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Brake Bias - Any Easy Check Before Pinning?
Howlor - 25/4/06 at 07:40 AM

Hi,

SVA is now looming loud and clear so need to sort some of the smaller jobs. Is there any way to gauge where to set my brake bias without getting it onto the rollers?

I want to pin it prior to the SVA at Beverley but obviously need to know where to set it.

Thanks,
Steve

wheezy - 25/4/06 at 07:45 AM

All I have done with my car was jack it up and adjust the bias so that the front wheel locks up and you can just turn the rear wheel. I then gave it another turn towards the front and locked it up.
A quick road test should then confirm that it is ok.

Howlor - 25/4/06 at 07:46 AM

I thought about doing it that way as well. Many thanks.

wheezy - 25/4/06 at 07:59 AM

I'll know that the SVA inspector is happy when the car goes for its SVA next Wednesday
When is you car due for its test?

Howlor - 25/4/06 at 08:00 AM

Next Friday 5th May I hope. Still waiting for confirmation.

Steve

wheezy - 25/4/06 at 08:06 AM

Hope it goes well.

Dave

Howlor - 25/4/06 at 08:11 AM

Good luck. Where are you been done?

wheezy - 25/4/06 at 08:22 AM

Taunton.
Its a 40 mile drive to the test centre, but at least I will get some time behind the wheel.

Howlor - 25/4/06 at 08:28 AM

Mines about 20 miles so hopefully sunny day!

JAG - 25/4/06 at 08:31 AM

Howlor,

what brake spec' do you have front and rear?

and what m/cyl's are you using on each circuit?

The favourite way seems to be to test drive and set-up that way. The method involves performing several VERY HARD stops from as high a speed as you can achieve within the space you have. You should then adjust the bias to make sure that the fronts always lock first.

ALWAYS start with a very front biased set-up and then increase the bias to the rear brakes as you test. This way you will avoid locking the rears first and hopefully have a safe test.

The problem is this method is not foolproof. If you don't test at a high enough decel' then you may find that the rear brakes still lock first at the higher decels (that you didn't test at ).

And of course there's an intrinsic risk in performing the test!

Either way the SVA man will tell you if it's Ok or not.

GOOD LUCK.

Howlor - 25/4/06 at 09:04 AM

50 ft gravel drive into 15ft garage, blade engine should accelerate fairly well so assuming I have decent sized balls I may acheive 35-40 mph before entering the garage leaving me 15ft stopping distance. Should I put a helmet on?!

I think I will go for the jack up and test method and accept I may fail on this point.

Many thanks for your suggestions.
Steve

G.Man - 25/4/06 at 09:53 AM

Have a word with Marc, they have a great way of "pinning" the brakes so you can do it at the sva centre after the brakes have been signed off..

britishtrident - 25/4/06 at 10:59 AM

quote:
Originally posted by JAG
Howlor,

snip

The favourite way seems to be to test drive and set-up that way. The method involves performing several VERY HARD stops from as high a speed as you can achieve within the space you have. You should then adjust the bias to make sure that the fronts always lock first.
snip
GOOD LUCK.


A very good way to kill yourself -- punch the brake hard with too much rear bias and the car will spin out in less than the blink of an eye.



Testing starts from slow speed on good dry tarmac with bias set towards the front. Work towards the rear one turn at a time.

[Edited on 25/4/06 by britishtrident]

smart51 - 25/4/06 at 11:32 AM

quote:
Originally posted by britishtridentA very good way to kill yourself -- punch the brake hard with too much rear bias and the car will spin out in less than the blink of an eye.


He did say that you should start out with heavy front bias and slowly adjust to the rear.

RichieC - 25/4/06 at 11:42 AM

quote:
Originally posted by G.Man
Have a word with Marc, they have a great way of "pinning" the brakes so you can do it at the sva centre after the brakes have been signed off..


Ill be interested in the trick method of pinning too as Im not sure Ill be able to get it on the brake rollers beforehand.

britishtrident - 25/4/06 at 11:54 AM

quote:
Originally posted by smart51
quote:
Originally posted by britishtridentA very good way to kill yourself -- punch the brake hard with too much rear bias and the car will spin out in less than the blink of an eye.


He did say that you should start out with heavy front bias and slowly adjust to the rear.


He also said "hard stops from high speed" --- believe me do that on car with way too much rear balance and you will be in the hedge in an instant particularly in a car that naturally oversteers and has a low polar moment of inertia.

Years back I spent a lot of time setting-up load sensing balance valves by road test -- and this thing I know.

[Edited on 25/4/06 by britishtrident]

JAG - 25/4/06 at 12:40 PM

quote:

ALWAYS start with a very front biased set-up and then increase the bias to the rear brakes as you test. This way you will avoid locking the rears first and hopefully have a safe test.

and
quote:

of course there's an intrinsic risk in performing the test!


Britishtrident - practice your reading skills as hard as you practice your "speed posting" technique and you'll save us all a lot of irritation

[Edited on 25/4/06 by JAG]

Nosey - 25/4/06 at 12:50 PM

I've been setting up brake bias on rally cars for years with the "hammer down road and stand on the brakes" method.

Just involves a bit of common sense. Don't go mad, 1st gear always worked for me and thats with 235 section slicks (and I've crashed enough in rallies to know that it's not my God-given genius for driving that stops me putting it in the hedge while doing this......).

MikeR - 25/4/06 at 04:58 PM

Edited this post as it didn't make sense.

Was supposed to be making a joke that the reason you occasionally put the car in the hedge is not cause of a problem with your driving skill or ability to set up a car, its cause some idiot keeps putting bends in the road.



[Edited on 25/4/06 by MikeR]

G.Man - 25/4/06 at 08:38 PM

quote:
Originally posted by RichieC
quote:
Originally posted by G.Man
Have a word with Marc, they have a great way of "pinning" the brakes so you can do it at the sva centre after the brakes have been signed off..


Ill be interested in the trick method of pinning too as Im not sure Ill be able to get it on the brake rollers beforehand.


Ring Marc, it wont be posted...