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Old 04-13-05, 06:23 PM   #1
dannyg1 
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Almost Done:Tuning a 2004 Jetstream XP

Tuning a 2004 Jetstream XP

I started this project with an eye towards getting the total weight of a stock 2004 Dahon Jetstream XP down to something competitive with the lightest folders ever made. At 9.2kg, the bike began life light; now 870g lighter, it's almost as light as it can be.

Some of the highlights:

Stronglight Pulsion cranks are the current world's lightest @ 451g with all bolts, including BB mounting bolts, and the chairings included. Since I've traded the small chainring for the bashguard, I'm probably 15g up on that. The Stock Truvativ Elita crank should've weighed in at around 680g's but when I took it off, I could instantly tell it was far heavier than that. I'll try and weigh it, with all of its associated hardware tonight. If I had to just guess, I'd guess 890g's.One other thing: When I put the new freewheel on,I had a bear of a time getting a smooth drivetrain running and had almost given up on ever having it smooth again. Turns out, most unexpectedly, the CNC chainring on the Stronglight was the complete cure! Keep that in mind should you find the same action on your bike.

Shimano Dura Ace half-titanium freewheel weighs almost exactly half of what the stock SRAM did. 177g (174g measured).

Paul Motolite Brakes are not the lightest V-brakes available, but they are among the most beautifully made. 364g for the pair.

The stock SRAM7 levers were very light 195gr but, man, were they ugly.SRAM 9.0SL levers are _much better looking and a good bit lighter. 158gr weighed.

Titanium, titanium everywhere. Aluminum nuts, titanium bolts. Replacing the QR levers on the rear wheel and on the front handlebar saved 90g alone. When I finish getting the frame hinge bolt sets made, I'll have saved around 300gr just in bolts.

Other than the few titanium bits left, I'll be changing the rear derailleur (I bought a Sachs Plasma DiRT on ebay. 200g and inexpensive. When that wears out, it'll be Dura Ace 10 with SRAM rocket gripshift. Interesting thing is that that combo will only save 10g or so. Maybe I'll titanium bolt the Sach derailleur as well and tune the cage).

A lighter seatpost seems possible and definately a lighter seat (I really want a new generation Selle SLR 125g to replace the current 235g saddle I'm running now. Do have to say that this SDG i-flex saddle I'm riding now is extremely comfortable. One of the best I've ever ridden). Continental racelite slim tubes save around 40g over the stock tubes for the set, so I'm running those.

All in all, at least until I get a CNC house to work on a few things for me, I've put together a bike that's pretty impressive. I guess I'm fishing for your opinion, so tell me what you think! Here's a pic:
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Old 04-14-05, 04:07 AM   #2
Simple Simon
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Well done - Thats getting seriously light !

Would you consider ditching the rear suspension ? If so (eg replace shock with a titanium link), a bit more would be saved, other than that not much else left. I'd be interested to know the prices you got for some of these light bits (ie best bang for buck) .... most can be used on any bike.
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Old 04-14-05, 10:30 AM   #3
dannyg1 
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Simon,

I haven't given any thought to removing the rear suspension, mostly because I think it's needed. Maybe I could mount a titanium spring over some kind of rubber block, in a sort of birdy-like arrangement..It might end up being heavier. As for the prices, I ebayed almost everything and did manage to save a good bit of money. The better bargains (all prices in brackets are what they would sell for in mail order store):

Stronglight Pulsion ($459-) $355
Paul Brakes (220- shipped) $170
Titanium kit #1 - One guy was selling a bolt kit to upgrade a certain bike that was very inexpensive (90) $25
SRAM 9.0SL levers (80) $35 used (bargain of the moment on Ebay is the Avid SL ti's buy it now for $35 brand new. I needed a nylon lever though. Metal would destroy my fork on the fold)
Sachs Plasma DiRT derailleur- not in pic - (90) $26 new
Dura Ace 12-27 cassette (135) $104
Many titanium bolts (gobs) $ lighter gobs
Continental tubes- LBS - $5 each

DG1
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Old 04-14-05, 11:06 AM   #4
josr
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Hello,

First of all this is a really nice job. But here are some questions:

1. Your bike started at 9.2 kg, but according to the Dahon specs site the Jetstream is 8.9 Kg? Well they mention that 8.9 kg is without pedals (what stupid, but yeah 8.9 looks better than 9.2 with pedals), and yours with? Or is the 2005 model lighter than your model (2004?). Or are they lying?

2. Dahon is using a customized SRAM, and I am sure not without a reasson. You are using a standard Dura Ace derailleur? Is this derailleur not too low to the ground? (Question: Freewheel = cassette or Freewheel = (casette + derailleur)?)

Keep up the good work.

Jos
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Old 04-14-05, 12:59 PM   #5
dannyg1 
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J,

The 2004 is heavier than 2005 and is 9.2kg without pedals, 9.6 with. I guess that I'm continuing the confusion by using that spec. So add 400 and a few grams to my weights. MKS soon will release a titanium axle for their QR EZY series and I'll probably buy those, cutting that weight down 100g or so.I might try Speedplay frogs but I really like being able to unplug the pedals. They're always in the way when I'm walking with the bike through the endless corridors.

The derailleur you see in the pic is the standard Sram X9 medium cage (260g and a standard Sram product) and is still currently on the bike. I've just bought a bolt on replacement (Sachs Plasma DiRT 195g long cage) that'll work with the 1:1 Sram X7 ESP shifter that's stock. Hopefully this won't hit the ground!

When I get around to mounting the Dura Ace, I'll use a standard short cage and there'll be no chance of that hitting the ground as it's, maybe a touch obviously, shorter than the mid-cage X7. The weight savings to cost ratio in this upgrade is pretty lame though, so I'll probably wait until Dura Ace 11speed is the norm. I'll be needing a new shifter for this upgrade as well and it won't be any lighter, but will still cost money.

Thanks for the compliment.

DG1
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Old 04-14-05, 04:11 PM   #6
ETRTO 520
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Sounds like a serious case of bicycle anorexia ... ;-)
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Old 04-15-05, 07:17 AM   #7
James H Haury
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It seems seriously light now at 18.4 lbs.It is time to go out and embarrass some scorchers on full size bikes.
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