26 replies to this topic

[Kam]

What size wheels have you got or are getting? You do know this right? Got a bit worried with the 11" stuff...

Assuming its a 12" wheel then with that engine on the road you'll be fine with running standard 2 pot calipers and standard 8.4" solid discs with some good uprated pads, but if your gonna drive it "spiritedly" everywhere or end up upping the power a bit further down the line then you might find them not being enough, all down to how and where your gonna use it

Getting 4 pots is never a bad thing, I'm using 12" wheels wrapped in yokos and still on mini suspension with minispares 4 pots and solid 8.4" discs with uprated pads and braided hoses and drums on the back, ran this on my 1.6 honda (which weighs probably just a little more than your vauxhall) and now on my 2.0 honda (which definitely weighs more than yours) still with the same setup above which includes 12" steel wheels (which trap heat more than alloys) and have never had any issues whatsoever on track or road with passengers or not, as Skortchio mentioned above you can lock most mini setups up

Thats the bare min I would have for spirited driving on the road, anything else added is just peace of mind, which again is never a bad thing...

[DylanAWRoberts]

What size wheels have you got or are getting? You do know this right? Got a bit worried with the 11" stuff...

Assuming its a 12" wheel then with that engine on the road you'll be fine with running standard 2 pot calipers and standard 8.4" solid discs with some good uprated pads, but if your gonna drive it "spiritedly" everywhere or end up upping the power a bit further down the line then you might find them not being enough, all down to how and where your gonna use it

Getting 4 pots is never a bad thing, I'm using 12" wheels wrapped in yokos and still on mini suspension with minispares 4 pots and solid 8.4" discs with uprated pads and braided hoses and drums on the back, ran this on my 1.6 honda (which weighs probably just a little more than your vauxhall) and now on my 2.0 honda (which definitely weighs more than yours) still with the same setup above which includes 12" steel wheels (which trap heat more than alloys) and have never had any issues whatsoever on track or road with passengers or not, as Skortchio mentioned above you can lock most mini setups up

Thats the bare min I would have for spirited driving on the road, anything else added is just peace of mind, which again is never a bad thing...

Thanks for that I'll go with 4 pot breaks then I guess just to be safe! :) there definitely will be spirited driving....

[The Matt]

Kam's Mini even brakes ok with me in it and that's heeeeeeeeeeeavy!

[AGoaty]

Are you using a servo?

If you don't have one then fitting one may be the best option. You can get a remote servo which doesn't have to fit in the engine bay as I know with conversions, space is tight. Then use the 8.4 standard discs or Metro 4 pots if you can afford them.

[tiger99]

Oh, and you want BRAKES, not BREAKS. If something BREAKS you will have big problems.

Edited by tiger99, 08 December 2012 - 11:22 AM.

[The Matt]

I wouldn't bother with a servo. I don't have one fitted and find it fine.

[Skortchio]

A servo has no bearing on the braking power, only the required pressure to gain said braking. So as The Matt says, it's of little advantage.

[AGoaty]

Funny then, all modern cars have servo's?

I have a Mini with a servo and standard 8.4" disc brakes, which has better brakes than my none servo'd Mini with 9.5" disc brakes from a Rover Metro. Neither have poor brakes but the servo'd one has much less effort to stop the car.

At the end of the day, it's opinion, but a servo makes the driver use less effort to stop the car.

[The Matt]

Yeah you're right, totally down to personal opinion. In the conversion he's doing it's fairly easy to mount one over on the left and use a linkage off the pedal box. I just personally don't think a Mini needs a servo.

[Skortchio]

At the end of the day, it's opinion, but a servo makes the driver use less effort to stop the car.

That :)

Doesn't improve braking, alters the effort for a required amount of braking.

[tiger99]

Provided that the driver can lock the wheels with a pedal effort that is reasonably comfortable, a servo is optional and basically down to personal preference. If the driver can't get maximum braking effort, i.e. at the point of locking on a dry road, without abnormal effort, you really do need a servo, which is one of the reasons why many modern cars must have one.

The issue is basically down to the area of the caliper pistons and the amount of pad knockback due to sloppy bearings, as the designer (you, if you are modifying!) has to be able to ensure that, even with one of the two hydraulic circuits failed, there is always enough fluid displacement to go from the pads fully knocked back to applied hard in one stroke of the pedal. (If you can't satisfy that condition, the car is unsafe.) You can't change the pedal strike by very much due to limitations of the human anatomy, so you need a larger diameter master cylinder to get more fluid displacement, which lowers the hydraulic "leverage" and needs more pedal pressure. Changing from drums to discs is one thing that seriously increases the amount of fluid displacement needed, which is why the master cylinder changes on a Mini. Many modern cars have discs at the rear too, yet more fluid displacement. Modern sliding calipers have the same fluid displacement needs as older double-sided hydraulic calipers, it is just that twice the movement is needed on one side.

There is quite a lot involved in modifying brakes properly, and it does concern me somewhat that it is not always done correctly. If in doubt, fit a larger diameter master cylinder, and then if the pedal is too heavy, fit a servo. That errs on the side of safety.

Some older cars, notably Triumph Heralds and MK 2 Cortinas, had very good (for that time) front discs, no servo, and comparatively light pedal pressure. There were three reasons for that, firstly hubs that were adjusted at every service, so they ran with very little free play, so pad knockback was minimised, secondly, they were only single circuit brakes so did not need to meet the criterion of working within one pedal stroke with the other circuit failed, and thirdly, at least in the case of the Cortina, the rear brakes were self-adjusting so always ran with minimum clearance. I do not suggest that we return to the bad old days of single circuit hydraulics, but adjustable taper roller hub bearings on a Mini would be rather nice, if someone could design them. Quite an interesting problem on a FWD car, but I think there is a way of doing it by using an adjustable seat benind one of the outer races, as the hub flange obviously must remain very tight on the splines at all times. Certainly at least new hubs would be needed, but the opportunity could be taken to fit modern, current production bearings of larger size, obtainable from a reputable source, not China.

[kcchan]

I'm surprised no one has mentioned suitable pads yet.