Plainsman

So I probably need long reach calipers, but short reach R7000 is what I have. You can see that the pads are right at the tip top of the brake track. Is there any issue running this way? Ideally I would center them on the brake track, but this is all I’ve got. Right up to the hook. Pics are of (1), without brake engaged, (2) with lever fully engaged. Also noticed that on the R7000, the non-drive side front pad sits just slightly lower than the drive side pad. TIA!!!

spelger

are these old wheels? the brake track looks like a channel, as if from severe wear. i have never seen that in a rim brake surface before.

ThermionicScott 

Looks fine to me, for now. One caution is that I would spin the wheel few times to make sure there isn't a radial dip where the brake pad could contact above the rim. The other thing to note is that as the brake pads wear, they will aim higher (toward the tire.)

Some of those offset brake pad holders wouldn't be a bad idea, if you're not willing to go for longer reach brakes.

gkamieneski

I don’t see an issue with your setup, and I don’t see much brake wear let alone a worn in “channel”.

Jeff Wills

1. As the brake pads wear, they will pivot upwards and cut into the sidewall of the tire. This will result in a blowout. Maybe not soon, but it will happen. (I did this once, thanks to a crappy brake pad adjustment. Not a fun time.)
2. The rim is very worn. Much more wear and the rim’s flange will break off. (I did this once. The tire and rim exploded on a rainy day. Even less fun waiting for my wife to come rescue me.)

maddog34

that rim is worn out or so close to dead it's wheezing.... next thing that happens is a crack.... and it will bend easily if you hit a curb lip or a pothole... the brake kinda pulses just before the crack opens...at least that's what i recall from the One time i let that happen....

the brake looks to be set up too close to that side of the rim when it's released... is the caliper not centered correctly? does it drag at any point in a revolution?

But that concave brake track is a problem waiting for an inopportune moment to manifest... they usually fail during heavy braking...
The curvature of the pad shows it clearly, in image #3.

Eric F 

I’m not seeing the significant wear on the brake track that others have commented on. It’s looks to me like the original factory finish is still
pretty intact.

maddog34

it may be a camera angle effect, but if you compare the gap at the bottom of the released pad to the top of the pad in image #3, the pad's top is even or hidden, and a 1mm to 1.5mm gap is apparent at the bottom of the pad... that lip at the top of the brake track shouldn't be that prominent, or even there, if what you say is true.
and spinning the rim while sanding it can leave similar parallel grooves..

it never hurts to point out possible trouble... and that brake track could certainly be trouble.
it won't suddenly fold up, but it will ruin a nice ride.

79pmooney

Plainsman, are we looking at a concave (ie very worn) brake channel or are we looking at a flat new, or near new rim sidewall and a brake shoe that is simply not hitting it square? (I thought it looks the latter; new with a brake shoe not hitting it squarely but others above think the former.)

If the former - address it! You do not want to be riding it when the sidewall fails Now, if the rim is good (simple check - lay a credit card edge vertically along the brake track at the rim top. Can you see a gap in the middle of the brake track with the card hitting at the top and bottom?) you need to be aware that the contact point on the brake shoe will move up as the pad wears unevenly to match the rim. Watch it! If it creeps above the rim do something! You have lots of options. A real solution is putting on deeper reach brakes. Using dropped brake shoe holders. You can simply file the top of the pads down. (You'll have to keep doing that as the shoe wears more but as long as you keep it no higher than the rim top, you are good.)

If the pad ever hits your tire, the odds are good that tire is dead. (You may get no audio or otherwise warning that it is happening. And it may not fail then.) You may well not be able to jury rig it enough to get home. (But carry a LOT of dollar bills if you do not have a backup plan like wife who can be called. Or be prepared to walk.)

jccaclimber

1. I'd ride it as-is, though it does look like the brake pad might end up being too high after it's worn halfway through. I would keep an eye on it every now and then, like one should any bike part, to make sure that the brake pad is not wearing incompletely and leaving a bit hanging over at the top to ruin the tire. It'll take a lot of braking for that to happen unless you ride in the rain a lot, and you should see it coming well in time if you're paying attention. If that happens, you either sand the extra bit off, or it's time to get pads.
2. I think those grooves look far too uniform to be brake track wear or sanding marks. I do see what looks like a less than ideal match at the bottom of the brake track, but it looks like a fairly new rim from this perspective. A straight-edge across the brake track would show for sure.
3. I'm not worried about the angle between the pad and rim, that will wear in over time.

79pmooney

When a sidewall fails, what happens is that a perhaps 10" piece of the outer sidewall and tire hook will blow off violently, often still attached at one of the ends of that strip. When that happens, that jagged piece is like the sword on a chariot wheel, cutting any flesh (your calf), carbon fiber (your chainstay or fork) in its way. Now you might get lucky and just have it blow off in the garage while you are doing other things. Steel bike, no more than a little paint.

