Widest rear rim/tire that will fit on the Datsun Roadster (well sort of)

[fairlane292]

Widest rear rim/tire that will fit on the Datsun Roadster (well sort of).

The specs on the wheel/tire combination pictured below may help you if you are trying to get max rubber down with your engine swap (without modifying the frame or mini tubbing the car)

Note the very small clearances and other detail here before running out and buying wheels and tires with these specifications. I will be using a Ford Mustang 8.8 rear differential that will be shortened such that the wheel mounting face location will be 1/4" inboard from the stock roadster. I will be moving the stock leaf springs (which are approx 3/4" outboard of the frame to essentially in alignment with the frame. When you see the clearances below you will understand why these modifications will be made.

Rims: UK Revolution, Rally ET 30, 7.0 x 15, offset +30mm (Fronts are 5.5 x 15, offset +15mm)
Tires: Kenda Kaiser (kr20a) - 225/45zr15 (check online for specs)

The pictures below are using my stock donor car. To test mount the setup I had to bend away the outboard tab of the forward leaf spring retainer. In theory the retainer could be repositioned slightly.
The clearances are: 3/16" upward at the narrowest point between the section width of the tire and the inner wheel well flange sheet metal. 1/8" between the section width of the tire and the rear outward edge of the leaf spring. 1/16" between the section width of the tire and the forward outward edge of the leaf spring. Enough clearance to fully mount the rim with tire and spin the tire at ride height. Not enough clearance for driving but enough for proof of concept and possibly for your reference. Project car will likely be lowered 3/4-1" with a single lowering block on OE leaf springs.

The keys are obviously rim width, rim offset and tire selection. In this case the numbers essentially use up the entire available rear wheel well space in the stock roadster. I spent a lot of measuring before selecting these rims and tires and maybe this info will save you a bit of time.

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[rwmann]

More filling than 205/60R14 Bridgestone RE71 on 14” x 7” Shelby with +1”/+25mm offset rears (and 195/55R14 fronts, same size and offset rims).

[fairlane292]

Just noticed I had a typo on the offset. Had 33mm but correct value is 30mm. +30mm was actually the maximum Revolution offered on this 7” wide rim.

[Alvin]

agreed, wheel/tire fitment is critical. Eric Straw's '69 SRL. Stock body with 225/245 tires:

[Alvin]

Rick's '69 SRL with 15x7 and 15x8 wheels and 225/50/15 tires:

[fairlane292]

agreed, wheel/tire fitment is critical. Eric Straw's '69 SRL. Stock body with 225/245 tires:

At least in the picture the tires look wider than my 225/45s. Everything is well inside the rear wheelwell too; I love to know what suspension and or frame mods were done. By stock body I'm assuming no mini tub then, any chance we can get confirmation on any suspension, frame or tub mods?

[Alvin]

At least in the picture the tires look wider than my 225/45s.

They are wider. 245-width in the rear, not 225.
The rear end is narrowed/linked (a hybrid Ford), with coil-overs at all 4 corners.
https://www.speedhunters.com/2019/05/bu ... -fairlady/

[fairlane292]

At least in the picture the tires look wider than my 225/45s.

They are wider. 245-width in the rear, not 225.
The rear end is narrowed/linked (a hybrid Ford), with coil-overs at all 4 corners.
https://www.speedhunters.com/2019/05/bu ... -fairlady/

Amazing story and build. I did not know about Eric’s car. Thanks so much for sending the link along.

[Alvin]

Amazing story and build. I did not know about Eric’s car. Thanks so much for sending the link along.

Absolutely! He's incredibly talented. We dyno-tuned his roadster and it was wild to be a passenger, enjoy the video and report:
https://www.zcarblog.com/2020/05/01/per ... dster.html

[Gregs672000]

Ya wow... what a tremendous car and sooooo well done. The pinnacle of Datsun Roadster development in all areas.