edelay

Hi folks.

Got a great deal on a Dahon Curve D3 off of Craigslist a few months back. Finally took it into my local bike shop to get the SRAM 3 speed internal hub upgraded to a 8 speed Sturmey Archer X-RF8 with a 120 mm over locknut dimension.

I upgraded from 3 speeds since I found on my 10km commute to work my cadence was always too high or too low. I guess I'm spoiled from my other bike with an 8 speed hub. The 3 speed gears were certainly fine for toodling around on a weekend on a bike path, but inefficient for commuting. As well, will be doing some touring this summer in Europe with the upgraded Dahon.

The bike shop did a great job of the installation. For less than the price of a new D3, I've got something that is better. Here are my thoughts.

PROS:
- no chain rub on the frame with the stock Dahon 46 tooth chainring and default hub 25 tooth sprocket
- the 46 tooth chain ring with the 25 tooth rear sprocket gives a nice usable range of gears
- having gear 1 with the efficient direct drive, will certainly be nice when grinding up long steep hills

CONS:
- very noisy "whizz" sound from the hub in all but gear 1 (direct drive). I have a Shimano Nexus sg 8r30 and that is silent. Hopefully this will decrease as the hub breaks in.
- noticeably less efficient (harder to pedal) than my Shimano Nexus sg 8r30. Hopefully this will decrease with age. My Nexus did for sure.
- the gear changes are much more finicky than that Shimano and more grabby
- the transition from gear 1 to gear 2 doesn't alway engage. From 3 to 2 works perfectly. I noticed that I have to completely let of pressure on the pedals or even back pedal a bit. Hopefully a tune-up and the breaking it in will fix this.

OTHER:
- the twist shifting is in the opposite direction from the Nexus. Not sure if this is a British thing, with the shifter normally being on the other side of the bike?

Winfried

It's always a good idea to let off pressure on the pedals when changing gears, or even back-pedaling a bit. I do this on my Brompton and my Alfine 11-based big bike.

I had the same idea, replacing the three-speed IGH with an eight-speed SA IGH on a Dahon D3 curve, but gave up because it's still too big when folded compared to a Brompton.

BruceMetras

I didn't care for the SA X-RF8 because of the same issues .. I know the SA's 'all up' gearing is great for small wheels, I was just spoiled by other hubs that were much quieter and less draggy.. one IGH that I love is the SRAM P5 .. of course discontinued, but they are around still if one hunts..

edelay

With my Shimano Nexus 8, I can maintain my cadence but for a split second back off on the power to do a clean shift. Perhaps I can master this will the Sturmey Archer in time or with some break-in. I hear ya, would love it if it folded as small as a Brompton. The Curve does fold small enough so it will do for now.

I'm an inevitable Brompton owner. Have had a search set up on eBay and my local Craigslist and have been waiting to pounce. I can't stand the idea of having two shifters for only 6 gears, so won't buy one new. Would prefer to get a gnarly one used and then upgrade the gears and other components into something better than I can get from the mfr directly. The only problem is Brompton owner don't sell them very often. Kicking myself for not buying the taxi yellow one last Christmas.

edelay

It is funny that the SRAM i-3 that came with the Curve was also grabby and noisy. More efficient though.

Is the SRAM p5 what is on some the older Bromptons?

BruceMetras

Doubtful unless someone retrofitted it... Bromptons usually went with the SA hubs as far as I know.. the Sachs/SRAM P5 and P7 were highly regarded in their day.. I continue to use the P5 (256%) gear range as my regular bike (belt drive Moulton TSR retrofitted with the P5) ..

tcs

FWIW, my empirical sensation is my S-A XRF8(W) turns easier than my Shimano Nexus 7.

Funny, the old French belief was IGHs were 'friction boxes' and gearing expert Frank Berto bought into that...until he tested them.

Nope. Shifters for IGHs have pretty much been set up for the right hand since the 1880s.

There's no standard for shift direction. Various twist shifters for different IGH and derailleur systems turn in either direction.

tcs

Brompton switched to SRAM (nee Sachs) IGHs for a period after the UK management drove Sturmey into the ground in 1999.

