No you won’t have to thread the hole for the bolt to fit. I bought multiple M10 bolts and they all fit through the swing arm with no force and no wiggle. Maybe you grabbed the wrong size ?
It’s interesting you say that. I could’ve sworn I ordered 8mm arms, but when I got mine the holes were way too big for the stock 8mm bolts. I figured they just shipped the wrong size and at that point I was kind of glad to have the bigger size anyhow. But when I got 10mm hardware, the bolt was just barely too big for the arm. I ended up reaming out the bushing a little to fit the bolt through. I thought it was just a one-off or a me-problem, but maybe not?
Thanks for the replies y’all
I tried multiple m10 bolts. It’s just too small. But 3/8 fits pretty well.
The scenario Skduncan560 describes is exactly my scenario. I ordered m8. The arms I received are way big for m8, but a hair small for m10.
I have a 3/8 stainless in there now and I drilled the frame for the 3/8 bolt. So I think I’m gonna leave it alone for now.
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So you both ordered 8m iris arms? What did Dmitri say about it?… I ordered the 10m arms and the 10mm bolts fit perfectly. I can’t speak for the 8m arms.
Three days ago I received the arms and discovered the M8 bolts didn’t fit. I assumed he probably sent the M10 arms instead. Deciding to keep them and drill the frame, I went to several stores, but couldn’t find M10 in stainless, only zinc.
I spoke to Dimitri briefly about using a 3/8 stainless temporarily. He didn’t exactly recommend it, but said it would be ok. The 3/8ths bolt fit well in the arms, so that’s what I drilled the frame for. I was expecting to drill for M10 once I found appropriate bolts. I flew that night and the following morning without issue.
The next day I found some M10 stainless bolts and figured out that they do not fit the arms. I then tried calling Dimitri back, but only got voicemail, so I have not spoken to him since I figured out that the arms I received do not fit M8 or M10. I can only speculated as to why these arms comfortably fit 3/8ths, but neither M8 or M10. Nevertheless, it’s interesting that someone else here described the same scenario.
Somebody got a 3/8 bit in their 10 mm bin by mistake. Probably a whole run of 10 mm arms with 3/8 holes. Dang, now you got to carry SAE and metric tools for your PPG
I ordered the arms with M8 holes, but they’re too big for M8 bolts, and too small for M10 bolts. So I made very thin bushings out of some scrap sheet metal to fill in the gap so the M8 bolts fit without any slop.
Sounds like the m10 arms are the way to go.
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Yes, if I had it to do over again I would follow your original advice and get the 10mm.
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Interestingly, the Iris Paramotor site now lists 3/8" as the “recommended” option for their swing arms.
That is weird. Recommend for what? Their frames maybe?? It used to say different models of frames not sizes on the drop down. I still think the bigger 10m would be stronger and better for the SP140. I have seen some people shear their bolts from acro.
Hey fellas, there is a lot of things to address here. Before I start, I wanted to encourage anyone who has question to contact us either on the Facebook page or via email. We are pretty busy but try to answer questions and solve problems to the best of our ability.
1). If you ordered 10mm bushings but the bolt doesn’t fit, please get a hold of us and we will get you sorted. This is a mistake on our end.
2). We started to recommend the 3/8" bolt configuration for both carbon and metal swing arms because it’s a good compromise between 8mm and 10mm. It’s much stronger than 8mm when talking about side loads (8mm is not adequate) but not so big that you run into clearance issues with hardware when installing the swing arms. On some frames it isn’t possible to upgrade the nut behind the swing arm mount to.
3). 8mm bushing being too large: we noticed this a while back. The bronze bushings we order have a bigger hole than 8mm. It’s closer to 9mm. Although the bolt has play, it should still be safe to use since the bushing and the whole sandwich gets bolted rigidly and completely to the frame and does not move. We will work for a solution and possibly machine our own bushings to prevent this from happening again.
In any case, we highly discourage people from using 8mm bolts on any swing arms. There have been way too many failures across many brands of machines. They work fine for normal flying and loads in the standard vertical orientation but if you start doing acro and putting any side loads on the swing arms things can get dicey.
Bartlett41: just to clarify, we never had the selection of frame models for the swing arms. You are thinking of our Quick Release prop hubs. We would never offer such a drop down because our swing arms are universal and most definitely not designed to be bolted to specific frames, each one requires some work with a few exceptions.
One last VERY important thing: Our swing arms use zinc plated steel hardware. Zinc plated alloy steel fasteners offer a tensile strength rating that is DOUBLE that of 316 and 18-8 stainless hardware. We test our swing arms with the riser offset blocks in place that use the zinc plated bolts that the swing arms are shipped with. Replacing those bolts with a lower grade fastener has never been tested and we do not recommend doing it.
Your right. It was when looking at the quick release it has a drop down for SP140 / nitro.
“In any case, we highly discourage people from using 8mm bolts on any swing arms. There have been way too many failures across many brands of machines.”
So what do you recommend we should do if we already purchased and installed the 8mm version?
Realistically, what I said mainly applies to pilots who actually get into acro or other high G maneuvers. The 8mm mounting bolt are fine on most machines from most manufacturers that still use them. The failures occur when the pilot is much more demanding. But this tells us that there is a low margin for the types of loads the 8mm bolts can handle. This is why we recommend the 3/8" or 10mm bolt option but you’re not going to die if you choose to run 8mm. 
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Thanks for the information! Can the 8mm setup be retrofitted (e.g. with a different bushing) to fit a 10mm bolt?
Yes, absolutely! If you decide to go down this path, make sure to tell us if you purchased the metal or the new carbon swing arms!
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Awesome. Thank you!
Quoting for importance… I was about to comment the same thing - don’t use stainless fasteners for any application like this!
One last VERY important thing: Our swing arms use zinc plated steel hardware. Zinc plated alloy steel fasteners offer a tensile strength rating that is DOUBLE that of 316 and 18-8 stainless hardware. We test our swing arms with the riser offset blocks in place that use the zinc plated bolts that the swing arms are shipped with. Replacing those bolts with a lower grade fastener has never been tested and we do not recommend doing it.
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Wow, I’ve really gone about this all wrong, haven’t I? 8mm stainless bolts. Good thing I haven’t been able to fly at all lately!