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Question on using larger brake booster

Question on using larger brake booster

Question on using larger brake booster

I asked this question in a car repair forum. No replies from there.

I have a 97 pickup, rear wheel drive, used as a spare vehicle. My wife's car (disk-disk) stops very quickly. To her, the pickup (disk-drum) doesn't want to stop. She refuses to drive it. My car is disk-drum, but stopping is not as bad as the pickup. I can replace the single diaphragm brake booster with a double diaphragm. What do I need to be aware of?

For your information, the pickup has ABS on all 4 wheels. The same model gets disk-disk and double diaphragm booster in 99 and later. Thank you.

RE: Question on using larger brake booster

After 99 did they also go to larger front disks?
If so then I would look at switching both the booster and the disks.
I don't think that the booster alone will help enough to make it worth while.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Question on using larger brake booster

99+ model has a caliper with larger piston diameter, same diameter disk (slightly thicker though), a master cylinder with a larger core. I cannot get the thicker disk because the bulkier caliper interferes with wheel.

Doesn't double diaphragm double vacuum assistance?

RE: Question on using larger brake booster

Calipers with larger piston diameters will produce more clamping force with the same pedal pressure but might also require greater fluid volume to flow. The thicker (heavier) disk will just build up heat slower (think, downhills or repeated panic stops) and won't change available braking force in a single stop without considering fade (heat buildup).

The double diaphragm might increase the maximum available vacuum assistance, but the ratio between input force and output force (up to the maximum) is determined by a little valve and mechanism inside the workings. You also don't know whether the piston diameter inside the master cylinder is the same.

In short, "not enough information" and the information you need might not be readily available.

If you don't have excessive pedal travel right now (i.e. good firm pedal) and you can get a set of used later model calipers cheap, I'd swap those first and see what happens. Make sure you can't push the brake pedal to the floor before you drive it!

RE: Question on using larger brake booster

Think about switching to higher friction brake pads in the front. A lot of the so-called "lifetime" pads have a relatively low friction coefficient and switching to a more aggressive pad will certainly reduce your stopping distances and the expensive of pad and disk. See if Hawk of Performance Friction have pads that will fit your calipers.

RE: Question on using larger brake booster

You might be able to find higher coefficient of friction pads too but not really sure if they would be available for your truck. You might try contacting someone like Stop Tech to see what they have available.


The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: Question on using larger brake booster

Check to see that the rear drum brakes are working at all.

Mike Halloran
Pembroke Pines, FL, USA

RE: Question on using larger brake booster

I'll second Mike's comment.

With regards to pads, a number of aftermarket manufacturers will make you a set of pads with the desired friction material if you provide them with the backing plate.

RE: Question on using larger brake booster

Thank you for your advice. I will carefully consider all points brought up by you.

RE: Question on using larger brake booster

Step one is to verify that the system is working correctly per factory, and understand the complaint.
If the complaint is "it takes too much pedal pressure to stop the vehicle" and the pedal effort is typical for that vehicle, then the question is how best to reduce pedal effort.
Higher friction pads might be easiest. The double booster might also be fine - it helps her push harder on the pedal.
When you look at reviews for that vehicle, are there comments about brake effectiveness or pedal effort?

Jay Maechtlen

RE: Question on using larger brake booster

After reading your replies, I decided to go ahead and replace the single diaphragm booster with a double diaphragm type. Now the vehicle is stopping well, just as I hoped. Thank you.

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