Results 1 to 16 of 16
  1. #1
    mtbr member
    Reputation:
    Join Date
    Feb 2005
    Posts
    463

    Dot fluid - Hope brakes

    I've been looking at getting some very early Hope disk brakes. The model number is the one before the black and gold mono minis.

    My question is these brakes are 11 years old. Over time does the dot fluid do any harm to the inside of the main body and calipers? Also looking even further ahead what would they be like after another 10 years...I imagine it'll degrade but I'm not sure at what rate.


    Any ideas?

  2. #2
    mtnjam
    Reputation: ryman's Avatar
    Join Date
    May 2004
    Posts
    689
    either way it'd probably be a good idea to replace the DOT fluid with a bleed and do an overhaul of the levers' and calipers' seals
    Just ride down there and jump off something for crying out loud...

  3. #3
    ...idios...
    Reputation: SteveUK's Avatar
    Join Date
    Apr 2006
    Posts
    5,663
    The fluid will thicken and may stick to the caliper/lever interior, mostly around seals as that is where air will have entered the system. As ryman has already said, a seal change and fluid flush should leave the brakes good as new. Is it the closed system brakes, or the original Minis that you're looking to get?

    What use is a philosopher who doesn't hurt anybody's feelings? -
    Diogenes


  4. #4
    mtnjam
    Reputation: ryman's Avatar
    Join Date
    May 2004
    Posts
    689
    saga....SteveUK has a really good tutorial on how to change the seals and flush the lines too

    BTW, SteveUK...any pitfalls I should be on the lookout for when I change the lever and caliper seals on my Minis and M4s?
    Just ride down there and jump off something for crying out loud...

  5. #5
    mtbr member
    Reputation:
    Join Date
    Feb 2005
    Posts
    463
    It's the closed system brake that came out in 98 I gather. They're silver, I'm going to get them as I just need some cheap brakes but was thinking a bit retro and thought how long would these brakes last. From your answers it's the fluid that degrades but the alloy inside will last a long time which is great.

  6. #6
    KARPIEL USA Rep.
    Reputation: Brian HCM#1's Avatar
    Join Date
    Jan 2004
    Posts
    308
    Hope uses a good quality DOT 3-4 or DOT 5.1. I prefer and only use 5.1 for all my Hopes.
    KARPIEL'S NOW IN STOCK!brian@karpiel.com www.karpiel.com

  7. #7
    ...idios...
    Reputation: SteveUK's Avatar
    Join Date
    Apr 2006
    Posts
    5,663
    "any pitfalls I should be on the lookout for when I change the lever and caliper seals on my Minis and M4s?"

    The only possible slip-up could be fitting the MC piston seals facing the wrong way, which will result in fluid leaking from the MC. It's easily avoided by just paying attention as you go.

    saga, caliper seals are still readily available - I think they may (don't hold me to that!!) be the same as the Mini/M4 seals - but it's a long while since I've seen lever seal/rebuild sets. Given that caliper seals generally fail from long-term use and the lever assembly generally fails from damage, this situation isn't necessarily a problem; although after 10 years the probability of failure through deterioration will obviously be greater, particularly if the fluid is the same age.

    Especially now since the Moto range came out in 2007, the original (silver, two-piece) Mini brakes can be picked up for less than $60 per brakeset (less than the BB7 RRP) and would always be my recommendation for an inexpensive but very good quality brake.

    DOT fluid should be flushed every three or four years, more often for heavy-use brakes.

    What use is a philosopher who doesn't hurt anybody's feelings? -
    Diogenes


  8. #8
    sam575
    Reputation: sam575's Avatar
    Join Date
    Dec 2006
    Posts
    155
    Only difference between DOT 4 and 5.1 is the freezing point...DOT5.1 was devloped for colder climates, hence its demand in the European market (it has a lower freezing point). DOT 4 and 5.1 have the same boiling point. SUPER DOT 4 has a higher boiling point than both, and that is what I use (I live in Australia so DOT 5.1 isn't necessary). A high quality SUPER DOT 4 that is carefully blended can be used trouble free in systems that still demand DOT 3 because of seal compatibility issues. DOT 3 is obsolete technology, only car manufacturers like Toyota and Subaru are keeping it alive due seal compatibility issues within the master cylinders. SO if something says use DOT 3 - DOT 4 or 5.1 is ok. DOT 5 fluid is something totally different again and is not compatible with any bicycle brake systems that I know of, only some motrocycles (Harley Davidsons) and some older cars. DOT 5 is a Silicon based product.

