XJ Front Brakes, BIG Brake Options

[bpas328xii]

How are you going to retrofit the 8.25 axle for ABS?

I could've sworn that someone swapped the 8.25 into a d35 ABS Cherokee and adapted the ABS to work... I honestly haven't looked into it in great detail yet. Still have to gather the parts from the junkyard and start playing with it.

They do actually make ABS tone rings for the 8.25, so.... It might not be a difficult swap. Lol.

 

[Talyn]

I could've sworn that someone swapped the 8.25 into a d35 ABS Cherokee and adapted the ABS to work... I honestly haven't looked into it in great detail yet.

Some has. Not sure who though. :eeks1:

They do actually make ABS tone rings for the 8.25, so.... It might not be a difficult swap. Lol.

They make 'a' tone ring for the 8.25 axle... it goes between the ring read and carrier. The XJ 8.25 is not machined for the sensor on the housing. There is no way a tone ring would fit directly on the XJ 8.25 axle shaft though.

 

[bpas328xii]

Some has. Not sure who though. :eeks1:

Hmm..... I wonder who did the conversion and posted info about it..

They make 'a' tone ring for the 8.25 axle... it goes between the ring read and carrier. The XJ 8.25 is not machined for the sensor on the housing. There is no way a tone ring would fit directly on the XJ 8.25 axle shaft though.

Like I said. I haven't looked into it in great depth. I'll definitely use your thread for info.

 

[moparmansfield]

Why is everyone hating on this project? Guy is sharing his R&D and he's open to peoples opinions, for a possible upgrade we could all(the majority) gain from. Adding to un-sprung weight? really? its a jeep Cherokee.. gimme a break.

O.P , looking forward to seeing where this goes and your testing. Would be a great upgrade that most of us would appreciate.

 

[kastein]

I'm not sure why you want to add ABS but it is possible if you know how to wire things properly.

And yes, ABS did come on 8.25s in the Liberty, Durango, Dakota (iirc), and several other C/J/D vehicles. But as someone noted it is a single tone wheel at the ring gear, at least on Durangos it's machined into the lip of the ring gear carrier flange. I am unsure about tooth count but it is most likely 108 teeth instead of the 54 I'm fairly certain XJs use, so you can't just splice both rear wheel sensor signals from the ABS HCU into it, you're going to need at the very least a PLL circuit and probably a lot more than that (possibly including DDS chips and a microcontroller, DSP, or FPGA) to convert the signal in any way I'd expect to work, depending on how smart the ABS HCU is.

Also, the XJ 8.25 center casting has the bosses for the ABS pickup, but they aren't machined out, so you're going to need to measure angles/positions relative to some sort of datum point (probably the centerline of the carrier bearings), find a machine shop that will work on a rusty ass 5 foot long oddly shaped bit of metal, and have them machine a few faces flat, bore a hole, and drill/tap a few mounting bolt holes in the center casting. It's probably not worth doing. As I recall people have put ABS on 8.25s but it focused on swapping ABS backing plates from a d35 out of an ABS vehicle and having the shaft shoulders and tone rings custom machined to fit properly. I'm not entirely sure on that, I may be thinking of the XJ D44 ABS swap someone (Talyn?) did.

Basically: you are in for a lot of pain if you try and do this. Either custom machining or custom electronics or both.

 

[Talyn]

Like I said. I haven't looked into it in great depth. I'll definitely use your thread for info.

LOL.

. Adding to un-sprung weight? really? its a jeep Cherokee.. gimme a break.

Its also a "racejeep", so weight should be a concern.

I am unsure about tooth count but it is most likely 108 teeth instead of the 54 I'm fairly certain XJs use, so you can't just splice both rear wheel sensor signals from the ABS HCU into it, you're going to need at the very least a PLL circuit and probably a lot more than that (possibly including DDS chips and a microcontroller, DSP, or FPGA) to convert the signal in any way I'd expect to work, depending on how smart the ABS HCU is.

A brief look at the Durango tone wheel looks like it has a very low tooth count for the diameter. Being a Chrysler product I wouldn't doubt that it is has the same tooth count as the smaller XJ tone wheels. However I don't know how the ABS unit would interpret it if you just spliced the two rear sensors together. The XJ does have an ABS sensor for each rear wheel, but only one brake line for the rear so it isn't that smart.

Also, the XJ 8.25 center casting has the bosses for the ABS pickup, but they aren't machined out,

That is correct

As I recall people have put ABS on 8.25s but it focused on swapping ABS backing plates from a d35 out of an ABS vehicle and having the shaft shoulders and tone rings custom machined to fit properly. I'm not entirely sure on that, I may be thinking of the XJ D44 ABS swap someone (Talyn?) did.