Hence my question about what we are looking at in my post above.

maddog34

OUCHY! I never let mine get that bad... it got a 3/4" long crack, and then replaced... it was on my 930 Road Trek, with a zillion miles of use... i Clean mybikes frequently.. the cleaning is also an in-depth inspection

i've seen another rim crack...it was about 1" long, a low pressure MTB rim, in that case....... and my parts collection gathering has brought a few into my shop that were clearly marked as "cracked"

neither one blew out, luckily...

i HAVE had a tire blow out for no apparent reason... the tire bead failed.. scared the dickens out of me...and i once over-inflated a sew-up on my Mitzutani superLite,, it blew right next to my left ear... the station had installed a new, BIG Compressor... the normal air-up time became dramatically shorter !... the new compressor was set by the installer to 150 lbs... they turned it down to 125lb. after my blowout..

erring to the side of caution is the best path, IMO...

Plainsman

This is actually a brand new wheelset. Less than 50 miles on it. Brake tracks are not concave, that is an illusion from the photo. Tracks are flat and flush. I’ve looked up brake pad extenders and heard mixed reviews. Some say they reduce braking force. Is there a reputable mfgr? The brake set could be replaced for $100 or so, just hoping to avoid that. I only need to pick up a few millimeters, and wish there was simply an aftermarket brake pad holder that would get the pads just a tad lower.

zandoval 

Rats... These look so good I think I better go adjust mine...

TiHabanero

The pad adjustment is spot on, and looks much like my own setup plus thousands of others I have done for customers in the past. FWIW concave brake tracks were a thing back when. I remember Araya had a rim with concave tracks, I don't recall the model, but it definitely had 'em.

Plainsman

Thanks, and had no idea there used to actually be concave tracks. I knew Zinn liked to see a few mm from the top of the track, and since I don’t quite have that, that was my primary concern.

Plainsman

It is a camera effect, there isn’t really any lip at the top of the track or concavity going on- the track is smooth and flush (these are new wheels, albeit relatively inexpensive ones. I have wrestled with these calipers as far as having the reach equal on each side. The right will go lower than the left by a mm or two, not sure why. I do run my pads tight because I like a light touch on the levers, but the wheel does spin freely as shown, without rubbing. I would personally feel a little more comfortable though having a little more track visible at the top. Does anyone have a good recommendation for extenders?

thumpism

If the calipers have sufficient material at the bottom of the arms you could file the slots longer to locate the pads lower down on the rim. I've done that.

grumpus

The problem is that in a dual pivot caliper one of the arms rises as the pads wear, and you don't have much to play with from the start. The blocks will wear so they're hanging over the edge of the rim and eventually cut into the tyres, unless you watch them and take preventive measures - I use a coarse file for smoothing and shaping brake blocks.

sweeks

Good to hear that the rims are new... it *did* sort of look like they were worn.
My experience with brake track wear is that there is a "thumping" during brake application before the rim actually separates. Rim widening may also occur as a structural failure due to high tire pressure in combination with wide tires on narrow rims.


Radial view of a rear rim with brake track failure in progress. This was really thumping. Probably less from wear than the situation pictured below.



This was a structural failure from wide tires on narrow (Kinetix 406-14) rim. Rear wheel.



A metal straight edge is a good screening tool for brake track wear. A 1mm gap in the center means the end is near! (Ruler slipped during this image...)

Plainsman

I appreciate the images, and I actually have a few sets of older alloy rims so this gives me a good idea of what to look for. Is the general consensus that pad extenders are a safe way too eek out a few more mm? Some of those extenders cost as much as the brake calipers!

sweeks

I have no experience with extenders, but I'm wondering if this is a 700c (BSD 622mm) wheelset that you have on a bike originally set up for 27" (BSD 630mm) wheels.
You can get brakes with longer reach (for example, HERE). It seems to me that if you are vigilant about the proximity of the brake pads to the rim edge as the pads wear, you should be OK.
The longer reach probably has less mechanical advantage, so less effective braking, though that might be compensated for by the optimal choice of brake levers.

AeroGut

I assume the extenders you’re asking about are something like this: https://bdopcycling.com/product/bdop...s-pair-silver/

Given how little extra distance you need, I think they’re a good option. Your leverage is slightly reduced by the longer distance, but I doubt it will be enough that you’ll even notice it. The other thing to be careful of is to make sure the pad holder is very tight in the caliper as there can be twisting force if the front or rear of the pad contacts first.

grumpus

If I'm unsure of a tyre's fit or structure I'll use eye and ear protection when inflating it, particularly if I'm using a compressor - once bitten ...

maddog34

the gas station incident was a tubular tire glued to a rim... I don't carry safety glasses or jet muffs on rides... and i won't use insertable ear plugs.. they are not on my list of things to carry along on rides, either.

and the other one was a high pressure clincher that had been aired up two days or more previous to the blowout.

45 years seperate the two events.