New disks...old pads...OK?

My XJ budget is small. With that said, I am about to replace my D30 with another one. I replaced the brake pads on my current axle about 4000 miles ago but didn't turn the rotors. They have been squeak/trouble free and I was wondering if I could reuse the pads on the new axle, with new disks, without any ill effects? Am I in for a squeak-fest or prematurely damaged disks? I know it's only 50 bucks for new pads, but I want to get this thing installed for an upcoming trail run and I am out of XJ $$$. Would it be better to wait and skip the trail run or would it really matter?

Thanks!

If your pads and rotors have flat surfaces, it should present no trouble whatever. It is typically preferred that the parts are not replaced together anyhow.

If you're not absolutely sure about your old pads, a few minutes with a belt or disc sander (don't breathe the dust!) will give assurance. Work with a stationary sander or a stationary part, and use a 180-240-grit paper.

Sand some of the ridges and grooves of of the pads and throw them in there, I use 100 grit, sealed sand paper. Break them in just like a new set, take it easy and don't overheat the brakes for a couple of weeks or 500 Miles. The pads wear into the disc and vice versa, an extra $35 bucks isn't all that much money. The normal scenario is to have new pads wear into old discs.
A couple of small stones in the wrong place could mess up both your new pads and disc, pretty quick anyway.

If the disc/rotors look fine and aren't excessively worn or grooved, I wouldn't bother replacing or turning them. Save your money.

Thanks a lot for the good feedback! My current disks ('91) are very grooved with 204,000 miles on them so it is time to junk them. The disks on the "new" ('96) junkyard axle are VERY rusty and the cost of new disks is only about 10 bucks more per set than having somebody turn the rusty disks so there is no point in trying to salvage them. With only 4000 miles on my current pads, I will take your advice, carefully sand them flat and break them in like I would a new set. This will allow me to STOP THE $$ HEMHORRAGING! I can't wait to get to it! The reason for my haste is the upcoming trail run...I just swapped in a 2001 Chrysler 8.25 29 spline with 89,000 miles on it in 3.55. My D30 is still a 3.07 so I need to get this new axle in with 3.55 ASAP. Thanks again! Later.

just get the pads bro 20 bucks is well worth it

My old pads are top notch. The XJ already doesn't stop very well. I was trying to avoid that expense again...do the cheapo 20 dollar sets significantly underperform a good Raybestos or Hawk version, or similar? I have never had cheapo pads on the XJ so I just don't know...

XJ AV8R said:

My old pads are top notch. The XJ already doesn't stop very well. I was trying to avoid that expense again...do the cheapo 20 dollar sets significantly underperform a good Raybestos or Hawk version, or similar? I have never had cheapo pads on the XJ so I just don't know...

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What year is your rig? The early XJs (single diaphragm brake booster) are notoriously underbraked - towing is an adventure! The later rigs have dual diaphragm boosters, and they stop rather better. Swapping a later booster into an early rig is a common upgrade.

That being said, I've never bothered with the "special" pads - Bendix or Raybestos are the order of the day. Brakes are not something I'll ever "cheap out" on - it's worth the peace of mind to know I've got something good getting me to stop...

5-90 said:

What year is your rig? The early XJs (single diaphragm brake booster) are notoriously underbraked - towing is an adventure!

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My XJ is a '91. No kidding on the towing adventure! I used to tow a small travel trailer with it. If it weren't for electric trailer brakes it would have been A LOT more interesting! I remember reading something about the booster upgrade a long time ago but didn't consider it at the time...and then forgot about it. What was the year break for the dual diaphragm booster? I will have to research this more thoroughly.

Bendix or Raybestos are the order of the day.

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Good. I usually go for the Raybestos. I think they cost me about 50 bucks for the set last time I did it. Nothing too fancy but not bottom of the barrel either. I will stick with that.

Thanks for the info 5-90. I will search for a thread about the booster upgrade, necessary modifications, etc.

XJ AV8R said:

My XJ is a '91. No kidding on the towing adventure! I used to tow a small travel trailer with it. If it weren't for electric trailer brakes it would have been A LOT more interesting! I remember reading something about the booster upgrade a long time ago but didn't consider it at the time...and then forgot about it. What was the year break for the dual diaphragm booster? I will have to research this more thoroughly.



Good. I usually go for the Raybestos. I think they cost me about 50 bucks for the set last time I did it. Nothing too fancy but not bottom of the barrel either. I will stick with that.

Thanks for the info 5-90. I will search for a thread about the booster upgrade, necessary modifications, etc.

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I'm wanting to think it was 1996, but that may be a bit late. The main reason I haven't done it is because I've not determined if the early master cylinder can be mounted to the late booster, and I'm not a huge fan of the aluminum/plastic "composite" cylinders that are used on later vehicles (you otherwise have to swap the cylinder and booster - a "loaded" booster.) All iron or all aluminum is fine with me - aluminum/plastic, not so much. The plastic reservoir is sealed and retained with rubber O-rings, and I've seen what brake fluid can do to rubber hoses - merci, non, monseiur Murphy.

search for wj booster and master swap.

did it to my 89 with 31's and can stop on a dime, even when towing a 5x10 trailer.

the 1996 has the shorter arm that will work in the older models. Everything I read says it's a direct swap except for a little bit of shiming to get the right angle on the MC. I have a line on a 96 MC and booster. Should hear from the guy tonight. Then just need to decide if I want to do the 8.25 swap before I do the disc conversion.

Here's a great writeup on the swap -

http://www.naxja.org/forum/showthread.php?t=924285&highlight=brake+booster+swap+1996