20 inch BMX rims with motorcycle tires

[Kingfish]

Yet another Addendum:

New Tire Link:
http://www.conti-online.com Continental Tires

Expanding Search to Motorcycle Rims:
As an alternative, decided to open myself up to more options as I began to have some serious concerns about having enough choice between rims and tires. The gating factors being: Diameter, Width, Aspect Ratio, Hole Count, Product Type/Usage, Quality of Workmanship, Reputation, Price, and Availability. Failure to meet criteria of any one of these attributes could sink a potential match. Here are some motorcycle rim manufacturers/suppliers that I reviewed:

http://www.mooseracing.com Moose Racing Rims (this official site is lame, so Google a supplier)
http://www.rkexcelamerica.com/mx_excel_rims.html Excel Rims (so is this one; other retailers do a better job)
http://www.prowheelracing.com/products/mx/rims Pro Wheel Racing Rims
http://www.buchananspokes.net/categorie ... l_rims.asp Buchanan's Rims; supplier of several types - including bare, unpunched rims for custom orders. Spendy!

Suppliers:
There are a lot of sites out there to help us find the proper tires and rims. The problem that I had with many of them is that they want us to provide the make, model, and year of the motorcycle/scooter before offering a selection which in my mind is ass-backwards if I already know the diameter, width, hole-count, etc. Google, TheFind, Amazon, eBay, and their ilk were of limited value, and often frustrating as a utility when attempting to craft a proper search string. One gem though stood out…

http://www.tyres-pneus-online.co.uk Pneus-Online finds the tyres we need in the UK! This gets the Most-Useful Website award: Big time saver, a great tool for comparison, with up to date reports, and best price listing. I found this site at like 9PM last night and I am still on it this morning. ***

Picking a Favorite:
I have decided upon the Continental Conti-Go! 2.75-18 M/C 48P TT (70-457) tyre mounted on an Excel Takasago 18x1.85 (457-47) 36h Rim. I will leave the front and rear to be the same since I am crafting a 2WD bike.

I cannot begin to explain the challenge here in attempting to match a tyre and rim – it was a struggle until I found the very last link Pneus-Online***. However by then I had pretty much figured out the math and formulas for converting the sizes on the fly and I was in the final stages of sorting out the suppliers.

Why Continental:
I have close to 9 months experience running the Continental Contact Reflex both F and R on my current e-build; they are adequate and give me little trouble. That ended up weighing in during in the process of removing unknowns from the calculus. There are some great manufacturers out there, but most of what they offer is difficult to source, and if it is found – pray it doesn’t cost your next-born child. The Continental Conti-Go appears to be a decent modern all-weather road tire, though I will need to pick something else for snow or off-road.


Continental Conti-Go! New City tyre for light motor bikes.

Why the 18” Wheel Size:
The Excel 18”/457mm rim when combined with the 2.75”/70mm wide tire (and similar aspect ratio) should not exceed a total diameter of 24”/610mm - thus meeting the criteria to drop the overall bike height by at least an inch/25mm. Presently I have the Mavic EX 729 Disc Rim with the Hookworms pegged for install - effectively setting the wheel diameter to 27.5”/700mm and exacerbating the already tall-for-a-medium-sized frame (it’s a Felt-Compulsion 1). Then I added Marzocchi 888 RC3 EVO DH forks which will raise the height even more.

As for why I picked 18” over 17” or 16”, I just thought that it might look a little odd if the tires were too small. The other problem is that the rear suspension framework is too narrow to load a 3”-wide tire; even if the diameter was smaller there’s just not enough room. Once I gave up on the 3”-wide tire idea another struggle ensued to find any tire narrow-enough to fit.

The last factor was based on selection and availability: There simply is not enough choice, and that can be easily proven by using the Pneus-Online*** website. U.S Domestic supplies are limited: I had to go look across the pond to Europe before I finally found the tyre.

The 1.85”/70mm-wide x 18”/457mm diameter Excel motorcross competition rim, being machined from lightweight 7-series aluminum, is stronger than any bicycle rim, and as a 22” equivalent-bike size - it falls neatly between the 20” and 24” inch gap. Trivia: This size also called an ISO457mm standard, 22x2.125, and 22x1.75, …and impossible to reliably find in bike-size.


Excel Takasago Signature Series Rims, available in several colors.

Caveats:

• There is lots of poop about the Excel rims needing their own spoke kits; another work item.
• Need to source a tube and rim-liner as well.
• Then figure out how to get the tires balanced.

No doubt it will be a burly-strong setup though when complete!

<pause to graze, looking for something to nibble on…>

Conclusions:
Q: Rhetorically, can we find and mount a 16”/406mm motorbike/scooter tire onto a 20” BMX wheel?
A: Yes, certainly. For example, mounting the Continental Conti-Go! 2.75-16 on say a Bombshell BMX Revolution Pro 1.75” Rim would create a wheel that drops a standard Mtb frame by more than 2 inches; a viable solution – it’s lighter, less expensive, more bike-like, and exceedingly meets the criteria.

My choices however are constrained by many factors, beginning with the narrowness of the frame. Picking a slightly larger rim expands the selection, raises the load characteristics and the top speed, and I end up getting a more durable pairing.

In the end, I guess one could say “if you look hard enough, you will likely find what you’re seeking”
…or maybe it will find you.

