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PostPosted: Wed Aug 20, 2014 8:29 pm 
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I bought my son 2013 Diamondback Element a few months back. It's a very fetching purple, that I'm not entirely sure he's that struck with.

He's not about to do any stunt or ramp stuff on it, he just wanted a bike for general riding, and he wanted a BMX. Although it came with a crappy front caliper brake and lever in the box, only the rear brake and lever were actually put on the bike. And in addition, the front wheel had a sticker on saying not to use a rim brake with it.

As he needed the bike for a rideability course, a working front brake was mandatory, so I managed to get him another front wheel that's got a braking surface.

In the meantime I've since got my hands on another of these bikes, albeit secondhand, but barely used. There was no brake hardware with it, though. I've really got this one for me, to hopefully get him to get over his qualms with the colour.

But I really do want some brakes at the front, so wondered if there were any decent dual pivot calipers that would work on a BMX. The forks have no bosses, so it's crown mounted calipers of some sort - what's as good as it gets, there?

And these front wheels with the stickers on about not using rim brakes - how do they get away with that, given they appear to include the front brake for legal completeness?

Rear isn't an issue for this second one, because although the seller has removed the brake and lever, they left the (removable) U brake bosses on the frame.


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PostPosted: Wed Aug 27, 2014 12:19 am 
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Neil, have a look for an ACS Boa - Skatepool on ebay used to list them now and again. Many years ago I ran 24" wheels on a DMR Sidekick with lovely chrome 24" forks which I used to occasionally race XC on - I fitted a Boa to the front as calipers were my only brake option and they worked very well - lovely brakes with ball-bearing pivots - shedload better than the cheap pressed calipers which come on completes to get them through British Standards.


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PostPosted: Thu Aug 28, 2014 11:08 pm 
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mamadirt wrote:
Neil, have a look for an ACS Boa - Skatepool on ebay used to list them now and again. Many years ago I ran 24" wheels on a DMR Sidekick with lovely chrome 24" forks which I used to occasionally race XC on - I fitted a Boa to the front as calipers were my only brake option and they worked very well - lovely brakes with ball-bearing pivots - shedload better than the cheap pressed calipers which come on completes to get them through British Standards.

I've bought some Dia Compe SS5 levers, after reading your 92 Apex thread, and I've got a couple of NOS Dia Compe MX 999 Big Dog dual pivots, plus a pair of new Dia Compe 806s on their way - will run whatever fits better, really.

It's only for the front, the back is U brake only, as the seat-stay bridge is rather ornamental / decorative.


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PostPosted: Fri Aug 29, 2014 9:58 am 
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Ah, you could have had my SS5s :lol: although I may leave them fitted to the frame and parts and sell it as a part build. Never used a dual pivot on a BMX but I imagine it would work a lot better than a simple caliper.


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PostPosted: Sun Aug 31, 2014 3:27 pm 
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So... had a bit of time to have a play with brakes.

The Dia Compe MX 999 Big Dog brakes actually wouldn't fit - despite being designed for BMXs.

The calipers were plenty long / deep enough, but they're just to narrow at the top to deal with the bigger / wider tyres on this BMX.

On the other hand, the Dia Compe 806s, despite not being as deep / long as the 999s, had plenty of clearance for the tyres. And with the pads as low as they can go, just fit nicely and work well. Impressive, given they're not BMX specific, but seem to be some road / crossover compromise.

And the brake I thought'd be easy on this bike (given it's my second, as I've got one for my son, too) a rear u brake? Well the brake bosses hadn't been removed, so that was one challenge I didn't have to fight, but they're pretty short bosses, so the bolts that came with the u brake I bought are too long. And looking at it, I'm not sure there's enough clearance (at least without putting some kind of washer / spacer on the brake boss) for the u brake arm that runs closest to the seat-stay, where the straddle connects with it.

So that's been removed, pending some other bolts and fitting stuff arriving. The stock u-brake on my son's identical bike fits fine, and works fine, so if nothing else, I'll see if I can get one like that.

At least I've got one good brake in the front, and I'll only be pootling around on it, and walking the dog for the moment.

I'll endeavour to post some pics of the front brake fitted - have to say, it works well and I'm glad I've done it, although I'm not convinced it's so much better (if at all) than the single caliper brake on the front of my son's.

How much is too much exposed seatpost on a BMX?

I'm running a long one (400mm) on mine, and most of the seat-tube must still be full of seat-post, when lining up a tape measure, but there still looks a lot out, wondered if that had been known to cause issues - I see as much, if not more, on MTBs, but then they tend to have bigger frames. It's a full 4130 frame, heat-treated, so should be reasonably strong. Worrying about nothing, or should I keep the seatpost a bit lower (will make more sense with pics)?

Thing is, because it's 400mm seatpost, even inserted as far as it'll go, there's still quite a lot exposed.


Last edited by Neil on Wed Sep 03, 2014 7:32 pm, edited 1 time in total.

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PostPosted: Sun Aug 31, 2014 8:32 pm 
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Pics...

Attachment:
IMG_20140831_183748.jpg
IMG_20140831_183748.jpg [ 155 KiB | Viewed 6334 times ]


It would be running a rear brake, except despite all my tinkering, the one I bought - in a very fetching purple, won't fit as things stand. The stock one works fine on my sons (below) though. So if some shorter bolts, and some spacer / washers to move the u-brake arm slightly forward on the boss don't work OK, I'll just try and get one like the stock one on my son's.

Attachment:
IMG_20140831_183816.jpg
IMG_20140831_183816.jpg [ 158.76 KiB | Viewed 6334 times ]


As you can see from the picture, the brake blocks are at the lowest part of the arm, but otherwise, there's plenty of clearance around the tyre.

Attachment:
IMG_20140831_183756.jpg
IMG_20140831_183756.jpg [ 134.67 KiB | Viewed 6334 times ]


And my son's:-

Attachment:
IMG_20140505_161330.jpg
IMG_20140505_161330.jpg [ 130.31 KiB | Viewed 6334 times ]


Front wheels on both are cheapo replacements, as the stock front wheel(s) doesn't have a braking surface. Slight snafu on mine, I was so sure that when I got one for my son's bike, it was the thicker axle (think it is on the back wheel), so that's what I ordered for mine... Then it arrived, and I realised you should always check first, because the front dropout only take the thinner axles. Doh!

My plan was for mine to be the testbed for running a dual-pivot caliper at the front, and once I was happy (as I bought two) I'd put it on my son's bike, but I can remember setting his up and finding it worked better than I expected, and then being a little underwhelmed with the one I've just put on mine. So think I'll leave that in obeyance for a while, and see how things pan out.


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 Post subject: good luck
PostPosted: Wed Aug 19, 2015 7:25 am 
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Joined: Wed Aug 05, 2015 8:15 am
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Good luck ~~~~~~~


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