ea_sport
ea_sport Reader
2/7/21 1:46 p.m.

I was planning on co-driving my son's 2013 Abarth 500 in HStreet with just sticky tires as the mod. He'll get his full license in April and this will be his car. How tippy top/prone to flipping over  is an Abarth 500 on autocross course? Looks like for the metro Washington DC area all autocrosses will be in Summit Point at their former go cart track (SPK) so it's not a wide open parking lot like FedEx field if that makes a difference.

Is it really a bad idea to autocross a basically stock Abarth 500 with sticky tires like the Falken 660? It's basically just for fun and some father son friendly competition. My other car is an '03 C5 Z06 which is probably too much for new driver lol. Thanks guys.

Duke
Duke MegaDork
2/7/21 2:37 p.m.

Well, the Abarth version is the only 500 you can autocross in Street class because of the rollover risk in standard trim.

That being said, over the years we've had several Abarths autocross with us and none seemed exceptionally tippy for a small FWD car. MINIs are just as prone to lifting the inside rear. 

dps214
dps214 HalfDork
2/7/21 2:48 p.m.

If it's just for fun, get some 300TWs that will still be plenty of fun but not as likely to roll. There's plenty of videos around of people rolling or nearly rolling them.

ea_sport
ea_sport Reader
2/7/21 2:54 p.m.

In reply to dps214 :

yeah..those vidoes kinda scared me....

spacecadet (Forum Supporter)
spacecadet (Forum Supporter) UltraDork
2/7/21 5:17 p.m.

There is a real threat you can roll this car over if you drive it hard and ar eon properly sticky tires.. .. the SAC buried the car in GS for years.. rumor was it was because they didn't want it to become popular to autocross.

bluescooby
bluescooby Reader
2/9/21 12:09 a.m.

I autocrossed one in GS and HS for a couple years and ran track days with it.  Stock suspension except a big rear bar and some 200TW tires.  I've seen the videos of Abarths rolling over but I never had any troubles.  A big rear bar will actually dial out a huge chunk of instability from the back, I would pop one of those on even if you have no intention of upgrading the suspension further.  Plus it's a Stock Class-legal mod. 

mad_machine (Forum Supporter)
mad_machine (Forum Supporter) MegaDork
2/9/21 10:17 a.m.

Big rear bar is on the list of things to do to my car.  I do not intend to race it, but I can feel the instability in the rear under hard braking.

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
2/9/21 4:57 p.m.

In reply to mad_machine (Forum Supporter) :

A rear bar should make that worse, not better.

bluescooby
bluescooby Reader
2/9/21 7:13 p.m.

In reply to Pete. (l33t FS) :

It should, but for some reason in the Fiat it's the opposite.  I did before-and-after laps on a small track I have access to and the difference surprised me.  Straight-line braking and trail braking into a corner were both really spooky with the stock bar.  I'm assuming the narrow track width, short wheelbase, and higher center of gravity conspire to unsettle the back tires when you shift weight to the front under decel, and the bigger bar helps keep the back tires planted longer during those transitions.  Car will still rotate when you want, it's just way more predictable. 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
2/9/21 7:24 p.m.

That's the part that makes my brain go "huh?".  Big rear bars work on a front driver by unsettling the rear.  But, I'll accept practical experience over theory, and then try to figure out why that works.  (Hooray for scientific method!)

03Panther
03Panther SuperDork
2/9/21 7:29 p.m.

I may be over simplifying it in my thoughts, and might be thinking wrong, but a stiffer rear bar should make it less likely to roll, and more likely to slide... if I'm thinkin' correctly?

bluescooby
bluescooby Reader
2/9/21 8:46 p.m.

In reply to 03Panther :

I don't fancy myself an engineer but that makes sense to me.  I also never ran that car with R-comps or anything so as the tire's friction coefficient goes up you may start to see less sliding and more tipping again.  Just a guess, but Abarths on race rubber did tend to flip with some frequency in the European one-make series...

dps214
dps214 HalfDork
2/9/21 9:05 p.m.
03Panther said:

I may be over simplifying it in my thoughts, and might be thinking wrong, but a stiffer rear bar should make it less likely to roll, and more likely to slide... if I'm thinkin' correctly?

In single input and steady state cornering situations, more or less. But the rollovers are almost always multiple quick inputs, ie a tight slalom or other situation where the car is unsettled and then you chuck it back the other direction. In that case, the extra roll stiffness makes the inputs more of a shock to the system and turns the car into a pogo stick of sorts with unpredictable results. Of the handful of fiesta/500 roll or near roll videos, I think I've only seen one that wasn't some sort of tight slalom or decreasing radius corner into a quick switch back the other way. Also note you can roll a car just fine without the swaybar, one of the more recent victims was an older focus on what I'm pretty sure was totally stock suspension, just tires.

ea_sport
ea_sport Reader
2/9/21 9:20 p.m.

In reply to bluescooby :

Which big rear bar did you use? I only found the Neu-F rear torsion bar.

03Panther
03Panther SuperDork
2/9/21 9:21 p.m.

In reply to dps214 :

Excellent explanation. Thanks.

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