does wheel size matter?

[neilhapgood]

Hi all, I hope you are well, I've had a TSDZ2 for a few years on an old Trek mountain bike, I use it daily for a 16 mile round trip commute, sometimes pulling a trailer weighing about 20kg.

The commute is flat all the way, mainly on a canal path, I'm thinking of changing the donor bike as I would like disc brakes and maybe larger wheels. There are lots of good second hand hybrids out there, a Cannondale quick cx has come up cheap as the crank needs replacing which would obviously be ideal. Couple of questions if people don't mind:

1 - would I notice much difference between 26" and 700c wheels? I currently run fairly skinny tyres on the bike and generally ride at about 20mph all the way. I'm therefore wondering if I would notice any difference in speed, battery consumption or riding experience with bigger wheels?

2 - The Cannondale quick has the cables under the BB as per the attached photo, would I be able to remove the guide and let the cables run between BB and Motor?

Any input on either of those would be great, thanks all!

 

[sjpt]

As long as you had a similar width and style tyre I don't think you'd notice much difference between 26" and 700C. The difference would probably be masked by other differences between the bikes.

Not at all sure about fitting the motor.

 

[Sturmey]

Your wheel width or particularly your chainstays looks wide and there may be a problem with the motor chainwheel housing touching the chainstay. Photo below (although its for the wider axle kit on fatbike) gives some indication of potential problem but you need to carefully measure this for yourself. Its possible to fit only a small spacer with standard kit or dimple the frame by hitting with a hammer as was recommended on one of the original installation videos!!
I think the gear cables will also have to be rearranged.

 

[Kinninvie]

You can remove the bottom cable guide as the motor will hold the cables up.
I have done the same on my Cannondale trail.
As said above the chainstay width may be a problem, my bike runs a 2.25 tyre max and is ok but if that bike takes a wider tyre then it may not be an easy conversion.

 

[Bikes4two]

I've fitted TSDZ2 to bikes 5 times now and one of the bike's had a similar downtube design where the cables exit the frame - so a couple of problems I can see are:

• On the bike I did I had to cut away a bit of the frame (see pic below) to allow the TSDZ2 to fit in the BB
• Those two cables - I didn't have to cope with a disc brake cable run - as regards the rear deraileur cable- after I'd removed the cable guide, I was able to route the cable through a short length of gear cable outer. It was a tight fit and required a bit of jiggling to get it into place. If the disc brake cable is larger than a gear outer cable, then you may not be able to route it between the BB shell and motor as it is only a very small space.

 

[Bikes4two]

Wheel size - I've had several bikes with 26" and 700c wheels - For the type of riding I do, the 26" invariably comes in a frame that makes the bike more suitable for gravel/rough tracks but not as fast as a 700c wheel/frame on smoother surfaces.

The differences as such are as much down to the overall frame design and its intended purpose than 26" vs 700c wheel size per se.

 

[guerney]

I was towing a heavy bike trailer up and down hills all summer with a Dahon Helios with 20" wheels (BBS01B), and as @Sturmey pointed out, you get more thrust from a smaller wheel. But the difference between 26" and 700c, doesn't seem substantial.

Sprocket wear

For practical reasons, you might just have to put a plastic screen in front of the motor to protect it. The mudguard would have to go so low it would probably get in the way. If necessary, it should be able to go as low as the pedals?

www.pedelecs.co.uk

 

[Sturmey]

But the difference between 26" and 700c, doesn't seem substantial.

The actual nominal difference between 26 inch and 28 inch is approx 8%. However, the actual difference can be much less depending on the tyres and a little arithmetic shows this.
The 700c rim bed (where the tyre wire/cord fits) is actually 622mm or 24.5 inches.
The 26 inch rim bed is 559mm or 22 inches.
So lets compare two wheels, lets say the 700c has narrow 1.25 (32mm)height tyres when measured and the 26 inch MTB has 2 inch high tyre when measured.
In this case then the 700c wheel actual size/diameter will be 24.5 +1.25 +1.25 =27 inches.
The 26 inch wheel will be 22+2+2=26 inches.
The actual difference will be an inch which works out at less than 4%.
The difference could even be less with smaller 700c road tyres.

Sometimes its important to know the difference between nominal values and actual measured values.

 

[vidtek]

@neilhapgood
This may assist BB limited space

Cheers Tony.