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crankin
10-08-2013, 11:31 PM
Correct me if I am wrong but my Abarth has dual trailing arm live axle rear. Can someone tell me how the axle is located to center? Reason for asking is after installing my new mudflaps it has exaggerated the fact the rear end is not centered within the body, this is measuring with a straight edge to the fender line. Is this normal mfg specs? Can it be adjusted or am I just picky? I took a quick look under the car but didn't see the normal panhard bar I am accustomed to.

Tweak
10-08-2013, 11:39 PM
Just wanted to say 2 things...(3 if you count this portion) :D

1. Welcome to the forum.

2. Several people have mentioned/complained about the rear being off center and some have mentioned odd tire wearing problems additionally...think you may be stuck with what you have sadly. :(

Fiat500USA
10-08-2013, 11:49 PM
The 500 Abarth uses a twist beam design. It is a one piece unit that is serviced as an assembly if components are bent or damaged. There is a bushing pressed into the front of each side of the axle assembly; the bushings are not serviced separately. The axle is mounted to its location on the body with three bolts on each side of the assembly.


https://lh3.googleusercontent.com/-5thRFsFmgQM/UlTRVw_bPvI/AAAAAAAASuU/GhdLOulhV-w/s800/Fiat500USA.com-Fiat_500_rear_axle_beam.jpg


http://youtu.be/RA0cKH0Z33k

Check out Fiat500USA.com (http://www.fiat500usa.com/) to find out all about the 500 Abarth.

lammie200
10-08-2013, 11:53 PM
I am not sure that the wheel/body centering issue is related to the tire wear issue but it might be. I think that someone will eventually make shim kits to rectify the centering problem because it is fairly widespread as far as I can tell. Mine is off by about 3mm, but my tires seem to be wearing evenly. Overall I consider the centering issue negligible.

msjulie33
10-09-2013, 12:34 AM
As was said, it seems more than one 500 has the axle misaligned in relationship to the body (thrust angle and other?). My Studio did a bunch of work to realign the car, front and rear, to spec - even using shims out back to provide a little more camber for me.. there's more to the story, but basically I do think a motivated tech could make little adjustments here and there.

crankin
10-09-2013, 08:55 AM
Good info guys much appreciated. I am new to the Fiat family and didn't know this was on on going issue. As far as tire wear I only have a 1000kms and the car tracks straight. So I will keep my eye on it.

Tweak
10-09-2013, 10:43 PM
I am not sure that the wheel/body centering issue is related to the tire wear issue but it might be. I think that someone will eventually make shim kits to rectify the centering problem because it is fairly widespread as far as I can tell. Mine is off by about 3mm, but my tires seem to be wearing evenly. Overall I consider the centering issue negligible.

Got an alignment today and was told the rear is pretty far out of spec but cannot be adjusted, also was stated the tires did not show unusual wear so not to worry about it but keep an eye on it and maybe they'll have some shims to resolve it down the road.

Fiat500USA
10-10-2013, 12:17 AM
Got an alignment today and was told the rear is pretty far out of spec but cannot be adjusted, also was stated the tires did not show unusual wear so not to worry about it but keep an eye on it and maybe they'll have some shims to resolve it down the road.

Do you know what alignment specs they used? There are sometimes discrepancies in these specs. I even found them in factory manual and brought it to their attention so they corrected it. Compare your specs to the correct ones below:

https://lh4.googleusercontent.com/-s5Uwhsohdco/T9lwW9gfIUI/AAAAAAAAMQg/c17PYpOFHDk/s800/Fiat500USA.com-Fiat_500_Abarth-Alignment_Specifications.jpg

Fiat 500 and 500 Abarth Wheel Alignment Specs (http://www.fiat500usa.com/2012/06/fiat-500-and-500-abarth-wheel-alignment.html)

msjulie33
10-10-2013, 04:56 PM
Got an alignment today and was told the rear is pretty far out of spec but cannot be adjusted, also was stated the tires did not show unusual wear so not to worry about it but keep an eye on it and maybe they'll have some shims to resolve it down the road.

