Van Diemen Question: Front Steering Arm Attachment Hardware

[Craig Henry]

Do all RF98 and newer front steering arms attach to the upright using M8-1.25 hardware? If yes, why was the upright tapped for metric versus imperial (5/16-18) hardware?

Craig

[redcar9]

Do all RF98 and newer front steering arms attach to the hub using M8-1.25 hardware? If yes, why was the hub tapped for metric versus imperial (5/16-18) hardware?

Craig

They're a few different types of hubs.

What I had to do was use a thread identifying tool to check. Used it all over the car to find the best fit. I think the newer billet hubs I got from Primus are metric. No clue as to why it's not SAE like the rest of the car.

[Craig Henry]

Hi Nick,

Thanks for taking the time to reply. Thread pitch gauges, micrometers, and verniers have always been close by for most of my life as I try to inspect, reverse engineer, and design better solutions over the decades...

My question was purposely vague, and I should have asked better.

Issue: I have the same billet hubs on the bench. I need to use RF98 "OEM" steering arms and a M8 socket head cap screw head interferes with the arm's recessed pocket side walls when trying to attach it to the upright (I was mistakenly calling the upright a hub last night.) A M8 socket head cap screw head is 0.043" larger in diameter than a 5/16" socket head cap screw. The smaller diameter 5/16" bolt head clears fine, but the upright isn't tapped for it. I can fix the issue I'm having (install a 5/16-18 threaded insert in the upright or turn the M8 bolt head down.)

I just wanted to know if the original RF98 OEM steering arm attachment to the uprights were intended for use with 5/16" bolts versus M8 bolts.

Seems odd that a UK company would tap two holes on an upright for metric bolts when the vast majority of the hardware used on the car is imperial units. If others are using M8 bolts to attach OEM RF98 steering arms to their uprights, then the "OEM" RF98 L/R steering arms I purchased might not be true OEM spec parts.

Also, is it safe to assume you are using the newer steering arm design and they bolted up fine to your billet uprights using M8 SHCS?

Thanks for all the help,

Craig

[redcar9]

Hi Craig!

I think I'm following you now with your concerns. I changed the steering arms and they seemed to fit better.
The OEM RF00 ones that I had the hole spacing too far apart if I remember correctly.

You could probably clean it up with a file, but I wanted to try different arms.

I did a depth check on the upright and ordered both SAE and metric bolts from mcmaster-carr to see what was a better fit. I can't remember want I landed on, but the head of the bolt says 12.9. I think that's metric.
https://www.dropbox.com/scl/fi/svojw...=moowq355&dl=0
https://www.dropbox.com/scl/fi/l5eul...=39xkntv3&dl=0
https://www.dropbox.com/scl/fi/q6e6m...=y33o3e96&dl=0

I went with these arms.
https://velocityhaus.com/products/vd...bb4063a3&_ss=r