1999 K2500 Suburban - TSM Disc Brake Change How-To with Pics

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by srracer, Dec 6, 2013.

  1. srracer

    srracer New Member

    I know I don't post often, but I'm just about finished installing the TSM kit in my Suburban and I figured I'd post a how-to since the Drum-Over-Hub version doesn't seem to have any references online (at least that I could find before I started this). I haven't completely finished yet (have to finish bleeding them tonight) so I can't review how they feel until at least tomorrow, but rest assured, I'll provide a complete review then.

    The kit I purchased was the *complete* TSM kit with new e-brake calipers (with the brackets) along with the stainless flex lines and the e-brake spacers. Total cost was $825 shipped to the East Coast. (I'm getting no renumeration for this, fwiw)

    First off, remove all existing stuff in the normal way: Wheels, drums and all drum brake hardware. I didn't document this part because it's in the various manuals.


    Then, remove the 8 bolts that connect the hubs to the axles and pull out the axles.

    After that, you need to remove the hubs by removing the hub nuts. These nuts should not be on tight so you don't *have* to get the tool if you don't want. (You would need it if you are replacing the bearings). First pry off the clip that is holding the key in place.

    Then use a magnet to remove the key. You might need to use a punch and give the nut a slight rap so that the key is loose.

    Then remove the nut. Again, it should not be heavily pre-loaded. A light rap with a hammer and punch would be the most you should need.

    Now you have the hub off:

    Then, I wrapped up the hub surface with masking tape to prevent any dings, damage or paint from getting on them.
    - - - Updated - - -

    Next, cut (or remove, but cutting is soo much faster, and you're going to need to resize it later anyways) the brake line going into the back of the wheel cylinder. I used a little air body saw and it took about 15 seconds.


    Then, use a big hammer (I used a 4 lb sledge) to remove the old drum backing plate. This is bigger and heavier than I expected it to be.


    This is a good time to brush and scrape any loose rust from this area:

    And give it a coat of some underbody paint. :) Then, the bolt first bracket onto the same surface as the old backing plate using the same screws.

    Note the orientation of mine. You'll see that I ended up installing my caliper at the bottom of the hub. This was not where I originally wanted it.. I wanted it about 90 degrees (a little less than that, actually) clockwise towards the rear... But the OE E-brake cables are not long enough on both sides and the e-brake bushings that TSM sells (for the extra $20) are too straight anyways. To mount the calipers towards the back would really require a custom e-brake cable that bends out of the way of the axle and is about 3-4" longer. If you do a lot of offroading, this would probably be worth it.

    Next, mount the additional bracket pieces. NOTE: DO NOT USE THE SPACERS AS INDICATED IN TSM'S INSTRUCTIONS. The spacers will make the spacing incorrect - at least they did for my truck (99 K2500 with G80 option). I did not tighten the bolts nuts yet..

    Temporarily install the caliper to the brackets. This will make sure the bracket arms are spaced exactly correct (there's just enough play that I think if you don't do this you could end up fighting the caliper bolts later).

    Now, tighten the bracket arm nuts/bolts.

    - - - Updated - - -

    Next up is preparing the E-brake connections.

    First, adjust the bracket on the caliper so that it is as angled as far away from the axle as possible. I did this by using a wrench and just taking up the clearance as much as possible.


    Then, use a dremel to slightly enlarge the bore hole in the bracket. You don't need too much here.. Just enough to let us tweak the spacer away from the axle.

    This is the *worst* part of the whole job - removing the existing springs on the e-brake cable. I used a dremel cutting wheel. I held the spring with some dykes and the scored (without breaking through) one side of the whole spring. Then I rotated it 180 degrees and cut through it. Then, I could use the dykes to bend/remove each ring remaining after the cut. 1st spring took me probably 30 minutes... 2nd spring was probably closer to 15.

