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Rear Disc Swap

Old 11-08-2010, 09:19 PM
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Rear Disc



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Old 11-10-2010, 05:23 PM
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Tonight, the proportioning valve comes off. Going to straight-line the rear lines to the hard line and see if that makes the difference, per James at Sky Manufacturing.
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Old 11-22-2010, 10:51 AM
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Remove LSPV, add Proportioning Valve

Pulled the LSPV, plugged both ends of the hard brakeline that went from it past the gas tank and to the front right brake line. Pedal feels pretty much the same.

Drove to Dave'z Offroad in Placerville, Thanks for your help and the sweet, reasonably priced, bolt-on proportioning valve with adapters, Dave!

Put it on. Figured I'd bench-bleed the MC. Then I bled everything again. Pedal is the same. Driving it last night through the blizzard we're amidst, the back brakes work better than they did (no locking up unless I wanted to), but the pedal remains soft. .. and I remain perplexed.

Reviewing the banjo bolt I used, I see I used Napa PN 82703, an 10x1.5" banjo bolt that's 1 5/16" long. Dang. Should have used what Elvota recommended in no uncertain terms - a banjo 1/8" longer, Napa PN 82700, 1 7/16" long is the right banjo bolt. I was eyeballing what I needed before I found this thread. Oh well - I was close. Will plug that in tomorrow and see what happens - seems to me it could solve the problem.

Elvota, I don't mean to hijack your thread. I can go elsewhere and fumble through this.
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Old 12-24-2010, 11:43 AM
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Well, I haven't tried anything new since the last post, as the truck was working fine (3 brake pedal pumps to normal) and I've only been driving around in the snow as needed. I did replace the eyeballed banjo bolt with the right one (see previous post), but that didn't make much of a difference.

I see here
http://www.4x4wire.com/toyota/faq/parts/
that the master cylinder on my '84 was 13/16" bore. The FJ80 MC that I put on is only 3/16" larger. Given that this is a long bed extra cab, and these rear calipers and brake lines are large - and given that I distinctly have "low pedal" (described here in Pirate 4x4's "Brake Bible" - http://www.pirate4x4.com/tech/billavista/Brakes/), I have to wonder if a larger MC is in order. I'm moving a lot of brake fluid here, possibly more than with the stock 8" drums on.

So, anyone know of a MC with a larger bore that mates up to the Yota booster?

Right now, I'm pulling the engine and transmission, as I am dropping in a VW TDI and doing all of that associated seal and gasket replacement, etc... etc... All y'all's posts throughout Yotatech are really helpful to newbies like myself... Keep 'em comin'.
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Old 07-03-2011, 12:08 PM
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I just did this swap this weekend and really like it. I figured I'd just add on to this post rather than start a new one. Elvyota did an excellent write up and I followed his basic procedures on my 91 V6 extra cab truck. I'll note the similarities and some differences.
1. I found the stock axle bearing studs to be long enough without replacing them. They get full depth in the nuts on the back side of the axle plate so that was nice not having to replace them.
2. I'm currently using the stock V6 MC as it is a 1" bore. I also used the stock rubber hoses for the calipers and just cut and re-flared the toyota brake lines for the SAE nuts/flare. I did have to slightly ream out the nuts with a drill to slide over the toyota brake lines.
3. I left the LSPV in place (I have a non abs truck) and set it for a 'less loaded' setup (i.e. the opposite of what comes with most lifts). I found the brakes with the LSPV to be just right with the back locking up just after the fronts and I could only get that on gravel, on pavement I could only get a little squeal and not a full skid.
4. After a couple of days driving around including a 400mile trip the brakes feel like they have a little air in them but I'm not getting any out of the bleeder. That feel is less as the pads are getting broke in. I do wonder if I need the 2lb residual valve that I have heard others refer to. I have a LC MC that came with the stuff I bought but it looked exactly like the one on my truck so I didn't change it but I've heard they have that 2lb residual valve built in.
overall a great modification, gives much better confidence especially if you are carrying or towing a load with the truck.
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Old 07-29-2011, 01:59 AM
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I'm sort of confused on the diagram from the first page. Why is only the rear line running to the ABS box, and then to the LSPV. While the front is routed directly to the LSPV? How does the LSPV work on a ABS and non-ABS system? All I know is it controls brake balance between the front and rear.
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Old 07-30-2011, 06:31 AM
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why isn't this sticky'd ? put all the info in 1 big section
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Old 12-04-2011, 09:23 PM
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Sky Rear Disk Brake Conversion, 1 year later

A year later and the low pedal has resolved itself. A normal braking motion - 1 push - stops the truck perfectly under average driving conditions. If it's quicker, I do 1.5 - 2 pumps, stopping fine on the second pump. The back brakes actually lock up slightly before the fronts - a fine tuning I will get to eventually. The whole system remains bled and as fresh as it can be a year out now - I haven't touched it for a year.

Been busy. The truck got a '97 1.9 liter VW TDI over the past winter.
http://forums.tdiclub.com/showthread.php?t=304345





(I didn't have to disconnect the brakes at any point throughout the diesel swap.)

