Runaway train!

Waverider · 2024-11-20T19:11:59+0000

Hi there, first post to the forum and had my Mondraker chaser r for 11 months now, been riding naturally aspirated MTB for years before that. One of the things I’ve not quite got my head around is the run away train feel on fast descents. I’ve made some upgrades with brake discs and pads now much better than stock, the bike seems setup ok, how do other full fat ebike riders feel about it? Should I ditch the db8’s and get better brakes?

DieBoy · 2024-11-20T20:21:45+0000

"Runaway train never going back
Wrong way on a one-way track
Seems like I should be getting somewhere
Somehow I'm neither here nor there"

Can't help you sorry, but your post title gave me an earworm, and the chorus lyrics are somehow appropriate.

RebornRider · 2024-11-20T20:33:45+0000

I share the trails on my regular ride with walkers, their little kids, and their dogs (usually with no leash). There are some long, steep descents, and it seems as though I always encounter the walkers on those descents. That means slowing from 25-ish mph to maybe 5 mph so I can pass them without scaring them. On a steep downhill.

Because of all that, I switched to Magura MT7s with their 220 mm rotors front and rear. No more fade, no more howling. I really appreciate having 100% confidence in those brakes! I'm not claiming my setup is the best available. It meets my needs.

Husky430 · 2024-11-20T20:38:31+0000

Maybe it just feels that way if you have spent most of your life riding relatively light clockwork MTBs.
With the extra weight of an ebike (motor, battery and burlier frame to accommodate said hardware) it might just feel that way to you, my experience tho is that the bike is much more 'planted' and less likely to defect off small imperfection in the track so sort of saying that part of the 'runaway train' feeling is that it is more like it's on a track and goes pretty much where you point it?
Just my 2 cents worth and I have no scientific back-up to this theory, just my gut feeling.

steve_sordy · 2024-11-20T20:45:03+0000

I don't get that feeling at all. My brakes are Shimano XT, with resin pads. Maybe I never go fast enough. To me 30mph is a suicide speed, even on the flat!

RebornRider · 2024-11-20T20:58:47+0000

Maybe this elevation graph will explain my situation. Quite a bit of descending from mile 15 to about mile 17.5. Even when I don't encounter walkers, each of the steep segments ends with a tight, slow 90 degree turn.

Mikerb · 2024-11-20T21:24:16+0000

An EMTB has more momentum and that usually translates to faster speeds on downhill trails..........to compensate the bike is much more planted and stable. You have 2 choices..........trust the bike, get used to the speed and enjoy it.........or control your speed with early braking rather than expecting the bike to stop on a dime just because you apply the brakes. That means reading the trail well ahead especially if you do not know any particular trail.

Invariably braking traction is the limiting factor rather than the difference between one brake and another unless your descents are long enough to generate too much heat in the brakes and on a descent the front brake is far more effective than the rear simply because the weight of the bike and rider are on the front of the bike. Front brake braking is however only really safe if the the front wheel is fairly straight!!

Husky430 · 2024-11-20T22:05:49+0000

steve_sordy said:
My brakes are Shimano XT, with resin pads.

I in Steve's boat with the same brakes and pads and find them to be more than adequate so maybe just need to update your brakes?

HandsomeDanNZ · 2024-11-20T22:41:15+0000

Husky430 said:
I in Steve's boat with the same brakes and pads and find them to be more than adequate so maybe just need to update your brakes?

Yeah I run SLX with large rotors and finned pads.
Basically they are slightly less adjustable and slightly heavier XT brakes.
I am heavy, my bike is heavy and my brakes are more than a match for anything I can throw at them.

RustyIron · 2024-11-20T23:35:02+0000

Waverider said:
One of the things I’ve not quite got my head around is the run away train feel on fast descents.

Hmmm... I don't really understand what you're saying. Do you mean that you're squeezing the brakes as hard as you can and they don't slow the bike down? Are the brakes strong enough to lock up both wheels but they just skid along the ground as you pick up speed? Please elaborate.

Waverider · 2024-11-21T00:05:11+0000

Husky430 said:
Maybe it just feels that way if you have spent most of your life riding relatively light clockwork MTBs.
With the extra weight of an ebike (motor, battery and burlier frame to accommodate said hardware) it might just feel that way to you, my experience tho is that the bike is much more 'planted' and less likely to defect off small imperfection in the track so sort of saying that part of the 'runaway train' feeling is that it is more like it's on a track and goes pretty much where you point it?
Just my 2 cents worth and I have no scientific back-up to this theory, just my gut feeling.

I definitely feel it’s more planted, but the momentum it carries doesn’t feel confidence inspiring through fast corners I guess. Running out of talent probably covers some of it!

Waverider · 2024-11-21T00:09:16+0000

RustyIron said:
Hmmm... I don't really understand what you're saying. Do you mean that you're squeezing the brakes as hard as you can and they don't slow the bike down? Are the brakes strong enough to lock up both wheels but they just skid along the ground as you pick up speed? Please elaborate.

I have had the brakes not be able to stop me enough after some scary dh tracks during an enduro stage for sure. Replaced the pads and discs since which has helped. The way it carries speed into things catches me out even now though.

Waverider · 2024-11-21T00:11:22+0000

HandsomeDanNZ said:
Yeah I run SLX with large rotors and finned pads.
Basically they are slightly less adjustable and slightly heavier XT brakes.
I am heavy, my bike is heavy and my brakes are more than a match for anything I can throw at them.

I have just put 2 pot slx on my xc bike and I like em

so good to know

Waverider · 2024-11-21T00:12:41+0000

I have to say this forum seems to get way more interaction and comments than any I’ve started on before. Thanks and kudos people!

RustyIron · 2024-11-21T03:53:11+0000

Waverider said:
I have had the brakes not be able to stop me enough after some scary dh tracks during an enduro stage for sure. Replaced the pads and discs since which has helped. The way it carries speed into things catches me out even now though.

While your DB8's aren't top-of-the-line, your bike looks like it came with 200mm rotors, which should be satisfactory. You mention "fast descents." If the brakes are ok at slow speeds, but not on prolonged high-speed downhills, perhaps you're experiencing brake fade. Better brake pad material can help. But if you're a picky sort, maybe you'll be happiest with some top-shelf brakes. I think the best deal around is Shimano XT. Their XTR and Saints are great, too, but more money. I'm currently running TRP DH-R's, but not long enough where I can say with certainty that they're the bomb.

irie · 2024-11-21T04:14:25+0000

Waverider said:
Hi there, first post to the forum and had my Mondraker chaser r for 11 months now, been riding naturally aspirated MTB for years before that. One of the things I’ve not quite got my head around is the run away train feel on fast descents. I’ve made some upgrades with brake discs and pads now much better than stock, the bike seems setup ok, how do other full fat ebike riders feel about it? Should I ditch the db8’s and get better brakes?

I'm 78kg ready to ride on a relatively heavy (25kg) 2022 alloy Trek Rail with Shimano SLX brakes with organic pads and Swissstop 220mm rotors. Great feel, stops from any speed, never get brake fade. When hitting 20+ mph downhill of course I'm sitting on a directional missile, it's the nature of the beast. If you get scared then go slower to start with or take up knitting.

Runaway train!

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