pgoat

After a bike shop mechanic adjusted my front side pull brakes ridiculously tight (wheel spun, but just barely had enough clearance to do so), I was too busy to re-adjust the cable and I just rode it several weeks with the quick release open. I did this to have more spinning clearance and a more 'normal' feel on the hand lever.

It's a 1985 bike, Dia Compe Royal Compe 400 single-pivot side pull.

After a while the caliper started chattering (you could see it fluttering forward with the rim while feathering/modulating, especially on descents) and the left arm (the side opposite the cable/quick release) no longer returns after braking (I had to reach down and return it by hand to get it off the rim after braking).

I did a good cleaning and lube and was messing with the pivot/lock nuts and checking the cable this weekend, but then I saw this:

Homebrew01

Looks broken from here, but you have a better view and can touch it.
Seems a rare part to fail.

prathmann

Yes, looks broken. I've had that happen a couple times. Once the LBS had an old brake caliper with a similar-looking spring that they sold to me for a few dollars, the other time my LBS then actually had a new replacement spring.

pgoat

thanks guys. I'm thinking definitely broken, based on what I see and feel. This is a first for me, so I was just looking for some feedback.

This was actually a decent-performing brake, so I may ask around a few shops here that stockpile old parts in the hopes they have a donor spring... But I have another bike with a front side pull from the same era (alas, a 57mm reach, so it's not as firm a stopper) that I'll likely throw on here - it's my commuter bike, so I'm hoping to have things working safely by Tuesday morning.

The old bike that's donating the long reach is used for longer rides, and will probably get a newer dual pivot. Having used both, I certainly prefer the more modern design, generally speaking.

alcjphil

As long as you can adjust the brake pads to properly meet the brake track on your wheel, the other brake will deliver the same mechanical advantage as the one you will be taking off. However if the other brake has a longer reach, you may not be able to adjust it to fit

Leisesturm

Actually what you are calling "long reach" is more accurately "medium reach". And dual pivot technology is more readily available in the "short reach" variety. Maybe medium reach, but I've never checked. Who doesn't prefer the modern designs? But don't completely discount the legacy stuff. It was throwing people over the bars and killing them long before dual pivot tech, to say nothing of hydraulic disc tech, was invented to do it far more expensively.

JohnDThompson 

The springs on side pull brakes are all quite similar, particularly if they're from the same manufacturer. I suspect you could scavenge a spring from another Dia-Compe caliper and use it in yours. It might not have the fancy chrome plating of the original spring, and the legs might be longer, but neither issue would affect function.

FBinNY 

If you can't find the spring, feel free to send me a PM. I have a number of DiaCompe brakes of this vintage. While I probably match your brake exactly, I probably have one uses the same spring, but is missing other parts.

pgoat

thank you all for the input and offer of parts - yes i meant 'medium' reach, really - both bikes are Trek 500s; and '85 and an '86 (some of you may recall I had the rear drop out replaced on my '86 about a year ago, when another BF member kindly donated a spare to me), both designed for 700Cs.

The Shimano 57mm max side pull from the 86 fit just fine on the 85 that had the broken 49mm Dia Compe (I did need to move the brake pads up a bit), so I'm ready to roll for commuting.


Oh, and that spring was good and broke, all right - crumbled in my hands as soon as i removed the caliper from the fork.






I slapped the busted Dia Compe onto the 86 just to check reach to the rim and it makes it fine with the pads positioned all the way down, so I'll probably hunt up a replacement spring for this caliper or, failing that, just buy a modern dual pivot that can reach 49mm to get the 86 bike back together.

Miele Man

I've seen the odd spring get badly damaged or broken like that when the person adjusting the brake to center it got a little to enthusiastic with the hammer when hitting the screwdriver that was placed just about where the break on your spring is.

Cheers

pgoat

The bad adjustment was done when the shop was replacing my headset - which also was done incorrectly (wrong stack height - and additional huge new spacers were too thick, so you can't tighten it down properly, and I didn't get the old one back, otherwise I'd re-use the old spacers). I'm envisioning some sort of bad juju that happened there.

pgoat

LOLing at this. Especially because I personally prefer to adjust my calipers so the pads are close to the rim (I hate spongy brakes) but I've never gotten back a bike from a shop with the front brakes that tight. It was as if I'd special-ordered an endo.

HillRider

That's another advantage of dual pivot brakes, you can center them by hand. No special wrenches and certainly no hammers and screwdrivers.

pgoat

Yep - to be honest, I'd be happy to pay a few dollars for an old spring to get the vintage dia-compe caliper working being these are old bikes, not particularly special or high-end and used for commuting and easy-going rides.

But as long as I need to replace the front brake anyway - and there are recent Ultegra DP calipers to be had new for around $50 (which i can later take off and move to a modern bike if/when needed) - I'm okay with slapping something on there that is not a headache to set up.

I assumed because my 86 Trek came with medium reach calipers (the Black Shimanos seen below) that a short reach wouldn't fit - but the broken Dia Compe (49mm max) did. So I'm leaning new brake, since I would be more likely to use that bike on longer rides with more descents. It was my main club bike for about 5 years (B rides, 40-100+ miles) and aside from MacGyvering a bar-mount index shifter (beats DT shifters when pacelining, imho), the best thing I did to that bike was put a cheap medium reach Nashbar DP caliper up front.

I didn't realize back then I didn't need a 57mm reach and the nashbars were very cheap re-badged Tektros (I once yanked the cable right out of the plastic bolt during a panic stop). But still, set up was so easy and the performance was much much better while they lasted (both stop power and modulation). A shame the build quality was so flimsy... When I went back to the OEM sidepulls, the inferior performance was pretty noticeable.

Having said that, the black caliper is on my 85 now and working fine for basic commuting - more than adequate getting me to work this morning, even if it irked me that after a solid 15-20 minutes of fiddling to center it yesterday, it was immediately all cockeyed as soon as I'd ridden a block or two from home today... *sigh*

hairnet

You're in NYC, go visit a bike co-op and salvage a spring there. I'm sure they have many busted calipers with missing parts that you take a spring from.

pgoat

i'm gonna poke around a few places, for sure. Still leaning towards new brake, but I also hate to throw out the old Dia Compe. I wouldn't mind replacing the spring for cheap and keeping it as a spare...

hairnet

Well, you can always mail to me for, uh, proper disposal.

WizardOfBoz

It was sobering to note that as I read your post, I realized I was that guy! I'll be a little more judicious in the future.

pgoat

Visited my favorite local odd parts shop - they had a nice chromed spring from an old donor Dia Compe, and presto - my old caliper is good as new. $5 and the guy even installed it for me. Can't beat that.

The 'new' spring actually feels much sturdier and stiffer than the original, judging by hand squeezing.

I'm going to install it on the other Trek today. I'm tempted to swap the rear brakes so the nicer 86 bike gets both Dia Compe calipers. I'll see how much energy I have later...