Bicycle Mechanics - Suspension Corrected Fork Advice... With Technical

Converting two Mountain Bikes to touring bikes as previously noted.

Here are the specs:

Trek 4300's - 2002 model
Frames Size: 21" (both bikes)
Head Angle: 71
Head Tube: 145mm
Offset/Rake: 38.1mm
Existing Fork: 435.5mm (axle to crown)
Existing Fork Travel: 63mm
Steerer: 245
Headset: 1 1/8" - Threadless

Proposed Fork:

Tange Suspension Corrected
Steerer: 260mm
New Fork: 413mm (axle to crown)
Rake: 45
Headset: 1 1/8" - Threadless

I think I'm good to go, just want to check.

I don't know whether it is any help, but I am basically doing the same thing on my Sedona DX, and also switching from threaded to threadless at the same time.

I have always adjusted my preload as tight as it would go, so I don't really think the Tange fork will get me to exactly the same as I was, but I expect it to be close enough to not be detrimental to handling or ride.

I just recently put a rigid fork on my old MTB with far less thought and calculations then you have put into this with no ill effects. However based on your calculations all looks right. Your existing fork with 63mm travel calculated with a 25% sag would make the axle to crown of your 435.5mm axle to crown fork 419.75mm. The 7mm diffrence in the rigid fork should not significantly change anything. Now the difference between the Offset/rake. In my opinion the 7 mm should not change things significantly. We need to remember all these figures will change with a suspension fork as it goes through it travel.

What you will notice is a much superior feel to your power application and handling, both on and offroad.

Shortening the fork will steepen the head tube angle, decreasing the trail
Reducing the rake will also decrease the trail.
It seems to me that these changes will make the bike steer much quicker, don't know if that's what you want. If it was me I'd go with fork with less rake, like a 38.

Al

Here is my 03 Trek 4300 with a Surly fork. Has same axle to crown as your fork. Unkown rake. It did drop the front end a bit but i notice no major side effects.


http://f10.putfile.com/thumb/7/19417183149.jpg (http://putfile.com/pic.php?pic=main/7/19417183149.jpg&s=f10)

You might want to go with a bit longer fork, ca 425 mm, the 413 mm length replaces forks with ~ 50 mm travel . See below from the Vicious cycles Website:

How to select a mountain fork to fit a particular frame:
The best way is to measure! Using a tape measure, find the distance between the top of the front portion of the race ring (where the headset mounts) and the center line of the front axle, now to choose the necessary model compare your measurement with dimension "B" on the above chart. No tape measure? These are some general, but not foolproof guidelines to help achieve the correct fit. If your bike is a 1996 model or older use the 413mm model. If your bike is a 1997 model or newer use the 425 mm model. If your bike is a 1990 or earlier you will probably be needing a Vicious Cycles short length mountain fork which is available by special order. Please be aware that some manufacturers pay no attention to industry standards in which case only a direct measurement will be accurate.
Mountain


438 mm oversize steer *available in disc version
a 1.125" steer
b 438mm (17.25") length
c 1.5" rake
true temper oversize uni-crown blades
straight blade fork

425 mm oversize steer *available in disc version
a 1.125" steer
b 425mm (16.75") length
c 1.5" rake
true temper oversize uni-crown blades
straight blade fork

413 mm oversize steer *available in disc version
a 1.125" steer
b 413mm (16.25") length
c 1.5" rake
true temper oversize uni-crown blades
straight blade fork

413 mm standard steer
a 1" steer
b 413mm (16.25") length
c 1.5" rake
true temper oversize uni-crown blades
straight blade fork

You might want to go with a bit longer fork, ca 425 mm, the 413 mm length replaces forks with ~ 50 mm travel . See below from the Vicious cycles Website:

How to select a mountain fork to fit a particular frame:
The best way is to measure! Using a tape measure, find the distance between the top of the front portion of the race ring (where the headset mounts) and the center line of the front axle, now to choose the necessary model compare your measurement with dimension "B" on the above chart. No tape measure? These are some general, but not foolproof guidelines to help achieve the correct fit. If your bike is a 1996 model or older use the 413mm model. If your bike is a 1997 model or newer use the 425 mm model. If your bike is a 1990 or earlier you will probably be needing a Vicious Cycles short length mountain fork which is available by special order. Please be aware that some manufacturers pay no attention to industry standards in which case only a direct measurement will be accurate.
Mountain


438 mm oversize steer *available in disc version
a 1.125" steer
b 438mm (17.25") length
c 1.5" rake
true temper oversize uni-crown blades
straight blade fork

425 mm oversize steer *available in disc version
a 1.125" steer
b 425mm (16.75") length
c 1.5" rake
true temper oversize uni-crown blades
straight blade fork

413 mm oversize steer *available in disc version
a 1.125" steer
b 413mm (16.25") length
c 1.5" rake
true temper oversize uni-crown blades
straight blade fork

413 mm standard steer
a 1" steer
b 413mm (16.25") length
c 1.5" rake
true temper oversize uni-crown blades
straight blade fork
+1
Vicious Cycles recommends the 425mm forks for frames designed around 63mm of travel.

