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Lucky Phil

Brake fluid tester.

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Looks like a good idea. Tell me, have you tested fluid flushed out of a caliper and compared it fluid in the reservoir? I always wondered how much the fluid mixes in a non-ABS brake system.

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Josh was just doing some testing on one of the SpineRaid V11. Pretty revealing. The question about comparing the caliper fluid to the reservoir is an interesting one.

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Why?  I just bleed the entire system every five years or so mainly to get all the black particles out of it.

 

My "specialty tool" box is overbrimming and I'd have to get a second box.

 

For those of you who have the tool you might consider removing the battery for those long periods of disuse.

 

Mark

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If in doubt, chuck the fluid out.

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I like changing my hydraulic fluids when the wheel comes off; front usually less than two years, rear (and clutch) about a year. By then the piston movement needs evened out anyway.  Using a tester looks like great method. Our Resident Pros do it! :luigi:  :thumbsup: 

 

Wheels Off Maintenance Checklist

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I've set up a pre-SSR TechSession to compare caliper to reservoir fluid, but the front brake fluid on this bike is already shot (wet), so we might not learn much . . .

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Why?  I just bleed the entire system every five years or so mainly to get all the black particles out of it.

 

My "specialty tool" box is overbrimming and I'd have to get a second box.

 

For those of you who have the tool you might consider removing the battery for those long periods of disuse.

 

Mark

You just made my point. Recommended replacement is every 2 years, not that I've been particular about doing it this often.

The dealer called the other day during the service of my wifes 2 year old Ford Escape saying the brake fluid needed changing out as it was +4%. Being the scepticle type I said dont bother as it was and added cost and It sounded over the phone like a extra work generating thing. As I said I am aware that the recommendation is change every 2 years but this car gets an easy life in benign weather conditions so I let it slide but thought I'd invest in the tool. I was thinking it should go well past 2 years, but I was wrong, it was over 4%. I actually checked the calibration of the tool before I started as well to be sure.

I also checked my 1 year old Focus and it was under 1%. The V11 was over 4% as well and I changed the fluid out.

The V11 didnt surprise me but the wifes car did and based on the Focus being under 1 % I can only assume the Escape probably left the factory with suspect fluid.

So I've got a lot of brakes to bleed now. I've had a vacuum bleeder for years and not been impressed with it to be honest so I also invested in one of these. Makes brake bleeding super simple on cars esp, dirt cheap and adaptors available for just about everything made including bikes.

 

https://www.ebay.com.au/itm/Motive-Products-0100-Pressure-Brake-Bleeder-Wilwood-Master-Cylinder/131499801918?epid=1128155773&hash=item1e9dffbd3e:g:BjkAAOSwMl9aXVVA

 

Ciao

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I've set up a pre-SSR TechSession to compare caliper to reservoir fluid, but the front brake fluid on this bike is already shot (wet), so we might not learn much . . .

Its an interesting question and since water is heavier than oil I'd assume it would work its way to the bottom of the system eventually. Data would be interesting for sure.

 

Ciao

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Not this coming weekend, but the next (Sept-the-One'th), we'll collect some "data" from two V11, both reservoir and first bleed from the calipers.

 

The longer these fluids sit in these hydraulic systems, the more I would expect the water to fall into the calipers (bottom).

Will this hypothesis test out? :huh2:

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Not this coming weekend, but the next (Sept-the-One'th), we'll collect some "data" from two V11, both reservoir and first bleed from the calipers.

 

The longer these fluids sit in these hydraulic systems, the more I would expect the water to fall into the calipers (bottom).

Will this hypothesis test out? :huh2:

As an aside docc my Focus reservior cap was leaking slightly a few months back and long story short I was surprised to find a lot of the modern automotive reserviors aren't a totally sealed unit as you might expect from the past or the motorcycle world. I checked carefully the rubber bellows and found a very small slit in the centre and thought I had found the culprit. Turns out the Escape cap seal/bellows was the same! Did some research including a patent search and found this is typical of systems these days on cars with small reserviors. Its a deliberate slit to allow for expansion and contraction that the small reservior bellows cant always accomodate. So there is an avenue for water ingress it seems.

Issue on the Focus turned out to be due to over filling and in these non totally sealed systems that can cause annoying leakage around the cap.

 

Ciao  

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So, my thinking that water sinks in brake fluid because it is "oil" is in error. Brake fluid is a mixture of glycol ethers with a specific gravity of ~1.04-1005 (they vary), while water is lighter (SG= 1.0 @4ºC).

 

Motor oil  has a specific gravity of ~0.80-0.90, so naturally water will "sink" in oil.

 

Yet, glycol ethers are also water soluble (therefor hygroscopic/ "soaks up water") while oil is not. Water separates in oil, yet disperses in brake fluid. So, it will be interesting to compare caliper to reservoir values over three Guzzis with nearly identical brake systems and three different age/ condition fluids.

 

There certainly may be little to no difference in water content between the two opposite ends of the system.  [Testing scheduled for 1 September when we can assemble some SpineRaid Guzzis for final prep :luigi: )

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So, my thinking that water sinks in brake fluid because it is "oil" is in error. Brake fluid is a mixture of glycol ethers with a specific gravity of ~1.04-1005 (they vary), while water is lighter (SG= 1.0 @4ºC).

 

Motor oil  has a specific gravity of ~0.80-0.90, so naturally water will "sink" in oil.

 

Yet, glycol ethers are also water soluble (therefor hygroscopic/ "soaks up water") while oil is not. Water separates in oil, yet disperses in brake fluid. So, it will be interesting to compare caliper to reservoir values over three Guzzis with nearly identical brake systems and three different age/ condition fluids.

 

There certainly may be little to no difference in water content between the two opposite ends of the system.  [Testing scheduled for 1 September when we can assemble some SpineRaid Guzzis for final prep :luigi: )

Hey docc, interesting SG data. I just assumed the water SG would be the greater but there you go. I did calibrate the tester I had by measuring out 10ml of brake fluid checking the reading and then adding water via a syringe at .1ml incriments and it looked accurate. The water mixed with the brake fluid quite well seemingly after a bit of shaking and stiring.

 

Ciao   

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One thing I think we can state definitively is that Guzzi brake fluid is shaken, not stirred:grin:

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I did just get my cheap fluid tester. Obviously, we did not get the planned testing done before last year's South'n Spine Raid. Josh even found some new, unopened brake fluid with marginally high water content. Probably smart to test before pouring . . . :luigi:

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