Effect of Tires and Lift on Braking

[NMC_EXP]

I recently bought an '85 FJ60. Previous owners had made modifications including: (1) 3" lift, (2) 33 x 10.50 x 15 tires on Toyota chrome spoke wheels, (3) ARB front bumper w/winch, (4) full size Wilderness roof rack, (5) SROR rear bumper with spare tire & ladder.

The engine, drivetrain and brakes are stock. No fridge, drawers...etc inside.

This is my first FJ60 and my first vehicle with a lift and larger tires.

This FJ60 does not get in a hurry about stopping - enough so to be a bit worrisome. In contrast, my pure stock FJ40 stops with great enthusiasm.

I've read that a suspension lift, added accessory weight and larger tires will reduce braking efficency.

Question #1 is how much....5%....10%....20%....40%?

Heavier tires & wheels reducing braking makes sense due to the rotating mass. Added weight of gear in and on the vehicle makes sense.

Question #2 is does the lift itself affect braking by placing the weight higher above the hubs?

These questions assume a braking system which is in spec and functioning correctly.

Once the weather warms up I'll inspect the brake system. For now the pedal is not spongy, and no visible leaks. It just feels like it has about 50% to 70% of the braking power it should have.

Regards

Jim

 

[gregnash]

First question is when was the last time that your cruiser had a brake refresh? mine is pretty much the same way and I am going through the braking system and fixing things that I find wrong. I have heard that drum style brakes are not the best for "braking enthusiasm" but do the job. Having extra weight added to the vehicle; i.e. heavier tires, rack, bumpers, etc. will all add mass to the vehicle and will cause it to have a harder time stopping. Though not bad, I would consider the system somewhat anemic in comparison to other heavier vehicles that I have driven. I am still diagnosing my system but I have yet to lock up the brakes on my 60.

If there is nothing that seems out of sorts, no spongy pedal, no visible leaks, etc. then I would probably attribute it to the somewhat anemic braking system of the 60s along with the added weight of your accessories.

 

[60Dan]

Hi Jim,

Your absolutely right - the bigger and heavier the tires, the more effort its going to take in order to stop.

I just recently switched from 33" to 35" tires and Im running about a 2.5" lift so my braking has suffered a little. Not what your describing, but then again I have 4 disc brakes where as you have drums on the rear (if Im not mistaken)

This week im planning on installing a set of cross-drilled and slotted rotors with ceramic pads to help.
Another thing you can do, and I'll be doing this as well, is you can adjust your proportioning valve. When a truck is lifted and the proportioning valve isnt adjusted, the truck thinks its lighter than it really is and so sends more brake energy to the front wheels. Lowering the valve brings the shared braking effort between the front and the rears closer to stock.

Of course a cheap place to start is do a brake flush, and inspect your brake lines for leaks or cracks

Dan

 

[LaOutbackTrail]

What greg said.

Please check on MUD as there are several write ups and threads about brake system upgrades. On my previous FJ62 I installed brake calipers from a V6 4runner. They were larger (but bolted up) giving more biting surface. Unfortunately it required more fluid travel so made the system feel a bit spongy I will do the same thing plus add a non ABS early model Fj80 or T100 brake booster and master cylinder. I may go so far as buying premium discs. This in theory will increase stopping power.

 

[NMC_EXP]

Another thing you can do, and I'll be doing this as well, is you can adjust your proportioning valve. When a truck is lifted and the proportioning valve isnt adjusted, the truck thinks its lighter than it really is and so sends more brake energy to the front wheels. Lowering the valve brings the shared braking effort between the front and the rears closer to stock.

When you say "adjust" the proportioning valve do you mean physically relocate to a lower position on the vehicle?

Come to think of it, I do not understand how a proportioning valve works on a stock vehicle.

Regards

Jim

 

[LaOutbackTrail]

Another thing you can do, and I'll be doing this as well, is you can adjust your proportioning valve. When a truck is lifted and the proportioning valve isnt adjusted, the truck thinks its lighter than it really is and so sends more brake energy to the front wheels. Lowering the valve brings the shared braking effort between the front and the rears closer to stock.

