SRAM Guide RS Brakes - Lever slow to return

Jesterarts

Jesterarts

Likes Dirt
JoelFitz said:
Just for the record, the pistons in mine are like the image below.. I think some people are commenting that this design doesn't suffer the same issue, but it does..

View attachment 332365
Click to expand...
Damn. That sucks. Looks like the guides are a rebuild every 12 months or need an upgrade to the better levers.

Ah well. I will rebuild mine and see how long they last until they start to show symptoms again.
 
bowtajzane

bowtajzane

Likes Dirt
I'll be looking at getting some aluminum ones turned up for my set...
gotta be cheaper than a hole new brake set
 
9

99_FGT

Likes Bikes and Dirt
JoelFitz said:
Maybe get bulk made and sell em?

Sent from my XT1092 using Tapatalk
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Might be keen. Had a set for over 12 months, no problems. New bike, ex demo, 2 weeks old and the front lever doesn't return all the time, particularly at the bottom of long runs.
Sound about right?
Yes, it is a warranty issue, but warranty on a design issue (like Joel said) is a pita
 
link1896

link1896

Mr Greenfield
To make new aluminium pistons I need to know the ID of the bore, but I can't accurately or safely measure the ID , so will have to turn up a rod for a test fit to find the ID as best I can, once I know ID I can calculate the correct size orings. Really want to try quad rings, the OEM seals offer zero resistance to side loading, an ally piston running on the bore would be bad. Who knew piston slap could be a thing in bike master cylinders. Maybe the aluminium piston needs a guide ring.

Will share my drawings with everyone.


I've a mate with a dozen cnc mills and lathes in the workshop he manages, but currently the whole fleet is running 24/7. Might be able to run a batch.

Really can't rush this, I think there are a few things at play here. The plastic pistons from RS and RCS levers, do they have rub marks on one side only?
 
bowtajzane

bowtajzane

Likes Dirt
mate , do let us now how you go,i was just going to give the hole thing to the machine shop and let them weave there magic
 
J

JoelFitz

Likes Dirt
Mine didn't have any rub marks, but there is only those 3 small contact points of the rsc piston.

Sent from my XT1092 using Tapatalk
 
Nambra

Nambra

Definitely should have gone to specsavers
Keen to see how this turns out, being a Guide owner as well.

Could you get dimensions from a replacement plastic piston out of a service kit perhaps?
 
link1896

link1896

Mr Greenfield
Nambra said:
Keen to see how this turns out, being a Guide owner as well.

Could you get dimensions from a replacement plastic piston out of a service kit perhaps?
Click to expand...
I will be copying the plastic pistons dimensions (except diameter ) to make my first copies.
 
Nambra

Nambra

Definitely should have gone to specsavers
link1896 said:
I will be copying the plastic pistons dimensions (except diameter ) to make my first copies.
Click to expand...
Don't the pistons vary between the various versions of the lever ie. R, RS, RSC?

Slightly OT, but has anyone seen the Guide now has an RE version, meant for e-bikes and based on a Guide R lever with a Code caliper? Supposed to provide lots more stopping power for electric bikes, but no reason they couldn't be used on a normal bike...
 
link1896

link1896

Mr Greenfield
Nambra said:
Don't the pistons vary between the various versions of the lever ie. R, RS, RSC?

Slightly OT, but has anyone seen the Guide now has an RE version, meant for e-bikes and based on a Guide R lever with a Code caliper? Supposed to provide lots more stopping power for electric bikes, but no reason they couldn't be used on a normal bike...
Click to expand...
R and RS look to be the same design from photos and parts catalog ( but with different part numbers due to the swinglink associated parts in the kit )
 
Boom King

Boom King

downloaded a pic of moorey's bruised arse
link1896 said:
I will be copying the plastic pistons dimensions (except diameter ) to make my first copies.
Click to expand...
When you have everthing sorted, let me know. I've got RS on the Povo and might need a pair if you are keen on making some in exchange for cash or other goods?
 
Jesterarts

Jesterarts

Likes Dirt
link1896 said:
Started work on aluminium pistons.

Bore is 9.45mm I believe.



Click to expand...
That is looking fantastic mate! Very interested to hear how you go.

Might try and do the same when my new internals arrive, but it's been a while since I've handled a lathe.

You said you are not machine the OD to the piston but rather using the bore of the lever. How are you accounting for heat expansion, etc?

Or do you think since both the level body and the piston are not aluninium, their expansion should be the same and you can reduce tolerance?
 
link1896

link1896

Mr Greenfield
Jesterarts said:
That is looking fantastic mate! Very interested to hear how you go.

Might try and do the same when my new internals arrive, but it's been a while since I've handled a lathe.

You said you are not machine the OD to the piston but rather using the bore of the lever. How are you accounting for heat expansion, etc?

Or do you think since both the level body and the piston are not aluninium, their expansion should be the same and you can reduce tolerance?
Click to expand...

I haven't settled on a piston OD yet, this was made just to find the ID of the lever bore so I can calculate appropriate dimensions. I don't have any accurate measuring tools to measure a 9-10mm hole that's start is 40mm in, so turning up a blank that just fits is my only option, then I measure that.
 
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