Carl Fausett

I have an idea that I have used elsewhere with some success: I could let a few of these out at a lower price to Rennlisters that will install them correctly and want to report back their findings.

If you are interested in such a program, PM me.

Lizard928

Carl,

In the interest of healthy debate, could you take a new Gates or Porsche belt (NOT conti), and lay a new/good used Porsche gear on the belt (smooth part of belt on counter). Then do the same with your gear. Taking high quality macro photos from one side with a light shining on the back.
the same thing again but with 3/4" wrap around the gear itself.

This will help to show some of us how the teeth engage the gear, and will be able to better judge the possible weak areas.

My biggest concern right now is the tooth profile on the gear allowing/causing the tooth to slightly roll. I worry about this as it may stress the tooth causing it to separate from the belt.

Carl Fausett

I have only one new "04" revision sprocket - its the one I paid $400 for from Porsche and sent off to be laser profiled. It may take me a little bit to get it back here so I can do that, but sure.

Cosmo Kramer

I see the point Carl is making here, the Porsche gear in the pics he is showing for comparison is of the old Porsche cam gear not the revised one. Maybe Porsche changed the tooth profile slightly to help reduce wear?

Great work Carl, I know the R&D is costly on this, but any thoughts on a reduced price and going higher volume? I know the MSRP is $413 for the Porsche gear, but it is available through our venders here for the same price as yours. If you could whittle this down a bit you could sell a ton of these as they are a wear item.

Lizard928

Even doing it with the old one is good.

Maybe do it with a 00-01 revision first until you get the new one back.

Jim M.

Do we even know the material specs of the NEW Porsche gears? It's supposed to be an improved design so it stands to reason the specs all changed for the better.

Lizard928

Roger,
While you are getting that picture, could you possibly take a picture of the 00 or 01 gear side by side the 04 gear so that we can see if there is a difference in profile design?

polecat702

I've been running belt drives on my Harleys for over 40 years. Based on the information Carl has provided, I'll buy his gears before I'd buy from Porsche. Carl has INHO produced a superior product, that in the long run will be cheaper and less prone to stripping the teeth off of the belt. Plus the gears are beefer, and use a better alloy. I only want to have to replace the gears once.

I don't know if you guys re aware of this but detergent oil on Gates HTD belts will cause failures. On the old Harleys we had to block off the chain oilers. Gates found that the detergents in the oil caused the belts to delaminate, and shread, or break. Also they went from square teeth to round teeth, and heat was also a problem, in enclosed aluminum primarys, with electric start bikes. This was all harleys had dry clutches. A belt drive wasn't available for Sportsters till the 90's.
All new Harleys can be retrofitted with primary belt drives, but they must run in a special oil from gates, that is nondetergent, yet provides gripping power for the new style wet clutches.

I only added this comment about the belts because some of the cars have oil leaks, and if the high detergent oil gets on these belts it may be a cause for failure that most here don't know about. Our timing belts are made the same way primary, and final drive belts for Harley are made. Prolly have the same tooth profile. The cost is about the same also.
BTW, the final drive belts on Harleys, last almost forever.

namasgt

Roger,

You have a new one in the garage, its from Docs GT with a broken piece of camshaft inside it. But the tooth is still brand new.

Its hanging on the wall next to the maroon sit seating on top of the red parts cleaner.


ALi

BC

An 01:

BC

These are new 01 Wheels bought in 2003. Porsche has not changed the tooth profile. The cogs in question have a different profile because the people involved cannot see the details of the change. Many people operate this way, and it just.... is. Whether or not this completely different profile is good or a bad thing will not be seen until testing, which we know didn't happen.

heinrich

BC are you overlaying a standard belt under a "racing" belt?

Lizard928

If you look at the attached picture, the red would be the cam belt tooth.

On the factory gear you can see that the tooth is much more encased in the gear (arrows)
On Carl's gear, you can see where the tooth meets the belt is not fully cased, and this will cause the tooth to roll, causing the tooth to want to separate from the belt.

If you look at an older belt, this is how they begin to fail over time. If you are using high performance cams this will be further exaggerated due to the additional loading.

Lizard928

BC,

Thank you for those photos.
The latter shows what I am referring to.

I have added two arrow that show there is very little gap holding the tooth tight and preventing the tooth from trying to rotate.

Dave928S

It's a bit hard to tell exactly, but if you look at the last contact points they are both approximately at the end of the radius of the tooth/start of the straight section up to the belt. I can't see that a small or large gap from that point will make much difference ... the tooth is either stiff enough and attached to the belt or it isn't. If the tooth flexes enough to make much difference I'd say it's a crap belt to start with, and would be giving you dynamic changes in timing with rapid engine rpm increase, regardless of the pulley you used. They both have a gap each side, and the gap is necessary for entry and departure of the belt from the pulley because the centre to centre distance of the extreme nose of the teeth is slightly more when the belt is flat on exit and entry, than when its wrapped around the circumference of the pulley.

Maybe the more parabolic shape of Carls gear allows the belt to depart from the pulley better without rubbing the shoulder of the gear tooth opening ... and maybe an old belt tooth fails because it does rub on the more closed profile standard pulley shoulder. Maybe the new pulley profile would wear less on the shoulder and cause less distress to the belt.

The only way you'd really know how a belt behaves dynamically under different loads and RPM, and whether the changed profile is a good or bad thing, would be to use high speed photography.