V Brake Arm Length

[mickeg]

I ran across an interesting website a couple days ago.  I was looking to buy another V brake and wanted to make sure I got one long enough for clearance around a fender that was over a 57mm wide tire (or tyre).  So, I need a big one. 

This website lists V brake arm lengths.  http://www.gravelbike.com/?p=3298

I have a Shimano XT BR-T780 on my front wheel on my Nomad, the cable between the two arms rubs on the fender, I did not want to get anything shorter than that.  This table lists that brake at 107mm.  The table is not as complete as desired, there are only a few Shimanos listed. 

I am not sure how they measured it.  I measured the length of my BR-T780 from the pivot point where the arm rotates on the frame boss to the cable attachment point, I got 103mm which is shorter than their measurement. 

But I am not going to obsess about how they measured it, I ordered a Tektro 857AL, according to the table that is the longest available at 110mm.

So, if you are building up a bike and want to get a V brake that is a bit longer than the minimum needed to clear a fender, this list might give you some help.  But, considering my measurement that was inconsistent with their listed length, you might want to add some contingency.

[Bill C]

if you need longer i have been looking at these at 125mm arm length,  http://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p2055119.m570.l1313.TR0.TRC0.H0.Xpatent+v+brake.TRS0&_nkw=patent+v+brake&_sacat=0 you can use them in a 26" frame to run 700c wheels using the 26" v bosses  not shimano though 

[John Saxby]

That's a very helpful link, Bill -- thanks.

A recent thread on crazyguy wondered if 26" rims & tires would become obsolete, with the few fashion for 650B and 29er tires.

This was my take on my situation: <i>If in the future I couldn't get quality 26 x 1.6 or 1.75 tires, I reckon I could fit 650B rims & tires to my Raven. The tires would easily fit within the VO 650B x 52mm alloy fenders I now have. The only mechanical tweak I'd require would be a set of V-brakes with a vertical adjustment slot that's about 1.5 cm longer than the one on my current garden-variety Deore V-brakes. I think I'm a few mm short of the vertical adjustment needed to allow me to fit 650B rims on my Raven.</i>

The V-brake arms in your link appear to have the necessary range of adjustment (though it's hard to tell from the photo), and I have no particular attachment to Deore hardware.

[Bill C]

Hi John
if i read the advert right you can use them with 26" or 700C wheels so 650 should go in the middle(ish) of the adjustment slot.
not sure how they'd be with 26" rims as the extra 15mm leverage might be scary the first time you used them on the front of a bike 
only 2 reason i haven't bought a set one is none in silver    ( just finished striping and polishing the anodising from an xtr 960 crankset, so I'm all polished out )
the other is customs and the P.O handling charge

in the quest for all things "Shiny" and staying on topic anyone know the arm length of shimano dxr v brakes
love the look of them
also any reason they are sold as rear only? as all the pics i've seen appear to have the pads set up for a front brake
and i can't think of any reason you can't just flip the pads for front or rear

[mickeg]

A QUICK UPDATE AND SOME PHOTOS:

I installed the Tektro 857AL on the rear on my Nomad, it has 110mm of clearance between the center of the brake pivot points on the frame and the cable.  I previously used a cantilever brake on the rear, but I had some brake squeal that I never could get rid of so I decided to try a V brake.  I still have the Shimano BR-T780 on the front which has 103mm of clearance between the brake pivot point and the cable attachment, and it rubs on my fender.  I was hoping that switching to the V brake on the rear would make the squeal go away.  It does not, but otherwise, the brake seems to work fine.

I attached four photos, the first two are of the Tektro 857AL on the rear, it is apparent that there is plenty of clearance between the brake cable and the fender.  The third and fourth photos are the Shimano BR-T-780 on the front where you can see that the cable and part of the brake rubs on the fender because there is insufficient clearance.  (Unfortunately, the first photo, the camera auto-focused on the ground, not the brake, but the focus is good enough that you can still see lots of clearance between the cable and fender.)

If you are curious about that weird round thing on each brake instead of a brake noodle, I am using normal cantilever type brake levers and they pull a short amount of cable, too short for the V brake.  Thus, I used travel agents that convert the cable pull to work with V brakes.  If you have never heard of them before, there is more info here.
http://problemsolversbike.com/products/travel_agents/

I am going to order another Tektro 857AL to put on the front to fix that rubbing problem.