Author Topic: Upgrade front end and twin disc brakes (Read 11971 times)

76supersport750F · « **on:** December 09, 2009, 11:19:38 AM »

Hello does anyone know of a year bike with dual disc brakes that would fit on a 76 750F.

I am looking for more braking.

Is there a better brake pads out there? Is there a better disc rotor with holes in it.

Thanks

michrobi · « **Reply #1 on:** December 09, 2009, 11:30:39 AM »

I might be full of #$%*, but I assume you could throw a set of 77 or 78F forks on that 76.

Don R · « **Reply #2 on:** December 09, 2009, 12:04:39 PM »

I don't have the lines connected yet but this is how I did mine. It was a trick modifying the little fender to work on the wrong side. I have a 75 wrecked parts bike and robbed the brake from it.
I drilled the rotors from a template I found here somewhere. The right coolant and lube makes all the difference. 96- 5/16" holes with 2 bits.
This is my 75F with 76F brake on the right.

eurban · « **Reply #3 on:** December 09, 2009, 01:20:02 PM »

This is a topic that has been gone over many times. Search for "dual discs" or "GL1000" front end form the Tech Forums page and you will have plenty of reading to do.

MCRider · « **Reply #4 on:** December 09, 2009, 01:36:01 PM »

As mentioned, gone over many times. But I'll give you my $.02. As you can see on my avatar, I've had duallies since way back in 1971.

You can convert the fork you have to duallies just by adding the parts and some simple machining. (I think you can. You can on the Ks anyway. Someone?)

An extra disc by itself does not give more braking. If one disc will lock the tire, what more can 2 do? (Also gone over in depth here). It can reduce fade, by spreading force out over 2 discs, so max braking can be applied more often (is that necessary how you ride?) And there is some added symmetry to the feel of the front end.

If you just want maximum one or 2 times braking improvement, consider an EBC rotor, EBC pads, braided lines, and a new possibly different ratio master cylinder. You'll get some more braking, some more anti-fade, better feel, without adding weight which is a negative you live with at all times, whether braking or not.

http://www.ebcbrakes.com/motorcycle_brake/index.shtml

http://www.ebcbrakes.com/motorcycle_brake/pro-lite_replacement_rotor/prolite.shtml

That's what I'm doing with my next project and bypass the weight and complexity of the second disc.

And there is also the "look" which is a valid consideration, in my book.

Also, your brakes will feel better if the fork is operating up to snuff. Fresh fluid, seals, springs, maybe cartridge emulators. And the whole bike performs better not just the brakes.

lordmoonpie · « **Reply #5 on:** December 10, 2009, 04:25:32 AM »

The old K series fork leg lowers and hangers can just be doubled up - they are reversible, you just need to swutch the caliper over and pull out the convex base disc in the brake line hole and you can even match up the lines and bleed nipples both sides.

I used K0 brackets and had to get a mirror image one machined but you can use K3-6 and I think the F model brackets just by flipping them over. If you're running a speedo, I think there are issues with the drive plate on a street bike but that's probably covered in the other threads.

I also had new rotors made in cast iron - much much better stopping power and thinner at 4mm brand new but very expensive. You can get these from cat engineering in the UK (use google) and they have a zinc treatment process so they don't rust up in the rain any worse than stock discs. If you want pictures, go to the ultimate engine thread in HiPo forum and flick through...

The_Crippler · « **Reply #6 on:** December 10, 2009, 05:31:31 AM »

Quote from: MCRider on December 09, 2009, 01:36:01 PM

An extra disc by itself does not give more braking. If one disc will lock the tire, what more can 2 do? (Also gone over in depth here).

It might have been gone over in depth, but I hadn't seen that little nugget before. Good call. Hadn't thought of it like that.

Quote

If you just want maximum one or 2 times braking improvement, consider an EBC rotor, EBC pads, braided lines, and a new possibly different ratio master cylinder.

The EBC items you mention...those just for 750s, or do they have stuff that will work with the 650s? Also, could you point me in the direction of something that will explain more about the MC ratio? I did not realize that the MC did much more than just hold the brake fluid.

Don R · « **Reply #7 on:** December 10, 2009, 10:30:33 AM »

The photo is a 75F, I guess I wasn't clear. They have a larger piston than the earlier K. The caliper with the fittings in the center match I think they were on early f, 75-76 or k, 77-78. I believe the brackets are the same once you get past the early style fork.

MCRider · « **Reply #8 on:** December 10, 2009, 10:49:53 AM »

Quote from: The_Crippler on December 10, 2009, 05:31:31 AM

Quote from: MCRider on December 09, 2009, 01:36:01 PM
An extra disc by itself does not give more braking. If one disc will lock the tire, what more can 2 do? (Also gone over in depth here).

It might have been gone over in depth, but I hadn't seen that little nugget before. Good call. Hadn't thought of it like that.

Quote
If you just want maximum one or 2 times braking improvement, consider an EBC rotor, EBC pads, braided lines, and a new possibly different ratio master cylinder.

The EBC items you mention...those just for 750s, or do they have stuff that will work with the 650s? Also, could you point me in the direction of something that will explain more about the MC ratio? I did not realize that the MC did much more than just hold the brake fluid.

Yes the discussion here was quite lengthy involving engineers and formulas and everything. Essentially, your MC puts out X amount of PSI and whether you funnel that into one caliper or 2 or solid discs or holey ones, that's all you've got to work with. YOu can improve the feel and progressivity and all sorts of esoteric characteristics, but...

On that EBC link if you navigate around there is an applications guide. Or just call them.

I've been lucky in that when i built duallies, i just went to the junkyard and got MCs I thought were off of dual brake bikes and they always worked great.

I have heard some hear complain that they had got an MC either new or used with a ratio that made the brake feel very hard and non-progressive. There are also charts around somewhere saying what our ratios are and what is optimum.

EBC says their rotor is 18% stickier and with their pucks you can actually improve the totla force without a MC change. I'm looking forward to trying.

But we still have the issue, if one system can lock the tire, how does a newer system make it better? Well, that would be with a wider and better tire.

MCRider · « **Reply #9 on:** December 10, 2009, 11:18:36 AM »

This is a good thread on Master Cylinders. Has links to the XS650 site which has manymaster cylinders. And about halfway down discusses an eBay item many have had good luck with.

http://forums.sohc4.net/index.php?topic=28649.0

Just search on master cylinders and you'll get tons.

The_Crippler · « **Reply #10 on:** December 10, 2009, 12:25:42 PM »

Quote from: MCRider on December 10, 2009, 11:18:36 AM

Just search on master cylinders and you'll get tons.

Well, that would be the problem, wouldn't it.

People always say that, but some don't realize that this is information overload sometimes. 50,000 thread and no idea where to start, what's BS, what's superfluous and what's what you're loking for - Thanks for pairing it down for me above and giving me a plave to start.

lordmoonpie · « **Reply #11 on:** December 11, 2009, 04:35:24 AM »

Or just go for an AP racing classic master cylinder as a replacement. period looks, modern manufacturing, awesome performance! You'll be doing rolling stoppies before you know it

fishhead · « **Reply #12 on:** December 11, 2009, 04:55:43 AM »

A GL 1000 Front end (75-77 has 6 bolt brake discs, 78-79 has 5 bolt brake discs) is a great upgrade for the CB 750 and bolts in place. You will need to make steering stops and modify the gauge mounting bracket to use the CB gauges. The stock GL brakes are fine when used with a 5/8 inch master cylinder.
Braking power and braking feel go hand in hand. Most motorcycles can lock the front brake, even with a single disc. Braking feel and modulation (having usable brakes- not "on and off" front brakes) goes a long way in installing braking confidence. Knowing you brakes will slow you down and slow you down in a predictable manner, repeatedly, is what "better braking" is all about.

I take my brakes (butchering?) to extremes,1975 GL 1000 front end, dual 330 mm discs and Tokico 6 piston calipers.

Yoshi823 · « **Reply #13 on:** December 11, 2009, 01:24:08 PM »

This is the setup on my 550F1.I just used standard bits except the disc mount bolts and some Aeroquip hydraulic lines.I had Ferodo pads on one disc and Vesrah on the other,so that it had the effect of double disc in the dry and single in the wet....not that i'm saying that Vesrah pads don't work in the wet, but......

fasturd · « **Reply #14 on:** December 11, 2009, 05:49:36 PM »

I have to say (again, lol I have said it before) That a properly working CB750K single front disc is all one needs IF it is working properly.

Rebuilding the calipers AND master cyl. or better yet getting a modern 14mm nissin master has worked great for me.

The last Cafe bike I did had a drilled stock disc, rebuilt caliper and the Nissin 14mm master and It had great feel and I could watch the fork bend under load.

Dual discs look great. But they are HEAVY and in my opinion do not offer an advantage in normal and even heavy street riding.

I have another 750 with duals and it looks cool but I swear I can feel the weight when cornering that bike.

Don't get me wrong. I am not saying a single disc is better than duals. I for instance would not remove one of my ZX12Rs discs just to save a little weight. BUT The modern bike has much stiffer forks, MORE tire contact patch AND MUCH better calipers. Modern discs are MUCH lighter in fact I wouldn't be suprised if my entire ZX12 set up doesnt weight less than the single disc CB set up.

So, I would stick to building a strong single disc before I bothered with a dual.

Just my opinion...

PS fish guys dual disc set ups are the BOMB and if my GL1000 project ever gets back together his front set up is on my list.

bucky katt · « **Reply #15 on:** December 11, 2009, 09:43:22 PM »

are those iron ebc rotors really worth the price? and are they made to fit on a k4-k6 front end

Retro Rocket · « **Reply #16 on:** December 11, 2009, 10:10:34 PM »

Quote

Dual discs look great. But they are HEAVY and in my opinion do not offer an advantage in normal and even heavy street riding.

I would have to disagree with that. I have put twin disc setups on all my Honda 4's and can guarantee that twin discs are far better for brake performance than just one disc. I have always ridden my bikes fairly hard and notice, not only more braking power but better resistance to fade, they may both lock up but thats not the point, its how fast you can stop without doing that and twin discs will always do it better. Yes they are heavier but i have more confidence in riding my bike hard with twin discs....

Mick

Zaipai · « **Reply #17 on:** December 11, 2009, 10:14:22 PM »

I have had enough parts for 2 discs, however felt that the extra weight vs braking power was not worth it.. Now you have me rethinking that. I will have to look into that. Oh the other thing that stopped me was what to do with the speedometer cable... Time to go do a search..

Good post..

Don R · « **Reply #18 on:** December 11, 2009, 11:15:05 PM »

The speedo cable isn't that hard. I didn't really get the posts when I read them but once I had it apart it was obvious what to do. I did my K0 lester wheel one way, (pinned to the hub) and my F0 by cutting and bending the tabs over the flats on the rim.
Duals are like a getting supercharger, it's just too cool not to do it.

ev0lve · « **Reply #19 on:** December 11, 2009, 11:19:42 PM »

Quote from: Zaipai on December 11, 2009, 10:14:22 PM

the other thing that stopped me was what to do with the speedometer cable...

Maybe I'm not understanding but if you mount the calipers up front of the forks as stock you should be able to use the same routing as stock.

If you swap them to the back of the forks you'll either need to turn the fender around or re-rivet the fender to the bracket so it stays in the same orientation otherwise the hanger will be on the wrong side.

I turned mine around but wish I'd modded the bracket in retrospect.

Retro Rocket · « **Reply #20 on:** December 11, 2009, 11:55:34 PM »

Quote from: Zaipai on December 11, 2009, 10:14:22 PM

I have had enough parts for 2 discs, however felt that the extra weight vs braking power was not worth it.. Now you have me rethinking that. I will have to look into that. Oh the other thing that stopped me was what to do with the speedometer cable... Time to go do a search..

Good post..

Remember this all depends on how hard you ride, i am a late braker and like the brakes to carry deep into the apex.this may not be what you want . And yea i have had my fair share of crotch rockets as well but i get a buzz out of riding these old bikes hard when they are set up well and wouldn't ride as hard without the twin discs. The extra disc would obviously add more weight but i don't think the extra centrifugal forces created make much difference, not on the street anyway..

Mick

Don R · « **Reply #21 on:** December 12, 2009, 10:43:52 AM »

Iggy, it isn't so much the cable routing it's how to get the drive to turn it after you remove the chrome drive plate to install the rotor.

ev0lve · « **Reply #22 on:** December 12, 2009, 10:58:22 AM »

Quote from: Don R on December 12, 2009, 10:43:52 AM

Iggy, it isn't so much the cable routing it's how to get the drive to turn it after you remove the chrome drive plate to install the rotor.

On the K models it's trim down the drive and bend the tangs over - MCRider has some pics of all the drive units up here.

It's pretty well documented here on the board.

754 · « **Reply #23 on:** December 12, 2009, 11:22:14 AM »

Yoshi, you dont see many triple discs like in your pic.

For the guy that said he had the parts, put it on without speedo drive, and fender, if you dont like em, take em off.. I bet they will stay on , then you can finish speedo drive, fender, etc...

Zaipai · « **Reply #24 on:** December 12, 2009, 05:09:34 PM »

Ok I believe I will give it a try, I have both disks, and both calipers and the break line.. I was thinking I may just try the MC from the basket case 82 VT750 I have since it still works, and the T I need to split the line so both brakes have a hydrologic line. To be honest I don't ride it that hard and really just love the way twin brakes look over a single disk.. So it really did not take much convincing to get me to do it. I would like the disks turned down and drilled at some point, but that will have to wait till next year I am afraid as money is going to get tight here.. But that's ok..

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Author Topic: Upgrade front end and twin disc brakes (Read 11971 times)

76supersport750F