Page 1 of 1

Daft question: How do you measure Backspace correctly?

Posted: Fri Jul 22, 16 6:21 pm
by Pete
Yes, it is the daft question of the day, and yes I have searched on Google.

DO you measure from the edge of the INNER Rim of the wheel to the centre Boss where the wheel mounts to the axle Flange,

OR:

DO you measure from where the tyre mounts on INNER Rim of the wheel to the centre Boss where the wheel mounts to the axle Flange?


I know you measure rim width from where the tyre mounts on both sides, NOT the edges of the wheel.

I was wondering how manufacturers quote backspace.

Any ideas on the correct measuring process??

Yes, the tyre is THAT tight that I need to get it right.

Thanks in anticipation.


Pete

Posted: Fri Jul 22, 16 6:41 pm
by Blue
You put a straightedge across the rim and measure from that to the wheel mounting face, don't worry about where the tyre fits. Only wheel width is measured bead to bead.

Posted: Fri Jul 22, 16 6:45 pm
by Pete
Fantastic, Blue; thanks.

Getting a bit paranoid about this.

Cheers!!

:thumbright: :thumbright: :thumbright:

Posted: Fri Jul 22, 16 8:53 pm
by adrianp
I've been bitten by this and in my limited experience found it differs from manufacturer to manufacturer. My Cragars are measured as Blue suggested, however my Wheel Vintiques are INNER of the rim to mounting face.

adrian.

Posted: Fri Jul 22, 16 9:05 pm
by Pete
Ahh!

That last point would explain why the Vintiques did not fit as planned on the Dart!

A definite conspiracy!! :evil: :evil: :evil:

Posted: Fri Jul 22, 16 9:07 pm
by adrianp
Yep, 1/4" here and a 1/4" there can make all the difference ! I was lucky enough to get away with it but it all depends on how much room you have to play with !

adrian.

Posted: Fri Jul 22, 16 9:14 pm
by Pete
I stuck the slicks on a borrowed pair of rims and at the moment I do not have 1/4" space twixt tyre and car, so once again fortune has vomited on my Eider down; hence the post!

Posted: Wed Aug 17, 16 3:24 pm
by Wolfman
Pete wrote:Fantastic, Blue; thanks.

Getting a bit paranoid about this.

Cheers!!

:thumbright: :thumbright: :thumbright:
I know this thread is old now, But can you get scrap tyres to experiment with.
I have some spare wheels(mags and cop rims) if that helps, bit of a trek to get them thou :lol:

Posted: Wed Aug 17, 16 4:32 pm
by Cannonball
The wheel tire combo was a perfect fit Pete

Posted: Wed Aug 17, 16 4:40 pm
by Pete
It is now, big fella :thumbright: