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700 front, 27 rear

Old 05-24-20, 12:21 PM
  #1  
kayakindude
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700 front, 27 rear

Hello, I have a 27 inch tandem that will get an electric upgrade shortly that uses a front hub system (swytch). One reason for buying the e-system was to switch it between the tandem and my wife's bike. Her bike rims are 700c. If I go 700c in the front for the tandem will it ride ok if I keep the 27 inch rear wheel?

Based on what I have read it would mean the front would ride about 4mm lower? Doesn't seem major but want some feedback. Thanks.
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Old 05-24-20, 12:56 PM
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I expect that she will adjust to any differences within a few hundred feet.
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Old 05-24-20, 01:44 PM
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Yes. the radius difference, for the same tire profile is 4mm. On a tandem this results in about half the very small head angle change as the wheelbase is much longer. Andy
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Old 05-24-20, 03:13 PM
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Thanks everyone for the quick replies. Andy great point on the angle being even less significant because the frame is longer.
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Old 05-24-20, 07:10 PM
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Will the rim brake pads (if equipped) adjust 4-5mm lower?
Identical sized tires? If you are running 27-1-1/4" tires, that's a 32mm tire. On paper at least, a 36mm tire would "level" you out.
Or put the heavy person on back.

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Old 05-24-20, 08:22 PM
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I'll be like riding downhill all the time.
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Old 05-24-20, 08:50 PM
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Originally Posted by Gresp15C View Post
I'll be like riding downhill all the time.
Just like Sport, Paul Bunyan's dog. The childhood story I recall had Paul feeding Sport under the kitchen cabinets so the dog, gifted with bigger then real life size like Paul, grew it's hind quarters but it's front stayed the "normal" size. This way Sport was always "walking" down hill. Andy
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Old 05-24-20, 09:50 PM
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You will not notice the difference in feel. The only real issue is whether you have rim brakes, and whether they can accomodate the difference.
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Old 05-24-20, 11:15 PM
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For years I rode a 26" rear 20" front recumbent. The downside was what to carry on long self supporting rides. A folding 26" tire, 20" tire, neither, or both?
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Old 05-25-20, 12:05 AM
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For years my old Cannondale touring bike has had a 700x23 front and 27x1 1/4 rear. I don't notice a thing.
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Old 05-25-20, 01:57 AM
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IMO, electric motors on any bicycle front wheel are a bit of a gamble.
With the overall weight and resulting strength demands of a front wheel on a tandem, even more so.


A powered front wheel on a loose surface, or wet/slippery spot is a bit un-nerving.
A front wheel motor is strictly a throttle actuated and can easily be in an overpowered mode in a turn.

Not certain, but I believe most front motors are 250 watt designs. The added weight of a tandem use might cause the
motor undo stress/torque requirements and premature burnout.

On background, I have sold electric bicycles as a factory rep.

rusty

Last edited by 100bikes; 05-25-20 at 02:01 AM.
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Old 05-25-20, 06:45 AM
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Originally Posted by 100bikes View Post
IMO, electric motors on any bicycle front wheel are a bit of a gamble.
With the overall weight and resulting strength demands of a front wheel on a tandem, even more so.


A powered front wheel on a loose surface, or wet/slippery spot is a bit un-nerving.
A front wheel motor is strictly a throttle actuated and can easily be in an overpowered mode in a turn.

Not certain, but I believe most front motors are 250 watt designs. The added weight of a tandem use might cause the
motor undo stress/torque requirements and premature burnout.

On background, I have sold electric bicycles as a factory rep.

rusty
Thanks Rusty,

I plan to only use the motor sparingly when on the tandem, only for really hard climbing and once we are past the 20-25 mile mark as a slight assist. This first kit is mainly to help the wife when riding solo close the gap with my pace. I'm more an 18mph average and she is 14. Telling her to get in better shape seems like a bad option 🙄

I do have adjustable brakes to compensate.

Last edited by kayakindude; 05-25-20 at 06:50 AM.
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Old 05-25-20, 03:40 PM
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Originally Posted by kayakindude View Post
Thanks Rusty,

I plan to only use the motor sparingly when on the tandem, only for really hard climbing and once we are past the 20-25 mile mark as a slight assist. This first kit is mainly to help the wife when riding solo close the gap with my pace. I'm more an 18mph average and she is 14. Telling her to get in better shape seems like a bad option 🙄

I do have adjustable brakes to compensate.
Gee do you think so?? Maybe you need to be willing to slow down when you ride together. Riding together is often like sex, it's the shared experience not the work out. And this goes for the tandem doubly so. Andy (who's on his third tandem).
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Old 05-25-20, 03:50 PM
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Originally Posted by Andrew R Stewart View Post
Gee do you think so?? Maybe you need to be willing to slow down when you ride together. Riding together is often like sex, it's the shared experience not the work out. And this goes for the tandem doubly so. Andy (who's on his third tandem).
Why Andy thanks for the advice 😁 that's what I currently do...we actually average 16 on the tandem. I was being sarcastic earlier, but no harm if a little e-assist can close the gap on longer solo rides as we head into our 50s. Agreed that whatever keeps us riding together works.
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Old 05-25-20, 04:27 PM
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Up front, worst case, you can get a new 700c fork. Go the cheapest (effective) route first, but on a decent tandem frame, I'd be willing to spend a bit more.
The size difference, insofar as handling is concerned, will be negligible, and easily compensated for with a slightly bigger tire, if you even bother at all.
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Old 05-25-20, 09:16 PM
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Agree with folks. Unless you're wife is a Princess (as in "The Princess and the Pea"), it will be hard for her to notice the 4mm diameter difference.
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