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need to upgrade our hydraulic brakes what should I ask for?

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need to upgrade our hydraulic brakes what should I ask for?

Old 08-04-20, 09:30 PM
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fooferdoggie 
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need to upgrade our hydraulic brakes what should I ask for?

this is on ort e tandem between the wife and I and the beast its over 400 pounds. the Shimano deore hydraulics with 203 rotors have issues. the front starts making noise after a couple minutes of long braking and when we are going down steeper slopes on mountain bike trails we my not be able to fully stop if needed. plus we have to use the back more to keep the front wheel from sliding sideways. so I guess its time for 4 piston brakes. they have to work with my bosch setup. I love the Magura e bike brakes on my other bosch bike they are really powerful 2 piston brakes. so their 4 should be really good. or should Stick with Shimano ? and if so what ones? what kind of rotors should I get?
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Old 08-04-20, 10:18 PM
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Basically what you have there is an issue of basic physics. You are trying to get rid of kinetic energy in the form of heat from the disc, once you reach a certain level of brake functionality improvements aren't going to make a huge difference, ie Deore Calipers are pretty good, 4 piston will reduce lever effort a bit, but still won't stop brake fade, which is due to heat build up. You need to be getting rid of heat faster. Normally I'd say do more pulse braking, short bursts of braking to dump heat into the discs fast and then breaks to allow them to shed heat. But on a tandem on gravel, that's hard to do. So another avenue is to upgrade the discs and pads. Given you're already at 203mm rotors I'd go for something like the Icetech Freeza, but they are only in centrelock https://bike.shimano.com/en-AU/produ.../RT-MT900.html or something like this in 6 bolt https://www.uberbikecomponents.com/v...Fins-GoldBlack - Discs with maximum surface area and conductive alloy to help shed heat. Pads something like the finned Icetech Metallic ones. Metallic will stand up to heat and abuse more, at the expense of accelerated disc wear and the fins help get rid of heat.
You can get dual disc front hubs, but I don't know of any dual disc suspension forks...
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Old 08-05-20, 07:42 AM
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yes there are limits but even riding the tandem by myself the brakes are not as strong as my regular e bike with only 180 rotors. so the brakes are lacking. I do have center locks and I just bought some copper backed koolstop pads that I will hope that helps. but when your going down a steep trail slowly and you cant stop because you have ran out of braking power you need to upgrade.
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Old 08-05-20, 02:26 PM
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I am assuming that you have a flat bar bike. I have a Ritchey Double Switchback tandem and I have Hope V4 brakes with an IceTech 203 mm in front and a vented Hope 203 mm rotor in the rear. The loads we put on our brakes when fully loaded are similar to what you are talking about.

Trevtassie is correct that the main issue is getting rid of heat, but the brake's ability to function when hot is also a factor. The Hope brakes tolerate heat well, and my experience with the vented rotor is that it will dissipate heat faster than the IceTech. Several brands of DoT fluids have very high boiling points, which will help with heat tolerance. Castrol SRF comes to mind as one of the higher boiling point fluids. Shimano and Magura are both very good products, but they are mineral oil systems, and they may not tolerate heat as well as a DoT fluid brake system.
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Old 08-05-20, 05:49 PM
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First they told us that traditional road-bike rim caliper brakes were inadequate (and Arai drum brakes were old-fashioned.) So we got cable disc brakes. Normal braking wasn't really any better (except sometimes in the rain) and once enough people had used them to descend long steep grades -- hardly any tandem teams actually do this because hardly any tandem teams, present company excepted, can climb long steep grades to begin with -- it became clear that they get hot enough to fade, just like rim brakes do. (OK,they can't blow off a tire but they can eject a front wheel, which is pretty bad, too.) So they said to get hydraulic disc brakes. One-finger braking, sounds awesome. But you still have to turn kinetic and potential energy into heat, and in dissipating that heat you're limited by the mass and thermal properties of the brake rotor, which doesn't care whether the linkage between it and your hand is cable or hydraulic fluid. So now the big tester of brake capability becomes large heavy people trying to bring heavy e-bikes down steep mountain-bike trails...and we find that hydraulic brakes don't cut it, either, in the domain that really matters to a tandem team: controlling speed on a descent and still having brakes cool and undamaged enough to stop quickly. "Yes, Martha, these brakes held our speed down to 40 km/hr all the way down that hill. Only trouble was we were still going 30 km/hr when we went through the stop sign."

