Dahon Jetstream P8 2007 - Front derailleur conversion.
 

Hi

I’ve owned a Jetstream p8 since 2008 and after 6 years of storage, I decided to recommission it.

I believe it is possible to add a front derailleur thanks to the LITEPRO front derrailleur hanger so I am now considering cranset option. I think i would go for a SRAM x7 front 2 gear derailleur kit. Looking at my bike, the original TRUVATIV kit has a 52T ring mounted on the inside of the crank (frame side) and a guard on the outside (leg side).

Would it be possible to fit one of the LITEPRO Chainrings 56T with integrated guard on the Outside of the crank and fit something like a 42or45T on the inside?
That said what ratio would you advice with the 8 gear cassette 11-32 for "all road" use?


Thanks

i guess no, because integrated chainguard will block the front derrailer

Does the Litepro chainring have ramps and pins for shifting on a multiring setup? I would guess it wouldn't if it's made for single chainring. You should get an outer chainring with ramps and pins if you want to be able to shift.

You could either put both new chainrings on the inner side of the flange with spacers to separate the 2 chainrings, or put one inside and one outside and add spacers to the outside to mount the bashguard. You'd then have to cut off one arc of the bashguard to clear the crank arm.

Does your crank use JIS square tapered BB or integrated spindle? If it's square tapered, you could use different length BB to adjust the chainline. You might want to measure your existing chainline for reference, bot at the chainring and at the cassette.

For the front derailleur on my Dahon Vigor, I use a SRAM YAW Rival FD. It's identical to the Force version. The front of the cage swings more than the rear of the cage to eliminate the need for trimming. I had to widen the cage a little bit though. However, having the rear swing less than the front does mean that you'll have a little bit more difficulty to shift to the outer chainring when on a small sized cog on the rear cassette, but if you set it up well, then it should work fine. Here is more information on how I did it.
https://www.bikeforums.net/folding-b...eat-tubes.html

I tried the Litepro P adapter for 41mm aluminum seat tube but the braze-on adapter part is shaped very poorly. The adapter from the K might fit the FD better, but the clamp on the K is 40mm for steel seat tube. I made my own braze-on adapter to attach to the Litepro clamp.

I use 12-34T 10 speed cassette with 24/44T double chainrings with 55mm (2.15") tires with an effective tire diameter of 19.80". This gives me 14.0 - 72.6 gear inches. It's a little low but I don't use the highest gear that much. The highest I might possibly go is 80-83 gear inches. I would very rarely go over 90 gear inches except for a few seconds per ride. But other people seem to want it. Your existing 11-32T cassette with 52T chainring, assuming you have an effective tire diameter of 19.30", is 31.4-91.2 gear inches.

After 7yrs, I want for a 1st ride at the weekend; 20kms including 3km of thick oozy mud, 5 km of gravel and 100m of 20" deep flood... I found that on flat-ish gravel, the current setup is fine but in the mud and uphill gravel, the rear tyre slipped as I was producing to much torque for available grip. I will need a smaller front ring.

That's a good point, looking at picture, they seem to be milled monoblock billet of Aluminium, I cannot see any feature that would ease shifting.

I thought the litepro adaptor was design to place the derailleur is the correct position. Looking at the Tuvactiv crank used elsewhere, it seems they put a ring inside and a ring outside without spacer and it works with 2 gear derailleur.



I was going for a sram x7 FD. Any reason why I shouldn't?

I believe soo.

I run 20x2" with 40 to 45psi so, I expect the effective tire diameter is a little lower than yours. Now, I do like the 52T/11T (~91 gear inches) on flat gravel/down hill gravel (it s fast bumpy and silly :) )
Mu wife helios runs the 45T with a 7G cassette 11/28T and on the road, I find it too slow or I need to put too much RPM for my liking. Off-road, it slips too. I think my top chainring has to remain in the 52 range.
Bearing in mind that I need a ring with a 130mm pcd or bcd, what would be descent as a small chainring? It seems 39T is the most common size and there may be some 38. If I was to fit a 39 ring, then, it adds 24 to 70" to the existing 31-91". I guess it could work, I believe it's not far from cyclocross.

