I thought ebikes with hydraulic disc brakes use mineral oil for brake fluid. I was surprised to find that my Fly-7 E-moped https://www.flyebike.com/product-page/fly-7 use DOT-3.
How common is that?
How common is that?
Dot-3 brake fluid in E-moped?
- Thread starter Zambam
- Start date
Chalo
100 TW
Bicycle hydraulics don't standardize on things like fluids and fittings because they're not serious equipment. They're toys for children of all ages, as long as those children don't require their stuff to work.
Take the hint.
Take the hint.
I bought my Fly 7 (with SLA batteries) Dec 2021 for $995. It currently has only 2,360 miles on it. A few days ago I needed to do an errand and could not roll it out of the parking spot. Investigation revealed front wheel was locked up. After a bit of struggle got the caliper off and the wheel now turns. Dual pistons were rusty and frozen. Called the local Fly 7 dealer and was told $70 parts and labor to replace. 15 min ride (with no front brakes), waited 10 min when a mechanic was free and he finished the job in approx 1/2 hour. I was surprised to see him put in DOT 3 but that's what it takes.
The chrome plating on these caliper pistons is garbage. What should I do for maintenance? I am thinking of removing the calipers every 6 months ( 2 bolts) to clean and lube the pistons.
What kind of lube should I use to keep the rust away?
The chrome plating on these caliper pistons is garbage. What should I do for maintenance? I am thinking of removing the calipers every 6 months ( 2 bolts) to clean and lube the pistons.
What kind of lube should I use to keep the rust away?
lnanek
10 kW
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- Sep 26, 2022
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Those are pretty corroded. Do you keep the bike outside and could keep it inside instead? Can you put a cover on it? Do you hose it down after riding it on salty roads? Maybe hose it down then spritz with alcohol to dry quicker even. Or start using brake cleaner regularly.
For my mineral oil hydraulic brakes I use a drop of the same on the sides of the cylinders when they are sticky to lube them. No idea about DOT fluid. Isn't it toxic? I generally keep greases away from brakes even if it protects metal from rust. If any got on the rotors or pads, there goes you breaking power.
For my mineral oil hydraulic brakes I use a drop of the same on the sides of the cylinders when they are sticky to lube them. No idea about DOT fluid. Isn't it toxic? I generally keep greases away from brakes even if it protects metal from rust. If any got on the rotors or pads, there goes you breaking power.
I do not ride in rain or snow so salty roads is not the issue. It's kept outside under a big awning, not exposed to direct rain. No indoor space available. There's also rust on the chrome plated railings (most of it on the welds), likely due to bad prep and poor quality plating.
I took the rear caliper off to have a look. It's not sticking (yet) but I do see slight corrosion on the pistons. Wiped it off as much as I can with a cloth then put a drop of DOT 3 on it and put it back together. On a nicer day I will take the rear caliper off again, remove the pads, move the pistons out further to give it a better cleaning. I think these calipers needs to be removed and cleaned every 6 months instead of being neglected for almost 3 years. I will add an event to my calendar so I do not forget.
I took the rear caliper off to have a look. It's not sticking (yet) but I do see slight corrosion on the pistons. Wiped it off as much as I can with a cloth then put a drop of DOT 3 on it and put it back together. On a nicer day I will take the rear caliper off again, remove the pads, move the pistons out further to give it a better cleaning. I think these calipers needs to be removed and cleaned every 6 months instead of being neglected for almost 3 years. I will add an event to my calendar so I do not forget.
marty
10 MW
That seems a bit excessive. If its not broke don't fix it.
Many calipers ago I bought a rebuild kit. Rubber rings and stuff. Took caliper all apart. Could not get piston back into hole. Took it to a real mechanic. He got it back together.
What ever fluid brakes take. DOT 3.
I put brake lube on outside of pads. Not sure why? Copy Google AI.
There is something that lets caliper slide so both pads wear evenly. Copy Google AI.
Important to clean and lube those pins.
Once saw a guy with a broken finger. I said how did you break your finger? Caliper testing. Ask helper to press brake pedal. Caliper breaks finger. Test complete. Caliper good.
What is brake lube? Look, smells, and tastes like grease. Copy Google AI.
What is Google AI? OK Marty that's enough copy and paste.