Sorry for bumping such old thread but i'm in the process of converting my crappy geared hardtail to a rigid SS, SS part it done, now to lighten the bike and get rid of that RST fork

About the same as the OP, 63mm travel, 38mm rake and 438.7mm Axe to crown

So any updates? How did it go?
The 425mm rigids are quite more expensive :(

Sorry for bumping such old thread but i'm in the process of converting my crappy geared hardtail to a rigid SS, SS part it done, now to lighten the bike and get rid of that RST fork

About the same as the OP, 63mm travel, 38mm rake and 438.7mm Axe to crown

So any updates? How did it go?
The 425mm rigids are quite more expensive :(

I love the Tange fork on my Sedona DX.

No bouncing when I am out of the saddle, and the chrome moly fork absorbs buzz adequately. I love the more responsive handling as well... Over-all better stability, and nice ride.

If you want to go rigid, you should try the Tange fork. I also converted a Raleigh MT-500 for a friend with the Nashbar fork, and it works well also... although the last time I looked the Nashbar fork doesn't seem to be in stock.

For looks I prefer the Tamge's more traditional looking fork...

Converting two Mountain Bikes to touring bikes as previously noted.

Here are the specs:

Trek 4300's - 2002 model
Frames Size: 21" (both bikes)
Head Angle: 71
Head Tube: 145mm
Offset/Rake: 38.1mm
Existing Fork: 435.5mm (axle to crown)
Existing Fork Travel: 63mm
Steerer: 245
Headset: 1 1/8" - Threadless

Proposed Fork:

Tange Suspension Corrected
Steerer: 260mm
New Fork: 413mm (axle to crown)
Rake: 45
Headset: 1 1/8" - Threadless

I think I'm good to go, just want to check.


yes it works

good to go

I love the Tange fork on my Sedona DX.

No bouncing when I am out of the saddle, and the chrome moly fork absorbs buzz adequately. I love the more responsive handling as well... Over-all better stability, and nice ride.

If you want to go rigid, you should try the Tange fork. I also converted a Raleigh MT-500 for a friend with the Nashbar fork, and it works well also... although the last time I looked the Nashbar fork doesn't seem to be in stock.

For looks I prefer the Tamge's more traditional looking fork...
So it's safe to go with a cheap 413mm $45 tange, instead of shelling more money for a 425mm..
lower front/shorter means quicker steering huh?

nashbar's is mucho longer at 453mm and is in stock at $55..hmm

So it's safe to go with a cheap 413mm $45 tange, instead of shelling more money for a 425mm..
lower front/shorter means quicker steering huh?

nashbar's is mucho longer at 453mm and is in stock at $55..hmm

Pull out your ruler and look at how small 12 mm (or even 40mm) is... The difference is probably in the same range as the handling change between the lightest and heaviest preload settings on shocks that have the option.

I actually attribute the more responsive handling to the lack of sponginess from a front shock rather than the difference in length.

There is probably a difference in handling between a 413 and 425 mm fork length, but probably a lot less than the change inherent in the elimination of the pogo stick effect of a cheap front shock...

Also, the quicker steering isn't enough to feel twitchy or unstable (at least in my case) it is more evident as a better feel for the road. It still doesn't feel like a tight geometry road bike, but more like a relaxed geometry road bike... Which makes sense with the geometry of my bike in general.

So I can say that the Tange fork has worked fine for me, and will probably work well for you too.

Whatever you decide, good luck!

EDIT: The reason I used the Nashbar on the Raleigh was because the rider wanted the handlebar as high as possible, so every little bit I could add was a good thing...

I found a Salsa 425mm in stock at a local bike shop (CAD$113 with tax), bought it and installed it tonight at my coop, didn't knew it was that easy to work with threadless forks, took me about a hour :)
Waiting for my new crankset and chainring to get rid of my derailleur..

http://zubu.ca/bike/rigid_fork.jpg
Old 2.2Kg monster fork (http://zubu.ca/bike/old_fork.jpg)
Close up of the fork (http://zubu.ca/bike/close_up_salsa.jpg)

Thanks for the help and nvm for the thread jack :p