BQ "Myth 18: Wide Tires Need Wide Rims"
 

I don't often start threads to be "provocative", but I didn't see a thread for this one yet, and was curious of the C&V Brain Trust's take: https://janheine.wordpress.com/2019/06/26/myth-18-wide-tires-need-wide-rims :)

It never would have occurred to me to think of narrow rims pinching tire beads close together as making it more tubular-like, and I'm still working through that concept.

It also seems to me that Keith Bontrager's intent when rolling MA2/MA40's into 26" rims wasn't necessarily to make narrow MTB rims, just to make lightweight ones. I'd welcome correction on that one.

I feel like the truth is somewhere in the middle on the rim width thing. Probably would have titled it "Do wide tires really need wide rims?"

I run 32mm tires on 15c rims. My only "complaint" is when they run down to 40psi, the get "floppy". I'm certain I would roll the tire if I corner too hard. Other than that, I don't give it much thought. Just my experience.

I read the BQ article. It makes some sense, but my biggest gripe with a wide tire on a narrow rim is that it reduces the width of the tire. I have 38mm Soma Supple Vitesse tires on a bike that measure to 35mm on narrow Wolber Alpine rims.

I read an article a little while back that said to multiply the ID of your rim by 1.8 to get the ideal tire size for that rim. Seems about right, but I wouldn't be concerned to go one way or the other too. I have had tires get weird/roll when going WIDE on narrow rims and not keeping them inflated well, but...

I don’t think this narrow rim verse has the same meter as the low pressure refrain

I don't want to be too harsh, but it seems like he's doing a bit of making up his own argument for wide rims, then acts a bit bewildered when that's not why wide rims are used, then continues along his attack of the argument he came up with. It's a bit of a headscratcher.

Even multiplying the ID of your rim by 1.8, would likely see many people using much wider rims than is often the case. :innocent:

I agree that he's going through unnecessary machinations, but I think he's right anyway. And it's a relief. I can stop worrying about at least one thing.

I don't know if I buy this:

Pros are using greater rim/tire width ratios than ever before. I know much of the reason is for aerodynamics, but clearly having a wide rim isn't detrimental.

Some pros have also been moving away from tubulars, I guess for some mix of disc brakes not overheating rims and tubeless clinchers. From what I can tell, a major racing advantage of a tubular is safety in a blow out, not handling.

It's almost like he has a vested interest...

How do we feel about a 25mm tubular being fitted onto a narrow wheel - I figure as long as its glued on well and correctly inflated it should be fine - they are always a pain to take off...

I think the most useful statement in the article is "the sidewalls don’t really hold up the weight of bike and rider. It’s the air that supports the weight." And note that this statement is true no matter which part of the tire is contacting the road at the moment. So his third conclusion "Using the tire sidewalls to hold up the rider results in a regressive spring rate. This can result in the tire collapsing suddenly." is contradicted by the earlier statement. I would say instead that a tire deforms quickly under a certain air pressure given the weight being supported. The reason the sidewall deforms is because the tread can't - it is plastered against the road surface! Our eighth grade science teacher taught us about Boyle's law using bicycle tires. He had us note how an automobile could be held up by as little as 10 lbs of pressure but a bicycle tire could be squeezed by hand (back when most of us had balloon tires - it is even more pronounced with low volume 23mm tires).

The combination of tire pressure, tire type (tubular/clincher/tubeless), rim width, rim volume, rider weight, riding style and a few other things I'm probably forgetting means that making a binary statement like "a wider rim is better/worse" is rather foolhardy.

I noticed the same thing when I replaced the front rim on my English 3-speed. The tires measured 35mm on the original (wide) steel rims, but the CR18 pulled it in to 33mm. Not the end of the world, but it still bugs me. ;)

iirc it is has been in very specific situations....time trials with everything optimized for that event. I can say my person experience with tubies is handling and ride is better......hope soon to do a corsa g clincher vs corsa g tubular comparison in a very apples to apples setup....not that I that fast

I've been riding wide Paselas (32c-38c) on Mavic Open Pro and Open Sport rims with zero issues. Wider rims might be better, but that narrow works just fine.

And yes, tubulars (or equivalent quality) are better handling and far safer when flatted (even blown out) at speed. You can ride a well glued on tubular to a stop reliably from any speed, even doing some of your braking with that wheel. You can also ride that flatted wheel as far as you need to. Yes, risking damage to the tire and rim, but if you have to, you always can. Gotta ride it 10 miles? Go ahead. I've had tubulars blow out at 45 mph. My heart rate spikes, but the rest is no big deal.

If you want to get an idea of how well tubulars corner, look at any photo of a '70s criterium corner. You will see unreal bank angles; angles we all took for granted. Scary yes, but less so than the idea of doing less, ie going slower among that tight pack of riders. The new G+ clinchers are getting close to what we rode 50 years ago. I am looking forward to going G+ tubulars.

