MountainCycleShawn

Hello everyone,

I am new here and to trials. I am big into mountain bikes but know really nothing about trials, but I have always been interested in it.

I have an idea to take a 26" Mountain Cycle San Andreas frame like mine in the picture and turn it into a 20" trials bike. Everytime I see one with the seat tower off, I think to myself - trials bike.

This is going to require a big degree of open mindness from you guys. And, you should know that I am 45 years old. Although, I'm in better shape then most 20 years olds, I won't be getting crazy with this bike. I'm really only going to build it to have a little fun and to improve my MTB skills. And I can build most of it with the parts that I have.

So here is what I am thinking about doing:

This bike has a +55mm BB height, so I think I should be good there. It will have similar forks on the front. So, I am thinking with the high front end and 42.5" wheelbase I should use a short stem with a little rise. Or, maybe a long stem with no rise, so I can get some weight over the front? Please let me know what you think about the stem I should use. I'll use a good trials bar. I plan to use a MTB crank with the 22 tooth inner ring and I'll cut off the arms for the outer and middle ring. I'll keep the 9 speed in the back and use a short derailer. With the suspension, I'll need something for tension and the 9 speed will give me some gear choice and make it a little easier to ride to somewhere. I have a couple ISIS BB's, but I think they are about 113mm wide. Should I use a wider BB for trials? Which would be good for the gearing, it will align the inner ring better with the 9 speed cassette. I'll put on some 20" wheels and tires. I could use help in deciding which kind. The fork I'll use is disk only, so there is plenty of room for wide tires. There is a lot of room in the swingarm for wide tires, but I may need to cut off the v-brake mounts if the 20" tires get in the way.
Let me know if I missed anything else.

I have some other general questions. I see in some vids, it looks like some people can pedal their bike in reverse, but can still coast. How does that work. And I have also read about freewheel cranks. What are those?

So, again, at my age, I won't be getting to nuts with this bike. it's just to have some fun and to improve my MTB skills. Any help or advise would be appreciated. I would like to find someone close to me who has some 20" wheels to see how they will fit in the swingarm. I live In Simi Valley, CA, which is between Thousand Oaks and San Fernando Valley.

Thanks,
Shawn

P.S. - IF YOUR GOING TO NEGATIVE AND HATEFUL LIKE J DADA, PLEASE MOVE ON!

J_Dada

That's ridiculous. Taking your 26 mountain bike and turn it into a 26 trials bike.

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MountainCycleShawn

I have another old frame to use. I told you it would take some open mindness.

AlexC

this'll never work. chances are your "old bike" won't have the right geometry either... just get a cheapo mod, 24", or stock off this site or pinkbike, then give trials a go.

J_Dada isn't trying to be closeminded about things, it's the truth

MountainCycleShawn

I've been looking at geo and the HT angle is like the same as most trials bikes.

NHtrials

...he is right, this is a tad ridiculous but couple things if you are going to go ahead with it.

- 20" wheels usually have 116mm spaced rear hubs so you are going to have to make a "custom" 20" wheel with a 135mm spaced hub = waste of money when you can find good deals on used ones.

- don't worry your 113mm or whatever bb will be fine since you only need 128mm ones for front freewheel setup.

you're right some of the geometry is similar to modern STOCK (26") bikes...i.e. the bb rise and wheelbase...BUT i'm guessing the chainstay length which has a big effect on rear wheel moves/control is way longer than 380mm. most 20" bikes have like 350mm-375mm.

seems way easier to try to turn it into a 26" trials bike

good luck

treewizzard

i dont even how this bike has a +55 bb

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MountainCycleShawn

The BB center is 55mm above a line drawn between the 2 axels.

treewizzard

well i know that, but thats a mountain bike frame, shouldnt it be like -400000?

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MountainCycleShawn

The chainstay length is 410mm.

I have an extra set of strong disk hubs in 32 hole. I would just lace them to 20" wheels.

MountainCycleShawn

It should, but San andreases have High BB's, but in this case that is good, right?

treewizzard

im sure it wont matter when your bottom bracket is dragging on the ground after you destroy the rear shock, or when you only have a couple inches of clearance with the ground.

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eaterofdog

You are just wasting money and time. These assholes have been riding a long time around here and they've seen/tried this many times.

Let's say you take a guy and start fixing him up like a woman. Some panties and a dress, maybe some makeup and a wig. Is it a woman? No. Add some fake titties and shave his ass. Woman yet? NO. Make him talk in a falsetto and learn to suck wang? NO NO NO.

You are going against the nature of the bike. It's just not ever going to be a trials bike. It's going to be a guy in lipstick and a wig.

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AlexC

it's not just about the bb height... head angle, chainstay length, suspension - it wont work, stop trying

NHtrials

fixed or free hub?

SmartBoy

1. Why 20" why not 26" wheels.

2. Are you keeping the suspension or going to lock it out. Maybe replace the rear shock with a rigid member?

If you are trying to learn the basics of trials the suspension is going to kill you. As you have already found out most of the guys here are going to tear you a new one for suggesting the idea of running a non-trials-comp frame for trials. There are a lot of die-hard newbs that insist the only type of bike you can ride trials on is a comp trials frame and anything else is sacrilege.

Ultimately it comes down to what you want to achieve. The suspension will hurt you in your learning, making everything harder that it already is. But, it can be done. My very first bike that I practiced trials on was a Cannondale Super V.



Buy the time I moved onto a hardtail I had learned ballance, roll-ups, rocking. I was able to get up onto benches and even pick-nick table tops with this bike. My next bike was a Kona cruiser which I learned rear wheel hops on.

Ignore the haters and evaluate what you are trying to accomplish. I would worry more about the suspension and getting rid of it than the geometry. The BB, HT angle, CS aren't going to matter to you when you've got suspension throwing you around while you try to balance. For learning the basics none of it really matters. You can pretty much take any hardtail, go out and learn 70% of the fundamentals before you need to start worrying about geometry. The only thing that might make it easier is stand-over. So look for or use a smaller than usual frame that gives you standover. Maybe look at a dirt jumper frame.

Again, I don't understand why you want 20" wheels. I would stick with 26" wheels, keep the disc in the front (get a larger rotor) and use some rim V-brakes on the rear.

And that's my $.02

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MountainCycleShawn

Free, It's a MTB hub.

rupintart

Even if the chainstays were 385mm, it still wouldn't ride like a trials bike. The reach is different, the ratio of pedal to bar height is different, and lastly, it has suspension.

People here aren't flaming you, they're telling you the flat truth that riding trials on anything except a trials bike, ESPECIALLY a bike like that, will just be shit. Like eaterofdog said....just because you dress it up in trials parts doesn't make it a trials bike. And learning on that, will COMPLETELY suck ass.

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trauma100

Next flame gets a month ban, I think mcs gets the point.

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MountainCycleShawn

The flames have been already been taken down.

treewizzard

hope this isnt viewed at trolling/flame...
http://www.biotorque-tech.com/id3.html

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MountainCycleShawn

It would break doing trials stuff if you put a rigid piece in place of the shock.

MountainCycleShawn

I didn't do any flaming!

Ramrod

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Ramrod

But seriously, you could probably sell it for some, then buy a trials bike

OR DO IT FOR SCIENCE. Make sure to lock out the rear shock or ever better rigid, your pedals changed, and singlespeed fuck yeah

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