Caliper placement
Caliper placement
(OP)
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.
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.
RE: Caliper placement
Cheers
Greg Locock
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RE: Caliper placement
You would not suggest that there is more room for the steering arm and caliper if they are on opposite sides of the axle are you
Regards
Pat
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RE: Caliper placement
If nothing else the poor old outer tie rod's grease would melt.
Cheers
Greg Locock
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RE: Caliper placement
Is that the only reason or am I over thinking this?
Thanks.
RE: Caliper placement
I did see something convincing as to why 12 o'clock would be a bad thing other than packaging, but can't remember the story.
So it would be interesting if you can find any examples, but even then we wouldn't know why they did it that way.
Cheers
Greg Locock
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RE: Caliper placement
But then, the simplest explanation is usually the most likely. Most vehicles use the advantages of front steer which leaves the rear of the rotor open for a caliper.
RE: Caliper placement
If there is a modern transverse-engine front-drive vehicle that has it otherwise, I haven't seen it.
If you go back to the 1930's, you can find examples of front-drive vehicles that had the powertrain behind the front-wheel axis (example: Cord), and Saab and Renault have had some oddball front-drive layouts in later years, but have long since reverted to the norm.
RE: Caliper placement
Thanks to all for the above reply s.
Brian.
RE: Caliper placement
Brian Bobyk - Hoerbiger Canada
RE: Caliper placement
TOP
CSWP, BSSE
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RE: Caliper placement
htt
There were exceptions, like ROKON, but they ignored any number of "rules"
http://rokonworld.com/brochures/c5.jpg
RE: Caliper placement
Still Item #1. One might think that toe control links for independent rear suspensions and shocks and trailing lower links for stick axles should get first crack at available space.
Norm
RE: Caliper placement
As for the rear, on my C5, the uprights are common on diagonal corners so the front design dictated the position of the rear caliper.
On a lot of other cars, it seems they are just put opposite of the fronts. Around here, it seems a lot of cars have front calipers to the back side of the rotor and rear calipers to the front side of the rotor. The ones with front calipers to the front of the rotor have the rears to the back of the rotor. Aesthetics?
RE: Caliper placement
I've never heard of tie rod problems, brake heat related or no, but servicing the brakes is difficult because of the location of the steering arm.
RE: Caliper placement
Regards
Pat
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RE: Caliper placement
Pat anyway evidence to back this up? You'd need to do some extensive testing with a moveable caliper to get any worthwhile evidence. Not saying your right or wrong just interested to see if there have been any studies/experiments on it.
As for vertical force exerted by the hub on the bearing, i.e. climbing in the 3 o'clock position, some could argue that the disc will try and pivot from the pad contact area, however thats another argument!
As far as I know front or rear placement is due to the steering arm placement, as has already been said.
BrianPeterson summed up very well the fwd caliper placement.
Cooling can be created quite easily, via ducting, wheel tub design and to an extent wheel design.
Placement other than 9 or 3 (roughly positions) like 12 or 6 is pretty much unheard of. 12 o'clock there will be interference issues with the struts or wishbones, also some would argue that more weight higher up will have a negative effect on handling but tbh it wouldn't be that much of an issue unless its a heavy cast iron component.
6 o'clock, interference with lower wishbones, more exposed to damage from debris, water ingress and so on, but ideal placement for the weight purists, but not practical.
Ideal position of course would be inboard, reducing unsprung mass greatly, but its poor for cooling, maintenance etc. Anyone who has worked on certain Jag's and Alfa's and some other euro stuff will know what I mean.
RE: Caliper placement
Problem with inboard is a drive shaft or CV failure is also a brake failure.
Also braking forces are applied to CVs and drive shafts.
My evidence of rears not being so hot are unscientific and varied ans sometimes indirect, being:-
There is normally considerably more weight over front axle, especially when weight transfers forward during braking.
Faster build up of dust on front wheels.
Faster wear on front pads.
Front pads normally about twice as big.
Front rotors are normally bigger or ventilated vs non ventilated.
But most of all, when I place my hand on the wheels after a very hard stop, the front wheels are uncomfortably hot while the rears are only noticably warm.
Regards
Pat
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RE: Caliper placement
I agree with the rear axles brakes are always cooler than the fronts and the rest of your description.
Citroen were using inboards a lot later than 1955's. Also the handbrake on the front wheels etc, awesome cars. If you have ever re-piped a BX or Xantia you would know what a joy they are to work on..
Some things like H1's still have inboard brakes due to the portal gears.
RE: Caliper placement
The D series was the most advanced compared to its peers as any car in history I think. Every so often Toyota launch an add campaign claiming to invent a feature that was on the D series. Steering and self leveling headlights spring to mind.
Regards
Pat
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RE: Caliper placement
Regards
Pat
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RE: Caliper placement
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
RE: Caliper placement
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.
RE: Caliper placement
Now that I think of it, the earlier models may also be rear steer/rear caliper, but I'm unfamiliar with them.
RE: Caliper placement
RE: Caliper placement
RE: Caliper placement
Thanks to all for the replys, youve all answered many of my questions.
Brian.
RE: Caliper placement
RE: Caliper placement
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
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"Node news is good news."
RE: Caliper placement
RE: Caliper placement
Well....I didn't mean to high jack this thread with my interjection.
I don't know anything but the people that do.
RE: Caliper placement
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
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RE: Caliper placement
RE: Caliper placement
Of course, you don't have to take my word for it, when there are images available - http:
RE: Caliper placement
RE: Caliper placement
"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