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Topics - gumby

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Road Bike Frames, Wheels & Components / Question about L-Twoo ERX rear derailleur
« on: May 05, 2024, 02:34:13 AM »
I've had an L-Twoo ERX groupset for about 9 months now. I've never been super impressed with the shifting precision but for the price I wasn't going to complain too much. Today I put a new cassette and chain on and when doing so I noticed that the derailleur cage looked bent.  The bottom pulley sits further outbound than the top.  Immediately I figured the derailleur hanger must have be bent somehow, not sure how as this bike has never been off the trainer, but nonetheless, that was my first thought.  Before pulling the bike out of the trainer and into the bike stand I figured I'd throw on the 105 derailleur I had on the bike before putting on the L-Twoo groupset, it lined up perfectly. I then put the hanger alignment tool on, it is also perfect.  The only remaining thing is that the L-Twoo derailleur is bent somehow, or maybe it is just like that by default (which would be a bit weird). Can any of you out there with L-Twoo ERX drivetrains have a look and see if yours looks like mine?  It's hard to photograph but you should be able to see what I mean in the attached image.

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26er & 27.5 (650b) / Chiner standover height
« on: July 29, 2015, 12:50:42 PM »
Hi all,

First time poster here.  Been looking at chinese carbon frames over the last few weeks and I think I may bite the bullet soon and order however I am trying to determine actual standover heights at the seatpost end of the top tube as it doesn't appear that this is an advertised number.  I am 6'1" tall with a 34" (863mm) inseam.  My current bike (an old Kona Kula 26") that measures 770mm (30.31") standover height to the center of the top tube and I am pretty comfortable at this height (1.5-2" clearance between the frame and the boys).  By my measurements (see below) I can approximate what the standover height would be but I was wondering if any of you out there that have 19,20 or 21.5" frames can tell me what yours come out to and which frame you have and from where.

Thus far I have the following method which I believe is correct.  Most sizing charts show the BB center to tube center as well as the distance between the hub center and BB center which gives as a close approximation of the distance between the hub center and top tube (the seatpost is on an angle so the number we get isn't the exact vertical height).  Now that we have the height of the hub center to top tube we just need the height of the ground to hub center.  We can take an avg circumference of a 27.5 wheel with a 2.25" tire on it (2182mm based on Cat-Eye website) and find the radius ( r = 2182 / 2pi ) of approximately 348mm.  So now on a vertical plane we have ground to hub center and hub center to top tube and thus we have ground to top tube.

A 20.5in cs-196 from xmcarbonspeed.com based on the above calcs is 769.5mm which is almost exactly the same as my current rig.

466.9mm-45mm+348mm = 769.9mm

A 20" CS-136 looks light it might be a bit short for me
423mm-45mm+348mm = 726mm

Even though the frames are only .5in different in size they are 1.75" different in standover height.

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