Bushranger said:
Ok, I'm getting my Spec Epic Comp 29er soon. Just doing some research on setting it up.
I won't be replacing any parts until they wear out or break. (If it matters, I'm 173cms tall and weight 68kgs, race cross country endurance type stuff, 50 to 100k, not elite but competitive)
1. What tyre pressure should I use? I have ridden 26" bikes at around 40 to 45, but read reports I should have been around 35. I'm from a road background so not familiar with best pressures for off road. Should tyre pressures be different for 29" bikes. For example, the contact patch is already bigger on a 29" so does that negate the need for lower pressure to increase contact??
Pressures for off road riding are going to be so low compared to your road background, that you will be left scratching your head and saying "that can't be" when you compare the two. Off road on 29"ers pretty much puts you in a 20 - 40 psi range depending on a few things.
It all depends on the width/volume of the tire you are using. As well as the width of the rim. Wider rims allow for lower psi's and narrower rims usually need a bit more air to prevent squirm. The smaller volume 29"er tires (1.8's, 1.9's) tend to require a bit more psi to avoid squirm than the larger volume tires. I'm taller and heavier than you and will usually run the smaller volume race tires in the 24 - 28 psi (tubeless) range. Larger volume tires usually are in the 20 - 26 psi range (tubeless). Again, depending on tire, terrain and conditions. If running tubes, all of those psi's get bumped up just a bit (2 - 7 psi) to avoid the dreaded snake bite. I usually ran everything around 30-32 psi when I used tubes with no problems whatsoever - except for thorns. In addition to the ride being so much better tubeless with traction, cornering, rolling resistance, the fact that I don't have to deal with thorns any more leaves me in a position that I don't even consider tubes (although I've got a box full of them).
Bushranger said:
2. What about pinch flats on 29ers? If you can run higher pressures does that then mean you don't get pinch flats as often so therefore there really isn't a need for tubeless tyres on a 29".
If you're running higher pressures, you're not going to have to really worry about pinch flats. Your new FS bike is going to absorb a lot of the terrain with the suspenion working to keep your wheels glued to the ground, but that doesn't mean the best solution is to run high pressures in the tires. You don't want the tires bouncing along and you fighting for traction with over-inflated tires. Running in the 40's will leave your tires feeling hard/harsh and your traction will suck.
If it were me and that bike, I would go directly to tubeless. Do not pass go. Your Epic comes with a tubeless ready Captain and Fast Trak. Get the rim strips, convert them and you will not go back to tubes.
Supple performance and handling. Traction galore. It's all worth it - trust us.
Bushranger said:
3. There is a lot of info around on 26" tyre pressures and combo's etc but it will take a while for similar database of knowledge to build up with 29". So if anyone can assist me on my path of discovery, point me to some good articles etc I'd appreciate it.
This subject was actually quite a frequent topic back in 2003, 2004 and 2005 as many on this forum were just getting into 29"ers and wondering about tire pressure on the big wheels. I posted several times wondering about tire pressures and pretty much always got the same response. The usual consensus at the time was that you just have to get out on your terrain, with your riding style and an air pump and gauge until you dial in what works on the front for you and what works on the rear for you with each tire you own. There really isn't any other short cut - such as a database. What works for you - may not for another. If you stick with tubes, just experiment as to how low you can go before getting a pinch flat, but still retain good sidewall support and no squirm.
Here's an example of me running a similar bike design to your new one (4" travel full suspension race/endurance bike) with 1.9 Kenda Karma's tubeless. The front tire is 22 psi and the rear is 24 psi. That's about as low as I'll go tubeless with the smaller volume tires at my weight, but they do well in the mid-20's on the wider (28-29mm) rims. Notice that even at that low weight and my 180 lbs. aboard - the sidewalls do not appear to be bulging out like an under-inflated tire. Great traction, cornering, rolling resistance, thorn protection, etc.... .
That'll leave one scratching their head from a background of running psi's over 100+ lbs. on the road. But it is true, I run most everything in the psi of 20's since I run tubeless, wider rims, etc... .
Best of luck experimenting and getting used to it all.
BB
