Tire profile changes on different rim widths (Mountain King 2.2)

[shiggy]

I spent a weekend riding Conti Mountain King 29 x 2.2 tires on wide Salsa Gordo rims. The profile was noticeably "flat" with the relatively small tire on the 35mm rim.

conti_mk22_med.jpg
Salso Gordo 35mm rim on the left, 24mm rim on the right.

Noticed a few handling quirks that may be related. More details here.

[Dogdude222]

Interesting. So, it seems that wider *may* not always be better. Thanks for the honest opinion Shig.

[RedGreen]

Yeah, that's about the exact opposite of what I thought would have happened... did you make sure things like tire pressure, suspension settings, and dirt conditions were the same?? any of those could make a difference... it makes sense though that floating on top would make the handling more skittish

[29erchico]

Shiggy:

Read your info on your site and tend to agree on your theory there. On my KH front rim the 2.4 MK felt pretty good in deep loose gravel at 28 psi.. Not as good as a Kodiak, Rampage or Nevegal (listed in the order of decreasing durability, I rate the Neve as unacceptable in this department) but solid enough. Looking at the MK 2.4 on the KH rim I felt that I might not want to mount a skinnier tire on that rim.

I like the MK 2.4 up front for wet to barely moist conditions. Since I don't ride in slop, I have no opinion about the tire in really loose mud. In dry conditions there are better choices as far as I'm concerned.

[Ronnie]

Provided that the rim is wide enough to prevent the tire from not rolling off, I see no advantage to using excessively wide rims. The shape/width of the contact patch, when using a wide tire on a narrower rim can be changed by changing tire pressure. A tire that has it's tread area stretched out and flattened by a wide rim is not likely to be changed much by lowering pressure.

Of course the rim needs to be wide and strong enough for it's intended use.

Ronnie.

[megalow maniac]

I totally understand the conclusions you draw from your observations. But than again, the MK 2,2" ist terribly narrow - compared to any onther 2,2" tire out there. I'd say it is not suited for the use with a wide rim in general. If you had used a tire with reasonable width, such as the MK 2,4" the wide rims would not have compromised the tires' characteristics.

[Mike Brown]

Shiggy, your website makes sense, but I guess I'd ask if I'm running a 35mm rim that weighs hundreds of grams more than some other offerings, why would I run such a low volume, small knobbed tire? Also, I'd NEVER use such a small tire on the front of my bike, which is where handling would be most effected in your drawing.
I've also experienced an advantage from the profile change pictured with the ExiWolf in the back. My main beef with the Exi has always been that the cornering knobs were so far down on the sidewall that they were practically useless in fast, hard turning situations. The "flatter" profile moved the knobs up just enough that they actually hook up...a great improvement.
As you can see, I find this info and these pictures interesting...thanks for posting.

[boomn]

Originally Posted by Ronnie

Provided that the rim is wide enough to prevent the tire from not rolling off, I see no advantage to using excessively wide rims. The shape/width of the contact patch, when using a wide tire on a narrower rim can be changed by changing tire pressure. A tire that has it's tread area stretched out and flattened by a wide rim is not likely to be changed much by lowering pressure.

Of course the rim needs to be wide and strong enough for it's intended use.

Ronnie.

Depends how far you take that conclusion I think. A narrower rim with lower pressure sounds like a formula for pinch flats, and that has been true for me in the past trying to get by with 21-23mm rims on rocky terrain. Using 28mm rims currently (wider than xc but certainly not excessively wide) I have noticed less pinch flats at similar pressures

[shiggy]

Good discussion, guys.

Why did I put such a small tire on that wide a rim? To find out how it would work! You need to explore the extremes to know how things actually work. As I mentioned on my site, I need to go ride the same trails with the MK 2.2 on narrow rims to see if it is indeed mostly the rim width and not just the tread design.

Different tires--width and tread design--will react differently on wider and narrower rims. The tread can "open" or "close", altering the open space between knobs and the angle of the lateral working edges, affecting the bite and tracking. Edge blocks can be "raised" when the tire is mounted on a wider rim, which may improver cornering grip or make it worse, depending on the design. With some tires the edge tread is nearly useless on a narrow rim. Others--usually with tall side knobs--the wide rim can make it edgy and track poorly. And riding style does come into play.

I have also noticed that even some wider tires on the wide rims seem to slip laterally more on off camber ruts, roots and rocks. Possibly related to the edginess some tires get.

[dRjOn]

i ran 35c cross tyres on old delgado rims in a cross race on a jones space frame about 2 years ago.

it was weird.

[shiggy]

Originally Posted by dRjOn

i ran 35c cross tyres on old delgado rims in a cross race on a jones space frame about 2 years ago.

it was weird.

Which Delgado rims? Cross or Disc?

[Ronnie]

Originally Posted by boomn

Depends how far you take that conclusion I think. A narrower rim with lower pressure sounds like a formula for pinch flats, and that has been true for me in the past trying to get by with 21-23mm rims on rocky terrain. Using 28mm rims currently (wider than xc but certainly not excessively wide) I have noticed less pinch flats at similar pressures

That is obviously true taken to extremes but I'll wager that there are more riders on narrower rims at "lowish" pressure than not. The low tire pressure debate has been extensive. Most would agree that lower pressure improves handling. Shiggy's results indicate to me that a rounded tire profile that is able to conform to to the terrain performs better than a stretched out tire. Perhaps a Mountain King 2.4 would work a whole lot better on the Gordos as the profile would be rounder.

