Slotted discs - which direction?

[zs]

with or opposing wheel (forward travel) motion direction?

with...



opposing...



(Sorry if repost - search engine not showing any results...)

[pits]

zs said:

with or opposing wheel (forward travel) motion direction?

Worst I dont know which upgraded discs to go for, on my Viper, post ever.


To be fair I dont think it really matters but I do believe that on my car the grooves are like the top picture, ie the grooves curve up towards the back of the car, not down towards the ground.

[Project 644]

Opposing.

[elster]

Project 644 said:

Opposing.

Won't that defeat the purpose of having them?

[diddles]

Its the internal cooling vanes that determines the install of a vented slotted disc not the slot direction pattern.

If the internal vane is straight then it will make no difference which way round a slotted disc is installed. You can install these types of disc which way you think looks best.

If the internal vane is curved/angled then the disc needs to be installed with the curved/angled vane pointing the rear of the car. These types of discs will generally be marked as to which side of the car they are for.

If in doubt ask the disc manufacturer

Edited by diddles on Tuesday 24th November 03:07

[redtwin]

If you buy Stoptech slotted discs you get one of each. One side curves with and the other curves against. Stoptech say that it is not a manufacturer defect and that the slots follow the cooling vanes of the vented discs.

Personally I like them curving with the rotation of the wheel.

[mat205125]

It's the vents inside the disc that are more important than the grooves on the outside. On most discs, however, these will be angled in the same direction.

Cooling air is designed to be taken into the centre of the disc, and expelled out of its perimeter. Likewise, the cleaning grooves are meant to clean the material out of the disc, rather than towards the hub.

The discs on that (abolutely stunning looking) black Viper appear to be fitted the wrong way around - i.e. to the wrong side.

[crofty1984]

For me, I'd say "with" as the dust is more likely to get thrown out, which is what you want.

[kambites]

Logic would dictate to me that the Viper is the wrong way around because dust will accumulate in the grove and the curvature will stop it getting thrown out of the outside of the disk. That may, in practice, make absolutely bugger all difference though.

[AndyBe]

crofty1984 said:

For me, I'd say "with" as the dust is more likely to get thrown out, which is what you want.

I think so too. Like the EBC discs here:

[eastlmark]

maybe depends on the Calliper leading or trailing?

[Paul Drawmer]

The primary consideration is as others have said, that the cooling vanes, if curved internally, must be aligned so there is a low pressure area behind the vane to draw the air out from the centre of the disk.

If the internal vanes are just straight radials (rare) or there are just pin separators (as on cheapo vented discs) then the alignement of the slots will determine of the pad gets pushed to the inner or outer of the caliper fitting. If your calipers hold the pad by one central pin on the outer edge (often with a spring), then make sure that the grooves tend to push the pad inwards where there are two bearing surfaces (one at each end of the pad)

[jshell]

zs said:

opposing...

]

This pic is wrong, they should be the other way round.

[benny.c]

jshell said:

This pic is wrong, they should be the other way round.

Sorry, but that is nonsense. There is no way you can tell unless you know who make the disks. The Brembo kit on my Mustang and the AP kit on my track car both have slots/holes that face "forward". Both are fitted correctly.

Edited by benny.c on Tuesday 24th November 09:43

[jshell]

benny.c said:

jshell said:

This pic is wrong, they should be the other way round.

Sorry, but that is nonsense. There is no way you can tell unless you know who make the disks. The Brembo kit on my Mustang and the AP kit on my track car both have slots/holes that face "forward". Both are fitted correctly.

The direction of the holes makes no difference to the disc's performance.

The direction of slots does! It's basic engineering principle in the way that a pump impeller, a compressor's vanes or the way ventilated discs work. The slotted spinning disc ejects material (water/dust etc) outwards using centripetal force. The slots pointing forwards prevent this happening as efficiently as they scoop air and debris from the outside of the disc and try to force it inwards against the favourable debris path. The 'trailing' slots help this work as they scoop air from the inside of the disc and throw it outwards together with the debris.

You need to swap sides with your discs.

[benny.c]

jshell said:

You need to swap sides with your discs.

You need to stop making things up. As others have said, it is the vane direction that does the cooling. On APs the vanes run in the opposite direction to the slots. If I swap the disks I would get no cooling from the vanes. You'll forgive me for following AP's advice wont you?

http://www.apracing.com/info/info.asp?section=Disc...

[jshell]

benny.c said:

jshell said:

You need to swap sides with your discs.

You need to stop making things up. As others have said, it is the vane direction that does the cooling. On APs the vanes run in the opposite direction to the slots. If I swap the disks I would get no cooling from the vanes. You'll forgive me for following AP's advice wont you?

http://www.apracing.com/info/info.asp?section=Disc...

Always follow the manufacturers advice!

That pic does show the slots running forward, I just don't see the reasoning for that at all. The cooling vanes do run as I said above though to throw air outwards for cooling. I always thought the disc clearing function of the slots would operate in the same way!

[Ozzie Osmond]

benny.c said:

jshell said:

You need to swap sides with your discs.

You need to stop making things up.

+1. It can be entirely acceptable for the grooves in the friction material to run opposite directions on opposite sides of the car. As others have said, it's the construction of the disc which matters.

[benny.c]

jshell said:

Always follow the manufacturers advice!

That pic does show the slots running forward, I just don't see the reasoning for that at all. The cooling vanes do run as I said above though to throw air outwards for cooling. I always thought the disc clearing function of the slots would operate in the same way!

Looks completely wrong but I'd like to think AP know what they are doing!

If it's any consolation, we fitted them on the wrong side before we read the instructions

[jshell]

I'd like to look further into this, must be some valid reasoning! Maybe that internal vanes and external slots running together may induce weak zones in the material of the disc and make them more prone to shatering....