RubeRad

this hardrock is 88 at least I'm sure

Bill Kapaun

It's a Rockhopper in your pic.
87-89 had U brakes which this doesn't. Wrong color to be earlier.
IF it has original Shimano bits, they'll have a 2 letter date code. YM with. year A starting in 1976 and repeating every 26 years. Month is A-L.

This has 93 & newer. You might be able to ID from commanalities such as cassette & crank brand/tooth count etc.
https://www.bikepedia.com/Quickbike/...spx?item=42395

oldbobcat

V-brake pads come with a stack of washers--one or two thin reinforcing washers, two concave-faced, two convex-faced, and fat and a skinny spacing washers. The concave and convex washers are to be mated for aligning the pads. For widely spaced posts, put the fat washers on the inside of the caliper, skinny washers on the outside. For narrowly spaced posts, put the skinny washers on the inside, fat washers on the outside. Except for swapping the fat and skinny washers, the order of the washers should never be changed. In 12 years of pro wrenching I have never come across a bike where this system didn't work. I have come across dozens of bikes where previous "mechanics" screwed this up.

wesmamyke

Came across a fork with a similar problem of very wide spacing. The only solution in the end was a wide rim, rhyno lite was the bare minimum at just under 30mm I think. You could rig it with the extra long threaded post kool stop eagle claw pads and a ton of spacers. I hated how rigged and kludgy it looked though.

I have a bike with extremely wide rims that has the opposite problem, can't set most brakes wide enough. The solution was STX v-brakes, as they take smooth post canti pads, you can slide them in/out about as far as you need.

RubeRad

I meant 88mm spacing
also I meant rockhopper
the frame and some bits were a dumpster find, so I don't have most of those original bits to know much, but color scheme probably determines it

cyccommute 

I’ve done this conversion on many bikes from many different eras. My personal bikes have been Specialized for many years and I don’t recall ever having any issues with doing the conversion. I don’t bother with measuring and just bolt up the brakes.

That said, I can see some issues with the picture above. Ditch the boot. You don’t need it and it’s just interfering with the cable. It looks like you have the wider spacer on the inside but it looks a bit narrow but that may just be a trick of the photography. One thing you can do to get greater width is to put a washer (or 2) behind the wide spacer. This thread on Bikestackexchage addresses the issue and the following graphic to show how to push the brakes outward. You could move both washers to the inside or even add a 3rd 1mm washer under the spacer and still have enough thread for the brake nut.

ClydeClydeson

cyccommute has the answer in the best detail in this thread. Move the thick concave washer and one or two 1mm flat washers on the pad side of the brake post and this will give you maximum width.

Your picture seems to show that you have no flat washers against the pad, and each 1mm washer will move the top of the arm ~2mm away, so one washer on each pad will move the arms 4mm apart. Two washers on each side will move the arms ~8mm further apart at the top.

RubeRad

Thx cycco

Any best-practice guidance on what angle you want the V-brake arms at for nominal-->ideal power/modulation geometry? Should I aim for the arms to be nearly parallel at rest or at rim contact?

Bill Kapaun

I think the eyeball is the best judge.
Some brake tracks are angled.
You want the geometry as such that the pad doesn't want to move toward/away from the axle under hard braking.
I run my pads very close to the rim.

cyccommute 

What Bill Kapaun said. Just eyeball.

oldbobcat

When aligning the pads just squeeze them against the rim and adjust to fully contact against the machined surface. Too high, they'll hit the tire. Too low, they'll hook over the edge as they wear out. Use a shim at the rear of the pad to get the proper toe-in. A thick rubber band, a match book cover, or the cardboard packaging the pads came in all make a decent shim. Then center the pads using the return spring tension screws. You want the pads to hit the rim simultaneously. You want cable tension loose enough so you can easily grab a handful of lever for maximum power, tight enough so the levers don't bottom out.

RubeRad

yeah, I got all that, my question is what angles do I want the v-brake arms to be when I put the pads against the rim with the shim. I'm guessing, given how bad the angles are now, I just need to move all the washers inside and be content with where that puts the arms.

ClydeClydeson

You want the arms to be close to parallel, but it will never be perfectly so, even on more modern bikes. Get 'em as god as they will go and try it out. I bet you'll be happy with how they work.

cyccommute 

Sorry. Didn’t understand the question. It’s not something that comes up a lot. The arms should be mostly vertical but they don’t have to be perfectly so. I think you’ll find that the arms will move outward so that they are vertical enough with a couple of spacers. You might also consider a different brake. Geometries change a lot from brand to brand.

