Primary Drive Aluminum Sprocket

Studboy · Mar 29, 2005

Previously, I have bought 2 of the Titax brand self cleaning aluminum rear sprockets for my YZ250 from Rocky Mountain MC.

They seemed to be good quality, with self cleaning grooves on both sides of the sprocket, and a quality fit and finish. After riding with them for a while, they have held up great! As well as any other product that I have tried, and they were a great value at $29.99 a piece.

Recently, I decided to change my gearing back to a 50 from a 51, so I pulled out the Rocky Mountain MC catalogue, and lo and behold they no longer sell the Titax sprockets, but now sell the Primary Drive sprockets instead. I ordered one of the 50 tooth self cleaning aluminum rears, for the same price as the Tusk (29.99).

When the order showed up, the sprocket was packed in a huge protective cardboard box which looked like it should enclose a high quality product.
I pulled out the sprocket, and instantly realized the absence of cleaning grooves on the back side of the sprocket! :pissed:
The sprocket mounted up fine. After two days of riding with the sprocket, all I can say is that it is junk. After one hour I could see the wear visually occurring, I have never had a sprocket wear this fast. :( I am running a fairly new (definately well within specs, I measured it) gold racing chain. The chain and sprocket were lubed 4x a day (about once every hour of riding time) with Ultra Film chain lube.

Rocky Mountain, bring back the Titax!!! :cool:

Throw away the Primary Drive!!! :moon:

KX02 · Mar 29, 2005

Thanks for the warning! I've got a pd x-ring chain that seems to be holding up OK, but I've never tried their sprockets.

Studboy · Mar 29, 2005

Their front sprockets are OK. Their chains also seem to be decent for the price. I'm not sure about the steel rears, but steer clear of the aluminum rear.

jboomer · Mar 29, 2005

I've run the complete PD set (f/r steel and x-ring chain). The rear sprocket, when layed on a class coffee table had an eight inch warp on one section...I noticed this after I went through 4 sets or so of sprocket bolts (kept loosening up after every ride). The x-ring chain seemed fine, but it broke one day at the track (many factors come into play here..ie. it was very muddy, mud was packing in my c/s cover, chain may have been on the tight side) and cracked my case. It was the master link that broke. On a smaller bike than my 450, I wouldn't hesitate to use them again (although I would pay more attention to the "trueness" of the sprocket before using it)...but these big bikes with mucho torque need a better quality drivetrain in my opinion.

moabdaze · Mar 30, 2005

Studboy,

Thanks for the update, I was planning on ordering tonight but think I might pass. What do you think about trying steel f/r on a CR250 that gets ridden hard and subsequently goes thru a lot of sprokets? I have normally used renthal but they are so damn expensive. I wouldn't mind trying it to save some money, but don't want to risk case damage or rapid wear in the process. Just wondering what you think. Hey, did you make it down to Sahara this last weekend?

bclapham · Mar 30, 2005

hhmmmm. i looked for the Titax since i had good luck with them, but had to buy the primary drive. mine looks good, the cleaning grooves are on the outside. new counter sprocket and gold ERT chain with jaybirds susperlube- its got 2 hours of hard trail riding (LOL) and 6 races on it, still looks good- maybe a bit of action on the surface of the teeth but nothing more than normal.

however, look on the Rocky front page- they have the Titax on closeout now for $20- maybe i will buy a couple

bclapham · Mar 30, 2005

BTW- as for sprocket bolts- i recon on a thumper you need new ones with every sprocket change- we had a CRF250 with a brand new Tag sprocket- now matter how we tightened it, locktite etc etc it would come loose in 5 mins.- nearly got stuck out on the trail. The bolts must stretch or somthing, and the locknuts loose their lockability quick.

bedell99 · Mar 30, 2005

I just bought the primary drive aluminum sprocket with a new chain and it is working awesome. I thought it was a very good deal.

Erik

Studboy · Mar 30, 2005

Hmmmm... maybe my chain is junk? I've only got about 5 hours on it and it has been well lubed... I'm going to take it off and measure it again this weekend just to make sure. I didn't see this sort of wear on the old rear.

bedell99 · Mar 30, 2005

I have 2 rides on it stud, I know that is not much but they seem to be fine.

