New Drivetrain
 

Hello everyone,

First time posting here so hopefully someone can help.

I have a Tern Verge P18 which is about 5 years old now & after maybe 10k miles the original drivetrain is on its last legs.

The front current setup is a 55/44 on the front and 11-32 on the back. The front chainrings are proving very difficult to find a replacement for in the same specification, 55/44 seemingly being a somewhat unusual setup, so I was wondering if anyone knows if there's a particular reason for having these sizes of chainring on the front. For example it seems worlds apart from the 50/34 on my regular road bike.

Obviously the folding bike is a very different beast (11.5kg, 20 inch wheels, probably a different crank length) so I guess there is a good reason to have different gears to a regular road bike, but in the absence of a direct replacement I was wondering if anyone on here has a similar bike to mine & if so what gears they have, or failing that any ideas as to what else might work if I can't have exactly the same setup as I currently have.

Hopefully I've explained this reasonably well - any help / advice / product recommendations much appreciated.

Alternative gearing
 

Measure & supply bolt circle of cranks ,,, how are they mounted? ...

An alternative Mixed hybrid, hub, Sturmey Archer combines Cassette & IGH

so like a triple crank with 1 chainring 2nd like what you have low .75 of 2nd, , high 1.33 x overdrive

small wheel has to turn more frequently per mile, than the larger wheel does .. so smaller wheel bigger chainring..



Internal gear Cranks exist too so chainring can turn at a different rate than the pedals ..

But a bigger chain ring weighs less.. (55-44 is used on smaller wheel triathlon race bikes too)








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Chuck, welcome to BFs and Folding Bike in particular.

More likely than not, your crankset utilizes chainrings which are 130BCD. Most modern road cranks (Shimano, SRAM, FSA, Cannondale, etc.) are 130BCD, with the exception of Campagnolo which are 135BCD. Yes, a compact crankset (50-34 which is on your road bike) uses 110BCD, but since your current set up is 55-44 most likely it is 130BCD. Telling us the brand name of the crankset will help nail this down.

Search ebay for 130BCD chainrings. Anything close will work. For instance I run a non-stock early 1990s Shimano 105 53-42 on my Dahon with a 12-26 9 speed cassette. I ride it primarily along coastal beach areas when I vacation, so I don't need low gearing except for head winds, and this works for me.

Think about which combo of chainring and sprockets you utilize the most. For instance, if you generally use the 55T with the middle set of sprockets, dropping to a 54T or increasing to a 56T won't make a large difference. If you primarily used the largest sprockets with the 55T dropping even to a 53 or 52 might prove helpful in taking advantage of all your gearing.

One piece of advice, if you've not already thought of this, replace your chain and cassette at the same time you replace the chainrings. Often times new pieces in the drivetrain don't play nicely with the old pieces. Also check your jockey and pulley wheels on your rear derailleur. They might need changing as well.

Best of luck on your overhaul.

PS--- Found this picture on the internet of P18, and it appears the crankset is an FSA which looks like a 130BCD to me. By any chance is this a close match?
https://cimg1.ibsrv.net/gimg/bikefor...51d1fd2b0d.jpg

Thanks for the replies & sharing of knowledge - much appreciated.

That's exactly the bike that I have, although the one store that still displays the FSA Crankset on its website (out of stock) says it's 110 rather than 130 BCD. Can you tell from looking whether the chainrings are removable from the cranks on this product as I believe this isn't always possible?

Anyway it's good to know that having slightly different gears shouldn't be an obstacle. I'll see what's out there in a similar spec & hopefully find something that works. Poor bike has been neglected recently but hopefully a new drivetrain will make a huge difference.

Chuck, you are welcome.

If you have the crankset pictured above the chainrings are held on by the five hex bolts you see pictured on the arms. That one looks to me as if it is 130BCD. Measure the distance in a straight line between the bolt centers next to each other. A 130BCD is 76.4mm. 110BCD is 64.7mm.

You are indeed correct - the words '130mm BCD' written on the chainrings should probably have served as a clue!

Anyway I think I know what I'm after now and it should be easier to get hold of than I first thought, so thanks again.