Gt 750 front brakes -Calliper axles “O” rings.

[Nicholasj]

Good evening all ; I was continuing with my restoration project today- the mission was to replace all the front brake hoses, and at one point I needed to move the bike.
Amazingly ( to me) I had a bit of a struggle to move a bike with no brakes. Further inspection revealed the R/F disc was binding.
Removed the calliper and split the R/H unit. The floating pad was immovable- there was crystallised brake fluid around the piston (stuck pretty solidly) and the actual pad was absolutely jammed in the hole in the calliper holder. I had to tap it out with my plastic head mallet.

The previous idiot had powder coated the callipers and not proved he had clearance for the pad to move in/out according to the brake lever’s wishes.
When I pulled the calliper axles they came out bone dry and the 2 small “O”rings were in pieces.

I’ve not been able to find out exactly which of the 4 grooves on the calliper axles these “O” rings are meant to be on.
I’m guessing it’s not the end grooves- but the two in between. If you numbered them 1,2,3,4 from the Allen head of the calliper axle: these would be 2 and 3.
My manual is not worth the paper it’s printed on: my CD Rom manual really only covers the “J” and the parts book merely shows there’s 2 “O” rings on the calliper axle and despite a lot of research I’ve haven’t found a definitive answer.
Is anyone able to provide guidance on this.
I have seen that some people are happy to omit these “O”rings and merely puts lotsa lube down the axle. Whilst others say that’s not what Suzuki intended.

This is pretty much my last task.
Well, once my new overhaul kits arrive.Easiest job last which is why I want to button up the brakes and finish the mechanicals.
My tank and sidecovers are at the paint shop and when they’re done I’m really hoping fitting them will be THE END of the road.
Any help will be gratefully appreciated.
Many thanks.

[gammakeith]

I ran my GT750 without the o rings on the brakes. I presume they have two functions. Firstly to stop water getting in and starting corrosion. Secondly they may also serve an anti-rattle function. Neither much of a problem.

Keith

[jabcb]

Manuals are here: https://www.oldjapanesebikes.com/mraxl_ ... /index.php

The parts manuals lists the o-ring count as 4 per caliper — one for each of those bolt grooves.
The diagram shows 2 but the parts count shows 4.

The separate Disk Brake Manual shows the bolt area that gets greased.

[Nicholasj]

Guys, thanks for the replies.
I never knew of the existence of the Suzuki Disc Brake manual.
And now I do.
Thank you to Ian Sandy.
Jabcb, now I now exactly where to grease the calliper axles- as per that diagram.
It’s a bit more area than I thought it would be, but no worries.
I still think there’s only 2 “o” rings per Calliper axle- a total of 4 “o”rings in a kit, but the kit is for the entire calliper which has 2 axles with 2 “o” rings on each.
Every rebuild kit I’ve seen only has 4 of them per calliper.
I’ll see how I go fitting them. If I need 4 per axle I’ve got a couple of “o”ring kits.
And now I’m thinking that the “o”rings go on the first and last grooves to control and retain the grease.

[jabcb]

Oops. You are right. Two bolts + four o-rings per caliper.

The portion of the bolt near the head sees no motion between the bolt & caliper — grease + o-rings wouldn’t affect performance.
(A bit of grease might make future disassembly easier.)

Only grease that’s needed is between the bolts & holders — the grease in that area is retained by the two o-rings & dust caps.
Insert a bolt into the holder. Likely will be obvious which grooves get the two o-rings.


Documentation written in the 60s & 70s is very different that what we get today. Rather lame by today's standards. And they didn't necessarily bother issuing corrections. Just part of the "fun" of having vintage bikes.

[Nicholasj]

Yes- I think we’ve all learned that about “old” stuff.
Funny, I don’t remember my750A being all that cantankerous.
Thanks for your help.
That really is worthwhile information.