Re-raking a steel fork…

2 03 2011

Steel isn't just real you can bend it!

If you have a modern bike it most likely has a high trail front end geometry that’s not designed to carry a front only or front biased load.  That’s not a problem if you carry your cargo on a rear rack, but if you want to do brevets with access to your cargo on the go you need it in a handlebar bag or perhaps you want to add a porteur rack to the front of your bike and carry heavy items there you’ll be fighting your bike.  This is because high trail bikes have a lot of wheel flop so when you have weight up front it makes the wheel veer from side to side with poor stability.

If your fork is carbon, aluminum or really burly straight steel tubing you can’t do much about it.  You’ll have to get a custom fork made.  However, if you have a classic curved steel fork like the Surly LHT or Cross Check you can have your fork re-raked at a modest cost.  This involves bending the fork to add more curve which lowers the bike’s trail.  Since the bend also reduces the axle to crown height of the fork the head tube angle will steepen as well which also will lower the bike’s trail.

It follows that if you steepen the head tube you will also steepen the seat tube so there is a limit to how much of a change you can make.

The 58cm 700c LHT has 72mm of trail compared to 30-40mm of trail for a typical front loading randonneur bike.

David at the Ready to Ride Blog tried to re-rake his Rivendell Atlantis’s fork and eventually got a custom fork made for that bike to get the low trail geometry he was after:

Note: that the problem he had bending the Atlantis’ stock fork relates to the canti posts hitting the bending apparatus and may not be an issue if the builder’s apparatus is different to the one used in this case.

I think Sharon would find it easier to ride her new Surly Cross Check with a low trail geometry and her gear strapped to a PR rack on the front of the bike.  I’d also like to try my LHT with a lower trail fork – say in the 45mm range. Nothing life threatening, but it would make an interesting and relatively low cost project.


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12 responses

2 03 2011
Foraker

Looking forward to reading about how that works out.

Here’s another new bike product that looks interesting.
http://www.slidepadbrake.com/pages/faq

Not sure how the pad retracts (spring most likely?) or how well it works in mud/freezing slush/snow, but I like that these guys are thinking.

2 03 2011
adventure!

Interesting…I’ve got an LHT. I use a handlebar bag and front panniers. I haven’t noticed anything really bad with steering, but it would be interesting to see how well it would handle with a re-raked fork.

How long have you been using the re-raked LHT? Any issues with toe overlap? And how much did it cost you?

2 03 2011
thelazyrando

@adventure – do you use a handlebar bag and front panniers without a rear load?

2 03 2011
adventure!

Sometimes. But if I’m touring-touring, it’s front and back panniers.

2 03 2011
thelazyrando

If I try and ride my LHT with a front only load I can’t let go of the bars or it will veer to the ditch. With a rear only load or a balanced load I can ride no hands easily.

2 03 2011
adventure!

thelazyrando–Was that pre or post fork rake adjustment?

2 03 2011
thelazyrando

The 58cm 700c LHT has a 71 deg HT angle and 45mm of fork offset resulting in 72mm of trail. I haven’t re-raked any forks yet so there is no post raking values.

3 03 2011
Rich

My LHT seems quite stable with front panniers and bar bag (ie. no shimmy) but your right in that it can pull to one side if your riding no-handed and the road changes camber. With just a bar bag this effect is even worse but due to having less weight on the fork, so riding no-handed is a no-no unless its pancake flat.

I wonder if a cross-check fork would be a good candidate for a re-rake? afteral its almost identical just 10mm taller, so should end up same effective length as the LHT fork after the re-rake.

3 03 2011
thelazyrando

@Rich – my goal would be to be able to load my LHT up front on a porteur rack so it would be like having a very heavy handlebar bag on it. Good tip about the CC fork – I didn’t know that.

30 11 2013
emanuelferretti
30 11 2013
Vik

Emanuel – very nice – let us know when you have some testing results. What is the range of rake values you can achieve with that fork?

2 12 2013
emanuelferretti

40-62mm circa.I wanted to do 0-100 but it would have meant a lot more work.

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