Why are the front rotors mounted on the front of the brake disc on an X Type? This is the first street car I've owned that had this configuration. I have seen this on race cars. I assume it must improve braking?

 

You mean the caliper being forward of the rotor not behind it?? Yes it has to do with braking power as far as I've ever seen in cars.

 

Cooling the calipers?????

Never noticed until you mentioned it. Odd.

 

It's just better

 

Steering gear is behind axle so caliper goes in front.

 

the funny part of this question is that most cars are like the Jag, With the steering rack at the bottom of the firewalll.
Maybe tomorrow I will explain why this is the cheap *** way to do it.. lol.
Check BMW and Porshes, with the caliper toward the rear. Ever wonder why they ALWAYS win the best steering feel?

 

I talked to a person who is an engineer and a real big car nut. His take on this type of from caliper mount is cooling, and better braking performance, due to the dynamics of deceleration, whatever that means. He didn't elaborate on the dynamics business, so I am going to do a Google search and find out.

 

Mounting the caliper to the front of the rotor is bsically for cooling. Think about it. You are converting mechanical energy into heat so you can stop the car. Would you want the caliper to be getting the cool air coming off of the front bumper or the warm air after it has passed by the hot rotor. If you need a demonstration of what I am talking about, get your car up to highway speed and then do an emergency stop. Put the car into park and put your hand near the rotor. This is what about 800-900F feels like. You do a few of these and you can push the rotors to well over 1100F (seen some cases of the metal starting to turn red). Every degree makes a difference for that.

Granted, sometimes it is a mechanical reason. If the steering joint is on one side of the axle, this can force the caliper to be on the other side of the axle. It all depends on how the engineering is worked for having adequate steering force to ensure you can turn the wheels in all cases.

 

Sorry guys, the cooling might be a logical answer but it is not the real reason.
Plenty of cars have cooling ducts that blow cooling air on brakes and they direct it to the right location It does not matter if the caliper is in front or rearward of the centre of the wheel.

Most steering knuckles are made with several attachment points, they have to hold the wheel bearing, the suspension control arm joints, sway bar links, spring and shock attachment points, and the steering tie rod connection.
with so many attachment points they are spread out all around the axle. It is very rare to have all these things on one side of the knuckle.

For most cars, the easy way to connect the steering, is to have the rack on the firewall, or on the subframe at the rear of it. The tie rods extend to the wheel, to the rear of the centre, and it just makes things easier to design when the caliper is at the front.

The more difficult way to do the steering ,is to put the rack at the bottom of the radiator, or on the subframe toward the front. This way the tie rods extend to the wheel at the front of the axle.

So why do some car makers go to the trouble of moving the rack forward?
when you take a turn, the tire is pushed sideways by the road. This force is resisted by all the above connections noted above. The tire pushes on the wheem which pushes on the hub, then the bearing, and next to the knuckle. with this force on the knuckle it then pushes on the car body via the suspension links and the tie rods.
Car suspension are attached by soft rubber bushings, and as you corner they get squished sideways a little. The steering rack is almost rigid, and when the tie rod gets this sideways force, it does not give or move.
The result is that the suspension squashes a little with the cornering force but the tie rod does not.

Now if the rigid part (the steering) is at the rear, the squishing of the suspension makes the wheel turn a teeny bit sharper. If the steering is at the front, the cornering force makes the wheel steer a teeny bit less sharp.

Got it?

Now why is one way better?
consider taking the same corner at different speeds. The faster you go, the higher the force is.
If you have the steering at the rear, the faster you go the LESS you need to turn the steering wheel to make the same turn.
If you have the steering link in front, then the faster you go, the MORE you need to turn the steering wheel to make the same turn. Drivers that care about steering feel find that more speed = more steering input is much easier to use.

Let me know if you can make sense of this, much easier to do with a pen and paper... lol

 

HERE IS THE ENGINEERING REASON.....
During cornering there are centrifugal forces acting on both front wheels and on the steering linkage.
If the wheel and steering linkages centre-of-gravity's are in front of the steer-axis , due to say, heavy front mounted brake calipers and front mounted steer-arms and rack and pinion, then the centrifugal forces act to turn the steering towards straight ahead-there is an increased self centring effect. With the CG's behind the steer axis there is a de-centring effect. Brake calipers are often mounted behind the wheel axle to minimise the load on the wheel bearings during braking. The de-centring effect of rear mounted calipers can be counted by the self-centring effect of a front mounted steering linkage. We Can estimate the size of these torque:
Tcg=Fcg*Lcg(Nm)
Where
Tcg=torque about the steer axis due to the inertial force of the wheels assembly
Fcg=inertial force at the CG
Lcg=length of the CG lever-arm"

 

Lets face it on a Skyline the caliper is on the front... mine had excellent handling and control and a very good feel from the steering. I dont think it makes a fat lot of difference to be fair. RWD cars only have the steering at the front and no power to them so less components than fwd or a 4wd vehicle.

 

All very interesting post, enjoyed reading them. As far as handle goes, my cars has very precise steering and centering and the brakes themselves are some of the best I have had on a car. And I owned BMW, and MB, Audi.

 

I did an search on Google on Front mounted rotors and could not find any explanation. But the ones here are very interesting and the varied opinions make for a lively discussion. Going to the hospital today for more test on my stomach, they still can't find what is wrong the endoscopic surgery showed nothing, today they are during a CAT scan and I have to drink 2 bottles of that god awful barium. I will let you all now what is up.
Thanks for all your support.

 

I'm going with Sport30's explanation on this one. It's best to have the steering rack in front of the front wheel center due to:
* steering input is progressively higher with cornering load
* understeering is built into the steering system thus rest of suspension bushing can be optimized for impact harshness
* since our X-type has engine where the ideal steering rack should be located, it's located behind the wheel center thus caliper was moved to forward position

Having said this, I'm sure there are other FWD/AWD cars with caliper in the back position. They may have tie rod attachment point further away from knuckle with compromised Achermann geometry. Or they may have the funky double lower ball joint design that some Audi and BMW uses.