Terry front wheel (ISO 520 vs 540), big difference?

Question

Preamble
I'm building up an old early 80s Terry Precision bicycle. Most of my time has been spent researching and sourcing the front wheel. It's a smaller frame which uses a smaller front wheel for shorter women. I learned that many small Terry frames use an ISO 520 24" front wheel so I went hunting around for that. None of my local LBS could source any 520 parts. I found a couple of online retailers that had the 24" road rims (i.e. not 24" BMX rims, typically ISO 507) and tires/tubes. I bought two rims, two tires, and three tubes for future spares.

I built the wheel recently and noticed that the brake reach on the front was about 20 mm more than on the rear wheel, which is a standard 700C (ISO 622). I realize now that the earliest Terry Precision bikes used the even-less-common 600A wheel size, or ISO 540.

Question
Now I'm in a strange situation where I have invested quite a bit into a slightly wrong wheel size. At worst it will sit 20 mm lower in the front and I'll need to find a longer reach caliper brake for the front rim. Is that a problem?

Side question: does anyone know any companies that sell ISO 540 road rims (and tires/tubes)?

This whole front wheel situation kinda rags on my otherwise purist Terry restoration so I'm not sure what the best course of action is to proceed.

Edit
Turns out that ISO 540 is the size of some wheelchair rims today (along with 507). Has anyone ever used a wheelchair rim for their bike? Where can I find one?

P.S. I know these are many questions and that's against SE guidelines, but to be clear, the main question I have is whether or not using my ISO 520 wheel would be a big deal.

Answer 1

Interesting—Sheldon Brown's tire-sizing chart refers to the 540 size as "British juvenile or wheelchair"

In any case: The 520 wheel (which his chart lists as the Terry size—looking at the Terry website, I see they sell both sizes) will pitch you forward slightly and give you a slightly steeper effective head-tube angle. I don't think that would be a big difference. And you'll need to adjust your brake pads. In theory the size difference could be offset by using a fatter tire, but in practice, I think fatter tires are not made for the 520 size.

I've never heard of anyone using a wheelchair rim on a bike—the only possible downside I would imagine might be A) if they aren't available in the spoke count you want, or B) the braking surface.

You might contact Terry directly and see what they think.

Answer 2

There are plenty of 'long reach' sidepull brakes around, the problem is that none of them are any good. Department store mountain bikes come with them, they are a rare find sold as replacement/accessories. They flex/swing fore/aft quite a bit and tend to be made of poor quality materials with a spongy feel.

As for the parts you have bought, there are laws regarding distance selling and you can send them back hassle free. However, if you want to plough the 520 furrow, give the folks at Airnimal a call. They are very nice people and support their 520 rim bikes with spares at reasonable prices:

http://www.airnimal.eu/Reference/FAQCham.php

As for 600A (540/541), these were a common size on 'juvenile' 5 speed drop-handlebar road bikes by the likes of Raleigh up until ~1990 when 24" wheel MTB bikes came along, decimating any demand for anything else. Typically they were steel rims rather than alloy with Maillard bolt-on hubs. 650A made it to the high end, for time trial bikes, but 600A was 'juvenile' only in those days.

Another source you may want to investigate is Alex Rims. Drop them an email to see what they can do:

http://www.alexrims.com/product_detail.asp?btn=1&cat=1&id=44

Answer 3

The only ISO 540 narrow rims I have seen are Sun wheelchair rims. I think they make both tubular and clinchers. You can get narrow ISO 540 wheelchair tires from Sportaid.

I have been in the process of building a road bike for my 7 year old daughter. I decided to go with the ISO 520 rims. I purchase a set of Velocity Aerohead rims. However, the only tires available at this time are the Intense Micro Knobbies and the Terry tire. The Intese tires are available in 1", 1-1/8" and 1-3/8". The Terry tire is 24 x 1 (25-520) and I believe is made by Panaracer. All-in-all, 24" rims/tires are a pain since they have been made in 4 different ISO diameters including the Schwinn 'S'.

I hope this helps!

Answer 4

Beginning my search for a 540 rim for a Terry, and commenting: I went to the trouble of getting a Velocity 520 Aerohead rim built to a Shimano XT hub. It came from a trike and 'bent specialist,so it has the small compromise of assymetry, the hub including the integral mounting plate for a disc.

This early Terry, a Symmetry, in the largest frame size with a "24" front wheel, fits me, @5'6" and short arms, better than my usual 622 ride. What I don't like, though, is the unavailability of wider and more comfortable 25-32mm tires for the front. The Panaracer tires are standard 23mm nominal and maybe narrower in reality.

The Terry fork allows plenty of space for a fender in front,and the likely-Tektro front brake pads are at their lower limits, so there is room for a 540 - based wheel if the rim is 13-19mm between beads. Without that larger wheel, a larger and more comfortable rear tire, a 25-28mm, will make the handling more squirrely than it already is.

Answer 5

Old thread, but I figured I should post what I've found while trying to source 540 tires for a Raleigh I'm working on. Yes wheelchair tires are available in 540 size, but I don't think the profile being flatter would be good for a bicycle. Sunlite and Kenda offer a 540x1-3/8" bicycle tire. From the pictures they look identical.

The discussion about geometry and handling between a 540 rim vs. A 507 rim should be a moot point as a 24" tire is measured from tread to tread so the outside diameter of the wheel should be the same. Steering angle wouldn't change.

Brake reach would be your only issue and could be easily solved with longer brake arms.

540mm-507mm = 33mm÷2 = 16.5mm

difference in brake pad location. That's about 5/8" for my fellow Americans. Thing is sourcing narrow 507 rims. Most are 1.75" which may be too wide to physically fit your bike. If you don't mind spending some coin then Velocity would be the guys I would look at.