Trouble always finds me; no need to look that.

Thoughts? KF

[johnrobholmes]

It is going to be a heavy setup with the 18s. I choose 16s or 17s for my "hybrid" wheels. Even then, they are much heavier than bicycle parts. You will likely add about 8 pounds of rotating mass, depending on the tire you choose at 18". Have you added up the penalty yet?

[Kingfish]

It is going to be a heavy setup with the 18s. I choose 16s or 17s for my "hybrid" wheels. Even then, they are much heavier than bicycle parts. You will likely add about 8 pounds of rotating mass, depending on the tire you choose at 18". Have you added up the penalty yet?

That is a good question. Let’s take a look…

Mass of Tires:
Unfortunately I haven’t found a single motorcycle tire manufacturer that posts the weight of their products. However, if we calculate the difference between 18” tire and 16” tire:

18/16 = 1.125, or 1/8th more mass than a 16” tire

Certainly not very welcoming for city/commuting with lots of starts and stops, however if used in touring we would see more efficiency.

Motorcycle/Scooter Tires:

Continental ContiGo Tyre: TBD. I may make a run down to the Kawasaki dealership and throw a tire on the scale just to see what we are dealing with.

Heavy Bike Tires:
For point of conversation...

26” Hookworm tire: 26x2.50 = 1125g
26” Fat Frank tire: 26x2.50 = 940g

Motorcycle Rims - Excel:
I placed a call to the U.S. Distributor; curious, the sales rep went out to the warehouse weighed the items on the UPS shipping scale; I have no idea if this includes packaging.

Rim Weight of Excel 18x1.85 (32h): 3.8 lbs / 1724g
Spoke Kit Weight: 1.2 lbs / 544g

Compared to Bicycle, 8-9 gauge spokes are about 1.5 times the weight of 12 gauge spokes. However, the length of spoke for an 18” rim is less than the length for a 22” (26” bicycle) rim by 2/3s (with a 9C hub) because the spoke is now effectively 2” shorter. Doing the math on a 12-gauge spoke for a 26” bike rim verses a 9-gauge spoke for a motorcycle 18” rim, the calculation is:

(1.5) * (2/3) = 1, or in other words ~ it’s a wash.

I can confirm this with my shipment of Sapim spokes used on the Mavic-9C mating which weighted just over 2 pounds for 80 spokes & alloy nipples. Worst case; we pick up 0.3 pounds between two rims. Alloy nipples will be lighter than Stainless and Carbon Steel. Going to a 16” motorcycle rim would naturally reduce the spoke weight further.

Bike Rims:

Weight of Bombshell: TBD. Distributor won’t answer phones; email sent.
Weight of 26” Mavic EX 729 Disc Rim: 1.49 lbs/675g ~ 40% of the Excel mass.

Accessories:

Weight of the Rim-Strips: Negligible.
Weight of the Tube: TBD.

I run the Specialized Desert Protection Tube with my bike tires; they are more than twice the weight of a conventional tube but well worth the money: On my last long trek (to California) I picked up a nasty piece of road-wire-trash on the side of a very busy highway. I removed the wire, rolled the bike backward to cover the hole, and in less than 30 seconds the leak had stopped almost entirely (the tube was replaced at the next destination). This heavy tube though should not be required with a motorcycle tire.

Other weight comments:
Last week when I picked up my newly mated Mavic EX 729 Disc Rim & 9C hub the repair guy at REI thought they weighed 30 lbs and suggested that I make “two trips” to carry each hub out. I told him that he was mistaken, that those hubs don’t weigh more than 14 pounds each – so he weighed them and was completely floored: “I, I guess the weight is all concentrated… that’s what through me off”. No worries man. I carried the lot out in one load

BTW, one other reason for not selecting 17” rims is that the only size I could source in aluminum with 36h were 1.4” or 2.15” wide; both a little too far out of spec. However there are steel rims available in the 17x1.6 size.

John, what did you use for a 17” rim?

Accepting the Load:
Generally speaking, we are already living with a weight penalty with an EV over that of a pure human-powered transport. My ebikes in particular run heavier because I am interested on long-range which translate into larger battery capacity, the weight of which is countered by using LiPo. For commuting, the batts weigh 12 lbs/5.4kg, and for long-distance they were 46 lbs/21kg. I also broke 5 spokes on that trip with the non-hub tire (the same one with the received the flat)

When we are talking about mounting motorcycle or scooter tires onto a bike, regardless of which rim is chosen, we are blurring the distinction even more between bike, moped, and light-motorcycle.

I accept that weight burden because I seriously desire a more rugged tire system that is able to withstand the trash we are forced to drive through on the margins of these city streets and highways. I am also slowly migrating to more stout platforms for testing, and I can easily imagine my next frame (P2?) will be closer to motorcycle than bike; might as well start planning now to have burly wheels

~KF

[Kingfish]

Small note:
I am having trouble sourcing my dream tire. The Michelin Sporty appears as a good alternative in some interesting sizes and looks quite Motard, though it too is difficult to find in the USA. Through this hunt I kept a record of interesting sites as I was looking for that great tire or buy... and this list became very lengthy

With permission I constructed a new thread and posted it here:
Rims and Tires Reference

Hopefully it will find value for others as well
Cheers, KF