So what next? Will we see two large disc brakes on each front wheel (with through axles to prevent ejection) plus the one on the back? Rim brakes too, for that final last-ditch (literally) stop when the discs have packed it in? Retro-rockets? Attach a railway tie to the bike with a logging chain and drag it down the hill?
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Old 08-05-20, 06:55 PM
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I can take care of the heat issue on long decent but it would be good to have better cooling. when when we are going down steep paths I want to be able to stop. we were only going maybe 10mph and we cant fully stop. when the grade is around 15% thats my main goal. but cooling would be good too. yes we have flat bars so that gives a lot more choices. but there is a issue. when I put the 203 rotor on it was fine on the test ride with it but with the wife and I the disc would rub sometimes on the fork or when braking hard bumps or peddling hard. so I took a angle grinder to the corner and got it so art just does not rub but once in awhile. so I am worried that one of the cooling discs will be farther out from the rim and rub. if so I would have to go with a 180 on front with a 4 piston. my wife is blind os no hot dogging for us (G) or she freaks out. anything blower 15% grade and it is no problem climbing with assist. 16% is a lot of work even with full assist and the bosch motor is pretty powerful.




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Old 08-05-20, 11:07 PM
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Originally Posted by fooferdoggie View Post
I can take care of the heat issue on long decent but it would be good to have better cooling. when when we are going down steep paths I want to be able to stop. we were only going maybe 10mph and we cant fully stop. when the grade is around 15% thats my main goal. but cooling would be good too. . . .
You are missing the point of @Trevtassi's physics lesson: "the heat issue" and "can't fully stop" are not two separate desiderata of which only the second is essential, and the first merely a "nice-to-have". Instead they are the same thing. Assuming you can stop OK, once, on level ground, the reason your brakes are failing during descents is that they get too hot. They get too hot because energy is being put into them too fast for the resulting heat to be radiated and convected away to keep the temperature at a value low enough for the brakes to keep working.. This is a nice way of saying you and your vehicle are too heavy for your brakes, just like an over-loaded coal truck trying to descend Kelly's Mountain (in Cape Breton, Nova Scotia) where you have to first make a hairpin to the right halfway down and then a sharp left curve at the bottom for the Seal Island Bridge.

There used to be a rule of thumb that said you should never try to ride down a hill that you couldn't ride up. Motorized bicycles allow this rule to be violated with the result that heavy weights find themselves at the top of a hill with no safe way down, a fact they discover only when brakes fail part way down. Electrically assisted bicycles intended to lift heavy weights should have dynamic braking like railway locomotives do, to supplement the friction-based brakes and prevent runaways. (This would add to the weight of the vehicle and be unpopular with bicyclists, as is typical for equipment intended to make the bike go slower, not faster.)


Otherwise, stay out of terrain that you cannot negotiate safely.

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Old 08-06-20, 03:58 AM
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Originally Posted by DangerousDanR View Post
I am assuming that you have a flat bar bike. I have a Ritchey Double Switchback tandem and I have Hope V4 brakes with an IceTech 203 mm in front and a vented Hope 203 mm rotor in the rear. The loads we put on our brakes when fully loaded are similar to what you are talking about.

