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Of course you would. DOT fluid basically dissolves mineral oil (usually NBR) seals while mineral oil swells DOT (usually EPDM) seals. This has been known since forever.
Everybody says different mineral oils are not cross compatible and there have been some claims about seals degrading by using a mineral oil from another manufacturer, but comparing mineral oils is still like comparing different fresh water sources as opposed to DOT being something completely different than water.
Completely okay, whatever floats your boat.
My concern is missing the forest for the trees. Are you sure a light lever pull will give you less arm pump? What I'm reading from you is that closing the pad gap is what gives you arm pump. Not the fact that you then need to pull the finger orders of magnitude more strongly when actually applying the braking force.
I.E. Dominions with their apparently high lever force required to get enough braking force from them would give you less arm pump than a Brake requiring less lever force but a higher starting force. To me that makes no sense at all.
Speaking personally, I've never felt that my Dominions required a lot of force at the lever to get enough braking force, it's been the opposite in fact. I've ridden them at a lot of weights too, from 165ish lbs all the way up to 220 lbs, and on bikes weighing 32 lbs to 40 lbs on 203mm rotors, and they've been reliably powerful for how much force I put into the lever. As a point of comparison, I've spent a good amount of time on Code Stealth silvers, and those brakes required a lot more force at the lever to get the same stopping power as the Dominions. Not sure where the "Dominions have a light stroke but take a lot of force to get enough power out" is coming from to be honest.
Dominions are for sure the most powerful brakes with the lighest lever action I've used, I've never heard anyone saying they need a lot of force to get the power either.
On the other end of the spectrum you have the Formula Cura 4 which requires a lot of lever pulling to get any decent braking force - one of the most disappointing brakes I've used for sure.
This statement "Dominions have a light stroke but take a lot of force to get enough power out" sounds like a pad or rotor issue to me. I have tested the Dominions extensively against many other high-performance brakes, and while they fall just short of something like a Maven or a Hope EVO GR4, I still put them firmly in the "powerful brakes" category. They do have that superlight action as you initiate the brake, they then tend to bite pretty good on first contact and keep building from there. When compared to the absolutely effortless way the Mavens deliver their max power, sure, the Dominions require a bit more lever force, but definitely not to the point of "taking a lot of force to get enough power out." My experience covers a couple of different Hayes compounds BTW.
Found where it came from, I actually wrote it and got the info from a local rider who compared Dominions to Code RSCs. Page 54 apparently (asking for a friend situation). Then @Shinook more or less confirmed this: "I would flat out avoid Dominions. They aren't bad brakes but they are going to require a fair amount of lever force once the pads engage, the freestroke is light but the buildup in pressure required is fairly significant if you have problems."
Dunno, to me, physics wise, it's kinda clear. If you have a cam in the system, it's likely the free stroke lever pull will be stiff (moving the piston a lot), but you will get a lot of power, relatively, from the brake. It will build up quickly though. If you want a light lever pull, you have to run it more linearly and sacrifice ultimate power. Or pad gap. There's only so much finger stroke and force, so you're limited there.
Unless a light lever pull comes from a different place (maybe smoother bores or less pressure on the seals), that's also an option.
But let's stop beating this dead horse, apparently I'm all kinds of wrong.
Anyone know of an alternate Maven pad spacer (assuming 3d printed) that's sized for 2.3mm thick rotors? I like the SRAM pad spacer because it helps ensure even piston advancement/alignment after a bleed, but if you try to run 2.3mm thick rotors after using it, there's not enough clearance. My work-around so far has been to use the stock pad spacer to advance & center the pistons, then push them back with the thicker edge, then re-advance them over the rotor.
One complaint I have that applies to so many manufacturers is about rotors. Surely, it is possible to design floating rotors with replaceable brake tracks?
The waste and cost of throwing out really nice, expensive carriers when a brake track wears really annoys me. I get the critical nature of the rotor / carrier connection, but that’s solveable, surely?
Surely Galfer, Hope, Intend, or someone else could pull this off really quickly…
We live in a time where steerers are replaced. So even if it required tooling, that would pay for itself fast if a shop offered the service.
In my experience this is completely backwards.
I replaced Code RSC brakes (which replaced XT 4 piston) with Dominions. The Dominions require noticably less lever force to stop, by a substantial margin.
Iceman, have you written about your experience on the Hope GR4? I'd be curious to read it if so 🙂
Intend is working on something like that, there’s a small Italian brand probably only sells through Facebook, Billet, he does those, Serafino Billet,
He also makes alloy magnetic pistons for most brakes as a replacement
I kind of state the following in my opinion on the Dominions. I really don't think a light dead stroke matters as much as some people think. Since we don't spend most of our time in the dead stroke area but rather the bite point. The bite point tends to lead to brake fatigue in my experience and you can get just as much fatigue on a Dominion as any other brake. This is why a GR4 interests me...a lot.