Firstly though, we need to consider what rim width measurements mean. Gordo rims are listed as 35mm. I have no idea if that means externally or internally. Mavic's TN719 is listed as a 19mm. rim but that is internally so externally they are probably at least 23mm. Stan's Flows are 22.5mm. and 28mm. respectively. They are not a lot wider than the Mavics.

My next set of wheels will be wider, similar to yours, to facilitate wider tires but I have had no problems with the likes of 2.3 Eskars (which are exceptionally wide) on my 19mm. rims at about 27psi. Granted I have been running TLR.

Ronnie.

[boomn]

Originally Posted by Ronnie

That is obviously true taken to extremes but I'll wager that there are more riders on narrower rims at "lowish" pressure than not. The low tire pressure debate has been extensive. Most would agree that lower pressure improves handling. Shiggy's results indicate to me that a rounded tire profile that is able to conform to to the terrain performs better than a stretched out tire. Perhaps a Mountain King 2.4 would work a whole lot better on the Gordos as the profile would be rounder.

Firstly though, we need to consider what rim width measurements mean. Gordo rims are listed as 35mm. I have no idea if that means externally or internally. Mavic's TN719 is listed as a 19mm. rim but that is internally so externally they are probably at least 23mm. Stan's Flows are 22.5mm. and 28mm. respectively. They are not a lot wider than the Mavics.

My next set of wheels will be wider, similar to yours, to facilitate wider tires but I have had no problems with the likes of 2.3 Eskars (which are exceptionally wide) on my 19mm. rims at about 27psi. Granted I have been running TLR.

Ronnie.

I understand and agree with the benefits of lower pressure. I used low pressure on my narrower rims and I use similar pressure on my slightly wider current rims. I was just countering your statement that narrower rim would do the job just as well if you ran a good low pressure. Sure the contact patch might be what you are looking for, but I am trying to point that there are secondary effects of rim width. As I mentioned I now have less pinch flats with a wider rim, even when I am hitting down to the rim on rocks. Also, tires of the same width now have less of the disturbing side-to-side squirm and flex under cornering that came from low pressure on a narrow rim.

[shiggy]

Originally Posted by Ronnie

That is obviously true taken to extremes but I'll wager that there are more riders on narrower rims at "lowish" pressure than not. The low tire pressure debate has been extensive. Most would agree that lower pressure improves handling. Shiggy's results indicate to me that a rounded tire profile that is able to conform to to the terrain performs better than a stretched out tire. Perhaps a Mountain King 2.4 would work a whole lot better on the Gordos as the profile would be rounder.

Firstly though, we need to consider what rim width measurements mean. Gordo rims are listed as 35mm. I have no idea if that means externally or internally. Mavic's TN719 is listed as a 19mm. rim but that is internally so externally they are probably at least 23mm. Stan's Flows are 22.5mm. and 28mm. respectively. They are not a lot wider than the Mavics.

My next set of wheels will be wider, similar to yours, to facilitate wider tires but I have had no problems with the likes of 2.3 Eskars (which are exceptionally wide) on my 19mm. rims at about 27psi. Granted I have been running TLR.

Ronnie.

The Gordo is 35mm as measured outside, which has been the consumer standard for measuring width (easier to check with a tire mounted). The inside measurement is used for a rim's ISO width. In general the outside width is ~5mm greater than the inside.

Boomn-
I think there is more to it than just wide rim=low pressure. There is a sweet spot for every rim/tire/pressure combo. Changing any one affects the others.

Tires can be run at lower pressure without squirming on wider rims, but that may be too low to prevent pinch flats. The MK 2.2 did not squirm on the Gordo at 28psi but I did have (minor) pinches. From past experience I would probably use about 30psi when mounted on a 24mm rim.

I was able to run the much higher volume Rampage 2.35 on the Gordo at 22psi without squirm or flats but need to use ~28psi on a 24mm rim to prevent squirm.

[boomn]

Originally Posted by shiggy

Boomn-
I think there is more to it than just wide rim=low pressure. There is a sweet spot for every rim/tire/pressure combo. Changing any one affects the others.

Tires can be run at lower pressure without squirming on wider rims, but that may be too low to prevent pinch flats. The MK 2.2 did not squirm on the Gordo at 28psi but I did have (minor) pinches. From past experience I would probably use about 30psi when mounted on a 24mm rim.

I was able to run the much higher volume Rampage 2.35 on the Gordo at 22psi without squirm or flats but need to use ~28psi on a 24mm rim to prevent squirm.

I think that matches what I was trying to say but couldn't explain well enough I like the sweet spot better on my somewhat wider rim, because that's what it took to make a 2.3ish tires feel as confident to me as a 2.1 tire of similar construction on a 23mm rim at a pressure I would like to ride

[Turveyd]

Wider Rim increases the air volume of the tyre without any extra tyre weight ( Rim weight ofcourse ).

But it also flattens the profile, which increases stability especially at low pressure, it also increases traction, comfort but the downside is especially on the rear it also increase the Drag.

There a nice very round profile tyre so fast.

I dumbed my internal 29mm rims for 21mm internal ages ago, cause the drag with the same tyre and pressure setup to what I ride for both, was just miles apart.

Remember the front is less of a drag issue especially while climbing as not much weight at all on the front, so a 35mm up front to increase comfort and traction is almost without a downside.