A newb question

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A newb question

Postby Shaolin_stud » Thu Oct 15, 2009 3:46 pm

Earlier today I was out on a training ride and I came across a question rather accidently.

I had just finished climbing (in my opinion) a pretty big hill. Upon reaching the top I ofcourse decided to go down it:P...

The point to this is ofcourse, How good are road bike breaks when speeds start to exceed 60km/h?

I ask this question because I intend to eventually upgrade my Mountain Bike for a road bike and seeings as i have hydraulic disck breaks im just worried the breaks on the road bike wont match the breaks I have now.

I know this may seem stupid to ask, but Im wondering what a proper road bike is like as I see a fair few guys on them around my area but cant usually catch up to talk to them

Thanks in advance for ignoring my stupidity :D
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by BNA » Thu Oct 15, 2009 4:11 pm

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Re: A newb question

Postby USM TOM » Thu Oct 15, 2009 4:11 pm

Shaolin_stud wrote:s i have hydraulic disck breaks im just worried the breaks on the road bike wont match the breaks I have now.
D


they wont come close to your MTB brakes
road bike brakes are pretty crap IMO
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Re: A newb question

Postby m@ » Thu Oct 15, 2009 4:20 pm

If they can lock the rear wheel, they're stronger than they need to be... If they can't lock the rear wheel, either there's something wrong with your setup and/or you've bought Tektro calipers that are made from cheese :lol:

You won't necessarily stop as fast as you would on a mountain bike, but my understanding is that all other things being equal, that's due to the difference in tyre pressure and contact patch size; not the brakes per se.
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Re: A newb question

Postby didge » Thu Oct 15, 2009 5:15 pm

Shaolin_stud wrote:How good are road bike breaks when speeds start to exceed 60km/h?


If you're above 60km/hr and your road bike breaks you are in big trouble.

Sorry
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Re: A newb question

Postby Jonny Rochester » Thu Oct 15, 2009 6:30 pm

^^ very true.


If you have modern Shimano Sora or Tiagra brakes, they will work very well. I noticed the Shimano 105 brakes do work a bit better.

The tyres are narrow, so it won't be hard to lock up the back. I read that Lance Armstrong got up to 110km/h in one of the tours recently. Their brakes are not so different to what you could afford on a modern road bike.
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Re: A newb question

Postby Shaolin_stud » Fri Oct 16, 2009 7:51 am

WOW! 110 km/h?????? THATS INSANE!!!!

but yeah i really thought that the breaks of a road bike would just be in scale with the rest of the system, why need such hardcore breaks if the over all bike is lighter? but i see what your all saying.I spoke to my Gfs dad last night whos an ex racer and he pretty much said the same thing. In fact hes words were something like "above 80km/h those breaks arent good for nothing, they just slow you down anyway", so im thinking I might stick with the mountain bike for a while yet before my skills improve:P

THanks for all the helpful answers :D
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Re: A newb question

Postby JV911 » Fri Oct 16, 2009 8:51 am

m@ wrote:If they can lock the rear wheel, they're stronger than they need to be...


or you just have crap tyres with inadequate grip. stickier tyres will enable you to brake harder
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Re: A newb question

Postby philip » Fri Oct 16, 2009 9:23 am

JV911 wrote:or you just have crap tyres with inadequate grip. stickier tyres will enable you to brake harder


+1, you have to remember the force slowing you down is between your tyres and the road, not the brakes and the rims.
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Re: A newb question

Postby m@ » Fri Oct 16, 2009 9:30 am

JV911 wrote:
m@ wrote:If they can lock the rear wheel, they're stronger than they need to be...


or you just have crap tyres with inadequate grip. stickier tyres will enable you to brake harder


True... though even with grippy tyres, modern road calipers should be able to lock the wheels... The point I was trying to make is that if you can lock the wheels, stronger brakes won't stop you any faster.
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Re: A newb question

Postby DanielS » Sat Oct 17, 2009 5:56 pm

Clean rims + Koolstop salmon pads + decent calipers = pretty damn good brakes actually!
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Re: A newb question

Postby toolonglegs » Sat Oct 17, 2009 10:12 pm

In the dry all your braking is on the front wheel...yes you can lock your rear wheel up because it has hardly any weight on it when braking hard.Road bike brakes are pretty good... their problem is they over heat very quickly...you just need to learn their limitations...especially in the wet!.
My brakes work harder than LA's most days of the week anyway...I can go faster down hills cause I weigh a lot more and when I need to stop I have 30-40 kilos more to slow down :lol: .
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Re: A newb question

