2.2 or 2.4 Specialized Purgatory front tire?
I have a tire question for you. I’m running Specialized Purgatory 2.2 rear, tubeless and low pressure (~20-25 psi) and it kills for traction – best tire I’ve run so far. My terrain is New England trail and traction is really a major concern (wet, loose, shaley, slippery, you know what I’m talking about) – outside of rider skill, traction is typically the number one factor for cleaning a section or not.
So the question is about what to run up front. I would like to try a 2.4 Purgatory, but, this is trail riding and I guess I wonder if 2.4 would be overkill? I’m not racing but I don’t want to have to deal with pushing a ton of extra rolling resistance (I am assuming a 2.4 would have more rolling resistance than a 2.2). But, like I said, the ability to keep momentum via cleaning sections is huge and ultimately perhaps outweighs (sic) the weight penalty and rolling resistance of the fatter version? What do you think!?
Random second question – will you thrash a Stumpjumper FSR 29’er anytime soon?
The Specialized Purgatory is a set-it-and-forget-it trail tire. The exposed side lugs get good cornering bite. The shoulder lugs make the tire feel consistent and predictable.
Thanks for writing.
I’ve spent some time on 2.2 Purgatories, and I agree they’re nice all-around trail tires. Pretty light, pretty fast, pretty good traction. I hear great things about the 2.4s, especially on 29ers.
If you want to switch from a 2.2 to a 2.4, consider:
Space – Will it fit in your fork? What about if it’s caked with mud?
Weight – Heavier, yes, but when you consider all the factors — bike weight, rider weight, terrain, etc. — that won’t significantly impact your pedaling output. Heavier tires have more rotational stability, which is probably a good thing in your conditions.
Tire pressure – A larger tire would let you run even lower air pressure, which would give you even better traction in the loose/rough/slippery stuff. If you tend to ride light and straight, that’s all benefit. If you tend to pump turns — braaap! — the tire might wallow and burp. If you’re going to run the same pressure as your smaller tires, you give up some of the larger tire’s benefits.
Rolling resistance – Definitely slower on smooth surfaces, but that’s not where you ride. On rougher surfaces, bigger tires (with proportionally lower air pressure) tend to roll faster than smaller ones.
Slackness — A bigger front tire will slacken your head angle. Not much, but it will make your bike a touch more stable in the gnar.
Confidence — The most important factor. Having a big meat up front makes you feel tough. Like you can handle anything.
I say give the 2.4 a try.
RE: The Stumpy 29er. I think that would be a heck of a trail bike. Let me see if I can borrow one …
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Can you explain why a larger tire ‘rolls faster’ than a smaller tire on rough surfaces? I can see why it would be more stable and confidence inspiring, but I’m not sure how it would actually roll faster for a given energy input. Thanks!
I think a larger tire will roll faster over rough terrain mainly due to the lower air pressure. The softer tire will be a bit more forgiving than a smaller tire that requires a bit more air pressure.
Think of it like a full suspension bike vs a hardtail. The full suspension bike will soak up more of the bumps and keep more forward momentum while the hardtail gets knocked around (upward and backwards) more when it hits bumps.
Well, that’s my best guess anyways.
Yup, that’s it.
A bigger tire (but only with lower air pressure) will absorb small bumps rather than convey them to your bike or body.
The better you insulate your bike and body from bump energy, the more speed you carry.
Thanks Lee and everyone for the input – I’m giving this a try and will try to report on how it went. It’s going to be a bit tight on the F-series fork, but it’ll work I think!
And, this is for my 26; I will definitely try the 2.4’s for my 29 as well. It should feel like extra suspension I think.
thanks again Lee, and can’t wait to get version 2.
RE; rolling resistance.
Tire pressure was one reason for lower rolling resistance, but at the same pressure a wider tire will still roll better, even on smooth surfaces. This was the conclusion of several studies in the last few years. There is a thread about the Bike Magazin/Schwalbe one on Lee’s site a while back. There was also a Continental test implying the same thing with road tires, 25 vs 23. The wider tires contact patch is shorter, meaning the tire doesn’t have to ‘dent’ in so far.
Oh yeah! Awesome.
I can’t find that article, but here’s some of the data:
Also, just for fun, check out: