My 131 abarth (never ending) story - 2017 season updates

[miro-1980]

Nigel,

The best off the shelf solution for 123 are the WHOA brakes from US, They just bolt in !
see http://www.midwest124.com/Whoa_Brakes.htm


Re : spacers.

I am currently using long bolts.
I would never even consider bolting my wheels to the spacer.
Somehow this contradicts my sense ofphysics.

I am currently expecting delivery of "pins" that are over twice as long as the original gr 4 pins. They need to be made from a rolled steel to be really strong. I found a supplier who will make therm to order. Thus the setup will be very much like the ogitrinal gr 4 but allow for use of spacers. This way the nut is applied from the wheels side which allows for quick mounting of a wheel ( should you get a flat on a stage).

The spacers are currently ca 43 mm but will be ( probably shaved off to around 37 mm. This may be done after final assembly and testing.
The spacers are made from special aluminum alloy designed for aviation.

Unless you require originality for your class , I would recommend the whoa brakes. If you intend to race it on tracks or tarmac rallies i also recommend good sports disks, steel reinforced brake cables, good high temp DOT 4 or DOT 5.1 brake fluid and racing pads ( which squeak and do not brake when cold)

Note : watch out for extra large wheels or lowering of the 124 spider etc. This drastically changes geometry of a spider and is known to cause crashes at high speed. I would recommend 13 " (or 14 inch wheels but only if you need to put larger brakes).


Miro

[Walezy]

You can do a simple thing with spacers. make it this way, bolt the spacers to the hub using screws and then drill holes in the spacers to fit pressed studs. i use it in my car like this in the back and this makes no problems at all. simple and effective, you can buy studs brand new for about 2 euro each at most tire change workshops as well as the nuts. PA6 aluminium is good enough for the spacers.
Using long bolts or studs puts some more stress on it.
I do not use spacers in the front(I use it only if neccesary to correct the ET of the wheel so that my brakes do not touch the wheels) as it makes the car handle worse than it would be with longer wishbones, i prefer to make the wishbones longer.

[miro-1980]

Tomek,

Re :wishbone - I agree with the longer wishbone being preferable to spacers on long studs or bolts, however this is only when you design the suspension. Mine is fixed.

Re: more stress with longer studs or bolts. Agree again.
If I were to make hard and long jumps the stress difference could make a difference.
The stress on long bolts is in cutting not pulling force. Provided the spacers are made of proper material and fight tightly it should not make much difference.

Re handling: I have no real experience to tell the difference.


Few philosophical remarks on the theme:

My key concern is stability of the car on curves (defined as relative lack of propensity to spin out of control at high speed and lots of G force.

Lots of elements influence this: wWeight distribution, height and dimensions of suspension, weight of the car, traction of tires, etc etc. But this is only part of "handling". The car needs sufficient ease and accuracy of steering. Hence geometry of suspension and steering. To me this is a very high science. Few professional designer teams in history ended up with close to perfect setup. Most that came close ended up with a car which was mechanically unreliable, required too much expensive maintenance or had other major flaws. It always is a compromise.

Theoretically the best would be a car which is completely square , with a Center of Gravity (CG) below the center of the car floor and with wheels giving the greatest traction ( friction between tire and road surface).

And there is the driver, which is the unpredictable and unmeasurable variable.

So , any car build for sports use is modified and suspension is a key modified element. It is modified by the mechanics based on feedback from the driver. It is done by the most scientific method : trial and error.

So the bottom line is this : modify and test, test and modify until you find a perfect balance for all surfaces, all weather, all tries.

Sounds a bit stupid , but in essence this is what Walezy is saying and he has tested , modified and re-modified a lot of setups.

So, I will review my setup based on his tips ...

thank you


Miro

[TomLouwrier]

hi guys,

I have said this before and will do so again: a fastener (bolt, stud, etc) should be seen as a spring. It pulls two or more items together. That's all it does. No location, no transfer of torque.
Yes, they can take some shear load ('cutting') but that is just a bonus and not something you should use in your design.

This means, as Jason mentioned as well: make sure that your wheel and spacer are well centered and positively located. If you use the right bolt or stud with the right tension it generates enough clamping force to fix the wheel, spacer and hub together without moving. The longer the bolt / stud, the better it will resist vibration. Shear and tension are not related to length.
If you rely on the bolt to locate your wheel and spacer, then sure it will be subjected to shear loads (not a very big problem, just unwanted and not necessary) and bending. It is the bending that increases with length and makes the bolt break off at the hole, usually in the last full thread (a carve in the surface). If you're bending your bolts you're already using a very marginal solution and should fix that..

You could use the spacer as just a ring that fills the space, or bolt it to the hub and put studs in the spacer. No big problems with either concept as long as you respect the basics of bolt technology and establish the right forces for the materials and construction used.

