SMC Info - 2008 Onwards

[jfheath]

Some close up photos of a brand new SMC for 2008 models and later - including the measurement for the refitting of the plunger bracket.




Above:
In this photo, the rubber boot is pulled to one side to reveal the retaining circlip and washer. This is brand new, I am surprised that there is not a smear of silicone grease in there.
Note the groove on the right hand side of the hole in this photo. This is the channel to allow any water that collects in the opening on top of the rubber boot to drain away. It is important that the boot is properly seated - it must not block that drainage channel.





Above: The SMC push rod is fully extended to measure the length of the extended plunger. This measurement is critical. The manual is very clear about not unscrewing the bracket from the plunger shaft. But if you do, I suggest that you take your own measurement first. I have had no success in removing the circlip without unscrewing this bracket.

I should add that I have only ever tried thion the ruined SMC that features in other threads.



Above: On this brand new SMC for a 2008 onwards model, the measurement is 3.678cm. Do not use this photo to read the top inches scale - the inches scale on my Vernier caliper is incorrect when at zero.





Above: The inlet and outlet port are plugged with plastic caps to prevent debris and moisture from getting in. Remove this before fitting the banjo bolts.



Above: another view. Note the silver retaining clip in position - above the top right corner of the part number label. The SMC is supplied with this. The manual doesn't mention this, but in the section on fluids and lubricants, there is also a glue specified for keeping this clip in place.

 

[Lowndes]

EXCELLENT photos and write-up!!

Thanks!!

 

[Obo]

Thanks for the info. So what's the main difference between this and the pre-2008 model?

 

[Igofar]

The models up to 2007 had smaller, shorter caliper bodies, thus a shorter SMC bracket that attaches to the fork leg.
From 2008 up, Honda used a one piece design (cast unit) instead of the old clam shell design, and in doing so the had to make it larger.
This is the reason the 2008 and newer have longer brake pads. They also have an 8 mm head on the pad hanger pins instead of the 5 mm allen style.
Thanks for the Photo's John.

 

[jfheath]

Purely from the SMC point of view (ie the master cylinder part of the bracket) - I am not too sure about the precise differences. The drainage groove was introduced before 2008, but I think that this one is slightly longer. Or my memory is fading. The piston itself has changed design over the years - this one has its primary seal attached to the return spring rather than attached to the piston body. But of course, you cannot see that from the outside. The service kit which includes the piston, plunger, rubber boot, spring and seals is a different part number - so the length, stroke, diameter of the piston may be different - so that measurement shown above may be different for pre-2008 models.

Although this SMC unit will fit the earlier fork legs, the 2008 and later model is designed to accept the slightly larger calipers. Pre-2008 SMCs are not interchangeable with Post 2007 SMCs.

(I see @Igofar has just posted some of the above - morning Larry !)

I have added some more detailed captions to the photos.

 

[Igofar]

Morning John! I found some of my older pictures of the design differences.
The new one uses a slightly longer spring, that is smaller in diameter as well. As John said the skirt is now attached to the spring. I believe this allows the piston to move around a bit and self center rather that having the spring attached to the piston and push it.
If you look closely, you'll see wear marks on the fins showing that the skirts gave up and allowed metal on metal contact. The old style one in these pictures has over 100,000 miles on it, and the brakes were flushed yearly, the newer style, if I remember correctly (poor memory) only had approximately 23,000 miles on it and was only flushed every couple of years or more (garage queen).
I'll also include pictures of both brackets.
There is also a picture of an old style one where the boot was destroyed (possibly by a mityvac bleeding) it was found turned inside out when taken apart.

 

[Upt' North]

Purely from the SMC point of view (ie the master cylinder part of the bracket) - I am not too sure about the precise differences. The drainage groove was introduced before 2008, but I think that this one is slightly longer. Or my memory is fading. The piston itself has changed design over the years - this one has its primary seal attached to the return spring rather than attached to the piston body. But of course, you cannot see that from the outside. The service kit which includes the piston, plunger, rubber boot, spring and seals is a different part number - so the length, stroke, diameter of the piston may be different - so that measurement shown above may be different for pre-2008 models.

Although this SMC unit will fit the earlier fork legs, the 2008 and later model is designed to accept the slightly larger calipers. Pre-2008 SMCs are not interchangeable with Post 2007 SMCs.

(I see @Igofar has just posted some of the above - morning Larry !)

I have added some more detailed captions to the photos.

