Re: [CR] Who has trouble stopping with vintage sidepulls?

(Example: Production Builders:Frejus)

In-Reply-To: <A1370A275A064D648680E850E51B5BB5@AD.UCSD.EDU>
References:
Date: Tue, 20 Jan 2009 18:15:46 -0800
From: "Kurt Sperry" <haxixe@gmail.com>
Cc: <classicrendezvous@bikelist.org>
Subject: Re: [CR] Who has trouble stopping with vintage sidepulls?


Isn't the braking power of a brake design essentially down to:

The rider's hand strength

The mechanical advantage of the levers

The effective mechanical advantage of the brake between each side of its arms' pivots

Any undue flexure in caliper arms or pivot mounts reducing efficiency

Friction in the actuating system

The friction coefficient between brake pad and rim?

So assuming that the cables, housings and runs are similar, the pads themselves are similar (all easily enough changed), the caliper is designed to be sufficiently rigid to do its job and the pivoting arms are properly adjusted so they can rotate without undue friction or play, the only relevant remaining variables I see are the mechanical leverages of the levers and calipers.

You can design for high total mechanical advantage in the system (caliper arms and levers together) and have a brake that is perceived as powerful at the cost of brake rub if there is any out of trueness in the rim as the pad travel is proportionately short or you can design a brake system with lower total mechanical advantage that will be more forgiving of an out of true rim. Every thing else- aero or traditional cable routing style, any QR mechanism for wheel removal or allowance for a bent rim, aesthetics like finish and detail engineering like ease of adjustment and set-up shouldn't affect braking power.

Thus I expect any significant advances in braking power since the '50s to have been either down to lower friction cables/housings, better brake friction pads/rims or simply changes in the lever ratio compromises chosen. Thus I'd fully expect any reasonably well engineered '50s vintage caliper brake with modern pads and cables and rims (assuming those are better) and an equivalent total leverage ratio to squeeze the rims and brake just as well as the latest and greatest designs. It would have been simple enough to change the geometry of the brake systems to give "modern" leverage ratios 50 years ago, so I assume that approach was looked at then and if not adopted, it was simply because a different compromise was deemed advantageous overall. Archimedes pretty much had it all sussed.

And I'm not seeing modern "dual pivots" from a mechanical standpoint as anything more than repackaged center pulls with simpler cable runs and perhaps different leverage compromises.

I'd have trouble calling any brake system where the rider can lock either wheel at will- like I can with, well just about any well set-up caliper brake I've ever tried- underpowered. Assuming enough usable braking torque is available to bring the wheels controllably to the point of lock up, everything else could surely just as easily be called personal preference.

Kurt Sperry Bellingham, Washington USA

2009/1/20 Peter Brueggeman <4peebee@peterbrueggeman.com>:
> Mitch Harris asks "... if anyone has trouble stopping with vintage single
> pivot sidepulls..."For context, I ride hills and mountains and have used SPs
> and CPs and cantilevers and disc brakes. Using SPs from Campagnolo,
> Weinmann, Modolo, Galli, GB, Lytaloy, Sun, Gipiemme, and Beborex, along with
> good brake pads,I've had no problems with properly adjusted SP brakes. I've
> had issues with brake levers, specifically leverage (hand fatigue) or reach,
> but not the brake calipers.Peter..........
> Peter Brueggeman
> La Jolla California USA
> 4peebee(at)peterbrueggeman.com