Att: Owner of AE86 with big brake

[Tom86]

Hi everyone,

Got a quick question for AE86 owner with big brake upgrade. I've recently installed a Hopper Stopper Kit 285mm twin piston ford AU2 caliper + 1 inch master on my car. Will put a pic up later for those who are interested.

The brake is quite powerful and I'm able to lock the wheels at pretty much any speed and it hardly get hot. Only problem I have is I need to press the brake pedal quite hard to get to work. I think the problem maybe with the stock booster not giving enough assistant?? e.g in newer car you can just touch the brake pedal and the brake will grap, but with my car its not doing that.

I just want to hear how bigger brake on other people cars perform? does you brake require hard braking before it start to work?

Thanks

[oldcorollas]

is the one way valve still fitted? is it fitted in the correct direction?

[MWP]

The brake is quite powerful and I'm able to lock the wheels at pretty much any speed....

Stock brakes on every car should do this.
The main reason to upgrade brakes to stop overheating, not to increase braking force.

So is the pedal squishy?
Or is the problem you need to push very hard on the pedal to get it to stop?

[Tom86]

The brake is not squishy it been bleed properly. The booster appear to be working properly did the test as per the Toyota manual.

The problem is it doesn't have the bite. For example in my Mum's Holden Vectra I only need to slightly touch the brake and it will work, in my car i need to press considerably harder to get it to bite. Hence my reason for suspecting that the booster maybe too small.

[sam86]

Can you please post some pictures and what would be the smallest size rim that would fit over your brakes.

[EVOSTi]

most modern cars (especially new toyotas) have heavily assisted brakes. this may feel like they are working better because you dont need as much effort to push the pedal, but it aint necesarily so.

if your brakes are working fine id leave it. if it takes a bit of effort to push the brakes thats ok, you should have better feel, which is good

[Cuzzo]

Id Say its the smaller booster to go along with the 1" master cylinder.
Now to fix this id suggested a larger boost or smaller master cylinder for "feel" but for the effectiveness of the braking the smaller master cylinder might not be beneficial.

[lexsmaz]

As you said i would put the extra pedal effort down to the master cylinder increase without the booster size increase ... Runing a bigger bore master cylinder the pedal effort must be increasd to get the same fluid pressure output that you had out of the smaller bore m/cyl, The reason for the bigger bore upgrade is due to the extra fluid displacment of the bigger front callipers ... Probably there are a few options, you could try runing some softer front pads may help but also may fade, defeating the original upgrade ... run a bigger booster if you can get one? or refit the original master cylinder & see how that coppes, down side is alonger pedal travel & maybe too long travel to be safe, or fit a master cylinder with the bore size in between the 1'' & the original m/cyl bore size ...
Or just get used to your new brake setup or buy a vectra, Personally its all a compromise because its not oem replacement, but that said you should be able to get it pretty good ...

[driftae86]

most of the time when people do big brake upgrades on ae86s (and other cars aswell) the booster is changed to match it. i hear people use r31 boosters, but i think you can use anything that fits. a mate of mine (you might know him, jeremy up in the hills) uses one from a pajero or some shit

so yer i would put your problem down to the relatively undersized booster.

but might be an idea to wait for some people who have first hand experience to reply to this thread to get some definite answers. If you know Gabe, ask him. Or the new owner of his car Brendan. good luck.

[Tom86]

Can you please post some pictures and what would be the smallest size rim that would fit over your brakes.

There is hardly any room under 15 so yeah 15 minimum. There no way it would fit under 14s.

most modern cars (especially new toyotas) have heavily assisted brakes. this may feel like they are working better because you dont need as much effort to push the pedal, but it aint necesarily so.

if your brakes are working fine id leave it. if it takes a bit of effort to push the brakes thats ok, you should have better feel, which is good

You definately have more feel thats for sure, its good when you go for a spirited drive. Little annoying when stuck behind traffic .

Kinda have to re-learn how to use the brake as I've been locking up leaving two lines of rubber everywhere.

So anyone actually run a 1"master with stock booster?

[fixeruperer]

i never had a problem upgrading my m/c ( 15/16 i think its off a landcruiser), and keeping standard booster.
does your booster hold vacuum ?.

[30psi 4agte]

Id Say its the smaller booster to go along with the 1" master cylinder.
Now to fix this id suggested a larger boost or smaller master cylinder for "feel" but for the effectiveness of the braking the smaller master cylinder might not be beneficial.

cuzzo is on the money.

I feel your master may be too big a bore size.

The smaller the master bore the more line pressure that is generated and hence applied to the brake pistons. The down side to this is increased pedal travel as the master needs to travel further to displace the same amount of fluid.

Bigger Master = less pedal travel but requires more ( foot ) pressure on the brake pedal to achieve the same force at the caliper.

So you may find even if you switch to a larger booster you may still have the same prob.

ALOT of people think you want a BIG master bore but that isnt the case.
In theory you would want the smallest master possible as you can generate the greatest amount of line pressure with the least amount of pedal force but this comes at a price.......... which is pedal travel and a "spongy" feel to the brakes

It is a toss up between pedal travel and applied pressure.

[EVOSTi]

i got 15/16 with the standard booster aswell, works good.

what rear brakes are you using? might need an aftermarket proportioning valve?

[thechuckster]

without changing the proportioning valve you will need more braking effort - you've doubled the front piston size without changing the amount of fluid going to the rears.

I'd hazard a guess that the rears are locking up first?

[Tom86]

I'm using T-Series rear disc from Jap Sprinter. No, I don't have issue with the rear locking up first. The front lock first every time, almost too easy sometime.

I thought about trying a smaller master, but I've already spend the money on this brand new super dooper 1" twin master cylinder .

I was looking at the old booster/master I got from AE92 halfcut its 15/16 I wonder if that will fit?