inboard brake pros vs cons

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richardcraineum
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inboard brake pros vs cons

Post by richardcraineum » Sun Nov 05, 2017 1:37 pm

thought I'd see what ppl's thoughts on running inboard brakes are? obviously there's less unsprung weight, but wouldn't there we more wear on cv's? and if a cv breaks you have no brakes to that wheel.
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Ol'fogasaurus
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Re: inboard brake pros vs cons

Post by Ol'fogasaurus » Sun Nov 05, 2017 2:25 pm

We had a discussion on this a while back. My memory says that the DOT may have limitations on this but, like you said, there have been cars brought in that way. E-brakes still have to be mechanical and outboard in case there is a half shaft or CV failure. The same with the brakes when one side disabled as the vehicle could pull to one side uncontrollable. Some trucks had driveshaft E-brakes which comes with a safety issue.

Less unstrung to the outboard sides but not necessarily overall.

An interesting discussion for sure.

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ChadH
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Re: inboard brake pros vs cons

Post by ChadH » Mon Nov 06, 2017 1:07 pm

A random B.S. thought - I don't know if it would really be an issue or not..

With outboard brakes, the brake is attached directly to the wheel, so brake modulation is immediate.

With an inboard brake, the braking forces would have to be transmitted through the axles, and there would be a torsional twist involved, before the force slows the wheel. This might take away from the immediacy of braking feel - and maybe even make modulation difficult, since the driveshaft would be subtly twisting and untwisting. Maybe even some sort of bad resonance or chatter would happen under heavy braking? Beat up CV joints?

I know old Jags had inboard brakes, but they used U-joints and pretty stout looking axles.
Last edited by ChadH on Mon Nov 06, 2017 1:23 pm, edited 1 time in total.

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Re: inboard brake pros vs cons

Post by Ol'fogasaurus » Mon Nov 06, 2017 1:20 pm

Chad, what you say is true. Axles, you could say, act similar to torsion bars in a way ("axle wrap"): if you were to park on a hill, for example, and used the parking brake located on the inside of the axle (or driveshaft like some trucks had), put it in gear/park, then let off on the parking brake there would be some travel (fore or aft depending on whether you were parking nose facing up hill or down hill) due to axle twisting until the axle loading stopped.

One of those silly (but important) little things you either forgot or don't think about.
Lee

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richardcraineum
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Re: inboard brake pros vs cons

Post by richardcraineum » Mon Nov 06, 2017 6:47 pm

all that makes sense and the little play in each part could compound and it be kinda like putting an automatic in park where u get a little bit of roll. now I know this wouldn't apply to our buggy stuff but I've read that on the 2.5 and 5 ton military axles with the brakes on the pinion, that the braking is multiplied by the gear reduction of the ring and pinion ( just something I always thought was cool )
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ChadH
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Re: inboard brake pros vs cons

Post by ChadH » Mon Nov 06, 2017 7:03 pm

On a long travel buggy or Baja, the effect of twist could even be worse. Not only are the axles longer, but their purposefully sized to twist and absorb shock to the drivetrain. From the Sway-Away site: "..the axle diameter is sized to twist like a torsion bar under heavy loads absorbing a large portion of the shock transmitted from the wheel into the gearbox."

However, maybe in a light sand car it wouldn't be that big of a deal. I was originally thinking a road car, with sticky tires, where braking needs to be precise and smoothness through the drivetrain is more important.

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Re: inboard brake pros vs cons

Post by Ol'fogasaurus » Mon Nov 06, 2017 8:05 pm

It is surprising on how much of that torsion effect is going on even with a stocker. You drive around in heavy traffic on and off the gas, you hit joints in the road as well as runts, puddles and curbs (parking or driving over them) not to mention the little "turtles" for lane markers or the monster turtles used for turning lanes.

Think of the torsioning loads that are applied at launch and hard shifting drag racing. The up and down shifting, the curbs (if that is what the called the white painted with red stripes that every one drives over to cut the corners) same with road racing and maybe even autocross. If you watch the hill climbers and the loading of things as they bounce around going over rocks and other obstacles' as well as landing under power from one hillock to a low spot. Sand can be hard on them assuming you are jumping (I never do that :roll: ) but not as bad as some other sports I would suspect. I couldn't afford those other sports (plus the misses wasn't into motorsports and was in control). :oops:

Also the U-joints and CVs are probably taking the same amount of abuse if not more.

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Re: inboard brake pros vs cons

Post by sideshow » Mon Nov 06, 2017 8:43 pm

I can't image that inboard couldn't be not street legal, Audi 100 were legal and Hummer/H1s have been plated.
I however am not sure what you are trying to accomplish.
Yeah some may call it overkill, but you can't have too much overkill.

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Re: inboard brake pros vs cons

Post by Jadewombat » Mon Nov 06, 2017 9:37 pm

I've never heard of inboard being illegal or special permissions needed. Both Jaguar and Alfa Romeo had them for a while at different times. For as narrow a rear end as the bug is, I don't think there would be too much slop or delay in transfer of energy through axles.

It's an idea that's been kicked around, but hasn't been tried (as far as I know) on a bug. Go for it. Just do the CV test before. Grad each axle and go side-side. More than 1/2" of play and they probably need to be replaced.

I'm not condoning bad braking, but I've had (as we all had at one point in time or another) a wheel cylinder blow out. You can still stop the car though. It sucks, but I think the benefits of mounting everything closer to the CoG outweigh the small increased risk something bad would happen. You'd have to have some serious hp and be doing a lot of heel-toe to break a CV I would think.

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Re: inboard brake pros vs cons

Post by Ol'fogasaurus » Mon Nov 06, 2017 11:40 pm

sideshow wrote:
Mon Nov 06, 2017 8:43 pm
I can't image that inboard couldn't be not street legal, Audi 100 were legal and Hummer/H1s have been plated.
I however am not sure what you are trying to accomplish.
There are several inboard brake cars like the Jag that were brought in but if I remember they were either banned or the idea was broached. I tried to search for it but what you get is so convoluted it is hard to figure it out.

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ChadH
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Re: inboard brake pros vs cons

Post by ChadH » Tue Nov 07, 2017 10:36 am

I did find this:

Image

https://www.thesamba.com/vw/forum/viewt ... c&start=40

This is a 100% show car though - so I doubt the car has ever been road tested, other than to be pushed by hand from the trailer to the parking lot. (FWIW - I remember seeing this car in Hot VW's back in the '80's)

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Re: inboard brake pros vs cons

Post by Ol'fogasaurus » Tue Nov 07, 2017 10:56 am

Yeah, there have been some fantastic things done with show cars but are they streetable and/or safe :roll: :wink: . A lot of the time there is so much "monkey motion" in their suspension or other systems it is hard to follow what all has been done and how it works.

I forget the term used for this kind of build, not a derogatory but more of a showy term. I also remember of their be Allison aircraft or helicopter engine being stuck in a Fiat or one of those overly small cars at one time.

I did a search on Allison engine builds and they are still doing them.

richardcraineum
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Re: inboard brake pros vs cons

Post by richardcraineum » Thu Nov 09, 2017 7:19 pm

I looove the looks of a cantilever set up! anyone ever seen a functional one on long or mid travel set up? read they can be hell to tune (not to highjack the inboard brake topic )
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