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Teaser pics (some performance eyecandy)
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Raceboy  



Joined: 01 Mar 2004
Posts: 2321
Location: Estonia, Europe

PostPosted: Fri Aug 03, 2007 5:16 am    Post subject: Teaser pics (some performance eyecandy) Reply with quote

Finished rear alloy arm and 951 brake conversion (plus torsion bar carrier swap for rear sway bar and yellow 951 M030 Konis) today and installed sandblasted & powdercoated struts w/ yellow Konis.
Tomorrow I'm finishing front end by installing spindles with 951 calipers and discs.
Quality is not the greatest (taken with cell phone) but you'll get the idea.


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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S
'91 944 S2, sold
'82 924S/931 "Gulf", sold
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Chrenan  



Joined: 15 Jan 2003
Posts: 3899
Location: Canada

PostPosted: Fri Aug 03, 2007 5:27 am    Post subject: Reply with quote

Well done!
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Raceboy  



Joined: 01 Mar 2004
Posts: 2321
Location: Estonia, Europe

PostPosted: Fri Aug 03, 2007 5:36 am    Post subject: Reply with quote

Should just add that all brake stuff sans calipers (though soft sandblasted and painted) are brand new: discs are Zimmermanns, pads are Ferodo DS Performance, brake lines are steel braided and fluid is Ate Super Racing Blue.
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche
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Min  



Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada

PostPosted: Fri Aug 03, 2007 6:43 am    Post subject: Reply with quote

Very nice, someone's been busy!

Min
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macBdog  



Joined: 16 Aug 2004
Posts: 1111
Location: Brisbane, Australia

PostPosted: Fri Aug 03, 2007 9:02 am    Post subject: Reply with quote

Nice work! Whats the philosophy behind drilled rotors and not slotted?
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!tom  



Joined: 28 Aug 2006
Posts: 1902
Location: Victoria, BC Canada

PostPosted: Fri Aug 03, 2007 9:28 am    Post subject: Reply with quote

macBdog wrote:
Nice work! Whats the philosophy behind drilled rotors and not slotted?


I like how you ask about the philosophy, rather than the science.

Seems I've heard a few people debate the science, but I'd expect the far greater surface area on the inside edges of the holes would provide superior cooling than slots or a uniform surface.

I know the holes sound neat on my motorcycle front disk brake, but that's a solid rather than vented rotor that's been drilled (from the factory).
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Raceboy  



Joined: 01 Mar 2004
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Location: Estonia, Europe

PostPosted: Fri Aug 03, 2007 2:28 pm    Post subject: Reply with quote

These discs are drilled already from the factory.
I would choose non-drilled and non-slotted discs but they weren't available at the time for '86 951. I think I can live with that and being used drilled and solid rotors, it's actually pretty hard to tell the difference.

What matters with cross-drilled rotors is the proper pad selection and heat-cycling, that prevents it cracking prematurely.
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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche
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morghen  



Joined: 21 Jan 2005
Posts: 8180
Location: Romania

PostPosted: Fri Aug 03, 2007 4:18 pm    Post subject: Reply with quote

very nice looken and i'm sure..very nice drivin'
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Raceboy  



Joined: 01 Mar 2004
Posts: 2321
Location: Estonia, Europe

PostPosted: Sat Aug 04, 2007 3:37 am    Post subject: Reply with quote

Hehee, right now the ride is terrible because of the totally f***d up alignment.

I finished the front axle today and too some photos of it.

These are fronts:


These are rears:


Rear axle:

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'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche
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Hoboceratops  



Joined: 16 Aug 2006
Posts: 156
Location: Atlanta, GA

PostPosted: Sat Aug 04, 2007 3:35 pm    Post subject: Reply with quote

Older brake pads would expel gases at high temperatures which could form a layer between pad/rotor and lower braking power. For more recent brake pads this is much less of a problem. The idea of slots and holes is to get these gases out from between the pad and rotor, and holes are supposedly better at this, but slots are more than adequate for todays brakes. Slots also have the bonus of scraping the pads off, which can form a sort of glaze that hurts baking [left this typo in because I think it's funny that glaze made me hungry for some baked goods].

Holes/Slots do nothing for cooling, in fact lowering the total mass will make the rotors worse off in terms of cooling.

Drilled holes are pretty good at making stress points for the rotors to crack though, and most companies that sell them do not recommend them for track use. Basically all they're good for is looks.

So in terms of performance, Slotted > Solid > Drilled

Edit: This is for normal iron rotors/brakes. Dunno how different materials will behave.
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!tom  



Joined: 28 Aug 2006
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Location: Victoria, BC Canada

PostPosted: Sat Aug 04, 2007 4:20 pm    Post subject: Reply with quote

Hoboceratops wrote:
Holes/Slots do nothing for cooling, in fact lowering the total mass will make the rotors worse off in terms of cooling.


A solid rotor (as in, no holes or slots in the friction surface; a vented rotor is obviously far superior to the solid 4 bolt rotors on our 924's) would have a higher heat capacity than an otherwise similar slotted or drilled rotor, due to the fact that there is more material.

However, I disagree with your conclusion that a solid rotor would cool better than a slotted or drilled rotor (assuming a conventional arrangement). A higher surface area will promote a higher rate of heat transfer from the rotor to the atmosphere, and of the 3 discussed arrangements, a drilled rotor would have the highest surface area.

I'm not saying that drilled is best, nor am I saying that people justify drilling their rotors due to the higher surface area hence rate of heat transfer, but I am saying that a drilled rotor will cool faster than a solid or slotted rotor.

The drilled and slotted rotors will also have less surface area acting against the brake pad, which will in and of itself decrease braking performance. However, the above mentioned justifications for holes and slots may or may not counteract the decrease in available surface area.

If you take cars that are identical in all ways other than their rotor arrangements, and stop each of them from the same speed in the same distance on the same road, the car with solid rotors would have the lowest rotor temperature once stopped due to the higher heat capacity of the solid rotor.

However, if you're driving all three cars down a very steep mountain and really use the brakes a whole bunch, the increased cooling capacity of the drilled rotors would ensure those brakes were the coolest, and the solid rotors would be the hottest. In both cases the slotted would be in between the two extremes.

They (drilled rotors) look novel, and they sound kind of neat, but I'd expect if they were all that much better, they'd be far more common than they are.

They are common on motorcycles which do not have vented rotors -- and they tend to be steel.
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Hoboceratops  



Joined: 16 Aug 2006
Posts: 156
Location: Atlanta, GA

PostPosted: Sat Aug 04, 2007 4:56 pm    Post subject: Reply with quote

Cross-drilling is really only a way to make the brakes lighter because out-gassing isn't a problem; and while I know the surface area to mass ratio makes sense, by all reports cross-drilled rotors run as hot or hotter than vented solid rotors.

Cross-drilling does make rotors the lightest of all the methods though, and I guess some think they look cool (I think they look goofy, slotted imo).
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morghen  



Joined: 21 Jan 2005
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PostPosted: Sat Aug 04, 2007 7:08 pm    Post subject: Reply with quote

oh i love those wheels....can we get a picture of the car?
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ihatesissycars  



Joined: 14 Jan 2008
Posts: 17
Location: Uk, Hampshire

PostPosted: Mon Jan 21, 2008 1:08 am    Post subject: Reply with quote

Did the ally arms widen the track of your car by any amount?

I'm having a problem with my own car after swapping the rear beam!

http://www.924board.org/viewtopic.php?p=204344#204344
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924RACR  



Joined: 29 Jul 2001
Posts: 8325
Location: Royal Oak, MI, USA

PostPosted: Mon Jan 21, 2008 1:47 am    Post subject: Reply with quote

We did recently refit the stock steel rear trailing arms to a 924 (early) racecar which had been fitted with the 924S alloy arms (for numerous reasons); I can confirm that there was a loss of track (having now the steel arms), perhaps 20mm per side?

OTOH, having read your other post - these were 924S alloy arms, interchangeable with the steel ones; not sure why on your car they're not apparently interchangeable, if you've already tried all the adjustments...
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