Trevtassie is correct that the main issue is getting rid of heat, but the brake's ability to function when hot is also a factor. The Hope brakes tolerate heat well, and my experience with the vented rotor is that it will dissipate heat faster than the IceTech. Several brands of DoT fluids have very high boiling points, which will help with heat tolerance. Castrol SRF comes to mind as one of the higher boiling point fluids. Shimano and Magura are both very good products, but they are mineral oil systems, and they may not tolerate heat as well as a DoT fluid brake system.
Oh yeah, that Hope vented rotor looks like the shizzle! Means new Calipers but 400lbs means a lot of heat! And a 6 bolt hub or centre lock adaptor if it didn't push the disc too close to the forks. I'd be thinking to get different forks with a through axle anyway, I'm not a fan of heavy weights with discs and QRs (says he who has QR on his Troll, 203mm and regularly hits 320lbs when touring, I've sent discs blue and burnt the paint off pads before)
Dan is also right about DOT fluid coping with heat (water contamination) better, It can absorb a bit, mineral oil just allows it to settle at the lowest point so when the caliper gets hot it boils making compressible steam..
There may also be a hand strength issue as well, so maybe the 4 pot Hope caliper would help.

Last edited by Trevtassie; 08-06-20 at 04:06 AM.
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Old 08-06-20, 07:32 AM
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when I say short hills I am saying a few hundred feet far to short to build up heat.. when I ride the tandem by myself and test the brakes they are not as strong as on my other bike with margua brakes and only 180 mm rotors. so thats telling me that they are not as strong and its a big difference. so of course with both of us on the tandem they are even weaker. we ride in traffic a lot and being able to do a emergency stop is dicy with these brakes. it improved with the 203 rotors but it is still not great. the rim brake thats on the back my wife can operate seems almost as strong as the disc on back.
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Old 08-06-20, 10:11 AM
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From what I have heard in the MTB world, the knock on Shimano is that they have a variable bite point. I don't know if yours have an adjustment for the bite point or lever travel, but if they do you might check that. If those Shimano brakes will not lock up a wheel on gravel there is something wrong with them. Glazed or contaminated pads or water in the caliper or an air bubble. Check the pads and replace or clean them. Bleed the brakes. They should work better.

I found this review of brakes which dates from 2017 so things may have changed since then, but I doubt that the Hope V4 are any worse.
https://www.vitalmtb.com/features/Vi...DH-Brakes,2152

They found the Hope V4 to be best. Thorn bicycles in the UK tested many disk brakes for fade on an 800 meter hill and they found that the only brake they tested that did not fade was the Hope V4. If you have a lot of money to spend "Trickstuff" makes some ultra powerful brakes but they are out of my price range. Merlin in the UK will sell you a Hope V4 for around $200 US. My memory says the Trickstuff are over double that, and availability is limited. You will also need a much longer hose which is available.

I initially put E4 brakes on our tandem, and they were not up to the job, but they would have locked the rear wheel with ease stopping from 20 mph on a short hill. Where they failed was stopping from 45 MPH on a long hill. But the real thing that I like about the Hope brakes is that I can hold them near the lockup point without locking up. Very good feel. The trickiest length / grade hill I have gone down was marked at 11.1% and it was about 1 km in length, with a cattle guard at the bottom. With all out luggage, the two of us, and the bike, our total weight is very close to 500 pounds.

I have heard that the latest SRAM (Dot fluid) brakes are quite good as well. I prefer to use a DoT fluid brake because I know I can get fluid in remote places where bicycle specific brake fluid may be a few days away.
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Old 08-06-20, 10:13 PM
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after playing with the brakes they work ok but the problem I think are the levers they are two finger levers and to lock the rear wheell on a small slope at 10 mph takes a lot of force. they are fine on flat ground. and suck on steep slopes when you need quick brake action to make it around the corner on that trail. my wife can use her brake but not in emergencies or fast she takes a bit to find it each time. going down long hills I keep it around 20. they have to be e bike compatible and the Magura's have a 4 piston brake that is. that may be the way to go. don't know if I can fit a cooling rotor on the bike.I will have the shop do the work I am not up to that.. I have already put new pads on I sanded the rotors and cleaned them first and broke them in properly .I have some koolstops with a copper back on the way that may work better.

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Old 08-07-20, 12:33 AM
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If your frame has enough clearance, you can fit a 220 mm on the rear. This should give you a bit more capacity.

