best shock type for rear hubs?

jimmyhackers

10 kW
Joined
May 11, 2015
Messages
600
i have a 20" and 26" hub motored bikes. 1000w hub motors.
both have cheap rear spring suspension (no dampening).
the smaller one is more offroady, and the larger bike is on roads only.

i have ordered an A5 rear air shock for the 20" EMBX thing for testing..

then i realised i should of asked on here first :S.

whats best for a heavyish rear hub, proper spring coils with dampening or air shocks?
 
I don't think you are asking the right question.
Any "control" of a hub motor will be a function of the rebound damping for unsprung weight, not so much the compression damping and bicycle shocks are not designed the deal w/ the extra weight of the motor in rebound.
Having said that, I would think a name brand like Fox or Roxshox would offer more rebound adjustment than a KS or DNM, so it becomes more a matter of what do you want to spend for something that may, or may not be so noticeable on a street Ebike.
Whatever the dynamics at work, the Fox and Rockshox units that come on the higher end mountain bikes I have used have worked remarkably well in conjunction with my 2 Kg. to 5 Kg. motors. They are easy to adjust, have been reliable and deffinately take the sting out of hard hits. But they have all been air shocks, so I can't really make a direct comparison of air to spring.
But I can when it comes to dirt bikes and my opinion is at the lower cost range, the air shocks feel more progressive and controlled. The spring units feel more bouncy unless lot's of rebound is dialed in, and that starts to hurt overall performance. I suspect as one goes higher in quality, the difference becomes less.
Somaybe the the question could be framed, "Are the name brands, worth spending the extra $$ over the Chinese brands?"
I would think, that if the Chinese units will work without the seals leaking, the difference would be sm. on a street ebike, hub motor or no hub motor.
Slow leaking when parked is, of course, the downside to air shocks. Even my new Rockshox needs to be pumped up a bit if it has sat overnight. Out of the several units I have had, only one Fox Float R didn't leak while sitting. In general, this is NBD, I just top off the shock while topping off the batt. And since I'm going to give my legs a workout, I might as well give my arms one too :D
 
Motomech is spot-on regarding unsprung weight problems with hub motor.
My solution: I went fat!
Rims built with fat-tire divorces heavy motor's weight issues during rebound/compression.
Fat tire effectively gives you about 3 inches of travel for the small "rattly" bumps.
I run 5PSI off road which eats up the small bumps.
Larger bumps and dips/whoops are handled fine with budget air shock. Dont waste money on one of the premier vendors' shock IMO because it is not engineered for heavy hub motors.

Caveat: This works well for my riding: bumpy/rutted roads with much loose sand sections. For pack single-track may not be a good fit for faster runs. Low-air tires absorb terrain very well, but they will "roll" when under lateral stresses and will wash-out.
 
I agree with pullin-gs’s and also believe a good sized tire is key as well. I run motorcycle tires with my QS205 in the 17x 3.00 size. I personally believe that the 18” with a 3.50 is the perfect mix of tire for the 205, 260 and 273 motors. Just wasn’t available when I built my bike. I run my tire at about 15 psi and it’s soft, very soft on pretty much all surfaces. I use the Shinko 241 tire and after maybe 5k miles still looks relatively new. I couldn’t recommend enough to anyone on the fence. I like coil spring shocks because you always have the same feel but mine does have an air chamber to add air to if I’m going to get aggressive off road. What ever you get make sure it has both high speed & low speed compression with rebound dampening.

Tom
 

Attachments

  • C0886C07-40BD-4EE6-AE26-E468FA60524D.jpeg
    C0886C07-40BD-4EE6-AE26-E468FA60524D.jpeg
    145.9 KB · Views: 367
jimmyhackers said:
whats best for a heavyish rear hub, proper spring coils with dampening or air shocks?
Proper spring coils offer superior suspension performance to air shocks -- not just on a heavish rear hub, but on any hub.
Air shocks are only used for weight and cost reasons.
 
The operative word here on what he has now is cheap. Better shock, of either type, will be,,,, wait for it,,,, Better.

