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Discussion Starter #1
I have heard on this forum that the brake calipers than come stock on the Cannondale R700 (And others) are junk, that they grab, don't stop well, etc. I have and R700, and admit it does not stop as well as my mountain bike.

But looking at the design of the brake calipers makes me wonder. It appears to be just a pivot. If I replaced them with, say, Ultegra calipers, would I notice a difference? If so, why?

Would just upgrading to Kool stop pads be that noticable?
 

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Island Hopping cyclist
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Upgrading any component will see an increase in performance. Road bikes do take longer to stop then an MTB, but road bikes tend to go faster, requiring longer stopping distances. Upgrading the pads will help a bit, but not as much as a complete brake upgrade.

I also see many negleted brake calipers. About every three or four chain cleanings you need to spray just a little chain lube into the pivot, being careful not to spray the pads.
 

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Those stock calipers look like rebadged Tektros. Your idea about trying Kool Stops is a good one; Tektros are said to work quite well with some better pads.
 

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Brake performance

DieselDan said:
Upgrading any component will see an increase in performance..
Why? Just because a component is higher cost/bling, doesn't gaurantee that it will perform any better than a lower cost component. There are plenty of examples in the bicycle world.

DieselDan said:
Road bikes do take longer to stop then an MTB, but road bikes tend to go faster, requiring longer stopping distances.
Starting from the same speed, virtually all propertly adjusted road brakes will stop faster than MTB brakes. On a road bike, the braking limit is the point at which the rear wheel starts to come off the ground (at around 0.5-0.6g). On clean dry pavement, just about any road brake can reach this point.

On an MTB, depending on surface conditions, the front wheel may start skidding before this limit is reached. Even if MTB traction is perfect, the braking limit is still limited by rear wheel lift-off. The braking force that this is acheived is just about the same as on a road bike.

DieselDan said:
Upgrading the pads will help a bit, but not as much as a complete brake upgrade.
I believe the opposite is the case. Most road brake calipers use a simple single or double pivot design with similar leverage ratio. However, brake pad compositions vary widely. The biggest differences in peformance by road brakes is due to brake pads, not calipers.
 

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you've obviously

never ridden a mtb. all things being equal, the longer leverage arms of a v-brake
will apply more clamping force and stop faster than a road bike.
 

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You've obviously

peabody said:
never ridden a mtb. all things being equal, the longer leverage arms of a v-brake
will apply more clamping force and stop faster than a road bike.
never ridden at the limits of braking.

It doesn't matter what mechanism is used in the caliper - once you've reached the point where the rear wheel starts lifting off the ground, you can not increase deceleration rate (not without flipping over, anyway). I can lift the rear wheel of my road bike off the ground with either single or dual pivot brakes. How can I possibly increase my braking rate? And how can an MTB brake any faster, if it too flips over at the same braking rate?

Furthermore, road tires have more traction on pavement than knobby tires have on dirt. This is plainly obvious because you can't skid a road front tire on clean dry pavement when going in a straight line - the rear wheel will lift off and the bike will flip over first.

Here's a quick test you can do. Jump on your bike and ride a on clean dry pavement. Riding in a straight line at a slow speed (for safety), clamp the front brake as hard as you can. See if you can skid the wheel. See how hard you can pull until the rear wheel lifts off the ground. As soon as the rear wheel starts lifting up, you've past the limits of braking. Extra caliper force or more tire traction won't make a bit of difference at this point - you simply can't stop any faster.
 

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Mark McM said:
However, brake pad compositions vary widely. The biggest differences in peformance by road brakes is due to brake pads, not calipers.
+10. The difference in braking between brakes w/ crap pads and brakes w/ good bads can be enormous.
 

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I have read on other Tektro discussions here that the Tektro's do work a lot better with different pads. I believe people were saying the stock Tektro pads were soft and don't work very well. If it was me I'd start by trying new pads and go from there.
 

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NeoRetroGrouch
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Mark McM said:
never ridden at the limits of braking.

