Trials bike tubing selection

[ltwiens38]

Hi,

Does anyone have experience building a trials bike? I'm looking for advice on DT wall and diameter: 42 x 979, 44.5 x 179 or should I do a straightwall .9mm? I'm trying to find the balance between strength and boat anchor, lol.

Thanks,

Lyle Wiens

[progetto]

Never seen it but I wonder if trials bikes should have a removeable ding shield protecting the down tube? The only reason to go straight gauge is for ding protection.

[ltwiens38]

It's common to have a bash guard on the bb for the chainring.

Straight gauge would be overall stronger, no?

Lyle

[VertigoCycles]

are you building a stock bike or mod bike? What's the skill of the rider? Is he/she still bashing up the chainstays and down tube or are they past that phase? What type of trials are we talking...Honest to goodness competition style trials or Danny MacAskill street/trials/trail mashup?

Straight gauge would have slightly more dent protection in the areas that would otherwise be butted, but if they ends are the same thickness...say 0.9mm...it'll just make the frame heavier without adding anything to the joint integrity.

My suggestion would be to make the BB as stiff as you can. This means a big down tube and big chain stays. Leave a bit more space between the pedal end of the crank arm and the chain stay than you might otherwise do on a proper mountain bike. In the past, I've had an Ellsworth, a custom Curtlo, some Spanish frame that I can't recall the name of (not Monty), an Echo, a Crescent and a Coustellier and of those, the Coustellier was the only one that I wasn't flexing the crank into the stays on big side hops.

[ltwiens38]

Thanks Sean! That's all very helpful.

I'm replicating the geo of an Echo MK6 mod aluminum frame. That's what my customer has been riding. The DT was cracked through at the BB and halfway through at the HT. The rider is 55 years old, and mostly messes around on his yard. Not to diminish what a 55 year old can do but, it's not MacAskill level I'm sure. The frame doesn't have much for wear in other areas. A bit on the inside of the NDS chainstay though that must be from a wheel rub when it slipped in the DOs? Other than that, it looked pretty clean.

Copy on the stiff BB, I was already thinking that...confirms my thoughts, thanks. I think I'll go with the 42 x 979 for the DT and a 34.9 for the TT.

Thanks again for the help!

Lyle