Dia Compe988

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Dodgers69
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Dia Compe988

Post by Dodgers69 »

I've just bought the 988s they assemble ok , spring is correct way around etc but...when tightening all they do is just compress onto the boss which results in just seizure of movement. They feel like they should be good apart from this oddity.

Any ideas please. Other style with Shimano spring in hole ok & Suntour 'self energising ' ones also similar concept to these DC 988s also ok
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simonineaston
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Re: Dia Compe988

Post by simonineaston »

I think the brake rotates around a bush that's part of the assembly, which then slides onto the frame boss. Given that frame bosses can come in slightly different lengths, I imagine the brake assembly is designed to cope with that variety.
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
colin54
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Re: Dia Compe988

Post by colin54 »

It looks like you need to use a spanner to move the red spring housing (and hence hold the pads away from the rim) whilst tightening the pivot bolt,
are you doing this ?
Screenshot (14).png
Some instructions :-
https://www.diacompe.com.tw/wp-content/ ... 8-2017.pdf
Nu-Fogey
Dodgers69
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Re: Dia Compe988

Post by Dodgers69 »

Thanks both for answers so far; yes I'm utilising the red section to lock/set the spring tension , that's not the issue here, it's the subsequent to that securing of the bolt into the boss, that won't allow any movement of the brake when tightened (had to be just tight enough to hold the red adjusters in place)
Barrowman
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Re: Dia Compe988

Post by Barrowman »

Haven't come across that particular brake , I do have a few machines with Cantilever brakes, all have a washer under the head if the bolt.
Just searched that brake on E Bay and the picture shows thin Washers in the exploded diagram which I assume go under the bolt heads. Are you using Washers?
Cyclothesist
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Re: Dia Compe988

Post by Cyclothesist »

I'm not familiar with this brake so I may be wrong with this suggestion...
Could it be dried up grease and a bit of corrosion where the brake body pivots around the red spring adjuster insert? It might be worth seeing if you can free it up with a penetrating lube. Or if possible dismantle, clean and relube the pivot.
Dodgers69
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Re: Dia Compe988

Post by Dodgers69 »

Thanks again for comments.
The brakes are brand new and freshly prepared bosses.

Was hoping someone was a user of these as still a viable brake, as necessitated by older narrower spaced frame fittings.

I suspect the Suntour mentioned in original post with same concept (not using spring hole on boss) is a better design as meets the base of the boss with the tension lock piece, as against having the bolt clamp onto it, on the exterior.
rjb
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Re: Dia Compe988

Post by rjb »

I'm using similar diacompes but mine have an eccentric bush which alters the height of the blocks as you rotate the carrier. Your red carrier bolts up tight to the stud so if the brake arm is binding it's an issue with the fit on the carrier.
Does your spring protrude though the rear the carrier. You may need to fit it through the frame location hole or trim it on a grinding wheel if it's too long.
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway X2, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
Dodgers69
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Re: Dia Compe988

Post by Dodgers69 »

No, as noted, it's not the spring into frame type.

The bosses are old but this design seems unsuited. Shimano ones can get away with it as don't rely on clamping tight their own springs as the frame does it.

Other dia compes and the Suntour mentioned have the adjuster at the rear not under the front clamp.
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simonineaston
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Re: Dia Compe988

Post by simonineaston »

An interesting read as its in the back of my mind to alter my front forks to use canto brakes and was considering this brake…
S
(on the look out for Armageddon, on board a Brompton nano & ever-changing Moultons)
Cyclothesist
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Re: Dia Compe988

Post by Cyclothesist »

Could it be the brake mounting bolts that are the problem? They come in different lengths and with differing bolt heads so often the bolts for one manufacturer don't work for the brake of another. Did the Dia Compes come with bolts?
Brucey
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Re: Dia Compe988

Post by Brucey »

it sounds to me like the bosses might be too short for that particular model of brake.

You may be able to rectify matters by either using small spacers between the bosses and brake, so as to lengthen the bosses slightly or by remachining parts of the boss.
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
pwa
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Re: Dia Compe988

Post by pwa »

It can be worth playing around with it for a while, because I have had the same sort of problem with the brake arm not quite going back far enough to leave a fag paper thickness of boss protruding for clearance, and it has come down to something like a bit of paint or something preventing the brake element seating itself back far enough. The difference between perfect and sticking can be tiny.
cycle tramp
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Re: Dia Compe988

Post by cycle tramp »

Apologies for being a bit John and Jane about this...

..way back in the 90's I had several sets of 986 cantilever brakes, which worked in the same way and had their own independent spring tensioning device (only it was behind the cantilever arm, Instead of indront of it)

The actual cantilever arm was slid onto its own long spacer tube, which was then slid over the brake boss - I think the 988 work in the same manner... are there any spacer tubes with the cantilever arms?
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Dodgers69
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Re: Dia Compe988

Post by Dodgers69 »

Thanks again for all the comments. The boss is immaculate/clean of paint and they are always standard dimensions.

No spacer tubes, just as in info sheet in a post above.

I think when worn(including the tip) there's the issue. I did start to research a form of copper pipe sleeve, what's needed with these for me at least is a 8mm ID ring but very slim 0.5 mm like used in jewelry making and place in front and behind.
Currently I've fitted a brand new Shimano CT_91 on the front which are the most fuss free.
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