ABS swap on a D44 is easier because there is enough axle shaft sticking out of the axle tube to put a tone ring on. On the 8.25 there isn't enough room on the shaft to put a tone directly on the shaft. The back of the axle flange must be used instead with a cylindrical spacer of sorts.

 

[urban yan]

Why is everyone hating on this project? Guy is sharing his R&D and he's open to peoples opinions, for a possible upgrade we could all(the majority) gain from.

Actually, the ones of us that have issue with his projects do so specifically because he is NOT open to people's opinions.

Adding to un-sprung weight? really? its a jeep Cherokee.. gimme a break.

So what? Just because our Jeeps came from the factory with some draw backs is that a legitimate excuse to expand upon those draw-backs with each successive mod?

O.P , looking forward to seeing where this goes and your testing. Would be a great upgrade that most of us would appreciate.

How so? His son admitted that this kit will not be for the public - just for his race Jeep. Secondly, that 14" rotor won't clear the vast majority of our wheels, so it’s not an upgrade most of us can appreciate or use.

 

[kastein]

A brief look at the Durango tone wheel looks like it has a very low tooth count for the diameter. Being a Chrysler product I wouldn't doubt that it is has the same tooth count as the smaller XJ tone wheels. However I don't know how the ABS unit would interpret it if you just spliced the two rear sensors together. The XJ does have an ABS sensor for each rear wheel, but only one brake line for the rear so it isn't that smart.

I may be wrong - it's happened before, frequently in fact. I have a Durango LSD sitting in my parts bin at work waiting to be installed in my XJ at some point, so if someone bumps this thread tomorrow I'll go count the teeth on the ring gear mounting flange.

I doubt it'd be a problem as long as you match polarity i.e. there are striped and non striped wires on the signal line to the ABS HCU. One is likely either grounded or linked to a supply voltage rail internal to the ABS HCU, the other is the signal wire to the AFE. Assuming it's a similar AFE to the LM1815 I've used on similar projects, it'll handle being in parallel with another input no problem.

The other option if it does turn out to be a 108 tooth wheel is to simply grind every other tooth off. Not sure it'll work, and it's pretty ghetto, but it's worth a try, Durango 8.25 LSDs are like 40 bucks each at the JY near me and they're rarely worn all that badly, being giant bloated grocery getters that rarely actually see anything over quarter throttle except in a straight line. Worst case it doesn't work and you don't have ABS, but you still ended up with an LSD.

 

[rockclimber]

I am going to preface this by saying I am not defending cobramarty's kit. I still haven't made up my mind on it, I'd like to see some real world testing done.

I'm not really crazy about the bracket only attaching to those 2 lugs, and for me, a BBK from black magic is just too easy of a kit to ever bother doing something like this.

So what? Just because our Jeeps came from the factory with some draw backs is that a legitimate excuse to expand upon those draw-backs with each successive mod?

any brake upgrade you do is going to add weight. some more, some less.

the key is to balance that added weight with added braking performance which by the looks of what he has will not be difficult.

How so? His son admitted that this kit will not be for the public - just for his race Jeep.

except he showed you exactly what you need to do to put the kit together yourself.

Secondly, that 14" rotor won't clear the vast majority of our wheels, so it’s not an upgrade most of us can appreciate or use.

that is a line of bullshit if I ever heard one. there are so many wheel setups out there, and the amount of people going to 17" rims is pretty high. it would not be unreasonable at all for someone to get different wheels to run this brake setup.

 

[Demonoid369]

I have a Durango LSD sitting in my parts bin at work waiting to be installed in my XJ at some point,

Not meaning to hijack but hey here's that bump you were talking about lol
Got any comments on the Durango LSD? Better than the xj's LSD? Or is it just easier getting the Durango? There's plenty of them near me and didnt know they had LSD. Been wanting rebuild/mod my factory xj LSD.

 

[urban yan]

that is a line of bullshit if I ever heard one. there are so many wheel setups out there, and the amount of people going to 17" rims is pretty high. it would not be unreasonable at all for someone to get different wheels to run this brake setup.

Bullshit huh? OK, what percentage of XJ owners run 17s? Moreso, will this kit even clear 17s because this looks like an 18" wheel kit ever since he upgraded to a 14” rotor. As someone running 18" wheels I can tell you the only Bullshit is finding a good set of tires for that wheel size. In fact, I'm contemplating going down a size, AND I can do that because my 300mm kit clears most anything.

I would stick with a 12" rotor for that caliper, and I certainly wouldn't exceed 13" rotors so everything clears 17s.

