Little Clanger

Anyone,
when I go for the PPP on my 03 STi, I fancy some decent 18inch rims. The dealer tells me the way to go is magnesium jobbies. I thought mags were crap on anything less smooth than a surface like a race track as constant bumping by road inputs cased fractures which led to them shattering in time (this is supposed to be the case with motor bikes) Who is misinformed, me or the dealer?

Are mags ok for normal road use?

greasemonkey

The WRC cars usually use cast magnesium wheels, and they very rarely run on surfaces that are as smooth as a racetrack, so that tells you a lot. In fact, they seem to be much more durable and resistant to damage than cast aluminium given the corner cutting, ditch hooking, potholing and other punishment they're expected to stand up to.

Suggest you have a word with a good wheel dealer and see what they say about the specific model you're interested in. I doubt any wheel would be sold for road use if they were known to shatter under "normal" conditions. If a particular type of wheel was known to do this, I imagine the cause is more likely to be a design or casting fault rather than a shortcoming of the material itself.

Little Clanger

wise words grease monkey. Common sense really. I wouldnt have thought Subaru UK would advocate selling a product for road use that as not really suited.

Next question - would you think they are worth the (undoubted) additional cost over alloys. The ones I have been advised to get are the "flitters"

Paulo P

iTrader: (42)

I thought magnesium wheels weren't good for road use because they crack and magnesium is dangerous if it catches fire.

I remember Jonny Milner losing his whole celica rally car a few years ago to fire after getting a puncture and the sparks caught the car alight

Paul

Little Clanger

Paul,
this is what I had in mind. I thought the rigidity of mags made em susceptible to stress fractures on sh1te roads. Greasemonkey tells a convincing side though. WDYT?

clintyboy12

You mention the rally cars, but don't the wheels get changed a lot more often in a rally than our regular road wheels?

Paulo P

iTrader: (42)

Yes. I think magnesuim road wheels need changing after a few thousand miles due to cracks

greasemonkey

I've never run mag wheels on a roadcar, so, as mentioned, the best people to ask on this are fitters with experience of the particular type of wheel you're considering.

The trouble with the "magnesium wheels crack and are a fire risk" or any similar sweeping generalisations is that they're often born more of old wives tales and concensus hallucination than fair comment.

When Milner's Toyota caught fire at the Jim Clarke in 2000, it wasn't like he had a puncture and the wheel suddenly spontaneously combusted. He carried on driving flat out for several kilometres on a completely shredded tyre, with the friction eventually setting the wheel alight. If you had a puncture, you'd stop and change the thing straight away, so this situation wouldn't arise.

You're right Clint, rallycar wheels are regularly inspected for cracks and other damage and are often scrapped, but this applies to aluminium wheels just as much as magnesium ones. I don't believe there's a general "chuck after 2000km" (or whatever) rule with the works teams. Most of them seem to sell wheels on when they start to look a bit tatty, and the privateers then seem to get years of use out of them.

stockcar

the main problem with "mag" wheels on the road is that when they get chipped, etc. this can lead to oxidizing which causes weakness (unlike ali rims which are not a susceptible!!).......
need much more attantion than "normal" alloys.....
alyn - asperformance.com

currymonster

Is the reason for the Magnesium alloy wheels weight? If so just get something like Oz Super leggeras, 7KG a wheel for 17s, light as paper!

Cal

currymonster

Tsl do some unfeasibly light wheels in 18 and 19 inch!!

http://www.tsl-motorsport.co.uk/wheels.html

Cal

Apple

I'd once talked to Mike Wood about wheels and the mag versions and seem to remember that there was some agreement / ruling amongst the WRC teams not to use them due to the astronomical cost over a season with the number they'd get through - very nice to have but the budgets wouldn't stretch to using them...

greasemonkey

That just ain't so Apple. Guess they may have been talking about banning them at some point, but it certainly hasn't happened. The WRC teams have been using mag wheels for years, and still are. Are you sure it was magnesium you were talking about, or some even more exotic metal?



[Edited by greasemonkey - 11/30/2003 1:20:08 AM]

Apple

Thought it was magnesium but possibly wrong

It's a couple of years ago so the memory's maybe not what it used to be