ORIGINAL: squeeguk
With the Hyper ST, I have lightened mine substantially. It's now just a little heavier than a X2 CRT. The Hyper ST is still a competitive truck. I was quicker with my ST than I am with my XT8 and am seriously considering changing back.
The only mods I made are milled the chassis, changed to the Hong Nor Super Big Bores, carbon fibre shock towers and centre chassis brace. Other than that, it's stock with the same diffs, etc. I don't think changing the diffs would make that big a difference, but then again, I've only ever driven with the standard diffs.
I am working on making some Ti chassis front and rear braces, the Kyosho ones don't fit straight on the ST. They need to be cut.
If you going racing, stick with the 21, everyone here in the UK uses 21's, better run time and just as good performance, sometimes better as the power is more manageable than a brute 28.
Remember that the Siim is no ordinary Sirio, it has been polished, balanced and slightly reworked and I can tell you now that it is strong on the bottom, not as strong as the Picco, but still very strong, I found them nicer and easier to drive smoother because of the smoother power band than the Picco. Don't get me wrong, I love the Picco's, like I say, Siim are now basing their engines on the Picco's, so you should have the best of both worlds. I can't wait to try one............
It all comes down to your driving style and what suits you best.
that makes sense UK and North America have very different style of tracks.... Here we have huge jumps with short runs to them, in a big rig like a Hyper you need punch......When I ran my Hyper on a flatter track it did good, but when i ran it on a Supercross style track it didn't do so well..... Sirio's are notorious for breaking cranks, which is why Siim now are Nova based.......