4

For context, the bike is a small Giant Liv Alight and the rack is a Transit Rear Rack which carries up to 40 lbs.

The distance between the mounting eyelets on the rack and the ones in the frame is about 8," while the rack-to-seat post distance is a little less. There are struts (attachment arms) for sale which are 11".

I plan to carry close to the 40 lb maximum. Considering the weight, would you recommend mounting the rack to the frame or the seat post? (As a city hybrid, this set up is a downgrade from the stronger, heavier set up on my touring bike.)

  • I attached those two prongs in front to my seat post and the others down to my rear wheel large nuts. Mine holds 40 pounds too but there are vids on youtube that will show you how to hold more, I had to use an extra part or two from Truvalue to get it all in place. – bobbym Feb 3 '17 at 3:01
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From rack strength perspective it doesn't make much difference. Most of the weight is going straight down to the rear dropout. The front connection is mostly for stability and isn't bearing much weight.

transit rack

From the seatpost's perspective, it's already carrying 150+ pounds (75kg+) of the rider. Another few pounds is nothing. (Note that racks that cantilever off the seatpost are another issue and they can put undesirable lateral force on the seatpost).

The only problem in attaching it to your seatpost means that it'll be harder to adjust your seatpost. One benefit though is that means it's a tad bit harder to steal your seat.

3

One additional benefit of bracing to the seat post is that with some combinations of rack/bike (yours may be one of these as you have V-brakes) the left brace to the frame interferes with the brake noodle. My old rack was fine, but one my new one I can't use the left brace to the frame at all. It's stiff enough to not move around fully loaded even so, because it's braced using solid alumium bar tightly clamped; the old one used a bent steel arrangement that was a bit more springy and really needed both.

2

Like the other poster said, you're probably fine with either approach. But... if you want to get scientific with it, you're better off mounting to the frame because of the reduced distance and lower weight distribution. Side to side sway will be felt more with a higher mount point.

  • Thanks for also answering too and welcome to bicycling.se! It seems the OP is saying it's 8" to the seatpost and 11" to the frame. So it's shorter to the seatpost. Attaching it to a higher location (the seatpost) would seem to also be better in terms of side-to-side swaying. But I agree that in almost all cases, it's better to go to the frame as it doesn't interfere with seatpost action and the added stability of a shorter/higher location is rather moot. – RoboKaren Feb 3 '17 at 8:03

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