HiYoSilver

Here's my problem. I have a topeak beam rack and bag that floats behind the seat. I've been looking at a new bike and that's the problem. The current has a round alum seatpost that the topeak clamps around. The planned bike seatpost is oblong like the cross-section of an aircraft wing. Since I use the bike for commuting I use about 1200cc of storage, mostly for clothes and do not want to use a back pack. Back pack would be just a temporary solution, but not acceptable for the long run.

No one seems to make any way of attaching the bag to the bike. Oh, I'm looking for a solution that does NOT involve a rear wheel mounted rack. So I can only think of two potential solutions.

Solution A - modify a seat post clamp
https://www.giant-bicycles.com/en-US/...uct/112/29416/
Basically use radiator type of clamps to hold the clamp tight and attach beam rack to it.
It would be pretty ugly, so would have to use electrical tape to smooth out the lines.

Solution B - mount to the saddle
Here would have to make a Y shaped gismo to connect to the sides of the saddle and then have a single bar/tube coming out back. The weight of the bag could be held by the bag straps, and this Y connector would just keep the bag from swinging wildly on turns.

If you have a Solution C, I would love to hear it. Oh, except ride two bikes. That solution is not acceptable to finance.

joejack951

I would look at mounting a rack using p-clamps on the seat stays and the seatpost clamp or brake bridge for the upper strut attachments. Assuming this is a carbon fiber frame, you'll need to be careful using the p-clamps as you don't want to apply too much clamping pressure on the stays. Perhaps you could pre-shape them by hand then use a spacer to limit the actual compression. The installation should be good enough to carry a lightweight bag on the back.

barturtle

The Carradice College saddlebag is 15L (1500cc) and attaches to the saddle loops on a Brooks and the seatpost with leather straps. If you do not have a Brooks, then the Bagman Q/R Support will attach to the saddle rails to hold the bag.

There are smaller bags that attach similarly, by various manufacturers (Acorn, Minnehaha, Zimbale) that allow you to strap stuff (like rolled clothing) to the top of the bag.

Further info, like what Make/Model of bike you're looking at might help, as well.

HiYoSilver

it's looking like a seat post clamp is not a really good idea. Looking at a tri bike, like a Giant Trinity Adv or Trek Equinox

Torchy McFlux

If I were in construction, I wouldn't buy a Ferrari to haul drywall. How about not buying some high zoot aero racing bike to use for commuting?

CliftonGK1

I'm going to guess that means you're selling your current bike to finance the purchace of your TT/tri bike. The best solution I've seen anyone mention is a Bagman support and a Carradice if you insist on Fredding up your tri-bike. Just be careful, or one day you'll look at your ride and realize you've turned it into this:

joejack951

Why not? If he can find a workable solution for carrying a single bag, he'll have about the fastest (for flatland at least) commuter bike possible. My commuter would be considered "high zoot" by most due to being a full carbon frame and fork and lightweight wheels but I've managed to make it a great commuter bike for my hilly 31 mile r/t ride.

chipcom 

I agree, given his strict criteria, a Carradice Barley, Pendle or maybe a large Acorn bag, along wth a with a Bagman support is probably his best option.

LarDasse74

Because the advantages of a super lightweight aero bike are completely wasted when you strap 15 lbs of luggage to it.

I'm not saying it can't be done, or that the OP or you shouldn't try...do whateverthehell you like and ride safe and have fun, but you are both certainly wasting a lot of effort to incorporate what will become a purely psychological advantage into your commute.

I guarantee that a decent, sensible road bike (if they still make these) with aero bars will be 100% as fast as a Tri bike once a rack and panniers are fitted.

HiYoSilver

Yeah, yeah, yeah. No rack or panniers. The bagmag adapter looks promising. Only bag I have seen that has any potential is the carradice sqr slim. Best solution would be replacing the aero seatpost with a round seatpost. Then the problem would be solved. Yes not as aero, but it would work and not add much weight.

We're not talking about much weight, just bulky: winter gloves, extra base layer, goretex slip on pants. The goal is to ride in to work and then do 15 to 25 training rides before hitting home. Not going to switch bikes and doesn't work to ride home and then try to get back out again. Easier to stay out.

I haven't looked at a road bike because of the seat angle issue. I thought most of them are 74d, and I was looking for 78d for more comfort on the aero bars.

caloso

I do this. And rather than mess around with trying to adapt a weird rack or bag set-up, I just use a small backpack. It can be a little sweaty during the summer, but it's better than going home to switch bikes or mess up your frame/seat post with a jerry-rigged rack.

CliftonGK1

You don't need a 1200cm^3 bag for carrying that little stuff. One of the larger Jandd seat wedge bags can easily fit that. Check out the Jandd Mountain Wedge III, and go to a fabric store to get some additional velcro to make a seatmast extender to fit around the aero-post.
I've got a 12L Berthoud on my brevet bike. I can fit everything (food included) for a 400k with 30 degree temperature differential in there with room to spare.

HiYoSilver

The Jandd won't work. I did check it out. It only has 450ci. My old truck had 1000 ci and I had to expand and carry items on top. Current bag is 750ci un expanded and 1380 expanded. I bought too big. I only have had to expand it once. Most of the time everything will fit in the 750 but every other week I need to expand it, closer to the 1000 ci.

Right now the biggest bulk is the winter gloves, heavy ice climbing gloves. today I'm wearing them, but last week I slipped on lighter gloves. In a few weeks, that won't be needed. In about a month, I'll probably drop out the recharger.

I could probably drop a lb and get a small trunk similar to the Jandd for the summer, about 450 ci. But I still have the attachment issue to figure out. I don't like something that takes too long to connect and disconnect.

I may have to rethink the back pack. All the back packs I have seen have two issues: 1- not engineered to keep the pack off your back in hot weather, and 2- have way too much room.

cyclist2000

Why not a handlebar bag and saddle bag combination

adamrice 

Perhaps a frame bag?

CliftonGK1

Look at something like the Camelback Capo. 10L cargo capacity plus 100oz hydration.

cyclist2000

This bag has 1700 cu in capacity
https://www.rivbike.com/products/show...k-green/20-133

HiYoSilver

Interesting, I didn't even think of camelbak. I'll give them a look over next weekend. thanks

barturtle

SQR Slim will not work on your aero seatpost. I know, I own one. I would have recommended it if it would.

Chris_W

Not being able to attach a seatpost-mounted rack is the exact reason why I would never consider buying a bike that doesn't have a round seatpost. There are lots of other bikes in the world, find one where the problem doesn't exist.

chipcom 

You might consider lumbar packs too. I have a MountainSmith Day pack, which is the largest, with the optional shoulder straps. It holds about 850 cubic inches.

davidad

https://www.rivbike.com/products/show...sack-xs/20-130
https://www.rivbike.com/products/show...p-nitto/20-109