Other people replace rotors. Not me. When replacing pads I usually clean rotor with hammer, paint scraper, sand paper.
PaPaSteve
10 kW
DOT 3 fluid in a brake designed for mineral oil will cause the seals to swell potentially causing leaks and / or the pistons to bind.
Mineral oil in a DOT 3 brake will cause no trouble.
Silicone fluid is safe to use in all brake systems or seal types.
Isn't it crazy when machinery sits for a while it tends to rust in place ?
Mineral oil in a DOT 3 brake will cause no trouble.
Silicone fluid is safe to use in all brake systems or seal types.
Isn't it crazy when machinery sits for a while it tends to rust in place ?
Frozen caliper pads locked rotor can't be removed (caliper hits the rim on this moped). I spent 20 minutes trying to get it off. Unfrozen, caliper comes off in less than 1 minute by undoing 2 bolts. Much easier to service it on a schedule before it breaks.
offGridDownUnder
10 kW
Unless you have researched the seal compound and know for a fact that it will resist lubricants, this is dangerous. Many elastomers will be damaged by the volatiles in lubricants.
I specified engineering chrome platings - we stated "hard, dense, fine, satin-finish chromium plate". Shiny chrome is mirror-finish because it is so thin. Appearance chrome plating is crap.
When I said "lube the pistons", I did not mean to take the pistons out and lube the entire thing, only the portion exposed to the elements (beyond the seals), to keep rust from developing. If done every season, I think will lower the incidence of frozen calipers.
Can you cite some scientific studies?
marty
10 MW
Don't forget rust on walls of hole that piston fits into. If you having frozen caliper paranoia? There is medication for that.
I am a believer in reading and following service recommendations in service manuals. Just completed reading every service manual for every car, truck, motorcycle, and moped on planet earth. None of them say to operate on a operational hydraulic caliper. They do say rebuild or replace calipers as necessary. Check pads every ? miles. Also replace fluid every ? years or ? miles.
Best advise is ride the moped every day. See ya live in NYC. Probably not riding much in the winter. Calipers sitting unused for a winter would be more likely to get stuck. Best to store moped indoors if possible.
Also as I said before:
There is something that lets caliper slide so both pads wear evenly. Copy Google AI.
The part that allows the brake caliper to slide, ensuring even wear of both brake pads, is called the caliper slide pins or guide pins.
Important to clean and lube those pins. THIS IS IMPORTANT MAINTENANCE.
PaPaSteve
10 kW
Sorry . . . Honestly can't remember where that knowledge came from.
Technical reading is part of the hobby of building and maintaining things.
Generally speaking, the DOT numbers for brake fluid relates to temperature stability of the fluid with the higher number being the most heat tolerant.
Mineral fluid being the least heat tolerant and also least toxic.
Baby oil is a version of mineral oil and can be substituted in a pinch.
Brake Fluid: Stay Safe And Go Fast
Understanding types of brake fluid, change intervals and the conditions that lead to contamination/degradation it is paramount to a successful brake setup.
tiltonracing.com
(Silicone):
- Dry Boiling Point: 260°C (500°F)
- Wet Boiling Point: 180°C (356°F)
- Composition: Hydrophobic polydimethylsiloxane
- Characteristics: Non-hygroscopic (doesn't absorb water), making it a good choice for classic cars and vintage vehicles.
- Color: Typically purple
- Not compatible with: DOT 3, DOT 4 or DOT 5.1
I don't think you understand the purpose of "scientific studies". No one will guarantee that mineral oil will work with every single DOT brake system, because noone's going to to test them all. At the same time, there are no good reasons why it wouldn't; DOT is more corrosive and systems that use it use rubber seals that can withstand it. By extension, they will generally work fine with mineral oil - at the cost of much lower maximum operating temperature.
Technically speaking there might be viscosity differences affecting long term braking performance. When in doubt, just replace your DOT3 or DOT4 fluid with brand new basic DOT5.1 which is cheap enough to not warrant worrying about all the variants. DOT5 is almost exclusively used in american vehicles and can only be replaced with itself.
PaPaSteve
10 kW
To be clear, I'm not advocating mixing fluid types.
Chalo
100 TW
Considering that your contraption is a facsimile of a motor vehicle and will tend to use those standards, my best guess is that you're only dealing with low component quality (cheap materials, poor finishes, thin platings) rather than some more fundamental issue. Given that you paid less than $1000 for it, that's no surprise at all. You got yourself a scooter-shaped object.
I think the low price of this particular model is because it's been in production for many years (at least 10). It's the most common delivery ebike in NYC with a big network of dealers to keep them running. For $995 (SLA battery) you get:
| Features | Remote Key Fob Alarm System Lockable Under-Seat Storage Front and Rear Suspension Full Lighting Package Arrives Fully Assembled |
| Motor | 1500W/BRUSHLESS |
| Battery | 60V/20Ah Lead-acid battery 60V/50Ah Lithium-ion battery 60V/55Ah Lithium lon Battery |
| Range | 60/20Ah (Lead-acid) : 20-25miles 60V/50Ah (Lithium-ion): 55-65miles 60V/55Ah (Lithium-ion): 60-70miles (Mileage may vary depending on rider weight and road conditions) |
| Top Speed | 30MPH |
| Charging Time | Lead-acid Battery: 8-10 Hour Charging Lithium-ion Battery: 8-10 Hour Fast Charging （Will take 12 Hours if voltage is low ） |
| Payload Capacity | 350LB |
| Brake | DISC/DISC |
| Tires | 10x3.0" |
| Headlight | YES |
| Taillight | YES |
| Turnsignal | YES |
| Rear-view Bike Mirror | YES |
| Charger | YES |
| Back Seat Step Pegs | YES |
Isn't that a great deal? With a 60 V 50 Ah Lithium the price almost doubles. My front brake caliper froze up due to lack of use and service over the winter (I won't make that mistake again with the new caliper). Since my lead acid battery died, I built a 72V 30 Ah LFP (22S) battery for it. Bike was transformed! Now it has very good acceleration, top speed of 40 Mph, 50 mile range and can now keep up with car traffic. It's my go to bike for errands if I want to get there fast. It can carry so much it's amazing!
Too bad you don't have Fly 7 dealers in TX. If you can try one, I'd think your opinion will change.
Last edited:
I didn't think you were!
Have you converted DOT-3 brakes (filled with DOT-3 initially) to DOT-5?
PaPaSteve
10 kW
Yes.
A simple drain and refill.
Just refill, no flush with DOT 5? What benefits did you notice?
PaPaSteve
10 kW
Refilling is a flush.
Simplest method is to use a clear hose attached to the caliper bleeder port.
Bicycle calipers have a plug not a bleeder so a hose barb will need to be fitted to the hose.
Thread size could be 5 or 6mm.
Yours being a "motorcycle" it likely has a bleeder like this.
Use a long enough hose to go up a bit before spilling into a catch bottle.
Open the reservoir at the handlebar to watch the level, to avoid extra work. don't allow level to drop enough to let air in.
Squeeze the handle to move the fluid out the hose.
Old fluid usually is a darker color.
Brake fluid can draw in water which is compressible leading to a spongy feel and water can corrode metal parts.
Simplest method is to use a clear hose attached to the caliper bleeder port.
Bicycle calipers have a plug not a bleeder so a hose barb will need to be fitted to the hose.
Thread size could be 5 or 6mm.
Yours being a "motorcycle" it likely has a bleeder like this.
Use a long enough hose to go up a bit before spilling into a catch bottle.
Open the reservoir at the handlebar to watch the level, to avoid extra work. don't allow level to drop enough to let air in.
Squeeze the handle to move the fluid out the hose.
Old fluid usually is a darker color.
Brake fluid can draw in water which is compressible leading to a spongy feel and water can corrode metal parts.
I'd like to reiterate that DOT 3 and DOT 5 are incompatible fluids and should never be mixed with each other. Refilling in a normal way will mix them together, it doesn't guarantee a total clean flush of the system.
Frankly, save from complete disassembly of both cylinders and likely complete replacement of hoses, or ar least flushing them with a lot of water and drying up with compressed air, there aren't many good ways to completely clean the system.
Frankly, save from complete disassembly of both cylinders and likely complete replacement of hoses, or ar least flushing them with a lot of water and drying up with compressed air, there aren't many good ways to completely clean the system.
What vehicle did you do that on? Any issues? What benefits were you expecting (switching from DOT 3 to DOT 5)?
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