Frankenbrakes and brake improvement discussion
- Thread starter Udi
- Start date
I've had multiple setups leak right there. You should redo the connection with a new olive.
I had one set that no matter how many times I reseated the hose, it would still leak. Something was up with the shape of the threaded barrel that crushes the olive in there. Switching out one of those finally did it. Just an idea.
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You need to decide if you want help, or if you're already an expert on the topic. You strike me as wanting both.
An open system brake works by using a square section seal that deforms when you squeeze the lever to allow the piston to move outwards, and then retract when the lever returns. The seal deformation acts as a spring, in general operation the piston isn't sliding in the seal (at all). The piston slides outwards in the seal only as the pad wears, which allows more fluid to enter the pressurised system of the brake - so it's entirely possible to have sticky pistons/seals and still do exactly what you describe (i.e. appear to work) - in fact it's highly likely that this is the problem.
I'd advise lubricating and cycling the pistons (exactly as I described, once already), and suggesting that the owner invest in new pads (although it's not necessary, if you fill the system while the pads are worn, the system will be overfilled when the owner fits new pads) at which point the correct thing to do would be to let some fluid out of the system.
An open system brake works by using a square section seal that deforms when you squeeze the lever to allow the piston to move outwards, and then retract when the lever returns. The seal deformation acts as a spring, in general operation the piston isn't sliding in the seal (at all). The piston slides outwards in the seal only as the pad wears, which allows more fluid to enter the pressurised system of the brake - so it's entirely possible to have sticky pistons/seals and still do exactly what you describe (i.e. appear to work) - in fact it's highly likely that this is the problem.
I'd advise lubricating and cycling the pistons (exactly as I described, once already), and suggesting that the owner invest in new pads (although it's not necessary, if you fill the system while the pads are worn, the system will be overfilled when the owner fits new pads) at which point the correct thing to do would be to let some fluid out of the system.
Did the air bubbles come from under the reservoir cap or from under the hose fitting cover?
There's a big difference. If it's not from the hose fitting then it's not what kidwoo said.
You said "out of the reservoir".
The resivour cap
Then forget what I typed in that last post.
"The Cura 2-piston is, in their words, the only 2-piston brake to be used in pro World Cup downhill bike races."
heh
Yeah whatever, just take my money.
you've had yours a while now ... what do you think of the stock 2 piston model?
pretty much the same as I've said before...
Don't like the lever swing, works better with the shimano levers, heat management maybe a little bit of an issue on some trails. I 'think' I may have glazed a set on my dh bike. But they bedded back in and felt normal again. I certainly don't have any severe longing to replace them, I just think some better heat dispersion would be a good thing for the big bike. I'm not that big and I tend to run into trees instead of use my brakes so it's not a huge issue. Might be for some other heavier folks though.
Like all the other brands, the metal pads are awesome and the organic mixes are useless in the wet.
I've had it happen to one non-centerlock rotor. But a sample size of 1 is not statistically significant, is it?
btw Woo... how are those aluminum pots working out for you? have you been able to use them since "thre break" and with winter burying things under snow?
Sorry for abusing this as the general brake thread, but as i am open to improvement i might as well. So my new bike comes stock with Code RSCs, does anyone have experience with the new Codes? I'll admit that i last used an Avid product in 2008, but i hated every second of it back then and the Guides i tried briefly didn't exactly convince me in terms of ergonomics and power.
Do they still come with the pre-fucked master cylinder pistons that expand in heat (i.e. in a car sitting in sun)? All my friends with the Codes had to have the levers replaced under warranty.
Everything produced from around a year ago comes with the updated master cylinder. Maybe somebody more knowledgeable can tell the exact month for the production swapp?
The only SRAM brake that most SRAM-sponsored riders genuinely seem to like is the previous-gen code (gunmetal/chrome complete brake). Most people I know went out of their way / pulled strings to get those instead of the modern versions, and still seem to.
This season a bunch of the guys were given the new Code RSCs and the verdict was that they started off good but then deteriorated halfway through the season. I didn't pay too much attention but I did notice the throws started reasonable then got longer over time. That said, unless you can replace them with you-know-what, maybe just run them?
I recently took the gamble of ordering some lightweight disc rotors from ebay. Turned out to be Promax parts. Didn't hear about that company/brand before. Does anybody have any knowledge about them? http://www.promaxcomponents.com/
To me they look like your typical Taiwan catalogue brand.
Price was ~ 8 Euros for the 180 and ~ 9 Euros for the 203.
Optical quality is quite ok. No sharp edges. The narrow face sides seem to be coated. They have a somewhat soft touch.
Here is the 180mm one, 104 gr
And that's the 203 mm one, 147 gr
My idea was to put them on my light wheelset, for pulling the trailer through the woods. So no hard braking put a higher load to slow down.
Is anybody warning me about me gonna get myself killed and take one of my kids with me?
To me they look like your typical Taiwan catalogue brand.
Price was ~ 8 Euros for the 180 and ~ 9 Euros for the 203.
Optical quality is quite ok. No sharp edges. The narrow face sides seem to be coated. They have a somewhat soft touch.
Here is the 180mm one, 104 gr
And that's the 203 mm one, 147 gr
My idea was to put them on my light wheelset, for pulling the trailer through the woods. So no hard braking put a higher load to slow down.
