Front Disc Brake Modification

I'm working on installing a floating disc with Brembo caliper on my MKIII.

I need some help from those of you that have done their own front disc mods.

I am using an EBC 320mm floating disc which I modified to fit the Norton bolt pattern.

https://www.flickr.com/photos/22794316@N03/11800716003/

I took measurements and made a spacer to move the disc position to approximately the same position out from the hub as the stock Norton disc but the EBC disc is up against the slider by a very slight amount.

https://www.flickr.com/photos/22794316@N03/11801214486/

Has anyone run into this? This disc position allows the Brembo caliper to be in the same plane as the mount points on the slider which make the mounting bracket easier to fabricate but will require that I machine some clearance off the slider to allow the disk to clear. I could reduce the thickness of the spacer, but then the mounting bracket for the caliper becomes more complicated. I plan to make my own mounting bracket because I am using the more common 65mm bolt spacing Brembo caliper. There are no brackets for these.

I could just leave the spacer out if I have to make a more complicated bracket which gives me plenty of clearance for the disc.

https://www.flickr.com/photos/22794316@N03/11800461315/

It looks like this position will work and everything seems to clear okay. The bracket will need to be stepped or have spacers to get the mount positions to work.

If anyone has done a similar mod to their Commando please let me know what you did so I don't completely reinvent the wheel so to speak.

Mine ended up similar your last pic using the RGM 12" disc but I used the 40mm bolt spacing Brembo caliper and made a stepped bracket to suit.
sam

Thanks Sam.

Looking at this I think your suggestion makes the most sense. I was trying to see if there was an easier way to do the bracket.

I decided to see if I could figure out the 65mm Brembo because there are tons of them out there for a lot less money than the 40mm. I'm surprised that more people haven't tried this. I did a quick layout of the bracket and will make a quick template up to see how it fits and how much step I will need to get the alignment.

Here's a screen shot of what the bracket looks like. From everything I can see it should work.

https://www.flickr.com/photos/22794316@N03/11802817436/

Thanks again for the help.

Dennis

dennisgb said:

Thanks Sam.

Looking at this I think your suggestion makes the most sense. I was trying to see if there was an easier way to do the bracket.

I decided to see if I could figure out the 65mm Brembo because there are tons of them out there for a lot less money than the 40mm. I'm surprised that more people haven't tried this. I did a quick layout of the bracket and will make a quick template up to see how it fits and how much step I will need to get the alignment.

Here's a screen shot of what the bracket looks like. From everything I can see it should work.

https://www.flickr.com/photos/22794316@N03/11802817436/

Thanks again for the help.

Dennis

Click to expand...

Yep Dennis,

Your pic is similar to my bracket except mine is longer make use of the front fork bottom lug as a third bracket mount.Sort of like a long V bracket . I really will have to learn how to post a pic :?
It's strange that the 40mm bolt space calipers are cheaper than the 65 mm over here, they were fitted to Ducati 748s, but also to Cagiva planet bikes and other small bikes I guess.
sam

I just bid on 4 pot brembos and ended up with 2 40mm, so they are cheaper this side of the Atlantic than 65mm.

trident sam said:

Your pic is similar to my bracket except mine is longer make use of the front fork bottom lug as a third bracket mount.Sort of like a long V bracket .

sam

Click to expand...

Yes I looked at tying into the bottom lug and may do that...the bracket kind of gets big and ugly but would be stronger for sure.

I made up a template of the mounting bracket from the drawing I made and it looks like everything comes out right.

Here's a picture of it.

http://www.flickr.com/photos/22794316@N03/11806438764/

After seeing it on the fork, I think it needs to be a little stronger. I think I'll make one that ties into the bottom of the slider to see what it looks like.

With the right thickness of material that should be plenty strong. I've seen several versions like that for sale.

bwolfie said:

With the right thickness of material that should be plenty strong. I've seen several versions like that for sale.

Click to expand...

Making it out of 6061 Aircraft Aluminum. It will be 1/2" thick but stepped so mounts will be about 1/4"...will keep it thicker through the transition. My concern is this is an MKIII with the brake on the left so it is "pulling" against the bracket rather than "pushing" if it were on the right. The bottom bolt web on the Brembo looks a little weak to me. I've been thinking about just flipping it all around and putting the brake on the right side tho.

I made up a longer bracket template that ties to the lower slider bolt.

I think this is the way I will go with it.

Here's a picture of it.

http://www.flickr.com/photos/22794316@N03/11808378946/

I took a shot of it if it was on the right...but it creates a problem with the fender bracket. The MKIII only has one fender bracket that will clear if the caliper is on the left side. I think I will leave it on the left.

http://www.flickr.com/photos/22794316@N03/11808377136/

Looks good. I'd also add a lightening hole or 3.

