Yesterday on the club run one of my club mates remarked that she was had been unable to use the large ring on her triple chainset, this had been the case for some years since she bought the bike. Her LBS had adjusted the front mech a couple of times but after a couple of weeks it failed to engage the large ring again.
When we stopped for coffee I looked at her bike and I consider the chainset to be too far out from the bb by a few millimetres.
I believe on this 9 sp set up the centre ring should be in line with the centre sprocket - it actually seems to align with a smaller sprocket.
I could also see what appeared to be a spacer about 5mm thick. I know that sometimes a thin spacer can help if there is a slight problem with engaging the small ring. I'm wondering if this was the spacer's original purpose - seems excessively thick if so.
I've not used external bearings so I have no knowledge of normal practice with these things.
The bike is a Scott carbon frame - not sure of age fitted with 9sp Tiagra.
Any suggestions would be welcome.
Purpose of spacer on external bearing ?
Re: Purpose of spacer on external bearing ?
I'm no expert, but the spacers are to get the chainset in the right position
see link below as an example
http://si.shimano.com/#categories/5
see link below as an example
http://si.shimano.com/#categories/5
If it aint broke, fix it til it is.
Re: Purpose of spacer on external bearing ?
I don't understand.
Is this bike kitted out as new, or has someone built it or modified it?
What is the spacer for?
Surely, you buy the kit for the frame and fit it. No spacers required because the kit fits, or if it doesn't, you've bought the wrong kit.
If you have a triple chainset, you buy the correct BB for it.
Is this bike kitted out as new, or has someone built it or modified it?
What is the spacer for?
Surely, you buy the kit for the frame and fit it. No spacers required because the kit fits, or if it doesn't, you've bought the wrong kit.
If you have a triple chainset, you buy the correct BB for it.
Mick F. Cornwall
Re: Purpose of spacer on external bearing ?
Not much to choose with external bearings......
Re: Purpose of spacer on external bearing ?
That's my point.
Triple chainset.
Standard width BB shell.
It fits.
That's how it's designed.
What's the spacer for?
Triple chainset.
Standard width BB shell.
It fits.
That's how it's designed.
What's the spacer for?
Mick F. Cornwall
Re: Purpose of spacer on external bearing ?
Mick F wrote:That's my point.
Triple chainset.
Standard width BB shell.
It fits.
That's how it's designed.
What's the spacer for?
Depends on the width of the BB shell. To get the chain rings in the right place depending on the width of the shell, Either using or omitting the spacers. One external bearing kit will fit all (in theory) and will come with spacers. Unlike SD where you have to get one with the right BB width and the right axle length.
Before we start on the old argument , I am not promoting either, just trying to help.
with regard to the OP, possibly too many / too thick spacer on the RH side.
Neil
If it aint broke, fix it til it is.
Re: Purpose of spacer on external bearing ?
The spacers can be moved to the other side if required.
I did that on mine when I fitted an MTB chainset with a road front mech'.
You can also check to see if the rear of the cranks are equal distance from the chain stays.
I did that on mine when I fitted an MTB chainset with a road front mech'.
You can also check to see if the rear of the cranks are equal distance from the chain stays.
A man can't have everything.
- Where would he put it all.?.
- Where would he put it all.?.
Re: Purpose of spacer on external bearing ?
I guess it's to make up variances in bb widths and to perfect the chainline.
Re: Purpose of spacer on external bearing ?
Mick F wrote:I don't understand.
Is this bike kitted out as new, or has someone built it or modified it?
What is the spacer for?
Surely, you buy the kit for the frame and fit it. No spacers required because the kit fits, or if it doesn't, you've bought the wrong kit.
If you have a triple chainset, you buy the correct BB for it.
This is how it should be Mick - but this was bought "off the shelf" - unfortunately most people buying bikes these days have little knowledge of bike workings and have little confidence in their abilities. I'm asking about this because I've never used external bearings so I'm not sure if assembling them with a spacer is a normal part of the process - I need to find out
.Re: Purpose of spacer on external bearing ?
Mick F wrote:That's my point.
Triple chainset.
Standard width BB shell.
It fits.
That's how it's designed.
What's the spacer for?
Spacers are for locating the axle/cranks in the bearings.
That's why I prefer the SRAM design , no hassle with spacers.
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recordacefromnew
- Posts: 334
- Joined: 21 Dec 2012, 3:17pm
Re: Purpose of spacer on external bearing ?