Erik

velosapiens · Mar 30, 2005

i don't know why any grownup would use aluminum sprockets. it seems like a good way to throw money away to me.

i use the primary drive steel sprockets for $15 each, and they last around 4000 miles of hard offroad riding for me (250sx and 300exc).

also, i would NEVER put a new sprocket on with a used chain. even in a few hours of use a chain will stretch and wear to fit an old sprocket, then it will chew the living crap out of your new sprocket. this is especially true for non-o-ring chains that wear very fast anyway.

-mark

mtk · Mar 30, 2005

velosapiens said:
i don't know why any grownup would use aluminum sprockets. it seems like a good way to throw money away to me.

Particulary when Ironman sprockets are available. Only slightly heavier than aluminum and WAY more durable.

Jaybird · Mar 30, 2005

Ironman sprockets are "too" hard. They are through hardened and can actually cause problems.
A good case hardened (rear or cs) is a much better choice for a steel sprocket, as the softer core actually helps to absorb some shock load. A super hard sprocket will allow this energy to be passed along to the other parts of the drive, including bearings.

Studboy · Mar 31, 2005

Jay,

I was wondering, have you had any experience with the P/D stuff?

It seems like the $20 RK standard chains that I was using are outlasting the P/D Gold racing chain... same lube schedule, same bike. I have been using the Ultra Film for a while now. I ran the stock sprockets on my YZ through three chains (2 years and 3 topends!) before they started to get thin and I replaced them.

The P/D sprocket is on my sand paddle rim.

mtk · Mar 31, 2005

Jaybird said:
Ironman sprockets are "too" hard. They are through hardened and can actually cause problems.
A good case hardened (rear or cs) is a much better choice for a steel sprocket, as the softer core actually helps to absorb some shock load. A super hard sprocket will allow this energy to be passed along to the other parts of the drive, including bearings.

Care to explain how this phenomenon works? Because anything I've ever read about hardening problems had to do with parts shattering from impact loads due to through-hardness. I'm not seeing how a soft core is going to absorb shock loads. In addition, the only information I can find on Ironman Sprockets says they are heat-treated chrome moly steel. That doesn't necessarily mean they're through-hardened.

bedell99 · Apr 4, 2005

Actually now I have 4 rides on it and it showing signs of wear, but I always figure that is normal with aluminum sprockets.

Erik

Jaybird · Apr 5, 2005

mtk said:
...Because anything I've ever read about hardening problems had to do with parts shattering from impact loads due to through-hardness...

Exactly.
Too hard is trouble.
Without doing an ansys simulation and uploading it, you will simply have to trust that a resiliant, soft core will absorb shock load. A hard sprocket with no soft core has a harder time obsorbing shock loads, and is exactly whey they are more prone to shatter.
To be as fair to Ironman as I can, they don;t have much meat on them to begin with. They are cut nearly to what depth a case hardened steel sprocket would have the teeth hardened to to begin with. The profile of the sprocket alone may provide some flex for absorbsion.
But I'm biased against steel sprockets period. They only mask bad maintenance, imo. In fact, I see no gain from them whatsoever, accept for making it easy to get by with stretched out chains longer. And if a sprocket will last until your chain absolutely peels apart from age and lets loose while you are aboard....is it really a gain to begin with?

Erik,
It isn't normal for a quaity aluminum sprocket to show wear unless there is an alingment/adjustment problem, or the chain is stretched.

I'm not familiar with the PD products, other than what I read on the boards. 7075-T6 aluminum is fine for sprocket use...I have no idea what PD's are made of.

bedell99 · Apr 5, 2005

The chain was brand new. I usually go thru about 3 sprockets a year. Thats riding 2-3 times a week, every week unless I'm injured.

Erik

bclapham · Apr 5, 2005

yep, mines got a bit of galling but nothing more or less than ive seen with any other sprocket. The track i ride mostly on destroys bikes- decomposed granite- it gets watered heavily in the morning and is deep and soupy- by the end of the day its foot deep ruts that the sprockets get dragged through. I got half a season out of the the stock chain and sprockets.

Magellan · Apr 5, 2005

I have the complete set of PD sprockets (both steel) and o-ring chain).
When I checked the rear before mounting, it was flat, so maybe they have a QA problem. I have them on a TTR250 (not much power) and so far they seem to be holding up. No niticeable wear after about 20 hours of riding, much of it in lots of mud.

