Definitive "The Right Way" Rear Hoop?

[Kodak]

Hey guys,

Hoping to have my build "finished" in time for the Beford Cruise. One part I need to get out of the way is fabricating a rear hoop. I've read many a thread on the criticisms of flat rear hoops, rear hoop clearance for full rear articulation, and overall safety/looks. Does anyone have any design pics/ measurements for a safe compromise for the rear loop when seeking a cafe aesthetic? Anyone interested in bending one up for me?!

 

[Kodak]

I'll bump as I'd really like to get some reliable info or a source for a good hoop before looking on eBay!

 

[clubfed11]

Same here!

 

[ddaniels]

I'm not sure what you're talking about. What's a rear hoop?

 

[Guest]

Your asking the wrong crowd. Best bet would be to go to a cafe forum. Try Dime City Cycles, they may even sell a universal hoop that can be welded in. http://www.dimecitycycles.com

or ebay http://www.ebay.com/itm/like/232006622609?lpid=82&chn=ps&ul_noapp=true
this is a rear hoop.

 

[dorkburger]

There was a member here, DOHCbikes, who was very opinionated on the subject, and the common complaint from him was lack of hoop / tire clearance at full suspension compression, especially on shortened frames with flat hoops where the hoop stops near the top of the tire. Persnally I think there is not really a set way to do it and trial, error and measurement is required.

 

[Guest]

They make them with an up kick for more clearance, but if you running stock sized tires and stock length shocks, I would think you'll have to hit one heck of a bump to bottom out. I guess weight of the rider plays a part also. http://www.ebay.com/itm/230mm-Cafe-...c09866&pid=100677&rk=7&rkt=50&sd=181370996265

 

[Kodak]

This was the member I was thinking of. He appeared to have put some critical thought into it. Universal hoops don't account necessarily for the geometry of the GS850 as opposed to say a CB750. I may end up having to go the universal route with a prefab kick, maybe find a local to bend it more specifically. I will look at other forums but this forum tends to hold a higher caliber with an attention to details that is lost in a lot of cafe forums. If I do say so myself haha!

There was a member here, DOHCbikes, who was very opinionated on the subject, and the common complaint from him was lack of hoop / tire clearance at full suspension compression, especially on shortened frames with flat hoops where the hoop stops near the top of the tire. Persnally I think there is not really a set way to do it and trial, error and measurement is required.

 

[Kodak]

They make them with an up kick for more clearance, but if you running stock sized tires and stock length shocks, I would think you'll have to hit one heck of a bump to bottom out. I guess weight of the rider plays a part also. http://www.ebay.com/itm/230mm-Cafe-...c09866&pid=100677&rk=7&rkt=50&sd=181370996265

So this is pretty much the rear hoop I went with. It's a bit longer so I can cut it down to how long I want it. 20 degree kick. I got paranoid seeing how DOHCbikes mentioned clearance issues that most cafe bikes don't take into consideration and pay for it when they are cornering hard and the tire catches the seat and making an unexpected lower GI release occur or worse! Being a new rider I don't want to take an unnecessary risk that could be avoided by paying attention to past experiences.

 

[hillsy]

As mentioned above, it's pretty much trial and error as different bikes have different seat rail heights and swingarm / suspension travel.

To be certain, take the spring off one of your shocks and then put that shock body back on the bike (by itself) and ratchet strap the rear wheel up as far as it will go. This shows you the maximum possible extent of the suspension travel and where you need to have the hoop to clear the tyre.

There's a lot of "fiery death" talk around the rear wheel touching the hoop, but in all reality, when the rear tyre hits a hoop it tends to bias the weight to the front of the bike and unloads the tyre. Obviously you want this not to happen at all, but your bike wont spontaneously combust or anything like that...

It's different with front clearance though - if the front tyre hits the top triple (like when you slide the forks through the trees) then it continues to push the weight forward locking the wheel and this can be REALLY bad.....

 

[80GS850GBob]

The hoop you need is greatly dependent on what your doing with it.
Said hoop keeps the shock mounts from spreading out - it's your anchor point for the seat {usually} - same for the battery mount if your running a tail piece and/or your anchor point for your tail light.
The hoop usually runs a straight line from the frame - one shouldn't have tire clearance issues unless you've dropped the shock height substantially shorter from stock....even under full compression.
Figure it this way, if your old oem suspension/fender hit the tire under full compression, then keeping a new hoop it where the old frame tail was will wind up with the same problem. I doubt it was ever a problem, so it shouldn't be now. However - to test/check, is to know!
Angled plate...well, set that per clearance under compression or put the plate on the side of the frame {ugly that way but paint your canvas your way}.