Also these rotors seem to have very good reviews:
https://shop.brake-stuff.de/en/brake...ano-compatibel
There is also a comparison to a floating rotor on their website incl.the test data and their steel rotor performs better. You can get them in different thickness, and the thicker it gets the more heat capacity the should have.

For a comparison of different brakes this test is a bit newer: https://enduro-mtb.com/en/best-mtb-disc-brake-can-buy/
Mt7 perform extremely well, but the saints are praised for their heat capacity. The saints also have ceramic pistons which should help with the fade, i don't know if the mt7 do.

Let us know what you end up with and how it performs!
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Old 08-07-20, 01:25 AM
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Originally Posted by fooferdoggie View Post
after playing with the brakes they work ok but the problem I think are the levers they are two finger levers and to lock the rear wheell on a small slope at 10 mph takes a lot of force. they are fine on flat ground. and suck on steep slopes when you need quick brake action to make it around the corner on that trail. my wife can use her brake but not in emergencies or fast she takes a bit to find it each time. going down long hills I keep it around 20. they have to be e bike compatible and the Magura's have a 4 piston brake that is. that may be the way to go. don't know if I can fit a cooling rotor on the bike.I will have the shop do the work I am not up to that.. I have already put new pads on I sanded the rotors and cleaned them first and broke them in properly .I have some koolstops with a copper back on the way that may work better.

Yeah, I reckon you are right, that bike is seriously under braked. You want 4 finger levers at a minimum.... Bigger rotor is good as the bigger the rotor the less the clamping force needed. 4 pot is a bit better, even clamping force over a larger pad means less force needed too. You are trying to stop a motorcycle with bicycle brakes!
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Old 08-07-20, 05:48 AM
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we have to use the back more to keep the front wheel from sliding sideways
Forgive me but are there some fundamentals being overlooked here? No doubt at 400lbs I'd be going with vented calipers and rotors, and the largest rotors possible. Braking force is 60/40 f/r so are you underutilizing your rear brake? I'd be purposely locking the rear then backing off slightly to maximize rear effort.
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Old 08-07-20, 08:15 AM
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Originally Posted by Trevtassie View Post
Yeah, I reckon you are right, that bike is seriously under braked. You want 4 finger levers at a minimum.... Bigger rotor is good as the bigger the rotor the less the clamping force needed. 4 pot is a bit better, even clamping force over a larger pad means less force needed too. You are trying to stop a motorcycle with bicycle brakes!
and this bike came with 180 mm rotors.
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Old 08-07-20, 08:16 AM
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Originally Posted by GrainBrain View Post
Forgive me but are there some fundamentals being overlooked here? No doubt at 400lbs I'd be going with vented calipers and rotors, and the largest rotors possible. Braking force is 60/40 f/r so are you underutilizing your rear brake? I'd be purposely locking the rear then backing off slightly to maximize rear effort.
​​​​​
I use it al to but its hard to get the most power out of it with those levers. you have to almost hit the grip to get it to lock and its a lot of effort to squeeze that hard.
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Old 08-15-20, 03:09 PM
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They say a good carpenter never blames his tools. The analogy is very strained, but I read other posts where such and such a product is blamed for having poor performance and in many cases I use the exact same product and get excellent results. It is not possible for 180mm rotors to outperform 203 rotors unless there is a problem with the SETUP of the calipers that are handling the 203mm rotors. In other words, instead of looking to ditch the 'poor performing' calipers, spend more money, lose more riding time while the tandem sits in the shop with a 3 week wait time ... ... get the brakes adjusted? New pads? New pad composition? Maybe different rotors even but 4 piston vs 2 piston as has been said cannot make a night/day difference in results.

