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Still square at -1.5, ARBs mid-setting, still wasting time on Cup2 N2 was moving to Trofeo R but have decided to test Cup2R on square set up. No need to go beyond -2.
Night - tarmac rally SS4 - got a gong
Prep going well, Bell comms good, red light effective, co-driver excellent, car excellent, Cup2 N2 average, TP App didn't initiate at start line, may change to a more aggressive pad, driver lots to work on. Car gets great air
I find for me on my 2018 GT 3 that -1.7 camber front rear seems to be working just fine.
What toe settings front and rear are you all using. I did zero toe front and 2mm toe inward rear per side.
I had -2 camber all 4 corners this past season but increasingly started wearing the outside more (as I got used to the car and pushed harder) - the last set of Dunlops prematurely corded on the outside on both left front and left rear after 4-5 days so I think I'll try a touch more next year -2.25/2.5 to see if I can get a bit better wear - and maybe try the Trofeo R
One observation: a lot of discussion on geometry here, but not a lot on tire pressure.
TP is a critical element in your setup. Before going about camber and toe and rake you need to make sure you have run data on baseline condition tires at proper temps and pressure.
This is not straightforward: a July run in Sebring will yield completely different outcomes as a December run in Laguna. Forums are a dangerous place to get baseline pressures because of the extreme diversity (and accuracy) of datapoints.
Suggestion for those who haven't (entirely) gone down the rabbit hole? Freeze your setup assuming you're not running anything extreme like 3.5 deg camber and 0.5 deg total toe LOL. Go through two sets of tires from stickers to scrap (doesn't matter whether it's Cup2, 2Rs, Trofeos or Hooters) and observe their evolution. Note the before and after tire pressures after each run. Come in on a hot in-lap and get a mate to measure your actual operating pressure before you go back out and do the cool-down. You'll come to understand a lot more about your car and driving.
One easy example: driver mentions entry and mid-corner understeer in the paddock. Common tech response will be soften front / increase toe / drop front. More nuanced response is at what phase of the session is that entry / mid understeer? Your tech inputs should benefit the peak phase of the tire during a run, not the suboptimal phases on either side of the bell curve.
In 911s our fronts take a fair bit longer to warm up and develop full grip. Hence easy to overdrive (and damage) the fronts when they're cold. Outboard shoulder wear despite 2 deg+ front camber and can be a tell.
Long post short, take a look at your pre & post run pressures accurate within 1 psi every session. Look at your in-cars before coming to a conclusion. Consider TP adjustments as your first tool. When you're finally convinced that the car's exhibiting a certain ailment at peak tire performance, feel free to embark on multi-variable calculus with the rest of your setup
Come in on a hot in-lap and get a mate to measure your actual operating pressure before you go back out and do the cool-down.
^This is critical. Taking tire pressures after a cool-down lap or back in the paddock after a session - witnessed both many times - is completely useless.
^This is critical. Taking tire pressures after a cool-down lap or back in the paddock after a session - witnessed both many times - is completely useless.
I wonder if anyone has found an easy solution to live tyre temperatures? I've seen it on McLaren's whilst on track, not sure how they work, if it is a tyre internal air temperature gauge or an external (infra-red?) thermometer?
Over analysing it - keep front and rear consistently in low to middle 30s max hot then drive it as it is - you have no choices beyond that really.
If that's the approach better not waste time talking about geometry. A 2 psi change is enough to negate pretty much anything you put into camber or ride height. Heck, 2psi itself would give a mil of ride height change
If that's the approach better not waste time talking about geometry. A 2 psi change is enough to negate pretty much anything you put into camber or ride height. Heck, 2psi itself would give a mil of ride height change
Its entirely realistic and practical - you can stuff around trying to optimise your tire pressures and temps for ever and yet you can’t control these on the fly.
The most important information to note is what best hot pressures work for you personally on any given track or surface and for the length of the run you are involved in. If you have to run for six days on a total of six tires - your setup will be very different to a sprint series.
Setting up a good baseline geometry and alignment is very much a fixed starting point to build on by increments. The tires are the variable that changes the most (within reason and have the greatest impact on performance) but are least able to be adjusted beyond - pressure. Thus a track specific alignment, geometry and corner weighting (or good general all round or average set up) - leaves you with only one variable to play with - the tires.
That’s the aim - to limit the variables down to tires and then be smart enough to know what hot pressure range you need to run. When you have that worked out you - there is very little else to do but drive and if you have things broadly right - drive to the limits of grip the set up offers and recognise the limit of grip changes lap by lap and understand how to monitor that - eg g meter. That’s all you can do.
I’m just looking for a baseline alignment. I do not track enough to run through 2 sets of tires quick enough to see what’s going on.
I personally stay basically close to Porsche stock alignment...with camber...found at the tire pressures I run at the track ...34/36 hot....I get away with -1.7 camber on my 991 gt3 and this also works great on the street. I keep toe with in OEM spec.
The check alignment was done two days before the event (in effect a very good stock alignment).
Understeer was felt through most corners - oversteer (at 13s mark in video) was felt on one fast corner (both understeer and oversteer was measured through data logging on PTP app). Hot tire pressures typically front 31, rear 34 - but hard to control for short burst stages plus wait for ~ 100 cars to go through. For this type of work probably needs no more than another -0.5 (~ -1.8) on all corners and the front sway bar dropped to soft setting.
Report card for the MPSC2R is mixed (UTQG 140), definitely more grip but still same soft sidewall as MPSC2 - tire squirm still present under hard braking. max lateral gs (as measured at 10Hz) ~ 1.5 which given the nature of the surface is pretty good (about 0.1 g over the regular MPSC2 on this surface - note air temperature ~ 35 degrees celsius).
11-18-2019, 09:14 AM
