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Narrowing a Rearend to match 1031 width + 40mm

jmc0369

jmc0369

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Jan 1, 2017
Location
San Diego
Going through the threads on rearend swaps and aside from the argument of which rearend (Ford or Toyota); what's the argument against narrowing a rearend to 40mm over stock 1031 if you know you are using wheels that otherwise would need a 20-25mm spacer?

I have BMW wheels on hand and considering either one of the 2 rearend options (which ever I find first for the right price considering what's inside the pumpkin). If all work being equal, it seems to me why not spec the width so as to not need spacers. Save $160 by only needing spacers in the front.

Thoughts?
 
Are you buying a rear that is narrower than stock or wider than stock? If the wheel would usually require a spacer, than the new rear end would have to be wider than stock to eliminate the spacer.

The only issue in regards to handling that rear end width plays is if you go excessively negative with the offset (read deep dish wheels) it is much harder on the bearings. I had to have torino bearing put in my dana 60 to handle the wheel setup. I run 11.25 wheels with 3.5" of backspacing. No, not on a Volvo but the engineering principles don't change.

The other thing to keep in mind is the mounting points of the rear suspension. If you too narrow you can encroach on the factory mounting points. I.e. my leaf springs near touch the rear disc calipers.
 
I thought that the 8.8 had axles that were 2 different lengths and that by shortening the long side it made it both the correct width and symmetrical. I could be mistaken with that though.
 
I put in a 8.8 with the one side shortened to match. Overall it's 1.5" wider than stock and I didn't need a spacer with a 17*18.5 with 30 offset.
 
The usual reason people are using spacers is because they are using FWD offset wheels on a car built for RWD offsets.

So the 40mm wider axle will fit well if the wheels you bolt directly to it are also FWD style offset. If they're RWD offset, you'll get some poke. Which may or may not be your thing.
 
Thanks for the input guys. I'll likely stay with the 1031 and just get me some expensive Swedish gears. Ouch.
 
Doesn't the 240 have a wider front track than rear? I thought that was why a lot of rear spacers are 7mm thicker than the front ones.

So if you want the same track front and rear you wouldn't want to narrow the new axle to match the old one, you would want it 14mm wider.
 
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