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Trialdog

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Discussion starter · #1 ·
I need help understanding a few things about running 2.1 or 2.35 tires on the front. Lately I have been switching between the two sizes and don't quite understand the results I seem to be getting.

I ride in Southern California mostly XC trails. A few rocks here and there but I would say XC. It sure seems to be getting drier and drier so lots of loose dirt/sandy conditions. And I would say I'm more of an XC rider more than anything else. After numerous rides on the same trails, I seem to prefer 2.1 tires over 2.35 tires. The tires I have been using are the Specialized Adrenaline 2.0(worn) vs. the older Specialized Resolution 2.2(new). So exactly the same tread just one bigger and one smaller. They both actually measure bigger and come out to be about a 2.1 and a 2.35. Two other tires are the Kenda Nevegal DTC 2.1(maybe 1/4 worn) and 2.35(new). Both seem correctly sized. My rims are the Mavic 117-not tubeless. I have tested all the tires at 35psi and 30 psi on the same trails. For some reason the 2.35 tires always seem to slip more and not feel as stable. I seem to like the 2.1's over the 2.35's in either tire. All seem better at 30psi, but that makes sense. So, my main question would be if all things are the same, why the heck wouldn't a fatter tire perform better? So also comes a few questions.

1. Do my rims have anything to do with not handling a fatter tire better?
2. Could it be that the 2.1 tires, with the smaller knobs, be the reason why they are sticking better. And if so, could them being worn have anything to do with it?
3. Should I be running the 2.35 at an even lower pressure?

This is all just for the front. For the record, I have run the Adrenaline 2.0 and the Nevegal 2.1 DTC in the back and I definetly prefer the Nevegals in the back. But so far, and I'm probably in the minority, I seem to like to Adrenaline's better in the front.

But again, if all is the same, why wouldn't the 2.35 perform better for me? Any help understanding tires would be awesome.
 
For XC type riding i too prefer the cornering bite of 2.1 tires. They seem to transition over faster and intiate bite deeper in the turns.

But for trail riding i like bigger brakes and bigger tires. If i screw up they can really save your arse. In rock gardens the bigger tires also seem to deflect less.
 
Trialdog said:
1. Do my rims have anything to do with not handling a fatter tire better?
2. Could it be that the 2.1 tires, with the smaller knobs, be the reason why they are sticking better. And if so, could them being worn have anything to do with it?
3. Should I be running the 2.35 at an even lower pressure?
It may be that your rim is a bit too narrow for the 2.35 tire. It makes the tread surface curved and reduces the amount of side bite the tire has.

You could probably lower the air pressure in the 2.35 a bit more. How much depends on how much you weigh and how/where you ride.

If the 2.1's are working for you, I'd say just ride them. No sense in pedaling the 2.35's with the extra weight and rolling resistance is they don't offer any improvement.
 
DM-SC said:
It may be that your rim is a bit too narrow for the 2.35 tire. It makes the tread surface curved and reduces the amount of side bite the tire has.
I agree with the above. The narrow rim would cause the bigger tire to have a rounder profile than intended, moving the side knobs higher up, and it could be than they're barely contacting the ground, not enough to get a firm bite out of them, except when in more extreme lean. A bigger front tire is a popular set-up for trail riding, and it should have better grip than a smaller one. If your rim is on a really narrow side, I'd say that's the reason it isn't working for you.

Arek
 
I would tend to agree...

Every tire I've ever run over the years I've had to experiment to find the "sweet spot" when it comes to inflation pressures vs. handling, and resistance to pinch flats. Tire pressue can be a biggy. All a happy compromise of course. What I've also discovered is that a wider tire doesn't always perform better than a narrower tire. And it can be directly related to tire width, rim width, and the tire profile. With a square profile tire you can generally run a wider tire on narrow rims with good results and often the wider versions will be better. Because the narrower rim forces the tire to have a rounder profile. With round profile tires the narrower versions usually peform better. It all has to do with the contact patch (the knobs that are in contact with the trail). With cornering it has to do with how quickly the transition is from center, to transition, to shoulder blocks. With wider round profile tires on narrow rims you force the tire to be rounder than intended and effectively increase the distance between edges of the transition and cornnering knobs and the distance they sit from the trail at a given pressure. Lower pressure can compensate to some extent for this, but only in a limited way.

My current set up consists of Nevegal 2.1's front and rear mounted to Mavic 719 hoops. Very similar to your 117 as far as rim width goes, the 117 is 17mm wide bead to bead, the 719 is 3mm wider. This combination is excellent, a bit slow rolling, but traction is outstanding and the set up cornners like it's on rails. I've tried the 2.3's and they do tend to wash a bit sooner when cornnering hard. With that said a friend of mine runs the 2.35 Neveys on Mavic 729 hoops, he's a big boy 250lbs. I've ridden his set up a couple of times and can't see any difference in pefromance from my rig.

So yeah, I'd say what you are seeing is either directly related to your rim width and tire width. Or it's at least a heavily weighted contributing factor. There are others that certainly make a difference as well, tire pressue, riding style, terrain, trail conditions, etc. What would be interesting would be to beg, borrow, or steal something like a set of 321's or similar and see what kind of difference it made.

Good Dirt
 
I run 2.35 Fat Alberts for technical trail riding where cornering isn't an issue. They are very solid performers that keep me from flatting and give me tons of confidence on the scary sketchy technical trails. I tried these same tires on real fast XC trails and they did wash out sooner. They weren't terrible but I didn't have the confidence in the corners that I wanted. So I put on my Maxxis Crossmark 2.1 tires and they railed amazingly. I was quite impressed at how they stuck in the corners and how reliable the traction was. I had much more confidence with these tires on the XC stuff. When I tried these tires back at home on my tech trails I felt like I was going to break my rims. Different tires for different riding. If you're riding XC and your 2.1's are studly keep them. Hold onto the 2.3's for the beefier trail days.
 
Discussion starter · #7 ·
Thanks for all the help and opinions. Sounds like it could be rim related. Thats ok. I will be playing with the pressure more and maybe that will give me more confidence in the 2.35's. 30psi works great for the 2.1's and pretty good for the 2.35. I 'll lower the 2.35's a bit and try that. Off course I have more 2.35's than 2.1's at the moment but thats ok. Better to have more tires than not.

Just by chance does anybody have the results from the tire shootout that Mountain Bike Action put on about 2 years ago? I believe it was the September 2005 issue. I can't seem to find anything on the web. Alls I know is they liked the Specialized Roll-X and Nevegal.

Thanks again for all the responses. You guys are great.
 
Keep in mind that the MBA tire test was done in SoCal terrain and biased toward XC type riding. At least that's the way it seemed to me.
 
Discussion starter · #9 ·
It just so happens thats perfect. I live in SoCal and I'm pretty much an XC rider. Being that, I'd love to see what the results were. But thanks for the heads up DM-SC. I'll do a separate post because I'm way curious.
 
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