Yes Miro, it is science but it can be calculated and predicted.

regards
Tom

[miro-1980]

Thanks, Tom.

You can make the most difficult issue seem simple, so even I can understand. To put it in plain terms is a gift.

This was my notion of how this works in principle.
Given the rear hub construction have very tight fit of the spacer to the hub on one side and to the wheel on the other, so the bolts do not really have to keep it in position.

Situation with the front is bit different. The hub front is flat , and the disk does on a hub directly and a thin spacer is bolted to the hub . The spacer is positioned by the hub. The wheel is centered by the center on opening of the wheel going onto the spacer. So there is nothing to hang on to.

FRONT HUB .jpg (81.18 KiB) Viewed 8407 times

small front spacer.jpg (70.02 KiB) Viewed 8407 times

RIMG7506a.jpg (73.88 KiB) Viewed 8407 times

This is assuming I will put in the ATE solution in place. If Brembo goes in we will figure it out , all on the same principle. The wheel and the hub are to be kept tight by bolts , but supported and solidly centered on something ...

Does it make sense ?

Miro

[TomLouwrier]

Hi Miro,

Thanks.

@pic FRONT HUB
OK, Abarth chose to locate the brake disc on all 4 holes by the shank on the base of the studs. They must have had a good reason for that, but for now I can't see it (yet).
Your front wheel spacer is indeed not as extreme as the one at the back. It offers the same face to the wheel (pic RIMG7506a.jpg) as does the disc you showed us last night (pic brembo front.jpg). The wheel is centred by the nose in the middle, in true Fiat tradition this would be about 59mm. Right? :-)

So as a construction this will work, only thing is that your studs will be shorter than intended because of the spacer. I can not tell you if you will have enough length left for the wheel nuts. You may have to source longer studs, but be aware of the material and the special shank. Are they replaceable at all?
The thread on these studs seems to have pretty fine pitch. That also points towards high clamping force and extra resistance against the nut coming off because of vibration. Logical for a rally car, no?

I'd be interested to hear about your rear hubs and the very fat spacers there. Why? How?

regards
Tom

[miro-1980]

Why ,

The answer is simple. History. Development of this car history of course...

Originally the suspensionn was standard 131. With the wider arches on the fenders (wings) the wheels looked simply funny.

Thus the spacers.

Once we moved to original abarth hubs in the rear we still used standard parts ( disks were standard Stradale 227 and calipers were from 125p, thus the spacers were still useful. Also I really grew used to the very wide rear.

Now that we move for full abarth the spacers are needed to fit the wheels . Look at this picture:

PIC00552.JPG (70.73 KiB) Viewed 8464 times

Without the spacer there is no way to fit the wheel.

Actually the current width of the rear (with spacers) is + 80mm compared to Gr 4 !

I am so used to wide rear that I am not sure I will give it up, though everything will depend on tests we will do later this season.

The front ? We will see what setup we will use : ATE or Brembo or combination. If ATE this is used the specer is required to gain necessary space under the wheel . Otherwise the caliper will not fit in the CD68 15 inch wheel.

If we go for Brembo the spacer will (probably) not be required.

This was a very good question Tom, which got me thinking . Let us see what happens on tests.

Miro

[miro-1980]

Brembos and disks in hand .

Some pictures for you to enjoy...

PIC00559.JPG (77.27 KiB) Viewed 8403 times

PIC00560.JPG (90.09 KiB) Viewed 8403 times

PIC00561.JPG (38.18 KiB) Viewed 8403 times

PIC00562.JPG (41.85 KiB) Viewed 8403 times

Miro

[TomLouwrier]

Four piston radial Brembo and (very nice!) two-piece disc with alloy bell. Powerful stuff, but this is no 70's technology Miro.

regards
Tom

[miro-1980]

I know but this is the best we could do ...

Miro

PS Once the season is over we will try to get the RS ATE calipers with a disk that we will try to replicate ( based on the one shown above.

As you know the disk is the real problem !

M

[TomLouwrier]

As you know the disk is the real problem !

Don't I know it... spent some nights going through catalogues for that one... :-)
Let's see if ATE made a caliper in that series but with a 54mm piston in stead of the existing 48mm. That would really improve things, more than disc diameter alone.

regards
Tom

[miro-1980]

As I suspected , life has many surprises, especially on the 13th !

The Brembo looked nice but could not be mounted , even if we made a new mounting plate with smaller mounting hole spread. It just could not fit over the ball joint of the front arm. The only option would be to go for a uniball instead of the ball joint. We do not have such arm and I really want to avoid this. The car front is hard enough and tight enough and going for a full uniball suspension on the font would endanger the integrity of the 30+ year old chassis.

