I have a 19mm internal rim (because I'm too poor to buy new ones) and ride with a 2.35 tire set up tubeless at 23-24 psi and no issues. I weigh 175ish if that matters.

 

^^^I tried this on my old 26er when I weighed 175#. For me, it did not work. I ended up near 40psi, then fortunately sold the rims to a buddy who was building a super lightweight bike for a lightweight rider. They did OK with 1.95-2.1 tires.

There are too many variables in play to give blanket suggestions in my opinion. Rider weight, actual tire size, casing construction variances for a given mold (protective vs non-protective), different compounds for a given mold (full sticky vs multi-compound), intended usage, etc.

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I would agree with not making blanket statements, but what if we start with the DT Swiss guidelines above. I think their chart indicates what you could do, but not really what you'd want to do. They seem to recommend/allow some fairly narrow rims with wide-ish tires - which works for some, but even they might choose otherwise if they had the option or if it was easier. Adding to that confusion, it seems some mfr's even spec somewhat narrow rims on brand new plus bikes. Maybe just to drive aftermarket sales of replacement wheels. :???:

IDK, maybe I'm thinking too much. :crazy:

-F

 

There are too many variables in play to give blanket suggestions in my opinion. Rider weight, actual tire size, casing construction variances for a given mold (protective vs non-protective), different compounds for a given mold (full sticky vs multi-compound), intended usage, etc.

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Wide rims support the tire better. All other vehicles use a rim that is close to the tire size.
The main problem is that mountain bike tires are designed to fit on narrow rims because that's what was available. Now that rims are growing, tires are starting to catch up. Maxxis is making WT that give a better profile on wider rims. Tires designed for a wider rim can incorporate larger tread spacing and a more rounded shape to keep handling consistent.
In a perfect world a tire that is 60mm should be on a 50ish mm rim and have wide enough tread to protect the sidewalls.
Let's say that 35mm internal is the new normal, even a correctly engineered 53mm tire should have no trouble fitting with a desirable tread pattern and profile. Time will tell, but I believe the majority of tires will transition to fitting on wider rims.

 

Wide rims support the tire better. All other vehicles use a rim that is close to the tire size.

The only other vehicles it's worth considering are other 2-wheels vehicles, as nothing else is purposely (generally) leaned over and requires a rounded profile. Essentially most other vehicles require a flat contact patch and therefore need the width to match up quite well.

It's also during a lean (cornering) where traction is most critical, aside from straight-line braking.

Wide rims still do support the tyre better though, there's no arguing that. However beyond that it's a combination of what side rim the tyre was designed around (opens/closes the tread spacing), how much protection you want to give the tyre sidewall and your rim from rocks etc, and personal preference.

As for actual figures, well the problem is that a Maxxis inch is not equal to a Schwalbe inch and so on.

 

Some more reading material

Easton has a pressure chart also:

https://www.eastoncycling.com/media/Easton Rim pressure.pdf

Schwalbe has a lot of technical info;

http://www.skeppshult.se/media/1140/techinfo-2015_gb.pdf

Surly:

http://surlybikes.com/uploads/downloads/Surly_Tire_Intructions.pdf

 

For whatever its worth, I am running WTB Ranger TCS Light 26" 3.0 on my Kona WO's 80mm wide Mulefut rims in the rear and a Jauggernaut Pro 4.0 up front. This combo seems to work great for my Fatty bike. It lowers the profile in the rear but widened the 3.0 to 3.25 but gives very little side rim protection. I swear this set up runs really smooth. The 3.0 allows quicker initial inertia and the 4.0 allows float up front for sand and muck, all based on my uneducated theory!!! I run about 12 psi in both, generally hard-pack terrain. Not super fast but for climbing and technical stuff it's awesome and Fattys are just to fun!!!

 

Not to mention rear triangle clearance to tire width. Oops, sorry I mentioned it.

 

DT Swiss has a chart of which tire widths are acceptable with which rim widths:

https://dycteyr72g97f.cloudfront.net/uploads/W0X1900AEIXS012610/MAN_WXD10000000866S_WEB_ZZ_001.pdf

 

According to this you can run an 81mm tire on an 80mm rim. That's fun.

 

Sorry for the conspiracy theory, but I think it's all about selling more expensive wider rims after recommending them for (more expensive) wider tires. I have a very standard tire Maxxis 27.5" x 2.5 (71 mm) on a 23mm front rim. That's over a 3:1 ratio for tire to rim size. When I first saw the tire I'm like no way this is fitting, I'm going to have to buy a wider rim. Not so. Not only did it easily fit on, I've had zero problems with it in the last 8 months. I can go all the way down to 22 psi with a tube and no mushiness (over 20 psi), no rim strikes, no separation of the bead off the rim, nothing. A solid workhorse tire on the 'wrong' rim.

Maybe the more important question is: has someone on here put on a wide tire on a narrow rim and DID they have problems?

 

I have a very standard tire Maxxis 27.5" x 2.5 (71 mm) on a 23mm front rim.

That's odd because my 2.5 DHF II on a 30mm internal rim measures 61mm.

