Brake disk switch

Others may disagree but I doubt you'll see any improved braking effectiveness just by switching to drilled disks. We had a big debate on this subject for mustangs. Bottom line is with the brake pad compounds we have now gas building up between the disc and the pad is no longer an issue.

There is no difference in brake effectivness between drilled or solid rotors. The drilled rotors will dissepate heat better and work better in the rain, and admit it.... they look cooler!

Qdude wrote:

Plummen,

It is an issue of the drilled disks being thinner than the solid disks.

Come to find out that the drilled disks wear more rapidly, are thinner and lighter, and should bolt right up if bolt patterns match as the pistons will compensate.

Lots of folks drill holes in the larger single front disc.

Qdude wrote:

Plummen,

It is an issue of the drilled disks being thinner than the solid disks.

Come to find out that the drilled disks wear more rapidly, are thinner and lighter, and should bolt right up if bolt patterns match as the pistons will compensate.

And lots of other folks leave their solid undrilled thinner oem dual front discs in stock showroon condition.

Can't prove it either way, but have heard drilled disc performs better in wet condidtions, And also heard whether drilled or not has no significant difference in rate of wear. Perhaps drilled performs cooler which could reduce chance of disc warp.

OnkelB wrote:

650ed wrote:

In addition to the diameter be sure to check the thickness of the disks. I know some models were different than others, but I don't know the details. Ed

The stock 650 rotors are 7 mm thick and have a 6 mm service limit, the Z1R rotors are 5 mm thick and have a 4.2 mm service limit. The difference in thickness didn´t present any problems when I did the swap though.

FSM for '73-'76 900's and '77-'78 1000's shows oem disc thickness on single front disc models of 6.9-7.1mm with service limit of 6.0mm. And shows '78 D1/Z1R cafe racer with mucho-drilled dual front discs (without specs -- so am guessing same as other dual front disc models).

FSM for dual drilled front discs '79 KZ1000 shows oem drilled disc thickness of 4.9-5.1mm with service limit of 4.5mm for both A3 standard model and D2/Z1R-II cafe racer model).

FSM supp for KZ900LTD (dual front discs) shows standard front disc thickness of 4.9-5.1mm with service limit of 4.5mm.

FSM supp for KZ900LTD shows standard single rear disc thickness of 6.9-7.1mm with service limit of 6.0mm (same as single front disc models).

So it seems all the large fours from '73 through '79 used same thickness on single front disc models (through '78) and same thinner thickness on all dual front disc models (regardless of whether drilled or solid).

Addition -- and also seems the thicker single rear disc thickness remained constant at least through '79 on the large fours.

Patton wrote:
... And shows '78 D1/Z1R cafe racer with mucho-drilled dual front discs (without specs -- so am guessing same as other dual front disc models).

[/quote]

I think the service limit is stamped into the Z1R discs I have, I´ll check it tomorrow.

you da man:cheer:

Ok, my memory failed me - the service limit for the Z1R discs is 4.5 mm, not 4.2 as I said earlier. The service limit is stamped on the inside of the disc centerpiece (sorry about the crappy pic, camera ran out of batteries before I could take another one).

Plenty clear enough to show the 4.5 mm,

Much thanks !!