Linear birake problems
 

Just bought a brand new "Windsor" comfort bike from BD.Assembled it and can't get the rear brake to work right.The cable seems to loosen after squeezing levers caused because the calipers don't have enough snap to tension the cable upon release of the lever.The type is a " C-star Alloy silver V brake Linear Pull."Anybody have a clue to how to fix it?The fronts work perfectly.Yes I know they're cheap and the bike is cheap but they should work nonetheless.I bought 7 of these bikes in different sizes in order to start a NYC bicycle tour business.I will be gone all day so if you need more details I'll respond tonight.Thanks.

Most V-brakes have a spring tension adjustment screw on each arm to set their return force and balance them. Tighten one or both of these screws. Otherwise, check if the cable itself is kinked or frayed or the housing has something inside blocking the cable's free motion

By the cable being 'loose' I will assume you mean that the cable remains attached but falls slack in the middle of the run.

Rear brake springs are not able to overcome friction and pull the cable tight when brake lever is released.
Either find the source of friction and reduce it, or increase the strength of the brake springs.



Check that there are no kinks in the cable and housings, make sure that the ends of the housings are cut and ground flat underneath the ferrule end caps, also see if any loops are excessively long while doing this, lubricate inside of housings with triflow before reinstalling cables.

Check brake arms for springiness when no cable is connected, if they are weak even without having to pull cable, either rebend the springs, or reset the spring position to a higher one (under the brake mount are 3 spring mounting holes)

Strongly recommend based on the issues you are having that these bikes be taken to a good LBS and given tuneup/safety check before allowing paying customers to ride them. Injury liability from impropor assembly can easily kill your tour business.

+1 Give the braking systems a thorough going-over. I helped a friend with a BD bike and virtually all of the cable housings required attention. Most were too long and the ends were poorly prepared. Once everything was tidied up they worked pretty well.

Since you are holding out services to the public I strongly suggest that you consult an insurance professional and an attorney regarding liability coverage and possibly forming an LLC or similar entity to protect your assets. A liability judgement against you can not only kill your business but can also financially ruin you personally.

As others have noted, the spring may not be able to overcome friction in the longer cable run. However, in my experience, I've never found a brake who's weren't strong enough if the cables were running freely (front or rear) so check the cable.

The other (rare, but not all that rare) possibility is that one of the canti posts is a hair short so that when the mounting bolt is tightened it binds the brake arm before bottoming out on the end of the post. The easiest way to confirm or eliminate this possibility is to loosen both mounting bolts. If that solves the problem, the cables are fine, but the problem is harder to fix.

If the posts are the removable/replaceable type, ask BD for a new pair (or if not maybe a new bike). Otherwise you need to thin the stack of the moving brake parts, which can sometimes be done by removing a washer or replacing it with a thinner one. Or add a thin spacer to extend the end of the post. I've done this successfully using O-rings, which get mashed down as I tighten the bolt, or with home made washers cut from paper and soaked in oil. Some mechanics solve the problem by using loctite to hold the bolt in place so they don't need to tighten it to the bottom, but I'm not a fan of that, especially for a rental bike.

People spend a lot of time worrying about shifters but, in my experience, brakes are more troublesome. Assuming reliable bikes are a part of your business plan, I'd buy 7 pairs of Shimano Acera V-brake calipers and solve the problem permanently.

Better brakes are always a nice thing, but won't solve the problem if it's the cables or posts. The first objective is to identify and resolve the actual problem. Then the OP can consider new brakes to improve overall performance.

The brake bosses usually have three holes to allow for the adjustment of spring tension. Start with the middle hole and if that isn't working for you , move the spring to the hole that gives you the highest tension. Al

Found and played with those spring tension adjustment screws and managed to make the back brakes pretty functional.Also improved the angles so the cable moves smoother.The front ones are now quite excellent.the back brakes are too squishy so I am going to check and lube the housings next.I never had new brakes before.The brakes are very powerful and also noisy.Will that improve as I wear them in?Appreciate your advice on liability.All people will sign a personal injury waiver at the very least but I fear insurance will be prohibitively expensive and make it impossible to turn a profit.We'll see.As far as a LBS putting these bikes together I consider myself competent to do it myself as well as Maintain them.I never had experience with these types of brakes before however.Thanks for your input!!

Just bend an outward curve in the straight spring, to increase its return pressure.