spongy brakes on '98 burb

[nikwho]

My wife's suburban's brakes are acting up. Kind of a spongy feel and you dont feel like you're getting a whole lot of stopping power even if you have to mash on the pedal. Its seems fine w/ normal driving around town, but if you really have to stop quick it just doesn't want to. Is this some kind of common problem? Thanks, Nik

[nikwho]

It doesn't pull, no major obvious problems. No super hot rotors or drums. The shoes on the back are about ready to be replaced but nothing very obvious going on. I was thinking maybe it could be a vaccume leak?

[buffle]

I know this sounds crazy. My 1999 Tahoe had really spongy brakes , had them checked and were fine. Then later I had trouble with the battery and found I needed an alternater and new battery. After I installed these it was like a new truck. It ran better stopped, stopped better ,the air worked better and overall it solved all my problems. I guess every system in the truck depends on a good flow of electricity, it sure did in my tahoe.

[bwood]

Here are some threads that touch on this same subject:

http://67-72chevytrucks.com/vboard/s...ghlight=brakes

http://67-72chevytrucks.com/vboard/s...ghlight=brakes

This complaint is common on these trucks and I would bet the back brakes needs some attention. How far down does the brake pedal travel, and does it hold the truck well? It you answers are "to the floor and no", pull the drums and manually adjust the brakes and go for a test ride.

[nikwho]

looks like the first order of business will be adjusting the rear brakes. Thanks guys

[nikwho]

Ok, The pedal does NOT go to the floor. The brakes hold the truck just fine and stop ok under normal driving conditions. New brakes all the way around. Manually adjusted rear drums after installing new shoes. It has a new alternator and a good battery. Brake fluid is good in the reservoir too. Tires are about a 32" equivilant. 285-75-16, I think, so not a very big tire. No lift. My wife continually complains that it has no real stopping power if she really needs to get on the brakes. She thinks that its going to cause her to rearend or hit someone if she needs to stop suddenly. I have mashed on them VERY hard and it stops at a pretty slow rate. Its really stumping me. I've checked everything that I can think of. Any other ideas or suggestions?
Thanks, Nik

[bwood]

Is this a new problem or how it has always been this way? Looking at your original post, it sounds like it is a new problem. You may have a failing component like a caliper or wheel cylinder that is not moving smoothly or failing brake line? Its hard to say over the internet. You say the fluid at the master cylinder is good (clean?) but I wonder how the fluid is at the wheels? You might consider bleeding them. You may already know, but when you bleed them, start with the driver front, then pass front, then driver rear and then the pass rear. You're suppose to start closest the master cyl and work your way to the farthest away.

The tires are about 2.3" taller than the stockers (my math show the LT245/75R16 @ 30.46" and the LT285/75R16 @ 32.8"), this sounds small but it will affect braking. You've added about 7.6% (1.17") to the distance from the wheel center to the road. That doesn't take into account the added rotating weight of the larger tire (I show an average weight of 45 for a stocker and 58 for the 285). The tire has more leverage against the brakes than before.

I have always felt that the brakes on these truck were not what they should be in the 1/2 tons especially. In my previous posts about adjusting the rear brakes, I have found this does make the pedal feel better and the truck doesn't lunge foward as much, but my issue still exists, it just isn't as bad.

[TwoFiftyShifter]

Have you bled the brakes recently? My 96 had weak pedal for a while, the combo of repairing a leaky brake line, adjusting the rear shoes and bleeing the brakes front and rear fixed it.

[Zeke]

Not sure if this will help, its for a 95 with ABS brakes. Appears there is a little more to do with ABS and can be a long drawn out process.

TWO PERSON PROCEDURE (PREFERRED)
Gravity and vacuum bleeding are not recommended for this ABS system.

PROCEDURE
1.Raise the vehicle to gain access to the system bleed screws. Install clear tubing on the bleed screws so that air bubbles in the fluid can be seen. NOTE: Never pump the brake pedal as fluid cavitation may occur.
2.Begin by bleeding the system at the right rear wheel, then the left rear, right front and left front.
3.Open one bleed screw at a time 1/2 to 1 full turn.
4.Slowly depress the brake pedal until it reaches its full travel and hold until the bleed screw has been tightened. Release the brake pedal and wait 10-15 seconds for the master cylinder to return to the home position. NOTE: Repeat steps 1 through 4 until approximately 1 pint of brake fluid has been bled from each wheel. Clean brake fluid should be present at each of the wheel bleed screws. Check the master cylinder fluid level every 4 to 6 strokes of the brake pedal to avoid running the system dry.
5.After bleeding all four wheels, use a Tech 1 Scan tool to run 4 functional tests while applying the brake pedal firmly.
6.Rebleed all four wheels using steps 1 through 4 to remove the remaining air from the brake system.
7.Evaluate the brake pedal feel before attempting to drive the vehicle and rebleed as many times as necessary to obtain appropriate pedal feel.

