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Dimensions for 1995 Trek 520 Fork?

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Dimensions for 1995 Trek 520 Fork?

Old 05-23-10, 07:43 PM
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dnlpnd
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Dimensions for 1995 Trek 520 Fork?

I am determined to replace the original threaded fork (1" headtube) with an equivalent 1" threadless fork with canti-brake brazeons and lugs for lowrider panniers. I've contacted Trek directly and they were useless for obtaining dimensions on the original fork. Before I can fork shop, I understand that I need the axle-to-crown race distance and rake. These dimensions are not easy for the do-it-yourselfer to measure with any accuracy. Therefore, I am hoping someone here may have already measured a fork from a 1995 Trek 520 and could pass those dimensions on to me. Thanks!
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Old 05-23-10, 08:44 PM
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The 520 has been in Trek's line since the stone age with very little change. The current frame has a sloping top tube instead of a level one but I believe all the other geometric considerations are very close to the same so the fork crown-axle and rake dimensions are probably the same as the current bike.

BTW, here is a .pdf of the 1995 Trek catalog covering the steel frame bikes from that year, including the 520. Scroll down to the bottom of page 7 for a chart of the 520's geometry and compare it to the 2010 catalog info. They are very similar. Note, for example, the rake dimension is identical at 5.2 cm for both the 1995 and 2010 bikes.

https://www.vintage-trek.com/images/trek/95/Trek95.pdf
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Old 05-26-10, 03:26 PM
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Your Best Estimate?

HillRider, thanks for the link on the 1995 Trek 520. Going with your train of thought, my 1995 Trek is a 21", what would be your best estimate of the fork crown-axle and rake dimensions from a modern Trek catalog as close as you can find to my year and size? Thanks again for your time!
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Old 05-26-10, 04:57 PM
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You no doubt want to stick with a 700 wheel, but if you didn't you could put a trek threaded fork from a 800,820,830,850,930,950 MTB style bike and get the canti brake bosses, and lower eyelets, these take 26" wheels.

You could also get a threaded trek fork from a 700,720,730,750 multitrack with canti bosses.These take 700c wheels. They also have lower eyelets. I see these forks on ebay. Trek Cromo forks.
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Old 05-26-10, 05:10 PM
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The problem I see is that there is a big difference in the head tube angle between your 520 and the HTA of modern bikes that modern forks are built for that I'm aware of. If you are trying to keep the handling characteristics about the same with a new fork then you need to keep the steering trail about the same. Trail is a function of head tube angle and rake offset. A change in the length of a fork will effectively change the HTA. The HTA for your bike is 71 degrees according the the chart. Most road bikes these days have HTA's around 73 to 74. Modern Treks are some of the steeper HTA's. If I'm reading the chart correctly your fork has a 52 mm rake offset and a trail of 63 mm. The relatively high rake offset is to help offset the layed back HTA to result in a very reasonable 63 mm of trail (more than Trek's modern "racing" geometry).
What I'm getting at is that typical modern replacement forks are designed to work with steeper head tube angles. But it may be possible to find the correct length and rake offset. I don't know. It is the 63 mm of steering trail that you should try to duplicate or at least get close. Assuming an identical length A rake offset of 50 mm would increase the trail and might make the bike turn a little slower, not necessarily a bad thing.
Here is a site with some useful information including the formula for calculating trail: https://www.bookrags.com/wiki/Bicycle...cycle_geometry
The handy calculator that I use to use is no longer available.

Last edited by Al1943; 06-01-10 at 09:18 PM.
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Old 05-27-10, 08:29 PM
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Al1943's explanation of rake/trail is very good. Along with finding a fork with a suitable rake, you are going to have problems finding a new fork with a 1" steerer.

The closest I could find is a Surly Cross Check fork which has a rake of 44mm and a crown to axle length of 400 mm which is probably a bit longer than your Trek fork. It is available with a 1" threadless steerer and has canti bosses.

https://surlybikes.com/parts/cross-check_fork/

Otherwise a fully custom fork may be the only alternative.
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Old 05-28-10, 09:16 AM
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If If you can find one you may want to check one of the early 2kX 520's. There were a couple years of those that ran 1" threadless.
There's also a Tange cross/touring fork which is available in 1" threadless you may want to check out. Of note - I'm fairly sure it only has eyelets on one side unlike the Trek fork which would have both. This could be significant if your rack wants both.
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Old 05-28-10, 11:35 AM
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Originally Posted by tromper View Post
... I'm fairly sure it only has eyelets on one side unlike the Trek fork which would have both. This could be significant if your rack wants both.
The Surly fork has dropout eyelets but no upper braze-on rack mounts either. That's why hardware stores sell P-clamps.
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Old 05-30-10, 08:39 AM
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Conclusions???

