Niloc

So I haven't posted on this forum for ages, but I did a fix on my bike that I just have to share. It's been done before, but I just wanted to testify that in my case it worked really well.

I have a Bianchi Reparto Corse lugged steel cross bike from I believe about 1995. It's my baby and my go-to daily ride, but I don't actually race it. I love the bike and have it set up just right for me, but one thing that has always bothered me is how the fork chattered and even bounced around under heavy braking, like say stopping at the bottom of a steep hill. I tried everything to get the cantis (Ritchey WCS) adjusted: toe-in, new pads, raised the yoke - nothing worked. I was beginning to think my beloved bike had a fatal flaw, that that Deddeciai steel fork was just a little too slender for the load. I mean it was downright scary to watch the front hub bounce around while braking to a stop, and the squealing was just embarrassing.

I talked to a top mechanic at a LBS and he said they stopped carrying Volpes and other Bianchi XC bikes because this problem was endemic, they had a lot of complaints and Bianchi wouldn't do anything about it. He said the one thing that worked was fork mounted cable stop, because it limited the action of the fork flexing on the brake cable tension. He sold me a $6 hanger but when on my bike b/c the of the position of the fork crown hole and the bottom flange of the headset I was going to have to use a lot of spacer washers and end up with the cable stop way out in front of the canti arms and it just seemed kludgy.

I did some research and this article does a great job of explaining the fork flex issue.

https://velonews.competitor.com/2009/...o-cross_101807

Anyways I found a pair of old mini-V brakes at another LBS for $5 so I decided to try them out, and wow problem solved. I can endo the bike without so much as a peep from the brakes. Chatter? - Zero.

So I didn't use a travel agent or a V-brake compatible lever and I feel that the clearance and feel is decent. I'm using old non-aero brake levers b/c I have moustache bars with bar end shifters. I estimate that my levers only pull about 1 cm of cable.

My rim is a Mavic Open Pro and it is not perfect. I discovered that it's not centered over the hub and that it has a couple minor wobbles. The first issue I was able to deal with by playing with the brake arm rebound screws to get the pads on both sides the same distance from the rims, and the second hasn't caused any problems. I did get (for free from the first LBS) and pulley device with a cable barrel adjuster as a noodle replacement - this is key b/c there's no way to adjust the cable tension otherwise. I set it so that when I screw it all the way in (loosening tension) I can just remove the noodle thingy from the brake to remove the wheel. For riding I have it set so that I have a good 3mm of rim clearance on both sides and I still get plenty of braking power. I realize that for cross that may not be enough on a muddy course, but I could probably get another mm or two and still get OK braking.

I'm keeping my rear canti as I see no reason to swap it out and honestly the way it's set up the feel between the two brakes is remarkably similar. Maybe b/c the rear brake has a longer cable run and the pads are worn and a long way from the rim.

So one vote for mini-Vs. I was ready to try a long reach caliper just to see if it would work, but I'm happy to be able the use the fork posts for something!

meanwhile

Mini Vs are supposed to be used without a Travel Agent, afaik. Congratulations!

OTHB

Hi Niloc,

I've been struggling with the same problem. Pads properly toed in, still get the shudder. Thinking about getting the mini v's, and would like to get that pulley with the cable barrel adjusted. Do you have a product name, or manufacturer, was going to try and hunt one down on the web b/c my LBS gave me a blank stare when I showed them your post and asked for the same thing.

Thanks much!

SpongeDad

Hey - could you post a picture of your frame? I refurbished an old Bianchi cross frame, but have never been able to identify the model. Mine has a threaded headset, lugs and mtb brake bosses front and back, but there is no built in cable hanger for the rear. Also, the seat clamp is part of the seat tube.

fwiw - I don't have shudder problems when I run the cantis at low hanger height / tight tolerances. My wheels are really true and centered so that helps.

ratell

My shudder problems went away when I switched from Tektro Oryx's to CR720's.

flargle

I still think a travel agent is a good idea for cross, and by my kitchen scale only adds 16g over a noodle.

Craig admits, though, that while most privateer racers in wetter climates do have to concern themselves with pad clearance in the mud, he not only often has the luxury of a pit bike but also a support mechanic to take care of both machines.

Even so, he feels it makes more sense to choose your equipment based on the rule rather than the exception, and in many cases - at least in the US - that rule is dry and fast.

"I've got a guy in the pits so if my brakes are jammed up with mud I'll stop and get my other bike and ride that for a couple of laps and then I'll have a new bike so it'll be a non-issue," he said. "[Fort Collins] has been the first muddy race of the year and when you're riding a motorcycle on a race track, you're either on the brakes or on the gas and when you're on your bike you should be doing the same thing.

Like you should be accelerating until you need to slow down at your braking point and with those brakes you can actually achieve that so I'm fired up that Lance [Larrabee, at TRP USA] was able to bring that to market. They're awesome."

https://www.cyclingnews.com/features/...cx-advanced-sl

Andy_K 

There are several available. The Tektro RX5 is an representative example.

The basic idea is really pretty simple. V-brakes traditionally require longer cable pull because otherwise they have too much mechanical advantage. Mechanical advantage is directly proportional to braking power, but inversly proportional to how far the brake moves for a given amount of cable pull. If you have high mechanical advantage and short cable pull (as with STI levers), your lever is likely to bottom out before you've applied the force you wanted to the brake (obviously depending to some extent on how close to the rim you set up the brake).

As the arm length on the V-brake goes down, its mechanical advantage goes down, meaning it can be used with less cable pull. The trade-off is that as the arm length goes down, so does the braking power. For reference, the Tektro RX5 has an 85mm arm, where as the Shimano Deore M590 V-brake has a 107mm arm.

Even with the shorter arm, mini-V's have a lot of mechanical advantage, and so even though they can be made to work with STI levers, you still need to set them up pretty close to the rim.

Incidentally, I believe the reason they fix the brake shutter problem is that the cable pull on the brake isn't dependent on the positional relation of the fork to the lever, so braking power isn't reduced as the fork flexes.

pacificaslim

I agree with your explanation. And I use the RX-5 brakes with campy ergo levers (no travel agent) on my Ritchey 'cross bike with wcs carbon fork and there is no shutter at all. The brake pads are pretty close to the rim but the brakes have good feel and good power, too.