Postby JV911 » Mon Oct 19, 2009 2:15 pm

m@ wrote:True... though even with grippy tyres, modern road calipers should be able to lock the wheels...


you really dont want to lock the wheel as if you're skidding you're not slowing down plus you'll loose the ability to steer if the front locks - hence ABS for cars

had a moment on a bunch ride last week...i was sitting 3rd wheel and as we approached a roundabout "clear" was called and a moment later the call was "CAR!" so i jumped on the brakes to avoid ploughing into the bloke in front. the wheels didnt lock but the rear tyre was a good 30cm off the deck :shock:
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Re: A newb question

Postby m@ » Mon Oct 19, 2009 2:27 pm

JV911 wrote:
m@ wrote:True... though even with grippy tyres, modern road calipers should be able to lock the wheels...


you really dont want to lock the wheel as if you're skidding you're not slowing down plus you'll loose the ability to steer if the front locks - hence ABS for cars


Exactly my point - the brakes themselves are more powerful than they need to be for optimal deceleration...
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Re: A newb question

Postby lukas » Mon Oct 19, 2009 2:29 pm

DanielS wrote:Clean rims + Koolstop salmon pads + decent calipers = pretty damn good brakes actually!


I bought the koolstop salmon's for the DA brakes on my R3. I've got to say I'm a little bit disappointed. They just feel way too mushy for me. I'm going to try the Swisstops.
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Re: A newb question

Postby steambao » Wed Oct 28, 2009 1:03 pm

Don't forget your HIGH SCHOOL PHYSICS.

What's the fastest and safest way to stop? Pump the brakes!! Your stopping distance will be the shortest if you pump (Press, release, roll, press, release, roll) because its the rolling resistance that slows you down the most. That's what you get in a Car with assisted braking :D

That way you can never flip over your bars too.
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Re: A newb question

Postby toolonglegs » Wed Oct 28, 2009 5:41 pm

steambao wrote:Don't forget your HIGH SCHOOL PHYSICS.

What's the fastest and safest way to stop? Pump the brakes!! Your stopping distance will be the shortest if you pump (Press, release, roll, press, release, roll) because its the rolling resistance that slows you down the most. That's what you get in a Car with assisted braking :D

That way you can never flip over your bars too.



Are you sure!...ABS (in a car)braking only pulsates if you are about to lock up the wheel.It does not pulsate under a smaller load.
Your stopping distance will be shortest if you get your weight back as much as possible (to have more weight over the back wheel) and hold your brakes on as hard as possible with out locking the rear wheel or the front for that matter.
It is the friction between the brake pads and rim that slows you down....NOT the rolling resistance.
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Re: A newb question

Postby thommo09 » Thu Oct 29, 2009 9:18 am

steambao wrote:Don't forget your HIGH SCHOOL PHYSICS.

What's the fastest and safest way to stop? Pump the brakes!! Your stopping distance will be the shortest if you pump (Press, release, roll, press, release, roll) because its the rolling resistance that slows you down the most. That's what you get in a Car with assisted braking :D

That way you can never flip over your bars too.


Sounds like you might be confusing the idea of "setting-up" your brakes (ie. taking up slack in cables/hydraulics) with anti-lock systems. ABS is designed solely to stop locking up and maintains traction between the tyre(s) and the road, something that usually occurs when the driver slams their foot on the brakes fast and hard. ABS will stop you faster than skidding to a halt, but much slower than if you set-up, then apply the brakes smoothly but firmly. You'll always stop faster if you use a smooth action and set up correctly before braking. Of course this is just stuff I've learnt from riding a motorbike, but most of it has transfered over to riding a pushie so far :D
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Re: A newb question

Postby JV911 » Thu Oct 29, 2009 10:57 am

thommo09 wrote:
steambao wrote:You'll always stop faster if you use a smooth action and set up correctly before braking.


+1 smooth action required. if you grab a big handful of brakes you'll lock up

toolonglegs wrote:Are you sure!...ABS (in a car)braking only pulsates if you are about to lock up the wheel.It does not pulsate under a smaller load.


+1
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Re: A newb question

Postby drubie » Thu Oct 29, 2009 1:55 pm

It's a pretty common misconception about ABS - that it "helps" your braking when in fact it's there to help you to *steer* while you're braking. When the wheel slips, it can no longer steer the car, so a skid just makes you a passenger. Not that a heavily braked car wheel is much good for steering anyway, but every little bit helps.