There's no normal adjustments but some of the thrust angle can be 'tweaked' :) and as was mentioned there can be shims added.... I'm a broken record on that but I do think it made a difference in my car's handling

Tweak
10-11-2013, 12:13 AM
They looked up the 2012 specs in their system and adjusted without camber bolts and mentioned shims which I am interested in knowing more about and likely buy for install sometime. I will be testing things the next few days, drove about 6 hours today to TN, tomorrow going to GA then Saturday returning to TN and Sunday hitting the Dragon. When Monday rolls around and I drive another 7ish (leaving from a different area) hours back home I should know without a doubt what is needed and if things aren't working properly.

Fiat500USA
10-11-2013, 12:25 AM
They looked up the 2012 specs in their system and adjusted without camber bolts and mentioned shims which I am interested in knowing more about and likely buy for install sometime. I will be testing things the next few days, drove about 6 hours today to TN, tomorrow going to GA then Saturday returning to TN and Sunday hitting the Dragon. When Monday rolls around and I drive another 7ish (leaving from a different area) hours back home I should know without a doubt what is needed and if things aren't working properly.

Wish I was going. Say hi to everyone for me and have fun!

Tweak
10-11-2013, 12:32 AM
Wish I was going. Say hi to everyone for me and have fun!

Right on, maybe in spring.
About to get some sleep, gotta clean the car in the morning!

deathshead
10-16-2013, 09:27 AM
I'm in the same boat, when i went in for my alignment the machine showed
LR toe is WAY out, and this also took out the thrust angle as well,

Since any regular shop will go by the machine that its non adjustable.

(im guessing shims for toe?).

Now if i go to the dealer, they will tell me to take a hike since im running sportline springs.
But due to the design of the rear axle springs should NOT affect the any rear alignment settings like this.

I'll have to call the dealer and see what they can do.


Also, I had a nice conversation with the Gentleman who runs Pocono sportscar.
This is a Ferarri only race shop ran by an ex factory ferrari crew chief.
They built a Abarth Racecar and said that they constantly had issues with the rear alignment getting really out of whack every couple of HARD runs.

He said that the company who did some of the other suspension work swapped out some of the mounting points from a rubber-plastic to machined aluminum and they havent had a problem since.

He wasn't able to provide much more detail but I will contact the shop who actually did the work and let you guys know what I can find out.

Scootin159
10-16-2013, 10:05 AM
If the rear axle is off centered, this wouldn't be the first car I've had that had this issue - my old Porsche had about a 3/4" difference from wheel to fender on one side versus the other. Only really became an issue though when it came time to fit larger wheel+tire combos, as I naively did my test fitment on the side with more room, and when I went to fit the wheel+tire to the other side, it wasn't even close to fitting. I ended up being able to make it work though by getting some wheels with more offset and using a thicker wheel spacer on the one side.


But due to the design of the rear axle springs should NOT affect the any rear alignment settings like this.

Changing the spring rate shouldn't alter the rear alignment, nor should the alignment get altered in the act of installing the springs (I assume the springs on the cars just involve using a set of compressors to install/remove - no unbolting suspension components?). However, I wouldn't be surprised at all if changing the rear ride height alters the static toe on the car. It's not uncommon at all to have the rear suspension geometry setup to have a dynamic toe angle change, and so when you alter the rear ride height, you're altering the "starting point" in that toe angle curve.


He said that the company who did some of the other suspension work swapped out some of the mounting points from a rubber-plastic to machined aluminum and they havent had a problem since.

Pretty typical fare for any old street car converted to racing duty. Suspension bushings wear with time, and allow more and more "slop" in the wheel positioning, causing all sorts of odd handling issues. On a street car you would fix this just by installing fresh bushings, but for track duty people will often replace the bushings with more solid components (either some form of hard plastic or metal depending on the application).

lammie200
10-16-2013, 11:35 AM
...I ended up being able to make it work though by getting some wheels with more offset and using a thicker wheel spacer on the one side...

Using 5mm of difference in wheel spacers for the rears will make the gaps for both mostly equal. I can't see how that would help with the tire wear problem that some people are seeing, however.

Tweak
10-16-2013, 08:37 PM
I'm in the same boat, when i went in for my alignment the machine showed
LR toe is WAY out, and this also took out the thrust angle as well,

Since any regular shop will go by the machine that its non adjustable.

(im guessing shims for toe?).

Now if i go to the dealer, they will tell me to take a hike since im running sportline springs.
But due to the design of the rear axle springs should NOT affect the any rear alignment settings like this.

I'll have to call the dealer and see what they can do.


Also, I had a nice conversation with the Gentleman who runs Pocono sportscar.
This is a Ferarri only race shop ran by an ex factory ferrari crew chief.
They built a Abarth Racecar and said that they constantly had issues with the rear alignment getting really out of whack every couple of HARD runs.

He said that the company who did some of the other suspension work swapped out some of the mounting points from a rubber-plastic to machined aluminum and they havent had a problem since.

He wasn't able to provide much more detail but I will contact the shop who actually did the work and let you guys know what I can find out.

I was told I should look for shims if possible by a friend that is a mechanic and did my alignment. I did have mine aligned and then put over 1K miles on it, much of this aggressively carving up mountain roads and I am hopeful my new tires won't be seeing the unusual wear others have mentioned...the old seemed to be ok when they came off we noted but that was with stock suspension and I am curious if my new setup will create issues. Time will certainly tell.

jguerdat
10-17-2013, 09:24 AM
Changing the spring rate shouldn't alter the rear alignment, nor should the alignment get altered in the act of installing the springs (I assume the springs on the cars just involve using a set of compressors to install/remove - no unbolting suspension components?). However, I wouldn't be surprised at all if changing the rear ride height alters the static toe on the car. It's not uncommon at all to have the rear suspension geometry setup to have a dynamic toe angle change, and so when you alter the rear ride height, you're altering the "starting point" in that toe angle curve.

Not sure this is applicable since the rear is basically a bar across the car. How would anything change from ride height, dynamically or statically, when the wheels are essentially bolted to the bar?

Scootin159
10-17-2013, 10:05 AM
Not sure this is applicable since the rear is basically a bar across the car. How would anything change from ride height, dynamically or statically, when the wheels are essentially bolted to the bar?

The rear suspension is a torsion beam suspension, which has dynamic properties more similar to a semi trailing arm suspension than to a solid axle. The wheels can move independently of each other as the torsion beam is designed to twist. If the axis on which the wheels move isn't parallel between the two wheels (typically handled by having the "trailing arms" pivots rotated to have a slight toe in), the rear wheels will gain/loose toe as they move up/down. They'll also see a corresponding camber increase/decrease.

Generally this bias is setup such that the rear will gain toe in during braking, for improved stability - which means that if you put shorter springs on the car, you'll have more static toe out (increasing tire wear and decreasing rear stability). The same geometry also works to increase rear camber as the corner squats - which means you're also adding static camber in the rear as you change the static ride height. Combine that static camber + static toe out and you'll likely see increased tire wear on the inside edges of the tires.

I know in the Porsche this was all adjustable by having adjustable trailing arms - you could basically change the angle the trailing arm meets the torsion beam, but you still had camber and toe linked together - you could just adjust the static position within the two curves. There was an aftermarket torsion beam available that allowed you to decouple those two by adjusting the position of the pivot within the chassis however.

That last bit gives me an idea though - if you do run into suspension geometry issues with lowering springs, you can likely rectify those by installing some shims between the torsion beam and the chassis. I wouldn't just go throw some aluminum spacers in there though - you'll want to put some good thought into the forces involved there, as I would think you'll need to upsize the bolts there at the same time to prevent them from breaking.

jguerdat
10-18-2013, 08:10 AM
Good reply - hadn't thought about it in that way. Thanks for the explanation!

Of course, with a stiffer torsion bar (I have the Neu-F) the deflection decreases, right? That doesn't address lowering, of course. BTW, here's the specs used at last year's Targa Newfoundland stock car driven by Roy Hopkins and Adrian Hughes:

Camber:
(deg)

LF -2.50 RF -2.50
LR -1.50 RR -1.50

Toe:
(mm)

LF -1.00 RF -1.00
LR -1.00 RR -0.5

The suspension was pure stock except for the adjustment capabilities (shims used for the rear). The camber increases were big but the toe, especially on the rear, surprises me compared to stock:

8188