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Old 08-15-09, 05:06 PM   #1
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700c on a bike that came with 27 ?

So there's a thread on here about a Panasonic Sport 500 for my wife that i went to look at.

I picked it up.


Has the old, hard to find tires for 27x1 1/4 size.

What is the criteria that the bike has to meet to swap out for 700c wheel ?
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Old 08-15-09, 05:12 PM   #2
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I think you might need longer reach brakes, because I believe the 700C wheels are of a smaller diameter than a 27 incher. Check out the brakes to see if the shoes can be moved down a bit. best thing to do is take it to the LBS and have them test out a 700C wheel on it to find out.

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Old 08-15-09, 05:12 PM   #3
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700c's are smaller than 27", so the only qualifications are long reach brakes, which are easy to find. Dropout spacing matters as well, depending on how many speeds you have/plan on having.
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Old 08-15-09, 05:19 PM   #4
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Hmm..

Slipped my mind. I should try on the front wheel from my Univega.

As far as speeds, She wants to keep it a 10speed. Brakes do indeed move up and down.

I can always swap those out for a set of cheap Veloce's or something similar.
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Old 08-15-09, 05:20 PM   #5
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37" tyres are still easy enough to find here in the UK and as far as I understand, in the US as well - my own preference is the Panaracer Pasela Tourguard. However you get a wider choice of wheels if you go for 700C. I've swapped 700C's into a 27" wheel frame dozens of times and the only problem on about five occasions was that the existing brake calipers didn't reach the rims - you need to be able to drop the brake blocks about 4mm on some frames - on others they seem to match up, probably something to do with the frame angles and clearances? If they won't reach, you can often get deeper drop calipers - Tektro make some good, low priced dual pivot models. The easist way to find out is to try a pair of 700C wheels (any old ones will do) and check that the brakes can be made to contact the rim without catching the tyre wall, front and rear. If you are buying new 700C wheels, check the width between the rear drop-outs on the frame as some later ones are made for 9 or 10 speed cassette sprockets and they are wider. Good luck!
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Old 08-15-09, 05:21 PM   #6
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It's a trial-and-error thing. Some frames handle the switch with no problems, others won't. No way to tell beforehand. A visit to the LBS might be a good way to go for you.
I had an old Peugeot that was made for 27", but all I had ready was a set of 700cx35. Just managed to fit without the tires rubbing the bottom of the fork crown, and the brake pads reached the rims. Others bikes I've tried didn't work out.
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Old 08-15-09, 05:46 PM   #7
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I really don't think 27" tires are that much harder to find than 700C. I get everything I need from the internet anyway. Most local stores carry 26" tires mainly and the LBS will have some 27" in if I need them. May not be my choice brand but they usually have some.
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Old 08-15-09, 08:19 PM   #8
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If you go to 700c wheels brake reach is the first issue. If you can find nutted calipers with the appropriate reach, your done. 47-57mm brakes will work with some frames, others require 55-73mm reach to take a 700c wheel. If not, recessed mounting bolts on non-recessed frames create further problems. Most people swap 27" for 700c for several reasons. Your selection of wheels and tires increases greatly at 700c. 700c wheels tend to be lighter and accelerate faster than 27". Cassette rear wheels permit customized gearing and are hard to find in 27". If performance and gearing are not important, buy some 27"X1 1/4" Armadillos and keep what you've got.
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Old 08-15-09, 09:06 PM   #9
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Originally Posted by JAG410 View Post
700c's are smaller than 27", so the only qualifications are long reach brakes, which are easy to find. Dropout spacing matters as well, depending on how many speeds you have/plan on having.
The difference in diameter is 8 mm, so the difference in radius is 4 mm. If there's enough room in the brake shoe slots for both the front and rear brake shoes to move down 4 mm, you don't need a new set of brakes. All you need to do is install the wheels and position the brake shoes once the wheels are secure. It doesn't matter if teh shoes can't move down any farther once they are adjusted for the 700Cs. So rather than run out and search like heck for long brakes that have nut mountings (this will be hard if you don't want Weinmann or DiaCompe centerpulls), or start modifying your frame for recessed nuts, do a test fit and see if the existing brake calipers are ok. They really might be ok.

Last edited by Road Fan; 08-15-09 at 09:11 PM.
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Old 08-15-09, 09:36 PM   #10
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Unless you have a spare set of 700c wheels laying around, I wouldn't bother, as long as the current wheels are in good shape. There are plenty of good tire options in 27". If the current wheels are steel rims or the hubs are trashed, that's a different matter, although personally I'd be tempted to go with another 27" set if the brake reach is an issue.
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Old 08-15-09, 09:55 PM   #11
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Originally Posted by Oldpeddaller View Post
... my own preference is the Panaracer Pasela Tourguard. However you get a wider choice of wheels if you go for 700C. ...
I really like Paselas also, but I find I prefer the ride of the standard tire over the Tourguard version.

Generally speaking, there are less issues swapping form 27" to 700c than the other way around (clearance definitely won't be an issue, and it's usually easier to find longer reach brakes than super short ones).
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Old 08-15-09, 09:59 PM   #12
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D'ya have 27" hook bead rims? Some older bikes don't, and cannot safely hold a narrow high pressure tire.

I'd buy new tires and keep the old wheels if they are in decent shape, and the rims have the hook profile. If I already had some spare 700c wheels (I do), and planned to buy dual pivot brakes (very worthwhile), or do a drive train upgrade, then I'd swap out the wheels.

Bad LBS installed a new front tire on a friends bike, pumped to the max on the sidewall, 110 psi, for a 100lb rider. Glad I spotted the bulge before the tire blew out. That old Schwinn road bike does not have hook bead rims, and needs wide low pressure tires.
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Old 08-16-09, 10:33 PM   #13
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D'ya have 27" hook bead rims? Some older bikes don't, and cannot safely hold a narrow high pressure tire.

I'd buy new tires and keep the old wheels if they are in decent shape, and the rims have the hook profile. If I already had some spare 700c wheels (I do), and planned to buy dual pivot brakes (very worthwhile), or do a drive train upgrade, then I'd swap out the wheels.

Bad LBS installed a new front tire on a friends bike, pumped to the max on the sidewall, 110 psi, for a 100lb rider. Glad I spotted the bulge before the tire blew out. That old Schwinn road bike does not have hook bead rims, and needs wide low pressure tires.
I have a straight-sided rim on the front of one bike and just pump the tire (Serfas Seca) up to about 70# or so. I've done it with other tires as well. They've all been 100# rated tires but have run fine at the lower pressure.
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Old 08-16-09, 11:15 PM   #14
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I have several bikes with 27" wheels. I'd no trouble finding 27" tires at jensonusa. They are not necessarily listed under the 27" category. For example, I use Vittoria Zaffiro in both 1 1/8 and 1 1/4 widths. They're not listed under 27".

I'd converted an '86 Schwinn World to 700c wheels and 9-speed cassette. The major change: new rear brake caliper (Tektro xtra long reach). The front caliper was okay. The rear hub spacing was 126mm which was easily "stretched" to accommodate the 130mm spacing of the 700c cassette hub.

There may be other unexpected problems:
(1) My wife's Raleigh had 96mm spacing on the fork. I could not spread the fork to accommodate the more usual 100mm spacing of front wheels (whether 27" or 700c).
(2) The Schwinn World needed a derailleur hanger claw which got in the way of the chain and the smallest rear cog. So my 9-speed was effectively an 8-speed...

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Old 08-17-09, 12:16 AM   #15
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There's a bottom bracket drop of 4". Isn't much if the bike was originally meant for 27". You do need new brakes but a conversion usually poses no real difficulty. The only limiting factor is how big a tire you can mount on a 700C wheelset.
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Old 08-17-09, 04:34 AM   #16
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I think the rims on that bike are steel, so upgrading the wheels (either to alloy 27" or 700c) makes sense. I would see if you can test fit a 700c on the bike to check if the current brakes have enough adjustment -- if it turns out you need new brakes on top of the wheels it may not make $$ sense.

If I had just bought that bike and the wheels are in decent shape but the tires are shot, I would pick up a set of good cheap tires (Forte GT, Kenda, or Panaracer for a little more) and ride the bike for a while. Then, if after wearing through the first set of cheap tires it still feels good and I liked the bike, I would start thinking about investing the money in a new set of wheels.
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Old 08-17-09, 08:43 AM   #17
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I really don't think 27" tires are that much harder to find than 700C.
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37" tyres are still easy enough to find here in the UK and as far as I understand, in the US as well - my own preference is the Panaracer Pasela Tourguard. However you get a wider choice of wheels if you go for 700C.
Continental also makes some good tires in 27". I agree that they are not hard to find at Internet shops, but the selection is quite limited; even more so at a LBS. The good thing is that one can still use the same tubes as 700c. In my case, it turns out the Panaracer Pasela Tourguard is my favorite general tire and it comes in a ridiculous variety of sizes.
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Old 08-17-09, 09:01 AM   #18
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I am going to have a Nexus 8 wheel built up for use on a Raleigh Sprite.

