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Okay guys it’s been awhile !

my car has been off the road for around five years while I build a house and garage.

 I have just recently finished a rear Subaru differential conversion and I’m now running Four pot callipers to the front and mgf tf tear discs and callipers to the rear.

I have just made new brake lines for the rear, connecting up to braided hoses going to the calipers I have bled  the system with my easy bleed and I’m getting no air bubbles in the system 

  My brake pedal is soft and spongy and I have lots of travel 

Should I be looking at a different master cylinder with a complete change of front and four pots and rear caliper set up any advice greatly appreciated

Rob

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Hi Rob. Glad to see you are back on the car.

What size master cylinder is fitted? I have GT6 fronts and mgf rears, and a .70 and that seems to work well. You "may" need a .75 depending on how large to 4 pots are?

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Hi Rob,

Good to hear from you :smile:

Conventional fluid or silicone?  The latter can be a right sod for hanging on to small bubbles of air - easier to shift if bled again after waiting a couple of days.  I wouldn't completely rule out there still being a small amount of air in the system - it doesn't take much.  Are all the calipers mounted so the bleed nipple is at the highest point?

Like Clive, I'm curious about M/C size.  If still the std Spitfire 5/8" bore it's probably too small and that will give a longer travel to bite point though not necessarily very spongy.  All new pads/discs can also result in a slightly springy feel that will go as they bed in.

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Good to be back on the car guys, 

 

i am am a total fud ! I am using Canleys front caliper and vented discs and have not bled both bleed nipples on each caliper, I did my initial bleed with the front wheels on and was impressed with the fact you can access the bleed Nipples with the wheels on only to find a second bleed nipple on the outside of the caliper also!

As I have now bled all bleed nipples all is much better, however I do think I have the smaller master cylinder and will need to swap that out. I think Clive is right with the .75, any suggestions on make?

I have refurbished the rear caliper with new seals and Pistons with new paint and I am running dot 5.1 fluid as I have always done , I got rid of silicone 10 years ago because I couldn't get it to work properly ! I have ensured that bleed nipples are up. 

Working on handbrake now until I order the new MS.

hope you guys are well and thanks for the welcome.

 

Rob 

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Be careful about going too large on the MC. a .75 can make std breaks feel quite wooden.

If you have a 5/8 (0.65) on there at the moment (that was std spitfire size), a change to .70 may well be adequate. That is what I am using and has a good feel. I did have a .75 but that was too hard and too short travel.

Afraid I have no idea what is a good make thesedays. Genuine NOS with a new seal kit? Plenty of cheapish repros about, but no idea on how good they are. 

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If you have an acceptable pedal it might be worth driving the car a bit and seeing how they settle.  All new pads/discs etc won't be fully representative.  Also depends a bit on personal preference.  If you find you'd like a shorter pedal feel then I'd be trying a 0.7" next as Clive says.

I've put a 0.75" on the GT6 on the basis that it also has a servo, which tends to cause a longer, squashier pedal.  Haven't driven it yet.......  Vitesse has a smaller  that factory 5/8" M/C to try and get pedal pressures down a bit.  This does help, but means that the back brakes have to kept adjusted up to maintain a decent pedal.

As to what M/C.... for the brake I'd say don't cheap out - get a decent one - Girling/Lucas/TRW.  There are many cheaper options, some of which are ok (fairly faithful Girling copies that will even take the Girling kits), others are total shite (Wilwood!)

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I may have a original girling 3/4 which is .75 ? But may do as you say Nick and give it a road test prior to any final decision 

with those guys using the mgf callipers to the rear how have you routed the handbrake cable ?? 

Thanks for the responses already received 

Rob 

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FWIW just had similar problems with my 2500. Turns out I had worn seals in the M/C. Being in New Zealand we have duel circuit systems with front and rear working independently. Fluid was getting back past the rear piston. Had cylinder resleeved in stainless and rekitted.

Now have perfect brakes.:biggrin:

Tony.

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