XR2

The truth is if you feel faster and less fatigued riding 650BX42's that's your reality. So ride them. Let others debate it online and rack up the miles/KMs.

bobbycorno

Pretty much. Only reason I'm here is there's too much snow on the roads and I'm working on a chest cold. So I got nothin' to do but argue.

SP
Bend,OR

chewybrian 

Thank you for simplifying it. What I am getting is that if I compare two tires, both with the same max psi, then wider is better. If the max psi is different, then comparison is trickier.

Aside to the aside, can you give an opinion of the Diagonale rims? Did they last for you, and would you rate them 'clyde-worthy'? I like the look and the price, but are these rims ready for a wookie on a brevet? thanks.

bobbycorno

Couldn't a' said it better. There's real-world data and experience on the fat-tire side, so I tried it. It works. That's good enough for me.

One observation: I've ridden 650x35b's and 700x35c's (SOMA B-lines and Paselas, respectively) on almost identical bikes. THe 650's seem to accelerate better, and definitely feel lighter, even tho' the weight is very similar. Could the difference in diameter be coming into play? Smaller dia = lighter "effective wieght" or something? Just more fodder for the arguments. ;-)

SP
Bend, OR

Hydrated

Yessir.

The 650b has a slightly smaller diameter so even though the overall wheel weight is similar, the 650b puts much of the weight closer to the hub. Closer to the hub means less inertia to overcome. Less inertia to overcome means quicker acceleration and that "light" feel.

zandoval 

Next time my Babys need a new pair of shoes what am I going to get? - Fat, Skinny, Clenchy or Gluey - Platform or Steletoes - Chinese, Italian, or Japanese - Oh well - Maybe Payless - One things for sure - I often feel guilty with what my tires have to endure - Great discussion....

ColonelJLloyd 

I weigh ~185 lbs. I've only put ~500 miles on them. Wider rims give you less clearance for your brake pads, but that's not a fault of the rim. It seems to me that the Diagonale is very, very similar to the CR18, although it has a much nicer finish. I like polished rims and didn't have a problem paying the difference for that. The Diagonales are double wall, trible box section rims. I'd imagine they're about a tough as any non-V rims.

I believe bigger tires at lower pressures will help reduce the stress on the rims as well. I have used Panaracer Ruffy Tuffys (28mm) and Jack Brown Blue labels (effectively 35mm). I enjoyed riding on both. So, I'm no expert, but nothing leads me to believe these rims wouldn't be fine for a clyde. I would recommend the 36h version if you're on the heavier side. I have 36h in the rear and 32h in the front because the Shimano 3N-80 was only available in 32h.

Road Fan

+100!

Road Fan

Try them, Tom, the Paselas are nice, even as TGs.

Road Fan

Very good, Dave!

And: in racing, reliability is at least as important as speed. Fast guys whose stuff breaks don't finish and don't win.

zandoval 

Its all been done many, many times - I can't find it now because their web site is way to crowded for me to find anything easily but - The US department of Transportation has long lists of interactive tables on calculating energy expended over time on different road surfaces - They are very detailed - I remember getting into them years ago and a quick summary of what I can remember is: "...reasonably high tire pressures on clean paved surfaces allow for less energy to carry more load at higher speeds..." - Now that changes with the road surface, load and temperature - Most truckers know exactly what pressure to apply for what tire they are running on what surface and load they are carrying - Another source are the NASCAR tables showing the same data for speed and time - Again in general higher pressures are usually preferred...

I also remember that on trucks tire width was more realtted to load stability and speed of travel rather than friction and resistance...

I really don't know how this fits into the article, but the subject deserves more reading and research...

I personally use a wider raod bike tire (34mm) at as high a preassure as I can (85psi) and am satisfied...

noglider 

But square profile tires (as on cars and trucks) behave differently than round profile tires (as on bicycles, motorcycles and airplanes). Square profile tires' contact patch probably doesn't get much wider when pressure is reduced, but it does increase almost linearly with reduced pressure on a round profile tire. This is my intuition, not from any study, so I could easily be wrong.

So it could be that the above applies only to square profile tires.

I don't really know.

zandoval 

Absolutely - The thing here is that this needs more research - Most of the riders I have talked to through the years have said higher pressures are better - And there is a little data backing that up - But certainly there is more data out there - It could be this is a closely guarded secrete... Should we hire a spook???

noglider 

And with new tire innovations, old data might no longer be valid.

