Bicycle Mechanics - chainring size question

ive been itching to increase the gearing on my fixed gear commuter so i went to my LBS for some options. the friend of mine that works there told me i was in luck and that he got a shimano 105 crank as a freebie for me (im running some old crusty mismatched sugino cranks too that need replacement...). its a 52/48 which is a bit too high for me. ive been wanting to run 43/16 but the shop didnt have any 43t chainrings in stock. my friend gave me all the details so that i could track one down elsewhere: 5 bolt, 135mm measurement. so i go to another bike shop and they have the 43t chainring... the guy didnt seem too bright though, and im not sure if he gave me the right size... i have a bad feeling that he is wrong...

whats a quick way for me to determine that the chainring is a 135? im not sure what to measure. id like to know if its the right size before i bring it down to my buddys house to fix. i really hope that im wrong and that the guy new his stuff bc most the bike shops are closed or closing now.

i was right... that guy was a goof.

for future reference: http://www.hostelshoppe.com/tech_bolt_circle_diameter.php

Isn't 135mm what "newer" Campagnolo rings are? Standard full size road is 130mm. That is probably what your Sugino/Shimano is. Compact road(touring) and mountain bike is 110mm.

Isn't 135mm what "newer" Campagnolo rings are? Standard full size road is 130mm. That is probably what your Sugino/Shimano is. Compact road(touring) and mountain bike is 110mm.

You're right. Sugino never used 135mm. Either 144mm for old road cranks and most (all?) track cranks, or 130mm for newer road cranks.

hmm, i dont know... the cranks im running now are suginos and i believe the bcd is 110. now im not sure about the shimano 105 cranks because i dont have them and the measurement that was given to me was by someone at the other bike shop. i dont actually have the cranks on me. im going to call the shop and get the distance measured from the two bolt holes. good thing i came back and checked this thread bc i was about to order a 135..........

anyone have shimano 105 cranks handy? if so whats the bcd?


thanks!

did some searching... im going to go ahead and buy a 130

I'm 99.99% sure that Shimano 105 is 130mm bcd.

thanks for all the help on the shimano bcd. sounds like 130 is the right number. just got off the phone with another bike shop. apparently (according to the shop guy) there is no 43t chainring available for 130... i find that hard to believe but im not having the best of luck so it might just be...

does this sound right to any of you?

I shopped around on eBay for chainrings a few weeks ago, and my general impression was that in the Shimano world, double chainrings are 130mm BCD, and triples are 110/74mm BCD. Not sure how this would apply to a single, but I'd lean toward it being 130. YMMV.

thanks for all the help on the shimano bcd. sounds like 130 is the right number. just got off the phone with another bike shop. apparently (according to the shop guy) there is no 43t chainring available for 130... i find that hard to believe but im not having the best of luck so it might just be...

does this sound right to any of you?

Harris Cyclery has 43T/130mm Sugino rings for $25:

http://www.sheldonbrown.com/harris/chainrings.html#130

thanks for the link john E! hmm... that rocket ring sounds like a bargain...

Watch out for the rocket rings. I have an old shimano 600 crank set (130) and the rocket ring (also 130) didn't fit. Holes matched up but the inner ring wouldn't fit the crank. After a few beers and some quality time with my dremel it now fits. If possible take the crank into your LBS and see if they have a rocket ring in stock (mine did) to see if it fits. Good luck.

BTW....do you want to sell the 48 tooth chainring?
Drop me a line at cbdougher@yahoo.com


Cheers
Chris

Watch out for the rocket rings. I have an old shimano 600 crank set (130) and the rocket ring (also 130) didn't fit. Holes matched up but the inner ring wouldn't fit the crank. After a few beers and some quality time with my dremel it now fits. If possible take the crank into your LBS and see if they have a rocket ring in stock (mine did) to see if it fits. Good luck.

BTW....do you want to sell the 48 tooth chainring?
Drop me a line at cbdougher@yahoo.com


Cheers
Chris

thanks for the heads up chris. im wondering if id run into that problem being that im riding fixed. not sure though. once i get the cranks in my hands, ill let you know whats up with the 48. thanks for asking

thanks for the heads up chris. im wondering if id run into that problem being that im riding fixed. not sure though. once i get the cranks in my hands, ill let you know whats up with the 48. thanks for asking

email harris bike and ask...tell them what you got and what you want to do. they will give you stuff that fits. It's what they do

email harris bike and ask...tell them what you got and what you want to do. they will give you stuff that fits. It's what they do

thanks man, i checked them out. i went with a rocket ring (43) that i bought locally at a shop. i threw it on yesterday and its great! riding 43/16 is awesome compared to 40/16. when i get out of the saddle to push hard on steep hills, i actually have something to push against. with 40/16, there was no comfortable position to climb hills: slow push up the hills in the saddle or stand and push at too low of a gear.

btw, i never got that 105 crank. turns out that the threads were stripped. so i just put the rocket ring on my suginos and voila. nice thing bout the rocket rings is that they are drilled for both 130 and 110 bcd!