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Solid vs Vented Discs ?


zim
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Morning,

Just curious as to what peoples opinions are in regards to which disc brakes are better. This is for a challenge truck that doesn't get used on the road.

I've got solid fronts at the moment, with 46mm pistons.... from what i've measured the vented callipers are either the same or 41mm (like some solid callipers).

So am i correct in saying that in theory the braking force applied will be the same, just with a vented disc it can get rid of the heat quicker....not really an issue offroad :)

But they fill up with mud :blink:

Thoughts ?

Gordon

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Actually - from searching a bit, i'll stick with my solids :) just need to find another set for the back :ph34r:

A mod can delete this thread if they wish :)

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Morning,

Just curious as to what peoples opinions are in regards to which disc brakes are better. This is for a challenge truck that doesn't get used on the road.

I've got solid fronts at the moment, with 46mm pistons.... from what i've measured the vented callipers are either the same or 41mm (like some solid callipers).

So am i correct in saying that in theory the braking force applied will be the same, just with a vented disc it can get rid of the heat quicker....not really an issue offroad :)

But they fill up with mud :blink:

Thoughts ?

Gordon

Pretty much what you've already concluded really.

Braking efficiency boils down to (no pun intended), co-efficient of friction, the force exerted on the friction material and surface area. What the brakes do is convert the forward momentum (energy) of the vehicle into heat energy. On the road, the quicker you can dissipate the heat, the more consistent your brakes will be. As you say, the vents are there to dissipate the heat generated during braking through a larger surface area.

Therefore, in a challenge type event, or any circumsatnce where you are not doing heavy braking for lengthy periods, or from high speed, all they do is act as a mud trap, which defeats the object of having them in the first place.

My opinion, for what it's worth, would be to go with solid discs.

HTH.

Mark

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I've been thinking about converting to vented on the fronts for a bit now. Car is used for Towing and road quite a bit.

People I spoke to about this state that the vaines will fill up with mud. But I'm not so sure about this.

Granted watery / sloppy mud can get in, but vaines are designed to suck air in from the centre of the rotor and out of the end centrifugally. So this makes me think that any mud that can get in there can also get out, especially when the wheel is rotating at any reasonable speed.

I agree that off road there isn't much of a benefit as generally the brakes aren't used in as much 'anger' than on the road. But I don't see, other than costing beer tokens, that there is a negative to having vented disc's off road. So I'm still looking at getting the vented for mine.

MHO

Eeyore

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Having read about this for other vehicles I ended fitting cross drilled discs rather than vented.

My reasons being, vented discs are cheap way to increase heat dissipation, however according to the information I read, gas pockets form between the pad and disc under heavy braking, cross drilling and grooving help dissipate the gas, therefore increasing friction.

Ideally this would be better with vented discs as well, but I couldn't be bothered to change calipers etc as well.

The braking performance is much better with the cross drilled/grooved discs compared to standard.

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Having read about this for other vehicles I ended fitting cross drilled discs rather than vented.

My reasons being, vented discs are cheap way to increase heat dissipation, however according to the information I read, gas pockets form between the pad and disc under heavy braking, cross drilling and grooving help dissipate the gas, therefore increasing friction.

Ideally this would be better with vented discs as well, but I couldn't be bothered to change calipers etc as well.

The braking performance is much better with the cross drilled/grooved discs compared to standard.

You would never get the discs / pads hot enough on a LR for gas pockets to form ...........also braking performance is more dependant upon the pad material than the construction of the disc ………….

When you can get the discs glowing red in daylight and clouds of smoke from the pads it is then time to think about drilled grooved discs and water mist cooling. :rolleyes:

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I've fitted vented discs and new calipers to my 90" after fitting the 4.6 :rolleyes: and with 35" tyres it didn't want to stop - now it does - on the button. offroad they don't fill with mud and having been to hogmoore with them on i can say that every thing else filled with mud/sand they were still pleasantly free from the stuff.

If you don't have a problem stopping on road then don't bother changing but i won't be putting solid discs back on.

Steve

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I've fitted vented discs and new calipers to my 90" after fitting the 4.6 :rolleyes: and with 35" tyres it didn't want to stop - now it does - on the button. offroad they don't fill with mud and having been to hogmoore with them on i can say that every thing else filled with mud/sand they were still pleasantly free from the stuff.

If you don't have a problem stopping on road then don't bother changing but i won't be putting solid discs back on.

Steve

FFS Steve ......... you are getting as bad as Nige ..... it must be rubbing off (ooooer).........

I would expect it to stop better if you renewed the whole of the front braking system ! :rolleyes:

But I stand by the above ......... even with a 4.6 in a 90 you will be hard pushed to find the limit of the brakes. Your tyre compound and tread pattern plays a greater part !

The only time you might get the brakes hot enough in a LR is coming down a steep mountain road with a auto and having a fully loaded 3.5T trailer.

Ian

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Having read about this for other vehicles I ended fitting cross drilled discs rather than vented.

My reasons being, vented discs are cheap way to increase heat dissipation, however according to the information I read, gas pockets form between the pad and disc under heavy braking, cross drilling and grooving help dissipate the gas, therefore increasing friction.

Ideally this would be better with vented discs as well, but I couldn't be bothered to change calipers etc as well.

The braking performance is much better with the cross drilled/grooved discs compared to standard.

Unfortunately cross drilled discs will eventually crack through. It is a matter of when rather than if

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Just fitted vented to the front of mine, hopefully it'll help out a bit when I do some "spirited" driving. I've had issues a few times with cooking the front brakes to the point of losing brake performance. Not expecting any difference off road but will hopefully reduce the number of times I end up smoking the brakes on the road/gravel tracks.

Regardless of your driving style and how hard you push the brakes if you have a choice between solid and vented I'd go for vented. It will never be any worse than solid brakes and will give you an extra safety margin if you do end up using the brakes hard.

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Unfortunately cross drilled discs will eventually crack through. It is a matter of when rather than if

I've had/fitted cross drilled rotors on several high performance cars, not had one crack yet.

I have had vented and solid rotors crack though.

Besides all rotors wear out, so they will have to be changed at some point.

As for the drilled and grooved discs on the Disco, there was a definite improvement in braking over plain discs even with standard pads.

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I've had/fitted cross drilled rotors on several high performance cars, not had one crack yet.

I have had vented and solid rotors crack though.

Besides all rotors wear out, so they will have to be changed at some point.

As for the drilled and grooved discs on the Disco, there was a definite improvement in braking over plain discs even with standard pads.

Send some of your luck my way please :)

That is very much the exception rather than the rule. The other exception would be Porsche who as well as having rotors with huge heat capacity, cast their holes in rather than drill them thus avoiding the issues with stress raisers around the drilled holes. Any cross drilled discs which are getting used hard will crack through much much sooner than a similar spec grooved disc and since the grooves do nearly as good a job in degassing the pad, drilled discs in high performance use have pretty much become the preserve of weight conscious teams who aren't paying for their (short lifed) components

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