hi guys,
OK, here's my views on the subject. Feel free to bash them ;-)
Anyone who actually did these conversions, please follow up as Guy asks.
OEM and the bolt on upgrades
Uno Turbo
Personally I've never seen this one in real life. Miro reported some time ago about the Uno turbo conversion (
viewtopic.php?f=14&t=1901) as a bolt on modification. (Miro, are you reading??).
Performance-wise the gains are small: you'll have the same caliper (48mm) and MBC (19mm) pistons. The front disc will be 240mm over the 227mm standard set you'll find in nearly all Fiats from the 60's and 70's, so you'll get 240/227= 106%. Nice, but not exactly shocking. It is my belief that most who do this conversion in fact feel the difference between their old, ineffective brakes and the rebuilt, well greased and properly sliding ones.
Main improvement is that the discs are vented, so you'll keep the brakes cooler for longer. A big plus when you're doing track days or going for rally fun in the mountains.
You can run this with the original rear brakes and MBC without upsetting F/R balance and pedal travel / force.
I've given up on this option because the parts are made of unobtainium and the gains not worth the effort.
124 DS and Volumex
The late 124 Spiders got their front brakes from the Argenta which used the standard 80's Fiat setup: 54mm caliper piston on a 257mm disc. This combo gives an improvement of about 44% over the 48mm/227mm. Cars got a lot heavier in those days because of safety and comfort requirements.
With this they fitted an enlarged rear caliper on the original disc: 38mm on 227mm non-vented (was: 34mm).
You'll find that in true Fiat-partsbin-style these rear calipers were lifted off the 125 and you can still get them as replacement parts for the FSO Polski. They were also used on the Monte I think.
(By the way: all this tallies nicely with the things I said earlier about F/R ratios: 65+/35- for North-South drive lines and 55/45 for mid engined cars.)
These 38mm rears should be a bolt on, but the construction is still the 1st generation sliding caliper with exposed wedges so it'll be prone to sticking and needs good regular maintenance.
As far as I know these models had a slightly larger MBC and booster (possibly from an Alfa 164 or Fiat Croma) to compensate for pedal travel and force, which fits the calcs.
Aftermarket kits
Whoa / Wilwood
The Whoa-kit looks neatly executed, it's based on a Wilwood caliper.
I have looked at their site and catalogues and no doubt Wilwood makes good products.
However.
The calipers in the Whoa don't feature dust/water shields. They will have no OEM references and certainly no E-markings (Euro type-rating). This makes them unsuitable for use on the public roads. You will have a car that is illegal to drive and thus not insured. That is two major problems in one sentence.
Wilwood themselves make disclaimers about their products being for track / racing / off road use only and I've not seen one reference to high way use. Get into an accident, even one that has nothing to do with any brake failure at all, and you will be in very big trouble.
Another aspect is availability of the pads, especially outside the USA.
Allison / Fiat OEM
The Allison kit is based around the brakes from the current Fiat 500 range. Parts / pads will be available easily. The calipers are designed and tested for years of regular every day use and abuse. With big firms like Fiat and its OEM suppliers (Lucas, Bosch, Valeo) you can be very sure there's a lot of development and testing done on the parts.
I have suggested to Mark he redesigns his caliper carrier (adapter) to fit a vented 240mm disc as found on the Uno Turbo and some younger Fiat models (Palio, Siena). This is not a difficult mod and it would make his set work under original 13" wheels too.
Now if you plan on using your car for track use only, this about sums it up. You make your choice, pay at the counter and fit your new kit. Everyone expects you to understand and handle all aspects of modifying a vital safety system on your car. If not, you are supposed to employ someone who does.
And since this is a racing forum, we could rightfully end the discussion here.
Most of us however, including the anonymous readers, either have a 'fast road' or a rally car. Most rallies demand that the participating cars are fully road legal and registered. So everyone in this section of the audience gets to deal with:
The law
In order to get modified brakes officially accepted, you have to have them examined and approved for use on your road going car.
In Germany and The Netherlands it is possible to have individual modifications inspected and accepted. You will have to convince the inspecting body that your modifications are both well engineered and properly executed, so get your dossier up to scratch (drawings, calculations) and invest time and money in good fabrication of parts. The use of OEM (Fiat) parts will help you show the inspector / inspecting body that your car will be at least as safe as it would be if it had come from Turin this way.
In France it is nearly impossible to get anything changed on a car unless you get official paperwork from the factory that they endorse the modification
and in fact support it as one of their own constructions. This goes for engines, brakes, suspension.... Bonne chance, mes amis!
Getting your car past a regular check (MoT, TuV, APK, CT... whatever) is not enough. I've heard enough silly people claiming the modification is 'good' because it managed to fool the guy at the local garage when he did the yearly check. Don't try that. You will always lose when things comes to that point.
regards
Tom