gugie 

(reposted here from the 650b Google group site)

There's a short list of proper tools to properly respace a rear triangle. A 2X4, a string and tape measure, and a pair of dropout straighteners (which could be as simple as some nuts, bolts, and washers) and you're set.

Rerake a fork? You've gotta be able to measure the rake, check to see if they're centered, those dropout straighteners (again), and a way to rake the forks without kinking them. That's a lot of tools. I have a pair of vintage (that means old) Zeus dropout tools and a no-longer-made Park FT-4 fork gauge which I learned to use working in shops in the early 80's. I figured out how to modify (slightly) an online-posted DIY fork jig so I could easily measure rake. Commercial fork rake mandrels are pretty expensive, so I found one that would utilize my woodworking skills. Of course, I modified the plans on that one too.

Here's the full kit I came up with.

unterhausen

fork rake checker might be a little overkill, but I like it. What radius is your mandrel?

FastJake

I've never had a desire to re-rake a fork. Why would I want to do such a thing?

noglider 

Very clever, @gugie!

You might want to rerake if you think it would improve handling or steering. I have an old Raleigh Twenty, and @rhm advised me that while I'm widening the fork to accommodate a modern (100mm) hub, I might as well reduce the rake on the fork. In his opinion, there is too much rake in it. I asked him how much, and he said he didn't know. I'm not sure how much I removed. Probably a centimeter or less. I can't say it's better, but it definitely isn't worse. Getting these things right on a small wheel bike is apparently trickier than on a large wheel bike.

SJX426 

@FastJake - here is a reason. This is a very hard to find, unique to Trek 700 series frames from the early 80's. I had the frame but not the fork. Found a fork on CL and then saw it was bent but bought it anyway.
[IMG]WP_20150430_006 on Flickr[/IMG]

Used my ingenuity:
[IMG]P1030002, on Flickr[/IMG]

To get close:
[IMG]P1020998, on Flickr[/IMG]

But I need to measure to finalize the adjustment.

How long was the 2x4?
[IMG]P1030007, on Flickr[/IMG]

Allows for fine tuning!

Dave Moulton address this as well: Dave Moulton's Blog - Dave Moulton's Bike Blog - Straightening steel*forks

Grand Bois

I once adjusted the rake of a replacement fork to match the original.

gugie 

You can brag to your friends that you can bend steel with your bare hands.

That and the handling and steering thing that @noglider alluded to.

gugie 

Yes, the simple method that you can find at Alex Wetmore's site is all you really need, but I had some 8020 cutoffs at work, and I figured I might want to make a fork someday.

The original plans were for a 5" radius, I made it 6", just a personal preference. It was easy enough to do, I CAD'ed out the original plans at 1:1 and printed them out on 11x17. I decided to change to 6" after that, so I just scaled the print to 6/5, or 120% on a copier. Took that and glued it to some 1/4" fiberboard and jigsawed/sanded it to make a template. I used the template to make 2 pieces out of 1X poplar, jigsawed closed to the edge, temporarily screwed the template to the pieces and used a router pattern bit to make them exact to the template. A 45 degree bevel was added to mirrored sides, then glued and screwed together.

If one doesn't have CAD skills, you can just print out the plans from the links at my flickr account, measure the bottom edge and scale it up on a copying machine. You can scale the rake up or down as you like easily with that method.

gugie 

[QUOTE=SJX426;17926097]

How long was the 2x4?
[IMG]P1030007, on Flickr[/IMG]

I think I spent too much time on mine! Very clever!

SJX426 

@gugie - I think it is about 8'. Makes it easy to be slow and use small amount of force. "Give me a lever and I can move the world."

I had an hub from another trek with shot bearings. The steerer was straight so it was mounted in the vice right up to the crown race mounting area, full length:
[IMG]P1020996 on Flickr[/IMG]

I wanted to make sure I caught the crown:
[IMG]P1030005 on Flickr[/IMG]

The hub could rotate so that was good and I tried to get the middle of it for uniform force on the tips:
[IMG]P1030006 on Flickr[/IMG]

In case the legs are not uniform, I will skew the 2x4 one way or the other on the hub. I need to measure before I do anything else. If I still lived in the Portland area, I would come by!
Not only was it important for me to have the right fork for the crown but this model has a 38 mm offset which is less than most aftermarket forks, typically 40-43. The only other option was to use a track fork (chrome) from Soma for $127 + shipping. I paid $25 for this fork. It was worth the risk of a buckled fork for me and with Dave's article as encouragement. A number of people told me it was trash. I don't think so.

vintage cellar

BITD alot of racers had very little money and crashes were frequent - especially on the track. Fork and frame straightening was a standard thing to do.

Old-timers would bring in bikes to one shop I worked at in the early 1980's. If you pulled out the fork, the steerer often had more than one bow to it - the thing had been straightened more than once ! And they used it like that for years with no problems other than it made headset adjustment kinda tricky sometimes.

Alot of those old-timers had grown up in the Great Depression and they didn't toss things away like nowadays.

An old time mechanic I knew could do amazing things with a rubber mallet when it came time to move metal. Not an easy thing to teach in writing.
I should do a video on this before I croak. Be a nice memorial to my manic mechanic mentor.

noglider 

But what are the effects of changes in fork rake?

