ALFAGTV6.COM

[MD]

Anybody experiencing stub axle bending under circuit racing conditions?

Is there a difference in the size of the stub axles between the 2 litre and 3 litre powered cars?

Appreciate some feed back.

Cheers.

[Giuliettaevo2]

There is a topic somewhere on this forum about that...

"Spindle flex" comes to mind...

2.0 and 3.0 have the same stub axles.. Only SZ/RZ has different ones i believe.

They do indeed flex a bit. I've seen proof of this, pictures where a brake discs made marks on the spindle while at rest there was a few mm's clearance...

[Giuliettaevo2]

found it;
click here

[benski105]

i always thought the 2 litre cars had different stub axles. or maybe just the older 2 litre ones.
i have been using ones from a 75ts with next to no clearance between the rotor and upright with no issues.

[kevin]

Our stub axles are different here . The gtv6 ones are bigger. They take bigger bearings . The guys who run 10 inch slicks use the alfa sei hubs as even a bigger bearing .

[MD]

In April 2011, Scott Venables wrote this in part ..

Did you figure something out Jim? At our last club sprint meeting a friend of mine with a 75TS turbo racer was having trouble with the inside of the wheel rim rubbing on the bottom ball joint stud.

This is potentially an issue I am having with 3.5* camber, 50mm offset and upside down ball joint on 8" rims , racing rubber.

If someone has the spindle size numbers, that would be very useful.

Here's a photo of an inside rim scuff. (Ignore the continous mark. That is simply from a lack of a turning circle stop.)

Kev. People I ask around here tell me that all our spindles are the same size. Only size difference is in the smaller units on early Alfettas.

[scott.venables]

Inner bearing ID 29mm
Outer bearing ID 19mm
Distance between inner races ~ 35mm when installed

JimK mentions the other spindle sizes in his book, inner bearing IDs of 32 (Alfa 6), 31 (SZ/RZ, 75evo, special heavy duty TS). 75s, GTV6, late Alfettas have 29mm and early Alfettas 26mm. Not sure where the transaxle Giulietta fits into this, I would guess 29mm.

Scott

[MD]

Thank you Scott. Useful info to have.

Never had a problem with 35 neg offset but otherwise everything the same. Mind you, I am not extemely concerned at this time because I think the marks on the rim are the likely results of:-

1 Some rim flexing
2 Some stub axle flex
3 Some localised rim distorion.

The latter being the most likely the cause. I have since installed a replacement true rim and will do some more testing on the same track and see if the problem continues on a known good rim.

Will update later..

[Mats]

MD: is it just the picture or are those marks not exactly radial/along the direction of rotation? Of so, how is that possible if it's touching somewhere?
On the same subject, what in the world is it touching? Can't imagine anything that would rub in that location..?

[MD]

Hi Mats. I see you have been doing a bit of head scratching. Me too.

Well if you remember I use the upside down ball joint set up. This gets the underside of the LCA to within about 10-11mm close to the inside radius of the 16" wheel. Now depending on the style of wheel and the offset, this will determine to a degree the amount of clearance.

The reason for the moving location of the marks is due to the triangular shape of the LCA. It is the leading edge of the LCA that is acting like a "cutting blade on the lathe". I have since ground off and rounded this part in an effort to minimise the point of friction.

The photo I have supplied could help a little but I just don't have one exactly to totally illustrate my point.

I hope this helps.

[kevin]

Md , I think it's your rim distorting off a kerb on the track with those marks .

[MD]

Very likely you are correct Kevin. A fresh rim should tell the story.

[benski105]

i used to to have issues with my rotor rubbing on the upright due to play in the bearing/stub.
the issue was cured by changing my bearing tension technique, i used to just use feel and a bit of sense, but since using the factory recommended bearing set up and changing to the 75 ts uprights the issue has gone away.
i find it hard to believe that the upright is actually flexing.
i keep a constant eye out for that kind of thing and have yet to see evidence of rubbing.

im curious to see what comes out.

[kevin]

I run my discs so close to the upright that I actually remove 1mm of material on the upright so my 305 mm discs fit inside my 15 inch rims . I have also been aware of this issue since Jim first noted this problem but thankfully have found no touching or scrape marks even when I was running full slicks . But they were only205 mm wide . The guys here who run 285 mm wide full slicks say they do get get spindle flex but I yet seen it .