All great information! Here are some of the conclusions I have come to: 1.) The closest off-the-shelf fork I can find is a Dimension fork (available at ebikestop.com for under $40), the only catch is that I would have to forego the pannier lugs. It has a rake of 50mm versus the 52mm rake of the original fork. Not knowing the original axle to crown length, I'm not sure how the lengths compare (for trailing purposes). 2.) Waterford will build me an exact replica of my Trek 520 fork for $350. Independent Fabricators will build me an exact replica of my Trek 520 fork for $390. 3.) I can buy a Surley Long Haul Trucker frame and uncut 1-1/8" threadless fork (touring geometry) for $400 and virtually all my already upgraded Trek 520 parts would transfer to the new frame. 4.) Lastly, putting a 1" threadless fork on my Trek 520 feels a bit like throwing good money after bad, because I am noticing that the selection of 1" threadless road stems is almost non-existent. I wanted a short extension 1" stem that has the correct clamp diameter for my road bars (bmx stuff will not work).
My hesitation with building up a Surley LHT are the potential problems I'd have to deal with chainline issues and bottom bracket offset (when my Trek 520 is shifting perfectly with a 8-sp STI 11-32 cassette and Ultegra triple crankset). Then when all is said and done, will I like how the bike rides & handles? Also, two local bike mechanics have suggested that a 21" Trek 520 might be too small for my 5'11" height and 32" inseam. I'm thinking I may like the LHT better, since my Trek 520 has never been overly stable on the steering, and I've always hated the height and extension options of the stem (maybe because the bike has never fit correctly, but I'm not ready to jump on that bandwagon yet). The smallest Surely LHT with 700C wheels is 56cm, which by default would force me into the next size larger frame (which also may cause issues with me not being able to stand over the top tube flat footed). Then I read that even though the LHTs are loved by their owners, the paint quality on Surley is poor (chips easily). Which is troubling, because this may be the last road bike I ever purchase/build. As always, any opinions and advice would be greatly appreciated. Thanks!

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Old 05-30-10, 09:55 AM
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A note on fork replacement:

All of the frks you linked to will work. The handling might change if you go from 52 to 50 mm of rake, but that will make the bike more stable. It is also possible that the axle-to-crown measurements on the aftermarket forks are different, but probaby not to the point where it will alter things much at all. It is very unlikely you will notice the difference after the first few minutes of riding.

You can get a reasonably accurate axle-to-crown measurement with a tape measure then compare that to published specs on avaialble forks... again - a few mm longer or shorter is not going to change enough to make any real difference at all. You might notice it feels slightly different when you first get on it, but the head-tube-angle change resulting froma 5mm difference in fork length will be less noticable than having an underinflated tire, or an extra water bottle in your handlebar bag.

A note on selecting a new frame or bike:

The fit is the most important aspect of selecting a new bike. IF it is heavier or stiffer or not enough rack mounts or has bad paint is all unimportant if the fit is wrong, and a far crappier bike will perform better if the fit is better. It sounds like you have no starting point by which to judge what dimensional difference you want in your next bike... you need to find a bike shop that specializes in fitting, pay them to measure you up and provide a reccomendation as to what size and length of bike you should be considering. I agree that a 21" (52cm) is probably the totally wrong size for someone 5'11 - you should probably be on a ~56 - 60 cm instead, which will give you higher handlebars and a much more comfortable layout.

Before you buy a new frame please consider all you will need to adapt your parts to the new frame. Stem and headset type and size, rear axle length (Over Locknut Distance - OLD) are all considerations that might have you replacing parts that will rack up the price for your project until it nears the cost of a whole new bike.