 

27-30mm seems ideal for the majority of mtb applications i.e. Trail riding...

The above should cater to 2.2 to 2.5 inch tires.

What about 2.6+? :meh:

Who needs em? The industry, that's who!!

:cha-ching:

'We'll all make it to the top... Some of us, might not make it to the bottom'

 

I used to hit rim, burp air and sealant with 2.3's on 29mm rims at 20 psi front and rear. Same tires on my current 21mm rims at same air pressure and ZERO issues. No rim strikes or burping. My 21's are way lighter too. Win/win. Drink the koolaid if you must.

 

Which makes absolute sense. However your tires now do not undergo as much deformation and therfore have less traction now. There is always a trade off.

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For me the exception to the rule is if you are running 26" wheels, the extra diameter provided by a big tire is more beneficial than sidewall performance. I noticed a big difference in bike ability when going from 2.2 to 2.5 even though my rims had no business running 2.5. The extra diameter was immediately noticeable for rocky climbs where the bike didnt get hung up on stuff as much, there was one obstacle I could never clear until I got 2.5's and suddenly my bike just rolled up and over it rather than coming to a dead stop.

On a 29er I dont like running tires that are too wide. I found 2.35 Schwalbe's on a 21mm rim too wide and even on a 26mm rim I wish they were a bit skinnier. I will probably try 2.3 Maxxis next.

 

I noticed the exact same thing on a 26" bike. For my 27.5" bike, going from 2.1 to 2.5 was nicer, more solid, no drama, an 'improvement'. For my 26" bike, going from 1.95 to 2.4 was huge. It was like a completely different bike. I went from out of control downhill and being forced to take every microtrack the 1.95 tire chose to actually going down the hill with some control. Rim size is only 19 mm (3.6x tire/rim width). Huge difference even if the tire is too wide for the rim. Lowering the psi from 35 to 25 helped a lot too.

BTW about that 2x tire width to rim width rule, it's actually not a rule:

https://www.bikerumor.com/2016/08/12/tech-story-match-bicycle-tire-width-rim-width-best-results/

"...with some calculations of the ETRTO standards, we came up with a rough guideline suggesting your rim width should be between 32% to 70% of the tire width. For a 2.8″ tire, that means rims with an internal width of 23mm to 49mm. Based on all of these conversations behind this story, our hunch is that the "ideal standard" lies near the upper middle of that range, so something like a 35-40mm IW rim would be the best starting point for safety, optimized performance and a good tire profile. Disclaimer: That's our math and opinion based on the charts and excludes the narrowest tire width fringes, so use at your own risk."

Also:

"It is primarily based on experience, testing, and feedback from our customers as well as the professional athletes we work with. The basics are that if you run a rim that is too wide for a particular tire you have a lot more issues with tire and rim damage, as the rim is much more likely to bottom out on lateral rock impacts causing tire or rim damage.

"Conversely, if the tire is too wide for a given rim, you get more tire roll due to the larger casing size and higher aspect ratio of the tire, which together create more leverage on the tire allowing the casing to collapse and roll over the rim during hard cornering."

They are basically saying it's a lesser evil to run too wide of a tire for the rim than to run too narrow of a tire for the rim. That 32-70% they referenced above for tire to rim width for a 2.8 inch-wide tire came out for them 23mm to 49 mm for the rim. My math (2.8 inches = 79mm) came out instead to 25mm to 55mm for the rim. However, I'm going to try a 26 x 2.8 tire and my XC rim is only 19mm wide (4.2x ratio) so I'll play it safe and buy a wider rim anyway.

 

Slightly OS, but what is the consensus on tire clearance from chain stays? I know depends on conditions, but for starters, let say 80% dry 20% muddy. Or another way answering, clearance on dry vs clearance on mud? Some assumptions 1) stiff wheels (carbon rims) 2) medium knobs (not DH) 3) Carbon frame.

 

I've ran tire clearance of a 1/8" on my chain stays for years without issue. But I run in dry conditions. In muddy conditions this could be a problem. Plus you better have a quality wheel that stays trued.

 

Yes, and a fine answer it is! :thumbsup:
I especially like answers that advance my agenda! :skep:

 

I was chatting with some friends about this. I told him my hypothesis about wide rims was more about people not being good enough to lean the bike over into the side knobs. So the wider wheels help get the side knobs into an easier position to reach, requiring less lean angle. They all agreed that it might be true. One is also a strong descender.

I'm racing XC with 2.35 on my 21mm wheels. My Enduro has a 2.6 on a 29mm wheel.

 

Actually from the pictures I've seen of the tires that are less than 1.7x tire to rim it's the opposite; the side knobs are gone and pointed up. I wish there was a thread dedicated to all of the problems with too narrow of a rim, and then too wide of a rim, or a poll, and then you could really see the real-world difference. I rarely read anyone complaining that their tire is too wide for the rim (in fact I can't remember ever reading that!!!), but there are several complaints on here about rims being too wide. Yes, there is some floppiness with a larger ratio like 3x tire to rim, but some people call that cushion. Cushion can be nice especially on a hardtail. It doesn't mean the tire is going to fall off or slide off the trail.

Conversely, I've seen many posts and some pictures with a wide rim where the tire's side knobs are gone, they are pointing up instead of out, the knobs are all crowded together, the rider says rolling resistance is annoyingly high, the tire wears out a lot faster, etc. It just does not look right. As for the wider tire on a standard rim, it's not really a bulb shape. It's more like an ice cream cone or hot air balloon shape; the sidewalls slowly and firmly grow out to the side knobs in a cone shape. It's not really as floppy as you may think if the tire is a heavy 2 lbs or so and the sidewalls are thick.

There is absolutely nothing to worry about, this is all rim manufacturer hype. Now if you actually tried a wider tire on a narrow rim and it sucked, please reply with exactly how it sucked, how riding was affected, so people can make a practical case for wider rims, instead of just taking everything as gospel from the for-profit bike industry. If the bike industry thinks you will believe something, they will simply add that to their sales pitch, whether it's true or not. The argument "The manufacturer recommends blah blah blah" is not an argument. We need to see real feedback from people trying vastly different ratios, 1.5x to 3.5x. If someone just tried 1.7x and never anything else, they would not know the difference. It may work fine to them but it's a different tire and rim than what they had before so there is no real experiment or conclusion.

 

Which Rockshox forks are 3 times as much as the comparable competitors? Fox isn't cheaper. Manitou is a bit cheaper if you look for good deals, but nowhere near 3 times cheaper. XFusion? Ohlins? DVO? If you're referring to Suntour or one of those Chinese brands, you're comparing apples to oranges, or at best red delicious apples to my daughter's plastic toy apples.

 

Tire and rim need to work together as a system. If a tire was designed for a 17mm rim and you but it on a 30mm rim it will probability suck. With that said 2.1-2.35 are much better on 25 then 17 rims. 25-30 is a sweet spot and 35+ needs a specific design or larger tire. I hope that 30-35 becomes the standard for all mountain bike tires from 2.2 to 2.6 it gives a good support and volume ratio without to much added weight.
LOL wider tires are only for newbs. Same thing for wide bars and dropper posts. I heard a rumor that all riders should start on full ridged too.

 

I heard a rumor that all riders should start on full ridged too.

It's way more fun to put 'very experienced' mountain bikers on rigids... :lol:

 

With that said 2.1-2.35 are much better on 25 then 17 rims. 25-30 is a sweet spot.

I disagree.

If I end up going to 2.6 up front I'll run a 25 rim instead of my 21 for it.

 

He actually said 25mm is better for 2.6, he agreed with you, or you agreed later with him. Getting my first 25mm front wheel in the mail today, WTB i25 CANNOT WAIT!!!

BTW 2.6 = 66mm / 25mm = 2.6x tire to rim ratio = FINE, not to beat a dead horse or anything. I agree 66mm / 21mm = 3.1x tire to rim ratio, not optimal, not the greatest, doable but floaty and I agree it's a bit much.

 

Car tires have a published recommended rim width range. I think it would be nice if MTB tires did too (a few do). I don't think it is just the tire size, but the tire design as well.

Stans has a guide on their website. They tend to go narrower on the rim width than what is considered the norm.

Anyway, here are a few I've tried:

Hans Dampfs 2.35s on i17 rims - very unstable on cornering.
Hans Dampfs 2.35s on i25.5 rims - whole new tire, could be drifted without dropping you.
Hans Dampfs 2.35s on i35 rims - Even more stable on corners. However IMO too stable at times, there was no sideways compliance, so it rode harder when leaned over on bumpy corners. Pressures could not be dropped further, because rim strikes were still the limiting factor. Also, sidewalls were exposed and wore out before the tread did. Rims were getting scraped too.

Dirt Wizard 3.0 60tpi on i35s - IMO the rim width was perfect for this tire. Due to the very heavy casing, there was no floppiness when leaning the bike over. Sidewalls and rim were very protected of course.

Nobby Nic 2.6 on i35s - Feels about right to me in this case as well. The casing is light, so there is a touch of squirm when leaned over at lower pressures, but not in a negative way. Sidewall wear is a moderate problem though.

 

I have an Enve XC wheelset with a 19mm inner with a Nobby Nic 2.35 tire and it feels great. I would have no problem putting a Maxxis Ardent 2.4 on this rim either. Sometimes I think people spend more time pontificating about a bunch of BS than they do riding. LOL

 

Totally^^^^^^^^

 

2.3 is better on 21mm than on 29mm.

 

Soooooo..... this rim WTB STP i29 TCS doesn't play well with Maxxis Tomahawk 27.5 x 2.3"?

 

 

Eight or nine out of ten people can't remember to properly air up their tires.
Is that the rim's fault or the tire's?

If you're trying to get the people here to quit thinking a set of ratios of the 'right' numbers in the 'right' places makes something ride well, good luck with that.

I'd say the proof of the pudding is in the eating of it, but I guess a successful theoretical argument of how the pudding is great works too on the interwebs.