slotted rotors

[alke46]

I have the 79 GS1000E model with solid rotors. I'd like to change it over to use slotted rotors. Can this be done? I think someone mentioned once to me that my stock calipers would NOT work with slotted discs.

I have a set of slotted rotors that came to me a couple of years ago but when I took some measurements today I found out they will stick out a little bit, something like .5mm compared to my solid ones.

Any suggestions?

edit: I have a slotted disc on the rear but I can't recall taking measurements of it. It seems to be working OK.

[salty_monk]

Yeah I think you have to use them as a set from memory. The later caliper is much better than the early round pad one anyway....

[Rob S.]

Or you could just drill the existing front rotor. Before slotted, drilled discs were all the rage.

[alke46]

Or you could just drill the existing front rotor. Before slotted, drilled discs were all the rage.

That's an option worth more thought.

[Rijko]

Larry,

afaik the slotted rotors have the same dimensions as the solid ones and are interchangeable.
That .5mm is thickness of the discs ? Should not be an issue.
On the back of the discs is stamped what the minimum thickness should be.
Approx. 4.5mm

[alke46]

Larry,

afaik the slotted rotors have the same dimensions as the solid ones and are interchangeable.
That .5mm is thickness of the discs ? Should not be an issue.
On the back of the discs is stamped what the minimum thickness should be.
Approx. 4.5mm

No, the .5mm was not the thickness of the disc. It was the center hub where it installs on the wheel. I think it was going to cause an alignment problem with the caliper/pads.
Not sure if that .5 would matter but it looks like the pads would not be fully covering the disc.

I'll try to get a pic of it later today so I can show what I am talking about. Should have done that yesterday when I had it apart.

The slotted discs each measured 4.93mm with minimum being 4.5mm.

[Grimly]

All I can tell you is that I've been swapping front and rear wheels between a 79 and an 80 GS850 for years and they just fit, no fuss.
At the moment the 80 bike is using a rebuilt pair of GS1000 forks and no problems with that set-up either - same wheels as before, but I haven't yet tried the plain rotor 79 wheel on those forks. I see no difference between them.
I'd already fitted the later calipers to the 79 forks on that bike and they fitted perfectly, with no issues of clearance at all.
0.5mm is barely thicker than the paint - nothing to worry about.
The only thing that catches you out is the damned L fork legs - same calipers, but the mounting lugs on the legs and the brackets are different.

[storm 64]

Or you could just drill the existing front rotor. Before slotted, drilled discs were all the rage.

Larry, I can drill your solid rotors if you'd like. I did the ones on my 1000 and they came out pretty good.👍

[alke46]

Thanks for the replies felllows. I got some pics of the two different rotors tonight and it does look as though I could get by with switching to the slotted ones. My only concern is the amount of pad that covers the solid disc and how it would work on the slotted one.
The pics will show what I am concerned about.

From reading Grimley's post though it seems there is nothing to worry about. Guess I will give it a go and see for myself.

IMG_20200818_213329875 by Larry Alkire, on Flickr

IMG_20200818_213206678 by Larry Alkire, on Flickr

IMG_20200818_213206678 by Larry Alkire, on Flickr

This is the side by side difference of the two. The solid is on the left and the slotted on the right.

IMG_20200818_213710579_MP by Larry Alkire, on Flickr

[alke46]

Larry, I can drill your solid rotors if you'd like. I did the ones on my 1000 and they came out pretty good.

Thanks for the offer Norm. I will keep you in mind if I go that route. Just trying to get all my ducks in a row

[salty_monk]

Well I guess my thoughts on the standard of GS brakes is pretty well known... I wouldn't want to be riding with the round pad type if I had other choices. The swept volume of the later caliper is far greater than those....

[alke46]

I know what you mean Dan. But I've got two sets of those round pads and you know what they say about the GS family. Most of us are a bunch of cheap bastards.

[greg78gs750]

or go all the way and do the saltymonk mod, not sure if he has plates available still, buuut...

[salty_monk]

I know what you mean Dan. But I've got two sets of those round pads and you know what they say about the GS family. Most of us are a bunch of cheap bastards.

yeah I know... Can't spend it when you're dead though.. that's what I always think with safety critical stuff. You have a few years more practice at managing the risks than me

[alke46]

A further update finds the slotted discs that I have compared to the solid discs measure 5mm thinner in the center hub area. Therefore, to fit the slotted discs, I will have to either buy 12 new bolts that are 5mm shorter, or have a 5mm spacer made to fit behind the disc. I don't know, maybe I'm over thinking this.

Looks like nothing will happen until winter.