I personally don't find it all that shocking that a single bike with 180mm rotors can outbrake a tandem with 203mm rotors in off road riding. I am very biased, I'm sorry, but I don't understand the desire to ride up, or down, grades in double digits of degrees on any other kind of surface but primo grade asphalt! At least if your tastes run to the rough stuff, allow for the fact that environment might be affecting the results? Be safe out there. Maybe the best thing for this team is to learn to work within the limits of their properly adjusted brakes. As noted they have already gone beyond the OEM configuration of 180mm, and IMO 220mm rotors are simply insanity. Don't do it. Walk out the stuff that can't be safely ridden out and call it good.
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Old 08-16-20, 12:01 PM
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Originally Posted by Leisesturm View Post
They say a good carpenter never blames his tools.. . .. I am very biased, I'm sorry, but I don't understand the desire to ride up, or down, grades in double digits of degrees on any other kind of surface but primo grade asphalt! At least if your tastes run to the rough stuff, allow for the fact that environment might be affecting the results? Be safe out there. Maybe the best thing for this team is to learn to work within the limits of their properly adjusted brakes. As noted they have already gone beyond the OEM configuration of 180mm, and IMO 220mm rotors are simply insanity. Don't do it. Walk out the stuff that can't be safely ridden out and call it good.
Good points. All the more so when you remember that this team can get themselves into the technically challenging terrain in the first place only because they are riding what amounts to a motorcycle. If they restricted themselves to terrain that they could manage under their own power, they, and other trail users, would be safer. I cringe at the thought of 400 lb. of muscle and fat hurtling down a path out of control.

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Old 08-16-20, 04:27 PM
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I don't bomb down paths I try to keep it under 10 mph because these are paths in parks in the middle of the city and people are walking. so I keep it slow and sure if I can brake well enough. and second I don't know what you can climb has any relation to going down hill. two different things. my bike is not a motorcycle we have to pedal and the motor cuts out at 20mph often we cruise above that only with our own power. As far as keeping it single digit hills well that would mean we cant even ride home since our road is 10% and all around us there are 13 to 16% roads with bike paths no less like the two pics. we like to keep our speed under control and never go faster the 30 on a straight paved bike path and slower on the road. hell we have al long ride through a cemetery with bike paths that are more then 10% grade.


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Old 08-17-20, 09:35 AM
  #20  
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Originally Posted by Leisesturm View Post
They say a good carpenter never blames his tools.
But the do upgrade them! It sounds like you have verified that your existing brakes are in good working order. I can't see the free stroke adjustment screw in the pictures. It is hiding behind the Master Cylinder piston/reservoir. This link to Shimano describes adjusting the free stroke:
https://bike.shimano.com/en-US/techn...ee-stroke.html

Many "happy" Shimano brake users report that the free stroke adjustment screw does "sod all". If the brakes are in good working order, and they don't have trapped air (rear brakes can be a pain to bleed), and the free stroke is set to have the pads contact the disk almost immediately when you pull on the lever, and they can't stop you from 10 MPH, they may not be up to the task. The brakes on your tandem are not Shimano's downhill Zee or Saint brakes. That would probably be the cheapest place to go. Same brake line, so no need to swap them out. Replace components, bleed, and go.

I certainly don't see anything that suggests overheating on that disk. When my Hope E4 brakes overheated you could see the result on the disk. They were discolored and slightly warped. Your disks don't look like they have been smoking hot. They may just not be up to the task. The English company Thorn has posted their reasons for only specifying Hope V4 brakes for their tandem customers who insist on disk brakes instead of cantilever brakes, but they don't like 700C wheels either.

The Hope V4 on our bike now would have no trouble stopping our bike with a full load on hills like the ones in your pictures. But be warned. My Hope have two finger levers. The Saints have two finger levers. SRAM brakes have two finger levers. I believe that all Downhill MTB brakes made today have two finger levers. If you really feel a need for brake power beyond any rational need, Trickstuff make some extremely high stopping power brakes, but they are above my pay grade and it looks like they make a batch when they have enough orders, so you may be waiting a long while to get them.

I have no experience with Magura brakes, but in my Motocross days their products were highly thought of. Of course, that means I DO bomb down trails that are more than single digits of degrees at high rates of speed, often ones that are not covered in tarmac. Living in Fargo for the last 10 years I really do miss those hills. My old driveway was 16% and gravel. My old cantilever rim brake MTB would stop me on that hill even when I was way too fat. You should be able to stop that tandem.
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Old 08-17-20, 10:12 AM
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Originally Posted by fooferdoggie View Post
... my bike is not a motorcycle we have to pedal and the motor cuts out at 20mph often we cruise above that only with our own power.
With a team weight of more than 400lbs, you're essentially riding a motorcycle with bicycle parts. For comparison purposes, an entry level dirt bike (eg. Honda CRF125) only weighs 200 lbs. Like most motorcycles, its entire braking system is bigger and more powerful than any e-bike or mtn bike. There are simply no mtn bike components designed for riders who weigh more than 250 lbs. In fact, the Fox mtn bike suspension guides maxes out at 250lbs.

If you want to ride an e-tandem, stay roads where the grade is less than 10%. This is the same reason why heavy trucks are prohibited from steep grades. It's just too risky to descent steep trails on a "motorcycle" with bicycle brakes.

PS. Grinding your suspension fork leg (to fit a 203mm rotor) significantly increases the risk of fatigue failure, especially with your team weight.
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Old 08-17-20, 11:54 AM
  #22  
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There is an old joke.

"I went to the doctor and told them, "Doc; it hurts when I do this... The doc says to me, "don't do that."

If that was my doc, I will be looking for a new doc. Why are so many people telling the OP to stick to grades less than 10% when they have made it plain and clear that is not possible? The original Shimano brakes on that bike are marginal. They are Shimano's trail bike brakes and a tandem needs the "downhill" brakes, whether Shimano or otherwise.

In our tours of Scotland I have come to hills with a grade of more than 10%. What should I do? Sorry, can't go on? Walk down the hill? How about Mrs. Dan closes her eyes and we go as fast as we can, because there is a rule of Scottish roads that what goes down will go up! And I need brakes that can stop me at 45 MPH on a steep hill. There may be a cattle guard at the bottom.

Stopping from 10 or 20 MPH with 400 pounds should be possible. Thorn says that they found one disk brake combo that can keep a tandem safe on a 1km 14% average and 25% steepest grade hill. They go on to say this about the Hope V4 with a vented rotor:
With this brake only, we’re able to hold 10mph for almost 800m down Crowcombe Hill, on just the rear brake. I believe that this brake is good enough for us to withdraw our
previous caveat:- that we would not supply a tandem, which only had a disc for a rear brake.
That is a whole lot more than the OP is asking their brakes to do. The photo of their front rotor does not show visible signs of heat damage. I suspect that if they adjust the bite point of their brakes they will be happier, or maybe they need to re-bleed the brakes, but if they are in solid working order and still will not stop that bicycle at 20 MPH or less on a 15% incline, they need to get some brakes intended for downhill MTB riding.

Last edited by DangerousDanR; 08-17-20 at 01:10 PM. Reason: word usage
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Old 08-17-20, 04:38 PM
  #23  
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Originally Posted by mtseymour View Post
With a team weight of more than 400lbs, you're essentially riding a motorcycle with bicycle parts. For comparison purposes, an entry level dirt bike (eg. Honda CRF125) only weighs 200 lbs. Like most motorcycles, its entire braking system is bigger and more powerful than any e-bike or mtn bike. There are simply no mtn bike components designed for riders who weigh more than 250 lbs. In fact, the Fox mtn bike suspension guides maxes out at 250lbs.

If you want to ride an e-tandem, stay roads where the grade is less than 10%. This is the same reason why heavy trucks are prohibited from steep grades. It's just too risky to descent steep trails on a "motorcycle" with bicycle brakes.

PS. Grinding your suspension fork leg (to fit a 203mm rotor) significantly increases the risk of fatigue failure, especially with your team weight.
I did not grind the fork I knocked the corner off of the disc. and we plan on going back to 180's on the front. we can stop ok but I want to sop better so i can go slow down trails. own the road stopping is not a problem but overheating is, the bike can handle 400 pounds so that leaves us with 60 pounds of cargo left. we don't weigh 400 we and the bike and our stuff weigh 400.

