Xray T4’16 – Testing and setup

Given that it’s been another long time since my last post, thought I really should note down some things I’ve learnt over the past months regarding the Xray T4’16. The car in question, despite the colour (why oh why Orange!), it is probably one of, if not the best cars on the market now. It’s consistent, almost viceless, easy to work on, and (as you can see from a lot of the team setups) fundamentally has a good, well developed base setup that pretty much works everywhere.

So here is a simple list of things I’ve tried and tested over the past few months, in my usual way of running through a batch of changes to see what feels nice, and what is fast… which are sometimes not the same thing! 😉 But I do firstly need to thank the team guys of Alex Hagberg, Olly Jefferies, and Tim Wahl for putting up with my bugging questions when I get stumped, and Craig McPhee for the local pestering!

I’ll say that most of the below is based off of the Alex Euro Champs setup (here), which I’ve found to be a great base setup, with a few tweaks. My current base setup is here. Certainly plenty still left to learn, but the pleasure is that the car really does respond well to both small and big changes, which makes it easy to figure out what works and what doesn’t.

Flex – I run the raised top deck everywhere, along with no screws in the layshaft bulkheads. Every time I try the car with those in, it locks the car down, reducing steering. Underneath, the ’16 spec introduced the 4 flex screw options. They have a noticeable effect on how the feels on track. Most of the team run just a single screw in the front most position, taking out the screw and nut. In my testing, for asphalt, you pretty much want to run the forward most screw all the time. It plain has more steering, everywhere. Having said that, in certain situations (specifically on Ride RE tyres) I found that using the second from the rear hole helped to tame the car and increase it’s stability on those ‘tricky’ tyres. General rule of thumb is screws more forward = more steering.
The optional centre post also helps to lock the car down, but not as much as layshaft scews, so is a decent intermediate option, although personally haven’t bothered with it recently as can achieve similar results with the lower motor mount flex screws.
A couple of things I do want to play a bit more with are the floating steering, and the steering brace options.. they are on the list, but quite down it 😉

Shocks – PSS is a very strong option… but don’t believe the hype on using the same oil. You’ll tend to want to run around 100cst more than what you would in the standard shocks. For example, if you run 450 in the 4-hole shocks, 550 is what you’ll want to shoot for in the PSS. The other thing to use as a tuning option is the foam above the bladder. Foam in increases the pack in the shock, making the initial feel stiffer. This is a bit similar to running smaller piston holes, something that isn’t an option with std PSS. However on bumpy (and lower grip) tracks, I found that no foam really helps to smooth the car out, as the bladder compresses quickly in the high-speed damping phase.
One small word of caution though is on the actual shock oils used. Be careful when looking at team driver setups, as Hudy/Xray oil is quite thin compared to AE or MuchMore oils. Back to back, AE35wt seems to be the closest match to Xray 550, and MuchMore 500 is probably a smidge heavier. Just bare that in mind (or just use Xray oil), and you’ll be golden 😉
Also, the shock mounting is another good option. Haven’t played with rear, but in the front, the more upright the shock, the softer the front will feel. 4mm behind the top of the shock will feel smoother, but lack a little steering, whilst 2mm will be more sharp and aggressive… and don’t forget the bottom shims affect this as well.

Springs – 2.7’s are the go to, and pretty much work everywhere. The progressive 2.5-2.8’s are also useful to have, as in really hot conditions they can help to look after tyres as they don’t overload them initially. Also useful in the front only to smooth out the initial steering, but can make it too numb in low grip. I’ve also recently started trying out the new Yokomo silver and pink springs, which seem to sit either side of the 2.7’s in terms of rate and on-track feel.

Bump steer – Has a massive effect on freeing the car up in the middle of corner, very noticeable in slow speed hairpins. 4mm as in the kit asphalt setup is far too much IMO. I keep ending up on 1.5mm at the moment, 1mm is a little easier to drive, but lacks just that little bit of mid corner front end.

Hexes – Narrow (-0.75) gives more grip… kit more stable… next 😉

Rear toe – This is one of those things that some struggle with. Less rear toe IS faster, but it requires a bit of time to get used to. Even in low grip, I will always run 2.5 (although it’s more like 2.8 on gauges). The nice option with the kit is that you can easily tweak how you reduce the toe to play with the track width, which also has a distinct effect on the performance. Widen the RF setting (0.5out), will make the car a bit more stable, but slightly less grip. Narrow the RR instead, and it’s more reactive, with more rotation, but a bit more tricky to drive. My personal preference is 0.5out on the RF, I like the stability. There has been the odd occasion where I’ve wanted to get a bit more steering, and have tried even less rear toe in, which helps in the rotation effect, but at the expense of forward traction.

Front end – When I first picked up the car, I preferred keeping the front pins straight and flat, albeit with the 0.5 down and out blocks in place. I didn’t like the ‘Hagberg’ style front end setup (FF 1.0 down and out, FR 0.5 down and out), felt to numb for me. But recently (and I’m not sure why), I switched my opinion, and every time I go back to flat and straight, there is less steering… weird eh?! Also find the car better on the brakes as well, which is ideal for mod and tight and twisty tracks. I am yet to try the indoor style setup though (FF 0.5 down and out, FR zero), but I think this might work better with the rest of the carpet setup than simply bolted onto the asphalt setup… something to test for the future.

Camber links – I really haven’t strayed much from the EC setup, but 1mm under the rear link helps to settle the car in lower grip. Otherwise, it’s 2° camber, and your set 🙂

Diff – Now the Xray diff is still one of the best diffs on the market. Build it as the instructions, with the exception of not bothering with the black case o-ring (you’ll only need to replace it when you change oil anyway), and its zero leak and super free. In terms of oil range, for mod at least 3K, 5K and 7K will cover most situations. 3 is that bit easier to drive, but the advise given to me is to go as hard as you can without the car doing donuts on power, then tune the rest of the car to suit.
Also, fill level on the diff is important. Following the Xray instructions on using weight to measure it is the most consistent way of doing it, and a short fill can change the diff feel. Generally less oil will require a higher weight to get the same feel, but also might change more during the run. Hence why I tend to prefer to max fill (1.3g) and leave it at that.

Diff Height – As the book says, low gives more traction and is a bit smoother to drive, will high is more steering. Given I’m running mostly on low grip asphalt (and it’s getting colder heading into winter in the southern hemisphere), low is the go, just can’t beat the traction.

Plastics – There doesn’t seem to be a huge difference in lap time between the standard hard plastics vs the graphite plastics, but the graphite’s do sharpen the car up, and feel more consistent. I wan to play more with the c-hubs, but it’s generally graphite everywhere.