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P clamps for bike racks???

Old 07-18-13, 06:41 PM
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alouie457
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P clamps for bike racks???

Unfortunately, my bike (1987 Schwinn Circuit) doesn't have eyelets for mounting a bike rack. Any tips on how to use p-clamps? It seems like most bike racks feel too heavy for p-clamps and afraid that the clamps might come loose when i ride. Also, I can't seem to find a p-clamp that has the right screw size as the clamp. Any tips on how I can get a rack with p clamps? Thanks a lot. A biking novice here.
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Old 07-18-13, 06:42 PM
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The P clamps are a separate piece.. ask Your Bike Shop.
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Old 07-18-13, 10:29 PM
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Home Depot carries the clamps. I'm not sure what you mean by "has the right screw size as the clamp," but Home Depot carries all kinds of bolts and nuts. Get the right size clamps, buy bolts long enough to go through the clamp and the rack legs, tighten it down and you're in business. It won't slip, and if it does, put a wrap of bar tape under the clamp.
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Old 07-19-13, 08:11 AM
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Does your bike have any solid rack mounting points? If not, I'd be looking at a seatpost mounted rack.

You really need at least 1 pair of solid mounting points. You can use p-clamps at either the top or bottom of your rack if you don't plan to carry too much weight. If you try to mount a rack with p-clamps at both the top and bottom of the rack, it'll sway too much from side-to-side.

Blackburn racks used to come with 2 sets of p-clamps so they could be used on bikes with 2 different diameters of seatstays. As a result, most bike shops will have a drawer full of them somewhere. If they like you, that could even be a gimmy.
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Old 07-20-13, 02:19 PM
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They have these at most hardware stores, and they come in various sizes to fit different size stays. I have them holding the rack on a 74 Schwinn World Traveler and haven't had any problems.

http://ecx.images-amazon.com/images/...L._AA1331_.jpg
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Old 07-20-13, 02:27 PM
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My rack is P-Clamped.

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Old 07-20-13, 02:56 PM
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P-clamps require both a nut and a bolt (they are too thin to be tapped), 5mm dia about 12-14mm long should do it depending upon rack. I suggest using nylock nuts and a locking washer for each bolt.
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Old 07-20-13, 05:02 PM
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(1) Buy P-clamps
(2) Put directly in garbage
(3) Order a seat clamp with integrated rank mount
(4) Install rack securely
(5) Laugh at P-clamps


Tjis is one example - there are a dozen on the market and cover ever seatpost size I've ever seen. http://problemsolversbike.com/produc...th_rack_mounts

Feel free to skip steps (1) and (2).
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Old 07-20-13, 10:02 PM
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Originally Posted by Burton View Post
(1) Buy P-clamps
(2) Put directly in garbage
(3) Order a seat clamp with integrated rank mount
(4) Install rack securely
(5) Laugh at P-clamps
Good P-clamps are available through bike shops: http://www.universalcycles.com/shopp...&category=3537
I've ridden 10's of thousands of miles with racks held on by P-clamps. I've never had one fail.
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Old 07-21-13, 03:52 AM
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Originally Posted by Jeff Wills View Post
Good P-clamps are available through bike shops: http://www.universalcycles.com/shopp...&category=3537
I've ridden 10's of thousands of miles with racks held on by P-clamps. I've never had one fail.
I work in a bike shop - remember? Those same clamps are also provided with a number of racks too. It doesn't mean there aren't better solutions available. A seatpost clamp with integrated rack bosses is not only stronger - it saves the paint and provides better clearance for brake routing.

But that's just my personal choice - if you wanna use P-clamps, zip-ties or anything else on your own bike - feel free!

Last edited by Burton; 07-21-13 at 04:19 AM.
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Old 07-21-13, 03:26 PM
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Originally Posted by Retro Grouch View Post
Does your bike have any solid rack mounting points? If not, I'd be looking at a seatpost mounted rack.
I wouldn't. I tried four before giving up on finding one which didn't have my thighs rubbing on its clamp and had side frames strong enough to keep one 15 pound pannier out of my spokes.

You really need at least 1 pair of solid mounting points. You can use p-clamps at either the top or bottom of your rack if you don't plan to carry too much weight. If you try to mount a rack with p-clamps at both the top and bottom of the rack, it'll sway too much from side-to-side.
While a more rigid mounting scheme would be preferable it works fine (as in I rode over 6000 miles that way).

Two caveats are that

1. P-clamps don't have much metal and can fail due to fatigue (I broke one made out of stainless steel which I bought from a marine supply place).

