middle ring suitability

[Black Sheep]

Hi,

I'm trying to find a middle ring (39t) for a friend's bike but when I look on CRC or wiggle I can't tell if the chainring is suitable for using as part of a tripple

I know it has to have ramps / pins on to aid the chain switching but can't tell from the pics.

how can I tell if a chainring will be suitable or not

tis a 5 bolt btw

 

[Crackle]

It will say middle. If it doesn't it isn't. Look on the TA website for confirmation of what you are looking for.

 

[Black Sheep]

Some of them look to be or say they're for part of a set, but don't specify middle

so anything that says middle will work with any groupset?

 

[Crackle]

Some of them look to be or say they're for part of a set, but don't specify middle

so anything that says middle will work with any groupset?

Well, I personally went for a TA chainring because I knew that would but if it's the same BCD and a ramped middle ring then yes. So if you stick with a known make you should be fine. You can get un-ramped middles but I don't think they'd say middle in that case, the middle label seems to be reserve for ramped chainrings.

 

[Black Sheep]

TA BCD?

 

[Crackle]

Oh right, sorry.

BCD is the measurement you need to get a ring that fits to your existing crank spider.
TA is a French company making chainrings - top quality stuff. Others are Stronglight, Sugino and proprietary ones like Shimano and Campag.

So you need to know the BCD first and then find a suitable ring. So for instance, Spa Cycles are listing TA rings in 39T middle. I would ring them and ask them what they've got to suit, they're very helpful and carry one of the lasrgest stocks and you talk to someone who knows their business.

 

[twentysix by twentyfive]

+1 Spa Cycles have an excellent selection of chainrings

 

[Black Sheep]

and i thought i knew about bikes!

i know its a sugino as the crank says so on it (tis for a sirrus) I presumed all 5 or 4 bolt were the same pattern.

 

[twentysix by twentyfive]

and i thought i knew about bikes!

i know its a sugino as the crank says so on it (tis for a sirrus) I presumed all 5 or 4 bolt were the same pattern.

Oh no. 5 bolt is not compatible with 4 bolt. Usually 5 bolt are roady chainsets while 4 bolt are Mtb. But you can fit either on the other. If you want low gears on your road bike an Mtb chainset can be used.

 

[Black Sheep]

oh no, i know 4 5 bolt are not compatible.

what I meant was that all 5 bolt are compatible with 5 bolt cranks and all 4 bolt chainrings compatible with all 4 bolt cranks - Like an industry standard measurement.

 

[twentysix by twentyfive]

oh no, i know 4 5 bolt are not compatible.

what I meant was that all 5 bolt are compatible with 5 bolt cranks and all 4 bolt chainrings compatible with all 4 bolt cranks - Like an industry standard measurement.

Sorry misunderstood. I see what you are driving at.

No the BCD's can be different, certainly of 5 bolt. No real experience with 4 bolt but I assume there are different BCD's there too. Measure the distance from one adjacent bolt hole to the other. Spa cycles will then translate that into BCD for you. Spa cycles publish just such a table in the CTC mag in their advert. It may be on their web site.

 

[Tynan]

campag have some la-dee-dah offset arm don't they?