What is the purpose of inboard brakes?

[BlueRooster]

They look cool, but is there a huge benefit?

[Woodz428]

It's primary advantage is moving that mass inward away from the wheel.By reducing the unsprung weight it allows the suspension to operate easier(smoother), they tend to wear pads out quicker because of less airflow and servicing is more difficult.

[Bob In Ct]

Ditto on Woodz428, it's all about "unsprung weight".

Bob

[Tony Radford]

Helps keep brake pad dust off the nice polished wheels.

[Excaliber]

Woodz nailed it. Sprung vs Unsprung weight. The constant suspension engineering "holy grail" is how to reduce the wieght of moving suspension component parts. Turn the shocks upside down! Do like Richard did to the JBL, put the shocks INSIDE the frame so there wieght is totally off the moving suspension parts.

With the Jag setup some people feel that any suspension weight advantage was lost due to over heating the brakes and the diificult servicing factors. I think ERA actually recommends an out board brake modification to the Jag setup for such reasons.

Another way to loose weight on the suspension? Light wheels and tires! BIG advantage here is it's not ONLY suspension weight it's also ROTATING weight! Every pound of rotating weight saved is equal to three pounds of static weight!

Ernie

[Richard Hudgins]

BlueRooster.

In the old days we chased the Unsprung weight quest a long ways.

Inboard brakes were a major part of this effort.

But, we did break a lot of parts. Halfshafts were a constant problem. We used to paint lines on the Halfshafts to measure twist from acceleration loads.

Guess what, braking loads far surpass acceleration loads. The twist was always in the braking direction on inboard brake cars.

To us in the race industry, it all came home with death of Jochen Rindt.

He was driving a Lotus 72 with inboard front brakes at Monza. A front Halfshaft broke under braking and the car turned into the Armco barrier. He did not survive the incident.


After this, as responsible engineers and participants, we looked at the real benefits and found that that there was really no decrease in laps times once we figured out how dampers worked. (This period really brought damper technology along very quickly and is the true mainstay of chassis dynamics today.)

At this point Inboard brakes ceased to be used on real race cars.


Too bad we had to lose one of the best in order for us to look at the reality of design risk and the quest for performance at any cost.

In closing, inboard brakes on a saloon car are just fine. But on a race car they are just plain stupid.

[BlueRooster]

Great answers guys thanks....they are a sight to behold when the body off the chassis though.

[RACER X #99]

The real good thing about inboards is all the fun you have changing pads, especially when you have rear mounted Wilwoods and a Fuel cell only 2 inches behind the Calipers. Bleeding is also a lot of fun especially the inboard side where you can't see the bleeder. Brake fluid running down your arm right into your arm pit. I really look forward to bleeding the rear brakes.

They're may be more than one reason they moved them right up next to the wheels.

Cranky

[Cal Metal]

Richard:

Elaborate on Damper Technology. Thanks.

[Woodz428]

I'm not Richard, but damper technology is one of the major improvements that have taken place the last 30 years. The better matching of compression/extension dampening rates to the springs and the changes made in fluids and circuits in the shock have helped it handle road contours better without elaborate additions such as inboard brakes. It has also allowed softer springs in applications that used to require stiff springs because the dampers can now better control the spring compression. This all adds up to a smoother yet better handling car (and motorcycle for those inclined).

[Richard Hudgins]

Cal,

Damper technology has grown by leaps and bounds since the 70’s.

The most advanced damper available in those days was the Koni double adjustable unit. It had bump and rebound adjustments and a very limited set of valving choices. I think that there was 8 sets of valves available. You had to send them back to Koni to have them changed.

The dampers used until the late 70’s were all double tube type. These were good units but limited as to mounting configuration and had a high tendency toward aeration and fade. They worked best when wheel rates were below 150.

With the advent of serious downforce in the 80’s becoming quite important, wheel rates by necessity had to increase. Also packaging became very important and damper mounting was a major part of this. You had to get them out of the air stream.

This is when the monotube type damper became the standard. This was a gas pressure unit that allowed running the damper in most any mounting position. The design and valving available was greatly expanded and wheel rates above 300 started becoming controllable. These were still the double adjustable type.

In the late 80’s and 90’s, Olins and a few other makers started looking at the telemetry data from the cars and realized that valving was not quite as simple as just worrying about your spring rate and sprung VS Unsprung masses. Shaft velocities and frequencies were way outside of the commonly accepted ranges.

This necessitated a whole different way of dealing with the motions. Damper bodies, internal valving, external rebound cans and low, mid, and high speed reservoirs all became part of the designs and also added complexity to the setup equation.

Dampers today have adjustments available for both rebound and bump just like the old days but with much more control of the motions. Now you can set the bump and rebound rates for low, medium, and high shaft velocities as well as stagger these rates across the range. Valving capability is now virtually unlimited and there are over 200 different oil compounds used to vary characteristics and gas pressures of 1800 psi are common.

Also, no respectable race team goes to the track these days without a damper dyno and a specialist on setting up the damper units. These are specialists that do nothing but damper tuning and most of these guys are MIT grad types that talk in strange tongues about temperature-hysteresis effects, mid shaft frequencies and stutter delay.


If you are really serious these days, you will put your car on a seven post rig and simulate the motions for each track that you visit and preset your chassis settings such as damper rates from the test data that you develop while on the rig. (And still change them once you are at the track to meet surface conditions and driver desires.)

In all honesty, dampers have become so complex that I really do not know very much about them anymore and the my brain is having a hard time keeping up.

[RACER X #99]

Richard
I know you are serious and all that shock tech talk makes sense to real pro racers but most of us Open track Bozos are just trying to keep their car going fast forward with little or no contact with the Armco. I am already past the age of "to old to be out there" but I will keep on trying untill the guys I used to pass start passing me.

What shock advise can you give to hard headed guys who don't want to hear and don't understand the tech talk?

Oh yea I only have $0 to spend.

Thanks,
Cranky

[strictlypersonl]

Originally posted by Excaliber


Woodz nailed it. Sprung vs Unsprung weight. The constant suspension engineering "holy grail" is how to reduce the wieght of moving suspension component parts. Turn the shocks upside down! Do like Richard did to the JBL, put the shocks INSIDE the frame so there wieght is totally off the moving suspension parts.
...

Ernie

For the record, inboard coil-overs do not inherently reduce unsprung weight. They still have to move, and their inertia is part of the sprung weight. In fact, because the control (rocker) arm has to be heavier, the net unsprung weight will probably increase.

Formula cars have their springs and dampers inboard for aerodynamic reasons, and it makes it a bit easier to integrate driver-adjustable anti-sway bars.

[Richard Hudgins]

strictlypersonl said,

"For the record, inboard coil-overs do not inherently reduce unsprung weight. They still have to move, and their inertia is part of the sprung weight. In fact, because the control (rocker) arm has to be heavier, the net unsprung weight will probably increase.

Formula cars have their springs and dampers inboard for aerodynamic reasons, and it makes it a bit easier to integrate driver-adjustable anti-sway bars."

Bob is quite correct.

The only possible reduction is that the damper itself is not part of the Unsprung weight.

The JBL rocker weighs about 4.7 lbs. with the outer rod end. I would think that most upper A-arms are in this same range or lighter.

One of reasons for the rocker system on the JBL is just as Bob stated. Packaging. This arraignment allowed for the anti-roll bar system and its adjusting bits.

The main reason however was motion ratio.

Cranky,

As I stated in my previous post, I really do not know enough about dampers to help you much.

It seems to me that you would be better served by other members of the forum, particularly in the "don't want to hear and don't understand the tech talk" bits.

(Also please note that you have spent your entire damper budget on my consulting fee at this point.)

Now, as to increasing your speed at the Glen.

The only thing that I can think of is to stop using the brakes so much. That is why the ARMCO is there.

As Ettore Bugatti once said "My cars are made to go, not to stop".

He was at the pinnacle of the sport you know.

[Excaliber]

I just bought a Kawasaki KLR250, on/off road. Been a LONG time since I was on a modern off road bike.

My how suspension has changed over the years! It just soaks up the rocks and bumps on the trails.

Kind of like the difference in the old skate boards I used in the mid 60's. Metal wheels attached to little more than a skinny board, and the motorcycles of that time were not much better!

Ernie

[KobraKarl]

Richard/Woods......

Good stuff, even if I only get 1/2 of it ....

KK

[Fullchat289]

Originally posted by Richard Hudgins


As Ettore Bugatti once said "My cars are made to go, not to stop".

[/b]

I've been telling people Enzo Ferrari said that..... I think Ettore was much too concious about the engineering that went into his creations to have said something like that. You sure???

[Richard Hudgins]

Fullchat289,

No I am not sure of this quote. I pulled it up from some dim memories.

But as a reference check:

Quotes1

Quotes2

However, these are not to be considered as proof examples.

Enzo Ferrari could certainly of said this as he was one of the last to go to disc brakes and was notoriously stubborn.

[Fullchat289]

Richard:

Thanks for posting the links. I like the other Enzo comment too regarding aerodynamics.

Sorry to de-rail.....back to inboard brakes.

[SPEEDEAMON]

Here's an early application of in-board drum brakes by the Mercedes GP team of 1954 and 1955. The car is a W196 driven by Fangio, Hermann, Kling and Moss. Both open wheeled and streamliner versions (300SLR) employed these in-board drum brakes which were turbo-cooled (finned drums). just FYI

Shin