The_Snail

the wheel is a 28 spoke, 3x both sides. White Ind. T11, cx-ray or aerolite (don't remember), Velocity Quill
the wheel is perfectly dished when the tire is off, or deflated. but once inflated (40mm tire), it deflects towards the drive side by about 2mm
i was thinking of rebuilding using DT competition (2.0-1.8) for the DS for their heavier gauge. since i have to replace some spokes anyway due to chain drop.
or just dish the wheel to the NDS to compensate?

FBinNY 

Inflating tires compresses the rim. The effect is related to the pressure x width, along with the rim's weight. (higher weight means greater cross section area, thus greater resistance to compression).

Since dished wheels are asymmetrical, the effect on tension is also, and the deflection is expected. If you plan on using these same tires at similar pressures, you can compensate so it moves to where you actually want it.

OTOH this has been going on forever, and the difference is probably meaningless in the scheme of things.

Andrew R Stewart 

Redish/tension the wheel/spokes with the tire on and pressured up. Andy

79pmooney

This has probably been happening on my bikes (well, not my fix gears) for the past 50 years. Never noticed. I build my wheels with dish for a centered wheel, no tire. Put the tires on. Blow up. Put wheels on bikes, centering the tire between the chainstays. Adjust the brakes to the rim; both the caliper and the pad heights. Ride.

So I guess I've been riding rear wheels askew by 2 mm forever. And unconsciously compensated every time I sat up and road no-hands. I guess all my geared bikes have rear ends that drift to the left. Funny. And I guess I've sorta noticed that the pads don't quite sit the same heights on the caliper arms.

And thinking more - yeah the tire has always wanted to sit closer to the DS chainstay on my ti custom with its vertical drops, 130 spacing and 9-speed wheels. I bet the stays on my rear fender aren't equal length (which I believe I've noticed putting on new ones). I think I'll try dishing my rear wheels 2mm less next build. Perhaps my bikes will ride a little straighter, a small burden may be lifted from my psyche and perhaps the Earth's rotation will be spared a little wobble.

grumpus

I've built plenty of wheels, trued/dished many more, I can't believe I've never even thought of this, it's so obvious. I'd expect that working to a tolerance of max 1.0 mm I'd have noticed the difference, at least with close clearance road frames, but I guess not.

grumpus

That's lighter than the cx-ray, which is effectively 2.0 mm plain gauge.

FBinNY 

This is the problem when people start measuring stuff and suddenly discover how imprecise the real world is.

OTOH the deflection was less of an issue BITD, since we were riding narrower tires on wheels not dished over as far.

In any case, that nobody ever noticed an issue riding these "wrongly dished" wheels, is proof that that the working tolerances are greater than most believe.

kcjc

Wow, I never contemplated this! I think I only checked the dish a handful of times on the frame when I first started riding in my early teens. That was an old 5-speed clunker, and I simply turned the wheel around on the frame to get a general feel. I never had much luck trueing, rounding, and dishing on the frame, especially with the tire on. Luckily, by college, I had access to a trueing stand.

Steve B.

This was fascinating. It occurred to me that I only and quickly check for true on a new wheel and only once on a mail order wheel have had to fix it. I've purchased 2 pairs of carbon wheels in the past year for my mt. bikes, made the (possibly stupid) assumption they were true out of the box so did not check, mounted the tubeless tires and put them on the bike. There's a bit more tolerance with 2.4" mt. bike tires, but when I spun the wheel to get sealant moved around, they looked true so left them alone. Haven't done a new road wheel in 5 years. After that if I noticed a road wheel running out of true after some use, I stuck it on the truing stand and fixed it, WHILE THE TIRE WAS ON THE WHEEL AND INFLATED. I would never bother removing a tire to re-true but as well, never had to deal with a wheel with no tire having a different position than a wheel with an inflated tire. Good info to know.

70sSanO

I had never heard of this before. But I had a similar strange phenomenon happen to me.

A few years ago I took a 130mm OLD and reduced it to sub 128mm with some creative manipulating on the DS. Put it on the stand without a tire, re-centered it, making sure it was dished properly and stressed relieved.

A couple months ago the RD cage looked a bit too close to the spokes, so I put the wheel with the tire on the stand and the dishing was off by over a mm toward the DS. My first thought was I must have done something stupid when I re-centered the rim years ago.

Now, maybe not.

John

79pmooney

Or ... ride wheels without dish! Yeah, yeah, dish allows lots of cogs, discs ... But wheels without (or with very little) are better wheels. Don't believe me? Take a hard right corner on a 130 OLD wheel with tons of cogs, then take the same corner on an identical wheel except single speed and no or very little dish. Bike simply feels more solid, even if you use the same light NDS spokes on the DS.

Derailleurs are great, But with dish, vulnerability to DS crashes and need to keep exposed chains in very good shape, not ideal. The ideal geared bike (maybe a century or two away) will be a different system entirely.

And another point. To keep your dish optimum riding gravel AND road, you need to re-true every time you change tire pressure! Get rid of those those derailleurs and make your bike a perfect dish!

Dan Burkhart 

(Channeling Fietsbob) A Rohloff is 100% symetrical. Just sayin

79pmooney

I might simply start building my rear wheels with no dish - fix gear, 1mm short on dish - 7-speed 126 OLD wheels and 2mm short on dish on my 9-speed and more 130 wheels. Tired and aired - ought to be plenty close enough. Easier to build also.

79pmooney

Yes. But it is not the performance equal of modern derailleurs. We are still an "ah ha!" away from the ultimate.

FBinNY 

I get that this is an OMG moment for many, but some perspective helps.

First of all, there's a big difference between an observed phenomenon, and a problem. That nobody's talked about this for however long as we've been riding dished wheels should be a clue to its (in)significance.

However, for those who obsess over stuff like this, a reminder ---- 90% of the time we're riding across a sloped surface, moving the bike's point of conract 1-3mm or so to the left. So, rather than "fix" the rear wheel, you might want to dish the front.

cyccommute 

This is not a common problem no matter if people are measuring stuff or not. For decades we have had visual indicators of a centered wheel mounted on the bicycle, i.e. rim brake pads. Deflection of the rim to the drive side isn’t something that people have reported in the past. I have mounted many wheels without tires into a frame during buildups and used them to align the brakes. I’ve never observed a shift of the wheel center to either side after mounting a tire.