When you say "adjust" the proportioning valve do you mean physically relocate to a lower position on the vehicle?

Come to think of it, I do not understand how a proportioning valve works on a stock vehicle.

Regards

Jim

Exactly Jim. What you'd need to do is unbolt the LSPV and then drop it down to approximately equal to the amount of lift on the vehicle. IE. 2" down for 2" of lift.

I haven't done it on my cruisers but did on my 4runner. Something like this:

Again, i haven't actually done this on my cruisers and it may be different than what i describe above.

 

[60Dan]

Exactly. Move it down - only a small amount. There is a formula somewhere, i'll see if I can dig it up.

This article is a good read, ref the proportioning valve in regards to lift

http://www.off-road.com/trucks-4x4/tech/increasing-rear-brakes-toyota-cheap-tricks-18518.html

Also heard of people running a T100 master cylinder and 4runner calipers on their 60/62 series with good results

Dan

 

[NMC_EXP]

First question is when was the last time that your cruiser had a brake refresh? mine is pretty much the same way and I am going through the braking system and fixing things that I find wrong. I have heard that drum style brakes are not the best for "braking enthusiasm" but do the job. Having extra weight added to the vehicle; i.e. heavier tires, rack, bumpers, etc. will all add mass to the vehicle and will cause it to have a harder time stopping. Though not bad, I would consider the system somewhat anemic in comparison to other heavier vehicles that I have driven. I am still diagnosing my system but I have yet to lock up the brakes on my 60.

If there is nothing that seems out of sorts, no spongy pedal, no visible leaks, etc. then I would probably attribute it to the somewhat anemic braking system of the 60s along with the added weight of your accessories.

When the weather improves I will inspect and overhaul the brakes if necessary. At this time I'm trying to get a feel for how much of a negative effect these modifications have on braking performance assuming the braking system is correct. Specifically, if the braking system was overhauled with new Toyota parts would this thing still be spooky to drive.

Regards

Jim

 

[UK4X4]

You may have sticky cylinders - old worn pads - contaminated pads - leakage through the seals on the master cylinder- ie your loosing pressure to the brakes
old brake lines-expand under pressure - loosing performance you have a multitude of little things to check.

 

[NMC_EXP]

LaOutback & 60Dan

Thanks for the info and link. This thing seems as though it has half the brakes it should and that may explain it.

For now I'm not driving it much. First thing that needs to happen is to inspect the brakes and replace/repair the wear out stuff as necessary. After that, I will relocate the valve.

Regards

Jim

 

[gregnash]

I dont know that there is an LSPV on FJ60s, only on FJ62s or so I thought. I have searched my truck and have yet to find one and I have an '85 FJ60 with no modifications what so ever (other than the desmog I did).

 

[NMC_EXP]

I appreciate all the replies.

Poked around on IH8MUD and found a photo of an FJ62 LSPV. Eyeballed the rear axle on my FJ60 and nothing there like on the 62.

I'm thinking there is more going on with the brakes on this vehicle than tires and lift.

What I need to do is: (1) buy a set of Factory Service Manuals, (2) start at the booster and work back through the system and inspect/adjust/replace/repair everything as required.

QUESTIONS:

1. Good (cheap) source for hardcopy FSM's?

2. As I recall there is more than one FSM for the FJ60 - which ones are "must have"?

3. On an '85 FJ60 are the rear drum brakes self adjusting? If so, do they adjust when backing up or when the parking brake is applied?

Thanks again

Jim

 

[LaOutbackTrail]

I (And I'm sure others too) will strongly recommend upgrading the hydraulics as mentioned earlier. Especially if you're going to be there anyway!

 

[hoser]

Give the FZJ80 brake booster a try. It's a popular mod on the 70 series and should decrease pedal effort.

 

[REDrum]

FWIW....

While upgraded hydraulic may be where you end up, start with fresh ceramic pads, flush fluid, rebuild/built calipers, and new rotors. Often fresh stuff can make a big difference.

Braided hoses help pedal feel too. Bigger master cylinder, et al, can come later.