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MG Midget and Sprite Technical - Long First Push - Brake Pedal

Over the years I've always suffered with a long first push of the brake pedal on my 1500, second and subsequent pushes are fine.

I've changed the brake master cylinder, just added Goodridge braided brake hoses, new calipers, shoes, brake cylinders, rear adjusters, the only thing I haven't changed are the drums, re-bled several times with an Eazi Bleed, which should have got rid of all old fluid, anyone had similar issues?

Thanks Tim
Tim Lynam

Tim,
you may be running with your rear brake shoes adjusted with too much clearance. I usually have mine set so that there is a slight drag felt when rotating the wheel by the tyre edge. Plus stamp on the brake pedal a couple of times before final adjustment. Drag may seem wrong, but they very quickly settle to a close clearance which reduces the pedal movement needed.

I note the thing not listed in your replacements, is a check for ovality in the brake pedal pivot. That would increase first stroke pedal movement.
GuyW

Poo.
Guy got there before me and said exactly what I was thinking.
Greybeard

Thanks for the comments, I usually tighten the adjusters until the drum stops turning and then back off the adjuster until it will turn with some resistance but I could be loosening a bit too much.

I have never checked the brake pedal pivot and wouldn't have thought about checking so will check it out.

Tim Lynam

Tim

When you say Ďfirst pushí, is it the very first push when starting your journey, and itís ok for the rest of that journey?

If you were to travel for 10 miles or so on the motorway without using the brakes, would the pedal be ok the next time you press it, or would it be long again?
Dave O'Neill 2

Good point Dave, first push and then immediate pushes are fine, but leave the pedal alone for a minute or two and the same longer first push, maybe itís just the shoes and pads retracting and each first push taking longer to push pads and shoes fully out?
Tim Lynam

Do you have any play in your front wheel bearings? If there is, it's possible for the discs to push the pads back into the calipers.

Also, are you using mineral or silicon fluid?
Dave O'Neill 2

Not noticed any play in the front bearings but Iíve only replaced the back bearings, so will be worth checking.

Iím using a mineral brake fluid.
Tim Lynam

Tim,
how much new brake fluid did you put in?
Nigel Atkins

If not FWBs, then how about warped discs, or run out on the disc if they have been replaced without adequate cleaning of the hub flange.

Any pulsing of the brake pedal under very light braking?
GuyW

Nigel,
I added around 200 - 250 ml of brake fluid, I lost a reasonable amount after changing one of the brake cylinders, over the last couple of years itís been bled reasonably frequently after different jobs on the system, so there should be no old fluid in the system.

Guy,
The discs are old and have not been changed in the last 7 years but I donít suffer from any problems with the brakes pulsing, they have always got through MOTís ok but itís just that first annoying longer pedal travel thatís so annoying!
Tim Lynam

Tim,
old fluid is anything over 18-24 months old but depending on circumstances this could be a shorter or longer period.

If all that came out of each nipple was clear/clean and without any air bubbles that's job done as far as renewing.

How long is this long push?
Nigel Atkins

If you apply the handbrake, just enough to stop you from pushing the car, then drive the car to try the long first pedal again, if it no longer does it then you must have wear associated with the handbrake.
You could try that.
Robert
MG Moneypit

Tim, the reason I asked about pulsing pedal is the same issue that Dave was alluding to with FWBs. If the disc isn't running true then after a few minutes running time the disc will push the front brake pads back a little into the caliper bores. Then the next time you brake this clearance has to be taken up again, hence a long pedal travel. Warped discs will do the same, and can sometimes be felt as a slight pedal vibration under very light braking.
GuyW

What's happened to the BBS display?! I cannot get my usual selection of preferred topics and selecting "last posts" just brings up a long Disclaimer message so I cannot see what else is being discussed. Only posted here as I cannot find any other thread at present . I hope this is just a temporary glitch!
GuyW

Guy
My mobiles IOS and Android have both changed to a display I don't like - cant see a way of getting back to the old style horizontal lists.

Think you are supposed to post under 'Beta Testing'

R.
richard b

I may have strayed onto a beta testing display, it looks very different and so far this is the only thread I can locate, which is a bit odd!

Sorry for thread drift/ hijack, Tim. I am a bit lost at the moment and this is the only home I can find!
GuyW

Guy,
The Beta testing is over its now live !
richard b

Guy, Richard,
give it a bit of time for things to settle.

