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I have an outdated 90's MTB that requires single pivot brake calipers. The only brakes of this kind I have found are either for road bikes or BMX bikes. How do I know if they would actually fit before my online purchase?

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  • Brakes brake - as long as the dimensions work and your brake pull ratios are good, then which side of the groupset fence the brakes come from is not important. Do you require authenticity? Or would you be open to swapping the fork for something with Cantilever pivots ?
    – Criggie
    Aug 4 '19 at 1:53
  • Rear brake mount can't be changed with just replacing the fork. With Murray I'd recommend replacing the entire bike. The period correct way to rebuild one would be using cheapest junk available and not care if it works.
    – ojs
    Aug 4 '19 at 6:00
  • Oddly enough, 3 years later, I'm trying to do the same thing. None of the comments above seem particularly helpful. I'm pretty sure that a BMX U-brake a "990" will fit an old 80's or 90's mountain bike. If you had success in your project, I'd like to know. Thanks! Jan 12 at 6:17
  • Related, somehow: bicycles.stackexchange.com/questions/15024/…
    – Jahaziel
    Jan 12 at 15:24
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The features that need to match are reach from mounting bolt to rim and recessed / normal nut. A BMX sidepull brake will probably work, but it's better to check the measurements before buying.

For younger readers, Murray was a legendary BSO brand in the 1990s. They did come with centerpull brakes made out of thin sheet metal.

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My personal preference regarding brakes is the linear pull or v-brake. So I did search for "V-barke adapter plate" and the results show several options.

enter image description here

I have seen similar adapters used to install v bakes to a frame that does not have v-brake bosses. They attach to the seat stays by means of U-bolts or similar clamps.

I'd be confident enough for rear brakes installed this way, as the braking forces press the plate against the stays, so the clamps just need to keep the plate in place, not a huge deal.

enter image description here

On the fork however, I would not use it, unless I could install the whole thing behind the fork, but there is often not much space there. Also, A new fork with the proper brake mounts will be cleaner, more reliable. Particularly if you go for a rigid fork.

Another alternative would be braze-on brake bosses, but that requires specialist equipment and training, thus, it's better to hire the services of a frame builder, which may not be available locally.

Regarding BMX style brakes, Iv'e dealt with several no brand models to know that I would not be happy with such low brake performance unless it's only for commuting at speeds not exceeding 20 kph and without steep descents. I don't know whether brand-name BMX brakes are better performing.

The other caveat with this brake style, is that there is a wild amount of varying dimensions. They do not have a formal standard so different makers use different dimensions, some may have more reach than others, some have different mechanical advantage and use different metal alloys with very different compliance.

However, here are some tips that I used on my most recent conversion:

Measure the distance from the mounting hole (in the center of the bridge or center of the fork) towards the braking surface of the rims. The Brakes you choose should allow the same distance between mounting bolt and brake pads.

The brake arms have an eyelet that accepts the brake pad mounting bolt. When I'm unsure of the measurements I need, I tend to choose the option with the longer eyelets, in order to have more adjustment range. Also, I try to use the ones where the eyelet would allow the use of brake pads designed for V-Brakes, since they also allow for more adjustments, the pads are longer and are available in different compounds and price ranges, whilst the cheap BMX style ones only come in one generic rubber that is usually very hard and barely usable if they get wet.

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