AnkleWork

Good question. The effects of rake have not been published on the internet for over seventeen months.

gugie 

[QUOTE=AnkleWork;19294131]Good question. The effects of rake have not been published on the internet for over seventeen months.[/QUOTE @noglider

Not sure about the context of the question, but Tom Matchak wrote up an excellent article on this subject.

speedy25

I have had to "adjust" bent forks as well. With a little ingenuity it can be done. Nice to see others have figured it out too.

-SP

TallRider

As the following comment implied, there's a lot of info out there.
In recent years, largely due to Jan Heine at Bicycle Quarterly, traditional French randoneering-bike steering geometry has become more popular. These forks have greater rake, and less trail, which leads to more responsive steering and less "wheel flop factor" (the degree to which turning the front wheel lowers the front end, thus meaning gravity pressures the bike to turn the wheel). There has been a lot of debate over the actual value here. Jan Heine and the guys at Bicycle Quarterly swear by low-trail steering geometry, which seems particularly well-suited to using a bike with front loads (large handlebar bag or front panniers). This allows a more flexible/springy frame while still carrying some load (frames must be stiffer to not experience front-wheel shimmy with rear loads).

Jan Heine's brief overview (the technical part is all in Bicycle Quarterly):

The overall value has been debated by many framebuilders, and I came away from my reading less confident about the value for most riding (apart from front loads).

TallRider

This first picture of the fork looks like the blades are bent backwards from a front-end collision. Certainly makes me wary of the strength at the crown interface (either between steerer tube and crown, or crown and blades). Am I seeing the picture wrong or misunderstanding what you did?

gugie 

No one who's read my many posts on this subject will be surprised that I'm in the low trail camp.

If you're just riding with no load on your bike, the advantages are either small, or non-existant with low-trail, depending on who you ask. If you're a Strava user and judge your rides by how you rank against others climbing a certain hill, or timing a certain section, odds are you're not a low trail candidate, since you're unlikely to want to carry anything but a spare tube. There's nothing wrong with that, I rode for a few decades in that mode when I was younger.

Tht was 30 lbs ago. I still love to ride, but now my handlebars are level with my saddle, I stop and take pictures, and like to carry some food, a few more tools, and some extra clothing. There's a big advantage to putting all that in a handlebar bag, the extra load doesn't affect handling when combined with low trail. I started noticing that a springier frame is a more lively ride, and I can stand and ride with a front load, whereas a rear load makes that very difficult.

Bandera

Yep, the first shop I had a stake in was truly Old School dating back to the early 20th century.
By the time I got there the fire marshal had forced removal of the brazing equipment (for good reason) but the flat table and fork jig with all of the tools, mandrels and fitting were still in place and overseen by a master of the trade who I apprenticed under. Nothing was considered disposable until it was well and truly trashed beyond safe repair.

Aside from the inevitable race crash repairs and lost arguments with curbs those tools got a regular work out in QC/QA on any number of new framesets that were incorrectly aligned from various suppliers or damaged in shipping.

Great tools to work with and very satisfying to have a reputation for putting excellent handling machines into our customers hands whether a Pixie or a Paramount.

-Bandera

TimothyH

I have nothing to add to the conversation about forks but wanted to acknowledge anyone who works on bikes while wearing English wingtips, hopefully with argyle socks as well.
@SJX426, please give those things a proper polish.


-Tim-

noglider 

What a fantastic article. Thank you so much. Was this one of the seminal articles that helped propel this trend, which really is a niche, but it's very attractive to me.

I'm not quite at the point of having someone modify my frame or fork, but I'm fantasizing and figuring if it would be worthwhile. My International is still a work in progress, and if I'm lucky, I'll be able to put 32mm tires under full fenders. I haven't worked out my luggage preference. It handles a pair of front panniers very well, but that makes placing my dynamo headlight a puzzle. And whatever I work out would not work with a handlebar bag. It seems I would have to have either panniers or a handlebar bag and not be able to switch if I keep the light setup the same.

So if I'm happy with 32mm tires, and I might be, and since the bike rides great with front panniers, I may need to do nothing.

On the other hand, I have a Super Course I like as much, and being cheaper and in horrific cosmetic condition, I could hardly make things worse if I subject it to a torch. Its chainstays may be longer and more ready for a 650B conversion.

I had Bike Mechanic Hal, at Bicycle Habitat, spread the stays of my International to 130, and that proved to be a very worthwhile thing. The wheel goes in and out easily. I'm thinking of changing my Super Course's drivetrain to something modern.

gugie 

Not hard to accomodate at all, Tom.



Each set of lowriders is easily removable with three screws.

79pmooney

Watch "Stars and Watercarriers". You will see racers straightening their forks after a crash, jumping on and chasing. (We don't know if they rode the next stage on the same fork. Probably depended on the budget of the team.)

Ben

Rowan

I know that this is obvious to most who have posted here... but should there be a disclaimer somewhere that this really only works with steel forks? Not CF, probably not aluminium, and good luck with Ti.

gugie 

Definitely not CF nor aluminum. Ti I couldn't comment on.