MTB V Brakes or rims?

[Wakatuki]

Hi,
Double header this one. My refurbed MTB is no longer pulling me up. I live in a particularly hilly area, bit country and all that
Now when I first fitted MTB generic $12 V brake pads and adjusted it all up it was ok the rear wheel would lock up if need be. I recently rode down a damp hill at around 40-50kph, a road I know quite well; applied the brakes but I struggled to slow down. I ended up with a brake lever to bar moment, whilst pulsing the front brake.

When I had stopped I checked the brakes and found them fine in location from the rim. So thought the problem may be cable stretch, wound in two turn pads were almost rubbing, I still had quite a descent to go. Onto the loose stuff onto a section nicknamed 'pucker up' a loose road section and again the rear would not lock up, not willing to reach hard for the front brake I hung on for grim death and got 4th place on Strava, I weigh 99kg, so I descend quickly everywhere.. Not always by choice!

Now, the LBS say rims need a 'rim stone treatment' WTH is that? I was just going to buy some Kool Stop Salmon pads. Which way would you go....?
MTB has about 3000k's on it and was formally panniered up and toured the east of AU by the former owner. It had little to no pads on it when purchased. New pads have covered about 80k’s.

Also the roadie, 300k's on the Foil, noisy grating brakes on the front, always has. LBS where I purchased from says no problems when serviced 2 weeks ago. Again, the brakes were not very good at biting this morning, not raining but the roads were wet enough to make the tires shine and occasionally spray up.

Could it be the roads around me are greasy/grimy; do I need to up the maintenance/ cleaning?

Any thoughts or suggestions....

Thanks

[drubie]

A v brake where the lever goes to the bar should just need adjusting. Double check the cable outers and where the cables transition from sheathed to bare to ensure there is no springiness on badly cut cable outers.

Noisy roadie brakes are normally alloy chips in the pads. Clean or replace the pads.

[silentbutdeadly]

If the only thing you've done to the MTB brakes is replace the pads...then I'd go with replacing the cable outer and inner and try the Kool Stop pads (I'm a fan). I've used the Jagwire cable sets and found them to be very useful at improving brakes over the generic but using Shimano XT outers and generic inner cable was just as effective.

It is worth looking for a wear indicator on the MTB rims...the previous owner may have worn the rim down that far with the touring etc. though it should be fine after just 3000kms. If it is glazed then try a gentle wipe over the braking surface with moistened 400 grit wet & dry...or a moistened green scouring pad

[human909]

not willing to reach hard for the front brake I hung on for grim death and got 4th place on Strava

That is your main problem. Your front brake should be doing 90-100% of the work. If you aren't using it properly then you can never expect good braking performance. Personally I ONLY use the front brake when on tarmac.

Rear brakes as well as being fundamentalled limited in braking capacity are also often further limitted due to cable flex, housing compression, and seat stay flex. All of these factors may combine to give you a lever to handle situation.

Stop relying on the rear brake!

[sturmey archer]

Regardless of braking technique, you should be easily able to lock up the rear brake going down hill. I'd :
Clean the rim surface with metho to remove any oil that might be there.
Sandpaper the brake blocks to remove any contaminated surface. If the blocks are old and hard they may be useless anyway.
Check the cables move freely and there are no kinks in the cable. Under tension any friction in the cables will be magnified. You want all that squeeze at the bars to go to squeezing the brakepads, not overcoming friction in the cable.
See whats bending when you pull the lever back to the bars. In a perfect world the only thing that will give is the rubber brake pads. In the real world the cable outer may compress, the arms of the v brakes will bend and the forks /stays will bend apart as you yank on the brakes.

Grating brakes? I'd check for bits of rim/grit embedded in the pads. For me salmon koolstops seem to hold much less stuff and worked better in the wet that the OEM shimano pads.

[kukamunga]

+1 to using your front brake a lot more than your rear

If cables are in good nick, wheels are true, pads and rims are good, and everything is adjusted and tightened properly, then check that you don't have 'anti-lock' compression spring thingies fitted at the top end of the curved-steel-tube 'cable noodles'. Ditch them if you have. Your brake levers should not be coming back to the bars at all.... ever !

