Rim width vs tire width

[Drew Fitchette]

Hey all,

Wanted to ask as I see lots of differing opinions from wheel/tire manufacturers about proper tire width for different rim widths. I’d always heard you don’t want your tire more than twice the internal width of your rim, but the RH website has a table and some blog posts to the contrary. I also saw on the WTB site something similar. 

I know context matters a lot, so for reference I’ve got a set of Velocity Atlas Rims (19.8mm internal width) and a set of 44mm RH tires(the high end of Velocity’s suggestion) on them but was looking to move them over to a frame with wider clearances than my Sam. I’m not sure how wide I can go, RH’s table says up to 55 and WTB says 50. 

Moving them because I’m planning a trail/mostly off-road camping trip for spring and this wheelset has a Dynamo. 

Thanks for any guidance/advice!

[Will Boericke]

I mostly ignore these recommendations, as I find I can run pretty much any tire on any rim (assuming tire is wider than the rim).  Probably the most egregious example in my household is my son's bike with 2.6" (66mm) tires on 17mm internal rims.  Works fine.

Will near Boston

[Brian Turner]

I have a 26" Atlantis with Atlas rims, and have run Humptulips Ridge tires on them with no problems whatsoever. They measure about 50mm wide on my Atlas rims.

Brian

Lex KY

[DavidP]

I've had no issues running CR18s (17.5mm internal) with 2.2 Race Kings (51mm on these rims) or Aeroheat/Dyad (18.6mm internal) with Rat Trap Pass (also ~51mm here).

-Dave

[Bill Lindsay]

"I’m not sure how wide I can go,"

There's no hard number that we can guarantee.  If you want to run 80mm wide fat bike tires, that's probably too much.  If you want to run 60mm tires, that's probably fine.  If you want us to collectively identify the absolute widest tire on Earth that is absolutely guaranteed to work on your bike on your bike packing trip, no matter what the conditions, then that's harder.  I agree with the above that I  would have no problem running 55mm Rene Herse tires on Velocity Atlas rims.  

Is there a particular tire that you want group "permission" to run?  What is the tire clearance on this other bike?  

Related to super-fat tires on super narrow rims is brake pad considerations.  With cantilevers and fixed-arm V-brakes, the brake pads dive as they come in.  Wide tires can get cozy with that brake pad path, and you need to pay attention to it.  Parallelogram-type V-brakes move the pads in a better line relative to that overhanging tire side wall.  All this stuff is manageable, if one keeps track of it.  

Bill Lindsay

El Cerrito, CA

[Mr. Ray]

Here is a chart I use:

[Drew Fitchette]

Thanks for all the feedback, y’all! Appreciate the examples. 

Bill - no tire in mind in particular but was mainly wondering if folks had any knowledge on if there was a line not to cross in terms of sizing. Was looking at a few different options, but wanted to hear folks’ experiences. 

Happy thanksgiving to all who are celebrating today!

- Drew

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[Patrick Moore]

+1 for almost any tire on any rim, and I can beat Will by 4 mm: 72 mm actual WTB Rangers tubeless on 21 mm IW OEM Alex rims on that Monocog — non-tubeless but even at 12 psi no problems. (Perhaps no problems because 12 psi.)

Back in the day Sun and other major mfrs made 13 mm IW 26” “semi-aero” rims for 50 mm knobby tires; that was the style in those days (channeling Abe Simpson).

Now, 72 mm on 21 mm is hardly the best combination, but it worked.

Patrick Moore with:

27 mm Elk Passes on 13 mm IW rims;

41 mm Naches Passes on ~15 mm IW rims;

49 mm Oracle Ridges and 50 mm Soma Supple Vitesse SLs on 27 mm IW rims

And shortly, God willing, 60 mm Big Ones on 21 mm IW rims.

All in ABQ, NM.

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[Patrick Moore]

Sorry, that should be: 72 mm actual width WTB Rangers tubeless on ~ 19 mm IW rims.

[Mackenzy Albright]

I emailed Jan Heine once about RTP's on mavic 717 which have a narrow inner width - I think 17mm. He said it was fine. I ran them for a long time and was indeed fine. I did notice that when the tires tended to squirm at lower pressure vs SBH's on velocity blunt SL's (19mm) but those were also tubeless. IME it effects the range of air pressure more than anything.

[Patrick Moore]

Exactly. With appropriately wide rims you can play relatively fast and loose with tire pressure, but with really fat tires on not-quite-wide-enough rims you do have to be more careful about pressure.

Still …. 72 mm actual on ~19 mm IW rims at 12 psi (tubeless) …

Happy Thanksgiving, everyone. I got a nice if brief and short RT ride in on the 1999 Joe Starck Riv custom road fixed gofast to church and back this morning despite feeling queasy, lightheaded, and palpitating; had to cancel a TG dinner with guests but managed to enjoy a solitary TG meal anyway.

On Thu, Nov 28, 2024 at 3:02 PM Mackenzy Albright <mackenzy...@gmail.com> wrote:

...IME it [= fatter tires on narrower rims] effects the range of air pressure more than anything.

[Stephen Durfee]

Wish this thread had been started yesterday, as I tried fitting a 2.1" Billy Bonkers onto an old Mavic 217 rim (17mm), got scared from the lightbulb profile, then called Rich to order up a new wheel...but now I'll finally have a proper matched rear to go with the front dynamo wheel that he built up for me earlier this year.

[Seth]

How does the calculus change for tubular tires/rims?

[Peter Adler]

That's a good question. I only know about old tubular rims, which are all fairly narrow; 20mm sidewall-to-sidewall on a 1960s Fiamme Red Label I just checked is typical. But even on wider profile types like the old Dugast 32-33mm cyclocross tires I have around or the 36mm Challenge Strada Biancas I'm hoping to use soon, the width of the base tape is the same, regardless of the width of the tire. If a wide tire has the same width gluing surface as a narrow tire, does the width of the rim make a difference if the mating gluing surface on the rim matches that on the tire?

I suspect the biggest issue is brake pad travel, just as with clinchers. I will note that, unlike cantilevers and V-brakes, the pads of sidepull and centerpull brakes arc from below the rim towards the braking face as they compress, making them easier to keep clear of the tire sidewall.

Peter Adler

Berkeley, CA

[Toshi Takeuchi]

Sorry I'm late to this thread, but back in the day (mid 90s?), I was mountain biking on Mavic Open Pro rims with 2.5" tires.  I think that is 15c (inner width) with ~62 mm tires?  That's way off the chart below, but I never had any issues over many years of riding.

Toshi, still alive in Oakland, CA

[Patrick Moore]

+1. Back in my day I rode 50 mm tires aggressively offroad on ~13 mm IW rims for years with no problem, and recently rode 72 mm actual tires on ~18 mm IW rims, tubeless tires on non-tubeless rims, just with lotsa tape, again with no problems. 

You do have to keep the pressure up, tho’ I rode the 72s down to a safe 12 psi.

Patrick Moore, channeling Abe Simpson in ABQ, NM.

[Bob Walicki]

Ha, was in my LBS on Monday picking up my bike and talking about building up some 650b wheels. We were chatting about rim width with respect to tire width and the only callout my pro made was that a wider rim will "flatten" the tire profile. I mentioned that maybe really wide tires would look silly on narrow rims, and he responded "you've got way better eyes than me". 

We chatted some more, but he is definitely in the "any tire on any rim" camp.

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[Armand Kizirian]

Jan Heine's take on the topic. I trust his opinions on tires, hard to argue that many people in the world have spent more time studying and experimenting with tires.

https://www.renehersecycles.com/myth-18-wide-tires-need-wide-rims/

[J-D Bamford]

I tend to trust matrices published by WTB and Rene Herse because there's evidence they really put some thought into it and in all likelihood have written notes on things they've tried if not formally tested. Whereas other sources will just have a sentence or two and it feels like a lawyer's take on it. Often in the sizes I've checked, it feels like 2:1 is a soft rule of thumb and I think we like those sort of easy ratios. But in real life, we've all seen and probably ran well over 2:1 as @ttoshi described. My wife's 1990s era Rock Lobster hard tail runs 2.3" tires on IIRC Open Pro rims with 15mm ID or such (almost 4:1) and that was totally the norm. Looks like Jan's ETRTO chart repost generally suggests up towards 3:1 and that feels like a good hedge against the possibility that modern light weight rims are perhaps less overbuilt (so maybe more tire size/pressure sensitive?) than what we had in the past. Admittedly conjecture on my part.

No offense to anyone, but I discredit any chart which doesn't seem to clarify between outer and inner rim width (although admittedly it's probably inconsequential), and uses "c" vocabulary when what they mean is "millimeters" because Sheldon long ago showed us c's irrelevance in the modern world of rim standards. I'm a snob on colloquial terms which happen to dilute meaning. But hey, I think a lot of perfectly good people in this world would rather refer to rim width in "c" because that saves three syllables off the tongue.