# clamping Tarmac-style carbon bikes in repair stand?



## tom_h (May 6, 2008)

What are you all doing, for clamping carbon fiber bikes having the Tarmac-style curved/elliptical top tube?

I've been using a Park PCS-10 stand, and up till now, aluminum frame bikes. With my wife's aluminum-framed/carbon-post Specialized bike, I've just clamped to the Al seat tube.

These are my concerns for an all-carbon bike -- maybe I'm being overcautious :

1) generally prefer the bike to be horizontal, in the stand.
2) "no torque" on CF bike frame best achieved by balancing bike on its top tube and _lightly_ clamping on the TT, but seems problematic on elliptical/curved top tubes. Could easily have extreme pressure where corners of clamp jaws dig into TT.
3) clamping to CF seat tube seems bad if bike is horizontal - bikes are "nose heavy" and weight of bike will apply high rotational torque to 6" section of CF seat tube, under the clamp. 
4) clamping to CF seat post seems bad, for same reasons as #3.
5) installing temporary _Alum_ seat posts just for clamping is a PITA, and all that repeated swapping may eventually cause other problems. 

I'm not _really_ wanting to buy a new repair stand, of the type that holds bike under bottom bracket. Plus, that stand design requires removal of one wheel, to provide a 2nd clamp point on bike's drop-out -- an inconvenience.

I've been thinking to take small heavy-duty 4x6" plastic bags, inject a bit of low-expansion insulation foam inside bags, and then let the bags "mould around" and "harden" into the TT's shape, creating custom fitted cushions ... the Park stand would clamp to the _outside_ of these TT cushions. 

I may be overthinking this ;-)

1st pic below: clamping jaws of the PCS-10 stand I now own.
2nd pic: BottomBracket-style stand, that I prefer _not_ to buy.


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## Dr_John (Oct 11, 2005)

After having at a minimum my paint damaged at shops by mechanics clamping the seat tube on my Roubaix using the standard type, I went with the BB style you refer to. I guess since I do it a lot anyways, the 5 seconds it takes me to remove my wheel isn't that big of a deal. Plus when I do remove it I take the opportunity to fish out gunk stuck in my break pads.

I know the overwhelming majority of folks use the standard type, but personally I like the BB-style better.


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## PJ352 (Dec 5, 2007)

I'm not disagreeing with Dr_John's solution, because it's probably the ideal 'fix', but I use a Park stand (similar, but older than yours) and clamp to the carbon seat post. Never experienced any problems with standard maintenance and if/ when you decide to apply high torque (the BB comes to mind) holding the frame with one hand (or having an accomplice do so) to offset the twisting forces offers a degree of safety. 

I think of it this way. At even my fairly light 137 lbs. when I hit a pothole what is the amount of impact absorbed by the frame? Yes, the tires & wheels absorb some, but at 110 psi I'm thinking a fair amount also goes through the frame. I know this because my hands and butt feel the impact. 

And yes, you're over thinking this.


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## ukbloke (Sep 1, 2007)

You can easily take the front wheel off to correct some of the fore-aft weight imbalance. One could also add (temporary) counter weights at the rear, but that just seems silly!

This is not something I worry about, other than the high torque situations that PJ352 mentions and then I similarly apply some counter-torque. If I do damage the seat-post that is not the end of the world.


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## Dr_John (Oct 11, 2005)

I should add that the Park BB-style stand I bought was the first and only stand I've purchased. I wouldn't have replaced a conventional stand with it, but I don't regret at all buying it. I really like being able to apply a serious torque in any direction and not needing a counter force, but that's hardly worth buying a new stand for. If you were shopping for a new stand, I'd suggest considering a BB-style stand, but if you have a conventional stand that you're happy with, don't bother, for the reasons others have mentioned.


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## JacksonDodge (Mar 26, 2006)

Shops actually clamp carbon tubes in the stand?

Wow. Glad I don't work in one of them.

Stay away from those places, please.

Seat post is the only way I've ever done it. Granted, certain bikes(TT and integrated mast designs) are a little trickier but I've never clamped a carbon tube in a repair stand.....

I fix hundreds(if not at least a thousand) bikes a year and I've never run into a problem using the post. Mark your height with some electrical tape Voila!


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## tom_h (May 6, 2008)

I recently asked the retailer where I just ordered an S-Works frameset, and they replied they clamp the carbon seat post "no problem", consistent with what everyone's been posting -- of course, with the precautions already mentioned.


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## The Squeaky Wheel (Jul 5, 2008)

JacksonDodge said:


> Shops actually clamp carbon tubes in the stand?
> 
> Wow. Glad I don't work in one of them.
> 
> ...


+1

Bikes should only be clamped at the seatposts


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## DMFT (Feb 3, 2005)

+2 + + +  

- I have wrenched for many, many, many moons. Clamping a bicycle via a carbon seatpost with "light pressure" is perfectly fine. Wheel in or wheel out, it does not matter.

DO NOT (IMO) EVER CLAMP A FRAME TUBE or use a car-top rack that clamps via the downtube unless it Alu./Ti/Steel.


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## ukbloke (Sep 1, 2007)

DMFT said:


> ... or use a car-top rack that clamps via the downtube unless it Alu./Ti/Steel.


Hmm, I hadn't thought of that. I have a Yakima hitch-mount rack with rubber straps that go around the top tube and down tube. The amount of pressure isn't at all adjustable and the Tarmac down-tube might be too fat to even fit. Either I'll have to get a roof-mount rack for the carbon bike, or ask one of the family to walk instead. I guess I now know what to spend my REI rebate on this year. Thanks for the information!


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## Dr_John (Oct 11, 2005)

> Shops actually clamp carbon tubes in the stand?


Can you believe it? This was done by one of the Bay Area Uber-Wrenches when he changed my bottom bracket. The shop is too small to have an apprentice, so I know it was him. Put a nice gash in the seat tube paint. I started doing all my own wrenching after that and none of my bikes have been in a shop since.


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## jlandry (Jan 12, 2007)

I went into the shop one day to pick up my new bike. I asked the salesman to swap the pedals for me. I watched in horror as the salesman clamped the top tube much too tight in the stand. Crushed the aluminum tube like a pop can.
As he turned pale, he got me to chose another bike.


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