Brompton Chainring Question
 

Hello,
I'm seriously considering a Brompton and after a lot of research I'm convinced that a Brompton fits my needs best. I'm definitely getting a six speed but have a question. The standard gearing or even the +8 will work for most of my riding. I do want to use it for touring so after checking some u-tube videos, it appears that changing the chain ring seems pretty simple. After watching a few videos, they all end without altering the chain (adding or subtracting) links. Am I right that this will need to be done or is there something about Bromptons that makes chain resizing unnecessary?
Thank you.

Bromptons have all got the chain tensioner so technically while unfolded, they work with a large chain tolerance. But a too-long chain will tend to fall off when folded. If you go down 1 chainring size, it should work as-is. Going down from 54T to 44T, that would need to get at least 2 links removed. Brompton also have an ideal chain length recommendation for each chainwheel and rear cogset. I saw that just this morning in the documentation after swapping out SWMBO's chainwheel from 54T to 44T. I am not 100% sure about the numbers, it might be 100/98/96 links for the 54T/50T/44T. That doc should be on the official B website too.

If you want to go from 50T to 54T, it might be too tight.

Jur,
I'll ask the LBS for the chart when I make the purchase.

Thank you.

My LBS took 2 links out for the 50>44T -12%. Too long a chain also impacts the fold - the chain will start to drag on the derailleur pulley. Tolerances seem pretty tight folded and unfolded, I would add/subtract links for any chainring change.

I had a 44 chainwheel and went down to 42 with no problems ..Later I went down to 39 teeth chainwheel and did not take out any links..There was no problem until the fold..If the chain was on the large cog at the back it was fine..you could move the pedals so you could position the cranks and fold it properly .However if the chain was on the small cog the chain dragged on the chain tensioner..So..took 2 links out..everything fine now..

I have no problem with a 50/34 double chainring. The chain tensioner can handle the slack when riding on the smaller ring.

However, when folding, it's better to keep the chain on the 50T chainring.

Now with the spider crank any 130 BCD.. 39 t and upward is fine.. though the Trouser guard will not be on those rings.

I went from 44T to 39T; I can't remember if I took out 1 or 2 links: