Inner Triple Ring Clearance

[buldogge]

So...I installed a Centaur century triple on my '85 Spectrum a couple days ago, and tuned it best I could with the regular FD. I'm wondering about the inner ring clearance...

The Spectrum's seat tube is 28.6mm, so I'm using the Centaur 111mm BB that was already installed.

What kind of clearance from the chain stay is acceptable? I rode maybe 15 miles with it yesterday without issue...but it was an easy flattish commute.

I haven't measured the clearance, but it is 2mm or less.

I could get a 115, or put a 1.5mm shim under the DS cup.

Thoughts???

TIA
-Mark in St. Louis

[Chance]

I haven't measured the clearance, but it is 2mm or less.


If close to 2 mm and it's shifting OK then letting it go for now and keeping an eye on it for a while makes sense to me. Because of the small diameter of the ring it won't move towards the chainstay as much as larger rings, so 2 mm seems adequate to me. On an old bike my 42T small ring was closer than that and it was never a problem.

[mistermo]

I have a Centaur triple 50/40/30 on a 111 (English) BB and haven't had a problem. I've never noticed how close the 30 ring is to the chainstay, but even at 2mm, I wouldn't think it's a problem. I don't imagine you'll be flexing it 2mm's worth.

[crownjewelwl]

put some electrical tape around the stay and grind up a hill.

if no contact, then you're ok

2mm seems like enough in the small ring. you'd have to flex the bb and/or ring a lot.

[Ralph]

I generally want the small ring on a triple as close as possible to the chain stay....assuming the FD will come in that much....it lets me use the big ring over a bigger part of rear cassette. 2 MM is plenty of clearance. I have a double with Campy crankset that works fine with about .5 MM clearance. As long as it clears, doesn't rub, you're OK.

[buldogge]

Thanx Guys... In case I'm being liberal with my clearance "measurement", what's the least you would use?

I will put some painter's tape and watch for contact as well.

TA
-Mark

[Chance]

Thanx Guys... In case I'm being liberal with my clearance "measurement", what's the least you would use?

Can't speak for others but for me 1 mm which is about 40 thousands of an inch is more than enough. As reference since sometimes it's hard to measure that's a little more than a typical spark plug gap. If the frame is very expensive carbon (don't want to scratch carbon at all) or else estremely flexible maybe a little more, but for typical modern frames with stiff bottom bracket area 1 mm would work for me.

Your tape test should tell you a lot. A miss under severe service is as good as you should need. Good luck.

[oldpotatoe]

So...I installed a Centaur century triple on my '85 Spectrum a couple days ago, and tuned it best I could with the regular FD. I'm wondering about the inner ring clearance...

The Spectrum's seat tube is 28.6mm, so I'm using the Centaur 111mm BB that was already installed.

What kind of clearance from the chain stay is acceptable? I rode maybe 15 miles with it yesterday without issue...but it was an easy flattish commute.

I haven't measured the clearance, but it is 2mm or less.

I could get a 115, or put a 1.5mm shim under the DS cup.

Thoughts???

TIA
-Mark in St. Louis

Depending on how many times it has been removed and put back on plus if the spindle was greased(bad idea)..it may be getting kinda close. 2mm isn't bad but I would do the 115mm BB if it is a concern for you..only about 2mm out on the RH side.

[buldogge]

BB was brand new when I installed the regular crankset, one time off and on with this triple.

I would probably throw a 1.5mm spacer on before going thru the trouble of getting a 115mm, unless someones sitting on a basically new one they want to swap with a 111.

TA
-Mark

Depending on how many times it has been removed and put back on plus if the spindle was greased(bad idea)..it may be getting kinda close. 2mm isn't bad but I would do the 115mm BB if it is a concern for you..only about 2mm out on the RH side.