There really isn't a correct position for the FD, as the optimal position is different for every setup due to many factors, like the largest size of your chainrings and cogs, the angle and position of your seattube in relation to the chainstay and BB shell, thickness of the seattube, the chainline, and the distance between chainrings. The litepro adapter and even the fixed braze on that comes with double crank Dahons might work optimally be designed for large chainrings, but I have small 44/24T chainrings and so the adapters and braze on wouldn't work for me.

You can try any FD and see if it works for you. I have no experience with that specific FD. I have only tried the Shimano FD-4700 and SRAM YAW. The YAW worked better than the Shimano for me, because the YAW had a narrower spring which allowed the inner cage plate to be closer inward. However, Shimano FD-4700 does not fit on the Litepro P adapter because of the strange bend that the P has, which hits the front of the FD spring. The YAW just barely fits in the P adapter, I didn't pay too much attention to it since I don't use the litepro adapter so I can't tell you whether the spring cleared it.

You can search the internet for the smallest chainring offered for 130 bcd. It seems to be 38t. Most brands will tell you not to exceed a 16T difference between double chainring. I have a 20T difference.

I had a look on the internet for x7 FD. Aren't they with a built in clamp? How do you plan to get it attached to the thicker Dahon seat tube?

Also, YAW comes with a removable screw at the tail of the cage, which makes it easier to bend if you have to widen the cage. Riveted cage is difficult to bend, unless you don't want to bend it.

from the ebay picture, the 2 speed FD hasn't got a clamp



The Screw on the tail is an advantage... I'll check ebay :P

Looking @ ebay, the yaw is rather rare here, The x7 2 speed is £15 with the shifter :)



here is a picture of the bike (before its flood bath)
https://cimg3.ibsrv.net/gimg/bikefor...68c00ab099.jpg

Those are probably direct mount type, not for braze-on, so won't be compatible with the Litepro adapter if that is what you will use to attach to the bike.

If you want to use direct mount, you can still use the Litepro clamp band, but you'll have to make your own adapter to attach the FD to the clamp.

It seems the Sram Apex (£6 to £15) would do... but, can I use a SRAM X7 2speed shifter???

I don't know. But all you need is a shifter that has enough cable pull to move it in the full range of motion. If it's the older Apex version that isn't YAW, you will probably need a shifter that has trim positions, because the ring/cog combinations that have sharp angles will cause the chain to rub on the FD cage plates. All new SRAM road FDs are YAW, and the only flatbar trigger that they currently offer is the S700/SL700 for YAW, which does not have trim. There is an old SL700 with a part number that existed from before 2010, before YAW came out, so possibly it has trim, but you have to make sure you get the old version and not the new version for any possibility of trim.
https://www.bike-components.de/en/SR...er-OEM-p70862/

Otherwise you can search the internet for information about what whether or not SRAM MTB flat bar triggers would work with a road Apex FD. You can ask in the bike mechanics forum.

So, I ordered the following:
litepro K frame (40mm) mount (£28.09)
Sram Rival 2x10 Braze on FD (£5.90)
cable housing (£2.00)
ferrules (£1.00)
Litepro chainring bolts - long ones (£5.99)
Q ring Rotor chainrings (53T and 39T)... (£20)

Now, I need to check which shifter I should go for.... hopefully. not more than £20

Is your seat tube 41mm? You might want to check this and ask if they are willing to give you the k adapter but with the 41mm clamp

I measured the frame tube @ 40.4mm OD but then, it was in the dark with a vernier caliper.


Description said: Inner diameter around 41mm

Hmmm.. maybe I was wrong. I thought I read that there was a difference of 40 or 41mm clamp between the 2 models, but it doesn't make financial sense to produce 2 different sized clamps.

Maybe the only difference is the shape of the braze on to clear the frame. Oh well.

I see what you mean now, K bracket is in anterior to the tube and P bracket is posterior to the tube.
The jetstream p8 post 2008 has a anterior crank...
My old jetstream has a posterior crank :twitchy::bang:

I'm going to look for a braze-on extension block or I could make a sliding plate. Will see when I get the bits

I prefer the forward position of the K adapter, because I feel like the P adapter is too far back. But when I was building my Dahon bike, I bought the P adapter because I thought the clamps were different diameters, and my seat tube was 41mm. If the clamps are identical, then the K would be better, but I don't know whether or not the clamp diameters are the same. You could try asking the seller. ThorUSA also sells them, I think the description on there was what confused me.

On this blog, some comments said that the clamps were different, but one person who tried both wrote that the K fit on his 41mm seat tube. You could have a look:
https://handsonbike.blogspot.com/201...-16-front.html

Hands On Bike

Left and middle are Ps, Right is K. ID seems to be the same 41mm. Will see
http://3.bp.blogspot.com/-Vm9OAw7sM8...0/DSC_1896.JPG


Looking further, it seems the old jetstream (like mine) is a bite special... it seems to be the only one with a posterior crank

Posterior
https://i.pinimg.com/originals/77/f9...3faf611bf0.jpg

Anterior
https://upload.wikimedia.org/wikiped...82009%29_3.JPG

anterior (Mu)
https://encrypted-tbn0.gstatic.com/i...gnN5gr7Ahk_A&s

anterior (speed)
http://www.togoparts.com/marketplace...2646-33689.jpg

My experience is from Brompton where I used adapters made for Dahon. For 2-speed I liked more the cheaper non-Litepro adapters that can be found on Ebay searching 'folding derailleur adapter'. They came with designations 'Sp8', 'mi.xim' etc. and run for $7 or so, S/H included. I liked them more because they were sturdier.

Yes. I can see them now, the advantage to be fit either side and if too short, a small extension would be easy to add
https://rover.ebay.com/rover/0/0/0?m...2F333368128844

i ll order one... if i need it my mine great. If Not, i ll put it on my wife Helios :P

Hm... very cheap. I would have tried this one for the cable stop if I had known about it. I used an additional Litepro clamp with my own 3D printed part for the cable stop. Although this one says for 40mm diameter tube. Maybe you could let us know what the actual diameter is when you try it.

The only problem I see with this one is that the braze-on part is not cylindrical, but flat, so you won't be able to adjust the swing the FD in the adapter, or use the SRAM chain catcher. You could adjust the swing by rotating the whole clamp though.

In my measurement the cheap clamp should fit a tube in the range 40-42mm without special provisions.

I measured the tube 40.2 -40.30
https://cimg0.ibsrv.net/gimg/bikefor...49198c0a0.jpeg

and i couldn’t wait; I fitted the chain rings

https://cimg2.ibsrv.net/gimg/bikefor...31d75f8ac.jpeg

I will do a “indoor session” to see how the big one feels.

After a couple of weeks, the mounts came and because mine is the old frame, it was not simple.
I had set the bracket upside down and make plate that keeps the cable in tension.

the derailleur was fine and the sram 2x10 shifter works well.

https://cimg9.ibsrv.net/gimg/bikefor...dc41676b1.jpeg
https://cimg0.ibsrv.net/gimg/bikefor...e8b14142b.jpeg
https://cimg3.ibsrv.net/gimg/bikefor...270b25900.jpeg
https://cimg6.ibsrv.net/gimg/bikefor...9eec5f46b.jpeg
https://cimg9.ibsrv.net/gimg/bikefor...ed15d2527.jpeg

For shifting quality you would normally want the outer derailleur cage closer to the circumference of the outer ring. Is that different with YAW? It looks well too far. (I had one at some point, but got rid of it too quickly to gain experience.) Could you by any chance post a photo showing the view of the mount and derailleur from the front perspective so that one could see how the derailleur sits on the mount?