Author Topic: Front brake service / set up 400/4 advice please  (Read 5369 times)

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Re: Front brake service / set up 400/4 advice please
« Reply #15 on: November 25, 2016, 09:16:36 AM »
I think it's a measure of how people are willing to approach things on this site that you can discuss areas like this. On some car sites it'd be met with a rider of not working on critical things like brakes and advising to only buy and replace components.

Agree with you Trigger,  I was wondering after posting if I should've covered more of the system. So at the risk of boring everyone I'll make some additional points.

Quite often people assemble the caliper by using brake fluid to ease the piston past the seal but this leaves fluid on the outside of the seal which doesn't protect it. The caliper should be clean and dry, use the brake system grease to lubricate the seal and the piston should just push in with your fingers. When you then fill the completed system,  the fluid is only on the correct side of the seal and helps to avoid corrosion.

The master cylinder is obviously another part critical to decent operation. The seals there have different functions which are not readily observed. When you first start to move the lever the fluid will try to go out via the easiest route from the piston chamber,  this tries to exit into the reservoir. The first seal operation is to close off that route and if the part of the seal that completes that function is impaired then more of the lever stroke is used before the brake line is pressurised. The seals when they get older and less squishy just don't do that so well, they get there but the lever travel is long as the seal requires the line pressure to build up as it's closing to assist 100% closing. This results in the lever coming too close to the bars and a critical feeling of delay to the rider.

The hole into the reservoir is also an area to look at. If it's partially blocked then two affects are possible, when you release the brake after use the hole is opened to allow the reserve fluid to refill any space in the brake line that has been created by pad wear. It's this aspect that makes disc brakes essentially self adjusting (discounting the screw adjust on the Honda caliper) and resets the lever position each time to give a good lever feel. It also makes the system hard to blead as quick replenishment of the line doesn't take place with the fluid in the line just being pushed down and then pulled back again as you release the lever.
Second effect is that the hole is mostly blocked and as a bit of heat comes into the brake system during use,  then the fluid can't expand anywhere so the pads are held against the disc and more heat is created (you often see this on rear disc brake systems as they are just not used at the frequency of the front) this will if not corrected end up looking the brake on.

Piston material in the caliper has an impact on longer term use as well. The corrosion of piston and bore is mostly caused by galvanic reaction ( one material electroplating from another when submerged in an electrolyte solution) in this case the electrolyte solution would be salt water. Even if you use a stainless steel piston the two materials still appear with a difference on the galvanic scale which doesn't stop the problem. There are I believe phenolic resin pistons available for these calipers which are obviously not metal so long term use of this type I think should be considered two best look after the original caliper material.

If you use them all year round and expose them to salty roads then you are probably looking at a strip down every 24months at a guess. This is alot of calipers nowadays have an additional seal outboard of the main one to keep that area as clean as possible.

I know they won't match modern systems for braking power but set up as intended they are alot better than most people indicate.

Offline RGP750

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Re: Front brake service / set up 400/4 advice please
« Reply #16 on: November 25, 2016, 10:11:36 AM »
Great info again thanks.
Yes agree a great site and so much can be gleaned from it.
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Offline tom400f

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Re: Front brake service / set up 400/4 advice please
« Reply #17 on: November 25, 2016, 12:38:48 PM »
K2-K6 - thanks for that. I agree (and with others) the complete system is important. Not least you don't waste time/fluid addressing things separately.

As regards caliper lubrication - I intend to refurb  one of my vfrs all round and will use red rubber grease. Also interested in going with silicon fluid, so flushing technique for removing the old stuff completely is welcome.

EDIT: perhaps pumping through 2*amount of new fluid is in fact the best way?

« Last Edit: November 25, 2016, 12:40:28 PM by tom400f »
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Offline Trigger

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Re: Front brake service / set up 400/4 advice please
« Reply #18 on: November 25, 2016, 02:01:36 PM »
I think it's a measure of how people are willing to approach things on this site that you can discuss areas like this. On some car sites it'd be met with a rider of not working on critical things like brakes and advising to only buy and replace components.

