This piston must need replaced?

[Oddjob]

It's interesting to see these comparisons between the old style braking systems and the new but one thing no one has deemed to comment on is that most of these modern bikes have ABS, that trades off braking distances for control, so whilst the braking distances may be roughly the same the modern bike will do this far more safely, in that it isn't all about the riders skill or experience in braking, ABS tends to smooth out that skill curve, even a novice can get some reasonable figures. Whereas a novice on an older braking system without ABS would be hard put to match an experienced rider.

The other main difference is that the modern bike can do far better braking distances when the speed rises, a comparison between the distances at 90mph for example would most likely show the distances are very far apart in results. The modern bike can also do it more repeatedly, it's far better at shedding heat and has generally a greater tyre grip patch due to the much wider tyres.

On a comparison note, when my first 1300 was written off I was just setting off from standstill when someone pulled across me, I didn't spot them immediately as I was looking at the traffic coming from the left in case they jumped the lights, when I did spot the car I immediately did a full emergency stop, the front brake went straight into it's ABS mode with it chattering as it tried to stop the tyre loosing grip, I was able to steer away from the car to some degree and IF the car driver had seen me it's possible the collision would have been avoided or lessened at least but of course she didn't see me. Now if that had been on say my 500-4 the first thing that would have happened is the front tyre would have locked up, the road was wet and it's possible the brake would have not worked for a sec or 2 as well whilst it shed water, I'd have had little control if any and would almost certainly have hit the car much harder as a result and further back, somewhere around the firewall I'd imagine, whereas by being able to steer under ABS I actually got around the front of the car and she plowed me under with her bumper. Saying that it's also possible the the differences in acceleration between the 500 and the 1300 might have meant she could have cleared the junction before I even got there 

It's a shame we can't have the option of retro fitting ABS to the SOHC bikes, it would be interesting to see how the brakes compare in real life tests. Although I am aware that might upset some people, I know of riders who really hate ABS for some reason.

[Mikep328]

I completely agree

Back when ABS was being introduced on bikes many riders said they could outbrake ABS and on a dry track with a fixed brake point, good riders can (and did) do that.  But in the real world on real roads with REAL random and sudden "panic" moments, there's no way!"  ABS is a great thing!  I wish there was an unobtrusive ABS system that could be fitted to vintage bikes.  I'd install one on my 400 (and my Norton Commando) in a heartbeat.

[TrickyMicky]

Y'know, if you want/need gut wrenching brakes with ABS, allied to super grippy fat tyres, then why on earth do you want a vintage bike? 

[Johnny4428]

Actually if you can lock the front with a single disc, (which I know you can), it begs the question the benefit of fitting a double disc setup, or am I missing the point?
I’ll get me coat!🫣🫣

[Mikep328]

Y'know, if you want/need gut wrenching brakes with ABS, allied to super grippy fat tyres, then why on earth do you want a vintage bike? 

 Good question!   

While I have no need for brakes/tires that can perform stoppies, brakes that won't lock up in the wet is a nice thing to have in an emergency.   I use my two vintage bikes as daily riders and, IMO, ABS would be a worthwhile "safety feature" in modern traffic.  I'd be fooling myself if I claimed that despite many years of riding (and racing in my younger days), I could modulate the brakes/stop as effectively as ABS can.  Of course, what I'd like and what exists are two different things so my vintage bikes will remain ABS-less! 

[Laverdaroo]

Actually if you can lock the front with a single disc, (which I know you can), it begs the question the benefit of fitting a double disc setup, or am I missing the point?
I’ll get me coat!🫣🫣

Cos twin discs look ‘the shizzle’ and balance the front end a bit in terms of looks IMO. Plus it’s more bling to dazzle the chicks outside the all girls school bus stop when you rumble by looking all macho
Each to their own. I disconnected the abs on the VFR for a while a few years back and the brakes were no where near as good but like I say, each to their own and soon rigged it all back up again and to be fair, EBC discs, carbon Lorraine sintered pads, braided lines and better levers, they bloody should be


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[Rozabikes Tim]

Actually if you can lock the front with a single disc, (which I know you can), it begs the question the benefit of fitting a double disc setup, or am I missing the point?
I’ll get me coat!🫣🫣

 Plus it’s more bling to dazzle the chicks outside the all girls school bus stop when you rumble by looking all macho

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I do hope we are talking back in the day and not last week Roo. That would be wrong! 😱

[K2-K6]

To the original question....the stainless piston option is a good one. Experience on here is that they are well made and work well.

As Bryan has already contributed, the seal, its groove, how clean that is, are one of the most crucial aspect of getting this (and any caliper) to work correctly.

They should be assembled with silicone grease (it's directed even in the very first 750 Honda manual) to work well and protect it from corrosion.

The seal on a single piston caliper must retract the piston to give running clearance for BOTH pads (the static side on this is assisted in keeping the pad off the disc while running, but needs the seal to "give" initial clearance) and makes a big difference to how effective the brake is..you should be able to feel the free piston go out when lightly squeezing the lever, then definitely retract as you let the lever go. If it doesn't do this (that's about 0.4mm) a very visible retraction, then either the groove is not clean or the seal is not toleranced correctly. 
It may be of use considering the genuine Honda seal IF you dont get that retraction correctly established.

[Oddjob]

Actually if you can lock the front with a single disc, (which I know you can), it begs the question the benefit of fitting a double disc setup, or am I missing the point?
I’ll get me coat!🫣🫣

 Plus it’s more bling to dazzle the chicks outside the all girls school bus stop when you rumble by looking all macho

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I do hope we are talking back in the day and not last week Roo. That would be wrong! 😱

And you would be wrong Tim, he meant last week. They don't call him Flash for nothing. The St Trinians character was based on Roo.

[TrickyMicky]

Actually if you can lock the front with a single disc, (which I know you can), it begs the question the benefit of fitting a double disc setup, or am I missing the point?
I’ll get me coat!🫣🫣

Cos twin discs look ‘the shizzle’ and balance the front end a bit in terms of looks IMO. Plus it’s more bling to dazzle the chicks outside the all girls school bus stop when you rumble by looking all macho Interesting image Roo, but in my REAL world, as I pass the girl's school, adorned in my XXL wax jacket and a pair of leather jeans that were too small 10 years ago, I don't think that even a second disc is going to improve my chances. Unless of course the latest fashion includes the grey Gaffa tape holding my left boot together!  Stay safe and upright everybody.
Each to their own. I disconnected the abs on the VFR for a while a few years back and the brakes were no where near as good but like I say, each to their own and soon rigged it all back up again and to be fair, EBC discs, carbon Lorraine sintered pads, braided lines and better levers, they bloody should be


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[Eldrick]

To the original question....the stainless piston option is a good one. Experience on here is that they are well made and work well.

As Bryan has already contributed, the seal, its groove, how clean that is, are one of the most crucial aspect of getting this (and any caliper) to work correctly.

They should be assembled with silicone grease (it's directed even in the very first 750 Honda manual) to work well and protect it from corrosion.

I noticed that the Haynes book suggests smearing the piston with Brake Fluid before inserting back into the caliper body. Is the  silicone grease a better choice or is there a good reason to use it?
Thanks

[Bryanj]

Nope and nope

[K2-K6]

To the original question....the stainless piston option is a good one. Experience on here is that they are well made and work well.

As Bryan has already contributed, the seal, its groove, how clean that is, are one of the most crucial aspect of getting this (and any caliper) to work correctly.

They should be assembled with silicone grease (it's directed even in the very first 750 Honda manual) to work well and protect it from corrosion.

I noticed that the Haynes book suggests smearing the piston with Brake Fluid before inserting back into the caliper body. Is the  silicone grease a better choice or is there a good reason to use it?
Thanks

They have absolutely no weather sealing on these caliper, the silicone grease excludes water from piston seal to effectively do this function.

Silicone grease is highly hydrophobic (near zero water attractive) with brake fluid the opposite in it's vulnerability to water ingress. Combine this with any available salt from road use gives effective electrolyte solution, causing the corrosion you've already got in the old piston.

Silicone grease is advised in the original Honda (first product disc brake really) and very effective.

It's your choice, but I use it on all caliper builds.

[McCabe-Thiele (Ted)]

I used Silicone grease when fitting the seals & pistons, I also use Silicone brake fluid.

[Mikep328]

I had a poor experience with silicone (DOT 5) fluid a few years back when I tried it in my Ducati 996.  The lever felt spongy and no amount of bleeding, etc would eliminate it.  Went back to DOT4 and the brake returned to normal.  I realize that liquids are not compressible and that DOT 5 is the spec fluid for some brake systems but I couldn't get it to work well for the Ducati.  Might have been my own incompetence in some way but as the old saying goes, "Once bitten, twice shy."