I plan to use a 700C rim but do not plan to replace the front 27" wheel. Will this cause a problem?

Even though the bike came with 27" wheels, I figured getting the hub built on a 700C rim would make for better future compatibility with other bikes.
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Old 08-17-09, 10:13 AM   #19
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There's a bottom bracket drop of 4". Isn't much if the bike was originally meant for 27". You do need new brakes but a conversion usually poses no real difficulty. The only limiting factor is how big a tire you can mount on a 700C wheelset.
I really doubt the BB drop is actually 4 inches! that's 100 mm of drop, which is not at all common. Have you measured it? Pedal clearance is not the only thing going on here - greater BB drop moves the down tube closer to the front wheel, reducing the clearance between it and the wheel. Addition of a fender can reduce clearance considerably. Ameliorating the small clearance could involve moving the head tube forward or laying back the head tube. The first measure results in a long, sometimes too long, top tube, and and the second can affect steering behavior (flop).

In road bikes DeRosa and Richard Sachs are about as low as anything, and they use an 8cm drop. That's already lower than just about any other modern road bikes.

Plus, if the brake slots are long enough to adjust the brake shoe position 4 mm downward, why would he need new calipers? Do you know for a fact the existing brakes won't work? I would not want to give the OP advice that will cost $$, without full justification.
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Old 08-17-09, 10:18 AM   #20
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I think the rims on that bike are steel, so upgrading the wheels (either to alloy 27" or 700c) makes sense. I would see if you can test fit a 700c on the bike to check if the current brakes have enough adjustment -- if it turns out you need new brakes on top of the wheels it may not make $$ sense.

If I had just bought that bike and the wheels are in decent shape but the tires are shot, I would pick up a set of good cheap tires (Forte GT, Kenda, or Panaracer for a little more) and ride the bike for a while. Then, if after wearing through the first set of cheap tires it still feels good and I liked the bike, I would start thinking about investing the money in a new set of wheels.
+1! Just get it roadworthy and see if you like it. Then you'll know what you need to do to it.
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Old 08-17-09, 03:19 PM   #21
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Originally Posted by Frankinbiker View Post
I am going to have a Nexus 8 wheel built up for use on a Raleigh Sprite.

I plan to use a 700C rim but do not plan to replace the front 27" wheel. Will this cause a problem?

Even though the bike came with 27" wheels, I figured getting the hub built on a 700C rim would make for better future compatibility with other bikes.
When I built my Raleigh Sprite, I used the Tektro long reach sidepulls (R556) to work with the 27" wheelset I had made for it.

Had I gone to 700c, even these brakes might not have been long enough(looks like they'd work but it'd be close)



If you need even longer reach brakes, get the Dia-Compe 750 centerpulls.
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Old 08-24-09, 10:20 AM   #22
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[QUOTE=Frankinbiker;9501570]I am going to have a Nexus 8 wheel built up for use on a Raleigh Sprite.

I plan to use a 700C rim but do not plan to replace the front 27" wheel. Will this cause a problem?
QUOTE]

If the 27" front wheel you are planning to retain is steel rimmed, then I see a problem with not taking advantage of changing out the front rim/wheel with an aluminum alloy one that will provide you with much much better braking performance in the wet. Aluminum rims give much better coefficient of friction than steel chromed wheels (even dimpled ones). Remenber, on 2 wheeled vehicles like bicycles and motorcycles, your front brake can be up to 80 and sometimes 100 percent (rear wheel lofting emergency stoppies) of your braking power/ability. So any upgrade you can do on braking for that end of the bike is somethng that should not be passed up, IMO.

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Old 08-28-09, 09:59 PM   #23
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Don't sweat it. 27" inch tires are still easy to get, including some really good ones. As for switching to 700c, it can be done, but your braking will suffer due to the longer reach to the rims. I'd stick with the 27s if the wheels are in decent shape.
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Old 08-28-09, 11:29 PM   #24
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Had I gone to 700c, even these brakes might not have been long enough(looks like they'd work but it'd be close).
You have 8-12mm of room on those brakes. You only need 4mm, there would be no problem with a 700c conversion with that bike and those brakes.
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Old 08-28-09, 11:46 PM   #25
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If you can find a dealer that can get Tektro 900A's (not the 800A's with 73mm max reach, but the monster 900A's with 92mm), you can pretty much get any bike that came with 27's to accept 700C's:


http://www.tektro.com/02products/07rb.php

I'm going to see if I can get a pair of them to use on my hot rod Raleigh 20. No doubt the only dual pivot in existence that could possibly make the stock brake reach.

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