Is anybody warning me about me gonna get myself killed and take one of my kids with me?
Necro bump.
I'm back to glycol based braking fluid in my recently bought R0R. Formula states that ONLY DOT 4 may be used, confirmed by an official rep. But he refuses to give me a technical reason or explanation. I can't find a reason why I would use DOT 4 over the lower viscosity DOT 5.1.
To make it short, what have you R0R users (@Udi @HAB ) been doing?
I'm back to glycol based braking fluid in my recently bought R0R. Formula states that ONLY DOT 4 may be used, confirmed by an official rep. But he refuses to give me a technical reason or explanation. I can't find a reason why I would use DOT 4 over the lower viscosity DOT 5.1.
To make it short, what have you R0R users (@Udi @HAB ) been doing?
@Flo33
I recently added a sheet to my brake spreadsheet (see tabs at bottom) with MTB-specific fluid recommendations.
I recently added a sheet to my brake spreadsheet (see tabs at bottom) with MTB-specific fluid recommendations.
But STILL relevant, at least for some of us. As for the 29r, that would be a welcome addition. Hell, do a 29 / 26 comparo as well, I can't be the only one that is looking at going to a 29" trailbike from a 26". I have a set of XO Trails that could get moved over....
Those numbers are approximations, but you lose roughly a further 6% (from 27.5" to 29"). The reason for the increased jump is because 27.5" is more like 27", but 29" is closer to actually being the jump the numbers suggest. Added to list.
So if you're going from 26" to 29" you'll lose a clean 10% braking force, and that's without accounting for inertial effects (which do become significant also, since it increases as a function of r^2 not just r).
For a 29" DH bike, I consider 225mm rotors a minimum, for a 29" trailbike 203mm rotors a minimum.
interesting stuff on that sheet WRT mineral oil. I have been using pentosin for years, which appears most similar to magura royal blood....but quite a bit different than shimano liquid gold. Maybe it's time to switch...
Found several discussions online that allegedly Magura royal blood is based on Castrol Vitamol V 10, if true it might give some more data for the Mix 'n' Match sheet.
I have 180f/180r on my trail bike and do 200,000ft+ of descending on that bike per year.
How much do you weigh? On my 27.5 Enduro bike I run 203mm rotors F&R with Hope E4s and just upgraded to V4s for more stopping power, with me in kit weighing ~90kg (200lbs). My girl runs 180mm F&R on her 29er Enduro bike and has no problems stopping but she's like 45kg.
A few years ago when I first got into trail riding I went from 97kg to 82kg in 12 months. My braking points changed substantially from doing that - it really was noticeable pulling up less weight coming into corners.
I'm probably ~180lb RTR. Just checked rather than guessing and it's been ~300,000ft of descending each of the last couple of years on my trail bike, Turner Burner.
Guide RSC's.
Guide RSC's.
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I'm running 180 mm rear, 203 mm front, and would like @Udi's cut...
203mm front / 180mm rear is probably a good bet given those circumstances/preferences.
You can obviously run anything you like (as evident above) but the disadvantage of small rotors on big wheels is not just the obvious braking force loss - it's less heat dissipation, which means pads see higher temps, and glaze more, so you start off with less braking force but then what you have gets worse faster too (long before the pads actually wear out, particularly in the case of full-sintered pads).
Every sintered pad suffers noticeably from this (organics/semis fare a bit better by wearing faster), the only notable exception is Shimano's heatsink pads (worth every cent of the premium for those who run Shimano or can fit those pads).
Weight is the only real downside to bigger rotors, but there are light options out there - my favourite is the Formula 203mm with alloy carrier, expensive but 143g is competitive with much smaller rotors and surface area is decent for the weight. The Shimano ice-tech 203mm is pretty good too at ~168g.
Aware of this, but my advice would just be to avoid it altogether.
It's the worst fluid on the list by far. Shimano oil is good and readily available.
@johnbryanpeters
FYI in case you were wondering, the big reason for keeping same size rotor front and rear (in this case 203mm rear) is that while the front generates the most braking force (and the rear can lock up with less), the rear also gets dragged a lot more particularly on descents - with the net result being that the rear pads get heat damaged much faster and to a greater extent.
I had this issue this lift season, and actually ended up running sintered pads on the front and organic pads on the rear to deal with it. The faster wear keeps the surface fresh instead of dragging on the same hard surface and causing permanent friction reduction.
Only a big problem with prolonged descents, with 203/180 I'd just change the rear pads if/when rear braking gets poor.
FYI in case you were wondering, the big reason for keeping same size rotor front and rear (in this case 203mm rear) is that while the front generates the most braking force (and the rear can lock up with less), the rear also gets dragged a lot more particularly on descents - with the net result being that the rear pads get heat damaged much faster and to a greater extent.
I had this issue this lift season, and actually ended up running sintered pads on the front and organic pads on the rear to deal with it. The faster wear keeps the surface fresh instead of dragging on the same hard surface and causing permanent friction reduction.
Only a big problem with prolonged descents, with 203/180 I'd just change the rear pads if/when rear braking gets poor.
Hi Udi, your list mentions Redline LikeWater. Is it this suspension fluid? https://www.redlineoil.com/likewater-suspension-fluid