Rim Vs Disk? Why not Both?

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Huntress_Amelia
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Rim Vs Disk? Why not Both?

Postby Huntress_Amelia » 29 Aug 2016, 10:38am

Whenever I go to bike meets, although this hasn't happened in a couple years, there was always a short debate over rim or disc brakes.

While my experience with disc brakes was short and very bad (cheap bike where the circular disk brake pads fell out whenever they felt like killing me on a steep hill (happened on three occasions, luckily I wasn't injured).

Can a bike have both systems with up to 4 brakes? Two on each wheel?

I thought about this idea while attaching a horn, two light systems, and indicator system, my trailer (which I can't use on my new bike because frame size) and bike bags all that weight adds up, and as the weight goes up the more effort brakes have to do, weight = effort = heat = wear...

Is this a possibility or as I am writing this, wouldn't a larger brake pad be a better option and less effort for upgrading.

reohn2
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Re: Rim Vs Disk? Why not Both?

Postby reohn2 » 29 Aug 2016, 10:58am

Do you really want four brake levers to play with/choose from?

While my experience with disc brakes was short and very bad (cheap bike where the circular disk brake pads fell out whenever they felt like killing me on a steep hill (happened on three occasions, luckily I wasn't injured).

That situation is criminal,the bike should've been returned to the retailer and a refund demanded.

Good quality brakes are a godsend,anything less than that is unacceptable.
I own five bikes with disc brakes two of which are tandems and they stop very well,wet or dry :)
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Bez
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Re: Rim Vs Disk? Why not Both?

Postby Bez » 29 Aug 2016, 11:10am

You wouldn't need four levers, you could do it with two. Hydraulic or cable. A bit of custom brazing and you could have rather more than four brakes, too, if you wanted to be really silly.

Much easier to just get some decent disc brakes, though. By the sounds of it you must have had something which shouldn't even have been on the market.

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meic
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Re: Rim Vs Disk? Why not Both?

Postby meic » 29 Aug 2016, 11:11am

Can a bike have both systems with up to 4 brakes? Two on each wheel?


Yes and with drums instead of disks if you so wish.

The problem is controlling those brakes, you need things like separate levers or cable splitter/balancers and different types of brakes respond in different non-linear ways to the cable pull or tension.
All in all, it generally isnt worth the hassle as most existing single brake systems are adequate enough.

Tandems go down this route, not for outright stopping power but to absorb all the heat generated through continuous braking on long descents.
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Abradable Chin
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Re: Rim Vs Disk? Why not Both?

Postby Abradable Chin » 29 Aug 2016, 11:14am

That's weird. I had this same thought last night.
A bicycle needs two brakes to be road legal, right? And we'd all want two brakes for safety, but why are they always on different wheels?
It is a pain to route a cable to the rear wheel, it's doubly bad on a folder, frictional losses are higher, and rear wheel braking is less effective. Many older frames do not have disc brake tabs, but it is a much easier prospect to swap to a disc-brake compatible fork.

My situation is that I built a rear wheel recently without rim braking surfaces. I now want to use it in a frame without rear disc tab. I either dismantle it, or I could leave the rear wheel unbraked, and double up on the front. Maybe during a front flat or ice rear wheel braking would be helpful, but it doesn't strike me as essential to safety. What do people think? And what do the regulations state?

Huntress_Amelia
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Re: Rim Vs Disk? Why not Both?

Postby Huntress_Amelia » 29 Aug 2016, 11:17am

Bez wrote:Much easier to just get some decent disc brakes, though. By the sounds of it you must have had something which shouldn't even have been on the market.


That is what I said to Halfords at the time, the brakes were shoddy at best, they stopped me quickly, first time I watched my front brake pad roll down the street as a stopped, it fell down a drain before my eyes, I rode home and got it replaced a couple days later.

A couple months later my rear brake did it, on a ride out, I decided to ride it back home again despite the distance and I would just take it slow on the hills, a couple miles from my house on a steep dual carriage way in Sheffield, the front brake rolled out and down the hill... at another time it would have been comedy gold, but I was terrified, luckily the road was almost dead I past a car and managed to go up a crossing ramp and back up a side road. I scrapped the bike I wanted nothing more to do with riding for almost a year I walked to work for 1 hour each way instead.

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Anyway back to the topic at and, would a larger brake pad be more effective?

Huntress_Amelia
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Re: Rim Vs Disk? Why not Both?

Postby Huntress_Amelia » 29 Aug 2016, 11:20am

Abradable Chin wrote:That's weird. I had this same thought last night.
A bicycle needs two brakes to be road legal, right? And we'd all want two brakes for safety, but why are they always on different wheels?
It is a pain to route a cable to the rear wheel, it's doubly bad on a folder, frictional losses are higher, and rear wheel braking is less effective. Many older frames do not have disc brake tabs, but it is a much easier prospect to swap to a disc-brake compatible fork.

My situation is that I built a rear wheel recently without rim braking surfaces. I now want to use it in a frame without rear disc tab. I either dismantle it, or I could leave the rear wheel unbraked, and double up on the front. Maybe during a front flat or ice rear wheel braking would be helpful, but it doesn't strike me as essential to safety. What do people think? And what do the regulations state?


Sorry, according to EU law both the front AND back wheel have to be braked to be legal they are even specific on which side each brake lever has to be on.

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meic
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Re: Rim Vs Disk? Why not Both?

Postby meic » 29 Aug 2016, 11:27am

Abradable Chin wrote:That's weird. I had this same thought last night.
A bicycle needs two brakes to be road legal, right? And we'd all want two brakes for safety, but why are they always on different wheels?
It is a pain to route a cable to the rear wheel, it's doubly bad on a folder, frictional losses are higher, and rear wheel braking is less effective. Many older frames do not have disc brake tabs, but it is a much easier prospect to swap to a disc-brake compatible fork.

My situation is that I built a rear wheel recently without rim braking surfaces. I now want to use it in a frame without rear disc tab. I either dismantle it, or I could leave the rear wheel unbraked, and double up on the front. Maybe during a front flat or ice rear wheel braking would be helpful, but it doesn't strike me as essential to safety. What do people think? And what do the regulations state?


Because that is what the regulations require.

A brief summary here.
http://www.cyclinguk.org/cyclists-libra ... uction-use
Yma o Hyd

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Spinners
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Re: Rim Vs Disk? Why not Both?

Postby Spinners » 29 Aug 2016, 11:28am

Not quite the same but Thorn seem to advocate a disc at the rear and V-Brakes at the front on their Club Tour Mk4 to avoid the overbuilt fork harsh ride syndrome. Just saying.

http://www.sjscycles.com/thornpdf/thorn ... ohires.pdf
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reohn2
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Re: Rim Vs Disk? Why not Both?

Postby reohn2 » 29 Aug 2016, 11:29am

Bez wrote:You wouldn't need four levers, you could do it with two. Hydraulic or cable. A bit of custom brazing and you could have rather more than four brakes, too, if you wanted to be really silly.

On the tandems,we've never needed more than two brakes working from levers and a drag working from a friction lever,and done some pretty big descents with that arrangement.

Much easier to just get some decent disc brakes, though.

Ain't that the truth!
By the sounds of it you must have had something which shouldn't even have been on the market.

More truth :wink:
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reohn2
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Re: Rim Vs Disk? Why not Both?

Postby reohn2 » 29 Aug 2016, 11:33am

Abradable Chin wrote:That's weird. I had this same thought last night.
A bicycle needs two brakes to be road legal, right? And we'd all want two brakes for safety, but why are they always on different wheels?
It is a pain to route a cable to the rear wheel, it's doubly bad on a folder, frictional losses are higher, and rear wheel braking is less effective. Many older frames do not have disc brake tabs, but it is a much easier prospect to swap to a disc-brake compatible fork.

My situation is that I built a rear wheel recently without rim braking surfaces. I now want to use it in a frame without rear disc tab. I either dismantle it, or I could leave the rear wheel unbraked, and double up on the front. Maybe during a front flat or ice rear wheel braking would be helpful, but it doesn't strike me as essential to safety. What do people think? And what do the regulations state?


Two good brakes on the front,dog walks out as is their wont,next stop for the cyclist is the tarmac followed by a trip to the dentist :shock:
Brakes can be too good,as much as they can be bad :wink:
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Stevek76
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Re: Rim Vs Disk? Why not Both?

Postby Stevek76 » 29 Aug 2016, 12:00pm

Huntress_Amelia wrote:
Abradable Chin wrote:That's weird. I had this same thought last night.
A bicycle needs two brakes to be road legal, right?

Sorry, according to EU law both the front AND back wheel have to be braked to be legal they are even specific on which side each brake lever has to be on.


The EU regulation about which side each lever is on is only to do with the state of the bike when sold (also where the bell requirement is from).

When on the road in the UK there are UK laws that cover what state a bike should be in when on the roads. This does require a braking system for each wheel (fixed gear counts for rear) but isn't bothered about where any levers are mounted. It also requires rear red reflector and front and back lights at night. I recall there's also a requirement for the amber pedal ones...

tatanab
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Re: Rim Vs Disk? Why not Both?

Postby tatanab » 29 Aug 2016, 12:14pm

brake 1.jpg
brake 2.jpg
reohn2 wrote:Two good brakes on the front,dog walks out as is their wont,next stop for the cyclist is the tarmac followed by a trip to the dentist :shock: Brakes can be too good,as much as they can be bad :wink:
OK, they are tricycles which frequently have 2 front brakes. No problem with biting the tarmac, but perhaps tricyclists come with ABS :D

I agree that brakes can be too good. My modern touring bike has stiff Shimano dual pivot callipers with top notch after market brake blocks. This has to be treated with care. Contrast it with the flexible centre pulls with rubber blocks that I used 50 years ago.

Abradable Chin
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Re: Rim Vs Disk? Why not Both?

Postby Abradable Chin » 29 Aug 2016, 1:46pm

tatanab wrote:I agree that brakes can be too good

On an conventional bicycle with an effective front brake, the rear brake is just offers redundancy since it has no effect on how rapidly you can stop, so it seems to me that it doesn't really matter on which wheel the redundant brake acts. The redundant rear brake only comes in to play when the front one fails, so I would similarly only use the second redundant brake in the unlikely situation in which the primary one failed. I could even reduce the efficacy of the redundant brake so that I couldn't face plant if I operated them both together. I think Meic has it right that it's what the law says, and there is not necessarily any reason to it.

BTW, I don't think it should be possible on most bikes to flip the bike by braking hard. Perhaps going down a steep incline it is possible. If a rider flies over the handlebars when braking on the horizontal, it is because he didn't have sufficient tone in his arm muscles at the time. This sometimes happens when taken by surprise.

Brucey
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Re: Rim Vs Disk? Why not Both?

Postby Brucey » 29 Aug 2016, 1:59pm

Abradable Chin wrote:
tatanab wrote:I agree that brakes can be too good

On an conventional bicycle with an effective front brake, the rear brake is just offers redundancy since it has no effect on how rapidly you can stop....


whenever there is some weight on the rear wheel, the rear brake can help to slow you down. Yes, you will stop most quickly if you can operate to the front brake to the exact point at which the rear wheel is starting to lift (and no more) but very few people can (or will) do that.

BTW, I don't think it should be possible on most bikes to flip the bike by braking hard...


nope, not so. There are a few bikes out there (tandems, bikes with a heavy rear load) where the front wheel will skid when you brake hard, and things may be different in the wet too, but the rest (in toto nearly all) of them will lift the rear wheel if you brake hard enough.

Hard braking in an emergency is a near-reflex action that does not involve conscious thought past 'brake hard, now'. If you are used to a given type of brake, changing to much more powerful ones can be very dangerous if you should then have to do an emergency stop. I've seen several people chuck themselves over the handlebars this way.

cheers
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