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Fixing the ATR setup front brake feel...

Chassis/Brakes/Steering/Wheels discussion
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RattyMcClelland
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Fixing the ATR setup front brake feel...

Post by RattyMcClelland » Sun Sep 06, 2020 9:53 pm

Scott560 wrote:
Sun Sep 06, 2020 9:44 pm
Don't fancy a track day at abingdon do you ratty? Can compare and contrast then lol.
What date is it?
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Fixing the ATR setup front brake feel...

Post by Scott560 » Sun Sep 06, 2020 9:55 pm

16th October - got a few work friends going too, including aquaintence with mint DC5.
'00 UKDM 2.2VTI H22a8
'21 'e' Advance

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Fixing the ATR setup front brake feel...

Post by Sailor » Mon Sep 07, 2020 11:24 pm

Remember, the fluid pumped is proportional to the square of the diameter, not just the diameter. You'll get 12% more if you go from 15/16 to 1 inch.
And be better matched to the calipers.
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Fixing the ATR setup front brake feel...

Post by Scott560 » Tue Sep 08, 2020 8:11 am

Well remembered sailor! Strangely, I remembered that when looking at the calipers.

ATR fronts are 38+42mm pistons, which is near enough the same area as the single 57mm caliper of the prelude 282setup , so in theory shouldn't be much in it.

The ATR rears , whilst the discs are the same diameter and only 1mm thicker, the rear piston is much larger...

Then it occured to me that perhaps the ATR has longer stroke on the MC (its not just about diameter!), and the pedal mech allows more stroke, and servo assisted more to counter the lower leverage.
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Fixing the ATR setup front brake feel...

Post by Scott560 » Tue Oct 13, 2020 8:17 am

Starting to get annoyed with this now lol. :evil:

In prep for Fridays track day I did:

1) Swapped the 17inch wheels for the 16s with federal track tyres.
2) General inspection, nothing loose except exhaust heat shield on the backbox, only 1 bolt left holding it on lol - removed... No fluid leaks...
3) Took off the front carrier/pads , cleaned up and re-greased the guide pins (all good from last time mind - but used a little less 3m silicone grease), pushed the ATR pistons back in, cleaned up the pads (quick going over with a wire brush and brake clean), re-greased all the contact points with ceramic grease, and all put back together nice and free and perfect. DS2500 pads have plenty of life in them (5mm), tiny bit 'ragged' around the edges mind, but they are a few years old now and done a few track days.
4) Both front ATR discs inspected and measured, 27.9mm (28mm new), hardly even worn, not even a lip or rusty edge. All drilled holes inspected for cracks (none at all - good to know)
5) Bled through near enough 1.5litre of RBF600 (rather than sedately pumping it, each corner was done in the right order using 1way speedbleed nipples, 0 leakage at the threads, and performed as quickly as possible incase air was trickling back up the pipe), 0 air bubbles observed (but i was doing it by myself), fluid was clean as done earlier this year (same rbf600, always new bottles).
6) didn't touch the rears other than look at them, clean up with some spray/compressed air, and bleed. With enough left arm effort , if they are a little bit warm, you can actually lock the rears so they are working fine...

Went out for a drive (Loving the comfort of 16s on 50profile tyres!), and it seemed near perfect! Much less pedal travel, solid feel, much better initial bite from the front brake, and could sustain hard braking and no ABS due to the better tyres. Thought id cracked it - was very happy with myself!

Come Monday trip to work and back - seemed to be halfway back to 'soft'

Drive to work this morning, back to excessive pedal travel again. The braking effort is there, but its only when the pedal is near 2 inches down inches down, which doesn't leave much reserve for very hard braking as required on the track. Fine for the road, I've never been worried about it not stopping, just not stopping very hard which you need for the track day.

So I'm convinced now it must be a hydraulic issue:

A) Master Cylinder seals most likely? Anyone ever rebuilt it? ATR swap ive not read anyone doing that.
B) Trapped air not being removed by bleed method - rbf600 seems very thin, easier for air to get trapped? perhaps foot pumping isn't fast enough to shift air pockets - needs a pressure bleed maybe. Anyone had any luck with that? I understand the honda cap is not suitable for an airtight pressure seal, i see Sealey do a universal pressure cap for the pressure kit...
C) Issue in the front calipers. New seals / pistons went in not so long ago (and new pistons a few year previous). Perhaps I used red grease where I shouldn't have leading to some weird piston pull back issue?
D) I don't believe its wheel bearings, as pumping the pedal doesn't really make it any better.

Any thoughts appreciated!

Cheers

Scott
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Fixing the ATR setup front brake feel...

Post by Scott560 » Thu Dec 10, 2020 11:52 am

trying to track down a new master cylinder or rebuild kit seems like hard work.

Here is a picture of one removed by lankysod on ebay. This car is the same as mine I assume, car is a UK VTI 2.2 H22a8 manual
https://www.ebay.co.uk/itm/Honda-Prelud ... SwdAVfHBg6
Note 2 circuit exits, 1 pointing straight up at the end, and one pointing to the passenger side. shaft sticking out.

lings part picture is a bit puzzling - only shows 1 exit up, the other must be on the hidden side, eg pointing towards the outside of the car? Doesn't make much sense. Let just assume the images are 'flipped' from American market pictures, part 4 shows the shaft sticking out.
https://www.lingshondaparts.com/partsca ... f/B__2400/
Part 31 is the 2 litre version (hence not listed in the parts unless you go back through the journey as a 2litre). This has no protruding shaft coming out of the cylinder.

The only new part I can find is the Japan Parts PF445 , but again, the 2nd circuit exit is on the wrong side (sticking into the drivers side wing, not into the engine bay / passenger side).
https://www.ebay.co.uk/itm/Brake-Master ... SwhCBbYcMY

this makes me think the only new one you can buy is an aftermarket one, built for USDM (would make sense as the brake servo on the other side, hence outlet on the other side).

rebuild kits:

https://www.ebay.co.uk/itm/BRAKE-MASTER ... 4882183188
also available on buycarparts.co.uk

This was about all I could find, but diameter listed as 22mm , which is less than 15/16th , so almost certainly not right for an ABS 1inch (if we are still to assume 5th gen ABS is 1inch master cylinder).

ATR master cylinder idea:
https://www.ebay.co.uk/itm/honda-accord ... SwYaZfKKXp
https://www.ebay.co.uk/itm/Brake-Master ... SwY3Veov3C

Doesn't have the exits in the same place (both out the side) - and doesn't have protruding shaft , so not an easy swap (probably needs servo moving over as well, and hard brake lines modifying as well as anything else).

Sigh...

I think I will buy the one for sale from lankysod, and take it apart to measure because there isn't much I can see in part listings to confirm the diameter... Then take my luck on a cheap cylinder rebuild kit. If the seals don't fit, I'm only out under 30quid...

Thoughts appreciated.
'00 UKDM 2.2VTI H22a8
'21 'e' Advance

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