Author Topic: 105 Rear Calipers on Alfetta  (Read 4269 times)

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NSharpley

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105 Rear Calipers on Alfetta
« on: July 29, 2020, 05:30:26 PM »
Pedal is crap after much bleeding.

Pumping the pedal does improve it though but still the pedal is crap.

The outer piston was pulling back a lot and leaving too much clearance to the disc.   Fixed that by pushing the piston out further without the pad in to move the pistons resting position.

But still the pedal is crap.

Any suggestions?  Anyone else run 105 calipers on the rear of their Alfetta?   Anyone had problems with them?

Ive also swapped the master cyclinder for a newer model (83 Giulietta).   Still the pedal is crap!
Current Alfa:
1975 Alfetta GT 2.0 Race car

Past Alfas:
1989 Alfa75 2.5ltr
1982 Alfetta Sedan 2.0
1976 Alfetta GT

MD

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Re: 105 Rear Calipers on Alfetta
« Reply #1 on: July 29, 2020, 05:56:55 PM »
You wouldn't be the first person that has had problems with bleeding brake and clutch systems. Well done getting some larger calipers to the rear rotors
I hope you also elected to fit larger diameter rotors at the same time. I am wondering what handbrake arrangement you came up with?

As for bleeding your system, if you have tried everything else, try reverse bleeding. That is to say from the bleed nipple back to the reservoir. Be sure to keep an eye on the later to prevent an overflow. Theoretically the calipers are at the lowest point and the reservoir is at the highest point. Entrapped air should rise from low to high.

BTW Keep in mind that the Alfetta brake systems tends to have a softer pedal due to firewall flex and the transfer bar arrangement to the booster.
Transaxle Alfas Haul More Arse.

NSharpley

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Re: 105 Rear Calipers on Alfetta
« Reply #2 on: July 29, 2020, 06:26:14 PM »
Have heard that suggestion before as it happens ... worth a try, thanks.

No handbrake required at this stage - track car only.

In fact I opted for the 105 calipers because I wanted to get rid of the standard calipers and the annoying adjustment feature.

In track applications the pedal would regularly disappear and the rear calipers would require regular readjustment.
Current Alfa:
1975 Alfetta GT 2.0 Race car

Past Alfas:
1989 Alfa75 2.5ltr
1982 Alfetta Sedan 2.0
1976 Alfetta GT

MD

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Re: 105 Rear Calipers on Alfetta
« Reply #3 on: July 29, 2020, 07:41:53 PM »
Oh  I see, a track car. Well you can still integrate a hydraulic handbrake into the rear circuit if you want one but I guess it is more of a rally application.

Stating the obvious here, your brake fluid boiling point will play a large part in the pedal feel and travel depth so use the highest rated stuff you can afford. Motul 660 I find to be the best in my application but it isn't cheap and requires regular replacement as well to maintain its rating. Ducting helps.
Thin/worn brake pad material also transfers more heat into the fluid affecting your pedal.
Transaxle Alfas Haul More Arse.

MD

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Re: 105 Rear Calipers on Alfetta
« Reply #4 on: July 29, 2020, 07:53:39 PM »
Here's an alternative conversion using 297mm vented rotors and Nissan caliper. You have to make removable service panels in the floor to replace the pads. Pad size is similar to the ATE units but better cooling and leverage.
« Last Edit: July 30, 2020, 06:38:51 AM by MD »
Transaxle Alfas Haul More Arse.

four90s

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Re: 105 Rear Calipers on Alfetta
« Reply #5 on: July 29, 2020, 09:12:56 PM »
Serious stuff MD.

Details of make and model Nissan to scavenge parts off?

Regards
Steve
Adelaide
Four90s
Too many others to list
(33 Alfas and some other things since 1979)

MD

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Re: 105 Rear Calipers on Alfetta
« Reply #6 on: July 30, 2020, 06:54:39 AM »
Hi Steve,

Nissan Skyline R34 GTT Engine: RB25DET 8/1998-2002 2.5L TURBO
Also R32 GT-R Engine: RB26DET 6/1989-8/1993 and the 300ZX Z32 VG30DETT 1989-1999.

Basically it is the DBA Rotor 908 the specs of which are : R 908  V 297 63 18 16 68 5

They are a 16mm vented rotor. You have to use the ATE original rear centre from a shagged disc and fit it to the centre of the DBA 908 rotor so it's not a straight up bolt on. This is close to the limit of the rotor size that can be used here before the rotor starts to foul the movement of the DeDion tube.

The other alternative is to install the rear brakes outboard.

