SergeL

Something ridiculously high, about 26" wheel. I can recall impressive bmx nollies over the rails, but I'd like to see a massive static sidehop from front to front/both wheels.

Do you know something about crewkerz (or atomz?) idea of a clutch freewheel. Were there any ridable test samples?

But isn't there more stress due to same chain segment is loaded from kick to kick? I know this is an extreme example, but imagine you have multiple rail-gaps in a row. While front freewheel setup is naturally rotating from every pedalkick, chain on a freehub is "frozen" during jumps without crank rotation. From street rider perspective I can confirm that freewheels have more drag, especially if you have double sprocket tensioner or dirty chain. Also with freehubs, tricks like tailwhips are less prone to backward crank spins due to chain tension.

Wheelbase: 1060 BB: +10 Head angle: 72 Chainstays: 385

I'd like to see safety standards along with quality control for parts, meaning things won't suddenly snap due to design sloppiness/manufacture fault. Even Clean did a K1 carbon frame with hs33 mounts under stays and later realized it's not working properly. Maybe changeable fork steerers. Specific trial brakes with progressive leverage like "servowave" to have both power and pad clearance Would be interesting to try vertical dropout adjustment to play with bb rise and geometry in general

In short, piston internals are incompatible It was time to service my BB5 brake, so decided to compare internals with BB7. Following photos aren't mine, as I forgot to take pictures, sorry. Here is BB5 disassembled: First of all, BB5's balls are bigger 😁 (1) and bearing base (4), which is pressed in caliper's body won't adopt BB7 drive cam correctly. Moreover BB7's drive cam is thicker in place (2), but few mm smaller in diameter (3). Basically, this is a dead end for a conversion. Possibly, you can press out bearing base (4), install new drive cam and put some thin wall tube in BB5 caliper to compensate diameter difference (3), but it is not worth the trouble. Design issue with these brakes It is a BB7 piston: Drive Cam movement is fixed (it is pushing a pad into rotor while rotating), but Pressure Foot can independently rotate and tilt in every direction due to a small metal ball (default 4mm bearing ball) between Foot Screw and Pressure Foot. This design makes sure pad is always contacting rotor squarely under a load. Same goes for BB5 but without Foot Screw. Everything here is made of hardened steel except Pressure Foot. Unfortunately, with time this ball imprints deeper in Pressure Footer's aluminum body. This directly affects on how outer pad is performing: deeper ball position makes pad further from a rotor, so more lever travel needed to initiate braking. With BB7 this can be fixed with a couple of clicks of outer pad adjuster, but with BB5 you don't have many options: either put something under a ball, or between pad backing and pressure foot. Also this ball sits quite tight and can't be removed by bare hands, it needs some love from angle grinder to pop out. In a very neglected condition Pressure Foot can rub Drive Cam under a load resulting in brake jamming. Normally, these brakes aren't tend to jam, but if it happens grease this gap to reduce friction on BB5 or screw outer pad adjuster inwards on BB7. Another observation is uneven pads movement on BB5 On this pic Drive cam + Pressure Foot are red, pads are blue, retention spring is black and disc is green. 1 - piston axis, 2 - spring's contact point BB5's retention spring design makes outer pad's idle position unparalleled to a rotor. Spring is pushing pads above Pressure Foot's rotating center, which is a metal ball, thus making lower part to stick out). To avoid this situation put a rubber band or heat shrink tube on top of pads' handles. Note, that band shouldn't squeeze pads too much, as they can bite disc. This is a piece of tube I used, fixed with sewing thread to prevent slipping:

I feel like 170-175 cranks are easier for fakie stuff and spinning tricks. But shorter cranks positively affect straight jumping, because you are launching from both feets rather than only rear. They also improve balance a bit and give more room for barspins and obstacles.

I don't have bb5 yet, only some broken bb7 calipers are lying around and I was wondering, if it is possible to replace internals such way. Piston & pull arm from 7 combined with everything else from 5.

I really like how these frames are paired with low travel forks. By the way I'm quite surprised this fork and front sprocket are still alive after trial abuse.

Both bikes look very nice! Vbrake and feeehub plus extra tensioner - quite interesting setup you have there. I'm wondering how mini mudwing would look on the rear end.

I was staring at pic for a 10 sec looking for a crack or something meaningful, but these scratches are absolutely normal as tyre wear. Can't say what cranks are you using, but my echo TR only cracked after 4-5 seasons of harsh beating, just check them regularly.

This is how badly cracks could go:

Covering blindly that distance on a such height, this is incredible

For example, Czar Street highriser is claimed to be triple butted: 1.8mm/2.6mm/1.8mm (official info). But Reynolds website says: 1. On double-butted tubes the thickness of the tubes at both ends is thicker than in the centre. 2. A triple-butted tube means it has three different wall thicknesses along its length e.g. 0.9mm/0.5mm/0.7mm. So, either Czar is double butted, or maybe there is an extra taper... How about 1.8mm/2.6+x mm/2.6mm for bended zones. Additional strength - maybe, but such extra taper doesn't correspond with weight advantage, which is claimed for triple butted tubes. Varying thickness in negative direction like 1.8mm/1.8-x mm/2.6mm makes no sense as bended zones are more stressed than grip area. Ok, imagine thickness reduction of the stem clamp area: 2.6mm/2.6-x mm/2.6mm. But this area is so small like 40mm and can't save enough weight.

Thanks everyone! Nope, it was another "atom" named company - a local brand called Atom or Atom Racing:

Hello! I built a streety 26" double disc based on a retro-geo frame (Atom Trial '04). Despite long rear end (405 cs and -15 bb height) it rides comfy enough. Bashed some parts while bunny hopping: fork's steerer tube (5 yrs old), rear lever blade. Rear disc brake is super stressful for a generic disc mounts, had to reinforce it with DIY brake booster connected to v-brake mount (it improves braking performance when wheel is spinning backwards). This 2mm zinc plated steel cracked after 1.5 years (previous one made from cheap 3mm alu lasted half an hour ).

Ok then, I was misled by stem-bar combination choice.

I like that you made color accent only on a frame without collecting parts of every red tint available. But not sure carbon cranks are practical for any trials oriented bike.

That tensioner is the work of art! Could you make some close up photos of a tyre clearance, cause 365 mm sounds intrigue.

I'd try to wrap a beer can stripe around it for a tighter fit.

Nothing special, just enough to keep it in place on vertical dropouts with single wheel tensioner. Rear cog chain overlap is also fine. Found this crack on the previous one:

Yep, no noise or chain skipping. Cog and freewheel look ok too.

I'm experiencing weird problem with this chain, its rollers are cracking without obvious reason. This is a narrow model which was ridden 10 times maximum. Same, but previous chain lost 3 rollers in about half a year. None of my other KMC chains had this issue (510/610 or 710/810)

Interesting find... This frame was a part of popular entry-level bike from russian brand Stark around 2005-2011 years and original name was Stark S.T.R. Geometry is not bad except too small headangle, but nobody cared because it was cheap. I had two of them. Frame cracked everywhere except seatstays in about two riding seasons, disc tab also snapped.

Good vid! Like the fact that all riders put some trials in here, especially mtb riders bring warm feelings of early 2000's, when there was no limitation in disciplines