My advice - tack on the hoop....measure the static frame height from the ground then remove the shocks and see how far the frame drops till the hoop hits...there's your drop limit. {a friend helping with this would be a good idea} Adjust the hoop {in/out/up/down or curve the rear top of the hoop} as needed. Retry the frame drop until your clearance is good for you. Attach shocks again knowing your clearance is good and worry about other things....

 

[80GS850GBob]

Having thought about this for 5min...how about an easier way...sort of.
Find out what the actual shock compression/bottoming is...3"-4" inches?....find on your current frame when the hoop will cross over the rear tire and measure your clearance to the top of the tire....see what any difference is. Then you'll know if your safe or short.
Hardest part is finding the bottoming spec for the shocks.... 6 of one....1/2 dozen of the other, I guess.

 

[Kodak]

As mentioned above, it's pretty much trial and error as different bikes have different seat rail heights and swingarm / suspension travel.

To be certain, take the spring off one of your shocks and then put that shock body back on the bike (by itself) and ratchet strap the rear wheel up as far as it will go. This shows you the maximum possible extent of the suspension travel and where you need to have the hoop to clear the tyre.

There's a lot of "fiery death" talk around the rear wheel touching the hoop, but in all reality, when the rear tyre hits a hoop it tends to bias the weight to the front of the bike and unloads the tyre. Obviously you want this not to happen at all, but your bike wont spontaneously combust or anything like that...

It's different with front clearance though - if the front tyre hits the top triple (like when you slide the forks through the trees) then it continues to push the weight forward locking the wheel and this can be REALLY bad.....

appreciate that post a lot. Makes me feel better. Going to try that out. See how much I need to compensate for near full travel. I'm fairly tall but not heavy, under 200. Going to do my best not to ride the ****a out of my bike until I've developed the appropriate competentancy to ride hard. Well at least that's a tentative goal.

 

[80GS850GBob]

LOL...I just noticed this....is the bike in your description the bike in question for "hooping"? I might know about those particular cycles....

 

[80GS850GBob]

"Going to do my best not to ride the ****a out of my bike until I've developed the appropriate competentancy to ride hard."

1- only time and riding aids in getting the feel of your cycle...each one has her own characteristics...850's are heavy and feel a tad top heavy to boot {but nothing outrageous or no one would ride them}
2- "riding hard"...if your thinking of carving corners like the modern bikes...this might not be the best subject to try it on. These old girls aren't incapable, but they lack the lightness {or easy flickablilty}, fatter tires and ground clearance that others would better offer...they were designed for long touring.{in other words built and nearly weigh like a brick sh%# house}
3- if a visual statement is really what your after, she'll do it. But much more after that I'd honestly refer you to statement #2 above.

...{4-lol...I'm racking my brain to come up with the 5 letter bad word ending in "a"}

 

[Guest]

There's a lot of "fiery death" talk around the rear wheel touching the hoop, but in all reality, when the rear tyre hits a hoop it tends to bias the weight to the front of the bike and unloads the tyre. Obviously you want this not to happen at all, but your bike wont spontaneously combust or anything like that...

To add to the no doom talk, MX racers will sometimes modify the rear subframe to suit short riders and end up with the rear tire jamming into the fender on big jump landings. This does not cause crashes and is just ignored as the consequence of making the bike fit the rider better. The second thing to realize is that the only way you will hit the hoop with the tire is by bottoming heavily on a large bump. This is an instantaneous condition that goes away immediately as the suspension rebounds. If it slows the wheel at all it is a momentary burp and then the wheel is clear again and will keep rotating just fine.

As you say, you don't want it to happen, but it shouldn't be the end of the world, either.

Going to do my best not to ride the ****a out of my bike until I've developed the appropriate competentancy to ride hard.

No offense, but as a new rider you won't be capable of riding the sh!t out of your bike for some time. You may well exceed your personal limits (this happens all the time and is the cause of a large majority of crashes) but you won't be overriding what the bike is capable of.


Mark