There are a bunch of production touring bikes still on the market. Surly, Kona, Cannondale, Jamis, Salsa, Rocky Mountain, Trek, and many others offer touring models in all sizes that will have you riding faster, longer, and more comfortably than before.
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Old 05-30-10, 10:24 AM
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A few comments:

I just built up a Surly Cross Check so I can give you some first hand info on Surly in general. I guess the paint isn't Imron or under several layers of clearcoat but it's adequate and mine hasn't shown any tendency to chip yet. I did treat all of the tube and fork blade interiors with Frame saver but I do that with any steel frame and fork.

My frame built up very nicely and the chainline, with a 130 mm rear hub and 8-speed Shimano mixed-bag stuff, is fine and it shifts very well. BTW. the Cross Check has 132.5 mm horizontal dropouts so it will accept 130 or 135 mm hubs. The LHT is 135 mm only.

Unless you have very short legs for your height, a 56 cm frame with 700c wheels should be no problem for standover. I'm 5' 9" and my Cross Check is a 56 cm with 700c wheels and 700x32 tires and the standover clearance is plenty.

My Cross Check is heavy (~33 pounds all-up which includes a rack, fenders, rack trunk, water bottle, cyclometer and a tail light) but it handles securely and is responsive enough without being too eager. It's stable to at least 43 mph which is the fastest my local hill has gotten us up to. The only touring amenity it lacks is mid-blade fork rack mounts and P-clamps would solve that problem quickly. I would tour on it with no hesitation.

Summary: Either the Cross check or LHT would make a newer, more integrate package than trying to retro-fit your older 520 and the cost would be similar.
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Old 06-01-10, 08:53 PM
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Thanks everyone for being on this journey with me. It has become very evident that it makes no sense to spend hundreds of dollars doing a fork swap to get a longer 1” (already becoming obsolete) threadless steertube for a bike that probably has never fit me correctly to begin with.

LarDasse74 makes a good point; I really do not have starting point by which to judge the size needed in my next frameset. Though I’ve thought about shelling out the money to be professionally sized up, but I know that I’ll pay a premium to get measured by a shop and then buy somewhere else (because no LBS can/will touch on-line prices). With the Surley LHT being the only affordable touring frameset sold to the public (please correct me if you feel that I am wrong in this conclusion), I am not sure cost to benefit analysis of fitting makes sense at this stage in the game. Considering how much standover height clearance I have on my 21" 520, the 56cm is the largest Surley LHT that I dare try. The standover height difference between the 21” 520 and 56cm LHT is 1.8” which is really pushing it for me to be able to stand flatfooted over the top tube.

In building up a new 56cm LHT with all of my current components (many of which are within a year or two old), here are my findings:

LHT 520
Seat Tube Length 55.9 53.3
Top Tube Length 56.4 56.5
Head Tube Angle 72.0 71.0
Seat Tube Angle 73.0 73.5
Chainstay Length 46.0 45.0
Wheelbase 105.7 105.4
Standover Height 81.3 76.8
Fork Rake 4.6 5.2
Seatpost Diameter 2.7 2.5
Seatube Diameter 2.9 3.2
Stem Diameter 2.9 2.8
Rear Dropout 1.35 1.35
Bottom Bracket Shell Width 6.8 ?

I’m getting weird measurement differences on the front derailleur clamp/seatube diameter and seatpost diameter with my calipers. I’m not sure if my existing seatube and front derailleur will work on the LHT. Does anything here jump out at anyone with frame geometry experience as far as anything that might make me an unhappy with the 56cm LHT frameset? Thanks!
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Old 06-02-10, 07:21 AM
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Originally Posted by dnlpnd View Post
Though I’ve thought about shelling out the money to be professionally sized up, but I know that I’ll pay a premium to get measured by a shop and then buy somewhere else (because no LBS can/will touch on-line prices).
You will pay for the service... but the price is generally told before hand. Many shops will chage $60 - $100 for a basic fitting session, and waive this if you are buying a bike from them, or refund the fitting service price at the time of bike purchase. This might be the best $100 youy ever spend. And you never know - they may give yo a list of fit reccomendations that can be accomplished with your Trek with a few component swaps. THis might be the most important $100 you spend.

Also, other budget touring frames I can think of: Nashbar, Soma, Tweed... and there are others.

One other thought - don't thumb your nose at 26" wheels. If the correct frame size with 700C leaves you with too little stand over clearance, a 26" wheel frame in the smae size might be a better fit.
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