2. Mine (I've tried both coated and plain stainless steel) did not clamp tenaciously enough at the bottom of the rack to avoid slipping down my seat stays. I put some hose clamps below them to solve that problem.



I've been meaning to have a titanium guy weld some eyelets on but keep not getting around to it.

If you really want Tubus sells an adapter which mounts via a longer rear wheel quick release.
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Old 07-21-13, 03:44 PM
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The 1987 Schwinn circuit was a nice bike and from the pictures I've seen, it looks like it has a seat cluster with nice "ears" (maybe forged?) and no dropout eyelets. Anyway, the problem solvers seatpost clamp showed won't work for that bike. OP- I would also suggest a seatpost mounted rack for that frame. Something like this might be good as it has the side frame to enable you to use panniers or a trunk bag. http://www.rei.com/product/743341/to...e-frame-e-type
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Old 07-21-13, 05:39 PM
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Originally Posted by likebike23 View Post
The 1987 Schwinn circuit was a nice bike and from the pictures I've seen, it looks like it has a seat cluster with nice "ears" (maybe forged?) and no dropout eyelets. Anyway, the problem solvers seatpost clamp showed won't work for that bike. OP- I would also suggest a seatpost mounted rack for that frame. Something like this might be good as it has the side frame to enable you to use panniers or a trunk bag. http://www.rei.com/product/743341/to...e-frame-e-type
The frames on that aren't stiff enough to keep panniers out of the spokes - I tried. If a trunk bag is enough that might work; it was the only one out of 4 I tried which had a clamp that didn't rub on my thighs when pedaling.
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Old 07-23-13, 06:22 AM
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FWIW: I use P-clamps on my Nitto Big Front rack and haven't had any problems in a year and a half of riding rough roads (potholes, constant vibration) and often having an asymmetrical (one heavy pannier) load on it. I even portaged home (~8 miles) one full sized Ortlieb completely full of donated books - no issues.

The P-clamps that came with the rack weren't long enough to wrap around my beefy forks on my '93 GT Outpost I use for commuting duty, so I went to the hardware store and picked up a small sheet of aluminum and cut my own with tin snips. Some people recommend clamping directly to the fork (metal to metal), but the P-clamps that came with the rack had rubber buffers for in-between, so I cut some longer ones from a dead tube. ~4,000 miles later still going strong; no slippage, no signs of the P-clamps having stress fractures or anything like that.

I was skeptical of P-clamps before this, but I'm totally sold now.
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Old 07-23-13, 08:46 AM
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I've used p-clamps on a couple bikes for the connection to the seat stays without issue. I've never used them to carry the weight at the bottom of the rack (so, I've always had eyelets near the axle of the rear wheel). If it were me, I'd go to my local hardware store (the local place with helpful people, not a big box chain), and either measure the diameter of the seat stay or just take the bike in with you, explain what you want with p-clamps. They'll be able to get you the right size clamp and make sure you have the necessary hardware (nut and bolt of the right size) to attach it. While the p-clamps usually come with a rubber or the like coating. Where I've attached them to my bike, I put a single wrap around of electrical tape as well...just to protect the finish.
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Old 07-23-13, 01:04 PM
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I'm assuming the OP is referring to no eyelets near the top of the seat stays, as most vintage bikes have at least one set on the dropouts. It this is the case, there is a good rigid contact point that bears most of the weight and P clamps near the top of the seatstays attaching the front rack mounts should be no problem.
Some racks have provision for a center bracket that attaches the crossmember on the seatstays, where the rear brake is mounted. If the frame geometry happens to work out, this may be all that is needed with a fairly short bracket - similar to the way some front racks attach to the top of the forks.
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Old 07-23-13, 01:25 PM
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the p clamps that come with basic racks
in other words
the p clamps that are laying around every lbs in na
are fine for holding bot the tops and bottoms of racks
but i have seen this mounting strategy fail under heavy loads
and high mileage

if it is for carrying your clothes and lunch to work int he morning
then ok
but if you are touring self supported around asia
find a better solution
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Old 07-23-13, 05:38 PM
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So there are P-clamps, specialized seat clamps with rack mounts integrated and seat post mounted clamps specifically for racks. There are also solid rod supports instead of the flimsy steel brackets some racks provide. At the end of the day they're all about the same price. I see a lot of alternatives to 'ideal' used all the time, but ..... not on my bike .....
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Old 07-29-13, 12:51 PM
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you can also make your own out of perforated metal strapping or thin bar steel but they aren't pretty.

my son's bike rack has a seat post adapter bracket which I don't recommend because of the location of the screws. the device previously posted for that purpose seems far superior
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