    IMG_3355.jpg IMG_3357.jpg

    Now, you need to 'massage' the spacer a little. Again, this is where custom e-brake cables would make this install a lot better, not the least of which would be having the caliper towards the rear of the truck. I used a vise and a long steel tube cheater to put just a slight bend in the the stainless spacers. I did have to rework the end a little bit after bending so that the end fit into the bracket hole with a little play and so that the e-brake cable nipple could fit through the spacer.
    IMG_3358.jpg IMG_3359.jpg IMG_3360.jpg
    Last edited: Dec 6, 2013
  2. dsfloyd

    dsfloyd Epic Member 5+ Years ROTM Winner 1000 Posts

    Great write up and pics so far. Tagging to see the rest of the posts on it.
  3. srracer

    srracer New Member

    As you can now see, the tweaking allows the spacer to clear the axle.

    While holding the spacer at it's "max clearance" position, I threw a quick tack weld between the spacer and the bracket to hold it. I did not use the spacer 'retainers' that TSM ships.

    While I had the welder out, I test fit the braided line locations and welded in the tabs for the flex line ends.

    Make sure to put out any paper towels that happened to catch on fire!

    I also used some Rustoleum cans to get some paint onto the spacers and welded brackets at this time.

    Now, it's time to start putting the hub back together. Remove the tape and slide the hub back into position. Installation is the reverse of the removal. The nut only needs to be finger tight. Assuming that you didn't touch the bearings, the nut should go to exactly the same alignment position as when you removed it. Install the key, the key retainer and then the axle.

    Next up is the rotor. The rotors come from TSM with 2 sets of holes. One set is a larger diameter than the other and will float. Do not use this set - these are for the OEM application of the rotor (I believe) where the rotor is aligned by its inner hub ID. On ours you need to use the snug fitting holes. Unfortunately for mine, they were too snug. I could have gotten the rotor on using lug nuts, but I never would have gotten it off. So I drilled all those holes out an additional .006" or so with a 19/32 drill bit. The fit was still snug, so I know its well centered, but it will be considerable easier to remove later. Hold the rotor in place with a couple of lug nuts.

    Next is a little tricky. First, grease the pad backs and caliper pins, then, reinstall the caliper over the rotor. Then you have to perform the first e-brake cable adjustment - the tricky part is that this adjustment has to be done without the e-brake spring on the caliper. Popping the spring off is easy enough but getting it back on was a bit of a bear. You can do this *before* you tack weld the spacer in place, but then you'll need to assemble/disassemble the caliper a couple of extra times.

    Take the spring off (obviously without the cable attached to the e-brake arm) and then by hand actuate the e-brake arm as far as it will go. It will move the piston out. Keep cycling the arm until the piston no longer moves. Then reinstall the spring and now you can install the e-brake cable through the spacer, through the spring and hook the nipple into the e-brake arm. The last step involves a bit of wrestling with a pair of solid pliers, but its not bad once you get the knack for it.

    At this point, you should actuate your e-brake pedal and make sure the caliper holds the rotor. If it doesn't, you didn't make enough 'adjustment' when the spring was off. If you did, the caliper should be holding strong on the rotor.

    Now you can install the flexible lines up to the brackets.


    Here's what it looks like:
    IMG_3370.jpg IMG_3371.jpg

    Final step is to bend, cut and re-tip the brake lines. The flex lines use 3/8-24 fittings and require a flared end.
    Then it's time to bleed. You'll notice in the right side picture below that I've modified a banjo bolt to put a bleed screw in it. If you copy this installation, this was a nifty mod as it lets me bleed a little cleaner/better. Since the bleed screw is below the banjo bolt in this caliper orientation, then the other options are to remove the caliper for bleeding (so you can rotate the caliper such that the bleed screw is the highest) or crack the banjo bolt to let air out (might work but may not get all the air).

    I use 2" rear wheel spacers. When finished, with the 2" spacers, this is what mine looks like:
    This definitely wouldn't be my choice if I was a big offroader - it just feels too exposed. If I ever have the inclination, I'll get some custom e-brake cables made up.

    Here's what it looks like without the spacers:

    IMG_3373.jpg IMG_3374.jpg
    More protected, for sure, but still in a vulnerable place if you're a rock crawler type. In the above pics you can also see my modified banjo bolt bleeder. I would advise these for everybody, except that the off-the-shelf banjo+bleeders do not come in the size we need for these calipers (7/16-20). If anybody knows a place to buy these, please let me know.

