Build & Trips on a '12 Trek Mamba 29er

[ultraclyde]

Looks good. I'm not a big fan but several of the guys I ride with swear by them. I'm running drop bars (Salsa Cowbells) on a rigid trek 920 right now. Not a fan of drops on a suspension bike though.

My Rig:

 

[korisu56]

Looks good. I'm not a big fan but several of the guys I ride with swear by them. I'm running drop bars (Salsa Cowbells) on a rigid trek 920 right now. Not a fan of drops on a suspension bike though.

Looks great! I'm thinking that I'll build one that will have drops on it that will be less back country and more hybrid-ish later on. Didn't want to spring for a whole new bike when the hard tail was chilling in the garage doing nothing. I've identified a couple of forks to replace my suspension fork, but I'm guessing it'll be after I acquire storage solutions and a sleeping bag. More than likely won't convert it until after the first trip to see if I like it or not.

I have really been eyeing that 920 though, but I was thinking of some smaller tires for longer road stints. How do you like it in the back country? What are you mostly riding on?

 

[ultraclyde]

I love my 920. It's not great at really technical trail work (drop bars, bar end shifters, rigid, long wheel base) and it's not ideal for rifing road centuries (too inefficient) but it's awesome for anything in between. IT fits perfectly between my carbon road bike and my 5" dual suspension trail bike.

I've got 2 wheel set ups that I can hot-swap depending on terrain. I've got the factory 29" wheels running Bontrager XR1 2.2" tires - small knob tread. I use these on pavement and groomed trails, and for commuting on sidewalks and they work better than I expected. I'll probably go to something like Scwalbe Big Apples when I wear these tires out to be even more road friendly, because I now have the rough country wheel set. The rough country wheels are a set of Stan's 27.5 x 28mm wheels I picked up cheap as OEM take-offs. I'm running 2.8" Terravail Cumberland Tough tires on them. These are perfect for the rough stuff. We ride a lot of WMA and Nat'l Forest roads that are big chunky, fist-sized gravel and very poorly kept (ruts, holes, washes, etc.) Not bad in sand pits, and they roll really well for what they are. They feel like putting the Jeep in 4-Lo. If you can keep turning the pedals, you can ride over anything.

The factory says the biggest you can run on the 920 is 29x2.2 and that's true...sort of. The 27.5x2.8 just barely clear on the back. The front could go a little bigger. I'm running a fairly narrow rim at 28mm too, and that keeps the tire tucked in a little. In the lowest gear the chain drags the edge of the tire tread slightly.

If I were packing over real singletrack trails I'd opt for a hardtail with a suspension fork. This bike was mainly built with commuting and the Cross Florida Individual Time Trial (CFITT) in mind...but I have yet to make it to CFITT with my friends.

 

[korisu56]

I love my 920. It's not great at really technical trail work (drop bars, bar end shifters, rigid, long wheel base) and it's not ideal for rifing road centuries (too inefficient) but it's awesome for anything in between. IT fits perfectly between my carbon road bike and my 5" dual suspension trail bike.

I've got 2 wheel set ups that I can hot-swap depending on terrain. I've got the factory 29" wheels running Bontrager XR1 2.2" tires - small knob tread. I use these on pavement and groomed trails, and for commuting on sidewalks and they work better than I expected. I'll probably go to something like Scwalbe Big Apples when I wear these tires out to be even more road friendly, because I now have the rough country wheel set. The rough country wheels are a set of Stan's 27.5 x 28mm wheels I picked up cheap as OEM take-offs. I'm running 2.8" Terravail Cumberland Tough tires on them. These are perfect for the rough stuff. We ride a lot of WMA and Nat'l Forest roads that are big chunky, fist-sized gravel and very poorly kept (ruts, holes, washes, etc.) Not bad in sand pits, and they roll really well for what they are. They feel like putting the Jeep in 4-Lo. If you can keep turning the pedals, you can ride over anything.

The factory says the biggest you can run on the 920 is 29x2.2 and that's true...sort of. The 27.5x2.8 just barely clear on the back. The front could go a little bigger. I'm running a fairly narrow rim at 28mm too, and that keeps the tire tucked in a little. In the lowest gear the chain drags the edge of the tire tread slightly.

If I were packing over real singletrack trails I'd opt for a hardtail with a suspension fork. This bike was mainly built with commuting and the Cross Florida Individual Time Trial (CFITT) in mind...but I have yet to make it to CFITT with my friends.

Great feedback! Thank you very much. Based on what you’re saying, I’ll hold what I have for a few trips and feel it out before making a call on a fork. That way I can also see if I’m more for touring or keep beating down trails. Some trip reports make it hard to not build a fat bike with flats and disappear for a while.