Agree with you Trigger,  I was wondering after posting if I should've covered more of the system. So at the risk of boring everyone I'll make some additional points.

Quite often people assemble the caliper by using brake fluid to ease the piston past the seal but this leaves fluid on the outside of the seal which doesn't protect it. The caliper should be clean and dry, use the brake system grease to lubricate the seal and the piston should just push in with your fingers. When you then fill the completed system,  the fluid is only on the correct side of the seal and helps to avoid corrosion.

The master cylinder is obviously another part critical to decent operation. The seals there have different functions which are not readily observed. When you first start to move the lever the fluid will try to go out via the easiest route from the piston chamber,  this tries to exit into the reservoir. The first seal operation is to close off that route and if the part of the seal that completes that function is impaired then more of the lever stroke is used before the brake line is pressurised. The seals when they get older and less squishy just don't do that so well, they get there but the lever travel is long as the seal requires the line pressure to build up as it's closing to assist 100% closing. This results in the lever coming too close to the bars and a critical feeling of delay to the rider.

The hole into the reservoir is also an area to look at. If it's partially blocked then two affects are possible, when you release the brake after use the hole is opened to allow the reserve fluid to refill any space in the brake line that has been created by pad wear. It's this aspect that makes disc brakes essentially self adjusting (discounting the screw adjust on the Honda caliper) and resets the lever position each time to give a good lever feel. It also makes the system hard to blead as quick replenishment of the line doesn't take place with the fluid in the line just being pushed down and then pulled back again as you release the lever.
Second effect is that the hole is mostly blocked and as a bit of heat comes into the brake system during use,  then the fluid can't expand anywhere so the pads are held against the disc and more heat is created (you often see this on rear disc brake systems as they are just not used at the frequency of the front) this will if not corrected end up looking the brake on.

Piston material in the caliper has an impact on longer term use as well. The corrosion of piston and bore is mostly caused by galvanic reaction ( one material electroplating from another when submerged in an electrolyte solution) in this case the electrolyte solution would be salt water. Even if you use a stainless steel piston the two materials still appear with a difference on the galvanic scale which doesn't stop the problem. There are I believe phenolic resin pistons available for these calipers which are obviously not metal so long term use of this type I think should be considered two best look after the original caliper material.

If you use them all year round and expose them to salty roads then you are probably looking at a strip down every 24months at a guess. This is alot of calipers nowadays have an additional seal outboard of the main one to keep that area as clean as possible.

I know they won't match modern systems for braking power but set up as intended they are alot better than most people indicate.

You must have more time on your hands than me  ;D.
Cheers for all that correct info. Saved me writing it  ;)

I do get annoyed when people bring there bike to me saying, I have fitted new braided lines and still have the same problem. Honda lines are braided, you just can not see the braiding.

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Re: Front brake service / set up 400/4 advice please
« Reply #19 on: November 25, 2016, 05:51:05 PM »
When I changed to silicone fluid I don't recall flushing the system but I had replaced the master cylinder and calliper seals. The piston was also replaced. Genuine Honda parts used. After cleaning there was certainly no fluid in the cylinder or calliper. I would imagine that any old fluid that may have been left in the system would be flushed out when the brake was bled. I think I've only bled the brake once since the change and that was because the front brake switch failed.

I would imagine that if silicone fluid has an adverse effect on the seals the fluid would become discoloured. 

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Re: Front brake service / set up 400/4 advice please
« Reply #20 on: November 25, 2016, 06:45:31 PM »
Ha ha Trigger,  I suspect you're a bit more productive than me thought as you've not seen things this end. I can't even get through my list of things to do in the house without the family chief executive (known more commonly as er-in-dooors) putting things on the end of the list while I'm trying to knock things off the top ;) I was late for working today though,  partly for battling with my spell checker as it insists every mention of piston should be pistol. Still some typos left in there though.
On that note; I guess the list of brake things is not complete without mentioning you've got to keep the arm pivot clean and free to move easily either.

The silicon brake fluid as far as I know will mix ok, just that by using silicon for its main attribute (it's not hygroscopic, so doesn't attract water and degrade) it will be compromised by having any old type fluid left. Think it's sufficient as stated to make sure you bleed it through the system completely, it shouldn't give any real problems.

On the subject of getting done in time for Christmas,  I reckon if I get the Brussels sprouts in the pot and boiling by the end of November then they should be just about ready for Christmas day ;)

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Re: Front brake service / set up 400/4 advice please
« Reply #21 on: November 25, 2016, 06:51:06 PM »
Should have put the sprouts on last week if you want them done properly by Xmas day 😁😁😁
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
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Re: Front brake service / set up 400/4 advice please
« Reply #22 on: November 25, 2016, 07:02:59 PM »
Yaaaa bugger,  another deadline missed;)

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Re: Front brake service / set up 400/4 advice please
« Reply #23 on: November 25, 2016, 07:48:59 PM »
Should have put the sprouts on last week if you want them done properly by Xmas day 😁😁😁


   oh !! you like them al dente !!!

  should really be middle of april so the cook through !!!
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Offline Rozabikes Tim

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Re: Front brake service / set up 400/4 advice please
« Reply #24 on: November 27, 2016, 08:54:04 PM »
Well caliper rebuilt with stainless piston / Honda seal. System fushed with meths and blown through with airline to dry out any residual meths before filling with silicone brake fluid. Caliper now very free and brake actually works. Still not brilliant but will look at other system components when resto starts.

I was amazed by the amount of oxidation etc in the seal grove. Accompanying picture shows the crap cleaned from this small area alone! (hope this works its the first time I've tried to insert an image in a post)


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Anyway was able to ride it and check gearbox etc. All seems ok so no real worries before resto starts in the new year.

Thanks again for helpful tips.


Tim
One day I'll have the time to restore it, not just talk and dream....

Offline Johnwebley

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Re: Front brake service / set up 400/4 advice please
« Reply #25 on: November 27, 2016, 09:12:37 PM »
now you have the mechanical side working,you need to ride and use the front brake often,but gently ,just to bed the pad in,

  Although I have twin discs,I only brake softly,and its taken ages to bed the pads in,

 I used DSS own make pads,and they seem very hard,hardly worn at all,
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Re: Front brake service / set up 400/4 advice please
« Reply #26 on: November 27, 2016, 09:20:48 PM »
I had to rough the DSS pads up to get them to work.But they have been fine since though.
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Re: Front brake service / set up 400/4 advice please
« Reply #27 on: November 30, 2016, 09:42:10 AM »
It's surprising when you take them apart just how much crap builds up in the groove. All clean and reassembled properly they do last quite well with the proper grease used but longer term I think you'd have to plan reasonable maintenance into running them to keep on top of it. It's really road salt that gets them going bad so if that's avoided then they stay in good nick for longer.

Bedding any pads in should take about 50miles of light use just to get the pads lying flat to the disc and any deviations on the disc if it has any wear.
After that to really get pads working properly you've got to take them through their entire heat range and back to cool to prepare them for general use.

I do this by riding and gently dragging the brake to build heat up slowly, then as the whole caliper and disc is warm keep going with more brake pressure until the pads start to smell,  and then more pressure (you may need to run it in 3rd gear to keep it moving along at this stage) until you feel the brake start to fade, ie retardation starts to go down even though you're pulling the lever hard, and the then keep going until it feels like it won't stop the bike ( yes you need to go this far) at this point release the brake but don't whatever you do stop the bike, just ride it gently until the whole system cools down back to normal. You'll they find when you use the brake normally it's the best it's ever been ( this assumes you've got all the system clean and working properly before you start). After this you'll find it gives the best friction power and linearity you can get for that system. Not many people do this properly so never get to see what their brakes will do.

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Re: Front brake service / set up 400/4 advice please
« Reply #28 on: November 30, 2016, 06:42:03 PM »
The rear brake was non existent on the Guzzi so that's how I bed in the new pads.Now its almost unusable as it is like an on off switch at low speed.
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