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I have a specialized fuse with avid db3 brakes. last rode this bike in april and the brakes were dialed in. pulled it out of the garage today and the rear brake offered no resistance, pulling the lever completely to the bar engaged the pads but the back wheel will could still role. no leaking of brake fluid.

is this due to the heat?
 

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Always in the wrong gear
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My wife doesn’t like it, but both the ‘important bikes’ (our mountain bikes) live in our guest room/office year round. The beater neighborhood bikes with tubes and cable brakes stay out there, but it’s only half for security reasons

AZ summer heat is hell on brake fluid and tire sealant. Storing a bike inside probably DOUBLES the life of these.


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No Clue Crew
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Me, either. My bikes stay in the garage or secure shed. I agree with the sealant drying comment, but suggesting heat impacts the DOT fluid in a MTB brake (which is the same as you run in your car) is off base.

Direct sunlight and high heat will have an effect on some SRAM brakes (swelling port in master cylinder), but not the brake fluid itself.

OP probably had an air bubble work it's way up. Trying flicking the affected lever a few times to see if you start getting some brake action. Likely just needs a bleed.
 

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Elitest thrill junkie
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So a bicycle with hydraulic brakes stored in a garage for a month of summer is worse than the heat generated from a month of riding?
Don't store your car in the garage either, it too has hydraulic brakes.
 

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Sram brakes have issues being stored in the heat. Nothing to do with fluids and everything to do with design at materials used. If you have Sram brake and store bikes in the garage it just an issue of time before they fail. If you store them in the house it is better. Sealant it purely about temperature.
 

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Actually it doesn't matter where you store the SRAM brakes...even if you store them in a freezer all it takes for them to gum up is just using them on a warm day.

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I guess that's why I don't like my SRAM brakes. LOL

Still can't wrap my head around why a garage heat is worse than the heat the brake system sees while in use.

Probably worse for people with a 1-car garage that park their vehicle in the garage...way too much heat build up in that tiny space for the system.

I get it, sustained 100 degree heat for several hours in a day. It's just nearly impossible to comprehend how SRAM is still in business if they can't make a brake system designed to resist ambient temperatures.
 

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The levers don't get hot when in use. The calipers do. The Sram problem is at the lever. I suspect the issue is down overall heat and how the DOT5 brake fluid interacts with nylon bushings in the lever. Close tolerances and it only takes a little swelling to cause issues. The nylon is probably the wrong material for this temperature application, but I bet Sram simply never tested to these temps and durations at temperature to see the interaction. BTW Nylon like other plastics can creep at temp. This means it can change shape when exposed to pressure and temperature over time. It can also react with other chemicals such as those found in brake fluid. Even silicone based DOT5.
 

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I get it, sustained 100 degree heat for several hours in a day. It's just nearly impossible to comprehend how SRAM is still in business if they can't make a brake system designed to resist ambient temperatures.
Well they won the OEM market, but definitely not because they make quality brakes.

Reminds me of going to a bunch of bike demos a couple years back. Twice in a month I grabbed a bike to go ride and the brakes wouldn't work. Show it to the demo tech and he said - "sometimes the SRAM brakes don't work when they've been sitting in the sun for a while." What??? So what happens when I've been riding the bike in the sun for awhile? Are the brakes going to stop working? 'Cause you know, I live in the south-west - where its sunny pretty much all the time!
 

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As several people have mentioned, ambient heat, even inside your garage during the summer in AZ, will have no effect on the brake fluid (neither the DOT fluid used in SRAM brakes, nor the mineral oil used by all other manufacturers). If this was in fact the case then you would need to replace the brake fluid after every single ride because it gets MUCH hotter from the friction generated at the caliper than any ambient temperature you will ever see outside of an oven.

As Joe pointed out, the SRAM problem lies with the lever (master cylinder) design and the seal material/design that tend to swell when the outside temperature even hints at a warm day in the forecast.

What everyone is failing to take into account is that the common SRAM brake failure is that the lever gets stuck in the ON position when hot, so that the brake is stuck in the engaged position until it cools off. It sounds like the OP's problem would be solved with a simple brake bleed..
 

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I chose my battles and this is not one I'm willing to lose.... bike stays in the garage.
My wife keeps her bikes in the bedroom closet, so there isn't space for mine, but I did insulate the garage so it doesn't get hella hot in there like it used to.
 

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As several people have mentioned, ambient heat, even inside your garage during the summer in AZ, will have no effect on the brake fluid (neither the DOT fluid used in SRAM brakes, nor the mineral oil used by all other manufacturers). If this was in fact the case then you would need to replace the brake fluid after every single ride because it gets MUCH hotter from the friction generated at the caliper than any ambient temperature you will ever see outside of an oven.

As Joe pointed out, the SRAM problem lies with the lever (master cylinder) design and the seal material/design that tend to swell when the outside temperature even hints at a warm day in the forecast.

What everyone is failing to take into account is that the common SRAM brake failure is that the lever gets stuck in the ON position when hot, so that the brake is stuck in the engaged position until it cools off. It sounds like the OP's problem would be solved with a simple brake bleed..
I think/hope/have been told that the heat issue with SRAM brakes has been identified and fixed.

I've ridden my relatively new Guide Ultimates in 100+ degree heat this summer without issues.

However, they seem to have less power than XTRs. I'll chose Shimano brakes next time.
 
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