 

[cdawall]

For a race jeep 17 and 18 rims probably have plenty of tires and for wheeling 17" is getting to the poiint were it has the best selection of tires and rims.

 

[CobraMarty]

I originally was going to use the 13.25" rotors that I have. I have already made the mock-up brackets for using 13.25" rotors but I am also making a second set of BigBrakes using the 14" rotors which I found (I have to stop 'surfing' the net) for a reasonable price (if they were $500 like 15" rotors, forget it, even $300pr for 14" OEM rotors forget it). I have shown here what I am doing, both for 13.25" rotors and 14" rotors with the same caliper just different adapter brackets. I am making what I want to make, what has not been done before. It is nearly the same amount of work to upgrade to 12" WJ rotors and brakes as it is to go with 13 or 14" rotors and calipers. If I had 20" wheels on 'racejeep' I would probable look for 15" rotors (reasonably priced of course) just because, but I don't, so I won't. Do I need a BBK? IDK. When I drive the Vette, Mercedes or BMW and they stop very well compared to the XJs, Why can't I try and make our play toy XJs do the same. I have less than $500 in all the parts to make 2 sets of BBKs, one 13.25" and the other 14" rotors.

I picked Mustang parts because it's new parts are reasonably priced, 5 mile take-offs are a great deal and used parts are everywhere and nearly as cheap as XJ parts. They only made like a million of them.

Stop hating. Enjoy your stock 11" front brakes if you got them, Nice upgrade to 12" of whatever make if you did that, and here is something else more different, 13.25" rotors (which 13" upgrade BBKs are already out there, $1500+, no thank you) and 14" rotors upgrade BBK to show about the maximum that can be done.

Snow expected tonight , fun wheeling tomorrow.

 

[Talyn]

The other option if it does turn out to be a 108 tooth wheel is to simply grind every other tooth off.

For some reason this rings a bell for me... someone may have done that in the past...

 

[kastein]

Not meaning to hijack but hey here's that bump you were talking about lol
Got any comments on the Durango LSD? Better than the xj's LSD? Or is it just easier getting the Durango? There's plenty of them near me and didnt know they had LSD. Been wanting rebuild/mod my factory xj LSD.

It's really greasy, I'll check it right after work.

The Durango LSD is quite literally exactly the same as an XJ LSD, it's the same axle, same everything except axleshafts, housing, and gear ratio. Same story for the Dakota LSD, but they're harder to find in good condition. The only difference is that there's an ABS reluctor wheel machined into the edge of the ring gear flange.

Both those vehicles come with either a 9.25 or an 8.25 depending on year and options. I've found that most of the Durangos with 8.25s have LSDs in them, at least in the northeast.

For some reason this rings a bell for me... someone may have done that in the past...

I believe it was done by someone swapping an 8.8 into a jeep with ABS, but yes, that same fuzzy memory is what gave me the idea. I should have mentioned that. 8.8s have the same single carrier flange mounted ABS sensor setup, I can't remember what their tooth count is.

 

[Talyn]

I believe it was done by someone swapping an 8.8 into a jeep with ABS, but yes, that same fuzzy memory is what gave me the idea. I should have mentioned that. 8.8s have the same single carrier flange mounted ABS sensor setup, I can't remember what their tooth count is.

After a quick search it looks like the 8.25's tone ring is 104 teeth.

 

[kastein]

You're correct. I just got out of a transmission redesign meeting and had to pull the thing out of my storage bin to measure the spider gears (we might use them in the design, the only thing better than a manufacturers parts bin is someone else's parts bin that is even bigger and higher sales volume) so I counted the teeth at the same time*. I'm guessing the front wheel reluctor rings are actually 52 teeth, then? They usually set things up that way to make the ABS HCU logic easier.

* (this is why I love my job)

 

[yossarian19]

What do you do for work, Kastein? You hint at awesomeness.

 

[kastein]

I'm an embedded systems engineer at a company building a road-driveable airplane in the LSA (light sport aircraft) classification. I also do basic drivetrain design/analysis/parts sourcing when needed, generally only to the "I bet we can find this part on that donor vehicle, let me look it up real quick and see if I can come up with something that works" or "this design seems week, it smells funny to me, that gear is probably not strong enough" level.

 

[bpas328xii]

I'm an embedded systems engineer at a company building a road-driveable airplane in the LSA (light sport aircraft) classification.

Now THAT'S cool!!




Just an FYI. Idk if I said this before, but I'm putting 13" brakes on my lifted Sprintex XJ. Hopefully they fit in the 15" rims. I'd really hate/have zero desire to have to go to a 16" rim and have to get new tires. The 32s I'm on now should last until I decide to go to 35s or 37s... And then that'll open a whole new can of worms.. XD