car5car

I have steel front wheel 27x1.25
alum rear 700c x 23c

BikingViking793 

What year?

pastorbobnlnh 

It depends on the model year.

If it is a '70s model the front is the original and the 700c is a replacement. Sometime in the mid to late '80s Schwinn probably switched to 700c.

Welcome to Bike Forums.

Reynolds 531 

I may be wrong, 27 inch

IIRC, 27 x 1 1/4, which is completely different from 27 x 1.25. I'm not wrong about that part

car5car

Sorry, year is 81
Thanks for responses, rear is LP18 Weinmann with 8 sprockets, found label, I guess previous owner upgraded, OEM wheels had 5 (???)sprockets, I think. Hopefully this upgrade increases value. Trying to figure out if $40+tax was a good deal. After riding Chinese bikes it is definitely upgrade for me.

alcjphil

You have your answer. That bike could not possibly have come with a cassette type wheel. However, a 700c front wheel with an alloy rim would be a big upgrade. As well there are far more choices of 700c tires out there. The mismatched wheels really detract from value if you want to resell. You paid about what the bike is currently worth, getting more for it without a front wheel change is going to be very difficult

USAZorro

From my perspective, you got a very good deal. The bike looks clean and the cassette alone could cost you more than $40.00.

reroll

In 1981 rear dropout spacing was almost always 126mm and an 8-speed free hub or freewheel requires at least 130mm spacing.

Reynolds 531 

130mm spacing is translated as:

" when I put in the 130 rear wheel, I use my thumbs to push on each dropout 2mm, and slide the wheel in"

52telecaster

Always worked for me.

reroll

Yes, that can be done, although not recommended, and is a good sign that your frame has its original, "straight and square", 126mm spacing which has not been randomly "cold spaced" to 130mm, a pracitise which was not infrequently done in the early to mid-1980s. However, by doing as you are doing and as to why this would not be recommended, which anybody with a mechanical engineering background could explain, the rear frame triangulation (seat tube and the pair of stays) would become preloaded in ways in which it was not designed to be, which in use could ultimately lead to premature failure of any of the components of the rear triangle, not to mention potential frame misalignment.

Reynolds 531 

Not really the place for an argument about this, but...

I have been an engineer for so long I think I am much closer to Henry Royce throwing his hands in the air and proclaiming "in the final analysis, all materials are rubber", than I am to a wet behind the ears graduate fussing about 2mm deflection over 400mm.

A chainstay is a spring, not a block of iron. (Proof: I can move a Schwinn chainstay spring with my thumb, I cannot move a cast iron ingot with my thumb)

Second proof: Toss out anecdotal information, try to force that chainstay / seatstay combination past yield strength, to remain at 130 instead of 126. Just see what happens. (science!)

^ the above is in all in good humour^

PS everytime you pedal, the frame is preloaded. And then you pedal with the other foot and reverse the load!

reroll

Also in good humour here, with the spelling of humour, not of American English humor, you must be British and your "proofs" are riddled with assumptions, qualitative perhaps but not actually proofs. I have been a daily BBC News reader and HYS contributor for a long time and have been a mechanical engineer since long before that. Any amount of springiness preloaded onto rear triangulation goes beyond its original design and such a preload can lead to premature failure, eventually.


BTW, former PM May made a very fine effort, Bojo is now thankfully gone and Truss remains to yet explain her ambitions.

Reynolds 531 

You just couldn't resist a passive aggressive snarky comment.

Definition of spring is to be preloaded, otherwise it is a piece of metal.

Maths is NOT engineering.

By the time a person chooses to debate "springiness" and "original design" with a number, they will be forced to drag Youngs Modulus out of the "we wrote it down so it must be correct" archives, and reveal yet another "proof" with a number (E) that is complete rubbish.

Such is my contention as to why observation is greater than calculation for a bicycle frame being forcibly flexed 0.3 degrees.

I throw away the maths because rubbish numbers in, rubbish numbers out.

Still in good humour, but also done.

dedhed

It's a Schwinn, Not known for their premature failure, most will survive the apocalypse.