Inboard disk brakes?

[jpryorx2]

good point on the wheel cylinder i guess i didn't look at it that way. i do mainly offroad driving in my sandrail which i have broken a few with no warning but i'm also only running stock vw cv's

[dd-ardvark]

Hello guy's, to your question with regards to Inboard Rear Brakes and whether I've used them.
No is the answer.

But I presented a similar question back in 2006 on Germanlook.com under "Inboard Rear Disc Brakes - Plausibility",
and the response that I got made me look in a different venue and I found the answer I was searching for
under a transmission company.

http://www.transworks.biz/ had this question posted to them and they came up with a novel answer for
both the bearing and seal wear, this along with hanging a rotor and caliper in close proximity to the transmission.
Read this article on machining the side covers for a additional bearing under the title, "Flange Bearing Retainer".
http://www.transworks.biz/TWP.html


This isn't cheap but If your want to build this once instead of twice..., spend the money and don't look back.

Myself, I never prosued this avenue for my brake issue, but here's the link for you.

http://www.transworks.biz/brakes1.jpg

dd-ardvark / David

[Jadewombat]

In case you're going to use a radial or tank engine on your VW. Old Pullman train cars used to use inboard ventilated disks.

[Ol'fogasaurus]

For an on road car, as I remember, DOT would still require a mechanical e-brake on an outside wheel for the reason jpryorx2 stated (the hydraulic park lock brake does not qualify as a street legal e-brake). Off-road only is (probably) a different matter unless where you would be riding is controlled by the feds then I don't know what, if anything, would be required but I would suspect DOT compliance would then be in effect. Where I ride they will sometime check a lot of things if license plates are on the vehicle; as that puts them into a different category. One of the reasons I took my plates off.

[Piledriver]

I have seen several mechanical disc ebrakes on the inner CV, Texas law requires that it is functional* to the point it keeps the car from moving while powered in gear. (4th will do, an auto needs to blip the throttle in gear to demonstrate function)

The factory parking brakes are kinds iffy IMHO, the mech parking brake Mk4 calipers I have out back have amazing grip and will prevent almost any motion, in first, floored, dropping the clutch at 5K.


*probably still prohibits a line-lok somewhere down deep in the regs.

[Ol'fogasaurus]

Again, if there is a break in the half-shaft or the outer CV then inboard e-brakes on that side are of no use; you do have a viable half of a turning brake though. On the race track then most likely you'd be OK with inboard e-brakes but on the road is a different matter.

Each state is different in their regs which is one reason there is a DOT... to set a minimum standard. Mechanical brakes may not be the best but they are, for the most part, consistent assuming that the rest of the system is correct but this would also be true with inboard brakes too.

If you live in hilly country like we do up here on the left coast you really need something you can depend on. From personal experience the line lock style of e-brake can either jam (happened numerous times) the rear brakes in a locked position to where you have to open a bleed valve to set them free or your car rolls down the hill (I still carry body damage from one of those times) as soon as you get out and lock the door. While I am sure that engineering could come up with something better so that will not have problems with air getting into the system allowing the brakes to fail or will do the lock up bit but would it be that way when amateurs get into the mix (granted: they can screw up anything so the argument is lame but I think good enough to get the point across).

If you live in flat country then, while probably not legal, the putting the car in park is probably good enough unless someone doing the touch tap method of parking hits you hard enough to knock the lock device out of the trans (automatic). I've known people (and these were adults) who rely on putting the trans in park even here in hilly country but then you need a friend with matching bumper height to slightly move you to allow you to get the shifter to move the trans out of park . Seen it done dude and not just once!

[sideshow]

Why would it not be legal? Audi 100 and Jag come to mind (http://en.wikipedia.org/wiki/Inboard_brake), and it was once common to run drum brakes on the driveshafts of trucks. I don't get where this wheel centric restriction comes from.

[Ol'fogasaurus]

Just what I was told when I looked into it years ago when the subject came up somewhere else.

[Piledriver]

If you have a simultaneous axle and brake failure you probably just wiped the suspension/wheel off on a tree.
I doubt it ever crossed their minds as a scenario for requiring a particular braking configuration...

[Ol'fogasaurus]

I got thinking about it again and this is what I came up with:

There are debatable questions that usually elicit debatable answers with not all being right or not all being wrong. It's kind of like the Quaife discussion going on: There are times when a diff-locker of some type is good and others when it is definitely not; the same with this.

Moving the brakes inboard changes sprung weight balance at least some which can be good or bad. Is the weight change enough to cause under-steer and if so can that be jacked to change the weight bias to some over-steer.

If I break an axle and not realize it will it cause me to take a hard detour towards the still good axle when I hit the brakes or not. The same with a live axle (welded spiders or a spool) where when the axle breaks under load you take a side trip in the direction of the broken axle.

Are there times when a posi is not needed or wanted if I have one installed.

As you know in off-roading a posi is good or bad but you can, by using the foot brake lightly or using the dual handles of the turning brakes make the diff work to drive both wheels rather than just the one with the least traction. You can also, by using dual handles change braking bias from wheel to make that one or the other one be the driving wheel as needed (that ability saved my bacon once when a sand dune collapsed causing a sand slide as I was driving up it).

I am sure that there are times when having the brakes inboard is good or can be bad. I also know that they have been playing with inboard braking systems since at least the early 50's and they seem to be in or out as fancy changes.

Ignoring the DOT post, I still think that inboard brakes can be more of a liability that outboard brakes even on the track but I still think this is one of those questions that is as debatable as the answers and probably no one answer is correct.

[Jadewombat]

It's pretty unlikely that you'd have a complete failure of all six CV bolts instantaneously shearing through with no warning, unless you're in an offroad race and hit a rock or something. We've all had the all too familiar wheel cylinder failure at one wheel. What happens? Car pulls to one side and catches you by surprise. That's it. I never crashed my bug when this happened.

[Ol'fogasaurus]

I lost 4 at bolts within a half mile driving on asphalt and a quarter mile of sand at one time before the CV came off the transaxle hub. The torque specs in some books say 25#s while others say 32#s. I now go with 32#s.

You can destroy at stock CBs, excluding the bolts backing out, by hammering on/shocking them which some forms of racing can do. Think about it: a hard launch/start then going up and down the gears for hours does put a load on the CV components, half-shafts, stub axles and the nut that holds the brake on if the brakes are outboard. Race CBs (not talking about race prepping CBs now) I don't know about them or if they even exist so I can't speak to them.

Again, we are at the debatable/what if part of a discussion.

[Jadewombat]

Agreed.

Do you wire-tie your bolt heads?

[Ol'fogasaurus]

No! I'm still using the stock style of bolts which wouldn't work well with "lacing" them in. To be honest, I never thought about or heard of anyone changing over the bolts but at first look it could be a great idea as long as the free end of the wire doesn't stand up and snag the boots .

Lee

[Piledriver]

You can get drilled socket head cap screws as well.
Not sure of the grade the factory used, suspect M10.9 or 12.9 they are good bolts.

I'd be far more inclined to use locktite.