Chain Ring Sizing?
 

I want to order a Blackspire stainless steel 24-tooth 5-ring 74BCD inner to replace the 30t inner oem on a 105 triple crank.

The best price is from chainreactioncycle and I will get free shipping so I want to order from them.

My problem is shown here:
http://www.chainreactioncycles.com/M...px?ModelID=495

They don't list the bcd for the 5-bolt 24-tooth ring.

As far as I can determine, if it is a 24-tooth 5-bolt ring, it MUST be 74 bcd. But I don't want to take a chance on ordering it if it is possibly the wrong bcd.

Contacting their customer service to ask this question is out of the question--they just don't ever answer.

So my question: Are 5-bolt 24-tooth chainrings sold today with any bcd other than 74mm?
Thank you.

This site:
http://www.universalcycles.com/shopp...ils.php?id=304
appears to show 24T, 5 bolt Blackspire rings in 58mm BCD. I'd email the company and ask.

This shows them to be either 58 or 64 BCD:
http://www.cambriabike.com/shopexd.asp?id=95956

Unless it explicitly states 74mm BCD, I'd stay away. Personally, I'd stay away from any site that doesn't state BCD, period. Omitting vital technical information is flat-out silly.

Do you have any LBS's within reasonable distance? I'd try to buy it locally if at all possible so you are certain you will get the right tooth count and bcd. I wouldn't go out of my way to get a stainless steel chainring as granny rings on road bikes should last forever even in aluminum.

Blackspire is definitely MTB oriented. "CD" must be short for a couple of buzzwords that might point to a standard.

Anyways, Harris has some of what you want.

This is an out-of-character screw-up for chainreaction--they usually give a lot of good info. The other day I tried to order the Pletscher two-leg kickstand from Jenson:
http://www.jensonusa.com/store/produ...Kickstand.aspx
http://bikeforums.net/attachment.php...hmentid=152175
I understand from reading that it comes in 2 different models (one length for 26" and the other for 700c). Since Jenson doesn't say which one they have, I sent an email inquiring. This is the useful reply I got:

"Im pretty sure that it is for the 26 but im not 100%. We dont have the specs so i really couldnt tell you. Sorry for the inconvenience and please let me know if you have anymore questions.

Shadd Stephen
Customer Service
Jenson USA"

Naturally to save on shipping I have to combine and buy from one vendor. Doesn't Shadd's "help" really give you confidence in Jenson . . . I wonder if Shadd will pay the shipping charges if it doesn't fit . . .

I've already purchased and am using Sugino 24t aluminum rings. I just feel like it's a weak link; but I'm about ready to live with it--maybe I can find another weak link:D

I wouldn't worry about running aluminum unless this is for cyclocross usage on muddy courses with long uphill grinds.

Weak link? Don't be silly. Aluminum granny rings will last for decades in your use. Find something else to worry about.

Well, cyclocross bikes almost all use double cranks with 48/36 rings most typical. Wearing out an aluminum granny ring isn't an issue since they don't have one.

That's true. As well as the scarcity of CX courses having long grinds on 'em. Both rare as hen's teeth, IME. But, who knows what they got going on in HI.

OK, I'm convinced--Thanks, Guys!