91diesel, let us know how your rear discs are working out in a year.
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Old 09-05-2012, 06:00 AM
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Old thread I know but I just completed this swap and I have a bit of a problem.

Got the old drum equipment removed, bolted up the new brackets and calipers and now my wheels wont fit over the calipers :-/

I've got M/T sidebiters they're 15" with 3.3" backspacing, http://www.mickeythompsontires.com/w...item=SideBiter
which meet the requirements on sky's website
http://www.sky-manufacturing.com/new...uct.php?id=128

unfortunately the caliper body digs into the inside of the wheel... I'm thinking my only options are to either grind down the caliper to fit, or add a wheels spacer, neither option is something I'm interested in doing...

Anyone else have any other suggestions?
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Old 09-05-2012, 06:06 AM
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How much would you have to grind?

The caliper hits on the inside of the mounting surface of the wheel is what you are saying right?

:wabbit2:
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Old 09-05-2012, 07:47 AM
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Originally Posted by waskillywabbit View Post
How much would you have to grind?

The caliper hits on the inside of the mounting surface of the wheel is what you are saying right?

:wabbit2:
no the clearance to the mounting surface is fine it's the inner diameter of the wheel that is problematic... I'll try to get some pics

I say that spacers might help because the inner wheel is tapered slightly, as is the caliper body so the further out the wheel is the more space I'll have. I really don't want to run my wheels further out, not to mention I'm pretty sure the mounting surface of the rotors are thicker than the drums so they're giving me a few mm of spacing already :-/

Last edited by twistedsymphony; 09-05-2012 at 07:52 AM.
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Old 09-05-2012, 07:49 AM
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Not much to do other than wheel spacers or new rims.

Not really anything to grind unless it's just the least bit.

Sucks.

:wabbit2:
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Old 09-05-2012, 08:18 AM
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Has anyone evert done a FRORF rear-disc conversion on a 5-lug 2wd (vs. 6-lug 4wd), using a drive-flange rather then a locking hub? I like the idea that you can install the locking-hub (for flat-towing), yet I can see never flat-towing and just wanting rear-discs with factory e-brake. Thanks.
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Old 09-05-2012, 03:30 PM
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since it was quite difficult getting a view through the large spokes on the wheel my friend and I marked the top of the caliper with chalk and put the wheel on to get an idea of where it was rubbing





the wheel isn't so much tapered as there's a small step (the diameter is slightly smaller near the mounting face of the wheel... it's this step that rubs the caliper...

you can see it rubs in the center of the body as well as the outer edge of the upper ear.

I am able to get the wheel to mount flat but it pushes on the caliper..
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Old 09-06-2012, 08:06 AM
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I realize it's not preferable, yet is it time to start thinking about new wheels? Because I'd be real careful about grinding too much of that caliper body down.
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Old 09-06-2012, 10:26 AM
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These are pretty much brand new wheels and tires... I'd rather swap back to drums than eat a few grand on new wheels and tires.

looking around I found a few other disc brake setups
http://www.pirate4x4.com/forum/showthread.php?t=969800
http://www.lowrangeoffroad.com/index...onomy-kit.html
http://www.ebay.com/itm/TOYOTA-REAR-...-/290413682610

but of course I have no idea if any of those will fit. that setup on pirate 4x4 looks a bit more promising, not to mention more appropriate since these GM brakes seem way overkill for rear brakes.

Last edited by twistedsymphony; 09-06-2012 at 10:28 AM.
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Old 09-06-2012, 10:56 AM
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Not to dump, yet yes, it does sound that you might have to go back to drums. I'm guessing one issue is that the rear disc conversion isn't popular enough to have a strong repository of engineering data, specifically for wheel configs. Personally, as I don't have much of a preference for wheels, I guess i'd just do the conversion, then use whatever cheap steel/aluminum wheels worked (preferably factory).
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Old 09-07-2012, 02:01 PM
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So I managed to get a freebie set of Tacoma wheels with tires... way smaller than what my truck is setup but it will get me on the road for the time being.

I'm going to run those while I get my t-case e-brake setup squared away (that's another project as I discovered I have the wrong t-case for the ebrake setup I bought too )

I'm going to source some pathfinder/montero brakes and try the setup from pirate 4x4 in my link above to see if they have any better clearance. if that works then I'll sell the sky brake setup to help recoup my costs.

if THAT fails then I'm going to buy some steel wheels and sell my Mickey Thompsons

and if the new wheels don't work with either brake setup I'm going to set my truck on fire and forget that it ever existed.
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Old 09-14-2012, 01:28 PM
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Really nice write up. Makes me jelly to see those parts come out of the pick n' pull so clean... they look new! No such luck in the midwest
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Old 09-14-2012, 03:14 PM
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thought I'd post a small update... Stock 16" tacoma wheels don't fit either... the offset isn't aggressive enough, so the whole caliper has to fit inside the wheel and the humps toward the back of the caliper scrape....
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