Sounds like a mix of issues potentially. First off a Tiagra chainset which is Road should have a 45mm chainline at the middle ring. Period.
Second I am pretty sure Shimano road outboard ht2 bb's don't come with any spacer, because road bikes have 68mm bb shells generally. Shimano mtb ht2 outboard chainset / bb's come with 3 spacers to cater for both 68mm and 73mm shells and e-type front mech, which shouldn't concern a new factory Road machine usually. Unless of course if there is a mix of road and mtb parts on the bike for whatever reason. Added into the mix is that mtb chainline is either 47.5mm or 50mm, which is why mixing road and mtb can be interesting, not to mention cable pull difference issues.
Second I am pretty sure Shimano road outboard ht2 bb's don't come with any spacer, because road bikes have 68mm bb shells generally. Shimano mtb ht2 outboard chainset / bb's come with 3 spacers to cater for both 68mm and 73mm shells and e-type front mech, which shouldn't concern a new factory Road machine usually. Unless of course if there is a mix of road and mtb parts on the bike for whatever reason. Added into the mix is that mtb chainline is either 47.5mm or 50mm, which is why mixing road and mtb can be interesting, not to mention cable pull difference issues.
Re: Purpose of spacer on external bearing ?
The OP is about external bearings.
The BB shells of bike frames have been standardised for years. Italian or English.
The kit fits.
That's how it's designed. No adjustment needed. No spacers needed.
What am I missing here?
The BB shells of bike frames have been standardised for years. Italian or English.
The kit fits.
That's how it's designed. No adjustment needed. No spacers needed.
What am I missing here?
Mick F. Cornwall
Re: Purpose of spacer on external bearing ?
Shimano road triple cranks which use HTII BB are supposed to have a 5.5 mm spacer between the bearing cup and the crank on the drive side and a tapered 3mm spacer between the cup and the crank on the non drive side. Shimano MTB triple cranks only use the 3 mm tapered spacer on the non drive side.
There also may be 2.5 mm spacers fitted between the HTII cups and the BB to accommodate the difference between 68mm and 73 mm width BB. If used its usually two on the drive side and 1 on the non drive side. Some road HTII clones may use just two 1 mm spacers (e.g. Hope).
The non alignment issue may be due to the 2.5 mm spacers being present or absent depending on the BB width. Some manipulation of the chainline for a Shimano road triple is possible by including/removing 2.5 and/or 1mm spacers as necessary. The only caveat is that there is no/minimal left right play in the axle and that the retaining tab on the non drive side can be pushed down correctly.
A common error on road triples is that the thin rubber washers that are normally fitted to the cranks for a double are fitted incorrectly for a triple. For a triple the thin rubbers washers should be fitted to the cup side of the spacers, no on the cranks. If they are already present on the cranks then they should be removed and fitted to the spacers.
There also may be 2.5 mm spacers fitted between the HTII cups and the BB to accommodate the difference between 68mm and 73 mm width BB. If used its usually two on the drive side and 1 on the non drive side. Some road HTII clones may use just two 1 mm spacers (e.g. Hope).
The non alignment issue may be due to the 2.5 mm spacers being present or absent depending on the BB width. Some manipulation of the chainline for a Shimano road triple is possible by including/removing 2.5 and/or 1mm spacers as necessary. The only caveat is that there is no/minimal left right play in the axle and that the retaining tab on the non drive side can be pushed down correctly.
A common error on road triples is that the thin rubber washers that are normally fitted to the cranks for a double are fitted incorrectly for a triple. For a triple the thin rubbers washers should be fitted to the cup side of the spacers, no on the cranks. If they are already present on the cranks then they should be removed and fitted to the spacers.
Re: Purpose of spacer on external bearing ?
Mick F wrote:The OP is about external bearings.
The BB shells of bike frames have been standardised for years. Italian or English.
The kit fits.
That's how it's designed. No adjustment needed. No spacers needed.
What am I missing here?
the BB /crankset is usually designed to also fit a 70mm BB shell or even a 73mm BB shell in some cases. So when you fit it to a 68mm shell, there have to be spacers. The spacers can space the cups out from the frame, or space the cranks away from the cups, or a mixture.
This isn't at all a bad thing; you can fine-tune the chainline.
As per the OP you can also mess it up of course....
cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
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