In general, he just needs a better shock of any type. I came to like my air rear shock simply because I could stiffen it up more than the spring shocks I have. Both were decent shocks, nothing spectacular, just better than a pogo stick from a BSO. Both needed increased pre load to handle the heavier motor wheel. Both had plenty of rebound adjustment. Both were superior to a shock that has no oil, no rebound adjustment at all, and a weak spring.
 
thansk for the replies, a5 air shock came today. put it on the ebmx

its ok, it is a lot stiffer than my old one....my backsides not really enjoying that.
i was kinda hoping for a softer start to the compression with it progressivly getting stiffer towards the end.
with the aim of a more comfortable general ride without the short 125mm suspension bottoming out on the bigger ruts/bumps.
at least its not bottoming out anymore.

i can let some air out but im waiting till i have a proper shock pump incase i let too much out.
 
lol, pump arrived.

i let some air out. they were at 110psi they are now at 90.
softer than before but i can feel little to no difference between these air shocks and the cheap coils.

whilst looking at the A5 specs my 125mm model only has 20mm of travel. im not sure if this is the same or less than my 125mm coil.
i suppose thats also why i can feel little progression in the stiffness over the short travel.

im thinking my only other option would be to redo one of the rear mount points to accomodate a longer shock for more travel.
i can probably get away with a 180 or 190mm. for a full 50cm of travel.
 
jimmy, did you consider a seat post with spring or shock to absorb some of the bounce?
 
fatty said:
Proper spring coils offer superior suspension performance to air shocks -- not just on a heavish rear hub, but on any hub.
Air shocks are only used for weight and cost reasons.

When was the last time you looked for rear shocks? even the most high end ones typically use air, and are also the most expensive type.

I've had a lot of bikes with spring suspension in the rear or front. Even a cheap air shock performs dramatically better.

High end shocks always use a combination of spring and air/oil.

You'll never ever see a high performance vehicle of any type using coils alone. Because a high performance suspension always includes a mechanism for damping.
 
Back to OP's question.
A heavy hub motor will always make any type of suspension you put on the bike perform poorly due to the extreme amount of unsprung weight. Very expensive rear suspension can help counter this, but it's impossible for a bike to have the floaty feel it should with a hub motor.

QS hub motors are the heaviest hub motors per continuous watt on the market because they use cheaper metals and really overdo it on the copper fill. These are cheap motorcycle hub designs adapted to bicycle axles. You can buy 18lb 2.5kw rated hubs all day and their rating increases to 3kw continuous in a 20" wheel. An equivalent QS motor weighs 24lbs... but cooling mods on the 18lbs motor would make it more capable than the QS without mods.

I suggest getting the lightest possible motor that meets your requirements over spending a lot of money on suspension.
 
neptronix said:
When was the last time you looked for rear shocks? even the most high end ones typically use air, and are also the most expensive type.

I've had a lot of bikes with spring suspension in the rear or front. Even a cheap air shock performs dramatically better.

High end shocks always use a combination of spring and air/oil.

You'll never ever see a high performance vehicle of any type using coils alone. Because a high performance suspension always includes a mechanism for damping.

Coil spring over damper, obviously -- not an undamped spring. Damping is a given.
Coilovers, as used in every performance suspension for non-HPVs counting individual grams. And even used there where suspension performance dictates.
 
i suppose this is more for comfort than performance now i think of it.

im not sam pilgrim. biggest jump/ramp id take the bmx thing off is a 3 footer if that.

i did put a seat post suspension on my other hardtail non ebike. i suppose i could get another for this, but more weight/cost.

a fatter rear tyre would help also. is currently 1.95 profile. so like 2.2 to 2.3 would help.

the existing seat is also rather lacking. i could fit a more padded one.

a longer shock is an option but it means frame welding and more money. also means im more likely to bottom out on my pedals with the extended travel.

i think ill go with a bigger tyre and softer seat for the moment, plus some padded shorts ive ordered.

im still kindof stuck with what to do with the bigger road bike now. i feel like i wont get much noticeable improvement unless i get something pricey, so im probably best leaving it as is. unless you guys have some suggestions for a good 150mm shock?
 
Back
Top