I've always run hydraulics discs on my bikes and I've never had a problem with them, but mechanical appeal to me for ease of changing cables, flights etc. However, as the fat bike is for the Rovaniemi150 next year, which are more reliable in cold (possibly -30c) temperatures? I'm thinking that the hydraulic seals may fail in the cold temperatures, whereas there is great danger of mechanical feezing if water gets in the cables?

Pop some hydro fluid in the freezer and see what happens!

Not very helpful I know but I'm also curious. Cable discs seem to be touted as less of a problem but a decent set of hydros is largely fit and forget.

Both Shimano and Hope brake fluids should be good down to -50°C - I guess that other manufacturers' fluids would be ok too. If you get the spec for the fluids, look for the melting or pour point temperature. I haven't been able find out what material they use for the seals but that would be limiting factor in hydraulics, I think. There certainly are grades of rubber that go down to those temps, but whether they work at the high temps you'd also see in a brake I don't know.

I think I'd be inclined to use hydraulics.

johnnystorm wrote:a decent set of hydros is largely fit and forget.

Not so much of the largely in my very recent experience :?

Brake fluid will start to freeze at around -59 C. There is the issue of the fluid absorbing water over time but at most that's only 3% (by volume) so it's unlikely to cause a problem.

The issue of seals is something else but having a wild stab I'd suggest that the seals on a bike aren't made from anything different to those used on other brake systems and they cope okay.

I think you really need to consider .... you're entering a 150 mile race which will feature snow, ice and minus stupid ... just how much riding that requires brakes do you think you'll actually be doing?

for what its worth my Mukluk comes as std with cable brakes

not sure if Salsa spec that out of price or due to the conditions they expect it to be ridden in

appreciate that doesn't help much

oh yes, I remember talking to Jeff Jones a few years ago at SSWC in Scotland and he told me that he ran cable brakes because of the cold. I guess he know's a thing or two about bikes

It certainly seems to be the case that cable disks are the default for all the bikes originally being used in Alaska etc. I've never seen that as a problem and just went with that when I specced up my 97. I've used BB7s on CX bikes before too.

Last year, I took some XTR hydros off a bike I wasn't then using and put them on the 97 instead, for no reason other than it seemed a shame to having them and not use them.

Summary? It makes little difference in normal conditions.

My first reaction to this was cable disks due to ease of maintenance if something we're to go wrong. But at minus 30 It sounds as if big gloves will be a necessity which means that you may not have the dexterity to tackle some mechanical issues anyway.

Also think about the freezing temperatures of the lube used inside the outer cables on mechanical brakes. This might result in your brakes freezing solid. For these reasons I'd go for some bombproof hydraulics. Probably something by Shimano or Hope (anything but Avids).

Just out of interest, do you have a plan in place for preventing your hub pawls/ gear cables from freezing up?

Just out of interest, do you have a plan in place for preventing your hub pawls/ gear cables from freezing up?

I don't think I was the only one to suffer with frozen gears at T n b and I reckon it was only about -3

johnnystorm wrote:Pop some hydro fluid in the freezer and see what happens! .

Think I'm going to put myself in the freezer and see what happens

s8tannorm wrote:I think you really need to consider .... you're entering a 150 mile race which will feature snow, ice and minus stupid ... just how much riding that requires brakes do you think you'll actually be doing?

This did occur to me and I'm hoping it should on be the once, either when I bail and end up in a wreck or when I cross the finnish line (geddit??).

barney wrote:oh yes, I remember talking to Jeff Jones a few years ago at SSWC in Scotland and he told me that he ran cable brakes because of the cold. I guess he know's a thing or two about bikes

This guy talks sense, so I'm going with cables.

Lmorgan87 wrote:Just out of interest, do you have a plan in place for preventing your hub pawls/ gear cables from freezing up?

A site in the US of A (fatbikes.com) has some grease that Kid from Salsa recommends to use, its been tested on the Iditarod, so it should work fine. The bike is being built up as a geared bike but I may change it for the race.

So in summary, I'm going to get cables put on the bike for two reasons, it what Salsa and Surly spec on their fat bikes an secondly, I have a set of hydraulics on my Salsa El M, so if I have got the wrong end of the sticl, I can always change them over before the race and I have lost out :)

Cheers for all the advice/ideas. Guess I'll never quite find out which one was correct unless something goes wrong mid-race

Might seem silly, but why not one of each? That way if your cable froze, you'd still have a hydraulic, and if your hydraulic seal failed, you'd still have a cable?
Just a thought, would hardly be a cheap option but might give a sort of "best of both worlds"?
Atb, enjoy the race :D
Ben

What does Aidan use for the Iditas? I'd just use the same. I've noticed shimano hydro pistons getting stickier (tighter seals?) in UK cold and the reduced clearance packing with snow or jamming with melt-freeze, seems less of that with BB7s. Never ridden in colder than minus a few degrees here though so that may be junk info ) One thing I do like about BB7s is knowing that your bike will survive the trip to the start of a ride without anything happening that can't be fixed easily yourself.
This helped stop the snow getting in and packing out the brake during last winter's snow rides -

http://www.aidanharding.com/2013/10/look-north/
Looks like your choice is correct Simon. A good read too.. I've always been fascinated by the Iditarod.