deep dish 13" rear wheels - issues?

[340i]

Our team has some three piece spun aluminium (5mm thick) wheels (made by arrow wheels, new zealand), they're 13"x7" (5" inner and 2" outer). To reduce drive-axle weight and increase the allowable angle of the wishbones, we're considering reversing the rear rims so that they're deep dish style. Has anyone had experience with doing this, and is there any issues with setting up a car like this? we've seen a couple of teams in last years australasian comp running this style (monash?.., but not too many teams do.
cheers

[340i]

Our team has some three piece spun aluminium (5mm thick) wheels (made by arrow wheels, new zealand), they're 13"x7" (5" inner and 2" outer). To reduce drive-axle weight and increase the allowable angle of the wishbones, we're considering reversing the rear rims so that they're deep dish style. Has anyone had experience with doing this, and is there any issues with setting up a car like this? we've seen a couple of teams in last years australasian comp running this style (monash?.., but not too many teams do.
cheers

[Brian Evans]

I have a car (not FSAE, a historic sports racer) that has 12" wide rear wheels with 3" inner and 9" outer sections, two piece spun aluminium. The question I would ask myself would be the increased loading developed during cornering on the wider outer section, ditto what would happen to wheel bearing loads, and what the potentially shorter suspension link length might do to geometry.

Brian

[Jersey Tom]

Would make your rear track appreciable larger, no? Or if you kept the same track would make your a-arms shorter and get less control of wheel inclination through travel. That, and as was mentioned, you'll put more load on the wheel bearings.

It's all tradeoffs. Try to figure out what you'll lose vs what you'll gain.

[Fil]

The only reason we run them is because we want radius rods on the rear suspension. There is no other way to get the radius rod to clear the wheel than to run the massive offset. The load cases are much bigger because your running a much larger scrub radius. There aren't too many issues with this particular layout. its the same as designing short long arms. We have also designed one piece cv in hub, so we run slightly longer drive shafts.

Im pretty sure UWA and UNSW run large offsets like we do. Its mainly a by product of trying to get the wheelbase down, pulling the driveline closer by mounting straight to a engine plate and having to run radius rods.

Also 5mm rims are bloody huge, get onto Whitehorse industries in melbourne they do most teams in aus, you can get much thinnner rims done.

http://www.metalspinnersaust.com.au/

[js10coastr]

mmm... 13" deep dish pizza....

[Craig Winters]

Sorry for the thread revival, but as I am one of the directors at Whitehorse Industries I thought I would point out a couple of things.

13" wheels can be made by us in 4mm 6061 (heat treated), 3mm and 4mm 5005 (non heat treated) aluminium. Additionally if you source your own metal 2.5mm 6061 aluminium in O temper can be used. This can be sourced from Airport Metals in Melbourne.

Cheers

Craig

[Craig Winters]

call me if you want wheels

03 9739 5955

[Claude Rouelle]

Additional perspective: If you change the rim offset you not only change the track but you do change the scrub radius (also called KPI trail) and THAT could seriously change...
- The driver steering effort and feedback
- The Mz and therefore the compliance due to longitudinal forces
- The camber variation in heave, steering and roll (or combined motions)
- The ride height change and the corner weight variation is steering
- The spring and ARB motion ratio: check your kinematics software (or Catia or solidworks); you could be surprised!

Better simulate that!

I remember a mistake made when I was in F1 (early 90's). The quality control was not what it is (or is supposed to be) now and that department did not spot a change in rim offset of 3 mm from one set of rim to another.It was a rim manufacturer error. During a test we did change the tires (well effectively the wheels). The driver went out. There was a small "chicane" at the exit of the pits. He called me on the radio: "These are not the same tires". I was thinking; "come on how can you say that just after 300 meters, at about 80 km/h and 0.00something lateral G and the tires are not even at operating temperature....!". In fact the tires were the same. They were new and cold; that was the only tire difference. The track was 6 mm difference, not such a bid deal but the scrub radius went from 13 to 10 mm. That is 30 % difference and that a good driver will feel it!