Caliper placement 2

[BrianGar]

Something Ive always wondered about but never got around to actually talking about it.
Some manufacturers place them to the rear of the hub/disc, others place them in front of the hub/disc.
What are the effects of either position?
Off the top of my head
1, positioning space comes to mind
2, weight offset in respect to other suspension components
3, hub design and force directions, for example, a caliper in front would have a tendency to try and force disc and bearing upwards(climb) in the hub as the pads try and stop rotation.

Anyone have any other views or wish to discuss?

Brian.

 

[patprimmer]

Some Porsche models might be exceptions to the front brakes always hotter rule, maybe?

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[chammyman]

I concur, pretty much anything new on cars citroen done sometimes well years ago. The first decent fwd car was the Traction Avant, beating the mini by 13 or so years if I recall correctly.

Sadly since the PSA group took over Citroen became a shadow of their former selves. They are just Peugeots now and I don't like Peugeots, although some are easy money spinners for poor design faults.

As for Porsches, the rule of front hotter still applies, weight transfer still occurs but I see your thinking. But you would be right in assuming the temps are closer end to end than say a fwd's. Thankfully these days they don't like to swap ends as easily but if you provoke them they will spin.

You have to admire their persistence in engineering a wrong design right, or at least trying to

 

[thundair]

I always thought you could increase braking by using something similar to a clutch pack with carbon/carbon and actuate it with a hydraulic clutch ring. I know there would be release problems and such, but nothing unsolvable, with no need to hang a caliper.

We went through this when they started hanging big Lockheed calipers on the Norton motorcycle,and one of the things we looked at was the polar moment on the steering axis. I don't know if that is a consideration on a car or not, but that seem it would put them on the top or bottom.

Cheers

I don't know anything but the people that do.

 

[izzmus]

chammyman - all Mazda RX-7 had rear mounted calipers in the front, but the first generation (models before MY1986) had rear-steer recirc-ball steering. The engine is too wide and low to fit a rack beneath it, and most of the front suspension is carryover from sedan models. Presumably, they didn't want to spend much money on the car.

Now that I think of it, the earlier models may also be rear steer/rear caliper, but I'm unfamiliar with them.

 

[RossABQ]

I recall an article in the SAE Journal back in the '80's when I belonged that had an in-depth analysis of the forces with 3-o'clock and 9-o'clock calipers (I think on a MacPherson suspension specifically). There was an advantage to one or the other, but not huge. No longer a member so I can't search their archives.

 

[thruthefence]

Didn't Chrysler have an option fro a multi disc/stationary disc "something similar to a clutch pack" on their cars back in the early '50's?

 

[BrianGar]

@Ross, was bearing loading the issue? Or can you remember?
Thanks to all for the replys, youve all answered many of my questions.
Brian.

 

[RossABQ]

I honestly don't remember, sorry Brian

 

[kellnerp]

I always thought you could increase braking by using something similar to a clutch pack with carbon/carbon and actuate it with a hydraulic clutch ring. I know there would be release problems and such, but nothing unsolvable, with no need to hang a caliper.

Most airplane brakes are like this. Four, five or six cylinders, a hollow tube with spines for the stationary disks and bolt on splines inside the wheel.

Aircraft have several criteria that automobiles don't have. One is an aborted takeoff in which case the brake is designed to become incandescent with out self destructing till after the aircraft is stopped. Another is a landing with a full load. Another is parking after a hot landing without the metal softening with a loss of pedal. Because aircraft brakes don't have to dissipate heat and drop down in temperature immediately after a stop they can be designed like this. But a "clutch" like brake would not dissipate heat well for automotive because the braking material is compact with little room for circulation and convective heat transfer.



TOP
CSWP, BSSE

http://www.engtran.com

http://www.niswug.org

"Node news is good news."

 

[thruthefence]

probably why we don't see them on cars - also they make a terrible rattling noise when the wheel rolls.

 

[thundair]

I was hoping the carbon carbon would handle the heat but you are right about the noise as my Ducati makes more clutch noise in the mornings then the exhaust.

Well....I didn't mean to high jack this thread with my interjection.



I don't know anything but the people that do.

 

[patprimmer]

Automatic transmissions seem to operate without waking the dead, but they do have the ATF to cool them and damp any noise. I thought motor bike clutches were mainly multi plate wet clutches like an automatic.

I think it would be extremely heavy and quite expensive to build a multi stack fluid cooled brake system.

Without the fluid a multi stack will take to long to cool between applications.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[chammyman]

izzmus gen 1 rx7's did indeed have recirc ball steering but they had front mounted calipers, the later gens had rear mounted calipers and track arms that went overt he wishbone to the front of the hub carrier. So again we are waiting for a car with rear calipers and rear track arm mounts.

 

[izzmus]

Speaking as someone who has owned, modified, and raced them since 1998, as well as running up approximately 25,000 miles per year driving them daily and performing all of the regular maintenance that ensues from it - they are definitely rear mounted. The easiest way to unbolt the calipers is to first unbolt the strut/spindle housing from the steering arm to get it out of the way.

Of course, you don't have to take my word for it, when there are images available -

http://c4.ac-images.myspacecdn.com/images01/52/l_b676217ddb6563e3652faf7e2f51b923.jpg

details just how cramped it is there. As well as the lengths one will go to in the quest to save money on dampers...

 

[BrianGar]

Damn that is tight!

 

[IceStationZebra]

"I always thought you could increase braking by using something similar to a clutch pack with carbon/carbon and actuate it with a hydraulic clutch ring. I know there would be release problems and such, but nothing unsolvable, with no need to hang a caliper."
"Most airplane brakes are like this. Four, five or six cylinders, a hollow tube with spines for the stationary disks and bolt on splines inside the wheel."

Many off-road vehicles use inboard multi-disc wet brakes. Many of them are spring applied and hydraulically released, this way if the hydraulics go out the vehicle comes to a stop.

ISZ