Rear Axle Widths

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jonclancy
Posts: 942
Joined: Tue Nov 01, 2011 9:30 pm

Rear Axle Widths

Post by jonclancy »

Hi All,

I hope everyone is safe and well during these difficult times.

After a tip, I had a look in my Ortenburger books to see if the various comparative axle widths were listed. I couldn’t find them, but I do have wire wheel and steel wheel axle casings here to compare. “So what,” you say, “we all know that the steel casing is wider. That’s why Splat’s wheel fell off.”

Indeed. However, I also have a Nash rear axle casing here too. The swingle-tree is mounted in a different place, the spring mounts are slightly different, and there is no oil fill hole. But... it is a BMC axle. Widthwise, from the edge of the diff-casing bump to brake backplate flange on the WW axle is circa 430mm. The steel and Nash axles casings measure circa 445mm. So, if you want the correct rear track, it seems the Steel Wheel axle is the one to go for. Just add Peter May’s HYBRID wire wheels halfshafts.

I am not sure what the tyre centre tracks were on the wire and steel wheeled MG Midgets. Maybe the bolt on splines widened the track accordingly to make them the same on the road? Will look into this if I have a moment. Busier than ever in lockdown! :D
biggles
Posts: 314
Joined: Tue Apr 10, 2012 8:10 am

Re: Rear Axle Widths

Post by biggles »

Splat's wheel fell off? When?!
Pm ing you btw re flying (or rather, not!) stuff....
Tim ( yep, busy on all the wrong stuff such as childcare while the wife works. Going slowly nuts. Didn't lay in stocks of all the stuff I needed before lockdown. Bugger)
Westfield 129
Posts: 867
Joined: Sat Jun 04, 2011 4:20 am

Re: Rear Axle Widths

Post by Westfield 129 »

It really doesn't matter which axle housing you use if you want to go with wire wheels. There are a couple of different backside spacing 15" wire wheels you can use in the rear, including a 5.5 and 6" widths in both rim and center laced types.
I like to use the 5.5"X15 TR250/TR6 center laced wheel to get another inch or so of rear track. There are rim laced wheels as well in 6" width as well. This works with the 5.00X15 Dunlop vintage race tires that I prefer. Plenty of room for this setup.
All of the options are off the shelf, and the pricing is about the same for any of them.

Wire wheel axle housings are an inch narrower than disc wheel housings. But in the general scheme of things, it really doesn't matter which you use if you are changing the axles to the competition type.

If you go with the longer disc wheel axle, you can use a wire wheel with a deeper backside spacing with rim width up to 6" as well.
Or, you can order custom made wheels with any backside spacing you need to fill your wheel wells and clear the rear suspension arms.


I have used both on builds. I don't really have a preference. Just know what backside spacing you want for your wheels, wire or disc.
That said... Yes, I would rather start with a wire wheel axle housing if I am going to run wire wheels.
But... And there is always a but... I have the disk wheel housing on my car, and a wire wheel conversion hub, and have picked out a wire wheel with a 6" width that will work perfectly with the extended width, so... Whatever... You really can't make a mistake.

When looking for your axle housing, think about the cost of the axles you want to use, and which type of wheel you need as well. Remember that you need to increase or decrease the wheel's backside spacing by approximately half the difference of the axle housing length to keep the tire centered and clear of the suspension arms. You can also decrease the wheel's backside spacing and change wheel width to increase rear track. Don't forget to take measurements prior to ordering custom disc wheels. This is not rocket science, but can be a bit more complex than what I have described here. It depends on which tires you want to use, which wheels and the rim width vs backside spacing. Both width and backside spacing are important in the placement of the wheel within the rear wheel space in the clamshell. Note that going to 15" wheels will require cutting the bottom (underneath) of the clam to clear the slightly taller tires.

Oh... Backside spacing, for those who are unfamiliar with the term, is the distance from the mating surface of the wheel/hub to the to the outer edge of the rim, back side of the wheel. This is a far easier way to determine what will fit your car than trying to figure out "offset". This is a hard measurement that you can measure yourself from the mating surface on your axle to wherever you need clearance inside the wheel well. It is easy to measure on the rim as well with a roller across the rim, and another ruler to measure the depth to the mating surface. This makes figuring out what wheels you need much easier, especially since MWS lists their wire wheels by width and backside spacing.

Have fun. Plenty of time to mess around with the car in the garage. We should all have 100 pt cars if we apply ourselves.

Stay safe. Masks everyone! No touching and two meters, or more, wash packages before opening... And don't get run over by your neighbors on bicycles. Waiting for July... Maybe it will be safe to come out then...
Splat
Posts: 461
Joined: Thu Jun 02, 2011 5:12 am

Re: Rear Axle Widths

Post by Splat »

Ancient history. As in, genuine ancient history.

When I first bought my car, in a very shabby state, it ran on Westfield-supplied 13” Minilite replicas. I initially converted it to 13” wires (the ones you have, Tim) using the readily available, bolt-on splined hubs. But I was really uncertain about them. Not only are they bolted to the original, sawn-down wheel studs with nylocs, they use TURNED-DOWN nylocs!!

And, yes! Sure enough, after a couple of thousand miles (probably less) one fell off! Thankfully, at very low speed on a roundabout.

Second time around and I did it properly. A complete swap at the front to the correct splined hubs (rather than adapters) and the aforementioned Peter May “hybrid” half-shafts at the rear. Peter produces hardened steel shafts (a must with an LSD) for both wire and steel-wheel axle casings. But he also does half-shafts with splined hubs in the longer length to fit the steel-wheel casing. Job (rather expensively) done.
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