Croftbound

Melted wetI seem to have driven up the A1 several times recently, including the visit to daytuner I mentioned a while ago. However, we’re soon going to be going up there to the Croft race circuit which is just south of Darlington. I’ve been to Croft once before. For some inexplicable reason I did a track day there in 2004. God knows why because my write up of it (which you can still find here) says that we set off at 0400 which is bonkers.

I can, as a consequence, just about remember the circuit although not in any really useful way. Before getting into details of the preparation for yet another trip up North, here’s a photo of one of the Avon wets after running them on a drying track at Brands. As you can see they’re in less than pristine condition. I can only hope that they’ll recover if used more sensibly. As you’ll have read if you looked back at my old notes about Croft it absolutely pissed down when I was there before and it’s bound to be a possibility again.

Soft ARBSo, I’ve been looking into how to make the car handle a bit better. In particular how to dial out the understeer. The obvious thing to address here is to make the front ARB a bit softer. You’ll remember that I did do some modifications over the winter to make the ARB fit inside the bodywork and, despite all my calculations, perhaps I didn’t get the rate right.

So, I set about making a new ARB using tubing rather than the solid bar that the current one is made with. However, after a day slaving over a welder and a lathe I ended up with a new ARB that was pretty much the same rate as the old one. (Measured using some weights and a dial gauge so it should be accurate.) That was a bit disappointing although, if I’m honest, not really a surprise as all the formulae show that when you’re twisting a tube it’s the material at the outside of the tube that has the biggest effect. Mind you, the new ARB is at least lighter.

bump steerI did modify things, though, by changing the actuation point for the ARB drop links on the suspension bell crank. That should mean that the bar has to move a shorter distance so in effect it’ll be softer. Luckily, I’ve booked the test day for Croft so I’ll have a chance to try it. Assuming that it’s dry of course…

Along the way I did a whole lot of very careful measuring of the suspension. I measured, and adjusted, the front caster angle. I did something I’ve been meaning to do for a while and measured and adjusted the bump steer. (See the pretty graphs on the right.) I’ve also decided to change the camber settings slightly, and as such Setup stringI spent some time adjusting the camber and, with the setup frames back on the car and some setup strings stretched down the side of the car (see the photo), I checked the toe settings.

I’m not sure I’ve talked about this before, but I’ve always thought this is the best way to set a car up. There’s a couple of steel frames that bolt to the chassis (you can see one at the bottom of  the photo) and then I stretch some bits of jazzy fishing line down the side of the car. The advantage of doing this is that you can check that the axles are toed correctly with respect to the chassis and not just from side to side of the car. The big downside, to be fair, is that if anything it’s too accurate and you can spend ages tweaking things.

Anyway, that’s all done. Next on the agenda is tarting up the bodywork slightly after its molestation at Brands…

 

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