Brake Pedal Effort - Collective brain help please (1 Viewer)

[AussieHJCruza]

Good Afternoon everyone, hoping for some input from the brains trust please:

02/86 FJ62 Sahara, going through the laborious process of getting a modified vehicle signed off by a vehicle engineer and registered.

I'm having issues with the brake pedal effort required, she passes the brake test with 35s, however max allowed pedal effort is 850 newtons and I'm at 961N to pass the test.

Drums are recently machined and new rear shoes, and front has fairly recent pads, just run of the mill aftermarket stuff. Caliper pistons aren't siezed. Handbrake passes the handbrake test so I'll assume that the drums are adjusted properly.

Soft lines are rubber but all look decent.

Brake booster is week-old Advics 80 series dual diaphragm into stock 60 series master.

I'm looking for suggestions on what I can do to reduce the pedal effort, a few thoughts below but would be interested in everyone's experience please.

Options:
1) More aggressive front pads
2) Braided lines - no idea if this will make any difference
3) I can get a further brake booster upgrade, however I'm reluctant as these are larger in diameter again than an 80 Dual Diapragm and because she's a Sahara, will foul on the clutch booster. Would like to avoid replumbing the clutch hardlines and relocating the master if there's any way I can avoid it.

Any thoughts on tyre pressures effecting this? Currently at about 30 psi for ride comfort.

Thanks in advance for your input and a couple of pics, just because.

Cheers

 

[AussieHJCruza]

If I'm correct, smaller diameter master increases travel but reduces pedal force? So I therefore I need to decrease size of M/C or increase the surface area of the calipers/wheel cylinders?

 

[g-man]

1. install a Hydro boost brake system...but it puts you in the same situation with the clutch booster being in the way. And it's expensive and you can destroy a high pressure power steering pump if you don't know what you're doing.

2. Tundra mod. Expensive though. You'll need 17" wheel/tire combo, the tundra adapter bracket and new discs and hubs and tundra m/c.

3. Put smaller tire/wheel combo on for your test. Then switch back for offroading. cheap if you can borrow a set of wheels and tires but doesn't really get you better braking.

 

[OSS]

Install stock sized tires for the test. It’s your 35” tires that’s creating the issue. It takes lot more braking effort to stop big tires.

 

[AussieHJCruza]

Thanks for the suggestions, unfortunately the modification laws are rather limiting here - this has been 6 months so far, working towards getting the truck registered.

1) the tundra mod increases my wheel track by more than 50mm which I'm not allowed to do (unless I do a full axle swap to 80 series axles which I believe should be able to be signed off) and I'd have to get engineer's approval for the 'non-standard' brake mounting bracket etc.
2) hydroboost would be similar, again because the engineer would have to approve the next round of changes to the braking system.
3) I have to do the test with the tyres I run on the road, so if she goes in with 33s, 33s will be the tyre size I'm allowed to run.

Must say I'm slightly envious of y'all in the USA with the modifications you're allowed to do.

I have found a caliper from a ~2005 Hilux that works with a 302mm rotor like a 60 but has slightly larger piston surface area and a physically bigger pad, wondering if this is worth a shot? Has the same bolt centres as the 60 caliper so should be able to be fitted 'under the radar'

 

[Seth S]

Braided lines are going to help a small amount but they are relatively low cost and easy to swap so a good place to start. The next thing to do is modify your pedal so it has more leverage. This might take some creativity but it’s probably the next easiest thing without re-engineering the rest of the brake system.

 

[relaxedcruiser]

The mid 90's Surf / 4Runner calipers should be just the same as the 60's but have two large pistons as opposed to the small and large piston in the 60 brake caliper You'll have less brake pedal effort, but a longer pedal stroke to archive the same pressure. Will feel more spongy....and this could be reduced with braided lines !
Its a question of leverage - extending your Brake pedal (difficult to do "under the radar") or reducing your M/C dia. or enlarging piston surface down at the calipers. The caliper option is maybe a good solution. The ~2005 Hilux option sounds good for not so old material....If you go for that please post outcome and exact year.
Sounds like the testing over here in NZ is also not as fussy as you have to deal with.
All the best for the next test - keep us informed !