Twin discs up front?

Woe unto you that bought the first model year of a major remake, perhaps this section can help address any 2014 and later model Ural "imperfections". Here's a special section for folks with the latest rigs to discuss 2014 and later model-related topics such fuel injection, 3-wheel disc brakes, hydraulic steering dampers, spin-on oil filters and other anomalies that don't belong on true Russsian motorcycle ;-P We've gone from using big hammers and greasy wrenches to needing computers and Ouija boards in order to fix our rigs.
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Please keep this section specific to issues pertaining to 2014 and later models such as fuel injection, sidecar and rear disc brakes and so forth. Ask general or non-2014 and later specific questions in the main Hammerin' & Wrenchin' section.
Fran
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Twin discs up front?

Post by Fran » Thu Feb 07, 2019 11:11 am

The mountains here in Guatemala are very steep and too much for the front brake. I am wondering has anyone thought about adding a second disc up front? With just a casual look it seems it would work. There seems to be enough room and with a mounting bracket fabricated and a splitter on the line and a disc on the hub it seems reasonably simple to me. Any thoughts out there?

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Peter Pan
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Re: Twin discs up front?

Post by Peter Pan » Thu Feb 07, 2019 12:05 pm

Possible without doubt. Guatemala should be much less hilly then Costa Rica. I still run drum brakes in the back and the single disc front brake I am able to block in any situation. I would worry more about the other 2 brakes to fade. (by the way I recommend you to change to synthetic brake liquid.)
Compression is the trick. Better have the engine reving at max revs, then rely only on brakes.

For the very bad climbs be sure to stay between 4000-5500 revs. Below 3300 revs the oil is not spashing enough and the engine tends to overheat. Check oil daily and on long Cordillera climbs for safety recheck as our Sophie uses sometimes on such climbs up to 0,6 liter oil in 100km. I use to keep the oil level at 1/2 to 3/4 of the dipstick mark when cold. You will be amazed how much the oil expands when it becomes hot. 10mm difference on the dipstick happens more then once. I broke one Honda CB125 engine once due to overfilling, so stay inside the oil marks. Good tool for such a case and filling the final drive is a turkey/meet "salmuera" shringe.

Important, when you have over loaded busses, trucks or Sunday drivers blocking your free ride and obligate you to too low speeds. Better stop, wait until the next cue comes uphill and go in front of them speeding at the Ural speed until you catch the tail of the upper cue again. If not and you stay inside a Sunday driver cue an engine seize will come for sure.

In case engine seizes, just stop, wait half an hour or more and kick through some times without ignition until the engine gets to normal friction and temperature. The critical oil temperature had been visibly above 113ºC= 235ºF when seizings occured. (Don't throw water on a standing or running engine!!!! => But you might think about a hand sprayer and your copilot can spray some water mist in front of the engine while you ride. A trick which worked on the Jawa rig. Until a Sunday driver caused the exitus on a Cordillera climb, where was no change to stop and wait at all for several km.)
Good luck on your journey.
Sven


Idea: If you get a disc, ball heads and brake fist with all plumbing, we could crank out a left hand brake monting in my machine shop when you come by and I am still in CR.
Sophie Travelair = Patrol 2013 =>43.388km+nacked :shock: :pot:
8 weeks 12.000km Oregon-Alaska-Oregon
With a DIY foam air filter the rig runs well even in tropical rain = :moto:
Final drives: 1. at 5000km, 2. at 34.000km(+friction plates) 3. at 42.386km
transmission: 1. 40.000km. 2. installed
Engine: 1.43.388km :gahhh:

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Claus
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Re: Twin discs up front?

Post by Claus » Thu Feb 07, 2019 12:28 pm

If you run a second brake in the front it´s becoming so strong that it will block your front wheel too easy. Without a good brake on the side car wheel the sidecar will push your blocked front wheel into the oncoming traffic.
Rather than fitting a second brake to the front wheel I would recommend to repair or maintain the brakes on sidecar and rear wheel so they will work properly.
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

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Re: Twin discs up front?

