sdn40

So I was browsing at my LBS and there is a 80's bike (Mangusta road bike) with some chrome 105 calipers and they were smaller than the usual and awesome IMO. Loved the smaller scale and didn't know there were different sizes. Had the same Shimano lettering and 105 script which was smaller as well. Can someone enlighten me on these and if they had a specific part number ? Should have snapped a pic but didn't

Lovenutz

Hmm something like these short reach BR-1050 calipers.?

sdn40

LOL - I can't tell unless a 'standard' size caliper is next to it - but yes - that's what they looked like. Don't recall if they had the SLR designation but it's not important. It caught me by surprise because I thought all calipers were roughly the same size. In a line of 15 or so used bikes - the one bike had the smaller calipers and stood out to me. I liked the smaller scale

dddd

In the days before dual-pivot calipers, and before many roadies were wanting to use wider tires, designing the fork and rear brake bridge for short-reaching calipers was an effective way to boost braking performance.
First, by simply increasing leverage, and secondly by shortening the load path along which bending-force leverage was being generated and fed longitudinally into the pivot, more power and less pivot friction, respectively, was the result.


Dual-pivot calipers helped maintain performance when larger tire and/or fender clearance was needed, but even today we see the latest high-end calipers striving to cut a smaller profile for weight and aero considerations.


So as long as the calipers still give enough clearance for the tires (and possibly fenders) that we want to use, and have enough reach for the frame/fork/wheels that we want to use, I'd say the smaller the better, since it's the frame and fork that determine the max possible clearance from the start.

old's'cool

dddd, all of the concepts you have elucidated in this forum have made perfect sense to me, once I have understood them.
The above load path argument is so far escaping my comprehension , so I wonder if you'd be kind enough to take another crack at explaining it?

noglider 

I think he is saying that a longer arm has more material to flex, so braking energy is wasted by flexing the arm rather than applying it to the pad.

T-Mar

Agreed. All other things being equal, longer arms = less leverage + more flex

SJX426 

Its about where the fulcrum is on a lever. If you are old enough to remember see saws (sp?) some of them were adjustable to compensate for weight difference between riders at each end. same thing, it is all about mechanical advantage.

sdn40

I'm sure this is old hat to most here - but your reaction was the same as mine. I'm guessing it may be harder to put bigger tires on too, but I loved the look

dddd

I was referring to the brake pad force generating side-load and off-axis twisting to the caliper pivot, which causes friction in the pivot's free rotation.
The shorter the arm (i.e. the shorter the load path from the pad to the pivot), the less friction results in the caliper pivot and the more responsive the brakes act in response to changes in force at the brake lever.


I have one bike that I race where the front caliper bolts to a thin metal plate instead of a forging or box structure, so I had to secure cords from the pads to the fork legs to control forward flexing of the mounting plate.
I was really surprised how much improvement resulted from relieving the pivots of the kind of twisting forces that cause friction in the caliper's pivots, since the front brake feels so much more direct now, with most of the friction removed.
This is definitely one of the reasons why people like the feel of disc brakes, since there is no leverage acting to force pivot bushings out of plane with their axis, and is why Shimano and DiaCompe have used ball bearings at the pivots of their best calipers.


Here's a picture of the front caliper, showing the support cords that feed braking loads in a path that is in line with the path of the rim instead of at 90 degrees to it. These pivots are still tight after 21 years of racing this bike on and off-road, while the rear caliper's pivots are in a totally loose, wasted condition with vague feeling at the lever despite new premium compressionless cabling.

old's'cool

Ah yes, perfectly clear now!