Triumph Rat Motorcycle Forums banner
  • Hey everyone! Enter your ride HERE to be a part of October's Bike of the Month Challenge!
1 - 14 of 14 Posts

·
Registered
Joined
·
571 Posts
Discussion Starter · #1 ·
Pls see the bit in red - anyone ever heard or experienced this ??

G'day, did the job this morning, took 2 1/2 hrs.

Thx for the advice - it is really an easy job.

If the lever stays like this - it is PERFECT... Kinda sorry I didn't do it years ago.

Donor bike - 2008 675, very low klms.
My bike Sprint ST 2002.

My ST calipers only had 1 seal per pot, not 2,. There was a groove below the first seal but the groove was empty when I dismantled them. No way any of the seals could fit in that groove !! Assembled with only one seal ( the thin one in the top groove ? ) - as before and its great ?? All the pics I've seen show 2 seals per pot ?? :confused:

It was a bit of a messy job, but not so bad.. Also, dont let the m/cylinder get empty, when bleeding it take ages for the lever to pump out all the air - still great when done..

Ive riden the bike about 20 klms, plenty of hard braking to bed in the new pads - feels and stops great !!

The bike was 95% perfect before - now 100% .. I thunk !!

Can this be a safety concern ?? the calipers always worked perfectly, never leaked since new and apart from the mushy overnight lever, when it pumped up a bit the brakes were always more than I needed.. including a few track days. The pads I took out were less than 1/4 worn and they were changed 37K klms ago ...

Hope someone can share some wisdom.... Front brakes are serious stuff - Thx
 

·
Premium Member
Joined
·
619 Posts
I've come across this before .. The first seal nearest the outside world is a dust seal. This attracts a lot of stuff, and often the groove it sits in eventually corrodes up and stops the pistons from retracting. I had constant problems with sticking pistons in a sliding caliper on a Japanese Bike. I finally removed the piston only to find a black line where the dust seal should be. After careful cleaning with a plastic scraper, I found no seal fitted. I spoke to the previous owner, and he claimed the local Bike store told him to leave it out if it was binding the brake up ! After fitting, I've had no further trouble with the piston sticking, and that's through two British winters, along with the tons of salt we have to endure every year. Triumph have always used Nissin Calipers, with a dust seal near the lip of the hole, and the larger main brake hydraulic seal further in the caliper (A square seal)
 

·
Premium Member
2018 Kawasaki H2 SX SE, '73 Yamaha RD350, '74 Kawasaki H1E 500
Joined
·
2,048 Posts
My ST calipers only had 1 seal per pot, not 2,. There was a groove below the first seal but the groove was empty when I dismantled them. No way any of the seals could fit in that groove !! Assembled with only one seal ( the thin one in the top groove ? ) - as before and its great ?? All the pics I've seen show 2 seals per pot ??
Harry,

Yes, as pcdabbler has already confirmed, there are two seals per pot. You have replaced only the dust seal and possibly not realized there is another seal in there. Did you split the calipers and have a good look?

The seal further into the bore is wide and square edged so could easily be confused as part of the piston bore. What you thought was an empty groove may have simply been a gap between the seal and the groove. If I'm correct then there should not be a safety issue because you still have a fluid seal - the original one still in place. I would not recommend such practice but it is not a major safety concern.

If I am wrong and, as you said, there was only one seal in there then you are relying on a dust seal to withhold fluid pressure. I don't know why I'm telling you that because, if true, you may never get to read this. :eek:

Hope someone can share some wisdom.... Front brakes are serious stuff - Thx
Might be stretching things to call this wisdom - just basic common sense. My advice to you is to dismantle the calipers and take a good look for your own peace of mind. Make sure that the wider seal is there and that you re-assemble the calipers with both seals in each pot. Better still, since you've gone to the trouble of dismantling your brakes, do the job properly; take my previous advice and put new seals in there instead of trying to save a few dollars on half-arsed solutions. Like you said "Front brakes are serious stuff". No brakes are more serious!

Not the best picture ever but you can see the narrow dust seal near the outer lip of the piston bore and a wider fluid seal further into the bore.
 

·
Registered
Joined
·
571 Posts
Discussion Starter · #4 ·
Thx Champ..

What you say makes perfect sense..

Per the post - the ST calipers that I dismantled completely to change out the pistons - only had the dust seal.. I replaced the pistons and new dust seals only - as the second groove was " way thiner " than the dust seal groove ?? So - with only the dust seal in the original calipers, it worked fine.. for nearly 10 years !!

If no one else has seen this, then I have an odd set of calipers.. oh - and it was the same on both sides on all 4 caliper halves..

If it does not leak - then it must be ok ???
 

·
Registered
Joined
·
165 Posts
did this firm the lever up quite a bit?

I have been contemplating the 675 pistons when I rebuild the calipers...also may swap on a different MC, but if the pistons do the trick, it may not be worth it.
 

·
Premium Member
2018 Kawasaki H2 SX SE, '73 Yamaha RD350, '74 Kawasaki H1E 500
Joined
·
2,048 Posts
did this firm the lever up quite a bit?

I have been contemplating the 675 pistons when I rebuild the calipers...also may swap on a different MC, but if the pistons do the trick, it may not be worth it.
If you do a search there is a ton of informaton about this on this forum. I'll summarize it for you.

The piston swap is a cure for inconsistent lever travel caused by caliper pistons sticking. Sometimes the lever will be firm and other times it will come back a long way before providing any stopping power. Hardly confidence inspiring. Some bikes never suffer the problem while others, such as mine, would be OK when the pistons were cleaned but quickly revert to varying amounts of lever travel. Stopping power was never the issue on my bike - only variations in lever travel that have been completely eliminated by using D675 pistons.

For shorter lever travel the 14mm master cylinder can be replaced with a 5/8" MC. The shorter travel gives the impression of a harder bite and more powerful brakes but there is no actual gain in stopping power. Some riders prefer that feel while others might think it feels "wooden" with less feedback.

General rule is to replace the pistons if you are having problems with varying lever travel. With that problem fixed assess the brakes and decide if the master cylinder swap might give you a better feel.
 

·
Registered
Joined
·
571 Posts
Discussion Starter · #7 ·
Hey Outlawed..

++ for Champs explaination.. For my bike, that had the crappy brake feel for all those years - the 675 piston swap is fantastic.. problem solved.. not withstanding my curious seal issue. :confused:

My lever was that bad that I had to have the postioning pin ( fits in holes 1 thru 4 ) actually between the holes, even in hole 1 the lever would come back nearly to the throttle.. and in hole 4 - forget it. Not confidence inspiring - even though it did stop safely every time..

Another observation - the pureists wont like, I was strongly advised to replace the seals as they were near 10 years old. It was very hard to tell the differecne between the new ones and the old ones ?? The full set cost about A$ 135.00 so not cheap.. and I only used 1/2 of them anyway..
 

·
Premium Member
Joined
·
619 Posts
Seals can swell slightly and harden off with age. It's subtle. My take on your problem is as said by others before. I think you mistook the main piston seal as being part of the Body, and looked at the gap between the seal and the body. The square main seal sits almost flush. You usually have to carefully dig the main seal out, taking care not to damage the grove.
 

·
Registered
Joined
·
512 Posts
as the second groove was " way thiner " than the dust seal groove ?? So - with only the dust seal in the original calipers, it worked fine.. for nearly 10 years !!

...

If it does not leak - then it must be ok ???
The fluid seals must have been there are they're wider than the dust seals so what you've described is the slight gap between the fluid seal and its groove.

Not sure I agree with your philisophy on brakes! Personally if I was changing pistons, I'd change the seals too for the few pounds extra it'll cost.

Dave
 

·
Registered
Joined
·
571 Posts
Discussion Starter · #10 · (Edited)
Thx, finally makes sense .. You are saying that the thin groove I felt was a gap between the exsting oil seal and the caliper wall, so the old seal is still in there... I'll ride for a while and then pull them off again and have a MUCH closer look..

There was no oil seal gap on the 675 calipers, it was a tight fit and I had not had the ST ones apart before !!

THX again for the answer..:D:D:D
 

·
Registered
Joined
·
571 Posts
Discussion Starter · #11 · (Edited)
Update

G'day,

The brakes are now remarkable, they always stopped great, now I have perfert, progressive, brake feel, in the 2 and 3 slot. ( before, I had to have the pin between the slots to have any sort of reasonable lever feel )

I am now looking to see if there is a good mirror changeout. I looked in the archives and got lost :rolleyes: and seem to recall some time ago there was a post on this ? Can anyone point me in the right direction..

Also - have a K&N air filter to fit when it arrives.. I'll let you know how that goes and if there is any noticeable change or improvement..

Cheers..
 

·
Registered
Joined
·
571 Posts
Discussion Starter · #12 · (Edited)
Update..

_ posted elsewhere, while I'm at it..

It's been 8 months since I changed out the OEM front brake pistons with the set from 675 Daytona ...

The brakes are still PERFECT .. great feel, adjustment pin in 2 or 3 on a trip .. The OEM, in pin 3 would near touch the throttle... pin 4 - forget it..

There were many other temporary remedies in this forum, No doubt - this fixes it for life....:) For those effected, if you have a few tools, it's an easy job..
 

·
Registered
Joined
·
571 Posts
Discussion Starter · #13 ·
02 / 675 brake piston update

Hey,
Just f.y.i. brakes now 15 months on are still PERFECT..:D:D:D
 

·
Premium Member
Joined
·
24,407 Posts
Good to hear that Harry.:thumb

Mine have always been good on my Daytona 955, except once when I had really low pads on a track day and cooked the brake fluid = no brakes that was scary!

If you have not ridden a GT you should if just for the brakes!
They are awesome, very solid lever and ABS both ends.:)

Glad that yours are cured, the 675 Daytona pistons seems the best fix (IMHO) for 955 brakes being spongy as it was always the pistons sticking that caused the issue in the first place.

There was never anything wrong with the 955 Sprint brakes apart from the lever being spongy, fix that with the pistons with the better coating and she's all good.
 
1 - 14 of 14 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top