Mini-v brakes, comparison with calipers?
 

I weigh 100kg and ride in the wet often (I like it - I'm strange like that). I use 105 calipers which I've adjusted ad-nauseum. I'm currently trying koolstop salmon pads which don't seem to help a great deal though I shall keep trying.

Currently braking is very poor in the wet - on a good incline in the wet if I exceed 30mph then I literally cannot stop, though I can reign in speed back down to 30mph normally. This is obviously rather dangerous.

I'm thinking of buying some carbon cross forks and trying mini-v brakes. These look like they have rather more mechanical advantage than callipers, but I was wondering if anyone has tried them back to back with callipers (say someone who has cross and road bikes) and how they would say they compare? I used to have a mountain bike and remember the first time I switched from cantis to v-brakes and finding the difference to be very significant - could I expect the same difference here?

The other option is of course to go for discs, but this means messing with my wheels and would cost a lot more.

Mini V brakes are not going to be an upgrade over good dual pivot calipers. V brakes require a Travel Agent or similar device because of longer cable pull to work with road bike levers You can get V brakes that have cable pull caompatible with road levers, but they don't brake as well .

V brakes work better than traditional cantilevers because cantilevers suck

If you're not happy with the 105's, pony up for Dura Ace calipers.

Our tandem, with a team weight of 350lbs stops fine on 20% grades from 65mph with Dura Ace caliper brakes.

I doubt even Dura-Ace calipers will make that much difference. The 105 calipers are pretty good. Are you braking from drops or the hoods? The drops will give you maximum braking power. The newer levers (Shimano x700 series) have been redesigned to have better braking power from the hoods.

If you're still not statisfied, your best option is a new bike. You can get discs and better levers, which is what you'd need to change on your current bike.

I agree with this. Calipers across similar constructed ones, like 105-Ultegra-DuraAce, are virtually identical. I raced for many years using RX-100 calipers (below 105), then for a few years with Ultegra, both while using Campy brake levers. No problems.

Another assumption I think most of us are making is that you're using the front brake. If you only use the rear brake you're not going to stop quickly, even with the best brakes in the world.

Brake pads make a difference. The Kool Stop Salmons are great, relatively speaking, so you're doing that right.

This leaves a few other factors, assuming that you're using both brakes and braking from the drops. Consider what needs to happen to slow down - you need to turn your forward momentum into heat. The heat is generated by the friction between the brake pads and the rim (or disc).

It requires an immense amount of force to generate heat in the rain. I upgraded the brakes on one of former cars to deal with brake fade caused by repeated aggressive slow downs. I didn't realize how efficiently the new brakes dissipated heat - in the rain I had to brake regularly to keep some heat in the rotors, even braking lightly on the uphills. If I didn't then I'd be dealing with a good length pause between hitting the brake pedal and before the brakes started working.

You may have to do this on your bike to keep the rims a bit more dry than soaking wet.

On the drops, with various pads, aluminum rims, on a steep downhill, I'd have a hard time coming to a stop. With carbon I found wet braking to be better, and after learning that carbon retains heat better, that makes sense. The aluminum rims would dissipate the heat quickly whereas the carbon would retain it. You need heat to dry the rim surface so you can generate more heat.

There was a study done on braking. The used a steep downhill, two riders, two bikes, and various techniques. They found that using the front brake allowed them to stop best. This wasn't because of any physics, it was because it was simply too difficult to exert maximum pressure on the front brake while trying to think about the rear brake at the same time. Using both brakes stopped reasonably well. Using only the rear brake didn't work well at all - one of the riders inadvertently ran a stop sign at the bottom of the hill.

The things to do:
- clean your rims. If there's oil, polish, wax, etc, it reduces friction.
- make sure your pads are in okay shape. If they have burn marks or have sand or something embedded in them they're not as effective.

The braking basics:
- use the drops. It gives you more leverage but also more control overall, braking and steering.
- use both brakes or just the front brake (with practice). The rear brake is more like a canary in a coal mine (if you lock up the rear you're starting to maximize your overall braking), the front brake does virtually all of the stopping.

I've tried dura ace, didn't notice much difference in the dry, and I've had quite a few people tell me there's no difference in function (certainly the pivots don't look to be positioned differently so the mechanical advantage can't be too much different). Mini-V brakes can be used with standard pull levers without a travel agent, and I've heard good things on bike review sites but wanted to hear from someone who's gone from calipers to mini-Vs (rather than cantis to mini v as is the norm for cx). From the look of them, there's significantly better leverage.

