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PostPosted: Wed Oct 02, 2013 8:11 am 
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Location: Norfolk
Recently, whilst trying to assemble components for my 80's Atala, to my dismay I could not mount the Suntour Sprint brakes with recessed allen bolts on the frame. Yes, thats right, even though my Atala is of the year 1987 (years after recessed allen bolts became standard) it was made for 'older' 1970's style nutted brakes. Mercian Cycles gladly drilled out the fork crown to fit an allen bolt just fine, but they refused to drill the rear brake bridge because they said it would 'weaken it'. I mulled over drilling/grinding it myself but I trust Mercian's frame-modification repertoire.

I know tektro do make modern brakes with a nutted fitting for older frames, and SJS cycles just sell the bolt part for some models of modern dual pivot Tektro and Shimano models: http://www.sjscycles.co.uk/tektro-tektr ... prod24266/

But I really want to run the Suntour Sprint brakes to keep everything period correct and to match the other Sprint groupset parts on the frame. I thought about getting some stock all thread and grinding it down. The only other thing I can do is get my hands on another Sprint front brake and mount it at the rear where it will be long enough to put a nut on it. But Suntour Sprint brakes are very rare and go for a high sum on ebay.

My question is, if you were to adapt recessed allen bolt brakes to a vintage frame for nutted brakes, how would you do it?


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PostPosted: Wed Oct 02, 2013 8:19 am 
retrobike rider / Gold Trader
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edit: you've already had my idea.


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PostPosted: Wed Oct 02, 2013 8:24 am 
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cce wrote:
edit: you've already had my idea.


Yes, I know. Like I said finding a Suntour Sprint front brake is like trying to find diamonds in a sewer.

What if I use the rear brake (with its shorter bolt) as the front and use the nut on the inside the fork? In theory it means the front brake will only go through 1 hole in the fork instead of two. Will it hold up under strong breaking forces, though?


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PostPosted: Wed Oct 02, 2013 9:29 am 
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I think I can see your dilemma. I'm not sure I would trust adapting the rear brake to make the front, the front being the most important. Maybe if you filed down a piece of aluminium to match the curvature of the inside of the fork tube, then double nut it.

Like this:

Attachment:
Untitled-2.jpg
Untitled-2.jpg [ 43.66 KiB | Viewed 466 times ]


That may give a solid fix.

I wouldn't rule out drilling the rear bridge though. It depends on the style of bridge but there is less breaking force at the rear, maybe you could post a pic?

Not that I'm inferring Mercian have got it wrong, but it depends on how you use your brakes. I'm heavy on the front and light on the rear :)


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PostPosted: Wed Oct 02, 2013 12:41 pm 
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otherself wrote:
cce wrote:
What if I use the rear brake (with its shorter bolt) as the front and use the nut on the inside the fork? In theory it means the front brake will only go through 1 hole in the fork instead of two. Will it hold up under strong breaking forces, though?

I did that but it's not ideal. You do need to make sure it's done up properly. Because the nut will bottom out onto a concave surface, the flats on the nut tend to stop the nut turning before it is fully tightened. It actually worked fine on my bike and I think I covered ~3000 miles of commuting with it like that, probably a lot more. I was always going to extend the threaded part by welding an extension on. Obviously I trust my own welding, but you'd want to be damn sure you trusted whoever did it or you might end up with no brakes. Another option is to get a long nut (12-15mm long - they are about but might take some searching) and screw in a second threaded brake axle on the end of it.


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PostPosted: Wed Oct 02, 2013 2:29 pm 
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Location: Southend-on-Sea, Essex, Uk
I can't say I know the Suntour Sprint Calipers intimately, but if your frame has now been drilled to take your recessed front Caliper, isn't it just a case of replacing the pivot bolt in the rear Caliper with a nutted (i.e. longer) pivot bolt from another nutted rear Caliper. I've done this before on some Campagnolo Record Calipers and just used a rear pivot bolt from a cheap set of Calipers. Not as pretty as the Campagnolo pivot bolt admittedly, but the brakes don't know!

Steve.


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PostPosted: Wed Oct 02, 2013 4:41 pm 
rBoTM Winner
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otherself wrote:
cce wrote:
edit: you've already had my idea.


Yes, I know. Like I said finding a Suntour Sprint front brake is like trying to find diamonds in a sewer.

What if I use the rear brake (with its shorter bolt) as the front and use the nut on the inside the fork? In theory it means the front brake will only go through 1 hole in the fork instead of two. Will it hold up under strong breaking forces, though?


I like this idea and because of carbon frames you can get very long recessed nuts. As long as it seems secure once installed I don't see why it should be weaker than the proper front brake.

Alternately you might be able to source a center bolt from another Suntour caliper. It is possible that different groups had the same center bolt.

Steven


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PostPosted: Wed Oct 02, 2013 4:50 pm 
Old School Grand Master
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Joined: Fri Oct 14, 2011 8:41 pm
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Location: Cumbria
Can you borrow something like an old campag / shimano / modolo / zeus bolt for the rear and see if it is compatible? somebody might have something knocking about.

Shaun


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PostPosted: Wed Oct 02, 2013 5:46 pm 
rBoTM Winner
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Hi,
Just seen your problem, I would not use the nut inside the fork, but Steven (lewisfoto) is on the right track. Using the rear brake calliper bolt for the front brake and using a long calliper bolt would be much better and easier. Have a look at sjs cycles, they stock a 30mm long bolt that should be long enough, (or could be cut down to required length)

http://www.sjscycles.co.uk/shimano-cali ... prod28697/

The front calliper bolt can then be employed on the rear, with a nut.

Alternatively, the calliper bolts on the suntour brakes are virtually identical to those used on Shimano Dura Ace BR-7400 or BR-7402.


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PostPosted: Wed Oct 02, 2013 6:34 pm 
Dirt Disciple

Joined: Sun Feb 10, 2013 9:48 pm
Posts: 78
Location: Wirral UK
Here is a solution that worked for me:
viewtopic.php?f=12&t=272634&start=15


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