rousseau

Can you manually pull your rim over to make it touch your brake pad?

I can. Does that mean I have too much flex, that I should increase the spoke tension? Or is it fairly normal, and there's no such thing as a stiff wheel with no horizontal give?

Bunyanderman

Give the skewer a really good re-clamp, I found that this kills most of the horiz flex.

rpenmanparker 

Unfortunately no matter how high the spoke tension, you can't increase wheel stiffness that way. Only way is more spokes or heavier spokes. Or a stiffer rim itself, but that can be problematic.

Also, it could be loose wheel bearings or skewer.

hueyhoolihan

it all depends on how close my pads are to the rim to begin with.

Jiggle

I have a 32 spoke mountain bike wheel with 2mm straight gauge spokes and I have no trouble pushing it into the brake pads. Yes, the skewers and bearings are tight. I think it's a silly experiment.

rousseau

There's nothing silly or experimental about it. As a heavier rider, I'm having problems with brake rubbing going up hills with a new wheelset, and I'm trying to increase the spoke tension to prevent that from happening. But I'm not sure whether being able to manually pull a rim to the brake pads necessarily means that the rim will flex by that much when under load going up hills.

FBinNY 

As RP said above, stiffer wheels are about more steel (more or thicker spokes or both), not spoke tension. The stiffness is determined by the flex modulus of the material, which is the same regardless of the initial tension.

Consider a scale. If you put 50 pounds on it, it'll move a certain distance and read 50#s (or so). It moves the same distance for 50#s whether it's the only 50#s or an additional 50#s when there's already 100#s on it. Likewise, the rim will deflect proportional to the load, and the amount of deflection is the same, whether the initial tension is high or low.

As to the original question. I like light wheels and usually build much lighter than most members here, using 300g or less tubular rims, and DB spokes as thin as 1.5mm in the center section. Since the wheels are built light I have absolutely no problem flexing them until they touch my brake shoes, but it's no issue.

Wheels undergo very little side load in the real world. We lean into turns so the side loads run from the center of our mass, in a line to the wheel's point of contact on the ground. Since they're within the plane of the bike, there's no (actually very little) side loading. In fact side loading is nearly impossible, though it can be done*, because if there were side loads we'd simply fall over.

*one way to crate a side load, is to lean our bodies into a turn while holding the bike more upright. Another is the rocking action during hard climbs or sprints, but even these aren't enough to deflect a wheel much, even a lightly built wheel.


BTW- the way to avoid incidental brake rub when climbing is to learn to keep the bike more upright. There's no benefit to rocking the bike the way most struggling climbers do. This is very different form the intentional rocking that sprinters do at high cadence.

Soody

With my 32/36 wheels you can push them into the brake pads.

They're Pacenti PL23 on 5800 hubs with DT competition spokes.

I just leave my rear brake pretty open. I hardly ever use the rear brake anyway.

The front one doesn't flex as much/ you can watch it.

rousseau

This could be a process of me discovering what sorts of wheels I can and can't ride. My previous rear wheelset was self-built: 28-spoke Miche Primato Syntesi hubs laced to H Plus Son Archetype rims, shown in this photo:



The wheelset I'm using now is a ten-year-old Campagnolo Scirocco with the G3 spoke pattern on the rear wheel:



Weight-wise they're comparable: 1,851 g for the self-built Syntesi-Archetype wheels, and 1,785 g for the Campagnolo Sciroccos. However, I was feeling sluggish going up hills with the Syntesi-Archetype wheels a while ago, and replacing the bearings fixed that. Maybe I should replace the bearings on the Sciroccos to see if that works? Because I can't positively confirm that they are rubbing against the brakes, I was just assuming that.

I bought the wheelset used, and the seller claimed they'd been taken off a bike years ago and never actually ridden, but the seller could have been lying about that, I suppose.

BoSoxYacht

no, it's normal to be able to do this.

BoSoxYacht

increasing spoke tension won't make the wheel stiffer. End of discussion on that.

Manually pulling the rim to one side is possible on every road bike I've ever seen, so that's not really an accurate way to judge wheel stiffness.

rousseau

That settles that, then. I guess I'll have to look at changing the bearings to see if that helps.

FBinNY 

No harm in checking and relubing the bearings, but don't expect miracles.

