Dahon Mariner D7 upgrade plans
 

I have a Dahon Mariner D7, I think about 2015. It has a 7 speed Shimano Tourney derailleur. About a year after I got it I was blowing rear spokes a couple a week. The shop I bought it from replaced the rear wheel with a double rimmed model which solved that problem. Also seems to have put me in a position to easily replace the rear cassette, as there is a spacer in there and looks to be a good amount of room. I'm looking at a Tiagra 11-34 cassette with a matching derailleur and click shifter. That takes care of the back. The front is another story. I don't want to put on a front derailleur, as this bike gets ridden hard and put away wet. The larger gear on the back will give me some more climbing help, which would be nice for those days when I have to walk the bike up the hill from the train station. I want to replace the crank, BB, and chain ring. If I go to a smaller chain ring I can get a little more help going uphill. But I wouldn't mind a little more speed when I'm sprinting across midtown Manhattan to make the above mentioned train. Which would dictate a larger chain ring. I've been punching numbers into Sheldon Brown's gear calculator, and the problem is that I'm just not sure how big a difference there is from 34.2 to 34.9 t0 36.9 in terms of ride.
Any insights would be appreciated.
Anthony

It's not a lot difference there. Can you go larger?

Wait- sorry- larger what? Chain ring or cassette gear?

Cassette gear.

Please verify that the rear is a cassette and NOT a freewheel. If it is a freewheel, the cassette that you're looking at won't be compatible. You'd have get another freewheel. I put a DNP Epoch Freewheel on my 16" Origami Wasp folder, and it works perfectly. It took awhile to ship, but it was worth the wait.

It's a Shimano cassette.
I didn't see anything bigger than 34, but I'll look again.

You could go to a smaller chain ring.

You don't need bigger for speed, you need smaller. A larger chainring + smaller freewheel = SPEED,...

I think he wants lower gear inches for climbing..

The problem is that I want both. But being disinclined to add a front derailleur I recognize that I need to make a decision. I was looking at a Shimano cassette that goes down to a 9 tooth on the smallest, but the price was more than I want to stretch to. I probably want the climbing more than the speed, so maybe I just stay with the 52 on the front and with the 10 speed up to the 34 on the back might be the best it gets.

Hmmm... okay, this sent me back to looking and I found a Shimano HG500 11-42t. It's a MTB cassette, and I was planning to use a short road derailleur, but maybe I should look for a MTB derailleur and shifter to mate it.

your derrailer will be very close to the ground. very prone to ground strikes.

That's why I was looking at the short cage Tiagra, but it won't work with the 42 t cassette. Trying to sort out which derailleurs would. They don't make it easy!

short cage tiagra goes maximum at 32t.
1 by transmission is a no way in folding bike world.
you best be is dual chainrings for that amount of range you want/need

That brings me to the Shimano RD-M640-SS, Zee Shadow (https://smile.amazon.com/gp/product/...718ZUBOU&psc=1) which Shimano has going to 36t, paired with a Shimano HG81 11/36 (https://smile.amazon.com/gp/product/...718ZUBOU&psc=1)