  9. #9
    mtbr member
    Reputation: Curious-George's Avatar
    Join Date
    Aug 2008
    Posts
    161
    Quote Originally Posted by sam575
    Only difference between DOT 4 and 5.1 is the freezing point...DOT5.1 was devloped for colder climates, hence its demand in the European market (it has a lower freezing point). DOT 4 and 5.1 have the same boiling point. SUPER DOT 4 has a higher boiling point than both, and that is what I use (I live in Australia so DOT 5.1 isn't necessary). A high quality SUPER DOT 4 that is carefully blended can be used trouble free in systems that still demand DOT 3 because of seal compatibility issues. DOT 3 is obsolete technology, only car manufacturers like Toyota and Subaru are keeping it alive due seal compatibility issues within the master cylinders. SO if something says use DOT 3 - DOT 4 or 5.1 is ok. DOT 5 fluid is something totally different again and is not compatible with any bicycle brake systems that I know of, only some motrocycles (Harley Davidsons) and some older cars. DOT 5 is a Silicon based product.
    Easy there, you've almost got the whole thing right, don't forget that the viscosity of dot 5.1 is much lower thus making it to move free-er in small cavity regions such as our mtb disc brakes...when referring to super dot-4 are you referring to the Bel-Ray oil or the Voltronic?

  10. #10
    sam575
    Reputation: sam575's Avatar
    Join Date
    Dec 2006
    Posts
    155
    The difference in Viscocity between Super DOT 4 and 5.1 is marginal, and only applicable at very low temperature, hence enabling the fluid to flow (which is why it was developed for countries with cold climates ie Europe, UK, USA, and parts of Asia). It is not "much lower". At operating temperature the viscocity is the same in both fluids, therefore there will be no difference in feel at the lever (or pedal).
    The Super DOT 4 I use is made by an Australian company called Penrite. They're standard Super DOT 4 has a 525 boiling point and the "SIN" racing brake fluid has a 600+ boiling point.

  11. #11
    mtbr member
    Reputation: Curious-George's Avatar
    Join Date
    Aug 2008
    Posts
    161
    Quote Originally Posted by sam575
    The difference in Viscocity between Super DOT 4 and 5.1 is marginal, and only applicable at very low temperature, hence enabling the fluid to flow (which is why it was developed for countries with cold climates ie Europe, UK, USA, and parts of Asia). It is not "much lower". At operating temperature the viscocity is the same in both fluids, therefore there will be no difference in feel at the lever (or pedal).
    The Super DOT 4 I use is made by an Australian company called Penrite. They're standard Super DOT 4 has a 525 boiling point and the "SIN" racing brake fluid has a 600+ boiling point.
    You keep on comparing Super Dot 4 to dot 5.1, when im referring to operating temperatures in viscosity im talking about regu dot 4 vs dot 5.1 which are different

    can you include the link for both those fluids plz

  12. #12
    mtbr member
    Reputation:
    Join Date
    Jan 2008
    Posts
    131
    Formally DOT 3, 4 and 5 are requirements put out by the Department Of Transportation in the USA to which brake fluids have to comply. It so happens that at first the only fluids compatible with the DOT 5 requirements were silicone based. It's when the DOT 4 fluids developed into the "Super DOT 4" fluids that actually complied to the DOT 5 requirements that the DOT 5.1 designation appeared to differentiate between the 'classic' silicone based DOT 5 fluids and the glycol based DOT 5 compatible fluids. And yes there is also a difference in boiling point (both dry and wet) for DOT 5 vs DOT 4, so DOT 5.1 fluids have a boiling point that is guaranteed to comply to these higher requirements. This is not to say that DOT 4 fluids cannot have boiling points higher than the DOT 5 spec. Some quick Googeling results in information about this, e.g. this one and this one

  13. #13
    mtbr member
    Reputation: J. G.'s Avatar
    Join Date
    Nov 2008
    Posts
    5
    great info, thanks guys!!!

  14. #14
    sam575
    Reputation: sam575's Avatar
    Join Date
    Dec 2006
    Posts
    155
    Only difference between DOT 4 and Super DOT 4 is the dry/wet boiling points (super dot 4 is higher so will out perform dot 4). Operating temp viscocity in dot 4, super dot 4 and dot 5.1 is the same, hence why they are all compatible with each other for top-up.

    The difference between a dot 5.1 and dot 4 (and super dot 4) is low temp viscocity (5.1 is lower) and this is why the European car manufacturers are using it.

    Links below for the Penrite products. Click on the "Product Information Sheet" link for full tech details.

    Brake Fluid 525
    http://www.penrite.com.au/html/s02_a...&nav_top_id=55

    SIN Brake Fluid
    http://www.penrite.com.au/html/s02_a...178&art_id=440

  15. #15
    mtbr member
    Reputation:
    Join Date
    Jun 2006
    Posts
    336

    5.1

    Any brand, I use Motorex.

    C2 is the brake model type probably, but a picture says a thousand words. I'd bet I have this same brake on my 1997 Schwinn Straight-6, which I still ride a couple of times a year. The brakes still perform. Maybe not as good as the latest and greatest, but they work and I don't have a choice for the rear. The frame is specific to the brake, prior to IS.

  16. #16
    sam575
    Reputation: sam575's Avatar
    Join Date
    Dec 2006
    Posts
    155
    Motul have a reasonably priced 5.1 also

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •