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TRA J contour

TRA J contour

TRA J contour

In the "round/round" J contour in automotive wheels, I have noticed an indent under the inboard round hump on the barrel. It matches the profile of the round hump perfectly. Some wheels have it, some do not. I hope hoping someone could let me know the reason for the hump indent in this location.

Clarification: There is an indent in the revolve of the barrel underneath the inboard round hump. Not sure of a better way to describe this.

RE: TRA J contour

" .... Not sure of a better way to describe this......"

maybe with a picture?

RE: TRA J contour

I suspect we are talking about the safety hump - a hump put in the wheel at the base of the flange to make it harder for the tire to be dislodged from the wheel. Those humps come in a number of configurations.

RE: TRA J contour

I' not positive on what the OP is referring to but I will hazard a guess that the hump is a safety feature as CaprRacer says, and that the indent is to make installation of the tire over the hump easier.

RE: TRA J contour

Since the OP is asking about indentations (which to me is the opposite of a hump) I'm going to guess that this is on the INSIDE of the rim profile (brake side) and not the outside (tire side) where the safety humps reside. Please see the image link below.

Link to image: INBOARD FLANGE.png

If that is a correct assumption on my part......

The main purpose of the indentation, from my experience, is to reduce weight. It can also provide an area to transition from a thicker wall in the inboard bead seat area (between the flange and the safety hump) to a thinner wall as you travel down the profile towards the outboard flange (towards the the drop well).

The wheels you see that lack this design feature - the machinists probably feel it's faster to machine the wheel without the ID indentation or they've experienced rim failures during pot hole testing and want the added material for more hoop strength to help avoid warranty issues as much as possible.

I've also ran into designs with a hump in that ID area for stick-on wheel weight location purposes - keeps the weights away from the brake as well as far enough from the centerline that they're more effective in balancing the rim. The design of the ID of the rim isn't as crucial as the OD in most instances - just offset from the OD, have enough material in the wall thickness and don't hit the brake caliper and all should be fine given proper metal processing.

Tim Flater
NX Designer
NX Win7 Enterprise x64 SP1
Intel Core i7 2.5GHz 16GB RAM
4GB NVIDIA Quadro K3100M

RE: TRA J contour

I suspect the wheels which have this indentation are spun from sheet, and the ones which do not are castings, in which case the presence (or lack) of the indentation is just a consequence of the manufacturing process used to produce the barrel.

RE: TRA J contour

It's not a consequence at all - it's quite intentional in the majority of cases with which I've dealt. Doesn't matter much anyway since it's been a month and the OP hasn't confirmed or denied the location of which he's asking.

Tim Flater
NX Designer
NX Win7 Enterprise x64 SP1
Intel Core i7 2.5GHz 16GB RAM
4GB NVIDIA Quadro K3100M

RE: TRA J contour

I agree with Xwheelguy. I think the OP is talking about the safety humps, but he hasn't come back to confirm.

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