Help! Crank arm rubs front derailleur

[Simeonbl]

Hi first post here!

So I bought an 80's apollo hybrid because bicycle theft round here is pretty bad and my last bike got stolen from the garage in the flats Iived at the time. So I bought this cheap old thing.

Anyway not being very knowledgeable on things at the time so correct if my jargon's wrong. I ended up having to replace the rear and front derailleur's and the bottom bracket of which the cup is epoxied to the frame

oh and a new chain. Any parts have been cheap so far and I haven't spent much. Oh I've used all shimano tourney stuff because it's cheap and that's what the frame is supposed to have on it according to it's decals

The problem I have now is when on my largest chain ring the crank arm rubs hard against the FB. It's adjusted properly and is square with the crank set. So I'm assuming the crank set isn't clearing the frame enough what should I do?

The chain ring is really worn but actually runs quit smooth! Do i need a new crank set?

 

[swampy1970]

Sounds like the outer limit adjusting screw on the front mech needs an adjustment.

http://techdocs.shimano.com/media/techdocs/content/cycle/SI/105/FD-5500-5501/SI-59G0C-En_v1_m56577569830612176.pdf

It's a pretty generic thing. Look for step 3 and adjust the outer screw as necessary.

A minute or two and a philips screwdriver is all it takes.

 

[Simeonbl]

It's not the outer limit, it's as close to the chain as physically possible without actually touching the chain. The crank arm pushes the fd back into the inner chain ring it needs about 4mm-5mm further in to clear but obviously it won't go into gear then. Do you think the crank arms bent?

 

[swampy1970]

... and the outer edge of the FD is parrallel to the chainrings?

I think in this case a picture or two would be worth a thousand words.

 

[Scotty_Dog]

Barring a bent crank arm or maladjusted FD, it sounds like the replacement bottom bracket spindle length is too short. Are you running a triple? Do you know the current spindle length?

 

[Simeonbl]

Yep the FD is set up correctly. Spindel length ia 127mm and i've running a double 36t and 48t. I can get hold of a 130mm i need to check the measurement between the bearings though .

 

[swampy1970]

If the bottom bracket axle was too short the big issue would likely be the inner chainring grinding on the chainstay. The FD is adjustable because of factors like this and if the FD is setup such that it just clears the chainring and still catches on the crank arm then something else is up.

I take it that there's no play in the bottom bracket.

 

[Simeonbl]

Hi sorry i though maybe the spindel had something to with it but it doesn't. theres 6-7 mm between the chain ring and the crank arm. If the outer limit is set to touching the chain 0-0.5mm there's 8-9mm's between the chain ring and the fd's outer plate. so 3mm to far out on the FD but it it goes in any more I can't change gear. I think I need to get a chain set that has more room in between to fit the FD. The old FD is thinner on the outer guide plate but still has the same problem.

 

[swampy1970]

If you used to have a regular 130mm bcd chainset with 42/52 chainrings on it and you put the new FD in the same location as the old then it may be that it's installed too high. Check step 1 in the pdf that I posted below. There should be only be a millimeter or two gap between the the out cage of the FD and the top of the chainring. The inner plate is profiled to help with gear changes. If this section isn't where it's supposed to be you'll have to way overshift the FD to get it onto the big chainring.

 

[Simeonbl]

No its 86bcd with 36 and 48t the FD is set up correctly all as should be. It is definitely set up right I trying to find out what could be the cause. When I bought the bike parts had been swapped out that weren't compatible and didn't work so I've replaced them with modern day equivalents, the chain set isn't supposed to be on this bike and the left crank arm is a different brand to the right. The chain set is a stronglight 99. So it looks like I may need to get a new chain set but I can't get measurements for the distance between the chain ring and the crank arm.

 

[Simeonbl]

Think I found my answer "Mech rubs crank – 1997.07 My front changer either rubs the chain or knocks on the crank when I am in top gear. There does not seem to be a position when there is no noise, which is irritating. The set up is a Campagnolo changer and Stronglight 80 chainset. Is it just a bad combination — this didn’t use to happen with my old Suntour changer — or is there anything I can do? Simon Rose – Hampton, Worcs I’ll assume you’ve adjusted the front mech cage height (to clear outer chainring by 1 or 2mm) and angle (parallel with chainrings) and declare that this problem commonly occurs when new designs of front mech are used with old designs of chainset. Front mechs now have wider cages, so they don’t need to be moved a bit to stop the chain rubbing when you shift at the rear — hence front shifts can be indexed too. And whereas chainsets used to be as narrow as possible — to minimise pedal track (Q-factor) which improves the bio-mechanics of pedalling and reduces frame flex — modern designs have been widened to suit the wider cage. Such is progress. So your solution is either a modern, wide-spaced chainset or an old (second-hand nowadays) front mech, or to take a hammer and pliers etc. to the new one — so as to make its cage a bit slimmer! Chris Juden" from http://www.ctc.org.uk

 

[Simeonbl]

Any Ideas on a replacement chainset? I was thinking a shimano one seeing as the rest of my transmission is shimano.

 

[Simeonbl]

Anyone know of a compatible sis index chainset for road bikes around the same price as the tourney stuff. So Far this is all I can find my FD goes to 48t http://cgi.ebay.co.uk/SHIMANO-FCM151-BIKE-CYCLE-TRIPLE-CHAINSET-28-38-48-X170-/130492526907?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item1e61f5f13b#ht_1880wt_1139

 

[alfeng]

Originally Posted by Simeonbl .

