Noonievut

I’m using Tektro mini v brakes (90mm) with 105 11sp brifters and while they do work and provide enough stopping power and okay modulation, they need to be set up with the pads pretty close to the rims to ensure the levers do not bottom out at the handlebars. I also have more than 10mm pad clearance between the tire and brake cable.

Would going to a shorter brake arm (considering the TRP cx8.4 - 84mm) mean that I can give the pads a bit more space (wheels won’t stay true forever)? If so, is that a function of arm length directly related to cable pull?

Also, with this specific TRP brake I’ve read it’s meant for SRAM/Campy levers, but I’m assuming a recent Shimano 11sp lever would be more than fine?

delbiker1 

I am not knowledgeable on this subject, but a quick google search shows many people have the same issue. Quite a few "fixes" are also listed. It appears that both are short pull, but are subject to specific set up needs. I am quite sure others will chime in with more definitive answers that might help, though info on the specific model, maybe pictures of the set up, would be helpful. Assuming parts are compatible is usually not a good idea.

FastJake

Yes, shorter arms means less mechanical advantage. This will give you less "braking power" but you'll be able to set the pads further away.

I've only used mini-Vs once but on that bike I had a strange issue where the levers would bottom out no matter what. It turns out the brake posts were flexing so much I couldn't get enough braking force. Adding "brake boosters" fixed this problem. I don't think the mini-Vs were the problem, but I just mention it because it could be the issue with your setup. This was on a very light full carbon cyclocross frame/fork.

Noonievut

The brakes stop the bike no problem. It’s clearance I’m interested in gaining. But I do have inline barrel adjusters so I can tweak them to see if I get it ideal (a good shop set these up, so I’m assuming they’re already optimal)

delbiker1 

I am not being critical, I just dislike assuming anything regarding component set up for optimal performance. Your OP suggests you do not believe your brakes achieve that, it is a worthwhile pursuit, IMO.

Dave Mayer

FastJake got it right: the longer the caliper arms, the more mechanical advantage, at the expense of pad travel. The longer the calipers, the stronger the braking, but you have to run the pads closer to the rims. If you've run standard V-brake calipers (100mm long+) with road levers, you'll know that the braking power is very strong, but you get little modulation, and you have to run the pads unacceptably close to the rims.

I currently run a 'cross bike with TRP 8.4's. They are the best mechanical rim brakes I've ever used. They are very powerful and stiff, and feature first-class hardware. I've also run Tektro Mini-V's, which have an arm length of <80mm, and they are perhaps an even better tradeoff between power and pad travel.

Noonievut

Very helpful, thanks!

Russ Roth

Maybe the trp are an exception but I've yet to find a V-brake/road lever combo that I considered acceptable. Either pad too close or too much pull to get contact and that's on bikes that came factory with the setup. Although I'm not a big canti fan, canti brakes on a cross or touring bike are the superior of the two options hands down. A little more money since you'll have to order a couple of pieces to make them work, but ease of wheel removal with what is fairly good stopping power makes the extra effort to set them up right worth it to me. Did this for my kid's bike and my tandem, do appreciate the stopping better.

Andrew R Stewart 

I'm with Russ here. We have set up quite a few bikes (some repairs, some new) with short pull drop levers and short length linear brakes. When all is new and true the set up works sort of well most times. but as wear, contamination and rim condition evolves with use the real life performance often falls off. Sometimes to the complaint of the riders. The range of good set up is narrow and I never liked the really mushy lever pull.

My choice might include Travel Agents if I can't get a good set up with cantis. Andy

Noonievut

If I swapped to the TRP cx8.4 can I re-use the cable (generally speaking)? Everything is new, and while I may just take it to the shop I wanted to get an idea whether this is relatively easy diy (my skills are okay, and I replaced calipers once on a road bike but can’t recall the details).

FastJake

Probably. V-brake anchor bolts tend not to crush and mangle the cable like other types of brakes/anchor bolts. Just be careful with the cable and hopefully it wasn't installed by a ham fist.

Re-use the noodle (90 degree metal curved part) if it looks identical to the new one. It can be iffy trying to feed a used cable through one of those. The cable tends to unravel.

Noonievut

FastJake thanks! - if I go 6mm shorter arms any idea if that means I get the same pull at the lever but now the pads are x mm further away from the rim? As I mentioned above, the power is more than adequate, I’m definitely not bottoming out the lever, and modulation okay, this is about solving pad clearance so if this change means I can run the pads only a hair further away from the rim it wouldn’t be worth it, but 2-3mm might be.

FastJake

You'd have to do the geometry yourself, I'm sure it's not a 1:1 ratio. But yes, shorter arms mean you can set the pads further away from the rim without risking bottoming out. This is because the arms move more for each millimeter of lever travel. The brakes should feel firmer, and you will have to squeeze them a bit harder to get the same braking force.

This article is about traditional cantilever brakes, but the mechanical advantage principles apply: https://www.sheldonbrown.com/cantilever-geometry.html

Freerojo

Get these https://bike.shimano.com/en-EU/produ...0/SM-CB90.html To get the brakes as close to the rim as needed you may not have enough to release the noodle to open the brake. Those in-line adjusters have a lever, one you pop it open, give the barrel a turn or two, now you can release the noodle for the pads that have to be set real close to the rims. I did this.

Noonievut

I thought I would share a photo of the clearance at the rim. Also included one showing the large clearance for the tire. Again, I would get something like the TRP cx8.4 if it means that fraction of rim clearance grows to the point where if the wheel is a bit untrue I don’t get pad rub, and ease of removing the needle to remove a wheel. Thanks

FastJake

I should clarify my earlier posts by saying that I don't know how much extra pad clearance you'll get with those shorter brakes. It will be "some", at least in theory. But will it be enough to notice and make a difference? I have no idea.

I would probably still use mini-Vs but the tires I ride these days are too wide for them. So it's regular V-brakes and cantilevers for me.