I've adjusted the chain once since I installed it. Note that I am very meticolous about chaing maintenance. I adjust my chain at the tightest point and with the axle, swing arm, and front sprocket all in line. I also check it after every ride. My stock set lasted four seasons.

I go steel becuase I'm not a good enough rider to benefit from the slight weight savings of aluminum (especially on the pig fo a bike I ride).

If you're unhappy, contact RM. Their service has been great and I bet they'd replace it.

Mag

bikepilot · Apr 8, 2005

My guess would be that the pb aluminum rears are made of 6061-T6 as its considerably cheeper and softer. I'v made a few for Down Hill mountain bikes and it holds up fine in that application, but is much too soft for a mx bike IMHO. Disclamer: I do NOT know for sure what they are made of, but judging by their price and poor longivity I would guess 6061-T6.

mtk · Apr 21, 2005

Jaybird said:
Exactly.
Too hard is trouble.
Without doing an ansys simulation and uploading it, you will simply have to trust that a resiliant, soft core will absorb shock load. A hard sprocket with no soft core has a harder time obsorbing shock loads, and is exactly whey they are more prone to shatter.
To be as fair to Ironman as I can, they don;t have much meat on them to begin with. They are cut nearly to what depth a case hardened steel sprocket would have the teeth hardened to to begin with. The profile of the sprocket alone may provide some flex for absorbsion.
But I'm biased against steel sprockets period.

The last sentence says it all.

The first paragraph is 100% true. But since there is no empirical evidence of a large number of Ironman sprockets shattering, it's also not relevant at all. In fact, given Ironman's warranty of thier product, I'd go so far as to say that they're pretty sure that shattering is NOT a problem. Nor is there ANY evidence to say that they are through-hardened as you claim. Lacking that, you have no data to back up your assertion, other than your admitted bias against steel sprockets in the first place.

Dekemonger · Feb 18, 2006

MTK,

Go to dirttricks website and click 4 reasons why...

Scroll down to blue box "ironman front sprockets". You will see what jaybird is saying, they are through-hardened. I understand the concept of being too hard. Think of steel bars vs. aluminum bars. Which bars absorb more energy and which bars transmit more to your arms? The same thing here except instead of your arms it is the engine internals touching the countershaft.

Jaybird · Feb 18, 2006

LOL...I can't believe I left the playground without replying on this one.

For something that points to the advantage of case hardening only the tooth profiles, concentrating on the working faces, I submit the quote below. Tsubaki is the largest chain manufacturer in the world. They have a good handle on what works and what doesn't in the way of chain drives. They are also involved in motorsports applications, so I provided their info instead of a sprocket mfg that may only concentrate on industrial applications, but their sprocket hardening practices are spot-on in line with Tsubaki's.

<font color="#0000FF">All U.S. Tsubaki sprockets are made from high quality steel. Since chain loadings are evenly distributed over all engaged sprocket teeth, tooth breakage or distortion is not normally a problem. It is seldom necessary to use special high strength material. Sprocket diameter and pitch determine the specific material used.

The hardening process of small diameter, small pitch sprockets are usually a on-step procedure: heat treatment (electrical induction). Large diameter, large pitch sprockets can usually be directly flame hardened. These methods are used to provide a high hardness at the wear areas, plus provide the ability of the tooth to absorb shock loads. This is accomplished by hardening only the wear area of each tooth while maintaining a ductile tooth core that is tough and resilient. The hubs and bores remain soft to permit reworking.</font></FONT>

http://www.ustsubaki.com/pdf/gen_catalog/gen_C72.pdf

The above PDF provides a hardness conversion chart. Compare the tensile stregths of the Ironman sprockets and you will find they are way up on the hardness scale. Way past what Tsubaki, or any other streel sprocket mfg recommends.

Ironman is selling a gimmick, and the joke is on your chain.

chevy383cid · Feb 18, 2006

Sidewinder(no.1) Sunstar(no.2) These two brands seam to take alot of abuse!! but a little pricy.

Primary Drive Aluminum Sprocket

Studboy

Thinks he can ride

KX02

Studboy

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jboomer

moabdaze

bclapham

bclapham

bedell99

Studboy

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bedell99

velosapiens

mtk

Jaybird

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Studboy

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mtk

bedell99

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bedell99

bclapham

Magellan

bikepilot

mtk

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Jaybird

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