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    • tod

      Seems like the biggest debate in mountain bikes for trail riding (versus cross country and downhill) is the choice between 29 and 27.5 inch wheels. I have recently demo'd several 27.5 bikes and I own a 29er Stumpjumper so have been able to compare a bit. I find both are great and have their advantages. The 29er is known for rolling efficiency and straight line power. The 27.5 is considered more playful and fun. I have found a key factor on performance of either is tire width and tread. Either build with a narrow tire and poor tread does not ride well. Said differently, a nice tire width and tread can make a big difference. Many bikes come with a tire width of 2.3 and now plus sized tires come with 3.0 inch tires. I find the 2.3 is fast but a bit narrow and the 3.0 provides a great ride but a bit soft around turns. I have talked with many in the bike industry and the feeling is the tire widths for trail bikes will settle in the 2.4-2.6 inch width. I recently put a Maxxis DHF Minion 2.5 (photo below) on my front wheel and it is sweet. It is not fast uphill but provides great traction and confidence downhill. I run a 2.3 on my back tire for better rolling and lower weight. Mountain bike gear is ever evolving so it would be great to hear what others are experiencing.

    • VilTri

      I guess it really depends on the kind of trails you ride. For less technical trails with climbs 29" is perfect. But for trails with steep technical downhill and tight cornering 27" is better. As far as tire width I find 2.4s DT tires as a sweet spot anything above that just feels too sloppy.

    • TriGeek

      I've mostly focused on Xterra (Mountain Bike Triathlon) have raced a couple of courses. I found 29" wheels to roll faster and being agile enough. My current setup is 2.35 Maxxis Ikon tubeless tires (22psi front and 24psi rear). This setup has seen some gnarly local trails at Demo Forest and handled them really well. So in my opinion 29 is the way to go. However, for trails like at North Star and occasional downhill sessions, I would go with 27".

      Here is my current winning setup:

    • VilTri

      Nice bike @TriGeek. To me it seems like a cross between a true XC and a trail bike. So it makes sense why you like running a 29 inch wheels with 2.3s on them. When it comes to XC racing 29s are a no-brainer.

    • tod

      Sweet bike. I agree tubeless is key. much better grip. I use the same tire pressure. For speed, no question, 29er and 2.3 tires.

    • Fer0z

      I usually end up riding on roads for a few miles to find trails. I'm wearing through my knobby tires pretty fast. Is it going to hurt my traction a lot if I went with a less aggressive tread pattern next time? I never ride in the mud.

    • tod

      All depends on the type of dirt riding you do. You do not need knobby tires to ride smooth XC trails. In fact, there are XC tires out there with very smooth roll and they are great. But, you do need knobs in more technical terrain for traction both up and down the hill. I have found much better climbing performance on rooty, rocky trails with my more aggressive tires. And, I am clearing technical down segments with my big tires. But it is totally unnecessary to carry this extra weight around if you are smooth trails. So, like most stuff, it all depends.

    • cvdavis

      I still use 26" wheels which are lighter, stronger, accelerate quicker, have quicker handling...

    • VilTri

      The other day I've had a chance to ride my 29" inch bike for a bit and then jump on my 26" bike right after. Despite having a slightly different geometry of the bikes with comparable suspension travel (5.5" vs 4.75" front and 5" vs 4" back) I still noticed a big difference in terms of rolling speed. I did feel like 29" wheels were rolling faster but were less nimble when turning.

    • cvdavis

      Yes the bigger the wheel diameter the better the rolling speed. Every wheels size has advantages and disadvantages. The best choice would really depend on the type of terrain you ride on, the type of rider you are and your weight. People also adjust their riding style to different wheel sizes so they often have the best experience on the size they are most familiar with. I'd say riders 5' or under are better off generally with smaller wheels but other than that it depends on what aspects of the ride you favour the most (tire traction, rolling speed, bike agility, wheel strength).

    • cvdavis

      I agree with what Vilen said except that when wanting to go FAST downhill I've used a 2.8" on a 150mm fully suspended bike and that tire hooked up so well and provided such cushioning that you could go faster than you should even want to go. I used to race A class dirt bikes in Minnesota and know what fast is ;) I'd never use a tire that big on my cross country race bike but if the goal is to go kick azz fast downhill then bigger is better. Tire pressure would of course be an important consideration to prevent the sidewall rollover Vilen was talking about. You can also use a tire foam insert to help hold up the sidewall when running lower tire pressures while tubeless. I run tubeless and I assume most of you guys do too. If not then that would be an area for big performance improvements to be made. So I guess when all is said and done I agree with Vilen on all points unless you are talking 150mm fully suspended down hill screamer runs.

    • cvdavis

      I said I use 26" but generally speaking that's NOT what I'd recommend someone to get. If you do open and smooth trails then I'd say go 29". If you do a variety of trails with very tight and technical single track and also lots of gnarly sections then I'd go 27.5". If you do ridiculously crazy tight trails with lots of climbing and tend to destroy wheels on a regular basis and value nimbleness over rolling smoothness then go 26". For the most part I would not recommend 26" simply due to the lack of availability and support for that wheel size at this time.

    • cvdavis

      I have four friends that have that same bike minus the fork. They absolutey love it.

    • VilTri

      Thanks for sharing the link!

      It is hard to argue with the results as this is probably as close to a "real world" testing rather than "lab" testing you can get. I completely agree with wider tires providing better traction overall and especially during climbing.

      I'm wondering if I should experiment with slightly lower tire pressure? 🤔

      Currently I'm running 22 psi on the front and 24 psi on the back (2.35" tires front and rear) so maybe I should try 20psi front and 22 rear. I weigh in at 145lbs and the bike is 24.5lbs. I'll try this on the next ride and will report back.

    • cvdavis

      I'm assuming you're running tubeless in which case I'd say yes try to run your tires with less pressure. When I use tubes I test ride my bike with lower and lower pressure until I start getting pinch flats (I carry extra tubes on these test days) then go up 1-2lbs depending on the trail conditions. With tubeless I run the lowest pressure that doesn't feel mushy. By mushy I mean you can feel the tire roll over on its sidewall during fast/aggressive turns. At your weight I think you're probably running your tires a bit high. If you're not tubeless then go tubeless and get impressed. If you're tubeless and start experiencing burps then go with more air or different tire and rim combination. You may also start feeling your rim hit the ground in which case you'd want to run with more air pressure.

    • VilTri

      Awesome advice, Cory! I am running tubeless and plan on sticking with them for the foreseeable future. Recently I’ve started carrying a mini pump with me in addition to CO2 (for emergency repairs), so I should experimenting on the trails with different air pressures.

      A couple of weeks ago a was descending and hit a rock with my back tired which caused it to burp (loose air and reseal). After that it felt like it was “folding“ while cornering. Fortunately, one of the riders had a handpump and I pumped it back up to finish the ride. Didn’t want to use a CO2 just to pump up the tire. Now for the next ride I’ll just take the preasure gauge and a mini pump.

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