own, regardless of the version only takes a couple red Tamiya o-rings and maybe a bladder to make it feel like new. Sure, there's times I'm tempted by something with flashier looks. I miss when the yellow variants were more common as the  black ones are a bit boring to look at for me. It would be nice if Tamiya simply offered the bodies in a variaety of colors all the time. In the end, the CVA does its job well IMHO, despite the need to cycle them a few times to un-stick them if they been sitting for awhile . 

 

[ThunderDragonCy]

Agreed. 

[SuperChamp82]

+1 

How do TRF (or other Tamiya aluminium oil filled) dampers influence what you’d buy though ?

From memory, they’ve been around for quite a while and, for me, beat the CVAs - albeit at increased expense ?

Completely agree most third party metal dampers under perform vs CVAs 

[speedy_w_beans]

So I'm going to play devil's advocate a little bit and suggest CVAs are an improvement over spring holders/friction shocks, but they really aren't that great compared to TRF dampers or even Yeah Racing Shock Gear stuff.  Here are my reasons:

1. Generally the seal between the piston and damper body has more gap than the TRFs or Shock Gear parts.  This means as the piston moves up and down, fluid is bypassing the piston holes and leaking around the piston itself.  I've built onroad CVA dampers with both regular CVA pistons as well as TRF-type pistons that are slightly larger, and the damping action is very different between the two.  CVAs with TRF-type pistons actually feel closer to TRF dampers.
2. The piston holes themselves are quite large, so while the damping action is relatively linear depending on oil thickness and shaft speed, they don't develop any "pack" or nonlinear damping in response to faster shaft speeds.  Basically what this means is they don't help prevent chassis slap when landing jumps on offroad tracks.  You can put thicker oil in a CVA to help with a jump, but then the chassis is way too twitchy over washboard surfaces.  Or, you can run thinner oil to handle the washboard, but then the chassis is always slapping (and losing speed) on landing a jump.  Any race-spec chassis from Associated, Kyosho, or even TRF will have several piston hole sizes available so you can more easily accommodate both jumps and washboards.  Having those options to work with piston hole count, piston hole size, and oil thickness provides more tools for tackling different scenarios.
3. The CVA bodies aren't threaded, so there's no fine adjustment to dial out chassis tweak, set ride height, or balance corner weights.  You can install some shims on the damper shaft to complement the clips installed on the damper body, but it's not as easy or adjustable as a threaded damper body.

Don't get me wrong, CVAs are definitely an improvement over friction dampers and they function fine for casual driving.  They're noticeably better than spring holders, are relatively inexpensive, and are pretty easy to maintain or rebuild.  If you do any car setup or any racing, then they're not the right tool for the job.

Here's where I did some work on CVAs in the past:

 

[Saito2]

Oh I agree with what you've noted @speedy_w_beans. The CVA is not the shock for every job. Sorry if I seemed like I was trying to make them out to be better than they are. For workhorse, basher type duties they suit just fine and are often better than cheap alloy Ebay shocks. They last pretty good in my experience and can always be cheaply rebuilt. Blingy alloy shocks have come and gone but the basic CVA is still around filling its role. There are plenty of better shocks out there like TRF units that aren't simply about bling.

[ruebiracer]

Agree with all of you. @Speedy: Even Tamiya noticed, that the CVA have more potential with some hopups.

In the M08 I´m still running them, as Tamiya tuned them for the first time (correct me if I´m wrong) with TRF Piston rodss and the TRF bladders. Smooth as silk. Was running them my first races with 400 oil and the kit pistons. Last time on black carpet I needed more damping without wanting to use 900 oil (which is Tamiya´s solution for compensating the greater piston bypass on the CVA plastic pistons), so I threw in some 3 hole TRF Teflon pistons and 450 oil. No need to switch to TRF shocks at the moment. If I feel the need, then only for the finer adjustment by the threads. Using the TRF bladder does 2 things: reduce rebound by less rubber stiffness of the bladder itself. Second: outer diameter is smaller, so you don´t unsettle the bladder when closing the shock and bringing air into the oil, which can be fussing on sometimes on the CVA´s. (But also on Rere Hicaps and TRF 419 Big bores)

Well done, Tamiya! Cheers!

 

[ThunderDragonCy]

Have to say one thing I noticed when tuning the RR03 was that it was way easier when I converted the rear shocks to a mini body with extended rods (not possible on a buggy, but worked here) because I could even up the damping performance front to rear, and use the 10mm TRF pistons front and rear. The rear CVAs being 11mm is seriously limited for the buggy side of things.

[SuperChamp82]

@speedy_w_beans is spot on

And it’s the manufacturing tolerances underpinning each of his points that also blights a lot of third party bling 

For me, Yeah Racing are the only outfit producing $ vs $ improvement vs CVA ... and even then the threads give way too quickly / they’re ultimately best suited for the shelf 

If you step back, Tamiya may have made a mistake making CVAs relatively expensive over time ? 

Especially when a few $ more buys you a TRF set that will out perform it by a country mile 

[ThunderDragonCy]

This got me thinking. CVA shocks are clearly pretty good with a couple of flaws, and particularly with the front shocks on buggies they are a somewhat unique length and stroke, even compared to higher end tamiya shocks. I have a friend who owns a machine shop that does some work for me in my day job. I knocked up a basic drawing of and alloy, threaded body for a CVA rear shock, using all the stock part except for a 10mm bore (for the reasons mentioned above). For a run of 50 pairs, they would be around £20 a pair. You would thrn need trf pistons and sone threaded collars, so it probably gets a expensive overall, but with mini length hicaps being so thin on the ground, do you think this might work? For things like the Top Force and Super Astute it would mean great shocks using kit parts. 

[Jonathon Gillham]

5 hours ago, ThunderDragonCy said:

This got me thinking. CVA shocks are clearly pretty good with a couple of flaws, and particularly with the front shocks on buggies they are a somewhat unique length and stroke, even compared to higher end tamiya shocks. I have a friend who owns a machine shop that does some work for me in my day job. I knocked up a basic drawing of and alloy, threaded body for a CVA rear shock, using all the stock part except for a 10mm bore (for the reasons mentioned above). For a run of 50 pairs, they would be around £20 a pair. You would thrn need trf pistons and sone threaded collars, so it probably gets a expensive overall, but with mini length hicaps being so thin on the ground, do you think this might work? For things like the Top Force and Super Astute it would mean great shocks using kit parts. 

They sound great but I think the price is just too high. I know thats what they'll be costing and there is very little, if any, profit in it for the manufacturer. People may pay that for the set of fronts that look like hi caps to get the right look, but I would spend that on a set of hi caps or TRF shocks for a buggy.

The Avante and Egress come with mini hi caps right? But they are impossible to find outside of a kit, so things like the Super Astute get converted to the Dyna Storm front tower and long hi caps?

[ruebiracer]

1 hour ago, Jonathon Gillham said:

They sound great but I think the price is just too high. I know thats what they'll be costing and there is very little, if any, profit in it for the manufacturer. People may pay that for the set of fronts that look like hi caps to get the right look, but I would spend that on a set of hi caps or TRF shocks for a buggy.

The Avante and Egress come with mini hi caps right? But they are impossible to find outside of a kit, so things like the Super Astute get converted to the Dyna Storm front tower and long hi caps?

Avante and Egress fronts are still available, even for some years now at Seidel. Sometimes the Avante tuning pair for the front was sold @30€ including the carbon front shock tower. The rears I built from single spares for my Avante ´89, as they were sold out as pair for some time...

Just search for "egress", and you find the spare parts. rod guides are by the way 100% re re Buggy champ Guidings. So if anyone complains them leaking, he might have a Problem with overfilling, or does anyone complain about the re re Hi Caps leaking?

[Jonathon Gillham]

46 minutes ago, ruebiracer said:

Avante and Egress fronts are still available, even for some years now at Seidel. Sometimes the Avante tuning pair for the front was sold @30€ including the carbon front shock tower. The rears I built from single spares for my Avante ´89, as they were sold out as pair for some time...

Just search for "egress", and you find the spare parts. rod guides are by the way 100% re re Buggy champ Guidings. So if anyone complains them leaking, he might have a Problem with overfilling, or does anyone complain about the re re Hi Caps leaking?

Interesting, just had a look.  So Egress front and rear damper bodies are 30 euros, that would be the main parts required to convert a Super Astute to nice alloy shocks right?  Could probably use kit CVA parts for some, and maybe have to buy a few bits to complete them.  Much cheaper than Top Force hi caps (which seem thin on the ground now) and a Dyna Storm tower.

[ruebiracer]

22 hours ago, Jonathon Gillham said:

Interesting, just had a look.  So Egress front and rear damper bodies are 30 euros, that would be the main parts required to convert a Super Astute to nice alloy shocks right?  Could probably use kit CVA parts for some, and maybe have to buy a few bits to complete them.  Much cheaper than Top Force hi caps (which seem thin on the ground now) and a Dyna Storm tower.

In principle I tend to say "yes". If you have some shock parts left, it´s probably not much more expensive, but the small parts like the guidings, bladders and mounting balls etc. are adding some Euros. As the Top force Hicaps (4xshort) are also available at the moment (search for "hi cap", 49€ for the TF set), I probably would go the route to buy the top force set and a set of the mini bodys. Maybe sell some parts from 2 shorts, like the bodies, piston rod, springs and so on. Guidings are totally identical short to mini, plastic parts tree with pistons and spring collars have different sizes, so you would need that anyway in the mini version. It´s some work with manuals and digging out the parts, but seidel is a quite good library regarding Tamiya parts. You search "Kolbenstange 31mm" for example, ad you get a list with all piston rods in that length range, and each part is marked with a listed of compatible cars, which is true in 99% of the cases. They have done an outstanding job over the years, in my eyes, to collect all these data and bring it into the web...

Kind regards,

Matthias

[Hobgoblin]

I am unfortunately guilty of falling for the fleeting charm of Shenzhen Special. My Manta Ray came with one pair of yellow CVA (no oil!) and one pair of horrible yellow Kyosho things that were sloppy and stiff at the same time. I changed them out for a £15 alu set which came in a beautifully fetching purple but were ultimately a bit naff. After about a year of fiddling and fettling I've elected to call it a day and I've got some Tamiya CVA's waiting at the post office for me to pick up on Friday! Hopefully they'll be what I want (or else it's hicaps )