Thoughts & Pics From First 4 Autocross Events - Alfa Romeo 4C Forums
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post #1 of 28 (permalink) Old 04-22-2019, 04:53 PM Thread Starter
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Thoughts & Pics From First 4 Autocross Events

Finally got some seat time in the 4c. 25 total runs over 4 very different courses in very different conditions. Overall, I am happy with it so far with 2 top 10s in raw and winning my class twice. It is considerably different than what I'm used to.

215/245 RE71r
-1.7* front camber
-2.1* rear camber
0 front toe
0.20" rear toe in
Factory everything

Initial thoughts:

1. Significant corner exit understeer. I think its a combo of the front tires not getting heat and the driving style I'm accustomed to. I am used to adding throttle to correct exit understeer. In this car, more throttle just ADDS exit understeer.

2. Above average corner entry understeer. I believe this is also a combo of not getting heat in the front tires and the driving style I'm used to. I think coldish 215's are being overwhelmed by hard braking zones followed by quick turn in. I need to easily brake earlier and learn to steady trail brake through mid corner, opposed to turn in with no brake/throttle input.

3. Tire pressures. For the start of each event, I have set the pressures to 26/29 cold. After each run, I have gained maybe .5psi in the rear and nothing in the front. This has been consistent. Front tire rollover hasn't been very detailed either. I lowered the front to ~24 cold with no change in grip, and slightly more rollover. This is pretty puzzling to me. I need more events to really gather more data. This coming weekend, I may start at 30/33 cold and see how the car reacts.


Any thoughts?
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post #2 of 28 (permalink) Old 04-22-2019, 05:40 PM
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Nice report and pix.

Please refresh my memory - what car were you coming from? Also mid or rear engine? Makes a big difference in terms of understeer. As do the 215's (though at least with the Potenza's you have a significantly wider tread than the P-Zero's). I think brake feel on the 4C also takes some getting used to - the travel is so short and even less so with RAB enabled

I've not done much Auto-X in the 4C, so this is interesting to read. On the road course, I drop pressure significantly, but it doesn't take long for the heat to build it back up (and keep it up) again. Not so much on a 1 minute course. I'm surprised that lowering 2PSI did nothing for grip, as on the track it makes a big difference (others have reported similar, so it isn't just me). Especially on the 18/19 Wheels.

Very interesting points. It's always challenging to work with a new platform. Sounds like you did quite well, despite having to learn/adapt. Congratulations!

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post #3 of 28 (permalink) Old 04-22-2019, 05:45 PM
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Question - you say "factory everything", but the rear wheels seem to fill out the gap better than normal - is it just the compression in the car in those photos, or do you have spacers in the back?

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post #4 of 28 (permalink) Old 04-22-2019, 07:29 PM
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Question - you say "factory everything", but the rear wheels seem to fill out the gap better than normal - is it just the compression in the car in those photos, or do you have spacers in the back?
I think it's the Potenza RE71r tires - 215 up front and 245 in the rear. Stock is what, 205 & 225? Looks like you had a blast tho. I would think it would be hard to gage much in the wet. Doesn't everything have understeer in wet conditions?
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post #5 of 28 (permalink) Old 04-22-2019, 08:32 PM
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I think it's the Potenza RE71r tires - 215 up front and 245 in the rear. Stock is what, 205 & 225? Looks like you had a blast tho. I would think it would be hard to gage much in the wet. Doesn't everything have understeer in wet conditions?
Stock is 205/40-18 & 235/35-19 in the larger wheel size. +1 is the 215/245
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post #6 of 28 (permalink) Old 04-22-2019, 09:13 PM Thread Starter
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Nice report and pix.

Please refresh my memory - what car were you coming from? Also mid or rear engine? Makes a big difference in terms of understeer. As do the 215's (though at least with the Potenza's you have a significantly wider tread than the P-Zero's). I think brake feel on the 4C also takes some getting used to - the travel is so short and even less so with RAB enabled

I've not done much Auto-X in the 4C, so this is interesting to read. On the road course, I drop pressure significantly, but it doesn't take long for the heat to build it back up (and keep it up) again. Not so much on a 1 minute course. I'm surprised that lowering 2PSI did nothing for grip, as on the track it makes a big difference (others have reported similar, so it isn't just me). Especially on the 18/19 Wheels.

Very interesting points. It's always challenging to work with a new platform. Sounds like you did quite well, despite having to learn/adapt. Congratulations!

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Question - you say "factory everything", but the rear wheels seem to fill out the gap better than normal - is it just the compression in the car in those photos, or do you have spacers in the back?
My previous heavily autox'd car was a 650whp s550 Mustang, so this is very different hah.

I think the next time out, I am going to drop pressure for the first heat to like 22/25 cold and then raise pressure for the second heat to like 30/33 cold and note the differences.

I do have spacers actually, 16mm all around. They are on the car for the wet photos.
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post #7 of 28 (permalink) Old 04-22-2019, 09:14 PM Thread Starter
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I think it's the Potenza RE71r tires - 215 up front and 245 in the rear. Stock is what, 205 & 225? Looks like you had a blast tho. I would think it would be hard to gage much in the wet. Doesn't everything have understeer in wet conditions?
All of these impressions are based on dry events. The wet pictures just looked cool lol.
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post #8 of 28 (permalink) Old 04-22-2019, 09:39 PM
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I’m running the same cross section widths RE71-R on 17/18 wheels on track. Find that is quite nicely balanced. The car still feels like it is on its tippy toes, and if I had more power to put down I suspect there could be a problem. But on stock everything else, on a curvy technical course, it it a blast and not too slow.
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post #9 of 28 (permalink) Old 04-23-2019, 01:46 AM
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Beautiful car looks like you had a lot of fun. Great job thanks for sharing.
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post #10 of 28 (permalink) Old 04-23-2019, 10:15 AM
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I'm very puzzled on your constant understeer. Did you get any oversteer? The 4C is a balance car, it does NOT like to be crash dived into corners. It requires finesse and smooth consistent inputs. You will want to have 90% of your braking completed before you ever enter the corner. A very light and smooth trail braking into the corner balances the car, and you can be on the throttle almost before you enter the corner. Yes, due to the weight of the car, and stiffness of the suspension, you can make quick turns (but do it SMOOTHLY). On exit, you should get some throttle oversteer with the 4C. If you are quick enough on exit, then you could get some 4 wheel slip, but that is how you drive it on the limit.

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