Does yours run the SLX single front 11-speed setup too? I was looking to convert mine for simplicity and gained room for rear tire. LBS quoted $350 for conversion, but I’m 99% sure I can do it myself if I can find the groupo for the right price.

 

[Stumpalump]

I could not get my Fox Float forks to do anything right. I rode other bikes and found they all had the same problem. Way too plush. I bumped the nitrogen way up for the fix per advise of a downhill race guy. Did the same to the rear shock. Per factory specs I need to gain 150 pounds to be using that much pressure. Now it handles like its on rails and I did not need a new fork. It's really nice to be able to pound down hard on the front end in turns and have what feels like a dirt bike front end. Just sayin if you don't like them then it's more than OK to swing the pressure dramatically. King coil over shocks on desert trucks have a sticker that calls for 150 psi. Suspension tuners tune for 200 psi. Racers run 50-500 psi for the tweek.

 

[korisu56]

I could not get my Fox Float forks to do anything right. I rode other bikes and found they all had the same problem. Way too plush. I bumped the nitrogen way up for the fix per advise of a downhill race guy. Did the same to the rear shock. Per factory specs I need to gain 150 pounds to be using that much pressure. Now it handles like its on rails and I did not need a new fork. It's really nice to be able to pound down hard on the front end in turns and have what feels like a dirt bike front end. Just sayin if you don't like them then it's more than OK to swing the pressure dramatically. King coil over shocks on desert trucks have a sticker that calls for 150 psi. Suspension tuners tune for 200 psi. Racers run 50-500 psi for the tweek.

Very interesting. I gotta check my fork, but I believe its a spring rather than gas. I planned an early break-in ride in May, so hopefully I can work some kinks out.

 

[ultraclyde]

My 920 is the first year model, so it's running Sram 2x10 gearing and bar end shifters. I typically use the larger chainring on roads and the smaller chainring for rough offroad, but having the lo-lo gears is valuable on a loaded touring bike. My trail bike (Fuel EX8) runs 2x10 as well, but I'm fat and slow and need that low gear on steep trails sometimes. On a pure trail bike I would consider 1x11 but I wouldn't go out of my way to get it. I'd run the factory stuff until you have to replace it for wear, then see what the difference in cost is.

One of the things I preach to all our beginners is suspension adjustment. Know your shocks and take time to adjust the settings until you get it dialed the way you want. It can make the difference between an ok bike and a real trail burner. Keep a log and write down the settings and your reaction to them. When I find the pressures I like I write them on the bike near the shock fill so I don't forget them. Every one likes different things from shocks and no shock comes set for you from the factory. Even spring shocks can often swap springs, but I'm not sure they've made spring-only socks on non-walmart bikes in years. The Fuel is the nicest bike I've had, but I still swapped in larger spacers on both shocks to increase compression ramp at the end of travel, and I'm running well over recommended air pressure in front and rear, all because I'm a heavy, aggressive rider. On the other hand, if you aren't bottoming out your shock occasionally on aggressive terrain, then you've got it set TOO stiff and you aren't using all the suspension you have.

 

[korisu56]

My 920 is the first year model, so it's running Sram 2x10 gearing and bar end shifters. I typically use the larger chainring on roads and the smaller chainring for rough offroad, but having the lo-lo gears is valuable on a loaded touring bike. My trail bike (Fuel EX8) runs 2x10 as well, but I'm fat and slow and need that low gear on steep trails sometimes. On a pure trail bike I would consider 1x11 but I wouldn't go out of my way to get it. I'd run the factory stuff until you have to replace it for wear, then see what the difference in cost is.

One of the things I preach to all our beginners is suspension adjustment. Know your shocks and take time to adjust the settings until you get it dialed the way you want. It can make the difference between an ok bike and a real trail burner. Keep a log and write down the settings and your reaction to them. When I find the pressures I like I write them on the bike near the shock fill so I don't forget them. Every one likes different things from shocks and no shock comes set for you from the factory. Even spring shocks can often swap springs, but I'm not sure they've made spring-only socks on non-walmart bikes in years. The Fuel is the nicest bike I've had, but I still swapped in larger spacers on both shocks to increase compression ramp at the end of travel, and I'm running well over recommended air pressure in front and rear, all because I'm a heavy, aggressive rider. On the other hand, if you aren't bottoming out your shock occasionally on aggressive terrain, then you've got it set TOO stiff and you aren't using all the suspension you have.

What great insight. Obviously pegged me proper as a beginner, so I appreciate it. I'll take some pictures and do research on my shock and goof around with it. Luckily, a friend gave me a shock pump a couple of years ago so I can throw that in my tool bag. I'll post up after some investigating this weekend.