I'm not sure what "pumping" the brakes on a road bike would do, other than maybe for clearing a bit of water off the rims in the rain?
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Re: A newb question

Postby steambao » Thu Oct 29, 2009 2:04 pm

toolonglegs wrote:
steambao wrote:Don't forget your HIGH SCHOOL PHYSICS.

What's the fastest and safest way to stop? Pump the brakes!! Your stopping distance will be the shortest if you pump (Press, release, roll, press, release, roll) because its the rolling resistance that slows you down the most. That's what you get in a Car with assisted braking :D

That way you can never flip over your bars too.



Are you sure!...ABS (in a car)braking only pulsates if you are about to lock up the wheel.It does not pulsate under a smaller load.
Your stopping distance will be shortest if you get your weight back as much as possible (to have more weight over the back wheel) and hold your brakes on as hard as possible with out locking the rear wheel or the front for that matter.
It is the friction between the brake pads and rim that slows you down....NOT the rolling resistance.


Yes, ABS only kicks in when your about to lock the wheel (on cars) because no one wants a rough ride. The idea behind stopping is through friction - friction between the road and your tyre (not the wheel and brake pad). The wheel and brake pad is just the means to the end. A break works, in the case of a bicycle, through the pads converting kinetic energy to heat, consequently slowing the wheel down. But it is the friction between the Wheel and the Ground that causes a bike to stop. A rotating wheel stops faster then a skiding wheel [static friction vs. dynamic friction]

When you pulse your brakes, your wheel will slow, roll, slow roll. When you are rolling does the wheel slow down the most. This also applies to smooth action. When you apply v-brakes, you gently hold it. You a slowing down because the wheel is still rolling! It's like pulsating your brakes but at micro-intervals.

The fact of the matter is, in a emergency situation when you're going really fast, gently pressing down on your brakes will not cause you to stop in time and so the best way to prevent skipping/skidding and stopping in time is through pulses. This allows for more force and prevents locking because letting your tyre roll will ensure some co-efficient of dynamic/static friction will not exceeed the other (i forgot which way) and hence you won't skid.
Last edited by steambao on Thu Oct 29, 2009 2:11 pm, edited 1 time in total.
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Re: A newb question

Postby sogood » Thu Oct 29, 2009 2:10 pm

ABS helps to preserve grip of the tyre on the road and prevent the tyre/road from exceeding their limit ie. F(static friction). Once exceeded in a skid, the max F(dynamic friction) is a lot lower. Hence the longer stopping distance in a skid.

As for pulsing the brakes on a long descent. My understanding is that it helps to keep the rims cooler, thereby minimises the risk of blow out and loss of braking power at higher temps.
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Re: A newb question

Postby twizzle » Thu Oct 29, 2009 3:48 pm

V-Brakes + lots of weight = O.K. Road brakes + lots of weight = big-time 'Oh, Feck!'. On a 12-14% grade, I can't stop the bike.

(As an aside... the hill I can't stop on has claimed the lives of two cyclists that I know of - one roadie who went head on into a 4WD when he drifted across the road, and one recumbent who went under a crash barrier).
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Re: A newb question

Postby toolonglegs » Sat Oct 31, 2009 7:22 pm

Oh well we will have to agree to disagree on that one... :D .
I often ride very fast tricky descents and there is no way I will be pumping my brakes before a corner...I am about a big handful on the entry and then chucking it into the apex...whether that is feet level knees tight on the top tube or outside leg down inside knee out depends on road surface and corner.
Exactly the same as when I was racing motor bikes...your hand cannot pump a brake the same as an ABS system....personally and many agree that ABS on motorbikes is actually more dangerous than a sliding wheel...but then I was big fan of the Kenny Roberts school of racing.
I don't even like ABS on my car!...well except in the middle of winter...but then it is of no help on black ice anyway.
Not many people can hold my wheel on a descent so I must be doing OK :lol: .
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Re: A newb question

Postby Kalgrm » Sat Oct 31, 2009 7:32 pm

toolonglegs wrote:Oh well we will have to agree to disagree on that one... :D

I'm with you on this one TLL. Under steambao's theory, we'd never be able to coast on our bikes.

Steambao, the wheel only slows significantly when the brakes are applied. If you release the brakes, the only thing slowing you is rolling and wind resistance, which is there whether you've got the brakes applied or not.

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Re: A newb question

Postby damhooligan » Sat Oct 31, 2009 7:39 pm

DanielS wrote:Clean rims + Koolstop salmon pads + decent calipers = pretty damn good brakes actually!


Agreed, went downhill today and reached 60km/h, only to dicover that the lights at the bottom wher going to be red....
Slowed down very quikly, no worries. :twisted:
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