RX-7 Spindle Failures

[Eagle7]

A first gen snapped a spindle and lost the wheel Saturday at Grattan. Quite a mess. They were saying it's not an uncommon problem. I was impressed to see him back on the track Sunday and running very competively.
Anybody else experience this? Is the 2nd gen spindle also prone to snapping?

Thanks,

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Marty Doane
ITS RX-7 #13
CenDiv WMR

[lateapex911]

I'll throw in my 2 cents...

I used to do chassis setup and maintennace and strategy for a team of 1st gen SS RX-7s that ran the Longest Day at Nelson, back in the days when Car and Driver went against Road and Track in sister cars. What we saw was consistant bearing failure between 17 and 18 hours. The brakes failed at 12. Like clockwork on both counts.

The second year I decided it was smarter to swap the entire strut at a planned stop around 12 hours, getting new pads, new discs, new bearings and shocks all at once. Saved a ton of time, and we didn't have any issues..

In my IT racing, I see regular bearing problems (slight loosening)...but I repack and adjust often, based on my Nelson experience. I replace the bearings seasonally, but they always look just fine. I run the same spindles that I had on the car at the begining in '97.

I would guess that this was an isolated incident, either caused by an suspect part or by improper setup or maintenance.

I have heard nothing about regular spindle snapping.

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[dyoungre]

I did witness a spindle snapping at Waterford Hills, in 2000. Fortunately, it snapped coming off of a turn, and the wheel stayed captured by the rotor. Driver pulled off.
I inspect my spindles for cracks on the underside, but have never seen any. Depending on wheel offset, I can see some unanticipated bending loads creeping in.

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Dave Youngren
NER ITA RX7 #61

[greendot]

I've been racing 1st gen cars since 1992 (not as long as Jake it seems) and have seen at least half dozen spindles fail. The one at Grattan was typical. The pre-84 spindles especially. Personally haven't seen an 84-5 spindle on an ITA car break, however it must be enough of a concern that an ITA racer was carrying the spare that helped get the car back on the track for Sunday. It's purely a question of fatigue of the material. there is a way to cure this that I've recently learned from the Prod guys, but I haven't build the parts yet.


To answer Marty's question, second gen failures seem far less common. Only know of one of them breaking.

Bruce Wentzel
Green Dot Racing, Inc

[JeffG]

I managed to snap a 2G spindle last season. Looking at the break it had been cracked for some time prior to failure. The side that failed had been abused before I purchased the car and I never though to have the spindle magna fluxed. I will now spend the $10-$15 each to have the spindles fluxed at the end of each season and whenever I feel I've had a hard hit on the front.

Jeff

[lateapex911]

This is interesting. (And a bit worrysome)

Where exactly was the break on the spindle??

I am having a tough time imagining how the rotor would retain the wheel.....I must be confused, but if the spindle breaks won't the rotor be free? Help me out here!

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[ITS5GB]

The break occurred approximately 1" from the threaded end. I've had the car for 2 seasons and have never had any problems. It is maintained by a local racing team that runs 1st and 2nd gen cars that are front runners.In fact, for a 1st gen ITS car it's pretty competetive. I don't think improper setup is a problem. Top 3 finishes at Waterford on a regular basis with 10 to 15 car fields. This past weekend the car was running in a solid 3rd at Grattan with I think a 9 car field when it broke. The car has a long successful history of podium finishes at Nelson Ledges, Mid-O, and Watkins Glen.(In fact it held the track record(long course) at Watkins Glen in 2000)The former owner was Dave Deen, maybe some of you guys know him.I've only been racing a few years. Almost all the guys that run the 1st gen cars at Waterford in IT7 have had some experience with spindle failure. We even had a very well maintained 2nd gen Speedsource car break a spindle last year. As Jeff said, the only way to really check the spindle is to have it magna fluxed. I think also, the setup is to use the 84 and 85 spindles, which have a larger diameter and are stronger. I was fortunate that Rich Miller, a successful Cendiv IT7 racer, had a spare strut assembly with him that he let me use to get the car back on the track for a 4th place finish on Sunday. And by the way, when I pulled the wheel out of the weeds the rotor, caliper, and stainless steel brake line were all there with it!(minus the brand new Hawk blues I just put on).

[Knestis]

Originally posted by JeffG:
... Looking at the break it had been cracked for some time prior to failure. The side that failed had been abused before I purchased the car and I never though to have the spindle magna fluxed. ...

The bothersome thing about crack propagation strain failures of castings or forgings is that they don't have to be truly abused (e.g., crashed or jumped) to happen. Just the repeated loading and unloading, shock, or even vibration will cause that failure to crawl through the part.

Is there a stress raiser where the failure happened? A machined grove or similar? Make sure that parts like spindles aren't nicked before they are installed.

With modern manufacturing processes and tolerances, it's still possible to get a bad batch of parts but it's sometimes scary how regularly they crap out. We had a rear spindle fail on a rally Golf - the RR wheel parted company with the car in a 70+ mph lefthand sweeper, never to be seen again - and after replacing that side, the OTHER one failed just a couple of miles into the first stage on the next event.

