I should mention here that the first thing I do with any suspension bike is set only the preload and rebound damping. I run minimum pressures on reservoirs and back out all compression damping because I like to get a good feel for what the frame itself is doing independently of the damper. I had to back off the boost valve a good bit to achieve this.
The first thing I noticed on the few rides out with the shock set this way was something Specialized has also been doing lately with a lot of their frames, basically ‘opening up’ their suspension. The swinglink that drives the suspension floats a lot more than a lot of other designs and pushes essentially straight into the shock. The same complaint I had with the 4” SX frame I reviewed last year applies to this one, too: the frame is far too linear throughout its travel.
I can get into the right sag range out of this spring with a tiny bit of preloading, but on the trail, the bike was just squatting way too much anywhere I wanted to pump. Some people like this kind of ride (Hi, Nomad Nation!) but I can’t stand it. Giving up the travel too easily leaves far too little of it when it really matters, and generally just feels like riding a dead marshmallow when trying to accelerate out of turns, preload on jump lips, or bang through rock sections where you’re looking for pump and spring points throughout the mess.
And, ironically, using more of the travel more easily gives a bike less of a feeling of bottomlessness since it will be sitting into the last reaches of its usable suspension far too frequently. The bottomless feel that most people claim to be after actually comes from suspension that moves smoothly into a more resistant end of travel. With the shock wide open, the SX Trail frame ain’t got it. But to be fair, that’s also not the way the shock came in the box. I backed the boost valve setting off, and realized why it was set the way it was. This wasn’t an option on the smaller travel SX frame, so it’s not nearly as big a deal on the SX Trail.
Fortunately, the RC4 that comes with these frames is pretty darn tuneable. I messed around with boost valve pressures and high-speed compression damping a bit, but the best result I’ve achieved (where it sits now and will remain) is the minimum pressure on the shock, and the boost valve dialed about half way in, with HS compression damping at a minimum.
What this does is provide something similar to closing down the air volume in a gas chamber: it gives it some ramp up, a leverage ratio that decreases throughout its motion (similar to what a lot frames come tweaked with already). Doing this is pretty much essential to the ride on this frame, and since that’s roughly the way it came from Specialized, I can’t fault them too much. But what I can do is harp on the fact that if you run a different shock, you may not be able to achieve the same feel as with the RC4.
I’ve said it in other reviews in the past, but I like frames that are tuned well, not ones that rely on a shock to achieve the desired ride. But unlike my Turner DHR, the RC4 is a really good match with this frame. Make sure you know what you’re doing if you’re going to switch it out.
Now that we’ve got that out of the way, let’s talk about the tuned ride.
RC4 has a fat shaft that displaces a lot of oil, so it makes it very progressive. The reason Double Barrel have since made an air shock as their thin shafted double barrel coil is very linear.
Perhaps the frame was designed to run sag with such a high BB(something I neither favor).
Lower Horst Link will provide more chain induced anti squat no? Far from a bad thing. More bump compliance also, at least theoretically.
Fun bikes, but with DH bikes so light now, and efficient, I don’t see the point really. Just run pumped up air shock/fork on a demo even.
Good review though.
I have a sx trail 2010 do you think it would be beneficial to put a decent pair of triple clamps on ( rock shock boxers for e:g ) to make it a better down hill machine ? Or leave it how it is and get a out and out downhill bike .
A dual crown fork certainly wouldn’t be out of place on it but it’s still not a DH bike. Too high and too steep to really compete with a modern dh bike. But if you’ve got the fork….why not?