Thanks a million.

 

[ultraclyde]

You're welcome, I'm glad to lend an opinion - but remember, it IS only my opinion. If something different works for you, go for it!

I wasn't necessarily trying to peg you as a beginner. I organize weekly Beginner + Chill rides for our local SORBA chapter because I really like helping people get involved in this addiction, er, sport. It's a chance for newer riders to get out and the experienced folks to take it easy and have a good time socializing. I usually throw a tip of the day in my preride meet and greet, and the suspension thing is one. Then comes discussion of tire pressure. And proper stance. And...eh, the list goes on.

If you ever get through the Macon GA area, shoot me a PM and we'll hit some trails.

 

[korisu56]

You're welcome, I'm glad to lend an opinion - but remember, it IS only my opinion. If something different works for you, go for it!

I wasn't necessarily trying to peg you as a beginner. I organize weekly Beginner + Chill rides for our local SORBA chapter because I really like helping people get involved in this addiction, er, sport. It's a chance for newer riders to get out and the experienced folks to take it easy and have a good time socializing. I usually throw a tip of the day in my preride meet and greet, and the suspension thing is one. Then comes discussion of tire pressure. And proper stance. And...eh, the list goes on.

If you ever get through the Macon GA area, shoot me a PM and we'll hit some trails.

Sounds great. Likewise if you’re ever in my neck of the woods. Moving to northern Virginia soon and have a few rides up there on my to-do list. One in May, maybe two. There’s a simple overnighted that would be cool to knock out.

I didn’t get to checking the shock out last weekend. Hopefully I’ll get to it this week.

 

[korisu56]

Picked up the Ortlieb waterproof bags. Pretty stoked as the project is coming together. Of course I walked out to a flat tire, so I need to fix that before I test it out.

 

[korisu56]

Took the bike out to Fair Hill, Maryland for a few miles of testing on some single track.

Good: Bags, jacket, and handlebar. Bags were tight and didn't make any noise. I bought a Pearl Izumi riding jacket at a LBS' ill-timed spring sale; I was sweaty, but never hot. Lastly, the H-bar was great. Bombed down some gravel roads, did some single track, and grinded up longer climbs. Pleasantly surprised.

Bad: My tires are too big at F-2.3 and R-2.25. Going to have to go down to 2.1. Wish that the LBS I bought the bike from years ago hadn't steered me to these tires. I also need some new pedals, so some flats are on their way.

 

[DaveInDenver]

Why you don't like the tires? I'm not disagreeing necessarily, just curious.

FWIW, I'm running a 2.4 front and 2.2 rear at the moment but it varies depending on what I find. I rarely pay full price so it's a matter of finding an acceptable brand, model and size that happens to be on sale.

 

[korisu56]

Why you don't like the tires? I'm not disagreeing necessarily, just curious.

FWIW, I'm running a 2.4 front and 2.2 rear at the moment but it varies depending on what I find. I rarely pay full price so it's a matter of finding an acceptable brand, model and size that happens to be on sale.

I should've been more specific. The tires themselves work well. However, I have little-to-no clearance under the fork for the front tire or from the front derailleur to the rear tire. After a quick google, the max recommended tire size for the Trek Mamba out of the box is 2.1. Perhaps if I went to single front chainring, then I'd gain the necessary clearance to keep a larger tire.

What do you think? If I just have to get used to debris (leaves and such) getting stuck on the FD hanger, then I'll adjust my expectations. I've done WAY more road riding than mtb, so I'm very open minded.

 

[ultraclyde]

As a heavy rider I'm a fan of the biggest tires I can make work on a mountain bike. Bigger tires allow you to run lower pressures ata given load, thereby maximizing traction and comfort (especially on a hardtail.) My 920 came with 2.1s on if so I ran them as long as I could. A few of those trips were loaded for an overnight over mixed routes with pavement and dirt roads with a fair amount of sand and mud. They sucked in the soft stuff. On singletrack where you're fighting roots and rocks, you'll need even higher pressures to keep the rims from banging into stuff under the load, and that will make the bike bounce off the trail obstacles. It decreases control significantly, increases slip-and-slide on wet roots, and wears you out faster. I swapped the 920 to a 27.5x2.8 that is WAY outside the design parameters but it works great on sand/mud/rough trail. On the easiest gear the chain line is so close that the knobs on the tire brush the chain for about half each wheel revolution, but I'm rarely in that gear.

Are the tires rubbing the fork / derailleur while riding? You mention leaf build up - does it keep the bike from working or is it just annoying? Leaves gettign snagged sometimes is part of it. They usually pop loose in short order, but if it's keeping something from functioning, that's a different problem.