Rich,
Mike has replied to me in a Beta Testing section thread that choice of font and colour will return to Customise.

I had to look up iOS, now I know it's all to do with Pear(shaped) and Android is to do with Gaga, but I won't remember remember.
Nigel Atkins

Now looking at this on my laptop and it looks a bit more familiar and friendly.
Previously I was using my phone (Android) and could only see the current thread. Maybe due to phone settings or cookies or something like that. I did notice it was allowing me to post replies again which it wouldn't doing before without using the "Gary method"
GuyW

Nigel, the long push is probably only an extra couple of inches, but annoying and highlights thereís an issue somewhere.

Thanks for the other suggestions, Iíd never have thought about the front wheel bearings being responsible and itís about time the discs were changed, so some good pointers to investigate.
Tim Lynam

Tim, if you have a dial gauge, or fancy buying one - they can be quite cheap, - it is easy to check front discs for run out before deciding to replace them or the bearings.
GuyW

Tim

What happens after a good emergency stop in terms of brake pedal travel for the stop and immediately afterwards, as well as does the car pull up straight or to one side in such a stop? (Safely done with no one following you on an open stretch of clear wide straight road. Plus all tyres in good condition and correct pressures). I am wondering about a single sticky piston.

This thread is definately a cut out and keep for my future fault finding as there are some possible faults that I have never thought of.

Cheers
Mike

M Wood

Could also be multiple brake faults all contributing a little to this. My current brake rebuild and fixing spree uncovered a selection of problems from PO - incorrect size master and rear rear pistons, leaky rear axle oil seal causing wet brake shoes, crushed rear brake pipe in axle, corroded bleed nipples plus my inability to install the beehive rear brake retaining springs.

I would do a full brake fluid change and bleed, making sure you bleed in the correct order.

Weird idea - anyone had issues with the brake light warning switch that might be the culprit or co-defendant?

Thanks
Mike
M Wood

Tim,
if it feels like a couple of inches on the pedal that sounds like a lot to me.

IF, it turns out to be anything to do with the change of fwbs then I have experience of that and why it might be a problem, some of the popular information I found about their installation was basically wrong - but of course you only need to cross that bridge if you come to it.
Nigel Atkins

Guy, no I don't have a gauge to check disks, but good idea if there's any reasonably priced ones about.

Mike, its not a sticky piston as calipers changed not too long ago and the car stops sharply and does not veer to the left or right, fluid is nice and fresh as they have been bled and bled over the past year or two, no leaking cylinders and they have both been changed, all flexible hoses just changed, so everything to me points to the fwbs or discs as just about everything else has been changed.

Nigel, yes the travel is not good, it may only be an inch but enough to be frustrating, I will get to the bottom of it one day!
Tim Lynam

Tim, you could try and check for wear in the fwbs. Or at least wear that might affect the brakes. Jack the front wheels clear of the ground. Spin the wheel round a few times by hand, then put your forefinger so that it rests across the gap between disc and caliper, touching both. Then with the other hand, rock the edge of the wheel side to side. If there's wear you will feel it as movement between the two components as changing pressure on your finger.

This method isolates the wear separately from possible king pin wear, which wouldn't have an impact on brakes travel.
GuyW

In a similar way to what Guy notes you can get a good idea if the disc is warped, either a screwdriver or a finger nail! held against the disc or slightly off it and restrained on the caliper and turn the disc slowly by hand - will give a good idea if any runout.
If its warped / out to any degree it will show up fairly easily or buy a DTI but for a once off its probably another one of those tools that are nice to own !

R.
richard b

Tim

A few more random ideas:

All your new connections tight and sitting correctly in fittings? Air in the system, very minor leak?

Unfortunately there could also be suspect quality new parts.

Cheers
Mike



M Wood

It's also possible that you've still got some trapped air in there.

Although I've been using an Eezibleed for years, I do occasionally have to resort to manual bleeding in order to get a good pedal.
Dave O'Neill 2

Air in the system could be the problem but this would normally also give a spongy feel to the pedal, which I didn't think was part of Tim's symptoms. If it's just long travel, but on a second stroke it then firms up and feels hard without springyness then I doubt it is air in the pipes.
GuyW

I very much doubt there is any air left in the system, there has been many bleeding sessions over the past couple of years after changing different parts of the braking system and there are no leaks on the system and the master cylinder is always full and never have to top up except after bleeding. I have just checked the extra travel on the first push and itís only 2cm but it feels much more.

You only have to leave the pedal alone for a few seconds and the long pedal on the first push returns.

I will check the play in the fwbís at the weekend.

Tim
Tim Lynam

<<
You only have to leave the pedal alone for a few seconds and the long pedal on the first push returns>>

Tim, for clarification, does this happen when you are stationary or only when moving?
GuyW

Guy, both when stationary and moving.
Tim Lynam

In that case, I still think thereís some air in there.
Dave O'Neill 2

Yes, if it happens when stationary it won't be the run-out on the disc / fwb issue.

Is the pedal reaching the floor on its first stroke, before requiring the second pump?
GuyW

Guy, good point, the pedal is a long way off the floor at first push so not a major issue, but just a frustrating one that I have never been able to resolve, there could be some air somewhere but I would be surprised knowing how many times I had bled the system.

But I appreciate all the comments as you don't always see the obvious for yourself!
Tim Lynam

It sounds perfectly normal to me - the shoes and pads WILL retract from the drums / discs because they are designed to do that.

Travel of one or two cm on the clutch pedal is nothing to worry about - I would be more worried about it having NO free movement on first push because your brakes would wear out in short order.
Chris at Octarine Services

Do you by any change have Copper brake pipes?
Rob
MG Moneypit

Tim,
how about try adjusting rear brakes with handbrake completely disconnected.

As you have an early 1500 it'll have the same handbrake mechanism as my 1275, do you grease it at services, I can never get any (additional) grease into the swivel/balancing lever yet if I take the nipple out grease shows below it.

You've kept the drums (often a very good idea) what do they look like on the inside?

What about the master cylinder pushrod and clevis pin could they have an unusual wear pattern (I was very surprised about the state of those on my clutch m/c)?
Nigel Atkins

Tim, so long as the first press on the pedal firms up before reaching the floor, and a second press is only about 2cms shorter, I would think that is ok. I wouldn't worry about that.

With only 2cms difference I would guess this is caused by piston travel at the front calipers. First press moves the pistons fully forward. When you release the pedal pressure the pistons do normally get pulled back a little by the rubber piston seals. But if you do a double stroke press the pistons won't have had time to retract like this so the second pedal stroke is that bit shorter.

So long as you are getting full braking on the first stroke before the pedal reached the floor, plus the pedal is then firm and braking balanced correctly, then I think that is probably just as it should be.
GuyW

2 cm or 3/4" of travel on first push - I think your brakes sound pretty good to me !

Thats not what I deem a Long Pedal !

R.
richard b

Tim said it's 2cm extra travel on the first push.

I wouldn't say that was normal.
Dave O'Neill 2

Rob - I'm intrigued by your copper brake line question, I cant think how that would have any relevance to this issue ?
Chris Madge

Chris, the reason I ask is our Frogeye has copper pipes and after renewing everything I have the same thing but not as severe (this was done 8 years ago BTW). I need to have the rear brakes adjusted up very tight to minimise the effect. I'm wondering if as copper is very much softer than original steel pipes there is an element of expansion under pressure.
Also, many countries ban the use of copper because it has a habit of work hardening, becoming brittle if not secured sufficiently. Cupro nickel (CuNiFer) is the minimum a lot of countries specify.
Rob
MG Moneypit

I am not sure that this is any more than the effect of a double pump of the brake pedal. The first stroke takes up movement in the pistons, and therefor the second stroke hits full on that bit higher up the pedal travel. 2cms difference in the travel is probably about right, especially if the rear brakes are adjusted slightly loosely.
GuyW

Tim,
it never hurts to check the brakes, as part of a service at least, but 3/4" is a lot less than up to 2" so might be OK. Taking the slack out of the rears may can give a better pedal feel - but a thought I've just had - the pedal return spring how firm is that, perhaps if you replaced it the push gap might feel better.
Nigel Atkins

Rob I would have though the difference between copper and steel would be very small ? But maybe its a factor.

The rubber hoses however must have a significant amount of flex?



Chris Madge

Tim,

If you've changed the master cylinder maybe the fluid port is in a different position and you need to extend the pushrod to close the port earlier and reduce that bit of free movement. I'm not familiar with the 1500 but it can be an issue on earlier cars.
David Billington

This thread was discussed between 23/02/2020 and 02/03/2020

MG Midget and Sprite Technical index

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