Interesting, so the x700 series I assume must have greater leverage? Mine are 5501. Wouldn't want to change my bike, am quite attached to it. No interest in changing the back brake, just the front.

I've tried using the drops and the hoods, doesn't seem to make much difference. I've also cleaned the rims thoroughly and both cleaned and resurfaced with sandpaper my old pads before changing to the koolstop salmons. I've also tried with and without cross levers as I ride in the city and find the ability to brake from the upright position very good to have. None of these things has made a significant difference, at least no more than I'd confidently feel wasn't psychosomatic. I brake using both front and back - the back will do very little past a certain level of deceleration as the weight will transfer to the front wheel. Carl Fogarty was quoted as saying he never touched the back brakes on his motogp bike and wouldn't have noticed if a mechanic had removed them before a race.

I think I've pretty much exhausted all that callipers can do. anyone have experience going from callipers to mini v?

We had mini v brakes on a bike friday tandem. I don't recall that bike stopping any better than bikes with calipers.

The reason to use cantilever brakes is that can handle wider tires than typical calipers, and mud clearance. The reason to use V brakes is that cantilevers don't really brake well. The reason to use mini V's is that they don't need travel agents.

But the reason for those brakes is not because calipers don't stop.

Most everybody else is able to stop with decent dual pivot calipers, and good pads.

The x700 series have similar leverage, but the lever shape allows a better pull from the hoods. There's zero difference in braking from the drops.

Have you tried replacing the brake cables? Friction in the cable housing can make a big difference.

I realize you don't want to buy a new bike, but you're pretty much out of options for improved braking. Upgrading to x700 series is basically a totally new groupset (shifters, derailuers, brakes), and I don't know that it would help, and you can buy a new bike for almost as much as the upgrade would cost. New wheels might help if your rims don't have a good braking surface.

If you still don't like the brakes hydraulic discs are absolutely the way to go, but that means a new bike.

Which STI's do you currently have? If you are looking at using x700 series calipers with anything other than the x600, x700 or x800 or 9x00 series STI's you will get less than optimal performance from them. The same goes if looking at mini-v's you need to have the v's that are optimized to the levers for optimal performance, get the correct ones, and Travel Agents aren't needed.

If you are normally riding in the wet, would be looking at discs over calipers, no matter how well calipers are setup, discs will always be superior in the wet in the dry they will be very similar; in addition to improved braking performance, you get the added advantage of no rim wear, which can give a cost saving on replacing rims or wheels.

I have a roubaix with normal brakes (dual pivot caliper) and a Jamis with TRP CX8.4 (Ti). I can't tell the difference between them. As far as I am concerned, the TRP CX8.4 is as good if not better. That's also what other reviewers have said.

Tho' it's a radical change, disc brakes will work much better in wet conditions than rim brakes.

You still have to be careful on descents though. If you drag on the brakes, you run the risk of overheating them and glazing the pads. Especially if you aren't using pads and rotors that are fully compatible and tested.

Thank you for your answer but I am confused - you say you can't tell the difference between them but the TRP is as good if not better. What do you mean?

http://bikeforums.net/attachment.php...hmentid=341717
Just knocked this up. This is why I would expect better pad pressure from the mini v brakes - the leverage does appear to be roughly 20% greater than the calliper.

I have Sora 2003 brifters with BR5501 callipers. I have no issues braking from the hoods as I have very large hands - I don't notice any difference between braking from the drops and the hoods. I was thinking of changing up to microshift arsis at some point and going 10 speed, however the need to upgrade the braking is far more pressing and this will take up the budget so I imagine the Sora brifters will have to stay.

If the mini-vs aren't likely to be any better then a BB7 mechanical road disc would be the next best choice I think. I'd prefer hydraulic but I have no interest in a hybrid hydro/cable system (seems a bit daft) and have heard very good reviews of the BB7s. Problem is budget - I can change to a columbus carbon cx fork and mini V for about £115, whereas changing to the BB7 will cost a total of £260. Quite a difference!

It had occurred to me that SRAM and Shimano are working on hydraulic road brifters at the top end so perhaps hydro brifters and discs will come down to 105 level kit in the next few years as they have done for mtbs? If so, getting by with mini-vs till then and upgrading the groupset would sound a good plan.

Objection to that!
Cantilevers brake fine if you know how to use them.
Then again the fact that you have to master the brakes before there is any use in them is a bit of a bummer.
Mini-V's are easier.

