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wanted to buy: 20" P38 fork

I would like to buy a 20" threaded fork for a Lightning P38 bike. Would prefer the wider touring style fork that can work with fatter tires, but will consider a narrow racing fork too.

I have a 16"/17" P-38 suspension fork to trade or sell if anybody is interested.

Thanks and safe riding,
Joel Dickman


If you don't mind, I was wondering what your reasons were for changing to a 20" fork instead of staying with the 16" fork?


I have bikes with both the 16" (ISO 349) and 20" (ISO 406) front wheels. I am 5'10" tall with a 42" ex-seam, and the little 16" front wheel makes it easier for me to get both feet planted flat on the ground when I stop. This is nice when I'm exhausted and the road surface is slippery.

But the larger 20" front wheel gives me a somewhat smoother ride on the poorly maintained roads around Chicago. I would not claim the difference is night and day, but it is definitely noticeable. A smoother ride means I can crank a little harder and go a little faster. There are also far more different tires available in the 20" ISO 406 size, and they can be purchased easily. The 16" ISO 349 tire is considered more of an oddball size at bike shops.

As usual, one size does not fit all. If you only ride on beautiful smooth roads, the smaller wheel/tire will not handicap you. If you are height-challenged - with an ex-seam shorter than mine - you may be better off with the 16" front wheel.

So the choice depends on:

a) most importantly your own ex-seam,
b) the quality of the road surfaces you ride on,
c) your willingness to put up with the smaller selection of tires in the 16" size and lesser availability,
d) and your personal riding style - are you more of a speed freak, or more of a smell-the-roses tourist?

The newest Lightning seats may make it easier to get your feet flat when stopped, though I have not tried them yet.

Safe riding,


Thank you for your willingness to share your experiences and knowledge. I do appreciate it very much (being a Newbie).

I did a weak effort search, thinking this question has been debated before, and it gave me some info but not exactly what I was looking for.

Why do you run ISO 406 size and not 451, and is there any measurable difference in your experience with speed?


Hi again Barret,

I believe Rick Martin and Ben Fox have P-38 bikes equipped with ISO 451 20" front wheels, so it can be done. (Ben's bike is pictured in the gallery area of this site - it is the silver bike with the tail sock.) The 451 wheel is about two inches larger in diameter than the ISO 406. I am going to try it myself in the near future, just for the hell of it. I like to experiment.

However... the 451 wheel can cause more problems with heel interference and even hard crankset interference in some cases. It will depend on the particular P-38 frame size, the fork you are using, the extent to which your crankset boom is extended, the size of your 451 tire, your crankset length, and even your shoe size.

There might be chainline headaches to work around too...

I think Ben did an end run around the crankset interference problem by using very short crankarms, and used Paul Motolite V-brakes with a Lightning touring fork. I am too cheap to spend $100 for a set of Paul brakes, so I am going to try drilling out a spare set of Odyssey A-brakes instead to stretch the up and down range of brake pad movement.

ISO 451 tires are kind of like ISO 349 16" tires in terms of selection and availability: regarded as an oddball size at most bike shops. I do not think there are any fat tires available in this size either, like the Tioga Comp Pool, Greenspeed Scorcher, or the fatter Primo Comets. But don't quote me on this. Fatter tires may exist in this size.

Possible benefits? An incrementally increased smoothness in comparison with the ISO 406 on real-world imperfect roads, with the possible speed benefit that smoothness can allow.

When I get around to doing this, I will report back about my experience. If Ben Fox or Rick Martin are reading this, I would invite you to share your impressions for good and/or ill. I think other Lightning riders would be curious.

Just remembered: before I started riding Lightning bikes, I tried putting an ISO 451 20" front wheel on an ATP Vision R40 bike that originally had a 16" wheel. (Poached a fork and wheel from my Ryan Vanguard LWB). I liked the way the Vision bike felt with the bigger wheel.

Safe riding,

I've had the 451 front wheel with Stelvoi tire on for about 2 years now.
I sold the 406 size wheel after 1 year,[I had kept it around in case I decided to return to it.]
The Paul brake works great and allows you to move back in forth between the 2 wheel sizes if you want.
I had no issues with the chainline. The cranks are 153mm and I'm 5' 7" with a 40.5 xseam.
The frame size is large.
There is no hard wheel to crank interferance.
I am very happy with this setup and it is faster smoother riding.
The handling is unaffected by the larger wheel. The fork is the wider one with the lugged crown.
I can't put my feet flat on the ground ,I'm on tip toes ,but this is not a problem.I'm able to keep one foot clipped in and one on the ground at stop lights.
Granted if the ground is slippery I would need both feet down.

I've been kicking aorund the idea of going to a 451 wheel on the front of my P38 for the reasons you've stated.
I'm 6'4" and have an 2007 XL P38 with the touring fork with the lugged crown and 175mm cranks. Other than going to the Paul brake, are there any other modifications that need to be made to accomodate the 451 wheel? Is a new fork needed? Is there a Velocity wheel available in that size? How about tire choices?
Thanks for your input.

I can't speak for Ben Fox, but as I read his note it sounds like going to the Paul Moto Lite brake and the shorter cranks were the only things he needed to do in order to switch to the larger front wheel.

Since you are 6'4", you probably will not need shorter cranks. You just will have to work out a front braking solution.

Looking at the Velocity website, the only ISO 451 rim I see is the Fusion. They might have other 451 rims that are not shown though. And I am sure they would be happy to build up a wheel for you if you cross their palm with silver.



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