Myth: Wide Tires Need Wide Rims:

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Mr.Gib
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by Mr.Gib

I am bringing this issue over from the gravel/cyclocross forum where somebody posted a link to Jan Heine's article in response to a question about choice of rim width. I felt Heine's contrarian viewed deserved to be aired and evaluated by the wheel and tire geeks.

The article:
Myth 18: Wide Tires Need Wide Rims:
https://janheine.wordpress.com/2019/06/ ... wide-rims/

My response in part was:
I am afraid this is nonsense. In the first place it is completely unsupported by any useful data. The whole idea that a wider rim results in more vertical sidewalls that are prone to callapse is just silly. Air pressure causes tires to take a uniform circular/round shape (uniform radius). A wider rim just means a slightly bigger circle. Deviations from a perfect circle are the result of varying tread thickness. More anectdotally, it is not possible to accept the idea that a tire with a narrower base of support will be more stable than the same tire with a wider base of support.
Afterall, were talking about the same guy who wrote this:

Myth 12: Disc Brakes Work Better Than Rim Brakes
"https://janheine.wordpress.com/2018/07/ ... im-brakes/
Unfortunately I've provided no data either, and simply am going by my intuitive understanding of physics - doesn't really qualify as science. I am curious if anyone agrees with Heine, or can provided a better argument why wider rims help wider tires perform better.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

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bm0p700f
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by bm0p700f

I am not sure what this post is saying.

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Alexbn921
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by Alexbn921

Rim and tire width are related. If you want to run wider tires you should match the increase in your rim. This helps the tire profile, casing support and aerodynamics.

alcatraz
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by alcatraz

If you hold a balloon by pinching with your finger tips or an open hand, which one is more stable?

I know, stupid simple analogy. I like simple though.

Mr.Gib
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by Mr.Gib

bm0p700f wrote: ↑
Sun Jul 07, 2019 10:26 pm
I am not sure what this post is saying.
Mr.Gib wrote: ↑
Sun Jul 07, 2019 9:05 pm
I am curious if anyone agrees with Heine, or can provided a better argument why wider rims help wider tires perform better.
Not that complicated. Heine says wider rims for big tires are BS. I say they are very helpful. What do you think and why?
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

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kytyree
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by kytyree

For one I'd say we need to establish what a "wide rim" is. At one point he's talking about a 20mm internal rim in that blog, to me that is a modern wide rim. I know they get a lot wider now but not that long ago I doubt I had anything that wide laying around.

I'm not sure when Fairwheel did this write up on alloy rims, but it's been a little bit http://blog.fairwheelbikes.com/reviews- ... m-roundup/

Look at those inner widths, 20mm internal is wider than anything on that pretty long list.

AJS914
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by AJS914

He's also talking about a much wider tire. I'm honestly not sure what to make of Heine's posts. I think some of his posts have merit but lack science. I think his stuff on rolling resistance is interesting. I don't think drum roller tests tell the whole story. His stuff on flexible frames "planing" is interesting. I'm not sure if it can give you 12% more power but I think it describes what I felt having had some frames that just feel magically fast.

This post kind of sounds like an ad for his tires. In the post he makes the distinction between tires with supple casings and those with stiffer casings.

In my limited experience, I tried a GP4000 25mm (26-27mm tire) on an old 14C rim and handling/cornering felt horrible and imprecise. I'm currently using the same tire on a C18 rim and they feel great.

On my gravel bike I run 40mm tires on C20 rims. I rum them at 25/30psi. I doubt I'd notice much difference if I ran 5mm wider rims. Would I notice much as the rims approached 30mm? Not sure.

bm0p700f
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by bm0p700f

That what I was asking. Wider rims go with wider tyres.

My min is take the internal width and multiply by 1.3 and that the min actual width of the tyre mounted and inflated.

Max width I am comfortable using is twice internal width. Beyond that is not unsafe but handling is affected adversely. Hense with mtb tyres a 25mm I eternal width rim is perfect for a 2.0" tyre bit most think the rim is too wide for the tyre. For off road tyres where side wall damage is likely using a tyre that twice the internal of the rim seem to be optimal. You get the right shape to maximise grip in the bends. For road tyres real tyre widths of 1.3 to 1.5 seem to offer the best performance.

Having read a number Jan blog posts I just cant follow his reasoning. Then again he thinks flexy frames climb faster.

Rims can get too wide for tyres and they an be to narrow too.

I am guessing Jan is not a fan of the hunt 48 limitless wheel where hint claim you can fit a 23mm tyre to a 22mm internal width rim. I hope I wrong about the internal width as the sidewalks would be tad exposed.

shuttlenote
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by shuttlenote

It was clearly evident that a ballooned tyre (25mm on a Shimano C60 rim) had a significant impact on drag, especially at higher speeds. In contrast the effect on the wider bodied Enve wheel was much less dramatic. In both cases a narrow tyre reduced the drag. The continental tyres tended to measure slightly wider than their stated width when mounted.
https://www.hambini.com/blog/post/bicyc ... s-fastest/


You'll have to decide which is more important to you comfort or reduce drag.

