Need Advice For Switching An X5 Into A 20" Wheel

I'm interested in re-lacing my X5 into a 20" from a 24" wheel. I never operate the bike near it's 44mph top speed, and I am looking for better acceleration and hill climbing power.

To do that, I need solutions to the following problems:

1) Pedal Clearance
The pedals might just barely clear the ground, but turning will probably cause dragging. It seems I'd need a new, shorter crank designed for my bike's 3 front gears. Suggestions on ones that would work? Would I need to pull the bottom bracket to install it? Would I need a new bottom bracket too?

2) Wheel
Suggestions for a sturdy, double wall 20" wheel? I plan to use a 20" hookworm or similar tire.

3) Anything else I'm missing?

This is the bike:
http://www.amazon.com/Cadillac-Adventure-Suspension-Comfort-17-Inch/dp/B000FW2C04/ref=pd_sim_sg_1_img/105-4484028-5962002

At ~3.5" pedal clearance looks like it might be OK with a 20" wheel which should decrease clearance by ~2", correct?

hey Xy,

i would use the crank you have - it is relatively easy to have it shortened and re-tapped,from memory i think you need 9/16" taps but you need a left and right hand tap - i bought these as a set for around £25 and are available from most lbs's.you dont need to change the bottom bracket but you may need a crank extraction tool.
the rim should be no problem either, look at bmx rims as they take a good bashing and most are double walled anyway - i went for gusset black dogs which were £17 each,pretty good.
tyres i found were a little harder to find but then i needed dirt tyres so you may be ok.
it should make for a much torqueier? bike though - will look forward to it it you go for it.


Cheers


D


edit - 3.5" wont be enough mate, look at my old pics, you will catch the pedal no end,with a 20" wheel you'll only have 1.5"!! - dont forget if you shorten the crank it will affect your gearing also so you need to know that the granny gear you have now will still be ok if your crank is shorter - my crank shortened gives me 5" clearence but in hindsight i could have got away with 4" - id say thats your target ?

Thanks, D. Do bike shops do this re-tapping? I don't suppose I can just drill un-threaded holes and then hack-off the ends...? So is the tap like a threaded piece you buy and install in the newly drilled holes?

Yah, torque monster! I was playing with the hubmotor simulator -- going from a 24" to a 20" wheel provides the same extra thrust that raising the voltage from 72v to 96v does! And motor efficiency at most speeds improve by 5% too.

So of course I'm looking to do both, with a 24v emoli or A123 boost pack, and the 60amp controller mod

At it's present 72v35a, top speed with a 20" wheel should be about 35mph. Still plenty fast for me. I just want to climb walls, that's all.

Bravo X !!! Join the small wheel club !

You have a short rear shock.. swap that sucker out with a longer unit and you regain your ground clearance.

That or have a metal shop cut and re-weld the crank arms shorter ( to avoid the drill and tap problem ) ...

Rims are easy to find, Spokes can be a bugger.. PM me if you need a set of 12 gauge one's.

Ypedal said:

Bravo X !!! Join the small wheel club !

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Oh yeah! There's just so many disadvantages to even a 24" wheel on a fast-spinning hubmotor, and no major advantages.

You have a short rear shock.. swap that sucker out with a longer unit and you regain your ground clearance.

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Oooh, I like that idea much better than shortening my crank. Do you have any links or suggestions of good shocks I could buy and bolt-on myself?

That or have a metal shop cut and re-weld the crank arms shorter ( to avoid the drill and tap problem ) ...

Click to expand...

This is my exercise/pedal bike too, so I'm not very hip to shortening my crank.

Rims are easy to find, Spokes can be a bugger.. PM me if you need a set of 12 gauge one's.

Click to expand...

Thanks! Do you or anyone know anything about these 20" rims that the poweridestore sells? Any reason they wouldn't work with a 20" Hookworm tire, or my hubmotor?
http://www.poweridestore.com/Rims/Double-Wall-Rims

They also sell 12 gauge and 13 gauge spokes in 20" lengths.
http://www.poweridestore.com/13-Gauge-Spokes

I use 13 gauge spokes right now so I figure they'll be fine for a 20" wheel laced radially.

xy,

looks like you may go the other route - im not sure how much you could extend using a replacement shock (may shorten wheelbase/alter handling?) but worth looking into especially as you could improve the rear suspension at the same time.
a tap is a thread cutter - you drill the hole then run the tap through it to cut the thread - it's like a self tapping screw cuts its own thread on the way in.
if you decide to cut and tap don't piss about yourself.you need a machine shop with mill/lathes etc.on the upside they can do it in about an hour and it wont cost much.personally im totally against the "cut and shut" approach,if they are slightly out at the join you will really feel it wobble in the pedal - with drill and tap the crank arm is jigged in the milling machine and comes out dead true,mine pedals dead straight
heres a link for the taps - http://www.bonthronebikes.co.uk/330-2966?a=2966
you need both to tap both sides as the left pedal has a left thread (sorry if you know this).i had the guy drill,tap,and then cut of the excess and round off.

