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Re: The Shiny New AM831 Group Buy (A) Thread!
My Frame just came in too. Size Small
August 17, 2021, 01:41:06 PM |
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Re: The Shiny New AM831 Group Buy (A) Thread!
It is worth showing the link assembly issues with pictures rather than just words to get the message better across, so I've drawn some (not to scale, dimensions exaggerated, showing the principles). This is the 831 assembly of the upper link to one of the rear triangle eyelets, as far as I could make it out. Grey is the aluminum link, black the carbon triangle, blue the ball bearing and pink the screw. The screw presses the inner race of the bearing against the link, so the screw and inner race are one piece with the link. There is some clearance between the screw head and the triangle so that the parts can rotate with respect to each other. This assembly would be alright if the two eyelets of the triangle (only one shown) were perfectly rigid relative to each other, but that is not the case. So, what prevents the outer bearing from sliding out of the triangle eyelet (to the left) is in practice only the press force of the outer bearing race in the eyelet, as Maffly stated. Inevitably, when the triangle is submitted to lateral forces, the bearing will end up sliding to this position, where the eyelet contacts the screw head, and rubs against it as the triangle and link rotate relative to each other. After a while, clearance may build up between the outer race and the eyelet, whereby the bearing will move freely in and out... The rubbing with the screw head will cause wear and potentially loosen the screw... The situation wouldn't be improved if the bearing were pressed from the outside. The bearings should be in the link, not the triangle, as per the SC assembly shown below. Yellow is a tube for taking up some of the axial force exerted on the bearings by the screw. Here, the bearings are mounted in the link and rely on the rigidity of the link between the two eyelets. The bearings cannot slide out. Dammit, the 831 link and triangle need to be redesigned!! A not too drastic redesign would be to provide something for keeping the bearing in the eyelet, such as a retainer ring. What about the assembly of the lower link to the triangle? I haven't looked close at that yet. November 29, 2021, 04:10:44 AM |
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Re: The Shiny New AM831 Group Buy (A) Thread!
THEY AREN'T Santa Cruz! That's why this frame cost you less than $1,000! The quality of the product is debatable (outside of this frame), but you are not going to get the same customer service as a Western brand that values is reputation. In summary, as some of us said here, we gambled and lost 
December 14, 2021, 03:30:00 PM |
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Re: BXT-MTB-117 150mm AM bike
Those swing links look much more solid. My first impression of the 831 — before we even knew about the flex/play issue — was that its links looked like they’d have questionable longevity. My son built up this frame (BXT MTB-117). I can confirm that all the pivots are now thru axle. I have attached a picture of the top pivot. It's massively overbuilt. A few things to note: 1. The rear post mounts are default for 180mm rotors (not 160mm as shown on the specs.) 2. Internal routing was fiddly and in the the case of the rear hydraulic hose, a little tight at the head tube. Either the opening diameter was undersized, or there was a burr in there. We needed to open up the hole a little. 3. 24mm bushings for the shock pivots. Some places still show 22mm. 4. I do not know why some people seem to think this is some updated version of the Tideace AM831. The dropouts, bushing sizes, BB mounting standard, and general look are not the same as the latest generation of the AM831. The front triangle on the BXT is missing the dated "camel hump". This bump might have been cool in 2015, but not today... 5. My son is notoriously hard on his bikes and so far there are no issues with flex or failures (but he is under 140lbs so YMMV.) April 16, 2023, 11:56:53 AM |
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Re: BXT-MTB-117 150mm AM bike
Well that looks way better than the AM831
April 16, 2023, 01:34:44 PM |
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