PIC00563a.JPG (56.06 KiB) Viewed 8319 times

So ( as I suspected ) we were forced tor the best solution. The ATE calipers and the great two piece disk with aluminum bell !

Ate with new disk (4).JPG (55.79 KiB) Viewed 8319 times

Ate with new disk (3).JPG (49.58 KiB) Viewed 8319 times

Ate with new disk (1).JPG (55.93 KiB) Viewed 8319 times

Ate with new disk (5).JPG (46.92 KiB) Viewed 8319 times

To answer a previous: why spacers on the front. I think this picture ( though not very sharp) answers this question. Putting a 15 " qhwwl on this is impossible without the spacer .

Ate with new disk.jpg (44.45 KiB) Viewed 8319 times

So , a compromise was struck.

I am actually very happy , as this allowed to use an original gr 4 specs caliper , instead of the a later technology Brembo caliper.

All's well that ends well.

Miro

[miro-1980]

On a somewhat different subject ...

I had an oil leak in my 2000 Spider ( 124 spider CS0, 2.0 fi)

The leak was from two places :

1/ exhaust header stud (furthest from the front of the car)

stud location.jpg (83.12 KiB) Viewed 8316 times

oily stud .jpg (75.7 KiB) Viewed 8316 times

This is a common problem when the whole drilled for the stud is just a bit to deep ( of someone forced it too deeply into it - the stud hits an oil channel. Hence the leaking . This was a problem ever since I bought the car in 2005. I thought it was the head seal... Well it was not . The leak was rather small, and had no effect on cars performance or ability to drive it. Loss of oil was minimal, but it was ANNOYING. The oil would drip over the exhaust header causing unpleasant smoke . When it was hot and I drove few hundred kilometers the burning oil smell was getting on my nerves. The proper way of repairing it would be take the engine out , take off the exhaust header, remove the stud and than use a sealing compound. However, I am not about to do it for such annoying but small reason. I will degrease the stud and and the header seat for the stud as well as the bolt and the washer and use a special high temperature sealant that is activated by absence of oxygen (applying it to the seat the stud the washer and the bolt). Will let it dry for a day and fire up the engine to see the results. I expect the problem to be gone ...

2/ the oil filter mounting pod.

I recently replaced the standard alternator with a slightly stronger one ( 65 AMP). Checking result of my work I realized that a small oil leak I had ever since the alternator mounting bolt got loose and of head damaged my radiator. As the leak was small I though nothing of it .

Returning from recent rally I drove the car over a distance of 150 km on a highway. Driving 100 km/h got boring so I accelerated once to well above the limit of 140 kmh. When I unloaded the car form a trailer I noticed a big oil stain under it. Tried to investigate it, believing this is likely a leak from loose oil filter or bad rubber oil seal. Well it was not ... The oil was dripping over the filter. Had to take it off and after numerous diagnostic attempts I identified the source of the problem. There is a minute crack on the side of the pod , where the bolt to hold the alternator is inserted. Upon very detailed analysis of the pod I managed to confirm this was the problem .
See location and the crack under 50 x magnification

crack location .jpg (78.68 KiB) Viewed 8316 times

crack x 50 .jpg (104 KiB) Viewed 8316 times

This is the first time I found out what micro crack means , and how much oil can leak through such a small crack

The whole part will be replaced , but before I can put my hand on a proper part ( all suppliers are on vacations) I will have the pod welded.

Incidentally I realized there were three oil filter pods : ( this may not apply to RWD vehicles , and this is not en exhaustive list, as other Fiats may have used similar or same pods)

- one for 131 with alternator mounts on the exhaust side (cast iron)

pod 131 .jpg (103.35 KiB) Viewed 8316 times

- one for 124 spider with alternator on the intake side ( pre 1980) - cast iron

pod 124 pre 1980 .jpg (65.57 KiB) Viewed 8316 times

- one for 124 spider with alternator on the intake side ( pre 1980) alloy

124 CS0 .jpg (65.63 KiB) Viewed 8316 times

Note they all have the sale fittings ( fit each model , but cannot be used interchangeably , when you must mount the alternator on the same side as oil filter.

The problem of using the older cast iron version of the pod for 124 spider CS0 is that the belt cannot be aligned properly. The pod places the alternator about an inch further away from the front. The fact the alternator is mounted from the above , rather than from the below does not make any other difference.

Thought some of you may find it interesting ...

Miro

[Guy Croft]

MODEL POST!

over and above the extraordinary documentation of your 131 MM, the post (above) about the oil leaks on your Spider is certainly useful and interesting. Put across of course in your usual excellent style with superb photographic backup.

G

[miro-1980]

Guy,

As this is an elite club : "noblesse oblige"

Thanks for your recognition.

Miro