Adjusting linear pull brakes

[mybike]

As I've mentioned before I have this ancient Tesco special that I inherited from my son which I am riding & adjusting/learning to adjust.

One of the areas I've had a problem with lately is the front brake, I'd pull the lever right back & the wheel would still go round. I think I've got the answer & fixed it but knowing the expertise here thought I'd check.

Here is the RHS brake/block as it was.

So the first thing I noticed was that little L, the block was clearly on the wrong side. Then I thought that there isn't much leverage with the block near the hinge so I moved it up in the slot after swapping the pads:

Now there is a bit of an angle on the pad but it does seem to work much better. Has anyone any comments or suggestions, is there anything wrong with that I have done?

 

[Smokin Joe]

I've never used that type of brake, but if it works as you have it and everything is tight and secure I'd say you're ok.

 

[Yellow Saddle]

The photo in the bottom is bad. Life and death bad. Something called pad dive can happen when you have an angle like that. Pad dive = face plant.

Linear pull brakes aka V-brakes have a large cosine error. Not only do the pads move towards the rim but they also move downwards. That's because it is a short little lever describing a small arc.

You have to adjust it so that the pad connects the rim square-on. In other words, with the cable released and you holding the two levers with pads against the rim, the two round shoe posts will be perpendicular to the rim's braking surface.

On that particular tyre width there is a fine line between getting the pad to connect squarely and not touch the tyre when it does. Make absolutely sure it never touches the tyre. By absolutely, I mean absolutely. Many cheaper tyres are not symmetrical and will touch on high spots. If you check whilst the wheel is stationery, you may miss a spot.
Fix.

 

[mybike]

The photo in the bottom is bad. Life and death bad. Something called pad dive can happen when you have an angle like that. Pad dive = face plant.

Linear pull brakes aka V-brakes have a large cosine error. Not only do the pads move towards the rim but they also move downwards. That's because it is a short little lever describing a small arc.

You have to adjust it so that the pad connects the rim square-on. In other words, with the cable released and you holding the two levers with pads against the rim, the two round shoe posts will be perpendicular to the rim's braking surface.

Fix.

OK, I suspected there might be a problem there.

 

[shouldbeinbed]

Put the block back down where it was, the whole face of the brake pad should contact the rim, not just the top edge as you have adjusted it to.

While the blocks are loose you need to do is 'toe them in' get a lolly stick or piece of card and put it in the back end of the brake block so that when you tighten them up the front edge of the block will contact the rotating wheel marginally before the rear and that momentum will help pull the block onto the rim, improving braking and stopping any brake squeal or chatter.

To get them set so that they stop the bike before you've pulled the lever to the bars you need to get the cable tension right, it sounds as if it has slipped at the brake arm, or its not been fitted into the brake lever properly.

1. Slacken off the cable at the brake arm.

2. Pull the brake lever fully on and look inside the bit that opens up, there will be a piece in there that holds the cable end, it should be pointing directly out the back of the brake, with the cable running out of the brake through the knurled adjustor knob, set this knurled knob about half way in/out while the cable is still slack, this knurled knob is your fine tune adjustment, as you get more into fettling you can decide better how much in/out you set it when changing cables.

Now hold the 2 brake arms, with one hand, so they just about touch the wheel rim, equal distance apart. With the other hand, pull the cable tight in the brake arm, making sure it sits in the groove properly, then tighten the bolt holding the cable in place. *edit- sounds like you need 3 hands, you can do the cable and bolt one handed, if you are struggling though, you can use a bit of string ono round the brake arms when you have them gapped properly to the rim to give you both hands to hold the cable and tighten it up. *end edit*

This should have the brakes set so that you can get good braking without squeezing the lever all the way to the bars. If they are too quick to grab or your wheel is out of true & rubbing in parts as it rotates, you can slacken the cable slightly at the knurled knob to make the brakes sit slightly further off the rim and need a longer pull on the lever to stop effectively. If you still think they're not gripping quickly enough for you, or as the cable stretches with age you can turn the knob slightly the other way to pull the brakes closer to the rim.

NB: If the wheel rim is out of true, it will do you well to learn/pay LBS to true it by ensuring the spokes are properly tensioned around the rim. Cheap enough to pay for and with a bit of practice not a hard job for the amateur fettler.

 

[Rickshaw Phil]

I won't add anything to the adjustment advice given above but do want to say; those appear to be the same brakes that my old Apollo came with as standard. They were nigh on impossible to adjust satisfactorily due to the naff quality materials they were made from and eventually broke.

Personally I'd look around for replacements - almost anything aftermarket will be better.

 

[mybike]

I won't add anything to the adjustment advice given above but do want to say; those appear to be the same brakes that my old Apollo came with as standard. They were nigh on impossible to adjust satisfactorily due to the naff quality materials they were made from and eventually broke.

Personally I'd look around for replacements - almost anything aftermarket will be better.

I think you're probably right. Still I'm having a lot of fun & getting some good help from folk here.

 

[mybike]

OK, so the shoe posts are now perpendicular to the rim & curiously now the brakes work quite well. I've had to discard the boot as it's totally shot but I'm not sure how necessary that is.

thanks guys, one and all for the help.