Damaged middle chainring

[barongreenback]

I have a 2009 Specialized Sirrus Sport with 48/38/28 tooth chainrings. After an unfortunate mishap with a faulty cycle carrier on my car, I've ended up with a big scratch on the side of my year old Audi A4 but even worse, I've managed to dent the middle chainring.


I need to get up and running on the bike asap and Sugino spares seem particularly hard to get hold of. This article here: http://www.peterwhit.../chainrings.asp would suggest that a simple swap with a Shimano replacement is not as simple as it could be.


So what do I do? Can I buy a replacement middle chainring or do I need a new set of 3 or a whole new crank as well? I think I'm comfortable fitting any spare parts, but I'd rather avoid spending a fortune if I don't have to. All advice hugely appreciated!


Full spec here if this helps:


http://www.evanscycles.com/products/specialized/sirrus-sport-2009-road-bike-ec016919[/font]

 

[Gerry Attrick]

Look carefully at the chainset. It is not usually possible to change individual chainrings on those cranks as they are spot welded together rather than bolted.

I speak generically here as I do not have experience of that bike, so check carefully.

According to the specs, the bottom bracket is square taper, in which case this should be a straight swap.(Make sure you select the correct number of teeth).

Ah, I've just looked at the magnified image of your bike and it appears your rings may well be changeable. You should be able to get a new ring. You need to ensure you specify the number of teeth and the "pitch circle diameter" or pcd. That is the diameter of an imaginary circle drawn through the ring bolt holes. Take the ring to a good lbs if in doubt.

 

[barongreenback]

Thanks for the advice. I'm just about to take the rings off to have a proper look. Hoping a good LBS with plenty of stock is open on a Sunday!

 

[fixedfixer]

1) rings can be bent back into shape with an adjustable spanner - just as a temp measure to get you going again. 2) if it is like the one in your link, that one has bolt on rings. You need to find the PCD measurement and you will be able to purchase a single middle ring. Look on St John Street Cycles for explanation of how to measure PCD then view the appropriate rings.

As for the A4, it's just a bike carrier or if it's like my car - a mobile dog kennel!

 

[barongreenback]

1) rings can be bent back into shape with an adjustable spanner - just as a temp measure to get you going again. 2) if it is like the one in your link, that one has bolt on rings. You need to find the PCD measurement and you will be able to purchase a single middle ring. Look on St John Street Cycles for explanation of how to measure PCD then view the appropriate rings.

As for the A4, it's just a bike carrier or if it's like my car - a mobile dog kennel!

As I didn't notice the damage until later (having ridden 20 miles and gear changes being less than smooth), the teeth are also totally shot and I may have damaged the outer ring too

This is the offending bike rack http://www.roofbox.co.uk/scripts/rbvehsel4.php?query=AR2220

It has a twist and lock mechanism but the twist is not reliable as it turns out and the bike can bounce out.