الموضوع: هل مكان الكاليبر بيفرق في حاجه في الفرامل؟

سؤال لذيذ كنت فكرت فيه زمان ودورت كتير على الاجابة العلمية للموضوع ده

الاجابة باختصار لا ، مفيش فرق في قوة الفرملة نفسها

هو فرق في توزيع الاحمال مش اكتر ومحصلته النهائية على كل المكونات ثابتة بس اللى بيختلف هو درجة تأثر كل مكون عن التانى في كل وضعية
يعنى مثلا لو باصين على العجلة الشمال قدام ، لو الكاليبر من ورا ( عند الساعة من 1 لـ 5 ) يبقى كأن الدسك بيحاول يرفعه لفوق اثناء الفرملة ، وده بيعمل حمل اقل على بلي العجل من لما يكون الكاليبر قدام ( الساعة 7 لحد 11 ) والدسك كأنه عايز يحركه لتحت (لحظة الفرملة)
ده التأثير من وجهة نظر بلي العجل مثلا ، ومش فاكر تفسيرها بالظبط ، بس طبعا زي ما قلت ، لو قللت الحمل على بلي العجل مثلا بيزيد على مكون تاني بحيث يبقى المحصلة واحدة

اللى بيفرق فعلا بتأثير دقيق جدا هو وزن الكاليبر بس مش فاكر برضه السبب ايه بالظبط

المقالة اللى قريتها كانت مطولة جدا ومتخصصة جدا ، وكان كمان بيشرح ازاى ان ممكن تخفيف الحمل على بلي العجل يأدي للعكس ويأثر على دقة التوجيه اثناء الفرملة ،

هدور على السؤال والاجابة واحطهم هنا ممكن حد يفهم حاجة اكتر ويشرحلنا في النهاية بشكل مبسط

EFFECT OF CALIPER MOUNTING POSITION


What effect on wheel loading does the positioning of the calipers in a leading or trailing location
have i.e. mounted at 3 and 9 o clock positions? Does a trailing caliper add or subtract load on the
front tires? In a rear independent suspension, does a leading caliper add or subtract wheel loading,
and is it the same in a live axle situation?


The short answer is no. Caliper location has no effect whatsoever on wheel loading. Having the
caliper s mass lower or higher does have a very minute effect, because it affects the CG location a
tiny bit, but there is no difference between a 3 o clock mounting position and a 9 o clock position.
However, there is an effect on bearing loads. It might seem counterintuitive that we can change the
bearing loads and not change the tire loads, but that is in fact the case. As the questioner appears to
have considered, the disc tries to carry the caliper upward if the caliper is trailing, and downward if
the caliper is leading. That reduces bearing loads if the caliper is trailing, and increases bearing loads
if the caliper is leading. However, these forces are reacted entirely within the
hub/bearing/spindle/upright/caliper/disc/hat assembly, and do not change the loads on other parts of
the car

.
We can think of it like this: Gravity acts downward on the car, with additions and subtractions due to
inertia effects and aerodynamic effects. The road surface holds the car up. Or, we may say the road
holds the tire up; the tire holds the wheel up; the wheel holds the hub up; the hub holds the bearings
up; the bearings hold the spindle up; the spindle holds the upright up; the upright holds the
suspension up; the suspension holds the sprung mass up. If the caliper exerts an upward force on the
upright and a downward force on the disc, that just means the brake is helping the bearings and
spindle hold the upright up. It doesn t change the total support force, only the load path within some
of the unsprung components.


It is worth noting that in braking there are also horizontal forces acting through the wheel bearings.
The car is trying to keep going forward at a constant speed. The road surface is exerting a rearward
force on the car, through the tires, wheels, hubs, bearings, spindles, uprights, and suspension. We can reduce the bearing loads due to this component if we mount the caliper above center, or increase the
bearing loads if we mount the caliper below center. In fact, the horizontal force may be greater than
the vertical force on the tire. With racing slicks on dry pavement, the horizontal force may be 1.3 or
more times as great as the vertical load on the tire. So for least bearing loads during braking, the
caliper should be somewhere in the upper rear quadrant around 1 o clock or 11 o clock, depending
on which wheel we re looking at, and from what direction.


Now, do we actually want maximum cancellation of the bearing loads by the brakes? We might
suppose so, but actually there is an argument for not having maximum cancellation. The effective
radius of the brake (roughly the radius to the middle of the pad) is often less than half of the tire
effective radius. This means that the force at the caliper is more than twice the rearward force at the
tire ....... patch, and it may also exceed the vector sum of the vertical and horizontal forces at the
....... patch. Consequently, the caliper force may not only reduce the bearing loads, but reverse
them. If there is any free play in the bearings, or deflection in the components, this load reversal may
result in a vibration or a small variation in the steer angle of the wheel. So there is a case for building
the components nice and strong, and positioning the calipers so the bearing loads will not reverse.
Of course, as a practical matter, if we are using purchased calipers we need to mount them with the
bleed screws at the top, or very nearly so, just to facilitate good brake bleeding without requiring the
calipers to be dismounted. This may well outweigh any theoretical considerations. If we are
designing from a blank sheet of paper, we don t face this constraint, but most of us, most of the time,
are designing around purchased calipers.


Another practical constraint is packaging, particularly of the steering arms and cooling ducts.
There are some ways in which we can affect wheel loads by the design of the brake system and the
suspension
I am referring here to the longitudinal anti or pro effects: anti-dive or pro-dive in the
front suspension, anti-lift or pro-lift at the rear. With independent suspension, it makes a difference
to these effects whether the brakes are inboard or outboard. With a beam axle, it makes a difference
if the calipers are mounted directly to the axle, or on birdcages or floaters that rotate on the axle and
have their own linkages.


However, with all of these, we cannot significantly alter the loading on the front or rear wheel pair,
nor on all four wheels. We can change the way the sprung mass moves in response to braking, and
this may have small effects on CG height, with corresponding small effects on overall load transfer.
But the big effects come from having geometry differences on the right and left sides of the car.
These may be present even in supposedly symmetrical road racing cars, because no car stays
symmetrical when it rolls. In oval track cars, we often design in, or adjust in, asymmetry even in the
static condition. Such asymmetry can produce significant changes in diagonal percentage when
braking, and we can use these to tune corner entry behavior.