Some more newbie questions
I got a 29er HT about a month ago and after a few rides have a few questions.
1) Its a 27 spd but I've read that you shouldn't run the big front sprocket with the two biggest rear sprockets; likewise also not to run the small front with the two smallest rear sprockets. This I'm told causes 'cross chaining'. Is this true? And if so this bike doesn't truly have 27 usable gear ratios.
2) How much air pressure should I run in the tires? They are continental race kings(I think) with tubes. I have been running them at 40psi and mainly riding on roads and paved paths so far. I'm guessing I'll want to air down a bit for more dirt/trail riding.
3). When riding I try not to shift under load and have managed pretty well except for when climbing up hills, I can't shift faster than I lose momentum which makes for a rough shift. Any way of making these smoother? (I'm guessing this will take time and practice to get shift timing just right)
With regard to the gears, it is not recommended to run the extremes (large chainring and largest rear gear for instance) as it puts a fair bit of sideways strain on the chain.
However the bike will do it, it won't fall apart if you run these gears. It is just better to use a different combination.
Tyre pressures off road l use about 30psi, this will give a softer ride but too low will make them more prone to punctures. Others will have their own views on tyre presure, l asked the same question myself for my hardtail and 30psi seemed a good compromise.
The rear cassette will change up or down under power, it is better if you can back off a little but it is not always possible, such as when climbing. Both my Cube and my Kona would change up or down while climbing out of the saddle.
On the front chainset you have to back off or it won't easily change, this can be tricky half way up a climb when you want to go into the small front chainwheel! But neither of my bikes would change front chain wheels unless l backed off while
But don't stop pedalling completely of course!
Some more newbie questions
I'll try running 30psi just to see what the difference is.
Originally Posted by lotusdriver
It is always possible. Modern drivetrains will shift under full load but this is how broken chains are born. Decide what gear you want before you get to the steep part, if you get it wrong you can still ease up for a nano second while you downshift. I have done this on very steep climbs.
27 gears it has no body said 27 ratios. You'll probably use only a few as you are the biggest variable power source.
I run 20psi front and 25 rear with tubes(26 2.1-2.5 for my 29 tires.
You don't want to snap a chain in the woods, so don't shift under full power.
That is what l meant in my post, do not try to shift the front chainset without backing off.
However l have on occasion shifted the rear chainset under full power, almost always into a lower gear, and have never snapped a chain.
all the important stuff has been covered. here's a tidbit that will help you sound like a super cool MTB veteran.
Originally Posted by Tbone77
instead of total gears, e.g. "27 speed", refer to the drivetrain in terms of chainrings x cassette cogs. For instance, you do not have a 27 speed...you've got a "3 x 9"...
yes, it is the same thing...we can all figure out exactly what you are saying in an instant regardless of the terminology...but now you can sit at the cool kids' table!
"The bitterness of poor quality remains long after the sweetness of a low price is forgotten." - Benjamin Franklin
If you look at a gear ratio chart a 3x9 really has about 20 differrent ratios .For example the middle ring and ninth is almost the same as the big and sixth .You can find more info on the Sheldon Brown site.
If you plan on doing any serious trails dump the big ring for a bash guard, it will glide over rocks and logs alot easier than that big tooth chain ring.
Your bike should be able to handle running in big rig/big cog, it just stresses the chain and pulls the rear mech a little more; don't make a habit about doing this thou. A bash guard may be a good idea if you ride over logs and your big ring hits them, if they're not tall enough keep it if you use it.
To prevent broken chains try not to shift under heavy load (climbing).
Tire pressure; ridding style, terrain and comfort will factor here. Try 30psi and see how you like it, lower pressures allow better traction and comfort but could be prone to pinch flats, too much psi's and the ride will be harsh but quicker; having said that I ride 30f/40r (with tubes) and haven't had a flat in a couple seasons mostly because there are no thorns or big rocks but plenty of roots where I ride.
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