Good morning John,
Honda went to a lot of trouble to change the braking system on the 13 in 2008 when it was already an ageing motorcycle with ever stiffer competition. The reasons are obvious to all and I'm sure the feedback from riders and dealers required some action for what is a serious issue and one with potentially substantial consequences.
Do you think the changes made any real differences with regards maintenance requirements, braking performance, ease of maintenance etc; was it successful?
Do you know if the new SMC was used on other Honda's or not, was the change designed for the 13 or was it just adapted from another model in the range at that time. Was it hanging around in the Honda parts bin.
I'm guessing (probably wrongly) that you have had an issue with the 08> SMC hence the new one in the pictures, but maybe not.
Upt'North.

 

[jfheath]

That is a nice side by side comparison that I haven't seen before. So I played around with your photos a bit. The photos are from slightly different angles, but the two made roughly the same size and one superimposed on the other. I've aligned the pivot hole (bottom right) and the two circular mouldings at each end of the SMC (top and bottom left). It brings out the very big difference in the location of the caliper slider pins (the two holes on the top side of the photo).



Morning Ray

The VFR and Goldwing have SMCs that I know of - the VFR that I looked at recently looks very similar in design, but I doubt it is identical.

The calipers had another modification to the pad spring - it is an assymetric design and it is impossible to put it in the wrong way round - so that may have been an issue - but not enough of one to change the design of the rear caliper. The horse-shoe cutouts on the inboard side of the caliper are now in place to allow the pistons to be removed - since there aren't two halves to separate.
It is, however, possible to get the pad spring trapped in front of the a piston when putting in new pads. When the pads are worn, the pistons are pushed out slightly and this isn't a problem.

I had problems with what I thought was an SMC issue on my older A6 model - lots of movement on the plunger it and it would rattle. That was when I started looking at the places that air could hide in the system, and how it was that I was getting no air out, but the SMC was still doing this. I got it all sorted out and restored my brakes to correct operation - and then I traded the bike in for my current new one.

I bought the new post 08 SMC because I was concerned that as I reached the same mileage, the same might happen, and although the bike was manufactured in late 2013, the model is an A9, and the design was getting near to 10 years old. I had this notion that manufacturers continue to supply parts for up to 10 years - I wanted one in stock before they became unobtainable. That notion is wrong. They stop making parts when they feel like it, apparently. Then I thought it was silly to have a bike with an old SMC on board and a brand new SMC sitting doing nothing, so I fitted the new one. The old one, I took apart and gave it a good check over and clean. Perfectly OK. No sign of wear, corrosion, distortion. By this time, I had already sorted out for myself how the brake system worked (with many discussions with Anna'sDad and Igofar and one or two others on here - it seemed that we were all learning stuff at the same time - me more than most as much of this was relatively new to me). I formed the opinion that the servicing and proper bleeding to purge all of the old fluid was the key to keeping things working properly. I keep reading threads, and most problems I have seen could be explained by an unknown service history.

Although I do note that the base on which the retainer clip sits is wearing down on my rear caliper bracket. Recently, I also noted that a glue is specified in the oil and lubricants list in the front of the manual for that part. Mine isn't glued in place. But I need to keep an eye on that.

There were other changes to the calipers and brackets. On the right hand side, they modified the front wheel ABS pulsar ring to a slotted steel design - which meant that the sensor had to face in towards the wheel rather than pointing down onto the previous castellated cast ring. So the bracket on that side has a different mount for the ABS sensor attached. I don't think the parts were just lying around, I think that they are newly cast for the ST1300. That 2008 design covered a lot of improvements, including changes to the ECM which made the engine more grunty, particularly at pulling away and tight uphill hairpin speeds. I don't know what the difference was with the 2009 model.

My own feeling is that there was nothing wrong with the original design of the SMC. But it required people to do certain things in a particular way - clean the drain hole, flush the fluid, if a service kit is used, silicone grease should be applied to the plunger and 'ball joint' area that moves inside the bore. I suspect that in many cases, shortcuts have been taken, and not just by the home mechanic. If fluid is left unused for a long time, you can expect a downturn in performance - but should you expect sudden locking of the rear wheel ? I think some modifications were made to try to address issues due to incorrect servicing. Although the reason for the change in design of the SMC piston is beyond me. Without two seals, I reckon that the piston will make metal on metal contact much more, and I guess that the bore would wear down faster , so I don't understand what that was supposed to achieve.

Binding rear brakes ? I have had those, but it was due entirely by me being over-generous with the silicone grease inside the holes in which the slider pins move. Air pressure put the pads in contact with the disc surface. Generated heat did the rest.