BruceMetras

We were talking 5 speed hubs .. The question was whether the SRAM/Sachs 5 speed P5 was used on early Bromptons...and I answered "Doubtful unless someone retrofitted it" .. perhaps you have an older Brompton sales brochure showing that they were sold with the P5.

Here's a period piece ..

Brompton 5-speed Upgrade | A to B Magazine

tds101 

I would have purchased a Dahon Curve and upgraded it to a Nexus 8 speed hub, but it's 135mm old doesn't fit the Curve. It would be a perfect trunk bike.

I forgot to mention that the Downtube Mini is exactly what the Dahon Curve should be.
https://www.downtube.com/Shimano-Nexu...ike-p/mini.htm

bhkyte

I passed this option over. I thought it would make more sence to buy a Curve SL used but I have neither seen one near me.

tds101 

The Downtube igh bikes are a bargain for the asking price.

Winfried

Does someone have experience with the Downtube Mini, especially compared to the Brompton?

"12/15 Starting in 2016, we will donate ALL profits to charity. Keep an eye on the website for more information"

Huh?

smallwheeler

theta healing™©

Winfried

More infos about the Downtube Mini:

> The box is 32"x23"x14" and it is smaller than the box, additionally once the seatpost is removed it is the size of a Brompton.


IOW, 81 x 58 x 35 cm as opposed to Brompton's 55 x 55 x 25 cm. So it's much bigger when folded.

Incidently, the Dahon Dash P18 is 88 x 79 x 38 cm (15.0" x 31.1" x 34.6").


> I forget the gear inches, but we use 70T/22T for the belt model with Shimano Nexus 8 I recall it gets high 20's to mid 80 gear inches.

28 gear inches * 0.08 = 2,24m
85 gear inches * 0.08 = 6,8m


FIY, the six-speed Brompton with a 50T chainring + 13/16T cassette + BWR offers a 2,34 - 7,9m development.


So it looks like the Downtube Mini would be slightly easier going up hill, but slower when riding on flat terrain.

>> Is the lug in the front Brompton-compatible, so I can just screw the Brompton baggage block?
> I have no idea what Brompton uses, hence I would assume it doesn't....but it might.


Strange that they wouldn't know. Isn't it their main competition for that bike?

smallwheeler

i would think the main competition for the downtube mini would be the dahon curve, of which, it is a copy.

edelay

I was so close to buying a Downtube Mini. I have to say that having "Bike1.com" printed on the side really turned me off. Otherwise an awesome bike.

Getting a deal on a used Curve D3 and then upgrading to 8 gears still saved me at least $200 over the Downtube Mini

tds101 

I understand. I just don't like the Sturmey-Archer hub that much. Very easy to work with, but a bit touchy at times. Still, an 8 speed Dahon Curve is excellent.

edelay

I've been watching the local Craigslist for over 2 years and only 1 Curve SL came up. Curve D3's comes up every few months. Because of this I decided to go with a D3 and upgrade it. Have to say I thought I would have needed to get a smaller front chain ring... both for chain clearance from the frame and to gear the bike down. Neither were needed.

bikebikebike

The 3 speed hobbles the Curve, but it is O/W a cush, laid back bike that is fine for short runs.
Some folks go farther, but for that I would want something more efficient.
More Swiss than Dutch roads here. The SL gearing seemed to fix that, but they are rare and the E3 has a horizontal hanger that is not RD friendly.
5 and 8 speed IGH sure seem to have poor shifting , and I wonder how much that has to do with foldie's cables being moved about more.
My 14 spd Rollie is fine but ain't on a foldie , is 135mmOLD and costs $$$
Brommie 3spdx2 is more annoying for it's BWR wide spacing, than its two handed shifting dance, but otherwise not a huge deal.
The Downtube Mini seems done right

drzdave58

I like the looks of the down tube bikes except for the lever lock they use on the frame hinge...

edelay

If the X-RF8 is adjusted properly, then it shifts accurately and cleanly.

Numerozero

At least it doesn't have a history of failing.

tds101 

I 100% despise the fold of my DownTube Mini,...it totally SUX!

drzdave58

So it turns out that I need to replace my handlebar stem due to the recall....Dahon will ship the part but I would have to pay the shipping plus installation at the bike shop...could cost me $60 -$80...should I go that way or buy one off eBay for $40 or $50..?...is there any difference in the quality?...thx