Ben

I can't remember where but I remember a pro saying he was only going to race on tubeless after he won some race and discovered he got a flat which sealed, although I know tubulars can be run with sealant, but that was the story. Very gradual though. I suspect a large part is the peloton being conservative until a TdF win can be attributed to new technology.

This was a myth that I bought into for years until I purchased a '98 Cannondale f1000 mtb. It was running 2.1" knobbies on its narrow Mavic rims just fine.

I now tell folks they can run 32mm clinchers on Sun m13ii rims just fine without the need to use CR18s. I think the lighter rims provide the better ride.

Interesting. As someone currently running 32mm tires on 13mm rims (which I really didn’t want to do) I welcome this news. Of course once mounted the tires only measured ~ 28mm, but I’m guessing some part of that is due to manufacturer spec “error”. (They’re cheapie Contis fwiw.)

I do cynically wonder though if this might be a veiled attempt to sell more expensive wide tires.

As for MTB, commonly seen are very wide tires on narrow clincher rims.

Going back to 1989, Trek spec 8000 with 1.9 in. width on very narrow Matrix rims. Used Kevlar bead, foldable rubber.

Wide tire on narrow rim for road is just rider preference to application road terrain and probably doesn't cause harm to a tire sidewall. Personally, I don't like the squirmy feel or handling.

Back to frame material. Is the industry cloaking poor riding modern carbon lightweights and now relying on the magic tire?

Not trying to divert the topic but just the other night out with a fast group, all but myself on modern carbon- we reached a section of road having repaired frost breaks in the asphalt. The group really backed off the pace and some complained due the harsh 'bump' 'bump'.

The bike I was riding likely averaged 8 lbs heavier, Columbus Tre-tubi steel, 32 hole rims on 23mm width tubular (funny yet on some tattered and old Vittoria). I was riding on a cloud, easily covered those miles and could have crushed the pack.

Only those who push the bike hard, really hard, could ever notice what Heine is discussing. Getting guys like that to agree about anything will never be easy. Even coming up with language to describe how tires feel is not easy and getting all in the room to use same language is unlikely.

MTB tires we used on skinny rims in 1989 are nothing like tires available now. Not clear to me what could come from talking about tire/rim combinations from thirty years ago.

My own recent experience is that 35 and 32mm tires on 13mm internal rims do feel a bit squirmy. Not a big one. They do feel better on wider rims. 28mm tires that never did a thing to complain about on 13mm rims do feel nicer on 17 or 19mm rims. But then I've a set of Jan's own tires @41mm (advertised as 44) also mounted on 19mm rims and they feel just great. Not going to buy and build another set of rims to find out if there are higher levels of perfection.

My SS and Fixed are both on standard narrow Velocity deep V rims. I run cross tires, 40's on the black fixed and 38's on the SS, neither measure up to width by a fair amount. But they look great and ride like any other tire to me. No rolly or odd feeling and I ride them pretty hard.

I put wider on my road (28's) and have been doing some group rides with, so far they feel slower and not as snappy. But no issues, although the jury is still out.
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Regarding clinchers, no, it's pragmatic.

I found out the difference the hard way, one of my first time riding clinchers.

Light rain, a moderate curve, and a pothole unseen till too late. I was down on the floor before it even registered in my brain that I flatted. Like hitting an oil patch in a rotary in the rain... Sucks. It's instantaneous. You're flying along one moment, the next you're giving up skin. Luckily:notamused: I'm a lot slower than I used to be. I was bruised, and embarrassed. What the heck? A front blowout happens with tubulars, there's a good chance of remaining upright. I found out it's not so easy with clinchers. The pros know this.

There have been some tubeless wins, but apparently they still have problems. I think the pros will mostly stick to tubulars, until tubeless are as reliable in all situations. Clinchers will remain the province of TTs and perhaps in races with no fast descents.

I've ridden tires that are too wide for the rims. It can be done. But it costs handling. The shoulders are inadequately supported so fast curves feel squishy and splashy.

For several months I've ridden 700x42 Continental Speed Rides (nominal, actually measure closer to 700x38) on 622x14 rims. No real problems. But I wouldn't recommend it. That's just my hybrid for casual rides and errands.

The widest I've tried on my road bike's 622x14 rim is 700x25, and those felt a bit splashy on curves compared with 700x23. Not sure I'd try to push it to 700x28 on a bike I like to ride fast.

Yeah, I mentioned that earlier in the thread since the "myth" addresses descending on tubulars from a handling and not safety perspective. Tubeless tires are less likely to blow out and come off than normal clinchers because of the tighter hook/bead interface, sealant, rims not getting hot anymore, and tube related issues.