Racing on cast wheels

[richie]

There was an incident at Drachten the other weekend where a bug crashed due to[from what i have read and been told] a cast wheel failing,they arent desinged for the abuse slicks and a sticky track will give them,just something for everyone to think about,there is a reason porsche etc made such high quality wheels,relpicas are not made to the same standards

cheers richie

[Bruce]

I disagree, Richie.  It's street driving and road racing that cracks and breaks wheels.

If you're only going straight, there's no side loading on the wheel center.  When you're accelerating, the torque of the axle is transferred to the wheel center evenly by all the lug bolts.  That torque is then transferred evenly to the rim of the wheel.  In other words, the load is spread out.

When you are cornering, the side load is concentrated mostly at the part of the rim closest to the ground.  Not spread over the whole wheel.

I know one Lounge member who owns a set of real BRMs.  He won't hesitate to use them on the track.  But when on the street, he purposely goes around corners slowly.  Slower than when he uses aluminium wheels.

[speedwell]

andy spilkoman had a real empi 5 who exploded some year ago

http://cal-look.no/lounge/index.php/topic,2222.msg28501.html#msg28501

http://cal-look.no/lounge/index.php/topic,4247.msg59673.html#msg59673

[andy198712]

Pretty sure the wheels on my ninja are cast and they get huge strains!!

But a poor quality cast wheel is dangerous I would totally agree!
And I would go further to say a well forged wheel would be better, but a good cast wheel would be good too.

I guess it may well come down to quality control also....

[Greg G]

There have been forged and billet center wheels break under extreme conditions in the top classes of the NHRA. Its like the best crank money can buy cracking when detonation takes over. Even the best wheel can break when chattering the tire takes place. We just normally don't shake it hard enough, but with the HP of some of the cars and the strength of the transmissions and axles, there will be breakage somewhere else, possibly the wheel. We sill be seeing cast wheels obviously break first.

[nicolas]

i have to agree with Richie. i will never run slicks on my 8 spokes. they have hold up with trips over bad roads, but risking to run a slick with a sticky track on a 30-40 year old rim that has been known to crack is a bad idea.

but it has a lot to do with the design of the said wheel as well. 5 and 8 spokes just won't hold up in the long run i am afraid. and it also has to do with how much power/abuse you put on them.

[Fasterbrit]

Speak to Paul Medhurst at Type3 Detectives. He recently had a vintage Vw cast wheel explode on tyre fitting machine. One half of the wheel disappeared through the ceiling of the workshop! Cast wheels fatigue with age something chronic. Kind of like a ticking timebomb...
I wouldn't fancy racing an older cast wheel. Particularly one that's made of brittle magnesium, is 30+ years old and worth a small fortune 

[dragvw2180]

             Cast wheels are for driving on the street with street tires and not for racing.  The first problem I see with them is weight, they are heavy and were never designed to take the stress of slicks and high HP launches, just like my light Mitchell racing wheels were never intended to be driven on the street and cornered hard.  I would not want to risk the investment of the BRM's either, not because of weakness but because of replacement costs .  Mike McCarthy