Unless there's an obvious source of significant friction almost all climbing "sluggishness" will trace back to engine problems. If it were bearing friction it would be obvious when you spun the wheel in your hand, any less wouldn't be enough to factor. Brake rub is the same. A slight passing rub when the bike is leaned won't add much drag at all, and more would be audible.

redlude97

You dont apply horizontal forces to the wheel like that when climbing, so it doesn't have any bearing on your rubbing IME. Brake rub on hills is also often attributable to frame flex, so it may not be the wheels flexing, even though its a new wheelset. The new wheels may just be wider than your old wheels or the dish may be slightly off. Just open your calipers more, they don't have to be that close

rousseau

Engine problems? I don't really want to admit this. Actually, deep down I know this is probably true. It's still early in the year, so I can't expect to be all that chipper on the climbs.

Thanks for the clarification on how rim rubbing is manifested. When I first put the new wheels on the bike I also had just put new brakes on, and I'd purposely set the brakes tighter, requiring less pull on the brake levers. I'm fairly certain that that resulted in some rub on steeper climbs, because I have felt a difference now that I've loosened the brake setting, allowing for more clearance from the rim.

But in the end I guess I probably have to admit that my legs aren't up to snuff yet.

rousseau

Interesting. I rode a steel frame for years, but just this year got a new (to me) aluminum frame. I wonder if that explains it, partly?

K.Katso

There's some pretty interesting reading here:

Debunking Wheel Stiffness - Slowtwitch.com

BoSoxYacht

I didn't want to say it, but now that it's out there...

Try your old wheels for a ride or two, if you still feel a little sluggish on the climbs, it's a weak motor issue. On the other hand, if the problem goes away, it's probably an issue with the new wheelset.

Jiggle

That's the joke. You can pull any rim into the brake pads with your fingers. Now, if you want to get a tension gauge and get some real numbers, then you're measuring stiffness in a useful way. That's not to say it will explain your rubbing problem on its own. Usually brake pad rubbing is due to a stiff rim paired with thin spokes or low spoke counts. Zipp has a graphic explaining this.

rpenmanparker 

Right, you have to either lighten up the rim or beef up the spokes.

gsa103

I disagree with that statement. My friend and I have both had wheelsets where the bearings were basically shot. They spun reasonably off the bike, but were marked slower on the bike. The description basically matched the OPs symptoms, the bike just felt slow. The spin test can be especially misleading on cheaper heavier wheels becuase the rim & tire will have higher angular momentum making it seem to spin acceptably.

With relatively new and well maintained wheels, the bearing drag doesn't matter. However, the OP is talking about a 10 year wheelset which has likely never been re-greased in its entire lifespan.

goenrdoug

as a big guy, myself ~210 lbs/~5'11", I can relate.

I run a cheap set of 'Aeromax 700' wheels. I think they're basically unbranded Vuelta Corsas. Regardless, at 20/24 & ~2400g, they do the job for me and have been fine for my needs for almost 6000 miles now. In that time I've had two broken spokes and no other problems at all with them. Not bad for $79 (including shipping)

But I digress. I wanted to relate a little story that supports your observations:

Soon after I got into road riding, (I was about 250 lbs at the time) a neighbor (long-time rider) noticed my interest and my cheap wheels and lent me a set of carbon Bontrager wheels. I forget the spoke count or the specific model, but I think it was 20/24. They were much lighter, however. I figured, score! So, I got myself some cork pads and tried them out. Well, I immediately experienced the slushiness you describe. Eventually I realized it was the wheels flexing and touching the pads in the rear. I opened the brakes in the rear as far as I was comfortable with and it only served to minimize the issue.

It came down to the wheel flexing side-to-side when I stood on the pedals. The Aeromax set doesn't do this at all.

The end of the story is that I gave his wheels back and chalked it up to them being just too flexy for my size. I suppose I could have worked on spoke tension, gotten new hubs for them or whatever else, but all of that was out of my paygrade (whether doing it myself or paying someone else to do it.)


I guess what I'm saying is that I, for one, don't think you're crazy.

rousseau

I forgot about this thread.

The outcome of this line of inquiry is that it was a motor problem. While I tightened up the spokes on the new (to me) wheelset and increased the spacing on the brakes, both of which needed doing, the real culprit, I think, was that I hadn't gotten over the early season hump yet.

Having put in a good solid two weeks of consistent riding since I started this thread, I'm more in the swing of things, and the hills have gotten easier. It doesn't feel like the wheels are rubbing against the brakes anymore (I don't think they ever actually were), and the wheelset itself feels terrific.

FBinNY 

See post no.13

Simple rule for any others. Unless you have an obvious source of friction, or low tire pressure, "sluggishness" will always trace back to an engine problem. The forces necessary to be a factor in loaded conditions, would cause very obvious drag and wheel slowing when unloaded.

rpenmanparker 

Hopefully whatever else would have worked, because spoke tension and new hubs would not. Not now, not ever. PERIOD.