Post by Peter Pan » Thu Feb 07, 2019 12:42 pm

As Claus says!!!
Sophie Travelair = Patrol 2013 =>43.388km+nacked :shock: :pot:
8 weeks 12.000km Oregon-Alaska-Oregon
With a DIY foam air filter the rig runs well even in tropical rain = :moto:
Final drives: 1. at 5000km, 2. at 34.000km(+friction plates) 3. at 42.386km
transmission: 1. 40.000km. 2. installed
Engine: 1.43.388km :gahhh:

The Avatar are 2 rice grains stating life's essence:
"The most important you cannot see!"
=> Attitude makes the difference!

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Re: Twin discs up front?

Post by Snakeoil » Thu Feb 07, 2019 8:02 pm

I would not put DOT 5 in place of DOT 3 or 4 if that is what you are suggesting.
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rivers
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Re: Twin discs up front?

Post by rivers » Fri Feb 08, 2019 12:45 pm

Snakeoil wrote:
Thu Feb 07, 2019 8:02 pm
I would not put DOT 5 in place of DOT 3 or 4 if that is what you are suggesting.
+1
Use only what your owners manual recommends. Dot 5(synthetic) fluid is not compatible with Dot 4 rubber bits and bad juju happens. As mentioned previously use your eng/trans for long downhill stretches. Don't ride the brakes. Single/dual/discs/drums are all going to overheat if ridden for any length of time.
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Re: Twin discs up front?

Post by Peter Pan » Fri Feb 08, 2019 1:02 pm

I have to check what say bottle and brake tank, I am sure they coincidate.
Me too for synthetic liquids I am a burnt child, but on brake fluid in tropic climate I am a BIG fan of synthetic fluid...once you grabbed into a over boiled brake you know about what I speek. had it perhaps 4-5 times and not again after changing liquid type. Just have a bad memory for brand names (unless some save the day specials)
Sophie Travelair = Patrol 2013 =>43.388km+nacked :shock: :pot:
8 weeks 12.000km Oregon-Alaska-Oregon
With a DIY foam air filter the rig runs well even in tropical rain = :moto:
Final drives: 1. at 5000km, 2. at 34.000km(+friction plates) 3. at 42.386km
transmission: 1. 40.000km. 2. installed
Engine: 1.43.388km :gahhh:

The Avatar are 2 rice grains stating life's essence:
"The most important you cannot see!"
=> Attitude makes the difference!

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Re: Twin discs up front?

Post by Mr Wazzock » Fri Feb 08, 2019 4:21 pm

rivers wrote:
Fri Feb 08, 2019 12:45 pm
Snakeoil wrote:
Thu Feb 07, 2019 8:02 pm
I would not put DOT 5 in place of DOT 3 or 4 if that is what you are suggesting.
+1
Use only what your owners manual recommends. Dot 5(synthetic) fluid is not compatible with Dot 4 rubber bits and bad juju happens.
Image this

However we have access to DOT 5.1, which is back to glycol based.

Re second disc idea, I'm not sure either, the stock disc is big plus 4-piston caliper, so the pads are large (well larger than what I had on my old Moto Guzzis and BMW, about twice as big, so they needed twin discs to be comparable [which they did have]). I think more braking force will just mean locking the wheel more easily. I've managed to lock mine on pavement. Add water or dirt to the surface, it's a cert.

Just IMHO...
Mike H
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(aka Oranzhevaya Opasnost, "The Orange Peril")

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Re: Twin discs up front?

Post by chaos2 » Fri Feb 08, 2019 4:41 pm

twin discs might be less prone to fade from overheating on long downhill stretches, but I'd try just keeping the stock brakes in top condition first.
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Re: Twin discs up front?

Post by Manscout » Fri Feb 08, 2019 5:59 pm

Fran wrote:
Thu Feb 07, 2019 11:11 am
The mountains here in Guatemala are very steep and too much for the front brake. I am wondering has anyone thought about adding a second disc up front? With just a casual look it seems it would work. There seems to be enough room and with a mounting bracket fabricated and a splitter on the line and a disc on the hub it seems reasonably simple to me. Any thoughts out there?
Just like when you drove truck ( I think I am getting it right), engine compression braking is your best friend for steep grades. Start in 1st, and then pulse brake, only 3 seconds on the brakes to lower your speed 5mph. Once it speeds back up 5mph, brake 3 seconds on. Repeat! You'll still get some fade, but you shouldn't loose it all together.
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Claus
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Re: Twin discs up front?

Post by Claus » Sat Feb 09, 2019 7:25 am

Manscout wrote:
Fri Feb 08, 2019 5:59 pm
Just like when you drove truck ( I think I am getting it right), engine compression braking is your best friend for steep grades. Start in 1st, and then pulse brake, only 3 seconds on the brakes to lower your speed 5mph. Once it speeds back up 5mph, brake 3 seconds on. Repeat! You'll still get some fade, but you shouldn't loose it all together.
+1

I used to work as a truck driver for some years when there was no retarders and other modern stuff on a 40 ton truck. What I learnt back in the day is to take the same gear downhill that you would choose uphill and use the brake like Manscout wrote.
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

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Re: Twin discs up front?

Post by Fran » Sat Feb 09, 2019 4:23 pm

Thanks for all the replies. The situation here is we have encountered two 9%+ grades of over 10k in length with multiple switchbacks. I already do safe breaking and engine breaking and stop regularly to let the brakes cool. Between myself, Yvonne and all the gear add another 450lbs to the bike weight. My point is that there is no margin for error with only a single disc. Claus it not the amount of brakes you have it is how you apply them. My thinking is with twin discs the heat in each disc is halved as it is doing half the work. Your margin of safety is increased. This idea is for extreme grades only like we have encountered here. Any more ideas are greatly accepted.

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Re: Twin discs up front?

Post by mrmagoo » Sun Feb 10, 2019 3:17 pm

What speed are you descending? slow? Maybe run some sort of fan to reduce rotor temps?

Dual rotors would be a better solution but more expensive. Im not so sure they would lock up that much easier. Disclaimer: i dont yet own a ural and dont know the system. Neither am i an expert in hydraulics. With that said: Your not increasing the hydraulic advantage (piston diameter/stroke ratios that determine force). I would think the increase in friction surface would at least be partially offset the fact your splitting the same force applied over two sets of brakes. And ultimately splitting the heat buildup over two rotors.

I would make sure your running DOT 4 over Dot 3 (higher temp range iirc).

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Re: Twin discs up front?

Post by Claus » Sun Feb 10, 2019 8:35 pm

I build rigs since 15 Years and know about the customers' wish for better brakes.
Having more than one disc brake is very good. But the second disk brake should be on the sidecar, activated together with the front brake.
If there is more need than that for a better brake after that modification, add a second disc to the front wheel or one to the rear wheel.

I experienced being pushed into the oncoming traffic more than once and many customers did. Once a sidecar wheel is equipped with a disc brake, your rig keeps in lane, even when your front wheel is blocked. That makes a big difference to me.

It's your decision, Fran. The front caliper of modern urals is the Brembo 30/34mm left front Caliper from Moto Guzzi (around 2000 with fuel injection)
The front right caliper should match and you`ll need only a caliper holder ,a bit of welding , turning and milling, a disc rotor with adapter and a bigger master cylinder (15 mm), a brake line, a torque bar and the ball joints. Take a look on the lower mount of the caliper holder, where the axle goes through. If you make a new holder, it must be the same type of construction (the caliper must be able to rotate around the axle)
owned bikes: 93 Ural rig domestic model, 01 Ural 750 rig, 92 BMW R100GS, 92 Suzuki GSX1100G rig, 95 BMW R100R rig with Ural sidecar, 98 Ural rig with BMW drivetrain under construction

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Re: Twin discs up front?

Post by Lmo » Mon Feb 11, 2019 2:50 pm

The master cylinder capacity might be insufficient for two front calipers... no?
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