I understand your desire to calculate this with some simple geometry but there are other things at work with any cantilever type brake. The first and foremost is the flex. Cantilevers (Or V-Type) flex the fork outwards (Someone once mentioned that you should put your hands around a canti-fork and squeeze the brakes, you will feel them flex).

Also your diagram should be drawing Y to the location where the brake pad is connected to the pivot arm, your diagram assumes that the braking force will move perfectly perpendicular to the ending of point 'Y' where in reality it moves at an angle.

Long and short is: V Brakes have more flex in them which will change your calculation. Don't underestimate the effect of flex.

Not so, the effect of a lever is calculated by measuring from the point where the force is exerted to the fulcrum. The levers (here the callipers or Vs) will flex a bit but very little and any amount of flex will only change the pressure achieved at the rim if it changes the geometry of the lever or permanently deforms the lever (if you bend something by exerting a force then that thing is also exerting that same force on you unless the force permanently deforms it - this is newton's equal and opposite reaction).

Yes the angle of the force at the rim is not 90 degrees with either brake, but the difference is marginal. I'm very happy that calliper/cantilever flex here can be safely disregarded in the comparison.

This is potentially a factor - fork flex could partially reduce the relative advantage of the V's higher leverage but I think this is very unlikely. As above remember that fork flex itself won't alter the pressure between pad and rim unless it causes the geometry of the lever to change, as however hard you're pushing the fork is exactly how hard the fork is pushing you - again equal and opposite reaction. If the two fulcrum move by more than a few mil then the lever geometry will start to change enough to notice, but then the fork would be going back anyway as it would not be fit for purpose. So there will be flex and this will only affect the V brakes, not the callipers, but I would be very surprised if this affected braking power in any measurable way.

However, flex in any of these components (and most significantly in the cable) will change brake feel and if it flexed enough that you couldn't get full pressure at the brifters without hitting the bar then that'd be a showstopper. Can't see that happening though.

So, I'm happy that the leverage difference is valid. The question is - is it enough to actually make a difference on a wet road? Jury's out on that one.

A: The angle of pad contact does matter, the way you have drawn the end points as the pads means that the force is being directed in a 45 degree angle in the case of the V brake and I am venturing to guess about 20-30 degrees with your caliper brake. Your diagrams actually prove that the force is going to be less well directed in the case of V brake. I am not awake enough to argue about Newtonian Mechanics and Linear Algebra. Please go read this and I will get back to you after that.


B: There is a difference between theoretical and real world applications. Flex is actually a very big part of the equation here. This is merely something that you find out with time and experience. Experimentally things don't exactly work the way they do on paper, sorry but I have spent enough time on both the theoretical side of things and the experimental side of things here to say that flex is certainly a nice big factor you need to deal with when it comes to bikes. For more info read this.


Also, consider the difference between regular cantilever brakes and V brakes . Why is a V-brake so much more powerful? They are essentially the same mechanism and some of them have just as long of a pivot arm, yet they are universally regarded as some of the poorest brakes for road bikes. That is because of a range of factors between flex and leverage.

Perhaps you should try some exalith rims from Mavic and mix them with the new BR-9000 brakes from Shimano, that sounds like some good power there (If not sort of expensive)

Best we simply agree to disagree, as I can't be bothered to explain further. I already have qualifications in pure and mechanics so I'm not going to be buying yet more textbooks! Also, this thread appears to have strayed. I'm looking for people who have experience of using both in the wet.

Mmmmm qualifications, not like I don't have any myself :rolleyes:

Well in any case I can answer your question regardless because I indeed have used both (I have Caliper, Mini-V and regular V with an Adaptor): Stopping power is roughly on par, modulation is pretty poor they have a tendency to be very "On/Off" not all that good for road riding in my opinion. I feel a definite lack of confidence when using a bike with V brakes.

Last week at cross practice I was using the Mini-Vs and I could probably stop well enough even with a few hairy (and grassy) descents. With total power I would say they are equal neither one has given me any problem stopping in a range of conditions. Calipers take a harder squeeze to lock up but that is partially due to the fact that they are designed like that.

One thing you may want to try and actually something different then salmon pads, in my experience using them they have a more 'consistent' braking power in wet and dry but not necessarily 'better'. Try some default black SRAM pads. They give a better lever feel and stiffness in my experience, they will wear your rim a tad faster but I find they total stopping power a little better.

