jackbombay

EDIT- I figured ot the issue, this bike does have Sora ST-3503 levers on it which are "New Super SLR" which have increased cable pull and "can be used with "Super SLR" (less cable pull) calipers", but the result will of course be reduced caliper force for any given amount of force at the lever, so getting some new calipers that are "New Super SLR" is the way forward here. If one wanted to make a very powerful brake system they could use NEW SUPER SLR calipers with SUPER SLR levers, but the pads will not back away from the rim all that much, and there could be issues with the brake lever hitting the bar, but I doubt it.



My girlfriend just picked up a 1997 Klein Quantum Race, it has some shimano 600 dual pivot brakes on it and the springs seems quite stiff, they "work fine for me", but her hands are certainly smaller than mine and not as strong and on longer descents her hands get quite fatigued. When I initially test rode the bike the stiff springs actually caught my attention, but I didn't think too much of it, but, they are a bit of an issue.

The bike is kept up well, and there isn't any drag in the cable housings, the levers are Sora as the original Ultegra levers on the bike had worn out and were replaced.

It seems I could remove the brake and tweak/bend the spring a bit to reduce its efforts to keep the brake open? Or has anyone else addressed this issue before?

Here are a couple pics,

daverup 

I've got a set of those and they don't seem worse than others to me.

hazetguy 

difficult to see in the pics, but which tension setting is the sping set at?
you can adjust the tension by flipping the plastic guide.
https://si.shimano.com/en/pdfs/si/U-...000-00-ENG.pdf

roadcrankr

Nice score on the Klein. Excellent framesets.
You might tackle a caliper rebuild, front and rear. It could result in smoother operation.
Also, remember to put a tiny dab of grease on where the spring rides on the caliper.
My nineties Dura Ace utilizes some sort of spring tension adjuster. Unsure if that would improve things.

daverup 

My 600 Calipers are in the lower tension setting on the spring pointed out by hazetguy .
Use caution if you tear these down. I believe the pivot bearing is a stack with tiny ball bearings.

Do you have another caliper that your girlfriend uses on another bike? Swapping it temporarily could help diagnose the issue.

jackbombay

The spring is in the "less tension" position, but that link got me going down the shimano worm hole and I found this quote below here,



The bike does have Sora ST-3503 levers on it which are "New Super SLR" which have increased cable pull and "can be used with "Super SLR" calipers", but the result will of course be reduced caliper force, so getting some new calipers that are "New Super SLR" is the way forward here it seems...


The amount of ways that bike parts can "not play well with each other" astounds me sometimes...

hazetguy 

ha, yeah, totally agree on this. i rebuilt a set once, and said never again. time consuming, rather detailed, frustrating excersize to say the least.


op, you could/should perhaps drip some lube into the pivots.
also, remove the spring from the plastic tension piece, and make sure there is no rust or corrosion on the spring. then oil the spring when reinstalling to help the spring slide through the plastic more easily.

jackbombay

Akkkk!!! Good to know!

I just did this and it did help some, but, still fairly stiff.

My previous post, #6, has the issue correctly identified, I had no idea that different dual pivot shimano brakes have different cable pull requirements, SLr is different from SUPER SLR, which is different from NEW SUPER SLR, and the previous owner replaced the SUPER SLR ;levers with NEW SUPER SLR levers which does result in less powerful brakes, so I've ordered up some NEW SUPER SLR brakes to go with the NEW SUPER SLR levers.... *sigh*

given all the different cable pull ratios one could get super powerful brakes by using SUPER SLR levers with NEW SUPER SLR calipers...

KCT1986

If you're referring to the bearing system as pictured below, it is just a special bushing. This is an example from back when they first used it.



Shimano's description in 1986 or so.


It was called 'thrust bearings' by Shimano, little balls imbedded in the bushing that don't really rotate but just reduces friction with the coated washers that sandwich it. Same system that is used by many of their 'nicer' dual pivot calipers that followed it.

The balls aren't loose, so no concern of it coming apart.

daverup 

I don't know what Shimano intended with this thrust bearing. I just know if you take the caliper apart, you could get a shower of tiny bearings. If it was intended to stay in one piece, it did not on the one I rebuilt.

KCT1986

Never had one of these come loose (yet).

But, being that the bushing is a plasticy material, who knows. May be affected by many things; age, wear, exposure to UV or solvents, heat/freezing cycles, ...

daverup 

And, these things are getting old. Who knows who took it apart in the past..

jackbombay

Today I swapped the brifters with some older ultegra units that are SUPER SLR instead of NEW SUPER SLR, and the brakes work much better, and the perception of "lots of spring tension" at the lever is gone.

Classtime 

Ultegra FTW!