Lesson learned.

K

[ITS5GB]

By the way Marty,the Waterford regulars had a great time at Grattan.That was the first time a lot of us had raced there and we had a blast.We are looking forward to next year. Thanks for the freindly welcome to your home track! Come down to Waterford sometime, 2 race weekends to go, late August and early October!

[bcarter]

One of our guys broke a spindle this weekend at speed. Luckily he managed to get it stopped before the wall. 1st gen GSL-SE running in IT1. I tried to post a picture, but it didn't work.


[This message has been edited by bcarter (edited August 11, 2004).]

[This message has been edited by bcarter (edited August 11, 2004).]

[ddewhurst]

The broken rotor thing seems to becoming quite common in the past year in 1st gen RX-7 E Prod racing. I undrstand the speeds & forces are greater but why all of a sudden broken rotors. I don't recall in past years hearing about broken rotors with 1st gen RX-7 E Prod cars. I wouldn't beleive that everone is not hitting the max allowable forces all at the same time. I understand Mazda rotors are no longer available for 1st gen's but they are also breaking if the info I have received is correct.

Have Fun
David

[JeffG]

It broke 30mm in from the thread which is 10mm from where the outer bearing sits. This tapered section of the 2G spindles has many machining steps. I assume that these parts are heat treated after machining, which should provide an excellent surface treatment for fatigue, short of shoot penning.

I can see where the crack propagated in as much as 4mm before failing. When it came off the wheel departed with the hub, rotor and broken caliber as a unit. Luckily it didn't happen at a corner like the kink or turn 12 at Rd Atl!

The process to ask for is referred to as wet, or A/C magna fluxing. The shop I take them to claims they do dozens of spindles a month. It’s cheap insurance!

Jeff

[Eagle7]

Originally posted by ITS5GB:
By the way Marty,the Waterford regulars had a great time at Grattan.That was the first time a lot of us had raced there and we had a blast.We are looking forward to next year. Thanks for the freindly welcome to your home track! Come down to Waterford sometime, 2 race weekends to go, late August and early October!

Glad to have you. Biggest ITS field I've been in yet. Only problem was, you guys didn't wait for me - well I guess Lynn did , he was sitting sideways in turn 1 after passing me on the straight. Glad he wasn't blocking the line.

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Marty Doane
ITS RX-7 #13
CenDiv WMR

[Tak]

If I understand this thread right, are most of the 1G failures here occuring on GSL-SE's running ITS/IT1? If that's correct, I wonder if it has anything to do with running 14" wheels on that car (and rotor failure in EP due to 15" wheels?). The larger diameter wheel will put more load on the spindle and rotor (because the rotor/tophat are cast together)...
Out west here, I havn't seen a spindle failure on an Rx-7 or Rx-3 in over 10 years.

Tak
#29 ITA
(84 Rx-7 with small spindles!)
SFR SCCA

[Marcus Miller]

RE: the E prod failures, I am sure the slicks add to the issue of forces, as well as the larger rims.

M.

[Allen Brown]

I'm not sure about most, but it looks as if at least three of us (GSL-SE) have had this happen.

I'm not sure if the 14"/15" tires make a difference. I might be more along the line of rim offset. In the IT-1 here in western Canada, we can use whatever rim diameter you want, just that we are limited by rim width.

But to be honest, I have never magnafluxed the spindle (I should have), and it's quite possible these are the original spindles that came on the car. Luckily I didn't hurt anyone or myself to learn this little tidbit. I will be doing a seasonal or semi seasonal check from now on. And the break also looked as if it had been cracked for some time.

Oh well...all is well. The car shall be stripped and we are off to the other chassis now....I can't wait for another 70hp or so..


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Allen Brown
#36 IT-1
GT-3 in 2004 or 2005
[email protected]

[rx7its95]

Dave,

You might have seen my car loose the spindle going into swamp in Waterford. My brake line kept the tire in place.

I have a question is one side more prone to break the spindle than the other? My passenger side spindle is the one that broke.

Driver side 0
Passenger side 1

Jorge

[This message has been edited by rx7its95 (edited August 13, 2004).]

[Allen Brown]

Mine was driver's side. This side takes a real beating on curbs that you basically launch the car in efforts to straighten out the chicane.

[ddewhurst]

While talking with one 1st gen RX-7 E Production car owner/driver that the left front GSL-SE broke @ Mid Ohio it was the rotor that broke off the bearing hub. This failure would not necessarly indicate a direct relationship to the rim size of offset IMHJ. Speed/slowdown/heat/casting quality ????????? IIRC second race weekend for the rotor/hub. The ensuing crash caved the left front sub-frame back approx 18" to 24".

Have Fun
David

[dyoungre]

I saw Scott ??? brake an '83 ITA RX7 spindle - driver's side, in that case, coming out of big bend. 13 inch on DOT tires.

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Dave Youngren
NER ITA RX7 #61