Last edited by fooferdoggie; 08-17-20 at 09:33 PM.
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Old 08-17-20, 04:42 PM
  #24  
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Originally Posted by DangerousDanR View Post
Th

If that was my doc, I will be looking for a new doc. Why are so many people telling the OP to stick to grades less than 10% when they have made it plain and clear that is not possible? The original Shimano brakes on that bike are marginal. They are Shimano's trail bike brakes and a tandem needs the "downhill" brakes, whether Shimano or otherwise.

Stopping from 10 or 20 MPH with 400 pounds should be possible. Thorn says that they found one disk brake combo that can keep a tandem safe on a 1km 14% average and 25% steepest grade hill. They go on to say this about the Hope V4 with a vented rotor:
That is a whole lot more than the OP is asking their brakes to do. The photo of their front rotor does not show visible signs of heat damage. I suspect that if they adjust the bite point of their brakes they will be happier, or maybe they need to re-bleed the brakes, but if they are in solid working order and still will not stop that bicycle at 20 MPH or less on a 15% incline, they need to get some brakes intended for downhill MTB riding.
right my regular commuting bikes brakes are better then what the tandem came with. have 203's on the tandem and only 180s on my other bike but I can out stop the tandem with just me on it its a big difference. any decent 4 piston with the cooling rotors should be great. this is Portland and we will be riding in the rain I am sure.
I dont let the brakes to too bad my wife has a rim brake she can use. but that's not practical on trails I cant tell her fast enough to use it and I need more control.

Last edited by fooferdoggie; 08-17-20 at 05:01 PM.
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Old 08-19-20, 03:13 PM
  #25  
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I just realized that we and the o.p. live in the same place. We ride the same roads. Our tandem club rides the same roads. 203mm are the biggest rotors any of the teams in our club (25 teams) have. The Captain of a tandem should have control of all the dynamic braking in my opinion. Of course you can't expect the Stoker to react quick enough to help with staying safe. Without buying new brakes, here is how the o.p. can improve their situation:
Make sure the calipers of the present brakes are properly set up (bled). A single air bubble in the hydraulic line can compromise the effectiveness of the brake. Bike shops are notorious for not being perfectionist enough. I don't trust them with my brakes.
Many tandems come with 'drag brakes'. Some use a 203mm rotor disc brake as a drag brake. That's what you may also have to do. Usually the drag brake is not hydraulic and you can use a friction shifter as the brake lever and apply it only enough to keep your speed from getting out of control and no more. It stays applied continuously all the way down the hill. It doesn't overheat because it isn't really working that hard.

A regular hand lever won't work because your hand will tire or you will sometimes grab harder than necessary and come to a stop when that wasn't intended. A sighted Stoker can see exactly how much or how little drag braking to apply. A blind Stoker cannot. A Captain with a blind Stoker has to have all the controls on their handlebars. You could possibly squeeze the drag brake lever with a rubber band. That's what I would do. Move the rim brake to the right hand lever and move the right hand lever to some other part of the handlebar where you can access it. It now becomes your drag brake. The rim brake becomes your main rear brake.

Or you could just use the two 203mm discs dynamically without any drag brake. Again, properly set up disc calipers gripping 203mm rotors are up to a 400lb. load. Me and mine (me 200, her 150, bike 50, loaded trailer 50 - 100) have no trouble stopping a downhill bomb towards a timed out green light on Cornell Blvd in Hillsboro just past the airport with just the front v-brake on our beat around town tandem when the rear brake wasn't working. When brakes don't stop you, something is wrong with them! There aren't 'better brakes' because the present ones don't work as good. If it's called a brake it better work. Period. I am offering to help sort this out and maybe our Stokers (both blind) can get acquainted. In any case, I hope you figure out how to get more satisfaction out of your tandem adventures. FWIW.
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