Front Steel Suspension Fork

S

SunCoaster

100 W
Joined
Nov 13, 2009
Messages
174
Location
Lake Oswego, Oregon
If anyone is looking for an inexpensive steel suspension fork, Choppers U.S., LLC has offered this fork, (now temporarily out of stock):

http://www.choppersus.com/store/product/996/Fork-Suspension-26%22-Silver/

The one I received has the model # SFM 2025S listed on the box and # FLC159-13 listed on the fork; I've searched, but couldn't find a direct product web page.

The fork weighs ~ 5lb.

I might try a low power hub on it with torque arms.
 
Excellent find dude! Often these front hub freindly steel suspension forks are only found in 1" headset. This one is 1 1/8 ! Perfect for the guy who wants a bit of help with the bumps and front hub.

The 1" ones are easy to find, just buy a broken bike cheap at the garage sale. But the steel fork in 1 1/8 " took me two years of hunting at the flea market to find.

Under 1000 watts, I ran motors on this type of forks with no torque arms for 5500 miles no problems. They have the really beefy dropouts. Just keep the nuts good and tight and you are good to go with just torque washers.
 
auraslip said:
It doesn't say on the website if they are steel.

Or am I blind. I couldn't find them the sontour website either.
Click to expand...

I don't see it mentioned either. However, the dropouts kinda look like pinched tube steel. Hard to tell with that little photo.

Here's the black model:
http://www.choppersus.com/store/product/995/Fork-Suspension-26%22-Black/
 
Thats the new one I've seen on the bikes down at Target now.
 
$59,,,,, steel. I'd say about 99% sure of that. $75,,,,, could be alloy. Anything of the pinched tube design is definitely steel.

Sometimes though, you have issues with hubmotors fitting between the tubes on steel forks. Wider ones like gearmotors and BD36 may rub on the tube. Fortunately the tubes can be pinched a bit more to make room on the cheaper steel forks. All the working parts are further up the tube.

Be nice if you could get the steel forks in 80 mm travel, most are only 40 mm. But 40 mm beats no mm.
 
DervAtl said:
auraslip said:
It doesn't say on the website if they are steel.

Or am I blind. I couldn't find them the sontour website either.
Click to expand...

I don't see it mentioned either. However, the dropouts kinda look like pinched tube steel. Hard to tell with that little photo.

Here's the black model:
http://www.choppersus.com/store/product/995/Fork-Suspension-26%22-Black/
Click to expand...

The one I've seen wasn't pinched steel.
 
If you have more time than money, craigslist for a bike with those. I picked up a $50 diamondback that had a 1 1/8" suntour steel suspension fork.
 
Part # RST-191 (from another thread), 1-1/8" steer tube, steel dropouts, allows both V-brakes and/or disc, etc....

770613_1.jpg
 
So how do you know if you have a 1" or 1 1/8" headset? I can measure but I was wondering if certain types of bikes had a certain size.
 
If it's a really cheap bike 99% sure it's 1" for starters. If it has threadless headset, remove the top cap, and you can see the steer tube and measure it. If it has the threaded headset measure the stem that sticks out of the big nut on the top of the frame. On 1 1/8" the stem will measure 15/16, nearly an inch. The 1" stem will be just a bit over 3/4 inch diameter.
 
I know RST makes steel entry level suspension forks but small inch head set. I had my GM on one and it rode great.

PLEASE PLEASE PLEASE!!!! make sure that the fork is steel and not magnesium. When i bought my bike I did the magnet test and a magnet stuck to it although it was a very weak attraction. There was something steel in the fork but the drop outs were magnesium. I had a Suntour fork similar to that one and it formed a hairline crack on mine running a motor at 60v. Turned out it had completely snapped and the bolt was just holding it all together.
http://endless-sphere.com/forums/viewtopic.php?f=3&t=10960&p=167914&hilit=icecube57+magnesium#p168004
 
Musta been a good magnet! It was attracting to the steel inner tube inside the fork. I use a cheaper magnet, one of those rubber sheet ones that can carry in my wallet. It's not going to be strong enough to attract through anything , even a buisness card would make it fail.

That's a new one I never thought about, some of those neomydium fridge magnets these days for hanging notes or photos are really strong.

A few other things that are tipoffs. Consider this as close as you get to a compatible fork post. Steel = compatible in general, but always each motor and each fork may have some issue with clearance. Some forks can take one motor and not another. 9c is the narrowest hub I've seen, fits nearly all forks. A 5304 is a fattie, and won't fit narrow forks.

If the fork looks like a tube that was pinched flat on the end for the dropout, definitely steel. Typical of the cheapest bikes.

Next up, a welded on dropout. Often these are also steel, and the welding looks like steel welding. Look at steel frame bikes, and aluminum frame bikes and you'll see it. The bead on the aluminum weld is huge, so if the fork welds look fine, 99% likely to be steel.

