How to clamp an e-bike on a repair stand?

Question

When doing maintenance on a bike, it's common in tutorials that the bike is clamped to the seat post, and not the top tube. I understood that the reason is top tube may not be designed to resist clamping forces, and the seat post is. Also, the seatpost is supposed to resist the weight of a rider when riding, so the static forces on the seatpost should be within design constraints.

But what about ebikes? I'm thinking more specifically to what should be a worst case: a e-trekking bike, with a mid-motor and the battery in the downtube, and a heavy coil front suspension, woman's frame - all heavy elements are then in front of the seatpost, and with some leverage. The seatpost is a 27.2mm suspended one. My stand is rated for the weight of the bike (around 25kg), but it seems to me quite 'risky' to attach this bike by the seatpost. Is my concern justified, or is better in that kind of case to clamp on the top tube? Should some precautions be taken? (removing the battery is the most obvious, but are they others?).

Answer 1

It's safe for the bike to clamp the seatpost, even on the heaviest bikes. The only thing to potentially be paranoid about is that the seatpost is clamped into the bike securely enough that the bike can't slide down off of it. That can sometimes be an issue, particularly on QR seat collars.

If clamping the post isn't an option for whatever reason, the next best place to clamp the bike from a perspective of minimizing frame damage is the top of the seat tube. However, doing that without fouling decals etc is sometimes a problem. The next place is the top tube, as close to the seat tube junction as possible.

Clamping frame tubes is not necessarily the rookie move that some internet wisdom makes it out to be. It is useful and sometimes necessary when working on various e-bikes, particularly long/cargo ones. However, it has to be done with good judgment.

It's critical to understand that a repair clamp can either be a screw-down style or a cam-over style, and the cam-over type exposes the clamped member to much more force, since the principle they work on is the peak load is a lot higher than the at-rest load. Differentiating between the two styles is important. It's generally pretty hard to hurt bikes with the screw-down style while using remotely good mechanical feel. Accidents can happen fast with the cam type.

The softer/rubbery type repair clamp pads in good, freshly cleaned condition will tend to not be able to scuff paint when clamped only hard enough to hold the bike and keep it from twisting. If it's a harder or slicker pad type, it can be hard to reliably keep the bike from twisting in the stand, which is the typical way to hurt the paint, and in those cases you'll need to use a clean rag to clamp around. When the pads are soft and clean and hold the bike nicely from being able to rotate, it's generally better on the paint to not use the rag.

The thing about clamping frame tubes in general is that when you use a rag, they want to slip all over the place, which is annoying, and when you don't use a rag there's always a level to it where you only hope you have it clamped such that it won't slip and scuff the paint, since it only takes once. Therefore, doing it for no reason is bad.

Answer 2

The battery is often easily removable and very heavy. There is no reason for keeping it in the slot when you are working on a bicycle. This would also shift the center of mass hopefully to the better side.

The battery is usually lockable so when giving to repair shop may be a good idea to remove the battery before.

Answer 3

The seatpost is rated to hold the weight of a rider, which will just-about always outweigh the bike. Getting the ebike up onto the stand and clamped can be a challenge though.

You might need to angle the bike such that the Center of Mass is not too far from the clamp. That probably means forks-down, somewhat inconvenient for front-end tasks but better for drivetrain work.

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I don't work on ebikes much, but I have worked on weird shaped things and some very heavy bikes. Other options might include:

Some workstands have adjustable "arms" more than a single clamp. These can be moved around to provide two points of support where suitable- perhaps the downtube and under the chainstays.

I have also used a "rear axle stand" that supports the rear wheel off the ground and no more. This is particularly light and good for taking to a fixup site.

Last option was to use a "bike lift" that hooked into the saddle and handlebars, and lifted the bike up to a convenient working height. Downside, these are very wobbly laterally.

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For a normal bike workstand, its usual in a commercial shop to bolt them to the floor. For a folding portable one you probably won't have that luxury and tipping is a definite issue. So put something weighty on the legs, or if a tripod design then a bag of rocks hanging underneath can help with stability. Look at construction/road-works signs for ideas.

If it's not complex, you could remove the battery to quickly save a couple kilos off the bike's total mass.

Long term, if your repair stand's limit is lower than your ebike's weight, it might be time for a better workstand.

Answer 4

What I do is to use a repair stand that has soft rubber in the clamp. I set the clamp reasonably loose, set the clamp to horizontal position and clamp the top tube at the point where the bike would stay balanced on the clamp even without any clamping forces.

I think that clamping a top tube is safe, as long as the clamp force is light. It can be light if the bike would stay balanced otherwise even without clamping.

I would find it very odd to have an e-bike that couldn't be clamped that way. Usually the battery is on the downtube, not on the top tube.

Edit: Oh, my top tube is not completely round but rather very flat. In bikes where the top tube is completely round, you may need more clamping force which could be risky.