Road Fan

About the only thing that's clear is that in order to support load, the contact patch area has to decrease as the pressure is raised. If the pressure goes up by 10%, the area decreases by 10% if the weight the tire is supporting does not change. What this change does to the shape, is another and more complicated question, and probably just needs to be determined by measurement

mickey85

fify

Hydrated

OMG... guys... please!

Did you skip over post #33 in this thread?? Read it slowly... digest it... and you'll understand more about tires than most people do.

This thread contains so many erroneous statements about tire construction and performance... then they're backed up with anecdotal evidence and conjecture.

I've spent my entire engineering career in the aerospace arena, and over the last 30 years I've picked up a few things. Most of the tire stuff I learned during the 8 years that I spent sharing an office with an aerospace engineer whose entire job revolved around the design and modification of aircraft landing gear and tires. Even though I specialize in RADAR and electronics, I learned a ton from him about tires and suspension.

That given... there have been a couple of things in this thread that drive me crazy:

1) People seem to think that no research exists about the physics of tires and rolling surfaces. C'mon... really??

So drag racing rigs have tires that just magically hold together and resist flying apart as they accelerate from 0 to 300 MPH in under 4.5 seconds? And airplanes land every day on tires that simultaneously support the impact of a descending airplane and almost instantly go from dead still to rolling at 200 MPH. Trust me... there's a ton of research data out there that documents the way that tires work. And trust me... the physics applies to bicycles too. No exceptions. Bicycles are just a little slower than airplanes or top fuel dragsters.


2) There is no such thing as a "square profile" tire. All tires are round inside and out. All of them. The thing that makes the tire look square is the way that the tread is bonded to the casing. The tread is not of uniform thickness across the tire. It is thicker at the edges and thinnest in the center. This gives the tire the illusion of being square... but the casing is round as can be when it is inflated. Don't believe me? Look at the inside of any auto tire. Is it square in there? Of course not... it's round. And try over inflating any auto tire. Where does it wear out first? The center maybe? That's because all tires act the same when you add or release pressure. Yep... that tread may change it a little, but it's still gonna act like a tire.

So whether you're going 17 MPH or 170 MPH... you're going to roll the same. Well... nearly the same.

Ride on, guys.

noglider 

Thanks for weighing in, hydrated. As I said, I don't know, and I've tried to preface my conjecture by stating that it is mere conjecture. I'm happy to learn new stuff.

I'm sure there has been tons of research into auto and airplane tires. In fact, there is research in the bike tire industry, too. But I don't know where to read about it.

rootboy 

Gotta trust the word of a guy who quotes himself.

Nobody has even mentioned slip angles yet!
heh....

Hydrated

Hey... nested quotes! That's a great idea...

I could quote myself quoting myself... hmmmmm...

zandoval 

This is still a very interesting thread to me - I don't have a real use for it cause I ride an older not to special entry if at all level bike - But the knowledge is fun - I personally know what tire and pressure I like - I decided this by my riding abilities and equipment - And of course limitations on money - I do like the bantering of knowledge and evidence of reasonable opinions by the faint vapor trails of burning gray matter they leave...
My favorite tire - Kneda K35 at about 85 psi ($10.00) - On a smooth surface that ridge down the middle really works...

MacAttack

This explanation only really makes sense to me if you are looking at one particular road surface. Things get a lot more complex & subjective when trying to figure out which tire is faster for each particular type of road surface.

For instance what type of tire is fastest on a gravel road & why?
Which tire is fastest on a beat-up urban road?
Which one for a day of mixed surfaces?

Mike Mills

I would reiterate what some have already said, rider fatigue is as likely a factor in the real world as is rolling resistance of the tire. Sometimes we want to focus on just the hardware because it is ammeanble to simple tests and then gross generalizations are drawn from the test data. Human factors are rarely that simple. Remember, it is the rider that makes the bike go fast, not the tire. Ah, but I'm sure you knew all that.

Zaphod Beeblebrox 

and if that were truly the case, Professional riders would choose their tires based on comfort. (ostensibly...if all tires are equally fast)

....The TDF would be run on 38's.

Mike Mills

Well, now that you mention it, there are several long endurance rides/races that do typically use wider tires - Paris/Roubaix comes to mind.