Unfortunately none of this stuff is going to make much difference to a crappy pedal if there is some fundamental problem with the system as a whole. It will in terms of heat dissipation in the rear circuit.
Transaxle Alfas Haul More Arse.

aggie57

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Re: 105 Rear Calipers on Alfetta
« Reply #7 on: July 30, 2020, 07:52:22 AM »
Do you still have the handbrake connected?  It's the handbrake that works the adjustment in an Alfetta.  My technique was to push firmly the footbrake then madly pump the handbrake for a few minutes.  AFAIK that makes sure the little circlip inside the piston is properly seated and the piston itself is adjusted.
Alister
14 Alfa's since 1977. 
Currently 1973 GTV 2000, a couple of Mercs,  a '14 Beetle (yes, seriously......), 2020 911 C2S (manual!)
Gone......far to many to list

Gusto

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Re: 105 Rear Calipers on Alfetta
« Reply #8 on: July 30, 2020, 09:27:24 AM »
I had this problem on my 75 when I put 105 callipers on the rear. The rear pistons would retract. Everything new or rebuilt and no air in the system. After advice from Mike. I installed a 2lb check valve in the rear brake line. Problem solved. Best brakes Ive ever had.

bonno

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Re: 105 Rear Calipers on Alfetta
« Reply #9 on: July 30, 2020, 10:12:37 AM »
Hi NSharpley
I had a similar problem with my Fiat X19 after reconditioning the brake calipers and fitting new pads. Tried bleeding brakes from the rear furthermost from master cylinder and working forward, without any luck. Purchased myself a pressure bleeder and pressure bled the brakes and fixed the pedal problem. I have photo of a similar unit available on ebay that might be worth a try.
Cheers
bonno
now
83 Alfetta GTV
05 156 JTS manual
past
00 156 selespeed
72 1750 GTV

carlo rossi

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Re: 105 Rear Calipers on Alfetta
« Reply #10 on: July 30, 2020, 03:24:01 PM »
there is a special technique for the rear calipers
and i would say 90% of alfettas are ill adjusted mine included '
its a dark art but i believe there are people with knowledge
find a retired euro mechanic must over 50 years of age
current cars
red 83 gtv 2.0


previous cars
Red 76 1.2/1.5 alfasud ti
white 79 alfetta 2000
alfetta 74 1.8
escort Lotus twin cam
bikes
ducati 900 ss 1979
moto morini 3 1/2 sport 1975/6
Moto morini 3 1/2 valentini speciale 77 oh and a deltek rockhopper

Alfetta77

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Re: 105 Rear Calipers on Alfetta
« Reply #11 on: July 30, 2020, 04:51:52 PM »
Agree re the value of a pressure bleeder, here is another option, has an adapter available that fits an Alfetta clutch and master cylinder https://www.autoinstruct.com.au/product/motive-products-brake-clutch-power-bleeder-1-9l/. Word of warning though, make sure you use plumber's (PTFE) tape on the threads, particularly on the master cylinder, as it is a looser fit. You will then avoid spilling brake fluid everywhere like I did!
Current:  Alfetta GTV 1977 Silver
Previous: Alfetta GTV 1980 Red

NSharpley

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Re: 105 Rear Calipers on Alfetta
« Reply #12 on: August 10, 2020, 05:25:04 PM »
Thanks for all the replies folks.

A few people mentioned rear caliper adjustment ... just so we're on the same page; these are 105 rear calipers so have no adjustment and no handbrake mechanism.   Precisely why I wanted to use them.   Continually readjusting calipers between sprints was annoying, not to mention the gradually decreasing pedal as the standard rear calipers unwind themselves.

The main mistake I made here was mounting the calipers upside down so the bleed screw was at the bottom.   Very accessible but just wont work.   Ive now swapped them around and bled them.   A thousand times better but still not 100%.   First press of the pedal and it goes very close to the floor.   Second press and its a good pedal.   This is obviously no good still.

I did have the piston retraction problem ... took the pads out and pumped the pedal so the pistons resting position was further in.  Jammed the pad back in and that now seems a lot better.

Saying this ... I feel like the issue might still be piston retraction.

Will go down the path of the check valve and see how that goes.

Appreciate all the feedback.

Current Alfa:
1975 Alfetta GT 2.0 Race car

Past Alfas:
1989 Alfa75 2.5ltr
1982 Alfetta Sedan 2.0
1976 Alfetta GT

bazzbazz

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Re: 105 Rear Calipers on Alfetta
« Reply #13 on: August 10, 2020, 07:13:49 PM »
The main mistake I made here was mounting the calipers upside down so the bleed screw was at the bottom.

I believe the word you looking for here is "DOH!". Definitely falls into the "seemed like a good idea at the time" category.   ;D

Don't give in, never say die, you'll get it sorted.
2004 Alfa 156 2.0 JTS Sportwagon (Patty)

NSharpley

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Re: 105 Rear Calipers on Alfetta
« Reply #14 on: August 10, 2020, 07:20:08 PM »
Here's an alternative conversion using 297mm vented rotors and Nissan caliper. You have to make removable service panels in the floor to replace the pads. Pad size is similar to the ATE units but better cooling and leverage.

This all looks very nice, Ill give you that, but I want to keep mine as "Alfa" as possible.

I have a set of ventilated discs ready to go.   Just need spacers for these ATE calipers and some longer bolts.   Happy with that solution.
Current Alfa:
1975 Alfetta GT 2.0 Race car

Past Alfas:
1989 Alfa75 2.5ltr
1982 Alfetta Sedan 2.0
1976 Alfetta GT