It doesn't matter what mechanism is used in the caliper - once you've reached the point where the rear wheel starts lifting off the ground, you can not increase deceleration rate (not without flipping over, anyway). I can lift the rear wheel of my road bike off the ground with either single or dual pivot brakes. How can I possibly increase my braking rate? And how can an MTB brake any faster, if it too flips over at the same braking rate?

Furthermore, road tires have more traction on pavement than knobby tires have on dirt. This is plainly obvious because you can't skid a road front tire on clean dry pavement when going in a straight line - the rear wheel will lift off and the bike will flip over first.

Here's a quick test you can do. Jump on your bike and ride a on clean dry pavement. Riding in a straight line at a slow speed (for safety), clamp the front brake as hard as you can. See if you can skid the wheel. See how hard you can pull until the rear wheel lifts off the ground. As soon as the rear wheel starts lifting up, you've past the limits of braking. Extra caliper force or more tire traction won't make a bit of difference at this point - you simply can't stop any faster.
You roadies have to learn to move your weight back. With black/salmon combo pads and Ultegra levers and calipers, I can slide back and pull as hard as I can and not slide the front or lift the rear. I just keep moving toward that truck in the intersection. On road bikes with road levers I have tried: cantis, road, BMX mini-Vs, standard Vs with Travel Agents and mechanical discs. For me, they are listed in the order of stopping power (road and mini-Vs are about a tie). - TF
 

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Kant phuckin sphell
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Agree with you guys!

alienator said:
+10. The difference in braking between brakes w/ crap pads and brakes w/ good bads can be enormous.
Those dual pivot calipers ain't too shabby either though......


Try changing the pads too see how you like it, its cheap.
 

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Weight shift minimal

TurboTurtle said:
You roadies have to learn to move your weight back. With black/salmon combo pads and Ultegra levers and calipers, I can slide back and pull as hard as I can and not slide the front or lift the rear.
On a typical road bike, with a typical road posiition, you can only shift your center of gravity back a few inches at best (assuming you keep your hands on the brakes), which can only increase braking at the pitch over power by a few percent. A quick experiment can verify this: Place two bathroom scales on the ground a distance apart equal to your bike's wheelbase. Place one wheel on each scale, mount the bike in your normal riding position, and measure the weight on each wheel. Now, place your hands in a position where the brake levers can be squeezed and shift your weight back, and measure the front and rear weight distribution again. You'll find that increase in weight on the rear wheel is only a few percent.

Of course you can't slide the front wheel - weight shifts to the front wheel during braking, increasing traction, so by the time you've reached the pitch-over point (about 0.5-0.6g) all your weight is on the front and the traction of the front wheel exceeds the braking force.

However, if you can't lift the rear wheel, you are not reaching your maximum braking. Due to a bike's relatively high center of gravity and short wheelbase, a bicycle's braking limit is much lower than an automobile's or a motorcycle's. If you can't even reach the maximum braking limit of the bicycle, then you aren't even approaching how fast an automobile or motorcycle can brake.
 

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Only a small change in your weight will result in a large shortening of your stopping distance. I do agree that to maintain control when breaking you need to make your backwards movements small, but that is all it may take to miss the unthinking not looking truckie.
 

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Juanmoretime
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Mark McM said:
However, if you can't lift the rear wheel, you are not reaching your maximum braking. Due to a bike's relatively high center of gravity and short wheelbase, a bicycle's braking limit is much lower than an automobile's or a motorcycle's. If you can't even reach the maximum braking limit of the bicycle, then you aren't even approaching how fast an automobile or motorcycle can brake.
I'm not sure if I agree with Mark's statement. Under hard braking there is weight transfer and more of the weight does transfer to the front of the bike but it doesn't have to lift the rear wheel to be at the maximum. Once the rear wheel leave contact with the ground you may be at the maximum force on the front but with no rear on the ground adding to the braking it's reduced. Plus isn't maximum braking power the ability to brake at the highest rate and stopping in the shortest distance?

