Spring tensioner safety

Question

I recently ordered this tool kit at an extremely reduced price.

While I am confident about the general quality of those tools I am quite reserved about the spring tensioner included in the kit. In other forums people advise strongly against such types of compressors and urge people to either get a professional compressor or let an specialist do the job. This brings me to my question:

Are those two-part spring compressors in generally reasonably safe to operate? While I understand that with enough carelessness / bad luck everyone is able to hurt himself I see a above average risk in these type of compressors slipping away the spring. Should I be happy about the rest of the kit, throw away the tensioner and bring the car to a professional should ever the spring needs to get removed OR can I use this tool, given enough precaution?

Background information: The intended use would be some vehicles in the 1000-1500 kg class. Front suspension are always McPherson-type struts. Rear suspension would be twist-beam type with separate dampers and springs. I aim to repair (as far as possible) everything car-related on myself, however I am not willing to unreasonably risk my safety/health.

Edit: Some recommendations on needed precautions would be highly welcome

Answer 1

I use two part spring compressors like you show here on a regular basis.* I think you'll be fine but there are some good things to watch out for.

1. Watch out for the threads. If the compressing clamps jump threads, the spring could suddenly express a lot of its potential energy. With McPherson struts, it's entirely possible to catch a finger between the spring and the seats. Ow.

2. Alternate sides when compressing and releasing the spring. You'll be turning the socket driver on one side and then turning the other side. It is easy to get impatient and think "oh, I'll just release this side and then do the other." You'll end up putting the spring on crooked, or as I have done, suddenly realize that you've canted the construction so far over that you can't actually reach the other side to turn it anymore. Foul language ensues.

3. Obviously, if the compressing clamps start to look faulty, discard the tool. Those are doing the real work of holding the spring in place. If they were to fail, that would be a situation with a high badness factor.

* Note: when I say regular basis, I mean every time I change dampers. That's happened 4 times so far with this spring compressor kit. So far, so good.

Answer 2

Use EXTREME caution and you should be fine. One major issue is watching out for the nuts on the end of the bolts: there frequently is no nut stop at the end of the bolts, so the nuts can totally unscrew and the entire assembly can explode in your face, resulting in serious injury or death.

But there is no structural reason why they are bad to use. Just be very careful, and you should be fine.

Answer 3

I'm not a pro, but I don't like the look of those spring compressors. I have some Harbor Fright ones that scare me for the same reason - the hooks don't have a safety lock on them. I dread the thought of all that compressed energy being released. I prefer the Lisle type, where they have a clamp and bolt system.