Author Topic: Centering Dia-Compe brakes (Read 1104 times)

yelmarb · « **on:** August 29, 2009, 10:55 PM »

Really struggling to get my Dia-Compe 1000 brakes to centre when I pull the brake lever. At the moment only the left side brake arm (when sitting on the bike) is moving. The right side moves about 1/2mm before it hits the rim. I've tried to tighten the main bolt so that the brake sits to the right but that hasn't helped. I've also been adjusting the 2 nuts on top and the lower nut but the caliper always wants to pull from the left hand side. Any ideas?

SteveG · « **Reply #1 on:** August 29, 2009, 11:58 PM »

First you need to release the spring and make sure it not bent one side more than the other. Adjust it if you need to and then re-attach it.
Next loosen the adjuster off so you get a reasonable amount of travel when you pull the lever and then adjust the pivot pin nuts (not the one holding the caliper to the frame).
It will take a few goes to do this and you need 2 spanners, loosen the locknut and tighten the other then lock it up again with the locknut. Don't overtighten the nuts as it is easy to strip the thread. You will need to find a comprimise between the nut being tight enough to stop the arms moving but not so tight the caliper wont release.
Once the caliper is opening and closing properly you need to set the cable so the blocks are just off the rim.
If the caliper still pulls one side more than the other you either need to bend the spring to make that side release properly or slightly loosen the frame attachment nut and twist the caliper the way it needs to go.

Hope this helps, if not it might be cos I've had a few

It could also be the brake cable holding the arm to one side to make sure it isn't too tight or loose

MartyC · « **Reply #2 on:** August 30, 2009, 04:20 AM »

Using a largeish flat blade screwdriver, place the blade on the spring and gently tap the screwdriver with a hammer until it centres, another way is to use a centreing tool availble on egay. Also, checkout this how to on the ParkTools website... http://www.parktool.com/repair/readhowto.asp?id=22

kevin rettie · « **Reply #3 on:** August 30, 2009, 09:34 AM »

That park tool website is brilliant, glad I read this post - cheers guys.

yelmarb · « **Reply #4 on:** August 30, 2009, 09:54 PM »

Thank you very much for you replies. I've tried bending springs and tightening and loosening the 2 bolts on top of the caliper and I've cut about 4" off the length of the brake cable but the left of side of the caliper is still the only one that does most of the movement - until it hits the rim and then the right side decides to move in - about 1mm.

So tempted to go down to my LBS and get them to sort it out (of which I do support by buying products from them) but you know..... it's my vintage BMX... I don't want anyone else messing with it.

SteveG · « **Reply #5 on:** August 31, 2009, 12:41 AM »

Perhaps a picture of how it's set up at the moment might help. Brake calipers aren't the beat quality but with a suitable amount of fiddling they can normally be made to work ok. I can't really think what else could be causing the problem.

moley · « **Reply #6 on:** August 31, 2009, 01:09 PM »

SteveG has basically said it all!

Grease the 2 nipples that hold the spring at the back of the arms!!

This will allow the arm to move more freely up and down the spring. If the spring is moving freely on one side but is sticking on the other then it will pull one arm in quicker than the other!! Check the nipple grooves are smooth from paint and other crud and grease them like the proverbial pig!!

Make sure you have the correct washers between the arms on the spindle bolt.

Some are plastic and others are metal. I'm not sure which came with the 1000's but I think they're metal.

Greasing these should help too!

Dont overtighten the spindle bolts nuts at the front!! They should be tightened against each other so that they dont come loose but they shouldn't be tightened against the arms as this will restrict the movement. Similar technique to 1 pc cranks to stop them coming loose!!

Front two nuts tight against each other and the back nut tight to stop the spindle moving. The spindle should be centred based on the integral spring housing. The spring can be moved to help centering but it can't be moved very far. So centering the spindle first will give you a good place to start.

Have you tried moving the spring all the way to the other side to see if it swaps the sticking arm to the other. If it does then you just haven't centred it right.

Make sure all moving parts are greased and are free moving.

Make sure you dont grease ya pads though!!

Check your wheel is centred too!!

If its slightly to one side then add/remove washers to pad it out on both sides to get it centred.

As SteveG said. A piccy will help diagnose. If the brakes were bought used then explode the parts. Maybe your missing a washer that goes between the brake arms or summat!!

Thats it!! I'm all out of ideas!! $:-\$

yelmarb · « **Reply #7 on:** December 05, 2009, 03:54 PM »

Sorry this is a little old now but thank you for all of your replies. I think the main issue here is the brake cable. I can't seem to grip it tight enough to stop it slipping, hence the caliper will always pull to one side.

The brakes did come with some lovely chrome plated cable holder things but they're too small to wrap around the centre tube of my frame. How do you clamp the cable tight enough so it wont move when you pull the brakes on?