Guide for setting up skinny tires on lectric xp 2

[towardsdawn]

I had to switch out my tires for skinnier ones to get my bike to fit on my local bike racks (Montgomery County MD RideOn and Washington DC Metrobus). Here's a quick guide for anyone looking to do something similar.

1. Find out the maximum width of tires and weight your bus bike racks will accept. I ended up googling the tech specs for Sportworks which is what my buses use (probably yours too), and the narrowest one is the Sportworks DL2 which has a 55lb weight limit and 2.3in max tire width.

2. Check if your bike meets requirements, including whether or not it will fit in the mounting system. In bike racks with front hook mounting system which goes over the top of the front tire, you'll have to remove the front fender. The Lectric XP 2 with the battery removed and skinnier tires and rims just about clocks in at 55 lb.

3. Decide on a tire width and rim that fits your requirements. At the minimum I would look at rims which are double walled (strong enough for ebikes), 36 holes, with offset rim holes (to accommodate the increased spoke angle from the hub motor) and a tire-rim width combination that is recommended by the manufacturer (I used Schwalbe's tire width and rim width table located here). Good cheap rims would be the SE Bikes J24SG (which I used the 406x24) and the Weinmann DM30. Ideally the rim would also have angled rim holes but I had a hard time finding ones that didn't break the bank.

4. Decide on spoke cross pattern (I used 1-cross, but I think you can get away with radial on the rear hub, which would reduce the spoke angle). Measure for spokes (I posted the measurements of the front and rear hubs here). Input them into a calculator to get correct spoke lengths (I used Freespoke). The lower the flange exit angle, the easier it will be to mount the spokes. I did end up with an exit angle of 31 degrees on the rear hub, which I was just about able to mount on the J24SG rims.

5. Decide on spokes and tires. I would recommend tires certified for ebikes (Schwalbe has ECE-R75 and ebike 50 km/h certification on their tires, Grin recommends 13-14G spokes).

6. Mount your spokes, tires and rims and enjoy! I liked Grin's single-cross wheel build tutorial and Park Tools' wheel truing tutorial

 

[harryS]

Nice job. Single cross is stronger. Did you end putting the spokes on the hubmotor with the elbows all facing out?

 

[towardsdawn]

Nice job. Single cross is stronger. Did you end putting the spokes on the hubmotor with the elbows all facing out?

I did the elbows on the outside of the hub motor, which is what Grin recommends because it makes the wheel more stable

 

[scottsdalecommuter]

love the reflective tape! great idea. I had a mountain bike with wider tires that i had to really jam to get down in the fairly narrow front bus bike rack holder. that's a really nice looking city commuter bike!

 

[m@Robertson]

You can go Waaaaay past the recommended widths on the various manufacturer recommendations. One of the keys to getting it done safely is to oversize the tube. Its common knowledge you can put a Maxxis Hookworm on an 80mm fat bike rim. Thats a 26x2.50 tire. Its often done to lower a bike so a shorter rider can fit onto a one-size-fits-most DTC ebike frame. On similar 80mm rims, I put Schwalbe 26x2.35 Crazy Bobs on and they fit just fine. I used a 3.50 tube - its always a good idea to use an oversized tube on general principles, but on a zany rim combo, it assures the tire fits easily to the rim crochets.

Speaking of combos, look up the DT Swiss Tire Pressure And Dimension table. Thats the best of the manufacturer charts - WTB has another one on a web page. So long as you remember lawyers had to sign off on them, and the true range is a bit more than admitted to, these charts are good references, although again the DT Swiss with its tire widths going up to 5" is the best.

1-cross or radial should only be done as a last resort. You only do that when forced. 2-cross or even 3-cross is what you see on quality wheel builds where the builder is not forced to make compromises. For my own 20" wheel builds a pro wheel builder did 2-cross. One of them was elbows all-outside but that was more because it was so difficult to lace the thing in the first place (used Sapim Leader spokes which was fine from a structural standpoint, but would have been much smarter to use the butted 13/14 Sapim Strongs. Part of a wheel's necessary performance is it should flex, which means using thinner spokes that are high quality so they can flex and spring back without damage. The downside of that is you're spending over $1 per spoke and a bit more on top for a proper length brass nipple. My 26" fat hub wheels are 3-cross. Just barely able to make that happen and not have bad angles.

Speaking of angles, buying rims with angled spoke holes is a HUGE help to stringing the thing with a better pattern. This is my 20" Alienation Blacksheep rim, a BMX rim I use on the front of my Bullitt.

If you have a double-walled rim with straight holes you probably really are stuck with a sucky spoke pattern.

And be judicious about offset-from-center spokes. Part of a bicycle wheel's strength is derived from the triangle the spokes form from the hub to the rim. A quadrilateral is not as strong of a shape as a triangle in this regard. I've done it myself but its when I don't have a choice, not by preference. My 90mm carbon fiber deep dish wheels are not offset one bit and thats a good thing.