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Rim Brake Caliper Return Springs: The softer the better?

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Rim Brake Caliper Return Springs: The softer the better?

Old 09-28-22, 09:18 AM
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karldub
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Rim Brake Caliper Return Springs: The softer the better?

I have many sets of rim brakes and generally have no problem with the stopping power (except for rainy days). My best calipers are a set of Shimano Dura Ace BR-7800 which I use with matching ST-7800 brifters and newly bought Jagwire Compressionless Road Pro brake housing + Jagwire brake cables. One thing that annoys me however is the amount of force I need to use to push the levers in when riding from the hoods. It's not a crazy amount, I just wish it was "softer", more like the feel of a hydraulic disc brake brifter.

From my understanding, the return spring on the caliper needs to be strong enough to push the caliper back into "open" position after letting go of the brake levers. But I'm thinking that should not require a lot of force? My question is, why don't the producers simply make the return spring softer, to require less force to push the lever when riding from the hoods?

Secondly, the Dura Ace 7800 set is a bit old but in good shape. Do newer calipers have a softer feel, more like hydraulic brake levers?
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Old 09-28-22, 09:27 AM
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I can actuate my 7700 calipers from the hoods with one finger. The brakes should already have a "softer" spring, to assist with the SLR braking. I use 7402 levers and don't have a clue about integrated shift/brake levers. Do they have a return spring to assist with any SLR-type function?
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Old 09-28-22, 09:28 AM
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Originally Posted by karldub View Post
From my understanding, the return spring on the caliper needs to be strong enough to push the caliper back into "open" position after letting go of the brake levers. But I'm thinking that should not require a lot of force? My question is, why don't the producers simply make the return spring softer, to require less force to push the lever when riding from the hoods?
1. Because the OEM spring rate is presumably designed to open the brake caliper even if the pivots get a little grimy or corroded?

2. On a cable-actuated brake system, the OEM spring rate has a significant effect on (a) the amount of force required to move the brake caliper from open to the point of contact against the braking surface (e.g., rim), but has only a slight effect on (b) the amount of force required to compress the braking material (e.g., brake shoe) against the braking surface (e.g., rim). Most people have no issue with (a) but feel that (b) requires too much force, especially compared to a hydraulic disc brake. So reducing the OEM return spring rate would not do much for that.
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Old 09-28-22, 10:48 AM
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Just checking, but you have tried to adjust the spring tension with the adjusting screw?

Not many Shimano calipers have this feature.

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Old 09-28-22, 10:57 AM
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Neat feature.
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Old 09-28-22, 11:19 AM
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More modern rim brake calipers do have softer return springs compared to vintage (single pivot) calipers. Compare a modern Campagnolo caliper to an old Record (1980s) model, and this is obvious. The same applies to Shimano. Some of the older brake brands such as Modolo and Gipiemme had absurdly stiff springs, which required a bunch of hand pressure to get some braking. And being single pivot brakes with flexy arms and cheap hardware, there wasn't much braking power to be had at the best of times.

The reason for the stiff springs in the old calipers is the need to overcome friction in the primitive unlined (steel against steel) housings, and the lack of return springs in the brake levers.

Thank goodness for modern dual-pivot brake calipers.
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Old 09-28-22, 01:09 PM
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Originally Posted by KCT1986 View Post
Just checking, but you have tried to adjust the spring tension with the adjusting screw?

Not many Shimano calipers have this feature.


Well actually...

Shimano dual pivot brake calipers have has a caliper return spring adjuster for a long time and on most all their series/grades. No screw but a small plastic block that most here likely think is a low friction pad. The plastic block has a thin (the usual OEM setting) and a thick side. By rotating the block 180* the spring is preloaded more, by the added thickness of the block as it nestles back into the arm's tab. These plastic blocks are one of the first things to lose if the spring is detached from the arm. The spring acts as a catapult and flings the "unseen" block across the room. Andy
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Old 09-28-22, 03:52 PM
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Even the strongest return spring is a trifle, considering the leverage involved and the total force used in braking.

There's also the practical design consideration of the various extraneous forces on arms which depend on the spring to center. These include the tug of the unloaded cable, friction at the pivot, and probably most significant, friction where the spring slides against the stop on the arm.

So, while less MAY be better, I assure you that least isn't.
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Old 09-28-22, 03:55 PM
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Originally Posted by Andrew R Stewart View Post
Well actually...

Shimano dual pivot brake calipers have has a caliper return spring adjuster for a long time and on most all their series/grades. No screw but a small plastic block that most here likely think is a low friction pad. The plastic block has a thin (the usual OEM setting) and a thick side. By rotating the block 180* the spring is preloaded more, by the added thickness of the block as it nestles back into the arm's tab. These plastic blocks are one of the first things to lose if the spring is detached from the arm. The spring acts as a catapult and flings the "unseen" block across the room. Andy
If you’re referring to what Shimano calls the “sleeve,” it’s not true for the BR 7700–the sleeves of which are perfectly cylindrical.
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Old 09-28-22, 04:48 PM
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Depending on the grade of steel used you may be able to bend (or possibly break) the spring to reduce preload, but cable operated rim brakes are never going to feel like hydraulic disc brakes. Shimano made some improvements in the 1980s with dual pivots, lower friction materials, low compression cable housing and helper springs, I don't think anything they've done since to improve cable rim brake feel has been as significant, and I don't suppose any further effort will be put into improving what is effectively obsolete technology.
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Old 09-28-22, 05:08 PM
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Originally Posted by Andrew R Stewart View Post
Well actually...

Shimano dual pivot brake calipers have has a caliper return spring adjuster for a long time and on most all their series/grades. No screw but a small plastic block that most here likely think is a low friction pad. The plastic block has a thin (the usual OEM setting) and a thick side. By rotating the block 180* the spring is preloaded more, by the added thickness of the block as it nestles back into the arm's tab. These plastic blocks are one of the first things to lose if the spring is detached from the arm. The spring acts as a catapult and flings the "unseen" block across the room. Andy
Those rectangular blocks are not that commonly seen. They were only on a few of the late model single pivot calipers and the early dual pivot calipers from back in the 7/8 speed group days.
Newer models had/have the round sleeves and some of series of the DA & Ultegra had the tension screw. Location of the centering screw and the spring tension adjuster varied on some series.
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