    After I get the system filled and bled, I'll post my reviews.
  4. srracer

    srracer New Member

    So I've now had the chance to bleed them and burnish the pads and now that the pads have come in I'm feeling pretty good about this change. I still think there's a little air in the lines that I could get out, and I'm not 100% convinced that there isn't something amiss with the combination valve (the driver's side front caliper seems to have considerably less flow/pressure than the passenger front during bleeding), but as the pads came in, the braking was definitely better than the drums - and most importantly - hard braking above 40mph didn't cause the truck to shoot to one side; something I always wrestled with on the drums and those stupid adjusters that never worked.

    That said, the e-brake capability isn't all that impressive yet. I may need to tighten up the e-brake cable adjusters as I can get it to the floor.... It will slow the truck down to an eventual stop from 30+mph, but you're not going to stop quickly by any stretch. They'll hold the truck on a hill, but probably wouldn't want to count on them for much else.

    I'll be happy to post back after I have some real miles on them.

    Hope this helps!
  5. srracer

    srracer New Member

    Haha.. well, based on the responses, I'm not sure that people care much, but I figured I'd report back.

    Brakes are awesome! The pads have come in and some more bubbles have worked their way out on their on and here's the scoop:

    I can now actually engage the ABS. I haven't been able to do that in a couple of years.
    Once the bubbles worked out, the pedal is as firm or firmer than than I've ever known it (owned the truck since 2001).

    The e-brake has proven to be better than I gave it credit for. I don't know if it's that the pads have come in or my multiple actuations and pressing of the pedals have gotten an extra click in the internal caliper adjusters, but I tried it today from 50mph and it stopped the truck in 13 seconds.... you're not locking up the rears with just the e-brake, but it will get you stopped if the poop hits the fan.

    So, would I do it again? Yes - definitely. If I owned a 2nd truck, I'd order another kit. Now that I know how it works, and I know what measurements to look for, I'm not sure if I'd order the whole kit from TSM.. but I wanted this to work without hiccups for my timeframe and TSM looked like the best choice on that. I *would* order the calipers from TSM again, for sure.

    Happy truckin'!

  6. taggat

    taggat New Member

    Hell yeah Chris!

    Ive only owned my GMC for a short while but the brake pedal seems squishy and soft, from what I hear its common with all of them.
    Id be interested in doing this swap as well, same thing mash on the pedal pulls to the right.

    Whats the thickness of the caliper mounting plate? 1/2" or more?
    My reasoning is if you could just just order the hub bracket as it looks like the toughest peice to fab "the od of the hub as that should be as tight as it could be" and then you could make your own caliper brackets easily and possibly fit a front end setup to the rear. You know junkyard upgrading for a 1/4 of the price.
  7. BurbanMan

    BurbanMan Rockstar 3 Years 500 Posts

    Great write up! Thanks a ton!
  8. Crawdaddy

    Crawdaddy All hail the Mad King!! Staff Member 5+ Years 1000 Posts Platinum Contributor

    The caliper being on the bottom is bothering me a lot since there's no way to get a good 100% bleed on it. Otherwise, good work.
  9. taggat

    taggat New Member

    Mighty Vac Pump would get it out easily from that positon. 100%? Not sure.
  10. srracer

    srracer New Member

    The bleeder+banjo bolts worked perfect for bleeding them out.

    In retrospect, I'm pretty sure they would have bled just as well by cracking the banjo bolts. I bled the banjo bleeder after every round at the caliper by gravity only - i.e., bleed with pressure or a buddy through the regular bleed screw and after the flow looked nice and clear of any air I closed the regular bleeder and shut down the pressure and then simply cracked the bleeder on the banjo until fluid dribbled out. Like I said, worked perfect. A mighty vac alone on the bleed screws would not get it done, in my opinion.

    As for the thickness of the steel, from memory I think they are ~5/16" - 3/8" thick pieces. Definitely not 1/2".


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