Mr.Gib
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by Mr.Gib

shuttlenote wrote: ↑
Mon Jul 08, 2019 10:43 pm
It was clearly evident that a ballooned tyre (25mm on a Shimano C60 rim) had a significant impact on drag, especially at higher speeds. In contrast the effect on the wider bodied Enve wheel was much less dramatic. In both cases a narrow tyre reduced the drag. The continental tyres tended to measure slightly wider than their stated width when mounted.
https://www.hambini.com/blog/post/bicyc ... s-fastest/


You'll have to decide which is more important to you comfort or reduce drag.
I think you can have both. You just need a rim that matches well with the "comfortable" tire
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

robertbb
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by robertbb

I think what bm0p700f says is right on point:

For a given rim:
Minimum inflated tyre size - take the internal width of the rim and multiply by 1.3
Maximum inflated tyre size - take the internal width of the rim and multiply by 2
Ideal inflated tyre size - split the difference between the above. Which on a 17c rim is precisely a 28mm tyre (well, 28.01mm)

You can "get away" with combinations either side of this, but they are going to be sub optimal.

Imaking20
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by Imaking20

Mr.Gib wrote: ↑
Mon Jul 08, 2019 11:47 pm
shuttlenote wrote: ↑
Mon Jul 08, 2019 10:43 pm
It was clearly evident that a ballooned tyre (25mm on a Shimano C60 rim) had a significant impact on drag, especially at higher speeds. In contrast the effect on the wider bodied Enve wheel was much less dramatic. In both cases a narrow tyre reduced the drag. The continental tyres tended to measure slightly wider than their stated width when mounted.
https://www.hambini.com/blog/post/bicyc ... s-fastest/


You'll have to decide which is more important to you comfort or reduce drag.
I think you can have both. You just need a rim that matches well with the "comfortable" tire
I think you have to accept a 25mm clincher as the largest "comfortable" tire then. Which, to be honest, I think is a perfectly reasonable volume considering 20+mm ID rims floating around now. When I think about experimenting again with lame (clincher) wheels, I picture something 19-21mm ID and no more than 24mm width.

If you are going to run a tire wider than the rim and have any sort of aspirations for maintaining aero, most tests would indicate that rim needs to be quite deep in order to offset the drag penalty from the light bulb - and even still the aero benefits are probably out the window if the tire is more than a couple mm wider than the rim width at the brake track.
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Mr.Gib
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by Mr.Gib

Imaking20 wrote: ↑
Tue Jul 09, 2019 5:42 am
Mr.Gib wrote: ↑
Mon Jul 08, 2019 11:47 pm
shuttlenote wrote: ↑
Mon Jul 08, 2019 10:43 pm
It was clearly evident that a ballooned tyre (25mm on a Shimano C60 rim) had a significant impact on drag, especially at higher speeds. In contrast the effect on the wider bodied Enve wheel was much less dramatic. In both cases a narrow tyre reduced the drag. The continental tyres tended to measure slightly wider than their stated width when mounted.
https://www.hambini.com/blog/post/bicyc ... s-fastest/


You'll have to decide which is more important to you comfort or reduce drag.
I think you can have both. You just need a rim that matches well with the "comfortable" tire
I think you have to accept a 25mm clincher as the largest "comfortable" tire then. Which, to be honest, I think is a perfectly reasonable volume considering 20+mm ID rims floating around now. When I think about experimenting again with lame (clincher) wheels, I picture something 19-21mm ID and no more than 24mm width.

If you are going to run a tire wider than the rim and have any sort of aspirations for maintaining aero, most tests would indicate that rim needs to be quite deep in order to offset the drag penalty from the light bulb - and even still the aero benefits are probably out the window if the tire is more than a couple mm wider than the rim width at the brake track.
But this assumes that one is racing. What percentage of cyclists race, and race at a level where the difference between 25mm and 28mm tire on a wide rim will impact the result? I am just trying to put forward the argument that wide rims are an advantage in handling and comfort to most cyclists, and was looking for some technical, physics, engineering support for my position. I was also more politely asking people to look at what Jan Heine was claiming (that wide rims might actually be worse), and to indicate if they thought he was as absolutely full of BS as I did. The guy even dresses like he wishes it was 1920.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

Imaking20
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by Imaking20

Yeah, I made no such assumption that one is racing. Slower riders actually benefit MORE from aerodynamic gains than the fastest racers. Although, considering forums are made up of people who like to obsess over minute details (just like the basis of this thread) - I find it hilarious that "well, only if you're racing" is like a carte blanche dismissal. But I digress..

It's totally fine to suggest wider tires and/or rims on grounds of comfort and handling (though I'd argue part of the difference in handling is also the increased trail that comes with larger tires). I was firmly committed to internal widths or no less than 17mm when I hung up my last set of clinchers. But your last comment said you think you can combine that with good aero efficiency. I'm saying there's likely a limit to that reality before you're right where @shuttlenote said - which is more or less "pick one."

As far as engineering or physics to substantiate the perception - it seems like you're looking for quantification of something that is VERY personal and subjective. Respectfully, I'd say it appears you're looking for science to support something you prefer. Ride what you want, ride what you like, I just don't think it's necessary to reach for scientific-sounding answers when "I just like it" will suffice.
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by Weenie


zefs
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by zefs

How can a wider rim be more comfortable when there is more material? same thing for the wider tire. Comfort comes from the spring effect. If the weight of the rider is so that you can't drop a narrower tire to low enough pressures to make it comfortable (and avoid pinch flats) for the riding conditions, then wider would be the right choice for that rider.

Then if you use the same pressure on the wider tire it will be less comfortable because of that extra material, but none does that.
Also with tubeless, you remove the tube and you actually gain in ride comfort.

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