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Mineral Oil v. DOT Fluid Brakes in Winter

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#61 ·
mtnbkrmike said:
You're absolutely right. Maybe I should just keep the Guide Ts on both of the incoming bikes, which (like yours) are also set up with 200/200 rotors.

DOT? Check.

No more massive bank account hemorrhaging? Check.

Thanks, and sincere apologies for my comments.
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No worries, no offense taken. As I said I'm not a fan of the Guide Ts, and have yet to go through winter with them. But I think they will be OK, at least for winter fatbike use. Other than the heavy tires, my demands of them should be fairly modest compared to my typical trail riding.

The SLXs should be the superior brake by far in fair weather. It will be interesting to see if that still holds true in the cold.
 
#62 ·
mtnbkrmike said:
These will make an even dozen (including 2 of my daughter's). Just like a box of donuts! I thought I needed an intervention (and some serious counselling) but reading about your 18, I feel somewhat relieved about things :thumbsup:
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Many of the collective are from 45 years of collecting. Those that made the cut earned a special place in my heart. All are operational.
 
#66 ·
Could you experiment by leaving your bike outside for several hours at the very low temps you are concerned about and then riding it to see how the brakes change? I'm wondering how/if things would be different in this test vs riding for 4 hours or whatever? Occasional braking?
 
#67 ·
king_dave72 said:
Could you experiment by leaving your bike outside for several hours at the very low temps you are concerned about and then riding it to see how the brakes change? I'm wondering how/if things would be different in this test vs riding for 4 hours or whatever? Occasional braking?
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That could be done but why not stick the bike between your legs and start pedaling? Seriously, how often is braking needed as you cruise along without a care in the world because bikes are so freakin awesome. Frankly, it doesn't take long for the bike to get chilled to the environment so if a brake is going to become sluggish from low temp, it won't take long. Kinda like setting fatbike tires in the living room to 5 psi and out the door and a block and a half later the tires are at 3 psi...
 
Discussion starter · #68 ·
Came back to say that I was wrong about the Guide T brakes. They have performed like a champ. Absolutely no need to replace them. Very glad I did not.

Haven't had any cold weather yet (this evening we rode in minus 5 C temps). So far so good.

Thanks again everyone for talking me out of changing them. That would have been a crap decision. Especially if they keep performing like they are, once we get to minus 15 C temps and colder.
 
#69 ·
-5F/-21C here today. I rode the bike with the XTRs. The sole reason for those brakes on the bike is the CF lever blade, but the brakes definitely sucked in the cold. It definitely took a little while for them to get fully cold-soaked (bike is at room temp inside when I start) but after a while they were pretty stiff and they'd pack-up with the lever point moving out. Not as bad as at -20F obviously, but not good. This is with HPX 2.5 that is much less vicious than shimano MO in the cold. To that extent, it did take maybe 30-45 min for then to degrade to where I noticed the serious performance/operation issue. On the faster trails with more vertical/DH I was longing for my Hopes.

But if you aren't going down this far much, if ever, then they are probably ok. The HPX makes a definite improvement, but not on the scale that would make them operate like a DOT brake.
 
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#70 ·
prlundberg said:
Not really. DOT fluid is designed to a higher standard. That's just a fact. Mineral oil may be perfectly sufficient for your needs and many bike brakes that use it are objectively better than many that use DOT, and there are several non-performance advantages to mineral oil, but that does not mean mineral oil performs better as a brake fluid.
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Actually not so much a higher standard as a universal standard. All DOT fluids from all manufacturers have to meet a certain minimum test standard for that grade of fluid. However that doesn't mean they're automatically better than non DOT fluids.
 
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#71 ·
DeeEight said:
Actually not so much a higher standard as a universal standard. All DOT fluids from all manufacturers have to meet a certain minimum test standard for that grade of fluid. However that doesn't mean they're automatically better than non DOT fluids.
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DOT has to meet high and low temp certification and is far easier to source than baby oil. On the low end of temps, oils will increase in viscosity. DOT has to maintain viscosity within the range set forth in SAE standards where mineral oil is not monitored to such stringent requirements.

No, that doesn't go to say one is "better" than the other since they both function without compression to detract from hydrostatic forces needed to operate the system satisfactorily.
 
#72 ·
Jayem said:
-5F/-21C here today. I rode the bike with the XTRs. The sole reason for those brakes on the bike is the CF lever blade, but the brakes definitely sucked in the cold. It definitely took a little while for them to get fully cold-soaked (bike is at room temp inside when I start) but after a while they were pretty stiff and they'd pack-up with the lever point moving out. Not as bad as at -20F obviously, but not good. This is with HPX 2.5 that is much less vicious than shimano MO in the cold. To that extent, it did take maybe 30-45 min for then to degrade to where I noticed the serious performance/operation issue. On the faster trails with more vertical/DH I was longing for my Hopes.

