Back from Combe, great day!
Tested out various tyre pressures:
33 - grip very spikey
32 - good grip but times when it did feel spikey e.g low speed or making a small mistake and it reacts dramatically
31/31.5 - good grip, quite balanced
30 - felt great, didn't feel super quicker than 31/32 but balance was way more neutral and tyres felt like they could last longer before going off
So 30 sounds like ideal on AR-1's and probably any 100-200 treadwear tyres.. which is what retro resus told me before but thought I'd find out for myself.
I've come across the idea of "scale factor" in terms of tyre pressures, its a way to set hot and cold pressures to get the exact correct pressures every time. So after reliably getting 30 hot, I'll take a cold reading with the tyres in the shade after they have completely cooled, then divide hot by cold and you get a scale factor, you record the scale factor along with the ambient temperature so it means next time you turn up to the same circuit you can see the scale factor and get it right first time, second time worst case rather than having to keep an eye on it constantly. Each ambient 1 degree is worth 0.1 psi so the scale factors I took were:
@27.5 degrees ambient
FL = 1.33 (22.5)
FR = 1.27 (23.5)
RL = 1.2 (25)
RR = 1.11 (27)
So next time I'm there if the ambient temp is say 20 degrees ambient i would set cold to:
FL = 1.33 (23.2 ~24)
FR = 1.27 (24.2 ~ 24)
RL = 1.2 (25.7 ~25.5)
RR = 1.11 (27.7 ~27.5)
Nice to have that recorded, I do think tyres are something overlooked a lot of the time, they're very delicate things and definitely need some thought to get them working well.
The front ARB was on full soft and the front was washing out quite a lot and rolling more than I'd like.. going from full soft to full hard added quite a lot of front grip and stability too. There is some "man maths" logic out there that you should only get a stiffer rear arb and keep an oem/super soft or no front arb but this isn't true at all, if the car rolls a little too much on front then stiffening the front should add more front grip not take away.
Recorded temps a couple of times, not every time but if these are not the highest settings then I imagine they are very close to these:
Intake temp: 60 on idle, 38-40 when running
Coolant: 99
Oil: 122
Brake caliper - 195
So Oil and coolant within my target but close to borderline, not giving much more wiggle room, also only running on map 2 ~220bhp all day which may see lower temps. I'm not overly worried as that big ugly AC condenser is surely blocking some clean airflow to the rad and intercooler. Worst case I can always add some bonnet vents to get some hot air out, I do like the middle tcr vents but I think you need some exhaust venting from the IC and rad to get the most out of this and that requires some very clever fab work so.... maybe I will 1 day maybe I won't.
Brakes held up though! Lack of weight, bigger caliper/pads/discs along with some better air flow has paid off, though the golf r calipers do not modulate well I got to say. What I mean is if a braking zone is downhill, and you unbalance the car by going 100% so you want to apply only 80% of the brakes to keep the car balanced then it does not feel like you have 80% of braking power, it feels about 50%! It is manageable but not ideal, not sure its worth the weight saving over the r32 setup because of that modulation issue. It also does not like much trail braking at the mo, probably because right now its super nose heavy having an empty rear.
For anyone who's never been to Combe, a great part of it is its probably the nicest part of england being on the edge of the cotswolds, so 3 minutes down the road you have beautiful scenic gastro pubs. Even my Mrs likes coming here because of that factor
Its a great excuse for weekend away.
Just to sum up, the car was rapid all day, obviously driver experience plays an enormous part but still going to take the pride in it seemingly being one of the quicker cars lapping all day. Really makes me want to get it running on map 5(273bhp) with a wavetrac diff and more camber, it should fly.