RubeRad

Yeah geometry comes up a lot more wrt cantilever setup. I guess that's one reason V-brakes basically took over from cantis, they're more idiot-proof to set up (but they didn't count on this idiot!)

cyccommute 

That’s a large part of it. Much less can go wrong.

RubeRad

OK to resurrect this problem, it turns out on closer inspection, the rim is nowhere near centered in the frame between the seatstays. I can't tell how much is because of the gigantic NDS washer in the axle pushing the wheel to the right, vs if the frame is bent

RubeRad

In that 2nd pic I swear the wheel looks like it's at a different angle than the top tube. I tried to have it aligned with the grid pattern of the shop rug. For now we're gonna try going with uneven washer stacks. But if I were to take a 2x4 to the frame, should I bend the right or left side in or out?

Geepig

Um, I would get the string out for a check for frame alignment first

If the frame is true the solution may be as simple as redishing the wheel.

If the frame is not true the solution may be as simple as redishing the wheel - some frames are bent in awkward, complicated ways. One of my bikes has a complicated bend, but since it is an old folder I decided to leave well alone.



This frame has a complex bend at the rear that I do not feel inclined to resolve - hence the angle on the rear brake calipers. I have since dished the wheel more, and while the bend is visible if you stand in front of the bike it actually rides well.

RubeRad

any good links on string-check for frame alignment? From Sheldon maybe?

I'm convinced the wheel looks diagonal to the top tube (which would mean the frame is misaligned), so redishing wouldn't fix it..

Even so, we're going forward with different washer stacks, and the brake arms seem to be in decent positions, and pad contact to the rim seems decent, and as off-center as it is, the tire is not rubbing, so maybe we're just ok. We should name the bike Mr Krabs though.

cyccommute 

Honestly there should be no need for any kind of washer on the unless it is part of the bearing lock nut system. If the hub is too narrow for the frame, you can probably just squish the frame down to the hub or, better yet, get the proper wheel for the frame.

As for checking the frame, damn, I just spread and checked two frames this week and forgot to take pictures. Stupid me. I had to go out and fake it.

Attach a long string to one of the dropouts. It doesn’t matter where as long as you attach at the same point on both sides.


Run the string up the bike, loop it around the head tube and take it back to a dropout. Make it secure to the bike.



Should look like this



Measure from the seat tube to the string on one side (the distance doesn’t matter). You can use a caliper, a tape measure or even a stick. Just note how far the seat tube is away from the string.



Measure the other side. A good frame will be within 1mm. This one is 0.1mm.



If your bike is too narrow or too wide for your hub, you can also cold set it if it is steel.DO NOT DO THIS TO ALUMINUM!!!!

You can make a spreading tool from a 3”x12” piece of all-thread and a few nuts and bolts. You can also make a drop out aligning tool from some nuts and bolts. It helps align things properly after bending the frame.




A 9/16” wrench is used on the inside so that the frame can be spread. This is a really bad picture but you can see how the nuts and washers are used. I turned the tool with a 5/8” wrench on the handle and just use the 9/16” to stabilize it. Spread the frame, remove the tool, measure, spread so more. You want the same width as your hub. If you over spread, you can use the tool to make minor adjustments inward.




Once spread, the dropouts may be out of alignment. Use the other nuts and bolts to check the alignment. The two bolt heads should align perfectly. If not use the alignment tool to make corrections.




It’s relatively easy to do. Just make small adjustments until you get the desired result.

RubeRad

thx, I'll give that a try, see how the string measurements come out.

When I say 'washer', I mean the wheel/axle has like a half-inch washer/bushing/whatever on the NDS, you can see it in the pic above, just below the edge of the dustpan. The wheel fits easily into the dropouts, they're not too narrow, and I don't see any significant dropout flexing when I close the QR, so I don't think the dropouts are too wide.

cyccommute 

Check the dish. If you don’t have a dishing tool, just flip the wheel around in the dropout and ensure that it is centered. Before you do anything, make sure that the wheel is as far back in the dropouts as possible on both sides, just to be sure that not the problem.

From the picture, it looks like it might be overdished. The tension on the driveside is too tight which pulls the rim that direction. It’s not difficult to correct. Go around the wheel and loosen the spokes on the driveside a quarter of a turn without touching the nondriveside spokes. Check the dish after one pass. If it isn’t right, do it again. Keep checking the dish until the wheel is properly centered.

RubeRad

at some point the NDS spokes should be tightened though, right?

cyccommute 

They may not need it. You might be able to pull it back by tightening the NDS but you might have to over tighten those spokes and risk rounding the nipples. That’s why I suggest working on the drive side and taking some tension off. If the spokes on the NDS feel loose after you are back in dish, tighten all the spokes, and check dish afterwards. Then you can make minor adjustments as needed.