So I bought an 80's apollo hybrid because bicycle theft round here is pretty bad and my last bike got stolen from the garage in the flats Iived at the time. So I bought this cheap old thing.

Anyway not being very knowledgeable on things at the time so correct if my jargon's wrong. I ended up having to replace the rear and front derailleur's and the bottom bracket of which the cup is epoxied to the frame

oh and [COLOR= #ff0000]a new chain[/COLOR]. Any parts have been cheap so far and I haven't spent much. Oh I've used all shimano tourney stuff because it's cheap and that's what the frame is supposed to have on it according to it's decals

The problem I have now is when on my largest chain ring the crank arm rubs hard against the FB. It's adjusted properly and is square with the crank set. So I'm assuming the crank set isn't clearing the frame enough what should I do?

The chain ring is really worn but actually runs quit smooth! Do i need a new crank set?

FYI. If the bike dates to the 80s, then it is probably was classified as "Touring" bike ([COLOR= #808080]basically, in the 80s, when cantilever brakes replaced what are now considered to be "long" reach brakes then the bikes were relabeled as "Touring" bikes AND bike frames which used the previously-considered-to-be-"short"-reach brake calipers which were formerly only found on "Racing" bikes became the norm on the non-Touring bikes ... concurrently, 700c wheels replaced 27" wheels[/COLOR]) ... so-called Touring bikes devolved into Hybrids ...

You can replace the crankset with almost ANY crankset ...

YOU will want to MEASURE the distance across the chainstays where the pedal crosses the chainstays ... ideally, the distance is about 110mm because that will allow you to use any crankset -- Double or Triple. If the distance is closer to 120mm, then you will need to use a MTB crankset (the arms have more chainstay clearance) OR you can use a ROAD crankset which has a Triple BB (i.e., longer spindle) available ...

• for example, if the distance across the stays is more than ~115mm and if you wanted to use a 105 Octalink Double crankset, you would use the particular crankset it with a 118mm Octalink BB which is normally spec'd for Triples.

[COLOR= #ff0000]BTW[/COLOR]. I suspect the problem MAY be that you are possibly using a 7-speed front derailleur with a chain which is too narrow ... e.g., an 8-speed or 9-speed chain ... because, if you use a chain which is too narrow, then the cage has to swing further to move the chain onto the next chainring and THAT could (but may not) leave the outer plate hanging-in-the-wind where the crank arm will scrape against it.

MY GENERAL RULE: Match the chain to the Cassette/Freewheel ... then, [COLOR= #ff0000]match the front derailleur to the chain[/COLOR] ... OR, vice versa. That is, while you can use a narrower chain than a Cassette/Freewheel needs ([COLOR= #808080]e.g., 9-speed chain with an 8-speed cassette[/COLOR]), you will typically need to use a front derailleur whose plates are correspondlingly narrower unless you are using either Friction shifters or Campagnolo ERGO shifters.

That's a long way of saying that you may simply want to buy a different chain ...

FWIW. MY personal preference is to use 9-speed Shimano chains with 9-speed Ultegra front derailleurs.

 

[alfeng]

Originally Posted by Simeonbl .

Anyone know of a compatible sis index chainset for road bikes around the same price as the tourney stuff. So Far this is all I can find my FD goes to 48t http://cgi.ebay.co.uk/SHIMANO-FCM151-BIKE-CYCLE-TRIPLE-CHAINSET-28-38-48-X170-/130492526907?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item1e61f5f13b#ht_1880wt_1139

Whether or not you actually need a new crankset, you probably want to spend a little more (e.g., £20+) to buy a slightly better crankset ...

I reckon that the one you have indicated could weigh close to 2 kilograms ... 2x the weight of a "good" (but, not great) crankset ... really. Well, maybe not.

• The problem isn't that it has steel chainrings, but I would guess that the rings are riveted together and they are not replaceable ... of course, that's not necessarily a bad thing.

Regardless, I don't know why Shimano specs their MTB front derailleurs so conservatively with regard to the largest chainring they can handle ... they can easily handle a 52t chainring ... I think that a 53t shouldn't be a problem, too ... so, you don't have to limit your choice to a MTB-type crankset.

BTW. The crank whose link you posted probably uses a 113mm-or-118mm (asymmetrical) Shimano BB, or equivalent, and your 127mm long spindle will probably be considered to be too long for a reasonable installation.

FWIW. If the distance across your chainstays is 110mm, then consider something like these two cranksets (just a couple of examples):

http://cgi.ebay.co.uk/Shimano-Ultegra-6600-crankset-and-bottom-bracket-/330544275257?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item4cf5f95f39

AND/OR, the distance across your chainstays is greater than 110mm:

http://cgi.ebay.co.uk/Shimano-FC-2303-Crankset-Hardly-used-52-42-30-/330543705702?pt=UK_sportsleisure_cycling_bikeparts_SR&hash=item4cf5f0ae66

The latter probably uses a 118mm square taper Shimano BB ....

The Ultegra crankset is MANY times nicer than the one you indicated ... and the FC-2303 crankset is at least twice as nice.

IMO, the former (Ultegra) crankset is certainly worth £40+, used (the BB is included), and the latter is worth more than £20, used (again, you may need to buy a new BB).