Are they proper v-brake compatible levers? What level of bike and v-brakes do you have?

[Wakatuki]

Thanks for the information,

With regard to the front braking, on the tarmac I do use the front, grabbing for the rear only if I feel the front getting to the point of locking up. In this grim death situation I was travelling on a loose gravel surface and felt that at the speed I had reached by this time hard front brake would result in the loss of any form of steering, I was using it gently to try and scrub speed some off. Similar to an old issue I had on my BMX in the snow and no rear brakes even fitted, that's another story.

The MTB a 2004 Montari Comp has Brake Levers - Shimano BL-M420 Brakes - Shimano BR-M420. Amazing how addictive a $100 bike is over a $2000+ roadie. Mrs would kill me if I sold the roadie already. The bike is in great condition a few life marks on the frame, I have put new tires, tubes, front brake cable as that was ruined and new generic MTB pads on.
I did last night take some brake cleaner home, applied to a rag and cleaned the rim, lot of dirt came off. Then after reading everyones replies I have just purchased a new rear brake cable (will only replace inner, but with a bit of white, lithium to super lube) and some JETBLACK black with orange insert $16.95 (please advise if I should return in the next 4 hours, time now 13:30 10/4/13!) I also purchased the nipples to close off the snipped end.

I will inspect the pads on the Roadie to look for contamination. I will in the mean time get some of the kool stops, not seen a bad word about them yet.

Thank you.

[twizzle]

Nah - you should always grab big handfuls of brake at that spot. Otherwise, you won't "Pucker up" (otherwise known as "sphincter clench")

human909 and kukamunga can go first.

[human909]

Nah - you should always grab big handfuls of brake at that spot. Otherwise, you won't "Pucker up" (otherwise known as "sphincter clench")

human909 and kukamunga can go first.

I always grab handfuls of front brake as I said earlier! With the caveat that the surface is not loose (which wasn't mentioned in the first post)

[Wakatuki]

Nah - you should always grab big handfuls of brake at that spot. Otherwise, you won't "Pucker up" (otherwise known as "sphincter clench")

human909 and kukamunga can go first.

I always grab handfuls of front brake as I said earlier! With the caveat that the surface is not loose (which wasn't mentioned in the first post)

Onto the loose stuff onto a section nicknamed 'pucker up' a loose road section and again the rear would not lock up, not willing to reach hard for the front brake I hung on for grim death and got 4th place on Strava

Oh yes I did

Honestly thanks for the help.

[high_tea]

You don't mention whether your initial test was in the wet. I had some brake pads that were okay in the dry, but scary in the wet. I upgraded to Kool Stops - much better. Cleaning the rim might help, especially if they have grease on them.

And +1 to the suggestion about making sure they're adjusted etc.

[human909]

Oh yes I did

Honestly thanks for the help.

[eeksll]

I'd think you want to sort out your brake lever to bar problem first. Where is all the slack going.

New brake pads are not going to solve that.

[kukamunga]

My refurbed MTB is no longer pulling me up...... Now when I first fitted MTB generic $12 V brake pads and adjusted it all up it was ok the rear wheel would lock up if need be.......I ended up with a brake lever to bar moment

.....check that you don't have 'anti-lock' compression spring thingies fitted at the top end of the curved-steel-tube 'cable noodles'. Ditch them if you have...... Are they proper v-brake compatible levers?

Mismatched Lever Issues:

Old short-pull lever, new direct pull ("V type") cantilever

The excessive mechanical advantage of this combination will make it difficult to modulate the brake, and it may be all too easy to lock up the wheel.

The lever feel will be very soft and mushy.

The lever will travel too far before engaging the brake, and it may bottom out against the handlebar. Thus, the brake may be super-powerful at first, but as the brake shoes wear, the lever's bumping up against the handlebar will prevent full application. This is likely to be a particular problem in wet conditions.

If they are the original levers specced with the bike, I don't imagine this will be the problem. Worth checking though.....

