ErnestSw

Has anyone had their wheel mounting surface milled to increase offset? I'm thinking that it would be relatively easy and safe to have, for instance, 5mm milled off the mounting surface of a 55mm offset wheel to get to a 60mm offset.

Ketchmi

Doing this would thin out the part of the wheel that you want to be the strongest. I considered it but looking at how thin the aluminum would become where you attach the lug nuts.............

I even considered milling the hub but I don't think there is enough meat there to maintain strength.

Face it, if you want proper offsets get out the wallet. With some of Greg Gray's info I'm looking at building different control arms but that's in the future. It changes all the suspension geometry and not necessarily in a bad way.

Dave

Jim bailey - 928 International

The lug nuts are set rather deeply in the wheels and there is not a lot of extra metal under them so removing metal from the mounting surface will reduce the strength of the wheel somewhat but how much ??

BrianG

Dave, why the RR reg in a N/A car??

Ketchmi

More than I want to take a chance on!

Dave

ErnestSw

I didn't take the lug nut inset into consideration when I asked the question. I'll measure the lug nut face to mounting face distance when I get my wheels back from refinishing tomorrow.

Ketchmi

Brian, exhaust mods and some tuning, allows fuel mixture tuning at WOT and is worth some pony's. Losing exhaust restriction will normally lean out an engine and the LH does not control fuel mixture in a closed loop mode at WOT, it's a predetermined map at that point. I fatten it back up with the RRR because our cars love to run rich at high rpm's.

Dave

Jim bailey - 928 International

Correct Dave , talk about a potential liability !

Ketchmi

Let alone watching your wheel pass you going down the front straight.........really high pucker factor involved there!

Dave

Tom. M

FWIW...I compared my club sport 60mm offset fronts (8" width) to a 52mm 8" club sport (from a 951 apparently). It appeared that the 60mm offset on the GT rim was due to milling....as the 52mm CS rim was obviously forged that way...

So..I would guess that it is safe enough for the forged GT rims...

Later,
Tom
midlman@rennlist.net
89GT

Jim bailey - 928 International

No kidding there are things you can experiment with where it may only cost you money if it breaks and things where it can affect your safety or the safety of others.

Jim bailey - 928 International

Tom I think the depth of the lug nut holes was finish drilled AFTER the mounting surface was machined.

Garth S

For interest, I just measured the thickness from the flange mounting face to the bottom of the conical nut taper - on both an older forged 16" and a very recent 17" cast oem wheel: they were both at 8mm, so 5mm is a very healthy % of that. Mind that the conical nuts clamping force is primarily spread out radially from its midpoint - so how much safety margin was designed into the flange ??
Another point - Machinists demand a true surface to set up and work from: the only true surface to easily clamp to in a wheel is the mounting face. Anything else jigged up is likely to be $$.
Xmas is comming - perhaps this debate could be parlayed into a custom set of Filske/Kinesis etc. to grace the Yultide tree ... "Honey, I tried with the Dremel ..."

ErnestSw

Garth,
Well there goes that idea!!

Peter F

I had the same thought on my forged CS wheels to get them from ET 60mm to 65mm but don't think it will be safe removing the 5mm when looking closer.
I'm using 9" CS wheels around on my -81S Euro, this was for the front wheels.



/Peter