JimsCorvettes

NOTE

SINCE I POSTED THIS, I HAVE FOUND OUT THIS IS NOT A GUMBY WHEEL.

Someone posted the correction further down.... however, the cracked wheel is real!


For those who have driven the road course at CMS, this happened during the transition from the inside track back to the oval track in turn one. I got a point by to the right of the car in front of me and did not want to lose any speed so I entered the big oval track what amounted to be a bit too early. I thought at the time what a hard hit (from the flat apron to the 24 degrees banking in turn 1) but thought nothing of it and got back to making my way around through turn two. At this time the hard hit was a distant memory even though it happened 10 seconds ago. I then felt the front of the car was just not responding like it had in my earlier sessions. (again, the hard hit was a memory and only after to talking to a track buddy of mine while in the pits did I put the two events together... hard hit = cracked wheel... thanks Tom) So I backed off my speed on the back straight (to 135, still way too fast after learning I was running on two spokes) and entered turn three. All felt ok until the next lap when I was exiting turn 2 again and the front of the car just did not feel right. I was thinking cracked rotor but don't know what that feels like. I did think the front of the car had a solid feel to it and I experienced a floating feeling so I backed off the speed even more (under 100) in turn 3-4 and headed to the pits.

This is a OEM Speedline wheel with a Toyo R888 tire. To my surprise, I was running on two spokes for a lap and a half while I was trying to figure out why the car did not feel the same. Yikes, what a feeling I had while looking at the wheel. I learned keep in your memory banks ALL track anomalies while driving in your session and when something "minor" happens really think it thru and convince yourself to pit and check your car. If I decided to stay out and finish my session (at the time I was about half way done) I could have had a very different story to tell.

brkntrxn

Which track?

brkntrxn

Which track?

jcsperson

By CMS I think he means Charlotte Motor Speedway.

brkntrxn

I missed that, thanks.

Charlotte has one of the most abrupt transitions of any roval. Although I won both I my races yesterday on 18's, I actually prefer to run 17's there so I can have a taller sidewall tire and cushion that transition.

Kevin

JimsCorvettes

Same subject:

http://forums.corvetteforum.com/c6-t...wheel-why.html

I see why you run 17 inch wheels.

sperkins

I've known folks that have busted the windshield in that transition. It's very brutal if you get it wrong. Glad you caught it before something worse happened.

ZedO6

Might not be a huge contributing factor considering CMS infield transistions, but chroming any wheel, especially a cast AL wheel, only weakens it.

This phenomenon is known as Hydrogen Embrittlement. Basically this means that the ductility of the metal is compromised and load bearing stresses that would normally bend or flex the metal, can actually cause cracking and in the instant case, catastrophic failure. This can occur with stresses that were well within the wheel's structural boundaries, prior to the events responsible for the Hydrogen Embrittlement, i.e. chrome plating.

I personally would never race or do HPDE's on a chromed wheel.

JimsCorvettes

Thanks for the advice. I have a set of comp gray gumbies in the garage. Looks like they will see some track duty.

waddisme

Not a good weekend for wheels and tires there.

larryfs

I have heard bad things about chroming wheels, and painting wheels. just leave them the factory finish.

spdislife

I learned that one when I cracked 9 of 10 spokes on a chrome plated speedline at Shenandoah this April. Fortunately caught it in time before it let completely go. Still need to replace the backs so if anyone has a set of rear speedlines 18x10.5 to sell let me know.

victorf

Those are not Gumbies. OP has normal cast Speedline wheels. Gumbies were forged.

froggy47

Picture of Gumby?

shakedown067

JimsCorvettes

Whoops. I thought the gumby name came from the spokes on the wheel look like "Gumby".

I see the difference now. Thanks for the picture!

ZedO6

Good info shakedown067. I'm a C5 guy and appreciate the education on the C6 wheels. I see a lot of the 5 spoke cast Speedlines with spoke failure like the OP experienced. Street road impact damage seems to result in the same failure.

I've been in the wheel business...many chromed OE wheels are REPAIRED and then chromed. This is a very common practice. Much easier to "upgrade" to "chromes" than try to match the factory paint on a repaired wheel.

Something to consider when buying used OE chromes.

db2xpert

I've had spokes crack on Fikse rims on two dofferent occasions, not from any specific impact. Didn't notice anything while on track, saw when re-torquing the wheels.

trackboss

Zed06, I am aware of hydrogen embrittlement. What are your thoughts about nickel plating on steel? It is very commonly done on race car suspension components. Just about all the high end nascar cup teams nickel plate a frames and spindles. Not to mention brakeman and pfc nickel plate forged aluminum calipers.

ZedO6

I believe that nickle plate is used in applications where surface hardness is the goal. The bearing surfaces on a spindle and cylinder surfaces on a brake caliper would benefit from this process. I don't see any benefit to the torsional and compression loads a wheel is subjected to, but I could be wrong. I have zero experience with nickle plate.