I used to weigh that much. I had no problems with 105 brakes, but if you're really concerned, discs are much better. You can always try mulleting your bike. A good set of disc forks, a caliper and a wheel with a rotor is all you'll need.

Interesting.

Very interesting.

This could be what I want... In the dry, and in the wet at slow speed, I'm happy as larry with wot I got. It's high speed wet descents which have me in danger as I literally cannot stop.

That'll be the leverage difference, same with the on-off feel and lack of modulation.

So the $64 question is this... if you weighed 100kg and were doing 40mph on a 15-20deg descent in the pouring rain with rims covered in the last 20miles worth of road crud and a car pulled out blind in front of you, which of your brakes would you want on the front? Which would be man enough to do the job?

Cute dig at the end there, but I will answer your question regardless:

I would want calipers honestly. My fear in that situation is that the stopping power does not offer the modulation I would want. If you are in a situation like that locking a front wheel will cause a crash much faster than having too much speed. When the roads are wet any brake you have will be able to lock your wheel. The trick is toeing the line on locking your brake. You are probably mis-interpreting the feel of your brakes and feel that they lack power when infact they are just modulating it.

For example on the new SRAM Red calipers (The ones that use Single-pivot style design) have a good bit of initial bite and then through a long part of the throw it feels firm and the power is "good" in that it doesn't cause an instant stop you just get to modulate your power. If you really start to squeeze though the power really ramps up near the end of the throw. I suggest that you take the recommendations we have here and experiment with braking technique.

No dig intended, my apologies.

My current brakes are not capable of locking either wheel, wet or dry, above about 10mph. Modulation is simply not an issue when the only way you can control your speed it to use every ounce of hand strength to haul the levers as tight as you can and end up with aching hands at the end of the ride. At very low speed in the wet I can JUST lock the back wheel. Out of interest, how much do you weigh?

This is where the disconnect is, in both this thread, and your other thread.

It doesn't comport with common experience, that with 105 calipers, and Swiss stop pads, you can't lock up even your back wheel at 10mph in dry conditions.

Something other than the type of brake (caliper) is going on here.

Yup, something ain't right. My dad (engineer and bike nut) is coming down tomorrow to have a look see. After that I've exhausted all options and it's time to choose a replacement... still not sure what to go for but based on dnuzzomueller's experience above I'm thinking mini-V might be a poor option. Maybe I should just pony up for a cx fork and BB7 disk brake...

Yup, something ain't right. My dad (engineer and bike nut) is coming down tomorrow to have a look see. After that I've exhausted all options and it's time to choose a replacement... still not sure what to go for but based on dnuzzomueller's experience above I'm thinking mini-V might be a poor option. Maybe I should just pony up for a cx fork and BB7 disk brake...

And to be clear: Did "exhaust all options" include "taking it to a LBS" ?

Nope. I'd trust my old man over any LBS mechanic any day of the week and twice on Sunday. Only times I've taken stuff in to LBS they've managed to sell me stuff in the process of failing to find a problem, then my dad's managed to fix it.

I have spoken to a couple of LBS about it but got nothing more than suggestions to change the pads or upgrade to dura ace callipers. Not exactly rocket surgery. The new pads have so far not been a great investment and I'm far from convinced that upgrading to dura ace or any other alternative callipers would change much at all.

The arrogance of this post is stifling.

http://sheldonbrown.com/cantilever-geometry.html
http://www.circleacycles.com/cantilevers/

As for the OP's question - I go back and forth from road calipers (Dura Ace 7900 and 105 5700) and Mini-V Brakes on a regular basis since my winter/rain bike has TRP CX9 Mini Vs. The CX9 mini-v absolutely unquestionably have more mechanical advantage than the caliper brakes, as there is always a few stops during the switch where I have to re-learn the amount of force required for a given amount of braking. However, as many have mentioned, the modulation is not as good. In the winter, when it's wet ALWAYS here, that doesn't really matter as the huge drop-off in pad-rim friction means I need more power for a given situation and that reasonably balances the modulation issue.

The main issue in the wet is the near total lack of stopping power (with any rim brake) that you can experience in the first moments of a braking effort. That's a problem for panic/emergency stops. I notice that the braking power ramps up as the rim gets swept dry. I think the most effective way to use rim brakes in the wet is to be proactive about 'wiping' the rims dry - periodically applying light pressure to clear off the rims so they are more ready when you need them.

If you're truly concerned with wet braking performance, you'll never be truly happy until you go to a front disc and caliper, as the real problem with wet braking is always going to be the pad-rim interface.