Gyro_T

I have an older Truvativ triple that I wanted to use on my granddaughter's college bike. It was given to me without a left crank arm. I found lots of left Truvativ crank arms on eBay. When I received my new left crank arm yesterday, I excitedly unwrapped it and tried to install it on the spindle. Both are ten splines, but my spindle has rounded valleys and the ones available on eBay have a squared profile. The eBay crank arm came from a parts supplier in Denver "Authorized Truvativ Dealer". I called them and they are fine taking it back, but offered no assistance in finding the correct crank arm. I am willing to make some calls to shops that carry some used parts, as long as I can communicate to them exactly what I need. I am attaching a picture of my drive side with the spindle and the non-drive side that shows the squared-off splines. Thanks for any help offered.

Showing the squared splines

My spindle with the rounded valleys. Looking for a 175mm arm for this.

TPL

Contact SRAM - Truvativ directly ....they can help you

Gyro_T

I will give that a shot. Thanks

Iride01 

Shimano always puts the crank part number on the backside of the crank arms. Usually near the hole for the pedals. Does your TruVativ have a part number on them? If so, your question wouldn't rely on someone guessing correctly.

wesmamyke

I see nothing wrong with those splines. That's how normal ISIS splines look on the crank. Truvativ does have a incompatible spline pattern called isoflow, looks different and is smaller diameter. Cranks are almost always labeled right on the crank arm, that picture shows the arm is marked ISIS drive.

The only odd ball you have to look out for is cranks listed as Truvativ Howitzer, that is a downhill bike specific thing and slightly different.

Gyro_T

There was one. 848FAG I will search for that. Thanks

Gyro_T

Hi Wesmamyke,

Just wanted to make sure you were seeing the squared off splines of the ISIS Drive arm that I got from eBay and the rounded valleys of the spindle splines of my crank. I did my best to make it fit, believe me, short of driving it on the splines with a mallet . I don't think they intended that, did they??? The diameter is right, just a mismatch of fit. I do have a large mallet.
As for the part number, that did not turn up anything, but there is the possibility that SRAM will reply with useful information. In the meantime I appreciate all responses.

70sSanO

Just a word on the crank splines. I believe you will not find a completely half round spline on an ISIS crank. There is a radius and then it flattens out. There is a very slight gap between the bottom of the round BB and the top of the crank spline.

Ironically, I just installed an ISIS crank yesterday before I saw this thread. The important part is to make sure the splines are lined up and the crank arms are at 180 degrees. I use a flashlight to make sure nothing is getting damaged.

It is also a press fit in that you need a crank puller to remove an arm. It just doesn’t slide on and bottom out.

I’ve never used a mallet. The torque on the crank bolt is 385-420 inch pounds. It never fails to cause a bit of anxiety until I get that click.

John

Iride01 

What the bottom of the valleys look like probably isn't an issue. Some mfrs might well make them rounded and some more squared off. But admittedly I'm guessing since I only had one crank that might have been ISIS, or a close copy of ISIS. I think the sides of the splines are the only thing that need to match up.

And my experience with the RaceFace Cadence crankset was that it took a lot of torque to get the arm on the splines and even more to get the crankarm fully seated. Putting the crank arm on that particular crank was nothing like the very easy forces that Shimano's HollowTech II require.

So don't think that because it doesn't easily slip on that it's not correct. But I would find out what your model, series and version of your crank is and make sure what you bought is compatible.

I didn't find anything with a quick search of the number you posted. SRAM has TruVativ and although a diligent search of SRAM's site can produce results, SRAM does not make finding tech data and installation info easy. And for older stuff next to impossible.

Which is why I like Shimano. You can get on their tech doc site and find almost everything you need for every one of their products almost back to their early days. Maybe not everything you want, but at least something can be found out about stuff no longer manufactured.

Gyro_T

REsponse from SRAM:

As you've found out, The ISIS interface (left arm you purchased) is different than the GXP interface (of your crank spindle), even though they appear similar.

The crank arm you need is our part number 11.6115.287.000. Your favorite local or online SRAM dealer should be able to source this for you.

Thanks to y'all for the help.

Gyro

Gyro_T

I discovered two different Truvativ Firex cranks on eBay. One had Powerspline and one had GXP. According to SRAM, Powerspline, GXP, and ISIS are all unique spline patterns. Good job boys. Henry Ford would just shhhh IT.