You realize these calipers are designed to fit behind the fork leg? They have a larger piston (34 mm) and a smaller piston (30 mm). It probably will work fine reversed, but it's not the way it was designed. Brembo has been making top quality brakes for a long time, so I would assume they have a good reason for this design.

Ron L said:

You realize these calipers are designed to fit behind the fork leg? They have a larger piston (34 mm) and a smaller piston (30 mm). It probably will work fine reversed, but it's not the way it was designed. Brembo has been making top quality brakes for a long time, so I would assume they have a good reason for this design.

Click to expand...

Ron,

I knew the pistons were different, but didn't know that they were designed to be placed in a certain orientation.

Dennis

From Brembo:

"Brembo's calipers are directional, due to the use of differential piston sizes. The leading pistons are smaller in diameter in order to combat uneven wear of the brake pads."

With the 40mm caliper the bracket can be made a lot slimmer, but I'd be happy with yours and maybe just take some material out between the right side caliper mount bolt and the lower bracket mount. I never noticed the pistons were a different size until mentioned above, but it all works fine .
sam

Dennis,
Regarding mounting the disc on the right hand side behind the slider, the old commando service notes produced by John Hudson in the UK Norton Owners Club mentioned that when the factory did this originally, the bike pulled to the right. Moving the caliper in front of the slider on the LHS eliminated the problem. No one ever explained why, it just worked.

It sounds like you have gone a long way down the road to fitting the caliper - my experience with the Norvil disc was to file the slider and polish out a radius until I had clearance - its been fine for about 20 years now.
Regards, Ian

HoveToo said:

Dennis,
Regarding mounting the disc on the right hand side behind the slider, the old commando service notes produced by John Hudson in the UK Norton Owners Club mentioned that when the factory did this originally, the bike pulled to the right. Moving the caliper in front of the slider on the LHS eliminated the problem. No one ever explained why, it just worked.

It sounds like you have gone a long way down the road to fitting the caliper - my experience with the Norvil disc was to file the slider and polish out a radius until I had clearance - its been fine for about 20 years now.
Regards, Ian

Click to expand...

Yes I've read about the pulling to the right but can't figure out why that would happen either...seems strange. Maybe someone here that knows the answer could explain.

Filing the slider or machining a little off to get the disc clearance is an option. Once I got it all bolted together there is actually a small amount of clearance between the disc and the slider with the spacer in place. The rivets (or whatever they are called) that hold the disc to the carrier hit though. It wouldn't take much to get the clearance needed. I like that position because it simplifies the mount, and the caliper is nicely on center of the disc without any adjustment needed. With the offset (no spacer) the bracket will need to step and control that positioning. I think both methods will work.

I thought this is the reason for multiple pistons ??? •Differential bore calipers -- As the surface of the rotor heats up, the clamping force of the pistons has to be increased to avoid brake fade. If the caliper has multiple pistons (or multiple pairs of pistons), the brake rotor surface is initially heated by the pistons pushing against the brake pad at the leading edge of the caliper, making the rotor surface hotter when it rotates back to the pistons closer to the trailing edge of the caliper. Therefore it helps if the pistons closer to the rear edge of the caliper are larger. Differential-bore calipers use smaller pistons up front, larger pistons toward the back.

HoveToo said:

Dennis,
Regarding mounting the disc on the right hand side behind the slider, the old commando service notes produced by John Hudson in the UK Norton Owners Club mentioned that when the factory did this originally, the bike pulled to the right. Moving the caliper in front of the slider on the LHS eliminated the problem. No one ever explained why, it just worked.

Click to expand...

Firstly, it wasn't John Hudson and the bikes didn't pull to the right, according to the 'Commando Service Notes'.
It was Mr T.R Stevens who wrote the majority of the 'Commando Service Notes' and in particular the story regarding the bikes pulling to the left with the caliper mounted behind the right hand fork leg. To be honest it sounds like a "bloke down the pub said" type of story. If it was the case, then I think without first knowing the accuracy of the frames etc one could not conclude it was purely due to the orientation of the caliper. I'm wary of 'word of mouth' stories, facts get easily misconstrued - as in the above quote for example.

There is a definite influence of whether the caliper mass is mounted in front or behind and has to do with gravity pulling its mass downward and there by causing fork to perfer to fall to one side on the other. It distance from fork affects how much leverage its gravity pulls on forks and the flip back forth rate of forks in a slapper too. You can explore this fact with a compliantly tri-linked isolastic which isolates everything - so does not mix up stuff to confuse what's goiong on in slight biais to drift one way or the other on level surface or tendency to climb a road crown. Biais ply vs radial ply also influence wether front tire tends to climb a crown or not. My SV650 is R/L mass balanced and dual rotors on front and also tends to climb road crown hands off. If ya are cleaver enough to build in some mass off set and tires off set bikes can be made to ride pretty straight on crowned roads but then tends to drift on the really level sections. C'do's tend to weigh more on the LH than RH so guess what that tends to do.