So continuing from my last post, I have a new set of cranks as you may have realised. You could guess from the chainrings that they are some kind of vintage style crank with the small bolt pattern. However they are not the famous Spécialités T.A. Pro Vis, nor are they the very similar Stronglight 49D cranks, they are from the less well known French manufacturer Nervar. From what I have gathered, Nervar cranks were found on a lot of high end French constructeur bikes as well as Schwinns and Peugeots, you can read more about Nervar here. They are the Nervar 631 cranks, which are somewhat of a rarity, which is a shame because they are beautiful cranks that take the common 50.4 BCD pattern that the Stronglight 49D and Spécialitiés T.A. take, but use the standard 22mm extractor threading.
|This is how they looked originally|
You might be wondering why I have new cranks? The Stronglight 99 cranks I had previously were great cranks with a nice gearing range and a narrow Q-Factor, as well as being very light. About a year or so ago the left hand crank came loose once so I babied it home, however a few months ago after some riding I noticed a clicking noise when pedalling. I think it came loose because when I installed it, it didn't seat properly on the taper and must have worn itself out a bit. I had no idea what this was for a while but I realised it was the crank, tightening the left hand crank a bit didn't really alleviate this. They worked fine, but the clicking was driving me nuts, and I love any excuse to buy more vintage bike parts on eBay.
|These are very light cranks|
The cranks came with a 54T chainring still attached which is of no real use to me, they look to have smaller holes for an inner ring which could be attached with spacers. The arms themselves are quite nice and chunky with a squarerish profile with a textured flute on the outside. They are definitely forged as you can tell by looking at the chainring spider, and generally have a nice feel of solidness and robustness.
The 50.4 BCD pattern differs from newer designs because it lacks a spider like modern arms, in a multi-ring setup the inner rings are all attached to the outer ring which is then attached to the crank. This has the advantage of allowing a near infinite number of combinations, single, double or triple are all possible with the same crank arms with only a swap of the bolts, spacers and chainrings which are also still quite plentiful new and used in a large range of sizes from 26t to 67t. The downside to this style of crank is probably chainring flex, due to the distance between the fixing to the crank and where the chain pulls on it. However I have never had a problem myself with the Stronglight 99's which were previously on my bike which also have a very small 86BCD.
The factory spec is a 117mm ISO BB spindle, however I used the118mm Shimano UN54 that I had previously. This gave a chainline of 45mm, a road double should be 43.5mm, and I should have used an ISO square taper instead of a JIS taper; ISO cranks on a JIS taper should sit slightly further out. However I have found that with older cranks and BB's to get the chainline perfect you need to just install it and measure. This means a 115mm JIS BB would be pretty much bang on, I did notice that the Q-factor was a bit wider when I was riding it compared to the Stronglights. The arms themselves are a fair bit beefier and felt stiffer than the Stronglights or T.A. arms, they are a bit tarnished as well and I had to chase the extractor threads as they had a little bit of damage which made it difficult to start the extractor in the thread.
Finally then, onto the polishing!