I ride with a center over post, and many feel that this type of post brings your weight distribution forward, and with the distribution of weight on my bike don't lift the rear wheel under braking but I can get it to lock up, I've had the front lock up too. Although once your at that point your beyond your maximum braking poweris gone and your skidding out of control. The rear wheel lift sound more like poor weight distribution to begin with verses an indicator of maximum braking power.

I believe that maximum braking power is the amount of stopping force you can create while maintaining traction without skidding the wheels.
 

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Juanmoretime said:
I'm not sure if I agree with Mark's statement. Under hard braking there is weight transfer and more of the weight does transfer to the front of the bike but it doesn't have to lift the rear wheel to be at the maximum. Once the rear wheel leave contact with the ground you may be at the maximum force on the front but with no rear on the ground adding to the braking it's reduced. Plus isn't maximum braking power the ability to brake at the highest rate and stopping in the shortest distance?
The amount of forward weight shift is proportional to the amount of deceleration, it doesn't matter which wheel is doing the braking. As the deceleration rate increases, at some point all the weight will have shifted to the front wheel, and any increase in deceleration rate will cause the rear wheel to lift and the bike to start to endo. In order to produce braking force at the rear wheel, you must have traction at the rear wheel, which means there must be weight on the rear wheel. And if there is weight on the rear wheel, you are not decelerating as fast as you would if you reached rear wheel lift-off point. If the front brake can produce enough braking force to lift the rear wheel, then that is the maximum braking you can possibly achieve - getting the rear wheel to contribute to the braking would require a slower deceleration rate.

Juanmoretime said:
I ride with a center over post, and many feel that this type of post brings your weight distribution forward, and with the distribution of weight on my bike don't lift the rear wheel under braking but I can get it to lock up, I've had the front lock up too. Although once your at that point your beyond your maximum braking poweris gone and your skidding out of control. The rear wheel lift sound more like poor weight distribution to begin with verses an indicator of maximum braking power..
Getting the rear wheel to skid is easy. Since the harder you brake, the more weight is shifted off the rear wheel, the less traction it has. It only takes a deceleration rate of about 1/4 g to lock up the rear wheel if the rear brake is used alone. The front brake alone can produce far more braking than this. A good front brake can brake hard enough to lift the rear wheel, which occurs at about 1/2 g, or twice the maximum the braking that the rear alone can do.

You say that you have locked up and skidded the front wheel, but I'm sure that you didn't do while going in a straight line on clean dry pavement. In fact it is virtually impossible to skid a front wheel while going straight on clean dry pavement. I've tried many times, and haven't acheived it yet - although I've got the rear wheel off the ground a few times.

Juanmoretime said:
I believe that maximum braking power is the amount of stopping force you can create while maintaining traction without skidding the wheels.
Sure - but by the time you've reached the maximum, there is so little traction at the rear wheel, it can not provide any meaningful braking.
 

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Weight shift and braking distance

slowdave said:
Only a small change in your weight will result in a large shortening of your stopping distance. I do agree that to maintain control when breaking you need to make your backwards movements small, but that is all it may take to miss the unthinking not looking truckie.
How do you propose that the weight shift decreases the stopping distance? The weight shift will not increase how hard the calipers are squeezing the rim. Nor will the weight shift increase traction - the front tire has more than enough traction to brake at the maximum braking rate. The only thing a weight shift can do is change the braking rate at which rear wheel lift-off occurs - and since most riders never reach this point, this has no affect either.
 

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Mark McM said:
How do you propose that the weight shift decreases the stopping distance? The weight shift will not increase how hard the calipers are squeezing the rim. Nor will the weight shift increase traction - the front tire has more than enough traction to brake at the maximum braking rate. The only thing a weight shift can do is change the braking rate at which rear wheel lift-off occurs - and since most riders never reach this point, this has no affect either.
The rear will slide easily as the weight shifts forward. Shifting weight back keeps it from sliding and provides better braking on the rear wheel. - TF
 

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Mark McM said:
On a typical road bike, with a typical road posiition, you can only shift your center of gravity back a few inches at best (assuming you keep your hands on the brakes), which can only increase braking at the pitch over power by a few percent. A quick experiment can verify this: Place two bathroom scales on the ground a distance apart equal to your bike's wheelbase. Place one wheel on each scale, mount the bike in your normal riding position, and measure the weight on each wheel. Now, place your hands in a position where the brake levers can be squeezed and shift your weight back, and measure the front and rear weight distribution again. You'll find that increase in weight on the rear wheel is only a few percent.