Now the alloy forks. The dropouts may be welded on, but anything that looks like a one piece casting, or machined shapes is going to be alloy. I have not seen fork lowers that were steel that werent welded. Even the pinched tube steel forks have a welded on horseshoe on top. Fancy shapes cast in place for disk brakes etc are going to be alloy for sure. In alloy forks, some can fit a motor and some can't. Some can fit one motor and not another.

Ebikes ca has the stuff you need to run motors on alloy forks. Two very good torque arms and the c washers are what you need. See the review section for details. So far so good for my alloy forks, but I am not stupid enough to run 2000 watts on a front alloy fork. Just 1000, 48v 22 amps. Justin thinks many of the alloy fork failures are from improper size washers for the cups molded into the forks, so that is what the c washers are for. The few remaining fork failures should be covered by using two good torque arms. Of course, keep the nuts tight, 90% of cases of loosening nuts is due to improper fitting of washers. Sometimes you gotta grind a corner off em.
 
How would somebody know if a drop-out was magnesium instead of steel...if a magnet is "somewhat" attracted to it?
Click to expand...
Two tricks I found to check for Steel/Iron (ferrous metals).
#1- suspend a small magnet riggeds on a long string (like a plumb-bob is held) and then hold it nearer to the object to be tested. It will swing slightly to the metal if iron is present, or unfortunately if an iron object is embedded in it.
#2- a very clean file used to scratch some filings off the piece to be tested (inconspicuous place) , sprinkle them on a white paper card, see if a magnet picks em' up.
 
When I was looking at used bikes a few months ago, I also noticed that my magnet was attracted to some of the magnesium drop outs. Knowing this is impossible, I dropped the front wheel out and retested. No attraction. Turns out it was attracted to the steel axle running through the center of the drop out and I was getting a little too close.
 
I noticed that too. I did the same thing. The axel was steel... the drop outs were magnesium... and something still was inside the fork shaft its self that was causing the magnet to stick but it was a real weak attraction. The magnet i was using was one from an old hub motor so i know it was strong.
 
:mrgreen: Yeah, an old hubmotor magnet woud stick to steel rebar imbedded in a concrete wall I bet. :twisted: That's a really really strong magnet!

My magnet test, using the rubber sheet magnets typical of a fridge magnet buisness card don't stick to the alloy forks at all. Only barely stick to steel.

See the reviews and testing sections for how I went about fitting a 1000 watt at 48v hub on alloy forks. The key item is the Ebikes-ca c washer, or similar washer that you grind yourself out of the typical torque washer in most kits, or make out of split washer type lock washers. The thing is, any tiny gaps behind the washer will put leverage on the dropouts, cracking them. Or the washer will slowly deform allowing the nut some space that reduces it's grab on the forks.( see the Fork tests thread from Justin too!) Once the nut gets loose, spinout happens. This applies to steel dropouts too, front or rear. In ALL cases the washers need to fit, and if not, be modified. You also have to look at the motor axle, too small a shoulder on it could spread dropouts. 9c motors have that, mine has inner washers to prevent it. Once you get good fitting washers, then a good set of tourque arms are the insurance. Two of em not only helps prevent spinout even if the nuts get loose, but more importantly, they keep the wheel on the bike if the bad thing happens. Forks are only a tool, no fun to pay for broken ones, but not breaking bones and teeth is worth the 50 bucks a pair of really good tourqe arms costs.

At this point though, I'd still be really uncomfortable running more than 48v 22 amps on alloy forks. But two good tourqe arms will keep the wheel on the bike if you put a 72v x5 motor up front. That much power, I'd want on the rear for other reasons anyway. I think 2000 watts on the front wheel would just grind up tires.
 
Even the Fusin 36V motor will spin a little on the front if I have it in the medium switch position sometimes, starting up from dead stop. :)
 
Yeah, tourquey little thing aint it? Lotsa folks have had forks trashed by little gearmotors that have huge tourqe. My 9c at 36v will spin the wheel a bit on starts, and at 48v it can spin a full revolution before taking off. Thats 1000 watts. No big deal for me, but it can scare a guy with low motorcycle experience. But it would be a shame to have 2 or 3 thousand watts on a wheel and have to always pedal first eh? So the rear would make sense for that, putting more weight on the rubber.
 
Here is the pro way to find a RST-191 fork:

http://www.google.com/search?hl=en&client=firefox-a&hs=5Xq&rls=org.mozilla%3Aen-US%3Aofficial&q=site%3Awww.bikepedia.com+rst-191&aq=f&aqi=&aql=&oq=&gs_rfai=

Then search each one of those bikes until you find one on craigslist for super cheap;.
 
On second though after reading the reviews of the RST-191, I don't even know if it's worth the time or money to install.

However most of the reviews are from mtn. riders. Using it for street riding might garner better reviews.
 
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