[Wakatuki]

THX Kukamunga,
Its as the bike came, a search on the net for articles on the bike would seem to suggest this is correct.
Went out on the new pads last night in the pouring rain, got 2nd best decent time! I was being cautious too. So I would say the pads are 200% better in the wet than the old (new) black generics. One of the old pads had a chunk missing from it already suggesting to me something got stuck and has now moved on..
A quick look at my water bottle this morning and it is absolutely covered in road grime that smears to the touch and will not come off without heaps of washing up liquid and elbow grease the whole bike is coated in it. The road I am riding is closed due to land slip, so the only traffic it see's is constrcution traffic AKA dirty diesel trucks and plant equipment. Non the less despite the torrential rain I could scrub off speed in a controlled manner. I will be de greasing the rims again using brake cleaner before the next ride.
As far as my roadie is concerned I am just going to replace the pads and again degrease the rims, the road itself must be a contributing factor.

Thanks again.

[kukamunga]

Dishwashing liquid is very corrosive. Use an auto or truck wash (CT-18?) instead. Methylated spirits to wipe clean rims is probably cheaper and might work ok

Sounds like you ride in a very dirty area. It would appear a light hose down of your bike immediately after every dirty or wet ride, and regular checking and cleaning of braking surfaces (and drivetrain) are in order for you to prevent premature wear and problems in future

[human909]

As mentioned, rear brakes have significant flex in them. Cables, housing and seat stays. Take a look at the visible flex in the seat stays when you squeeze the rear brake! Back in the days before disc brakes were common many mountain bikes has brake boosters to reduce the frame flex.

If you cables and housing is good then its either break boosters OR improving the friction on pads vs rims. Often I find a simple pad replacement quicker, simpler and easier than other mucking about.

Dishwashing liquid is very corrosive.

That is totally unfounded. Dish washing liquid is a detergent and a fairly mild one at that. Dishwashing machine tablets are harsher but that is only due to the salts, again neither are corrosive.

[twizzle]

He used detergent on his bottle, not the bike.
And if the brakes worked fine before and the only thing which changed was the shoes, it's not going to be some basic fault with the bike, is it?

I tried some Swisstop GHP-II's on the TT bike, in the dry ONLY, ended up with stacks of metal in the shoe that was grinding the rim away. Back to kool-stop. I use the "Road" for race duty, and Dual for the commuter.

And I've also been riding around on the new roadie a lot, I left the original Shimano 5700 (2012) brake shoes in... quite impressed. I haven't tried them in the wet to see if they are soluble or metal-magnets though. But my rule of thumb is Kool-Stop for everything.

[Wakatuki]

Twizzle, thanks for reading the content of the posts... fully.
As I work in a car dealership I have a plentiful supply of wash and wax, very handy. Also the commercial brake cleaner is readily available. Dip a rag into the bottle and rub!
I had not noticed HOW dirty the roads were till last night. That was my first night in full rain, normally I may just get caught in a shower or a ride on a damp road. Last night was unreal.
And on the Kool-Stop - I am onto it, placing an order today, replacing all three common bikes with them. The MTB, FOIL and GLW's Dolce, with extra suicide brakes, she is not a good decent person...

The MTB has been left outdoors in the rain today and will get a soap down and rinse again tonight. Nice liberal application of ceramic chain lube and she will be fine. All major points were white greased and lubed up only a few weeks ago. BUT the rear derallier is giving me grief now, it goes slack when on the largest crank and bottom (smallest ring cassettes) when I back pedal a 1/4 turn on the descent. I know I should not back pedal, but its a bad habit when I switch from left to right turn. I believe I will re-look at the jockey wheels first and regrease, then if that fails soak the whole bloody thing in degreaser and then ceramic lube and pivoting it around to get lube everywhere, probably got a bit of fine grit in it as it's only just started to do it. Oh joy.

[twizzle]

BUT the rear derallier is giving me greif now, it goes slack when on the largest crank and bottom (smallest ring cassettes) when I back pedal a 1/4 turn on the descent. I know I should not back pedal, but its a bad habit when I switch from left to right turn.

Nothing wrong with back pedalling, unless crosschained it shouldn't cause a problem.

I'd just replace the jockey wheels, they are a consumable item anyway.

[Wakatuki]

Noisy roadie brakes are normally alloy chips in the pads. Clean or replace the pads.

Spot on, couple of fillings in the pads.

Fillings removed, rub with coarse sand paper all good.