15 replies to this topic

[The.Yellow.Mini.Guy]

Good morning mini people!

 

I recently got 4 pots for my mini and before fitting them I would like to sort out an issue I have.

 

When I'm hard on the brakes the rears lock up way before the fronts do which wears them down alot quicker and makes the handbrake useless without constant adjustment. I get the feeling the brake bias valve has gone and rather than just replacing it I thought about getting a manual one like the Wilwood one so I can fine tune the front/rear balance, I'm far from an expert so any advice would be great (tell me if this is the wrong way to go about it!).

 

I have the black tag master cylinder which has two feeds going to the brake balancer then to the brakes, If i just connected the front brake lines together bypassing the valve and used the Willwood brake valve to connnect the rear lines would that be what I'm after? I also heard the yellow tag master cylinder is better but mine works just fine so it would be a shame to replace something thats works?

 

 

Now.. the next item on the agenda.

 

I have the standard MG metro engine in and I'm looking to add a few extra horses to the old british stable! Not anything crazy but I'm thinking a new head and rockers, From what I've read it seems the a-series 'breathing' is something that can be improved. I don't want to take the engine out and from what I've read the metro cam isn't actually to bad. This is where I'm stumped, I have a working knowledge of the suspension and brake setup as I have messed with it quite alot recently but engines are something I have never really done anything with. I'm keen to learn and would like to do the work myself, obviously polishing and porting a head isn't a 'diy job' so some advice would be great. I've ordered David Vizzards A-series tuning book for some more knowledge so hopefully that will help. I've also thought of full electronic ignition by Aldon amethyst or maybe even taking the leap to megajolt but I get the feeling that might be overkill!

 

 

Any help is appreciated! 

 

my setup is just standard metro engine with the accuspark electronic ignition module.

[Steve220]

What condition are your tires in? Are they cheap or a decent brand?

If it turns out they are ok and it is, say, your brake bias, Then I wouldn't get an adjustable if you are in fact a novice to it all. To fine adjust it you need specialist equipment to differentiate the percentage difference between front and rear balance to your requirements.

Edited by Steve220, 24 October 2015 - 10:32 AM.

[carbon]

+1 for Steve's comments. If this is for a road car then adjustable brake bias is not really suitable.

 

Rear brakes locking up before front brakes under heavy braking make any car very unstable.

 

Worst case scenario is you're tanking along motorway in heavy traffic in wet conditions and suddenly need to brake - you can end up spinning the car and/or completely losing control.

[nicklouse]

Sounds like you do need to service/change the bias/regulator.

Which is also a shut off valve if one of the two brake circuits fails.

[nicklouse]

Re the second part of your post.

If the ignition works leave it.
Exhaust.inlet.filters and having the carb set up after as the first steps for getting a little more out of the motor.

[The.Yellow.Mini.Guy]

What condition are your tires in? Are they cheap or a decent brand?

If it turns out they are ok and it is, say, your brake bias, Then I wouldn't get an adjustable if you are in fact a novice to it all. To fine adjust it you need specialist equipment to differentiate the percentage difference between front and rear balance to your requirements.

 

Thanks for the feedback :)

 

Pretty good condition all the way round and even wear, I've never bothered with cheap tyres. I ride bikes so I see the importance of good rubber! They have yoko a539's

 

I wouldn't say I'm a complete novice I've done a fair bit of brake work mostly with motorbikes, Its more the mini's braking system I'm not 100% familiar with.

 

Could you not do it on a private stretch of road and by feel? or is that just stupid and unscientific? 

[The.Yellow.Mini.Guy]

+1 for Steve's comments. If this is for a road car then adjustable brake bias is not really suitable.

 

Rear brakes locking up before front brakes under heavy braking make any car very unstable.

 

Worst case scenario is you're tanking along motorway in heavy traffic in wet conditions and suddenly need to brake - you can end up spinning the car and/or completely losing control.

 

I get what your saying, I changed the rear shoes and drums and went a small drive to check the brakes and it nearly did.. Which is why they aren't currently adjusted that tightly.

 

Thanks for the response 

Edited by The.Yellow.Mini.Guy, 24 October 2015 - 12:42 PM.

[The.Yellow.Mini.Guy]

Sounds like you do need to service/change the bias/regulator.

Which is also a shut off valve if one of the two brake circuits fails.

 

Thanks for the response  

 

Is servicing it an at home job or does it have to be sent away?

 

Never thought of that actually, So even though its separate lines if one goes they both go?

[The.Yellow.Mini.Guy]

Re the second part of your post.

If the ignition works leave it.
Exhaust.inlet.filters and having the carb set up after as the first steps for getting a little more out of the motor.

 

Completely forgot to mention it has a stage one kit and Hiff44 with K'n filter 

[Alex_B]

I would just replace like for like, fitting an adjustable bias is fine on a motorsport vehicle (excluding regs) but I don't believe it is legal for a road car to have one fitted. 

Also setting it up by feel requires an experienced driver and the risks are high if you get it wrong. 

The mini as standard doesn't do a lot from the back end, I believe 20% of the braking force so something is amiss if its braking from the back first. Check the basics like if the wheel cylinders have been changed for a different bore, and the reducer valve (can't usually check those its a replacement job) 

[Spider]

Have you got the right sized wheel cylinders on the rear brakes?  Given your set up. 5/8" would be an appropriate size. I'd look here before looking to replace the bias valve.

 

And are the drums round? If they have even a small amount of out of round in them, they lock fairly easy.

[Icey]

Have you got the right sized wheel cylinders on the rear brakes?  Given your set up. 5/8" would be an appropriate size. I'd look here before looking to replace the bias valve.

 

Very much this. On most Minis (other than those fitted with the bias valves from the factory) the break balance is controlled by the sizing of the wheel cylinders, if those are wrong (usually found after the fronts have been altered) you'll have issues.

 

I've just had the same thing myself, we have Metro 4-pots and originally had 3/4" rear cylinders - that was lively! Changed down to 1/2" and everything is back under control.

[johnR]

it is very easy to mount the bulkhead bias valve the wrong way round (as I found out!) which results in the symptoms you give.

Any chance of that having happened?

John

[The.Yellow.Mini.Guy]

By some miracle I was helping a mate today who has a few mini bits and bobs and on his shelf was a very new looking brake limiter valve, He said I could have it! So I'll pop it in when I change the calipers and see what happens.

 

Thanks for the help again lads!

Edited by The.Yellow.Mini.Guy, 26 October 2015 - 09:38 PM.

[nicklouse]

Make sure it is the correct one. There are more than one.