I remember seeing this question 4 or 5 years ago but I could find the thread...

Someone just gave me a full set of 31x12.5x15 swampers on some sweet 15x8 Chevy rally wheels. Unfortunately, the center hole is 3.75" and not the 4.25" that I need to get over the hubs on my Gen I.

I spent all day at the junkyards looking for some cheap wheels with no luck. Is it safe to bore out the center holes the extra 1/2 inch that I need or are new wheels my only option?
Or is there some trick I can do with the hub housing?

Thanks,
Matt

I think...Heck ya! Either pay a machine shop to do it or...

Grab yourself a mounted point for a 4-1/2" angle grinder and get to work. Being steel, you're ahead of the game. You will need to carefully treat the cut edge, cause your breaking the "seal" of the chrome.

The center hole doesn't carry the weight of your rig anyway, the lugs do. Kinda like true spoke wheels;only the rod that is pointing straight up truly carries the weight.I'm not sure that I'd grind the center hole out though.I'd have it turned or bored, the truer the hole is;the closer it is to being balanced.Please, any of you engineers out there ,correct me if I'm wrong.I sure wouldn't want to mislead anyone due to my incorrect assumption.

Yes it should be safe but have a machine shop or other qualified shop do the work. It should be bored out as close to center as possible to minimize balancing problems.

Also as others have noted the montero is a Lug Centric versus a Hub Centric designed setup. <img src="/forums/images/graemlins/kewl.gif" alt="" />

I'm no engineer, but there's no way anybody could convince me that an out of round inside the lugs, at the wheels center could possibly effect balancing at the measurement levels of a tire shop. the rotational mass at the center is so small, that it wouldn't be a difference.
By using a mounted point in a grinder, you are spinning a stone that is nearly the same size as the hole you're looking to achieve. Not like using a small bit of a die grinder or something. The biggest concern would be making sure that the cut is clean and smooth, without chips and chatters, that could lead to radial cracks.
I looked long and hard into this recently. I didn't wind up with the wheels that needed it, but I wouldn't hesitate to transport my kids after I'd done it. <img src="/forums/images/graemlins/kewl.gif" alt="" />

No argument here, but




Can you elaborate on this? The way you describe it make little sense to me. Most grinders are right angle drive.

I think he meant a die grinder. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Yep, right angle drive, Nope, not a die grinder...
typical 4-1/2" 13,000rpm angle grinder


Then...
I've found these listed as "mounted points", "mounted cones" and "plugs"
web page

Another option I've long thought of for this purpose would be the "Oops Holesaw Arbor" from Starret. It allows you to use a holesaw as an arbor to enlarge a hole-
starrett

We use both of these systems at work. Many times the stone is used following blowing a hole through a truck frame with a plasma cutter. It makes the hole perfectly clean, and eliminates the chance of the radial cracks.

Oh...those are cool. <img src="/forums/images/graemlins/kewl.gif" alt="" />
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I thought you meant going free hand with a die grinder. <img src="/forums/images/graemlins/smile.gif" alt="" /> Your way is mush better. <img src="/forums/images/graemlins/cheers.gif" alt="" />

freehand with a die grinder would also take... forever! <img src="/forums/images/graemlins/notooth.gif" alt="" /> these are still smaller than the finished hole we would need, but, with very little practice any of us dumbarses at work can make a nearly perfect round hole.