9/16 is the size and they would need to drill 1/2" then tap them through.

like i say mate - look into the rear suss option but if you want to shorten use a machinist to do it unless you have the workshop to ensure true drilling and tapping.

if you do shorten them be warned you will feel the difference, i dont pedal much at all, only when im going up really steep hills and to get home should my kit fail so mine are perfect but if you excersise on your bike you may not like the smaller stroke - as ever with ebikes built for purpose i suppose.


cheers


D

If you can remove one of the bolts that holds the rear shock, try to pivot the swingarm to make sure the pivot point will allow you to extend the shock enough ( some frames won't let you do this without some serious mods.. some just swing down.. )

Earl's Double walled rims : Send him an email and ask if they are the " Narrow DeepV type or the Wide Flat surface types "

You DO NOT want the Deep-V on an X5.. i had one and it bends at the seam.. i have some of the wide Crystalyte one's ( 33mm ID, 38mm OD ) those are much better and would be prefect.

I suggest a new set of spokes while you are at it.. used spokes will have bent and warped, and have seated on the current angle used... get new spokes.

I'm currently running one of the new offset 5304s with a 24" rim, and a 24x1.85" Maxxis Holy Roller. Pick up off the line is much improved over the 503, but top speed suffers of course. No load speed is 105km/h at 105v, and so far top speed on the flats is 81-82km/h @ 88v. Above 65-70km/h the power really drops off, and I think this setup needs a bit more voltage.

Efficiency seems improved over all, but I still have to do some proper 2 way Wh/km measurements. On the way home from work yesterday, I reset the CA at the start of a 6km straight stretch of road. At an average speed of 76km/h, the CA showed 28.4Wh/km.

Is there any importance difference between 20" BMX tires and 20" recumbent tires? I'm looking at Maxxis hookworms listed in the BMX section, but there's also some good-looking 20" tires in the recumbent section.

Is one usually an "ISO 406" standard and the other the ISO 451 standard?
http://www.sheldonbrown.com/tire-sizing.html

Which standard, 406 or 451, does crystalyte use for their 20" wheels?


Thanks.

I'm holding a rim right now that has ID 33mm from inside flange to inside flange where the tire bead seats..

Measuring the diameter, a 406mm tire bead would be just right.

On my Norco:
I'm using a " Revenge Industries " Kevlar belt tire from the BMX tire rack at the local bike shop right now. 100 psi rated tire inflated to 65. And a FMF Powermoto rim, with 13 gauge spokes.

If that helps any.

Ok, thanks Ypedal. Is that rim you measured one sold by Crystalyte?

And yet another issue: spoking pattern. Is radially the only way to lace an x5 into a 20" wheel?

Sheldon Brown has this to say about radial lacing -- but it may not apply here since the hub is of much greater diameter and strength, and the spokes much shorter:

http://www.sheldonbrown.com/wheelbuild.html
"Wheels with hub brakes and drive wheels should never be radially spoked. Due to the near perpendicular angle of the spoke to the hub's tangent, any torque applied at the hub of a radial spoked wheel will result in a very great increase in spoke tension, almost certainly causing hub or spoke failure."

Here is a list of the spoke lenghts i got from crystalyte :

5X motor and 20â€￾ rim = 77 mm
5X motor and 24â€￾ rim = 138 mm
5X motor and 26â€￾ rim = 165 mm


4X motor and 16â€￾ rim = 57 mm
4X motor and 20â€￾ rim = 106 mm
4X motor and 24â€￾ rim = 165 mm
4X motor and 26â€￾ rim = 190 mm
4X motor and 700c rim = 218 mm

Spoke sets are all the same lenght, so no allowance for dishing.

yes, the 33mm rim is crystalyte stock, but there are different sizes available.. i requested the widest available. 25 and/or 27's are possible i beleive, not 100 % sure on that one.

