Runaway train!

[Waverider]

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]

"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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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.

 

[Waverider]

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.

Getting up to speed isn’t the problem

 

[Astro66]

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?

This thread seems to imply your brakes are the issue.

Your thoughts on SRAM's new DB 8 brakes

Anyone has tried the new SRAM DB8 mineral oil brakes (calipers, levers). I saw that many e-mtb brands are now fitting them on their 2023 models, from lower to higher end bikes. SRAM claims Code-like braking power. How do they compare with higher end brakes?

www.emtbforums.com

 

[irie]

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.

I think (and am sure if wrong will be corrected) that all Shimano 4 piston calipers from MT420 to BR-M9120 (XTR) have the same size pistons so all work pretty much the same, and all have ceramic pistons with the exception of MT420 which have organic pistons. I have BR-M6120 (Deore) calipers with BL-M6120 (Deore) levers which (IMO) is the 'sweet spot', paired with Swissstop Catalyst Pro 220mm rotors front and rear with stock Shimano D03s pads. Physics says that money spent on larger rotors is far more effective than if spent to obtain what are only marginal caliper and/or lever improvements. Can't argue with the physics, but Shimano is only available in black so if you want bling look elsewhere.

 

[Zimmerframe]

TRP's, though I think I prefer my XT's ..

No issues here (derestricted for a motor heat test), though I think sometimes there's a natural tendency to drag the brakes a bit sometimes when you don't need to, which can cause heat issues.

 

[Darren66]

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?

Uberbike E-Matrix SRAM Code - Code R - DB8 - Code Stealth Bronze/Ultimate/Silver E-Bike / Endurance Disc Brake Pads

For use with New style 2011 onwards SRAM Code, Code R Code Stealth Bronze/Ultimate/Silver and DB8 disc brake systems.

www.uberbikecomponents.com

I have a Crafty R with db8 brakes, I swapped the pads to uberbike e matrix and now they're good.

 

[Paulquattro]

Welcome
Speeeeed

 

[Waverider]

Thanks for everyone’s responses, I did put some hs2 discs and Dt swiss pads on which helped, but maybe based on this I’ll look at a full upgrade. I guess I hoped for a bit more on riding technique rather than a deep dive on brake tech but fun to read nonetheless!

 

[irie]

Thanks for everyone’s responses, I did put some hs2 discs and Dt swiss pads on which helped, but maybe based on this I’ll look at a full upgrade. I guess I hoped for a bit more on riding technique rather than a deep dive on brake tech but fun to read nonetheless!

If you do have a problem with your brakes:

Are you getting brake fade? Yes or No

Can you lock the brakes at any speed? Yes or No

Do your brakes lack "feel"? Yes or No

Do your brakes work consistently? Yes or No

Exactly what is your braking problem?

If you do not have a braking problem then what is the "riding technique" problem you want help in solving?

 

[RustyIron]

I guess I hoped for a bit more on riding technique rather than a deep dive on brake tech

Ahhh... well that's a whole 'nother thing.

If you're dragging your brakes to manage speed, you might be creating a lot of heat that doesn't dissipate, and you end up with fade. If you insist on dragging the brakes, ride slower, and the heat will have more time to dissipate.

A better solution would be to be judicious in your application of the brakes. Use your braking less frequently, but maybe harder. You create a lot of heat very quickly, but then you let off the brakes, allowing some time where the heat can dissipate. Braking super hard isn't always possible, but every downhill run will have some features that you can utilize to your advantage. Suppose there's a little dip; when you hit the bottom of the dip and start coming out, you have extra force driving the tires into the ground, and it's the perfect time to shed some speed. It's the same if you can spot a little berm-like feature. Lean into it a little bit, and use the extra traction as an opportunity to give it some extra braking.

Bottom line, I suppose, is watch for places where you can give it a little extra brake, and always be aware of heat buildup.

 

[steve_sordy]

................. If you get scared then go slower to start with or take up knitting.

Harsh, but funny!

 

[irie]

Ahhh... well that's a whole 'nother thing.

If you're dragging your brakes to manage speed, you might be creating a lot of heat that doesn't dissipate, and you end up with fade. If you insist on dragging the brakes, ride slower, and the heat will have more time to dissipate.

A better solution would be to be judicious in your application of the brakes. Use your braking less frequently, but maybe harder. You create a lot of heat very quickly, but then you let off the brakes, allowing some time where the heat can dissipate. Braking super hard isn't always possible, but every downhill run will have some features that you can utilize to your advantage. Suppose there's a little dip; when you hit the bottom of the dip and start coming out, you have extra force driving the tires into the ground, and it's the perfect time to shed some speed. It's the same if you can spot a little berm-like feature. Lean into it a little bit, and use the extra traction as an opportunity to give it some extra braking.

Bottom line, I suppose, is watch for places where you can give it a little extra brake, and always be aware of heat buildup.

Bottom line is, we really don't yet know what the OP's problem is.

 

[Waverider]

Bottom line is, we really don't yet know what the OP's problem is.

The conservation definitely has lent into braking but I only see that as part of it. When I ride twisty tech trails, off camber or fast corners etc. the momentum - behaviour of the bike can be disconcerting, I’ve got stock ish fox settings, decent maxxis assagai /dhr tyres with inserts but I think the bike has more to give so setup and technique are probably areas to improve on top of confidence in the brakes. I’ve been riding regular bikes for a while so I know a bit of what I’m about, but this one has had me a bit stumped for getting dialled in when gravity takes over.

 

[irie]

The conservation definitely has lent into braking but I only see that as part of it. When I ride twisty tech trails, off camber or fast corners etc. the momentum - behaviour of the bike can be disconcerting, I’ve got stock ish fox settings, decent maxxis assagai /dhr tyres with inserts but I think the bike has more to give so setup and technique are probably areas to improve on top of confidence in the brakes. I’ve been riding regular bikes for a while so I know a bit of what I’m about, but this one has had me a bit stumped for getting dialled in when gravity takes over.

 

[Mikerb]

I did say earlier in this thread that assuming you were not getting brake fade due to heat and you can lock at least the rear wheel when applying the brake ( not that doing so will help a lot to reduce speed!) your issue is a bout managing your speed to match the features you encounter on a steep descent. Whilst you may well have been a ble to put a dent in the speed of a much lighter analogue EMTB, that may well not be the case with a 25kg bike. On an analogue bike you may well have chosen to add in additional pedal strokes to maintain or increase speed..........on an EMTB the bikes momentum mostly makes that uneccessary.
Take a leaf out of motor racing. You leave the brakes alone most of the time but when you do brake it is done hard and short whilst on the straight before a corner. The car/bike is then a ble to settle leaving its supension free to do its job. Brake too late and you compress the front suspension and/or lose traction. Brake early and the car/bike is then settled and your concentration can be 100% on line choice and technique for whatever you hit...corner, drop, jump ramp etc.
Stay centred over the bike with flexible knees and arms. That way you have some chance of both brakes finding traction and letting the bike "float" rather than allowing your weight ( probably 3+ times the weight of the bike) to stuff the bike into the ground. Corners at speed with a heavier bike need good bike lean with bike/rider separation...especially if it is an unsupported bend ( ie not a berm).
Sorry if I am teaching a grandmother to suck eggs...but you did ask!!