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MG MGB Technical - Brake Upgrades

Front Only Brake Upgrades Increases Stopping Distance!

Double Dutch or not?

Paul
Paul Wiley

What do you mean?
MMD

May be it decreases stopping distance or it will not be an upgrade.
Jean Guy Catford

Maybe it means that if you wind the fronts up too much, you'll lock them before there's any braking effort on the rear, thus leading to a lower overall rate of decelleration.

You'd have to go quite far with the upgrade though, as most of the common ones don't increase the braking force for a given brake line pressure much; instead they just give you more resistance to fade.

I guess if you put 330mm wilwood disks and massive 6-pot calipers on, you'd have to think about upping the ante on the rear brakes too!

ttfn,
--
Olly
Oliver Stephenson

Wondered if anyone would question that comment.
For a very good discussion of brake upgrades check out the February 2004 issue of Grassroots Motorsports; plus it has a story of a Volvo/MGB transplant with quite a nose job.
Leland Bradley

Leland,

Can you access that free, if not can you paraphrase.

Oliver is spot on but how far is too far?

Paul
Paul Wiley

Keep going; maybe I'll catch on.
MMD

A few numbers ball park

OE brakes 60% Front 40% Rear
Upgrade front now 70% Front 30% rear

Maximum front tyre grip at point just before lock up 1500lbs

So OE Front 1500 rear 1000 total 2500lb of stopping force

Upgrade Front 1500 Rear 650 total 2150
Nearly 15% reduction in stopping force!


Paul
Paul Wiley

Paul,
Here is a link to their article on brake material, not the brake upgrade and balance. http://www.grmotorsports.com/brakes.html

One of the interesting points in the upgrade article was that brakes are biased to the front from the factory. Front biased braking is stable; rear baised is unstable. So right from the start the rear brakes are not doing as much as they could in stopping the car and with a front brake upgrade the problem becomes worse, as you pointed out in your example.
Leland Bradley

PW,

In other words, the OE brakes were able to lock the front wheels so upgrading was a waste of time in terms of braking force!

Solution - get stickier front tyres that can use the extra braking force of the upgraded brakes....
Chris at Octarine Services

Or, only upgrade your fade resistance and not the brake force? e.g. space out the standard calipers, use standard size greenstuff pads and shove vented disks in there. If you require extra overall braking force, simply upgrade your right leg :o)

Gice to know I got it right, 'twas merely idle speculation <g>

good thread, this.
--
Olly
Oliver Stephenson

Chris,

Apart from going to race tyres (perhaps Yoko for road?) - Whats you view on just wider say 175 to 195?

Oliver

Peugot discs and princess calpiers are a good match or more expensive Wilwood.

Theres a limit to right leg once lock up on front occurs, I've bounced a few other ideas around on MGF Technical

Leland

Thanks for link I'll have a read.

Agreed the rear is underbraked in first place so you don't start from maximum but need to avoid rear lock up. The GT and roadster used diff rear cylinders of course.

Paul
Paul Wiley

How about this!
Upgrade front brakes = more controlled faster heavy braking causing more weight transfer relieving the load at the rear hence rear upgrade not necessary.
Just a theory.
My brain hurts!

Mark

PS I upgraded fronts only to 300mm vented discs with superlite 4 pot calipers and the rears would still lock up too early.
Now gone to twin master cylinders so I can get the bias just right. Presumably this will be a different setting for wet conditions than dry.
Mark

Yes, normally you can run more rear braking in the wet as the front tires remove some of the water.

Not much weight transfer with MGBs.
Leland Bradley

PW,

Yes, Yokos or Avon ZV1 - wider won't give much improvement as the grip on the contact patch depend more on the material than the size.

Chris at Octarine Services

Chris,

Do you know reason why with Wider Tyres the RV8 used smaller drums at rear or did they increase piston size?

The point about material is interesting as when the B was designed has there not been an improvement in material?

Leland good point.

I would add in wet less grip as well and less weight transfer.

Mark were you testing in wet?

Paul
Paul Wiley

I agree with Mark. Even with a OEM brake setup the rears will lock. I am using 195 Avon ZV1. I really don't see that you need more braking effort on the rear. Not for my car anyway.

I thought brake upgrades gave better control and modulation as well as reduced fade.

Joe
Joseph Phillips

This thread was discussed between 19/01/2004 and 21/01/2004

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.