Help needed on back spacing on 20 inch rims on a 57 chevy stepside

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JC Rousseau
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Joined: Mon 08 Jan 2018, 11:03

Help needed on back spacing on 20 inch rims on a 57 chevy stepside

Post by JC Rousseau » Wed 07 Feb 2018, 14:20

Hi all

I want to fit 20 inch rims on my 57 3100 step side i will be ordering them from the us

1)Its a 57 chev 3100 step side
2)1983 jag front and rear suspension
3)Airbag front and rear
4)20x8 in front and 20x9 on rear
Anybody out there with the same setup?

I need to know the backspacing front and rear before i order

I have all the parts to do the job but need the rims to start ,so that i can get the lowered height right (on the floor) :)

I hope it all makes sense
If anybody has a better idea of how to get the back spacing please feel free to tell me

Thank
JC
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Burnthosetyres
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Location: Durban (Home of Sharks rugby) RSA

Re: Help needed on back spacing on 20 inch rims on a 57 chevy stepside

Post by Burnthosetyres » Fri 09 Feb 2018, 06:44

The offset is determined by the dish on the rim.

It’s a hard one to determine in theory on email, also depends on how he front rack was mounted.

What you have to ensure is there is no touching or rubbing, normally you order the rims first and the suspension geometry is set up from there....

Also if the front rack is mounted horizontal on Jag you will never get the toe in right, must be mounted with a 7 degree rake. Rather take it to an expert, measure twice cut once.....
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jlebenon
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Re: Help needed on back spacing on 20 inch rims on a 57 chevy stepside

Post by jlebenon » Sat 10 Feb 2018, 19:01

You can measure the required backspace If the suspension is setup already
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Burnthosetyres
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Re: Help needed on back spacing on 20 inch rims on a 57 chevy stepside

Post by Burnthosetyres » Mon 12 Feb 2018, 06:47

Does the bin and fenders not also need to be mock fitted?

I had to semi tub by bin and I’m running 15’ albeit 295’s
'A Camaro is a little animal that eats Mustangs!'

JC Rousseau
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Joined: Mon 08 Jan 2018, 11:03

Re: Help needed on back spacing on 20 inch rims on a 57 chevy stepside

Post by JC Rousseau » Mon 12 Feb 2018, 11:12

Thanks for the info
I have the suspension but not fitted just need the wheels as the man doing the suspension for me asked for the rims and suspension together .
Cab ,load bin and chassis are still together and will go to the welder like that with suspension.I will try get fender and hub measured when suspension has been mocked up
I will have to make a big tub for the wheels 8O

dom
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Re: Help needed on back spacing on 20 inch rims on a 57 chevy stepside

Post by dom » Fri 29 Jun 2018, 17:21

Your XJ axles should be 1550mm (61") from wheel mouting flange to flange. Measure the body and calculate the backspacing to suit.
If you are worried about the front rims hitting parts, use the original XJ wheels as a reference. If you are lucky sombody here has smaller diameter rims but a similar setup otherwise.
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