That is a beautiful bicycle

Radial should be ok. I see a lot of small scooter wheels radially laced.

Spoke sets are all the same lenght, so no allowance for dishing.

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Hmmm....what happens if I can't dish the wheel? Would I be able to tell it's not dished? With its 3-speed freewheel, I only need about an inch or less of dish...can I skip the dish? Or would skipping the dish skiff me into the ditch?

Johnbear said:

That is a beautiful bicycle

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That was a beautiful bike. Now it's an ugly, odd duck that works much better and is a lot more funner.

With a 3 speed it should not be a problem, I've had requests for 9 speed clusters .. not that's pushing it.

The spokes have a 10mm range of usable threads.

Big factor on dishing is usually the Brakes !, but since you don't have a rear brake this is not really a problem. As long as both your wheels track paralell you will roll in a straight line. I only like to roll down ditches on purpose !

Thank you for all the help so far -- I'm almost ready to downsize my wheel now.

One issue remains: a longer shock absorber for my soft-tail.

Does anyone have any specific recommendations, or at least good sources for bike shocks in general?

Also, it's not immediately obvious to me how to remove the end of the shock nearest the wheel...?

Might have to do some trig to figure out the best length -- by eyeball it looks like I need a 2-4" longer shock to raise the rear 1-2".

Note: the wound on my left middle finger from when I drilled into my knuckle is almost healed. So far, the workshop has been more dangerous than the road. Good thing I was wearing my helmet. :wink:

Shocks that work with soft-tails aren't easy to find.

http://forums.mtbr.com/showthread.php?t=318238

MTBR Forum said:

Any sources for Soft Tail shocks?
5" length, one eye on end only? I can find zero so far. Let me elaborate. Salsa has what looks like a winner on their 29"er...they tell me they don't sell it...and it's a RockShox MC3. Fine, except Rock Shox only lists a 6.5" as the smallest size, and it has eye holes on both ends. I ask the guy at Salsa "what about someone who needs a replacement down the road?"...haven't heard back on that one....

So, I'm asking the knowledgeable bike geeks out here in mtbr land if they've seen one.
---------------------------------------------
Check DT Swiss and their ssd line. They specced of currently spec a short travel shock for the Scalpal.

You will not likely find one aftermarket, however. You will likely not find one used, either, as any frame problems will go back to Cannondale under their lifetime warranty.

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I didn't find any either, and judging by the price of full-suspension shocks, any of those possibilities mentioned above probably costs hundreds of bucks.

I think I'll go ahead and try the bike with 1.5" ground clearance. If I find I'm often scraping, I'll extend the length of my stock shock with some sort of simple, non-compressible wood or metal apparatus.

Try looking for an old Fox DHX 5.0.

http://www.mtbr.com/reviews/Rear_Shock/product_124492.shtml

Bigger front wheel?

Would be worth making any extension to the shock solidly mounted (i.e. not swivelable) to the frame, otherwise it could 'jackknife'.

maxwell said:

Bigger front wheel?

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Don't thinks that's feasible. The front is already 26". The rim brakes won't work with a larger wheel; there may not be sufficient clearance from the frame; and even if I could fit a 28" front wheel, that probably wouldn't raise the pedals more than half-an-inch. Besides, with a 26" front and 20" rear, the bike is already going to look pretty weird (in a good way, I hope!).

Would be worth making any extension to the shock solidly mounted (i.e. not swivelable) to the frame, otherwise it could 'jackknife'.

Click to expand...

Good idea. I was thinking the same thing. Basically, I'll design something simple that acts a straight-line extension to the bike-side end of the stock shock; and also cut it and brace it in the frame mount so that it'll act like an extended frame mount. In other words, the extension will be fixed against any rotation on both ends. Since the extension will only need to be a few inches, and I don't have much in the way of metal working tools, I may just craft it from a block of pressure-treated wood, using lots of transverse bolts to make double-sure the wood won't crack.

Hi Xyster
Any chance you can post a photo of the bottom half of the shock so we can see how it's mounted? Looks from your last photo as if it's welded to the swing arm, but I'm sure that's not right.

NO WOOD !!!! please...

My god man.. you got a death wish ? :lol: oy..

That rear shock is very strange, the bottom mount is not usual at all.. how does the shock bolt to the swingarm part ? or does it just sit in that cup ?