Bicycle Mechanics - installing rack to seat post

Just starting out after decades since last bike ownership. New woman's cruiser bike and bought Bontragger rear rack (25LB load) that attaches to seat post as I will not be carrying much weight in the bag and easier for me to install or so I thought. Seat post is too small and the shims that came with the rack are too big and rack clamp will not tighten enough on the seat post to keep rack above the tire. Any suggestions as to what else to try? My husband thought about cutting the shim to make it smaller. I thought about rubber pipe insulation tubing. Getting frustrated and appreciate suggestions.

Terri

Get some help from the bike shop you bought the rack from. They can show you how to adjust the mount if it is like most seatpost racks or may have other shim sizes.

That was a fast reply..thanks. I thought about going back to the bike shop but I am kind of embarrassed. I originally bought the standard bike rack but there were no holes where they should be to attach it under the seat post and did not want to use all the additional clamps they offered so went back to get the 'easier' one. They really tried to talk me into modifiying the first one I bought but I balked politely. I hate to go back again and whine but I might have to. I don't want to appear to be a difficult customer. I already went thru getting two different water bottle cages there as there were no holes for that either.

He wanted me to bring the bike in but I can't. My car is a sportscar convertible and the bike never 'travels by car' and I only ride on bike paths ......lol.


Thanks again,

Terri

... bought Bontrager rear rack..that attaches to seat post .... Seat post is too small and the shims that came with the rack are too big

Don't understand, do the shims extend too far up & down the seat post, or do they reach around too much and overlap? Or something else? If it's up & down they can be trimmed quite easily and w/o risks.


... ..rack clamp will not tighten enough on the seat post to keep rack above the tire. That is w/o shims I assume? Don't get the above tire part either. I can see the rack swiveling if it's not clamped properly, but falling on to the tire?


... Any suggestions as to what else to try?

Insulation tubing is usually "fluffy" and is likely to compress into nothing rather than doing any good. But a lightly loaded rack isn't a critical item, so you should be able to improvise quite freely with zero-to-marginal risk. A length of garden hose slit open is one option, those plastic pipes used for electrical conduits is another. Squares of that type of plastic flooring that's often used in bathrooms is a third, linoleum if you have it. Thick leather, like from a belt might work, but wouldn't be my first choice. Parts cut from an old bicycle tire or tube might work too, if one layer is sufficient. I wouldn't even try tape....

... if one layer is sufficient. I wouldn't even try tape....

He meant 'try tape'.
Electrical tape, and you can customize the fit with the number of wraps.

Both shims that came with it are the up and down type and of course a bit bigger than the post but can't tighten the rack clamps all the way to keep the rack above the tire. One is thicker than the other but both are same diameter. They have a slit down the side so can be cut which we will try first. I want it TIGHT. Garden hose is a great idea and I have old ones we use to drain water heater,etc. I am a pack rat. Also have conduit pipe and linoleum pieces. Husband is a contractor. Great ideas guys......thanks so much.

Terri

That was a fast reply..thanks. I thought about going back to the bike shop but I am kind of embarrassed. I originally bought the standard bike rack but there were no holes where they should be to attach it under the seat post and did not want to use all the additional clamps they offered so went back to get the 'easier' one. They really tried to talk me into modifiying the first one I bought but I balked politely. I hate to go back again and whine but I might have to. I don't want to appear to be a difficult customer. I already went thru getting two different water bottle cages there as there were no holes for that either.i

Hey, it's February. They'er not doing much anyway. Take your bike and rack back to them, smile real sweet, and ask them to make something work for you. It's far, far better to do whatever it takes to get it right once than to have to fuss with something everytime that you use it.

RetroGrouch...love that handle by the way!

I wish I could get the bike to the shop but I don't ride on roads and cannot carry it in my sportcar..lol. If I could get it there I would be very sweet and bat my blue baby boomer eyes and ask for help.

Terri

You could always take just the seatpost and rack with you or better yet just the rack. They should have more of the same bikes there and should be able to show you how to solve the problem. Don't be ashamed to go back. They are there to help with your needs. Helping you with the little stuff will keep you loyal when you need more.

Keep in mind that if it is like most seat post racks. It has fasteners on both sides. You may have to loosen both a bit to get it properly centered over the shims and tight.

Sliced up bicycle tire inner tubes make great non-slip shims on handlebars and seatposts.

Well how absolutely stupid AM I!! Double duh on me. Thanks for the THUMP on the forehead. Of course I will just take the seat/post and the rack and go back to the shop and let them figure it out. I did not get the bike there so have to take the whole configuration but thats not a problem.

Onward!

Terri

He meant 'try tape'.

No, I did mean don't try tape.
IME the glue on the tape instead of keeping stuff in place under pressure will behave as a slick layer for the tape to slide on.
Maybe there is a tape somewhere that'll allow itself to be used as a shim under compression, but not in my toolbox. Might consider it for something like a cyclocomputer though.

You could always take just the seatpost and rack with you or better yet just the rack. They should have more of the same bikes there and should be able to show you how to solve the problem.

That might work if they happen to have the exact same frame and size in stock. Otherwise, you're asking them to solve a jugsaw puzzle without all of the pieces.

Incidentally, I once had a customer who would bring his tandem in to me sticking through the top of his Porsche Targa. Where there's a strong enough will there's a way.

They sell seat post clamps with threaded fittings on either side to take bolt-on racks. Just like having the threaded fittings on the frame up near the seat post clamp. http://www.probikekit.com/display.php?code=NP09504

Thanks again to everyone for all great advice/suggestions. We used a piece of black outdoor plastic well water line conduit that was the right diameter and thick and the rack clamp worked perfectly on it. Its all secure and up off the tire and looks great. I am so happy.

This is a great forum!

Terri

They sell seat post clamps with threaded fittings on either side to take bolt-on racks. Just like having the threaded fittings on the frame up near the seat post clamp. http://www.probikekit.com/display.php?code=NP09504

That seat post clamp with rack fittings is an awesome idea. It's a great shame that it only comes in one size, 31.8mm. I'd buy one in a second if there was a 35mm version. Here's a better image (http://www.edinburghbicycle.com/ebwPNLqrymode.a4p?f_ProductID=7673&f_FullProductVersion=1&f_SupersetQRY=C419&f_SortOrderID=1&f_bct=c003154c003138c012497) for anyone else who is interested.