Chain size for cafÃ? racer

Previously wrote:

Hi,

I wanted to know what the advantages or disadvantages of the two diferent size chains used on the rear of thebig twins ie 1/4 or the 3/8. I am builing a bike from scratch so I can purchase either type, looking foward to your replies.

Cheers

Andy

Some people have had clearance issues with 3/8 chains hitting the inner primary. My Dommi has a 3/8 (wouldâve been ? standard) and when I replaced it recently I couldnât find an O ring chain that was narrow enough. In the end I went for an ordinary Renolds which had the narrowest profile I could find for a 3/8. Iâm sure some will tell you Renolds ainât what they used to be but for the miles I do itâll probably last for years!

The 5/8 x 3/8 can wear a groove or hole in the back of the primary chaincase inner if you are not careful. The 5/8 x 1/4 doesn't have that problem. Quite honestly, I don't think there is much to choose between them. I switched to 5/8 x 3/8 years ago when 5/8 x 1/4 were hard to get. I generally get 6,000 miles from a Renolds chain unless I use the bike extensively in the winter when the road salt does its horrific worst.

I would agree with the above comments re clearance, some bikes seem more affected than others for some strange reason, must be down to inner chaincase positioning? One other observation, I've used both size's in the past & found that the 1/4 chain stretches much less than the 3/8, others I've spoken to have found the same & the general consensus is that the 3/8 chain is much heavier & whips more, thus stretching it, seems logical, I guess. I always use Renolds chain, as I have a local agricultural outlet that stocks both sizes in bloody great rollsfrom whichthey just cut me whatever length I require & it works out about a 1/3 of the price of buying from the usual suspects, so worth shopping around.

Regards, Tim

It seems odd that the narrower chain should stretch more as I think the rollers are the same diameter and the sideplates the same - they are the parts that would stretch. As the cross-section of steel is the same there shouldn't be any difference between them in theory. Take a section of each chain and load test it at your local Uni's engineering dept. !

Cheers, Lionel

I once used "agricultural" chain because it was cheap. Trouble is it was designed for fixed chainwheels, not ones that moved up and down on swinging arms and had variable tension, so they were like liquorice string! The giveaway was the fact they had plain steel sideplates - not blued ones. That's what I was told by John Hudson in the day anyway.

Cheers, Lionel

Lionel,

Please take the trouble to read things properly before comenting. I didn't say the narrower chain stretched more, I said it stretched LESS, as you say the parts that would stretch are the same spec, but the narrow chain has much less weight so less whip & with regard cheap agricultural chain, again, that's NOT what I said, I clearly stated the chain I buy from the 'agricultural outlet' is RENOLDS chain & it's exactly the same spec as the Renolds chain sold by motorcycle dealers, it has Renold stamped on every sideplate which are 'blued', I'll send you a link or two to inspect if you don't believe me. I usually get 6-8 thousand miles out of the 3/8 on the Commando & considerably more from the 1/4 on the Dommi, good enough for me but hey, if you want to spend 3 times more money for exactly the same thing but in a nice individual Renolds box, thats fine by me.

Regards, Tim

Chains don't "Stretch". The reason an old chain requires the rear wheel to be pulled back to tension the chain is because of wear. If a worn out chain is degreased and laid flat, it can be pulled to what appears to be a longer length and pushed to a shorter one.