[HacksawReynolds]

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.

 

[tuckerjt07]

And most amateurs wouldn't know what's good for them if they were beaten over the head with it. The continued popularity of RockShox forks, Stan's rims, and Hans Dampf tires is proof of this.

Then it logically follows that they would not know what was bad either. Ergo, unless your name is Gwin, Minaar, Hart, Bruni, etc., you've just refuted your own argument. Excellent work. [emoji106]

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[tuckerjt07]

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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[HacksawReynolds]

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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Traction, that I can tell from riding hasn't been any worse. I mean it's a 29er at 20psi. If one is having traction issues with that setup one must look at their riding technique and not their equipment IMO.

The tire profile is much better with my 21's than with my 29's as well.

 

[tuckerjt07]

Traction, that I can tell from riding hasn't been any worse. I mean it's a 29er at 20psi. If one is having traction issues with that setup one must look at their riding technique and not their equipment IMO.

The tire profile is much better with my 21's than with my 29's as well.

You would likely only notice it if you were regularly flirting with the limit. However, there will be less available traction due to the fact you made the system less supple.

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[aerius]

Then it logically follows that they would not know what was bad either. Ergo, unless your name is Gwin, Minaar, Hart, Bruni, etc., you've just refuted your own argument. Excellent work. [emoji106]

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And that is why the bike industry refuses to progress and continues repeating past mistakes. Which is why better riders such as myself have a hard time finding stuff that doesn't suck.

 

[tuckerjt07]

And that is why the bike industry refuses to progress and continues repeating past mistakes. Which is why better riders such as myself have a hard time finding stuff that doesn't suck.

Or, idea, maybe you aren't as good as you think you are. You've already said that you have no way of knowing if something is good or bad so...

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[HacksawReynolds]

there will be less available traction due to the fact you made the system less supple.

Less supple maybe, but far more functional/reliable.

 

[idividebyzero]

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.

 

[richj8990]

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.

 

[Fleas]

...

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. ...

Ha ha :lol:
That's a difference of over 100%!
I see how these guidelines work: Do whatever you want.

-F

 

[richj8990]

Ha ha :lol:
That's a difference of over 100%!
I see how these guidelines work: Do whatever you want.

-F

Exactly. That link is really informative: https://www.bikerumor.com/2016/08/12/tech-story-match-bicycle-tire-width-rim-width-best-results/

You know what's embarrassing, I've been using 28.3 as an inch/mm conversion and forgot it was 25.4 and not 28.3 (28.3 is ounces to grams). DOH! This is what happens when you don't work in science for 9 years, brain mush.

These are all general guidelines in the link's discussion. Anything up to 3x tire width to internal rim width is probably fine. You can go above 3x but I for sure would not go over 4x.

BTW for anyone who still thinks that going over 2x the tire width compared to rim width is bad:
after spending hours looking at 26" rims yesterday, I guess it was not a total waste of time because I learned the standard internal rim width is 19mm, or 559 x 19. The standard tire width is 26 x 1.95. 1.95 x 25.4 = 50mm. 50mm / 19mm = 2.6x tire width to internal rim width ratio. So above 2x is NORMAL.

My Maxxis 27.5 x 2.5 (64mm wide) is on a 23mm internal width rim = 2.8x = OK

My (off-brand?) CST Rock Hawk 26 x 2.4 (61mm wide) is on a 21mm internal width rim = 2.0x = OK.

After looking for hours and hours yesterday online trying to find a reasonably priced 26+ wheelset, and not finding it, then...taking the same wheel above, adding Maxxis 26 x 2.8 (71mm wide) / 21mm rim width = 3.4x, over 3.0x but still under 4.0x so worth trying.

According to the link, if you have a tire over 3x the internal rim size and you take corners aggressively, there is a chance that the outside of the tire can fold over the rim and may cause a pinch flat or worst case the tire may even start sliding off the rim. So aggressive riders should not go over 3x tire to rim width. I don't really do that so hopefully I'll be fine and not end up flung off the trail corner lol.

Last but not least, tire height (or length, as will be mentioned below) is important too for many reasons, including if they fit on your bike; it's not just width that should be measured. I see a lot of discussion now about 29 vs. 27.5+. A 27.5 x 3.0 tire is just as tall as a 29 x 2.3 tire. And you are getting 0.7 inches wider for the tire, same height = winner. So to me it's a no-brainer, go 27.5+ if you can. But if you have a stock 27.5" bike there can be problems...

Going back to the 26 x 2.8 tire I want to put on my bike; there's one little problem: it won't fit under the fork arch. Right now it has the aforementioned 26 x 2.4 tire, and the space between the top of the tire and the fork arch is only 0.4 inches. If you take the 27.5 x 3.0 being as tall as the 29 x 2.3 tire, then 0.7 inches wider = 1.5 inches higher, or 0.1 inches wider = 0.215 inches higher. Remember this ratio: 0.1 inch wider = 0.215 inches higher / longer. If I go from 2.4 inches wide to 2.8 inches wide, then a 0.4 inch difference in width = 0.86 inches higher. That's 0.46 inches above the bottom of the fork arch = cannot fit. So I'll have to get a 27.5" fork on the 26" bike to make it fit (and that's not the end of the world, sorry 26" purists).

The same issue applies on the back of the bike. It's not necessarily the width of the tire clearing the triangle and not hitting the chain. It's the length of the tire hitting the back of the front derailleur if you have a 2x or 3x drivetrain. 1x maybe no issue with a wider tire, 2x or 3x = major issue. Right now I have a 26 x 2.25 inch tire on the back and it's only 0.25 inches away from the front derailleur. I can't go 26 x 2.4 on back because 0.15 inches wider = 0.32 inches longer, and rubbing into the front derailleur in the 1st chainring = cannot do. Similarly, I have a 27 x 2.35 inch tire in back and again it's 0.25 inches from the front. If I went 27 x 2.5 then 0.15 inches wider (again) = 0.32 inches longer and rubbing into the front derailleur again. So gentlemen it's not just girth that matters it's length too.

 

[Rider51]

I see how these guidelines work: Do whatever you want.

-F

Exactly.

There are so many factors that come into play, so many different rim types, tires, frames, hubs, etc. that it's virtually impossible to generate any sort of true "guideline".

You want your own guideline? Take your bike with your wheels, into your LBS with a mechanic you trust, and ask them to show you just exactly what they think, what tires will work with your bike, for your kind of riding and terrain, and why.

 

[Simplemind]

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.

 

[DIRTJUNKIE]

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.

 

[MSU Alum]

Slightly OS, but what is the consensus on tire clearance from chain stays? I know depends on conditions...

There's your answer.

 

[Simplemind]

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

 

[Sidewalk]

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.

 

[Zowie]

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.

If you can't break a spoke, you can't have fun...

 

[richj8990]

And most amateurs wouldn't know what's good for them if they were beaten over the head with it. The continued popularity of RockShox forks, Stan's rims, and Hans Dampf tires is proof of this.

LOL I was wondering about that too. I'm a beginner and all three of those names above are often twice as expensive for what the equivalent product is from the competitors. I just go with what works. Who cares what brand name is on your bike if the goal is to have fun. Some guys even buy a $3 Rock Shox logo off e-bay to stick on their off-brand fork. What a joke.