But if you aren't going down this far much, if ever, then they are probably ok. The HPX makes a definite improvement, but not on the scale that would make them operate like a DOT brake.
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FYI, Hayes recently released a lighter version of their 2-piston Dominion with carbon levers.

I snagged a few sets but they're more for new summer bikes.

The wife and I are both on cheap mechanicals with carbon v-brake levers on our snowbikes. Plenty of power if crappy modulation. Good enough tho.
 
#73 ·
mikesee said:
FYI, Hayes recently released a lighter version of their 2-piston Dominion with carbon levers.

I snagged a few sets but they're more for new summer bikes.

The wife and I are both on cheap mechanicals with carbon v-brake levers on our snowbikes. Plenty of power if crappy modulation. Good enough tho.
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Yeah the carbon lever may push me towards the hayes, good to know.
 
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#74 ·
mtnbkrmike said:
Came back to say that I was wrong about the Guide T brakes. They have performed like a champ. Absolutely no need to replace them. Very glad I did not.

Haven't had any cold weather yet (this evening we rode in minus 5 C temps). So far so good.

Thanks again everyone for talking me out of changing them. That would have been a crap decision. Especially if they keep performing like they are, once we get to minus 15 C temps and colder.
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Eventually, someday, real winter will return and then we'll all remember that most brakes are plenty powerful enough. It's the snow/tire interface is the real limitation. Uphill, downhill, and sideways!

I often wanted more power out of my old Level T's in the summer, but I never had a complaint in the winter. Snow ain't dirt!

Have fun on the new bikes.
 
Discussion starter · #75 ·
CanmoreBruce said:
Eventually, someday, real winter will return and then we'll all remember that most brakes are plenty powerful enough. It's the snow/tire interface is the real limitation. Uphill, downhill, and sideways!

I often wanted more power out of my old Level T's in the summer, but I never had a complaint in the winter. Snow ain't dirt!

Have fun on the new bikes.
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True. True. That said, not sure how Canmore is right now but West Bragg is mostly dirt. This weekend, 90% of the bikes out there were non-fatties. It was like late spring conditions.

I have Guide Ultimates on my Druid, which are fine. These Guide Ts feel no different. 200mm rotors front and rear help.

One thing about Guides (that I really like) - I do not find them weak, but I also never skid with them. Which in is good when you are blasting along on dirt and rock with brand new studded Wrathchilds.

And thanks! Hope to cross paths with you sometime this winter.
 
#76 ·
mtnbkrmike said:
True. True. That said, not sure how Canmore is right now but West Bragg is mostly dirt. This weekend, 90% of the bikes out there were non-fatties. It was like late spring conditions.
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Yeah, things is tough all over. Some areas are bare dirt, others have bit of firm snow cover, others are death ice. Highly variable by trail, aspect, elevation and sun exposure. No simple answer to 'which bike?' or 'which tires?' in these conditions!

I don't get to WBC as often as I should, mostly I'm doing laps around Canmore, often in the dark. But I'll keep an eye out for those fancy new bikes of yours!
 
#78 ·
I purchased my fat bike in 2021. It came with Shimano 6120 4 pots. Brakes failed in less than a year. Brake fluid leaked from the calipers contamining the pads. My bike shop replaced the calipers etc under warranty. Now the rear caliper has failed again. Looks like its leaking from the transfer port.
 
#79 ·
Did a night ride in -5f temps last year. That's about as cold as I've ridden in but hadn't had any problems before. I had Shim mineral oil brakes and they were sluggish and draggy in that cold. Then they squealed like crazy. I put some G2 SRAMs on the bike I just built so we'll see how that goes.
 
#80 ·
Dean Williamson said:
I purchased my fat bike in 2021. It came with Shimano 6120 4 pots. Brakes failed in less than a year. Brake fluid leaked from the calipers contamining the pads. My bike shop replaced the calipers etc under warranty. Now the rear caliper has failed again. Looks like its leaking from the transfer port.
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Shimanos have been hit or miss for me for a few years now. They used to be my go to brake but I've had to deal with leaky caliper seals such as you describe several times in the last 10 or so years. I still prefer mineral oil brakes though, and have had decent luck with Maguras on my fat bike and trail bike. They do come with their own challenges-the close tolerance at the caliper/rotor that makes rub-free set up tough. But I'm on my 8th season with the Magura MT-4s that came stock on my Voytek and they've needed nearly no attention at all. I still have Shimano brakes in my fleet but given the choice if I were equipping a bike now, I'd probably go with Maguras.
 
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