clickagent75

...is my bike to blame?

So I have a 21-speed x-mart dual-suspension bike (I know I know, but its just to see if I will stick around with the sport). A buddy of mine took me on some mild singletrack terrain (roots, bunny hops & worn logs).

While riding we encountered a handful of logs along the trail. He took them with ease on his $3K Brodie DH bike, while I had trouble getting over them with my rig. I have 3 chain rings and the bottom of the largest one kept scraping the log as I tried to roll over them.

Is it just my techique? Or is it b/c I have 3 chain rings as opposed to my buddies DH bike which had only 2? His largest ring is about as big as my 2nd chain ring.

Any pointers? Or should I hold off on singletracks until I get a more capable bike?

madbiker555

This is almost exactly the same as my friend with his x-mart hog, (except he just plows straight into the log as opposed to lifting his bike over). I wouldn't trust doing singletrack with an x-mart bike, but you could remove the third ring. Or get a bash guard, but that would mean taking off 1 chainring anyway.

notfred

He probably can't remove the third rind or get a bashguard. All three rings are riveted together on most x-mart bikes.

clickagent75

Hmm, worth looking into as I don't even bother shifting into the 3rd ring.

My drivetrain is using Shimano parts so hopefully their not welded together.

Any tips on technique for riding over logs?

badsac

Momentum

LowCel 

I've got three rings on my bike and I can get over most logs without any problem. It just takes practice. This was your first time out, don't expect to be able to clear everything immediately.

There is actually a thread on here with pointers on log crossings. Just do a search and you will find some great information to help you out with them.

OldMBZip

Ditto what Badsac and LowCel said....momentum plus a little technique that will come w/ time. There's no reason any "Mart" mtb bike shouldn't be able to clear the log. It may be a little heavier but even an entry level bike should be able to handle that. Keep it up and just think how easy it may be one day if you do upgrade!

Brad01

You might want to try this: Find a log in you woods and drag it somewhere open and flat.
Then practice getting over it until you "get it" and next ride, then impress your buddy next ride.
That's how I learned balance, bunny hopping, and log clearing. Trails are much more fun now.

Stubacca

The BB on the X-mart bike might be lower than on a 'real' MTB. It's not designed to take off road, so the designers probably didn't build it to clear logs.

zx108

i just need to ask one quick Q: what ring is better for pedaling, i think it is the larger one because the road bikes have pretty big ones.

mach_5

i have a Q also. when you all talk about going over logs what are the to ways? i know you can bunny hope them, but what about lower speeds? do you just lift up the front wheek and let the back just hit the log or are you fast enough to be able to land the front wheel and some how lift the back. can someone explain the part of "push" or is it "pull" the rear wheel over.

zx108

you pull up and get your front wheel on the log, then you push your weight towards the front of the bike while pedaling, this propels you over the log.

Jaye

Lift the front tire over and then just pedal through the log if it is a reasonable size your back wheel should pedal right over it.

mach_5

thank you for clearing that up zx108 and jaye.

zx108

no problem, happy to help.

Stubacca

Depends on the speed and the terrain.

The chainrings on my MTB have 44/32/22 teeth (44 hardest, 22 easiest). The cassette is 11-32, so has 11-12-14-16-18-21-24-28-32 (11 hardest, 32 easiest).

For general XC terrain, I spend most of my time in the middle (32 teeth) ring. You can use most of the cassette range with this chainring, so can go for 32/12 combo for higher speed flats/descents and right down to 32/28 for short climbs (I try not to use the two most extreme combinations). When riding fast, smooth descents or on hardpack/asphalt, I might use the biggest chainring (44 teeth). For steep climbs, sometimes I'll use the smallest chainring (22 teeth). It's all about choosing the right gear for the terrain - too high a gear and you won't be able to move the cranks, too low a gear and you'll be spinning like a madman and going nowhere!

Road bikes have bigger chainrings than MTBs, because they average a higher speed (mine has two - 50/34. Some use 53/39. Some bikes have three (52/42/30)). However, a lot of riders only use the largest chainring when riding down a hill - the rest of the time they're using a smaller, more appropriate gear for the terrain, and using a higher pedalling cadence. Using the biggest gears all the time is known as 'mashing', and tends to tire out the legs faster since you're pushing hard with the muscles at a low speed.

For a road bike with a triple crank, you'll generally use the 52 for descents and high speed cruising, the 42 for flats and mild climbing, and the 30 when the road really gets steep!

zx108

ok, next time i go i am going to not use the higher one and see how it is. i ask this because i am thinking of getting a bash guard, which means taking off the bigest chainring.

Maelstrom 

And then there are those of us who don't use a big ring. The terrain here is steep enough to not allow much pedalling UP in a big ring and technical enough where a bashgaurd is worth its weight in GOLD!!!...I will lkely never use a big chainring as long as I live here. No real point to it

clickagent75

What's your clearance (in inches) from BB to the ground?

Gonna measure mine when I get home.

Stubacca

Specs say 11.9 inches (Klein Attitude, size L (19")). Not sure if that's from the bottom of the BB of from the center of the BB. I suck at logs, but I haven't had issues with clearance, Clarance.

Brian

We've got an E thirteen for the tandem, but I'm not installing it until we can get a slightly bigger middle ring. I can do without the big ring if I had a 38, or even 36. But the 32 is not enough top gear for us. That would save me from making the swap when we're doing a long road/fire trail ride.

Oh, try going over logs on a tandem. I want to strap some split heavy PVC to the boom tube, and just go for it.

jc1

I assume this is the same for even the high end components but shifting in the rear is much smoother and quicker than shifting in the front. I find I stick with the same front gear and use the rear gear for adjustments as needed when riding, shifting the front gear only when I am about to get stuck. But it seems that everytime I shift the front gear I get all messed up and have to regroup my gear selections.

Stubacca

Rear shifts are much closer spaced (in gear inch or gear ratio terms) than front shifts. No matter what the component level, rear shifts are smoother and faster, and will shift better under load.

rigid4life

I wouldn't say that. It's easy to get good shifting from even a so-so front derailer and chaingears, but a lot tougher to do so on cheaper rear components, especially if the cogs aren't spaced right (as they frequently are on cheap bikes). Case in point is my 10+ year Maruishi (now branded Jamis) Challenger, with stock Shimano thumbshifters and Suntour XCM drivetrain everywhere except the cogset, which is really cheap Shimano, and the chain, which is no-name brand off of a Walmart bike. The front shifts smooth and quick like you wouldn't believe - sometimes going down a grade I have to look down to see with my eyes if it's really shifted (and it always does). Yes, it's that smooth! Now it's a completely different story on the rear, because the cog spacing is for some reason all wrong. It shifts fine in some areas of the cogset, but skips or sticks to others, and no amount of cable tension tweaking from me has been able to ameliorate that. So bottom line is I think for many lower-end components, front shifts, if you adjust everything right, can be just as smooth or even smoother than shifts in the rear.

Stubacca

Sure, rear cogs are more sensitive to chain issues than the front. Is your chain the right width for your cassette? If the cassette is incorrectly spaced for the shifters, or if the chain is the wrong width for the cassette, the rear shifting will suffer big time. Chainrings don't care so much about the chain width (you can use a 7/8 speed crank with a 9 speed cassette and 9 speed chain, but a 7/8 speed chain doesn't work so well).

Set it up with properly matched and tuned components, and I'd much rather be doing the majority of my shifting on the rear, especially riding up a hill and under load (which is where it really matters).

I haven't come across a factory bike sold with an incorrectly spaced cassette. Maybe Walmart bikes are sold like this...