Your TD4 Big Bore shock settings

[BuggyDad 5926]

Big Bores for my TD4 finally arrived. For those who are running them, I'd be interested to know your choices of oil weight, pistons and springs? Partly I want to start from a decent position but partly also I'm not great at tuning knowledge. I'd like to optimise it for outdoor astro, since its first significant running, if the diary stars align, would be at a Tamiya Junkies meet. 

[G-rem 5]

Hi BuggyDad,

a bit off-topic (sorry for that) but maybe you can help ? I can delete the post if not relevant   

On 4/4/2024 at 2:22 PM, G-rem said:

I'm very interested in Tamiya BB aeration dampers for a custom Tamiya project based on WT-01 chassis but I'd like to know if you can tell me several additional measurements :

- could you please tell me both for BB front & rear the length from upper cap to lower body of the shock, like so : 

 

- you also disclosed the front & rear travels for these shocks, but I would be interested to know if I can put rear shaft with the front body shock (and vice-versa) and see what Eye-to-Eye measurement and travel I would get ? Otherwise : when genuinally built like you did, is the top of the shaft hitting (kind of) the top of the cap ? Or is there still room in between, meaning using the rear shaft in the front body would be possible without too much compromising the eye-to-eye distance and / or the travel amount when built like so ? Not sure if I'm clear...

 

Thanks in advance !

G-rem

[BuggyDad 5926]

1 hour ago, G-rem said:

Hi BuggyDad,

a bit off-topic (sorry for that) but maybe you can help ? I can delete the post if not relevant   

 

Thanks in advance !

G-rem

Hey, that's OK, I can measure them for you, but at the mo they are still in the packet so I'll need to assemble them first, which will probably be next week. 

While I'm doing it I can swap a rear shaft to front to test but I'd expect you to need some spacers to stop the piston/shaft hitting the cap. So by adding a longer shaft to the front I expect that you'll increase uncompressed eye-to-eye by the increase in shaft length, but travel you probably won't be able to increase by much. 

[BuggyDad 5926]

@G-rem I assembled them this evening. The measurement you drew in red there is 50mm on the rear and 41.5mm front. 

The shafts are 49.6 and 40.7mm. So a difference between them of 8.9mm.

This pic shows both assembled stock and compressed to the point that only thread is showing:

So each shaft is close enough to bottoming out that I guess you would only increase travel by up to max about 3mm by going for a longer shaft. Maybe 4mm in the front. And that's to hitting the cap, which you probably don't want to do. 

Here are the rear then the two front shocks with short then long shafts in for comparison. Fully extended:

Eye to eye is 93mm rear, 76.5mm front and 85mm for the front with the rear shaft in. 

And fully compressed:

Compressed they are 65mm, 57.7mm and 62mm (that last one gets to the above c.3mm shorter than the rear because it's fully bottomed out into the cap). 

Edit: so this means travel is

Rear: 28mm

Front: 19mm

Front maxed out with a longer shaft: up to 23mm (but probably not sensible to go to the extreme)

[G-rem 5]

Hey BuggyDad,

that's amazing, thank you soooo much for taking those measurements ; that's perfectly what I needed to know

Big thanks !

G-rem

[BuggyDad 5926]

One question I had was why do folk often start with harder damping settings front than rear? 

The shock travel numbers above give a possible answer, since wheel travel is not far different front to rear yet shock travel is about 1/3 less, so leverage ratio on the front shock is much greater. Ergo, for damping at the wheel to be the same you'd need about 1/3 more damping force in the shock. I guess this simple point would explain it? Combined with less weight on the front meaning there's perhaps less downside to simply levering up on the shock and increasing its damping to match? (hmm maybe not that - that would be cancelled out by the leverage ratio) Are buggies built with shorter front shocks for aesthetic reasons alone?