[nikwho]

I appreciate all of the input guys. We have not owned this vehicle for very long so im pretty sure that its be the same way since we got it. It stops fine under normal driving conditions. no problems at all. I tried to mash on them pretty much as hard as i could to stop quickly yesterday and it was not even enough to make my dogs loose their balance! :-) I have had a truck with factory brakes and 42" tires stop better than this thing! 32" tires should not take this much away from the brake system! I guess that I will try bleeding them. But one of you said FL, FR, RL then RR and another said RR, RL, FR then front FL. Is the sequence important and which way should i do it if so???

[bwood]

Originally Posted by nikwho

But one of you said FL, FR, RL then RR and another said RR, RL, FR then front FL. Is the sequence important and which way should i do it if so???

I was always taught start with the closest to the MC. My Chilton's doesn't say.

[Zeke]

I just cut and pasted info from ALLDATAdiy.com, basically a factory shop manual online. I was taught master cyl, farthest wheel, next farthest etc. Never told why and don't know if it makes a difference.

[nikwho]

Ok, I bled all of the nasty, grungy dirty dark green brake fluid completely out of the system. It looked like undiluted simple green. I'm assuming it was the brake fluid from the factory. It was extremely dirty! Probably thirteen years old!!! I bled that completely out starting at the drivers left, dr. rt., rear left, and finally rear right. I used two of the big two quart bottles and bled it until it was completely clean. After that I installed new pads and shoes. Went for a test drive. Better but not good! I pulled the drums back off and noticed that there was only wear marks on the very center of the new shoes! only about 1/2" wide!!! so, thats all that was contacting on the rear drums! so I took the drums and rotors into napa. I had the Rotors turned down and the drums were WAY out of specs! Bought the highest quality drums that they had in stock and it made a world of difference! My wife spilled her coffee this morning because she stepped on the pedal with the usual force and it stopped in a hurry! So problem solved! Thanks for all of the help guys!!!!

[nikwho]

Since my rotors were turned down to the minimum specs, I know that a new set of rotors will be in coming before too long. What do you guys think about the cross drilled and slotted rotors that summit sells for $100 each??? They did an article on them for tip of the month in super chevy with a $1000 set of calipers but im wondering if they'll help things out with just using my stock calipers. here is a link:
http://www.summitracing.com/parts/SSB-23045AA3L/

[danomano]

I have always been told that the Suburban, Tahoe, (Any heavy truck) are hard on the braking systems. The rotors and drums are like throw away parts due to the wear. It seems you got lucky on your rotors.
I am think next pads to go with the carbon fiber as those seem less hard on the rotors and drums.

[ChevLoRay]

Front brake rotors and hubs on the 2WD trucks are "one-piece". I hate that fact but don't know how to get around it. So, even the cheapie rotors are (my best price) about $53 each. I bought rotors for the wifes' Lexus for less than $20 each. GM got to us on that item.


So, the question about drilled, slotted, drilled/slotted and the pricing is one of preference. What I'm wondering is if the rotors that they use to drill and slot are the same basic cheapie rotor that you can buy for half the price without the drilling and slotting? Can you say China?

[nikwho]

Well, ours is a K1500 burb so the rotors are just sandwiched between the hub and the wheel. Cheapies from NAPA are about $35 with thier higher quality parts being around $65. I wonder if the higher quality NAPA rotors are better than the $100 drilled and slotted versions from Summit. What is the cross drilling and slotting going to do for me? keep brakes cooler? make pads last longer? give the rotors more bite and better braking characteristics? i dont want to spend the extra money just to look cooler!

[danomano]

Read here on cross drilled rotors
http://stason.org/TULARC/vehicles/vw...ed-rotors.html

[Zeke]

FWIW here is my take on drilled/slotted rotors and braided brake lines, people who bought them say they can stop better (plus they look cool) My brother in-law put drilled rotors on his honda and swore they stopped better, he does complain that when the rotors get wet the holes will rust and mess up his wheels. Having driven his car before and after I couldn't tell the difference but its not my car and I don't drive it like he does, he is also a left foot on the brake kinda guy so I guess he needs the extra cooling. I been awhile but I think if you cut a stock brake hose you will find it is braided also, it just has a rubber cover on it. The advantage of this is you don't get dirt and crud between the braid and rubber part of the hose not good on moving parts so you might wind up replacing them more often.

[bwood]

In post #4 of this thread, 2nd link is info on this very subject. I would stick with the higher end parts store stuff and good pads.

[nikwho]

Thanks Bwood! I had read that thread back when it was new. I missed it the first go around on this thread. Thank you!
Nik