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850 front brake calipers?

Discussion in 'Rear-Engine Fiats' started by Fiat4Fun, Jun 4, 2018.

  1. Fiat4Fun

    Fiat4Fun Low Mileage

    Location:
    Sunriver, OR
    Howdy,
    Does anyone know if a 124 front brake caliper would work on a 850?
    I assume not, since they list them as a different part number.
    Looks similar in a picture. I remember reading a long time ago about it.....
    My pistons seem frozen, so what to get a replacement....
    Thanks
    Bob
     
  2. kmead

    kmead True Classic

    Location:
    Grand Rapids, MI
    No they won’t.

    You can buy new pistons, as the housings are aluminum they can generally be reused.

    I bought a set of new pistons on eBay from a German seller. I believe US eBay has a seller of the pistons as well.

    Be sure to replace your rubber front brake lines at the same time as they can fail internally and block the return flow of the fluid creating a locked situation.

    Karl
     
  3. NM850

    NM850 True Classic

    Location:
    Albuquerque NM
    Or I have some used calipers....
     
  4. Fiat4Fun

    Fiat4Fun Low Mileage

    Location:
    Sunriver, OR
    Cool, send me a message, and we can work something out,,,,, Can pay for them, or maybe I have something you need ;-)
     
    NM850 likes this.
  5. Mark

    Mark FIATFREAK

    I have 124 calipers on my ‘68 850. I swapped the front hubs and brakes to those from a newer 850 but used 124 calipers. I think the 850 calipers were similar or the same as those on my ‘74 X1/9. This is all subject to memory.


    DBCBECF9-ABAC-4620-9B6F-D56427C15FCC.jpeg .




     
  6. kmead

    kmead True Classic

    Location:
    Grand Rapids, MI
    They may physically fit the sliders but I am pretty certain that the pistons are notably different in diameter which means you will change the brake bias further forward. Added to that the limited diameter of the master cylinder you will have pretty extended pedal travel.

    As X and 124 calipers are the same parts assuming you wanted to try you have choices.

    I wouldnt but I am not particularly adventurous.
     
  7. fiatfactory

    fiatfactory Steve Cecchele

    Location:
    Western Australia
    there are two types of 850 front calipers... one is the same as the usual 124/x19 caliper, exactly the same piston etc

    the other type is totally different... this is the caliper used on the odd disc type 850's...by ODD disc I mean they are not the same as a "regular" Fiat 227 x 10 disc... and unfortunately you can't interchange the disc and caliper as the stub axle and hub are different.

    You can retro fit the late style hub / disc and caliper to any 850, but it requires a stub axle change (which usually means replacing the king pins and bushes on the secondhand parts you buy to do the job)

    caliper piston size is the same for both types of caliper, but the pistons are unique for the early calipers.

    SteveC
     
  8. Jeff Stich

    Jeff Stich True Classic

    Location:
    Norco, CA
    The "late" style 850 caliper is similar to, but not the same as, the 124-X1/9-128 caliper. The length (depth) of the 850 caliper body is shorter, & the 850 brake pads are about half as thick as on the 124-X1/9-128 caliper. That's why front 124-etc. pads won't fit on an 850 - way too thick!


    Correct. The early 850 front brakes are like those on the Fiat 1100R. Real pain to service! :(
     
  9. NM850

    NM850 True Classic

    Location:
    Albuquerque NM
    My 68 has the early style brakes. By "real pain to service" are you referring to parts availability? I stocked up and have enough to last me and the next owner.
     
  10. RJ80

    RJ80 True Classic

    Location:
    Kitsap, WA
    That didn't stop Mark Allison from installing a set of 124 calipers on my coupe, since sold. To his credit, the car did stop alright after (though I only drove the car around town and never had to stop in a hurry). The pedal travel did seem longer -- first half of travel did nothing.
     
  11. Jeff Stich

    Jeff Stich True Classic

    Location:
    Norco, CA
    Parts availability for these has always been hit-&-miss, even moreso these days; the pads can still be found fairly easily, the rotors less so & often very costly.

    "Real pain to service" refers to the fact that you have to remove the main wheel bearing/hub assembly from the spindle first in order to change the brake rotor. Add in 2 new replacement spindle/hub retainer nuts when doing this, plus correctly tensioning & staking those nuts afterwards. Just to change a rotor? (a very ass-backwards design) Not to mention the different 1.25mm "fine-thread" pitch of the front lugbolts vs. the 1.50mm "coarse-thread" on the rears, resulting in an easy opportunity for cross-threaded (torn up) lugbolts & front rotor/rear hub lugbolt holes. With the front rotors having the lugbolt-retaining threads in them (not the hub), cross-threading the rotors on accident can get expensive! :(
     
    NM850 likes this.
  12. NM850

    NM850 True Classic

    Location:
    Albuquerque NM
    It's been so long since I've done it I forgot all that. I changed the brakes and the kingpins early in my ownership. At the time I bought two of everything and the parts are still on the shelf but you are right it would be easier to switch to later brakes , I have those parts too but haven't found the need.
    My 67 will get either later brakes or a completely modern and hopefully much lighter system of my own design.
     
  13. RJ80

    RJ80 True Classic

    Location:
    Kitsap, WA
    Just as a PSA, I've got a set of early-style 850 rotors if anyone is in need. They are not new, but were resurfaced and found to be within spec by the late, great John Edwards.
     
  14. Frank L. Di Gioia

    Frank L. Di Gioia Low Mileage

    Location:
    las vegas, nevada
    Just to add to the complications of 850 calipers I'll toss this out there. My "new" 1967 HP race car project has the "old" style front calipers and rotors. Almost that is. They are held on with the 4 stout springs and rather than the "new" style sliding wedge with clips it has the nylon (?) trim similar to door edge trim. However the caliper bodies have provision (recess in center of caliper back) for the screw and lock nut adjustment but have not been drilled out or tapped. Late style dust boots and caliper seals fit perfectly. My possible solution to the whole thing is to convert front and rear to NEW (2012 on) style Fiat 500 Abarth brakes. Since my knock around car is just such car I've got some parts to try and fit. The rear disc rotors fit! I'd imagine the front vented rotors may have to be turned a little to clear 14" rims. I'll post when that project starts. In the "old" days adding 4 wheel disc brakes worked fine using a Multiplia master cylinder.
     
  15. kmead

    kmead True Classic

    Location:
    Grand Rapids, MI
    The negative to changing to the new calipers is the new 500 caliper pistons are 54mm and will significantly change your brake bias more to the front.
     
  16. Frank L. Di Gioia

    Frank L. Di Gioia Low Mileage

    Location:
    las vegas, nevada
    In my past experience changing the front and rear calipers will result in the same proportioning but the stock single MC will probably go to the floor before acting on forward movement. Hence the larger MC if staying in the single piston field. Insurance comes in the form of a bias adjustment mounted in the tunnel and having the knob around the emergency brake area. Small diameter SS brake lines (flex) help keep it from getting mushy. As pointed you out there is a larger front piston AND a front heavy factory bias to start with. In days past my engineering consisted of a friend watching while I locked a 4 wheels in a sand covered street. When all 4 locked at the same time bias adjustment was deemed "spot on." But then at Cars & Coffee having 4 wheel discs and vented/drilled rotors is worth at least 50+ points. If/when done I'll report what actually happens on an Auto-X course. In the meantime it's back to rust removal....
     

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