Of course you can't slide the front wheel - weight shifts to the front wheel during braking, increasing traction, so by the time you've reached the pitch-over point (about 0.5-0.6g) all your weight is on the front and the traction of the front wheel exceeds the braking force.

However, if you can't lift the rear wheel, you are not reaching your maximum braking. Due to a bike's relatively high center of gravity and short wheelbase, a bicycle's braking limit is much lower than an automobile's or a motorcycle's. If you can't even reach the maximum braking limit of the bicycle, then you aren't even approaching how fast an automobile or motorcycle can brake.
Tried your scale experimrnt. Since I don't have two scales, I just use my trainer and the scale under the front wheel. While holding the brake levers, I can easily decrease the front weight from about 85 lbs to about 45 lbs. This means that 40 more lbs (about 30 % increase) are on the rear resisting lock-up. - TF
 

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Wrong interpretation

TurboTurtle said:
While holding the brake levers, I can easily decrease the front weight from about 85 lbs to about 45 lbs. This means that 40 more lbs (about 30 % increase) are on the rear resisting lock-up. - TF
Not really, because when you are applying the front brake hard, all that weight will shift back to the front. Sliding back increases the front wheel force required to create "rear wheel lift-off" but it does improve rear wheel braking unless you are not applying the front brake hard.
 

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This is fun! For one, I never realised anyone had done "g' ratings on stopping a bike - but it makes sense.

The pad thing has to be reasonable, but my present ride has 'old' Ultegra brakes (circa 2003) with DA shoes, vs my new bike with 'new' Ultegra brakes, pads as they came out the box. Based on some highly scientific testing, my conclusion as to the stopping power on my new bike is somewhere around "[email protected]@7y H#!!, whereas the old gal is merely adequate.

Old age may bring wisdom - when I did this seriously (circa 1970), I didn't know any roadies who ran anything other than the absolutely cheapest sidepulls on the market and the only qualification for the shoes was 'not worn out'.

After all, why spend valuable cash on slowing the bike down? In my case, it was vastly more needed for stuff like tyres, to keep the thing moving!

Now, there's folk willing to spend hundreds on brakes with ti bolts made in one size smaller than last year's edition, to drop another half gram - and, I've read, some of them are so moronic that they'll pay another $50 or so to try and "win" preferential short delivery.

Funny old world, ain't it?

Regards

Dereck
Who should be doing something more important, so will :)
 

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TurboTurtle said:
Tried your scale experimrnt. Since I don't have two scales, I just use my trainer and the scale under the front wheel. While holding the brake levers, I can easily decrease the front weight from about 85 lbs to about 45 lbs. This means that 40 more lbs (about 30 % increase) are on the rear resisting lock-up. - TF
As Kerry says, moving the weight back can either: 1) at any given braking deceleration, increase the maximum possible contribution of the rear brake; or 2) increase the maximum braking deceleration rate by increasing the rear lift-off point. The deceleration rate of option 2 is necessarily greater than option 1, so the maximum possible braking rate is still to be had with front braking only.

Now that you have found the horizontal position of the center of gravity, the next step, albeit more difficult, is to find the height of the center of gravity. The angle of this line (or more specifically the cotangent of this angle) defines the deceleration rate at tire lift off. You can find the height of the c.g. mathematically by raising or lowering one end of the bike and measuring the forward/rearward shift of the c.g. This obviously varies greatly with rider shape and riding position, but my rough guess is that the c.g. will be about 3"-6" above the saddle for a rider on the hoods or drops
 
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