Twinpot Brake upgrade on 78 Skunk

[salty_monk]

I suspect Don is using the 98 900RR rotors. They are 310mm & the bolt pattern is correct the holes just need enlarging.

I suspect Windcrow is using the 600CBR F3 Rotors (They look the same). They are 296mm. These are the ones I used but the bolt pattern is different to Suzuki.

Instead of enlarging the hole which in my opinion is the wrong way to do it as you build in potential for the rotor to slip back & forwards & the holes becoming elongated over time (It's only Aluminium) I used a jig to drill new holes at the correct size & pattern in between the original bolt holes.

Yes I do have a couple of sets of brackets & spacers left but to use them with that rotor you'll also need some hub spacers. This brings everything into alignment so the calipers are placed centrally over the rotor & you use the full width & depth of the pad.

If you have pad alignment issues then you need to be careful about caliper clearance on the rotor (basically as the pad wears you could reach the limit of movement of the rotor & the caliper half will drag on the rotor).

Be careful of caliper to wheel clearances too, it's quite tight the way you have it fitted with the caliper bracket on the inside. Out of interest what thickness of material are you using for that Tag you have going to the bottom bolt hole?

Cheers,


Dan

[Suzuki_Don]

Hi Dan,
I am using the Fireblade 296mm rotors from '94 to '97. Drill out and bolt up. Of course I drilled undersize and then reamed the holes for a perfect fit, no movement when brakes are applied. No elongation.

[salty_monk]

Hmm, not sure then... I just thought this guy might be using the same rotors I have. If you simply drill those out to size they won't fit as the PCD is wrong.

The PCD is right on that rotor I sent you but that was a 310. There are obviously some smaller ones with that PCD over there too, I haven't seen any over here but that isn't to say there aren't some!!

[Suzuki_Don]

Dan the Fireblade obviously use the same wheel, hub, I would think, no matter which disc they are using. So whether Honda are using the 296mm or 310mm on the Fireblade the spacing would be the same. So the 296mm CBR900RR discs that I have used have the same PCB (whatever that means) spacing as the 310mm disc that you sent me.

BTW I purchased the 296mm discs from the US. And they are quite distinctive from the other Honda discs in the pattern the holes are drilled in the discs for ventilation. Which can be seen in the pic I included at the bottom of this page.

These CBR900RR discs also have 10 rivets holding the outer braking surface to the inner as opposed to the eight on the CBR600 discs.

I guess in the end people are going to use the discs that are more available and easily obtainable even if it is a bit more work to make them fit. And it would seem there are more CBR600 discs around than the CBR900 discs. I guess I was just lucky as I bought them on EBAY from the States and you dont get to ask too many questions in that arena. So I took a risk not really knowing if they would be a perfect fit or not -- and as luck would have it they did fit perfectly with minimal work.

BTW Dan thanks for all your help in those early days of these modifications and even though I ended up not using your brackets your help and advice was very much appreciated. GS owners are very few on the ground over here and it was great to have someone to bounce ideas off. Both you , Jeff and Mark Mattock were a great help to me.

[salty_monk]

That makes sense Don. I guess the 900RR ones are the ones to go for over the 600 if you don't want to re-drill just enlarge then

[gearhead13]

Pic of the twinpot setup on my GS750
Thanks, Dan.

[salty_monk]

Looking good! Clearances all work out for you or did you have to make any adjustments to the hub spacers?

Dan

[gearhead13]

No, all clearances were fine went together real easy, love that two finger braking now
I did have to open up the inner diameter of the spacer, just used a dremel.

[salty_monk]

That's good news. I would make that large hole a little bigger if I did them again. Seems more need opening up than not. Maybe I have a freak hub here

[windcrow]

[QUOTE=salty_monk;1046942]I suspect Don is using the 98 900RR rotors. They are 310mm & the bolt pattern is correct the holes just need enlarging.

I suspect Windcrow is using the 600CBR F3 Rotors (They look the same). They are 296mm. These are the ones I used but the bolt pattern is different to Suzuki.

Instead of enlarging the hole which in my opinion is the wrong way to do it as you build in potential for the rotor to slip back & forwards & the holes becoming elongated over time (It's only Aluminium)

Salty-- You're absolutely correct. I didn't know of any other method to use while I doing it. Right now the discs are holding .

I used a jig to drill new holes at the correct size & pattern in between the original bolt holes.

Can you describe the jig you built


Yes I do have a couple of sets of brackets & spacers left but to use them with that rotor you'll also need some hub spacers.

I can paypal you for that

This brings everything into alignment so the calipers are placed centrally over the rotor & you use the full width & depth of the pad.

If you have pad alignment issues then you need to be careful about caliper clearance on the rotor (basically as the pad wears you could reach the limit of movement of the rotor & the caliper half will drag on the rotor).

Noted.

At present, the new brakes work awesome, but I don't completely trust what I've done so far. I'm not getting paid to road test my leathers

[salty_monk]

The hub spacers I have also serve as a drilling template. The problem is that the way it works is that there are 2 6mm holes on the CBR PCD to bolt to the original holes, once bolted down tight you simply drill through the 8mm holes (making sure you drill straight i,e. 90 degrees to surface). You would have to do whatever you have done CBR rotor holes on those 2 holes as well to get it all to line up...

If you want to stick with what you have I just a drilling template (works the same as described above but no centre hole)

PM me if you want prices on brackets etc same as the ones shown above.

Cheers,

Dan

[gearhead13]

I have pulsing in my front brakes, only noticable as you come to a stop. Not noticable at highers speeds only under~15 km/h. When you spin the front wheel, there is a tiny bit of wobble in the rotors. I took them off today and checked the mounting surfaces to make sure there wasnt anything underneath the spacer cocking the rotor up on one side. Havent taken it for a ride yet, but there is still some slight wobble.
The guy I got them off of says "they were just fine" . Ya, and I am the king of England

[salty_monk]

It's not uncommon to get a warped rotor that you can feel at slow speed (a front wheel bearing going out can also feel the same so check those too).

Nessism had one on a 550 that you could feel pulse even though it was still within Suzuki tolerances!

Dan

[salty_monk]

Just 2 sets left now (& one guy supposedly picking a set up on Friday so that will make one left)... any more will probably be on a bulk buy basis.

I also have a plan to build some in powdercoated steel which might help bring the price down but again they would probably be on bulk buy basis & prob not till the winter.

I have had some mild interest in building a set for the single rotor models (GS550 etc). I am happy to do the R&D if someone can send me a front end & wheel to play with (or actually just the fork lowers & a wheel with the right spacers to set the width would do it).

Dan

[sparki]

Just 2 sets left now (& one guy supposedly picking a set up on Friday so that will make one left)... any more will probably be on a bulk buy basis.
Dan

would you be able to ship to the UK? I need something more on the front of my katana (81) as the OE kit is a little lacking

what is included in what you're selling?.... mounting plates and single spacer for the bottom mount?...

from what i'm reading i understand i'll need some 900rr discs to drill out the 6mm to 8mm and find some mid-late 90's kawasaki calipers that slide on the rear?...

cheers
steve