I have indeed: https://www.vitalmtb.com/product/guide/hydraulic-disc-brakes/hope-technology/evo-gr4-69746#product-reviews-683186.
When I reviewed the Dominions for a mag back when they first came out, I discussed the design goals with Hayes themselves. They said that every aspect of the brake was designed to minimise resistance in the system while maximising stiffness. This includes seals, springs, and a larger ID for the hose than normal. This is the main reason that the Dominions are easy to pull. The linear lever with very little pad retraction is the other reason - the pads sit very close to the rotors. There was no sacrifice to leverage ratio or relative size of pistons that would affect the power.
Everyone that's concerned only about arm pump when talking about heavy/light levers is missing the forest for the trees. The amount of feel and control is increased also. On really wet slippery rides I have a distinct, obvious, glaring advantage compared to my friends on other brakes when modulating brakes to maintain grip. It's not a small effect. And that's while having more power than they do because they're all on either Shimano or code RSCs.
I threw rocks at a hornets nest in the replies. Anyway, I chose Hope EVO GR4s.
Ah yes, the Lever Blade-gate scandal 🤣
I was waiting on some GRs when the option for the TR the next day came up. There's so much power on hand I'm glad I didn't go for the GR. Sharing the pad with the current V4 (which I have on a different bike) and they feel stronger than the V4. I ended up dropping a rotor size front and rear (220/200 > 200/180). They've been incredibly solid after nearly 30,000m descending, it's hard to think of an improvement (except for replaceable rotor brake tracks...).
Have not heard of that personally except for people that have done adjustments beyond that little bite point screw. Some have experimented with trying to get that piston in there further causing what you experienced or worse.
If those are brand new, I would hit up Hayes.
I'm in the middle of doing some stupid brake tricks. In this case, Maven base lever assemblies (with Maven b1 lever blades) and db8 calipers. This started out with the idea of just using what I had on the shelf to finish a build and is turning into an exercise in finding a middle ground in weight and power between mavens and motives.
I blocked my system by messing with that push rod, but haven’t actually touched that bite point screw.
How is it working? I’m on db8 caliper Shimano xt lever for my front brake and it’s working really well, will see how it fares at a bike park in a couple weeks time though. Weirdly, the feel at the lever is very similar to the rear brake which is still full shimano.
Not to sound pedantic, but you'll be surprised at how many times this exact situ has been discussed in this thread. The contact/bite point adjust moves the piston position in the bore and if dialed in too much can cause the primary cup seal to pass over the timing ports, effectively closing the brake system. NBD, and lessons learned.
This might be my issue.
To be clear , what You have heard was from people who screwed this bite point screw in (pads closer to rotor) making whole system wiring incorrect?
The screw is tightened to max already from factory, what many of us tried is this Page 11, but it doesn't work, the dead throw in dominions is part of the brake and cant be altered.
The bite point is adjustable. The pushrod in the system advances or retreats the master cylinder piston, which decreases or increases lever throw to engagement. My main nit with the Doms is not with the brakes themselves, it's the bleed process they specify. That 'bar 45°, lever in neutral' allows an air pocket to remain the MC bore. Ideally before you set it in that position the MC should be rotated to 12 on the bar, similar to this EVD from the manual, to insure there's no air left in there.
I have also turned push rod fully clockwise as advised here by "TheFBI" somewhere on page 12 of this post. This however eliminate lever dead throw but still ,system keeps the full flow.
Where the situation changes (at least from what I experienced) I what also HexonJuan described couple posts later (6/16/2024 2:13pm).
I wrote to Hayes asking if tightening the bite screw will close the port and make bleeding impossible.Waiting for reply.
The answer is yes. Signed, one who got curious and had to try it out and see.
Reply from Hayes:
"The bite point does not effect bleed and does not need to be reset.
You don't need to adjust bite point as pads wear - the system advances the pads as needed."
And they are correct. If you however adjust the contact adjuster clockwise you can close off the timing port holes, effectively making the brake a closed system, proven when you can't push fluid through the system. The experiences on this forum show others having turned the contact adjust too far and caused the above issue. I experimented on the last set I installed and yep, You can close the timing port holes and then turn it counterclockwise to get the fluid to flow through again. And yes, the caliper pistons adjust for pad wear by design, a fundamental of disc brake design regardless of vehicle (mostly).
My point is simply I think most folx leave an air pocket in the MC bore when they follow the provided bleed instructions, which in turn gives the impression the contact adjuster doesn't do anything. IME it does have an effect on feel, providing a shorter stroke to contact.
Post a reply to: Nerding out on Brakes shall we? Not another tech deraliment