Can't solve this one.

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bigjim
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Can't solve this one.

Postby bigjim » 10 Sep 2020, 6:18pm

I have a very nice Woodrup bike. I can't work out if it is 70s or early 80s as it has had a respray in it's past by Bob Jackson. However. I've installed a modern 50/34 chainsetFSA compact on the front whilst retaining the freewheel on the rear hub. It has a modern 7 speed Megarange freewheel fitted. Sora 8 speed STIs up front. Whist in the 34 on the front and the higher gears on the back the chain rubs on the wall of the big ring. Slightly catching it at times. I assume it is the chain-line but can't figure out how to cure it. Anybody got any suggestions apart from cold setting the frame for a modern wheel?
Cheers Jim.

chris_suffolk
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Re: Can't solve this one.

Postby chris_suffolk » 10 Sep 2020, 6:31pm

By 'modern compact' I assume you mean external BB (hollowtech). Any space for shims on the drive side crank axle? Will push the front cogs out a touch and improve the chainline.

ElCani
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Re: Can't solve this one.

Postby ElCani » 10 Sep 2020, 6:31pm

What style of bottom bracket does the chainset use? If it's square taper, then a BB with a longer axle will move the rings out a bit and cure/lessen the issue. If it's an external BB then you can get spacers to go between the frame and the external cup (moving it and the chainset outwards) but whether that's ultimately workable depends on the specific chainset.

Brucey
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Re: Can't solve this one.

Postby Brucey » 10 Sep 2020, 6:41pm

34-50 chainsets are mostly designed to run using 9 or 10/11s chains, which are narrower than 6/7/8s ones. If you are using the latter with one such then rubbing on the big ring as you describe is quite likely. You can use shim washers to respace the chainrings slightly wider and avoid the issue (SJS sell them, so do others). Alternatively a narrower chain (which is meant of the chainset) may work with the freewheel; it all depends on the thickness of the sprockets.

NB the indexing won't quite be perfect with a 7s freewheel and 8s shifters; it'll probably be workable though.

FWIW I am working on schemes for respacing modern freewheels so that you can use closer-pitched sprockets and modern chain, even though the back end of the frame is only 120mm or 126mm

cheers
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The utility cyclist
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Re: Can't solve this one.

Postby The utility cyclist » 10 Sep 2020, 8:38pm

Brucey wrote:34-50 chainsets are mostly designed to run using 9 or 10/11s chains, which are narrower than 6/7/8s ones. If you are using the latter with one such then rubbing on the big ring as you describe is quite likely. You can use shim washers to respace the chainrings slightly wider and avoid the issue (SJS sell them, so do others). Alternatively a narrower chain (which is meant of the chainset) may work with the freewheel; it all depends on the thickness of the sprockets.

NB the indexing won't quite be perfect with a 7s freewheel and 8s shifters; it'll probably be workable though.

FWIW I am working on schemes for respacing modern freewheels so that you can use closer-pitched sprockets and modern chain, even though the back end of the frame is only 120mm or 126mm

cheers

You forget that the 'compact' c/set was around long before 9 speed, having used both older and newer variants and the latter with older chains and newer 9/10/11 speed chains and again on both rtro and modern machines, I've never experienced the scraping you mention.
There's absolutely no need to shim the chainrings.

Brucey
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Re: Can't solve this one.

Postby Brucey » 10 Sep 2020, 8:44pm

I'm forgetting nothing; those 'compacts' (which weren't even called that) are spaced differently and a have a different issue; they won't work well with narrow modern chains, 'riding' on the small chainring is likely if you try.

The OP's FSA compact double is extremely unlikely to work properly with 7s chain for the reason I have described.
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Valbrona
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Re: Can't solve this one.

Postby Valbrona » 10 Sep 2020, 9:12pm

That a bike bearing components spanning four decades and a mix of 7 speed and 10 speed kit ain't going to work.
I should coco.

bgnukem
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Re: Can't solve this one.

Postby bgnukem » 11 Sep 2020, 1:16pm

If the bottom bracket RH cup can't be spaced out from the frame using shims, I assume it's not possible to move the cassette closer to the spokes because of the older narrow freehub body?

You could perhaps try a 9-speed chain, if it would work with the 7-speed rear cassette sprockets (which may be too thick).

Otherwise can you just live with using some of the sprockets with the small chainring? I tend to get rub using the smallest 2-3 sprockets with the middle 'ring (I use a triple chainset) and so just use the sprockets at the lower (i.e. larger) end of the cassette, and the top/smallest 4-5 sprockets with the big 'ring. If the gearing is too high to allow this, maybe use a smaller large chainring or a 12-up or 13-up cassette.

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foxyrider
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Re: Can't solve this one.

Postby foxyrider » 11 Sep 2020, 5:05pm

Using a 9/10 speed chain on the 7sp should work ok - i found that the only modern chain that runs smoothly on my 2x6 Eroica bike is a 10sp - i tried every thing from 5/6sp upwards before reaching this conclusion and losing the constant growling.
Convention? what's that then?
Airnimal Chameleon touring, Orbit Pro hack, Orbit Photon audax, Focus Mares AX tour, Peugeot Carbon sportive, Owen Blower vintage race - all running Tulio's finest!

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bigjim
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Re: Can't solve this one.

Postby bigjim » 11 Sep 2020, 5:10pm

Valbrona wrote:That a bike bearing components spanning four decades and a mix of 7 speed and 10 speed kit ain't going to work.

I'm afraid you are quite wrong. Firstly it is not 10 speed kit. It's a 9 speed crankset on a square taper. Square taper is still sold on modern bikes. I have used this setup on an 80s Raleigh Sprint. 2 80s Harry Halls and a 90s Raleigh Clubman. Steel frames lend themselves very well to modern components and ride very well. It sometimes just needs a little fettling. Something modern bikes don't lend themselves to quite as easily.

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bigjim
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Re: Can't solve this one.

Postby bigjim » 11 Sep 2020, 5:16pm

Thank-you for all the comments and advice. Much appreciated. A few things to work through. I've also thought that maybe its possible to draw a line where the chain side-plates are making contact on going over that area with a file. Not enough to weaken, but enough to allow the slight clearance needed.
Brucey. I've found in the past that the 8 speed Sora works very well with a 7 speed freewheel, and you don't notice the extra click. 7 speed Sora are quite rare now. I'm very much a DT guy but this bike is already set up this way.

Brucey
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Re: Can't solve this one.

Postby Brucey » 11 Sep 2020, 6:10pm

0.45mm thickness chainring bolt spacers

https://www.spacycles.co.uk/m8b0s173p3305/SPA-CYCLES-Chainring-Spacers-small-%28x5%29

worth a punt for a quid?

BTW you don't say what exact model chain you are using, or chainset model (from the description I'm guessing FSA tempo...?) or what chainrings are fitted -standard or aftermarket?

One thing that is worth checking is that the inside chainring is fitted the right way round; with some models of chainset it is possible to fit the chainring the wrong way round; there is no counterbore for the bolt heads and the teeth are offset laterally.

cheers
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Brucey
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Re: Can't solve this one.

Postby Brucey » 11 Sep 2020, 8:27pm

I just checked an FSA tempo double crankset I have here and the inner ring is steel, without counterbores. so it is of the sort that is easily fitted the wrong way round. The inner ring has a slight offset built in to it; this offset should be positioned so that the teeth are set to the left; rubbing of the sort reported is inevitable with many chains if this is otherwise. I suppose you could fit the chainring the other way round (eg for wear reasons) provided you use suitable length spacers.

I'd check that first of all

cheers
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