Daft question: How do you measure Backspace correctly?

Pete · Post by **Pete** » Fri Jul 22, 16 6:21 pm

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

Blue · Post by **Blue** » Fri Jul 22, 16 6:41 pm

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.

Pete · Post by **Pete** » Fri Jul 22, 16 6:45 pm

Fantastic, Blue; thanks.

Getting a bit paranoid about this.

Cheers!!

adrianp · Post by **adrianp** » Fri Jul 22, 16 8:53 pm

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.

Pete · Post by **Pete** » Fri Jul 22, 16 9:05 pm

Ahh!

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

A definite conspiracy!!

adrianp · Post by **adrianp** » Fri Jul 22, 16 9:07 pm

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.

Pete · Post by **Pete** » Fri Jul 22, 16 9:14 pm

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!

Wolfman · Post by **Wolfman** » Wed Aug 17, 16 3:24 pm

Pete wrote:Fantastic, Blue; thanks.

Getting a bit paranoid about this.

Cheers!!

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

Cannonball · Post by **Cannonball** » Wed Aug 17, 16 4:32 pm

The wheel tire combo was a perfect fit Pete

Pete · Post by **Pete** » Wed Aug 17, 16 4:40 pm

It is now, big fella