Mang0, I've left my bike lifted for upwards of two weeks. There is no bending or cupping. I'm using grade 8 bolts.

 

i'll check the grade of my bolts and post a pic of what i see--maybe you could help me figure out what i'm doing wrong, thanks

 

If I can't, I'm sure someone with more engineering experience can.

Let me also say that I am using 1/2" grade 8 bolts. I did have to drill out the holes on the pads and on the arms of the jack to accept them. I think the stock bolts were in the area of 12mm thick.

 

here's a pic of what i am seeing. i probably have something screwy.

 

From what I can see, it's the vertical support on the bunk that's bending inward just a bit. I don't see your bolts flexing. I've thought about putting spacers between the bunks, for the bolts to travel through, to keep the two vertical supports from bending inward.

I thought about using 1/2" ID metal pipe but, being the lazy bastich I am, I might just use some PVC outdoor, sprinkler type pipe. Some of it is pretty stout, some of it, not so much. The interior, water supply type seems to be much weaker. Might have to go to 3/4" ID to get the higher grade (grade 40??). I think it would be fine as a spacer. I think it would handle the load very easily. Probably.

I think keeping those vertical supports (or whatever they should be called) separated would provide a more stable platform and would keep the bunks from bending sideways.

I believe SC thinks I'm nuts. If so, he's a member of a big club.

 

LMAO. No, I don't think your nuts.

If you are using PVC as a support spacer make sure you use sched 40. It's pretty stiff. I've used it as a spacer in the front end without cracking or chipping.


As far as the picture goes, those look like small diameter bolts. Did you just buy the same size as stock, except longer to compensate for the added necessary length?

1/2" grade 8 bolts are pretty beefy.

 

My stage II mod (post #130) eliminates that problem. PVC won't help.

 

The red jack that Vic did the modification to, #00950190000, is currently available on line at Sears craftsman site for $99. That's $20 off shipped to your local Sears store.

 

Since there has to be some movement between the lift pads and arms, you can't fully tighten the bolts and there is some slop so the pads tweak a little. My modded Harbor freight does the same thing and I have had my bike on there for over a month and it is not going any where. I also used the stock 12mm bolts that only reach to the middle of the lift pad and still no problems (the way the HF jack pads are designed you can just use the stock bolts). Some spacers might help a little on the Sears jack, but it is mostly due to the fact you can't fully tighten the bolts. Welding the bar in the middle would help eliminate it, but in my opinion it is not necessary and there goes the simple mod.
CB

 

i believe they are 1/2 inch bolts, i also thought about adding some tyoe of spacers under the "bunk", although i never considered PVC. i also picked up a threaded bar and was thinking of running it across the two "bunks". but all in all, i'm not worried about it. i think itsw a well worth mod. if i find the energy and try spacers or the bar across the bunks--i'll post a pic of the results.