Likes Likes:  3
Thanks Thanks:  2
Results 1 to 8 of 8

Thread: What size rear brake master cylinder?

  1. #1
    10+ Posts
    User ID
    33843
    Join Date
    Aug 2022
    Location
    taunton, somerset, UK
    Posts
    18
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Rep Power
    35

    Default What size rear brake master cylinder?

    I've spent most the afternoon on this & gone round in a circle.

    The trike:

    late 90s Vmax with English axle (MK1 ford escort). Compomotive 15" rims 225/50 tyres. Has the disc brake conversion. Not sure of the exact piston size but estimate 30mm. Single piston. 9.5" rotors. Pads app 1.25" tall. Pedal leverage ratio 4.75:1

    No idea what master cylinder has been fitted. Looks like it's from a car. Can only read the make Brembo. Body diam is 30mm.

    There is some weeping where the reservoir tube joins the body but it's not much. No idea how old the fluid is. Brakes feel mushy.

    Thought I'd try & find out what ought to be on there before doing anything or spending money.

    I went down the 'would the Vmax OEM one be right' rabbit hole. It's 13mm. Using bike calculations/chart I was getting I need 12mm.

    I looked here to check only to find 3/4" (19-20mm) or more being talked about so now I'm lost.

    All advice gratefully received.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	GEDC2396.jpg 
Views:	9 
Size:	1,019.8 KB 
ID:	110342  

    Click image for larger version. 

Name:	GEDC2398.jpg 
Views:	7 
Size:	599.3 KB 
ID:	110343  

    Click image for larger version. 

Name:	GEDC2432.jpg 
Views:	5 
Size:	978.0 KB 
ID:	110344  

    Last edited by J-max; 10-30-2022 at 01:21 PM. Reason: add pics

  2. #2
    3750+ Posts
    Gold Club Member
    Marc H's Avatar
    User ID
    6801
    Join Date
    Dec 2011
    Location
    Evensville,Tn.
    Posts
    3,953
    Thanks
    0
    Thanked 2 Times in 2 Posts
    Rep Power
    300

    Default

    I would contact Brembo with any numbers you can find on it.They make everything from high performance street car upgrades to full on race applications.Don't discount that it may be a clutch master also.That mounting sure looks like automotive to me.
    Do not argue with an idiot.He will drag you down to his level and beat you with experience.
    Its dog eat dog world and i'm wearing milkbone underwear.
    1989 GL1500 Goldwing (SOLD)
    2006 GL1800 CSC

  3. #3
    16500+ Posts
    Tech Contributor
    Gold Club Member
    Jack Klarich's Avatar
    User ID
    24367
    Join Date
    Oct 2016
    Location
    Jax, Fla USA
    Posts
    16,888
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Rep Power
    300

    Default

    3/4 or 7/8 bore master should work fine
    Nuff Said," Were Burnin Daylight, Lets Ride"(Sober 36 years)
    Current ride : 2021 FREEWHEELER M8

  4. #4
    10+ Posts
    User ID
    33843
    Join Date
    Aug 2022
    Location
    taunton, somerset, UK
    Posts
    18
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Rep Power
    35

    Default

    Quote Originally Posted by Marc H View Post
    I would contact Brembo with any numbers you can find on it.They make everything from high performance street car upgrades to full on race applications.Don't discount that it may be a clutch master also.That mounting sure looks like automotive to me.
    I've correction. It's a Bendix I (i). I'm Dyslexic. It has No 653 but I can't find any info.

    From appearance only it looks like a clutch M/C for a Fiat Uno (19mm) so bonus points for you.

  5. #5
    10+ Posts
    User ID
    33843
    Join Date
    Aug 2022
    Location
    taunton, somerset, UK
    Posts
    18
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Rep Power
    35

    Default

    posted in error.

  6. #6
    10+ Posts
    User ID
    33843
    Join Date
    Aug 2022
    Location
    taunton, somerset, UK
    Posts
    18
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Rep Power
    35

    Default

    Quote Originally Posted by Jack Klarich View Post
    3/4 or 7/8 bore master should work fine
    3/4 - 7/8 seems big to me. I've now seen a chart for bikes & a calc for cars & they're saying anything from 10mm to 1/2".

    Could you give more info on how you arrive at 3/4 please?

  7. #7
    16500+ Posts
    Tech Contributor
    Gold Club Member
    Jack Klarich's Avatar
    User ID
    24367
    Join Date
    Oct 2016
    Location
    Jax, Fla USA
    Posts
    16,888
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Rep Power
    300

    Default

    Quote Originally Posted by J-max View Post
    3/4 - 7/8 seems big to me. I've now seen a chart for bikes & a calc for cars & they're saying anything from 10mm to 1/2".

    Could you give more info on how you arrive at 3/4 please?
    3/4 is close to the Bendix 19mm you referenced, many masters are 3/4-7/8

    smaller diameter will work but your pedal travel will increase
    Nuff Said," Were Burnin Daylight, Lets Ride"(Sober 36 years)
    Current ride : 2021 FREEWHEELER M8

  8. #8
    10+ Posts
    User ID
    33843
    Join Date
    Aug 2022
    Location
    taunton, somerset, UK
    Posts
    18
    Thanks
    0
    Thanked 0 Times in 0 Posts
    Rep Power
    35

    Default

    Update:

    Me being me I had to try the 1/2" oem - otherwise it would have bugged me. Didn't even start to operate the rr brakes.

    Made some proper bracketry for the Bendix & fitted an external reservoir (oem size was inadequate for the bigger m/c) & this is doing a good job. Not leaking either - so far.

    Click image for larger version. 

Name:	GEDC2474.jpg 
Views:	2 
Size:	995.3 KB 
ID:	111413

Similar Threads

  1. Master cylinder for rear brake
    By jimmib in forum Harley Trike Conversions
    Replies: 8
    Last Post: 07-15-2020, 12:49 PM
  2. Master cylinder size
    By starrider1946 in forum VW Powered Trikes
    Replies: 6
    Last Post: 03-21-2018, 10:00 PM
  3. Rear brake master cylinder reservoir idea
    By Dirtydan in forum Victory Trikes
    Replies: 13
    Last Post: 08-03-2016, 09:40 PM
  4. Rear Brake Master cylinder
    By Kiwi in forum New Member - Welcome
    Replies: 9
    Last Post: 02-05-2016, 11:28 AM
  5. rear brake master cylinder spec needed
    By lardarse in forum Harley Tri Glide
    Replies: 10
    Last Post: 12-31-2013, 03:18 AM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •