Topic: Front brake upgrade for my racer

[Hot500]

I'm starting out to build an historic racer from an SL350. The front end is cb500 and I will be upgrading the brakes with a AP racing caliper and 300mm disc.

I've searched out a few threads on here where guys have done this upgrade, but I can't find any threads that tell me where to purchase a 300mm disc. All of the 350 racing sites I've found who sell heaps of go fast goodies make no mention of 300mm disc either.     Brembo would seem to be the logical choice but oppracing does not specify bolt pattern or model fittment for their 300mm X 5mm disc.

A part number would be most helpful. 

Any help mucho appreciated.

[turboguzzi]

welcome to the RR club, good to have you on board. bwaller and me use early suzuki discs in our bikes which are a nice upgrade, they are almost a bolt on. not easy to fit after market calipers to 500/4 forks,  bracket is pretty fancy, davies motorsports in uk might sell it. there should be pics in my build thread as well as bwaller's or on the DM site.

[Hot500]

D-M Engineering sell the adapter plate and a spacer for a 300mm disc, but dont sell the disc.

What size are the suzuki discs you're running. When you say 'almost' a bolt on, are the bolt patterns the same and are the stock Honda bolts long enough. Would a 295mm be ok with the AP caliper.

I'll check out those build threads. Thanks.

[bwaller]

The Suzuki rotors are 274mm. You could work over a CB750 disc, they are 295. Thin it, slot it, drill it, to reduce weight......or keep looking for something else!

[scottly]

The 750 rotor will bolt right on to the 500 wheel, but you will also need to use a 750 caliper and it's mounting arm. I have some Yamaha 300 mm rotors on my 750; the bolt pattern is the same, but the center hole is larger than the Honda, so I made spacers.

[754]

Ducati rotors will fit the 6 hole hubs used on 450 and bigger.. (not the 350G hub)

[turboguzzi]

The 750 rotor will bolt right on to the 500 wheel, but you will also need to use a 750 caliper and it's mounting arm. I have some Yamaha 300 mm rotors on my 750; the bolt pattern is the same, but the center hole is larger than the Honda, so I made spacers.

interesting, 300mm's off what yamaha?

[Chris Tyler]

Hi

Look for a website called John Sunter Honda
http://www.sunterhonda30.co.uk/
John machines the fork leg for a plate for the Lockheed he does them to suit standard or 750 discs. There is a spacer for the hub. I dont know what other models he does as they are K4 350 twin parts.
The Davies & D & M adaptors are a plate made to fit with no machining.

Again I dont know if they do twin discs but the 500's are the new class!

Chris

[scottly]

TG, I don't know what model of Yamaha the rotors came from: my buddy picked up the wheel at a junkyard in the late '80s for a project, and never used it. They are about 2 pounds lighter each than stock 750 rotors.

[Hot500]

Yep, I was aware that the Ducati and Yamaha disc had the same hole pattern. I wonder how the offsets compare to the honda rotor?

I've had an email from Dave at D&M Engineering. They will have the disc made up to customer specs depending on what hubs and legs are being used. 125 English pounds per disc. Quite reasonable I think.

[turboguzzi]

TG, I don't know what model of Yamaha the rotors came from: my buddy picked up the wheel at a junkyard in the late '80s for a project, and never used it. They are about 2 pounds lighter each than stock 750 rotors.

neat, but these dont look like 300mm...   I could be wrong of course, looks can be deceiving

[scottly]

Ok, it seems they are only 298mm. The offset is slightly less than the Honda, so the spacer/centering ring I made was about 1.5mm thick, if my memory is correct. Here is a picture of the left side spacer, and one of the wheel the rotors came from:

[turboguzzi]

ok, now i see its the 19" wheels that caught me out. I have 300mm-ers in my gpz and with 18" rim they just "fill the gap" better....

surely wouldnt spot a 2mm diff in a pic at my advanced age !

[scottly]

Ha! And here I was about to start calling you "Eagle Eye Guzzi".

[Roach Carver]

marked!

[754]

Here is a VTR rotor and caliper mounted to 6 bolt Honda hub on a 750F fork..

[turboguzzi]

Here is a VTR rotor and caliper mounted to 6 bolt Honda hub on a 750F fork..

nice try but dont think that floating discs and modern calipers are allowed in the classes that a 350 can be raced in...

[lordmoonpie]

You want to talk to those nice people at ISR brakes. They will make you discs of any diameter, any hole spacing or offset and they can make you them in fully floating modern styles right through to old fashioned classic. Very well made and good prices for custom items.....google them and you'll find all your heart desires ;-)

[Hot500]

Here's one for the experienced racers. If your racing with a single disc front, is there any benefit in having the rotor on one side as opposed to the other. i.e. if racing on a predomanantly left hand circuit, is there anything to be gained or lost by having the rotor mounted on the left side of the wheel.

Hope that makes sense.

[trueblue]

Is there any ruling in your class stopping you from running dual rotors up front?  I'm currently building a CB350 twin and I'm using Morris mags with dual CB500T rotors which are 275mm.  To provide the squeeze I'm using CB900 twin pot calipers and an R1 master cylinder.

[Hot500]

Yes, unfortunately the major components have to be faithful to the period, i.e. in the case of the Honda 350T that means rear hub, single disc.

You can upgrade these components with modern parts, materials, make them bigger, better, faster etc but if the original model did'nt have it, neither can you.

[trueblue]

That's ok, I just thought I would throw out another opiton for you in case you could use it .

[madScientist]

subscribed

[bwaller]

I imagine by some degree there would be an effect (at least the weight factor) of having the rotor/caliper mounted on the left leg for a circuit with mostly lefthanders, but I doubt most of us would ever feel the difference. If you trail brake into the corner it'll likely try to straighten the bike up whether it's mounted left or right.

[Hot500]

I was looking for a 500 front hub for my racer and a mate knew an old bloke with lots of 500 parts laying around.....so over we go to old mates place and he has a complete front end, triples, forks, hub, wheel, disc.....$100 the lot...

My mate Dave (forum member Dave500) looking at the hub says, hey that speedo drive is on the wrong side. I didnt think anything about it at the time as the wheel didnt have a disc on it I knew the hub had been dismantled and shoved back together, but everything was there, so no big deal.

Couple days later when I get a chance to look things over I find out why the speedo drive was on the wrong side.

It was hiding this:




Some #@%%*head had taken to it with a grinder    Seems they couldnt get the dust seal out and thought, I know, I'll grind it out.

Anyhow turns out the old bloke doesnt know have the stuff hes got and didnt realise the hub was rat#$%*. I pick up another hub from him on wednesday.