|Will the roller stand damage the fork?||Chunky|
Oct 7, 2002 8:39 AM
|I've been eyeing the Kreitler stand so I can afford to "space out" a little on the roller without risking the carpet burn. Can't find review on the stand. Does anyone have experience w/ this product or information whether it's safe for the fork? Thanks.|
|Yes, forks are not designed or engineered for those stresses.||MB1|
Oct 7, 2002 8:43 AM
|That being said, a cheap steel fork is your best bet.|
Oct 7, 2002 10:06 AM
|I put a roller stand on every once in awhile. I'm not sure what particular stresses would be different. The rear tire moves back and forth as does the frame, but this motion would be taken up in the headset. As long as you don't rock the whole assembly I don't see where the problem would be. For hammering indoors, I use a rear wheel mag trainer. Rollers for spinning.|
|The fork blades are the problem.||MB1|
Oct 7, 2002 12:24 PM
|On the road your front wheel floats as the rear wheel moves around-this pretty much puts no stress on the weld/bond of the fork tips to the blades.
Locked into a fork stand the attachment of the fork blades to the tips can be weakened as the rear wheel moves around in the rollers. This does not happen in a rear wheel trainer if you leave the front wheel in or as you ride rollers normally.
Of course this failure will not occur untill you are back on the road and hit a bump on a screaming downhill.....
Oct 7, 2002 2:46 PM
|It's a darn good thing you *never* hit any bumps in the road at say 50 mph or have to bunny hop the bike with a 200 pound rider year after year mile after mile under racing conditions - - - b/c everyone knows that the forks aren't designed to take that kind of load. ;-) Yep, those forks are right at the design limit and just ready to fail the moment you put them into the fork stand - why just look at the thousands and thousands of senseless deaths and people that have been maimed as a result. Why Ralph Nader has made his entire reputation on suing fork and stand manufacturers - and you thought "Unsafe at Any Speed" was all about cars..... |
Got ANY data to back up your position or you going to just continue to spew?
|When I worked at GT we did a bunch of destruction tests.||MB1|
Oct 7, 2002 3:35 PM
|I spent 10 years in GT manufacturing management. GT made very few forks, we bought them from Taiwan-as most of the bike industry does. The liability insurance was crazy.
Forks would usually fail at or near the crown (before unicrown forks) if they were held in a hub type clamp that was allowed to float on a ramp and repeatative forces were applied from above as if a rider was on a bike hitting bumps. Bending often preceded the failure by a few cycles.
Forks failed much, much sooner and at the tips if they were locked in place and not allowed to float on a ramp (such as in a fork holder for rollers). The differences were striking. As I recall the failures often came without warning when the tips separated.
I have no idea where the data is now that GT is bankrupt it was certainly never released to the public.
For what it is worth I would have no problem riding a bike thet had been used in a rear wheel trainer or on rollers. I very much doubt that a steel fork would have a problem being held in a roller support. I would not feel comfortable doing it to an aluminum fork or a light carbon fork.
|sounds more like data than spew to me :-) nm||DougSloan|
Oct 7, 2002 6:55 PM
|Bicycles are fascinating structures, so strong-so fragile.||MB1|
Oct 8, 2002 5:05 AM
|Grzy has a very legitimate point in that bicycles and forks survive very large load forces all the time. My point is that they are designed and manufactured to withstand those very forces and yet think how easy it is to dent a top tube (a minor design consideration) for instance.
Forks are not designed to be clamped into place and twisted (this is what happenes in a fork stand on rollers as you apply force to the handlebars). Sure there is a very large safety margin in the materials used in a fork to allow for this sort of abuse (in a design sense) but is it wise? In my opinion no, this is not a good use for aluminum or carbon fiber forks.
There is a wonderful book To Engineer Is Human: The Role of Failure in Successful Design by Henry Petroski. (Read everything the man writes-well worth your time). The main point in the book is that over time a successful design is modified for cost and weight until it starts to fail-then the design pendulum swings in the other direction for a while. I believe that the bicycle industry is going down this road right now with its' emphasis on light weight and performance at the expense of durability.
Oct 8, 2002 3:28 PM
|Well, I guess it's a darn good thing that GT is out of business and that there is an alternative to buying crappy low-end forks from Taiwan made at slave wages and with non-existent quality control. What you pay for is what you get. |
BTW - Where are all of the maimed and injured riders from these catastrauphic failures - and how come they're not suing or even speaking up?
|LOL ok, do it.||MB1|
Oct 8, 2002 3:57 PM
|Man asks a question about how we feel about fork holders.
You strongly object.
I expand on my experiences.
You strongly object.
O.K. clamp your carbon or aluminum fork in a holder and ride hard.
Have a nice day.
|I'd bet that most manufacturer's warr would cover that, but||Ken of Fresno|
Oct 8, 2002 4:08 AM
|I guess you wouldn't want to need to file a claim while going downhill at 60 mph. :o
I guess it's a good reason to have a beater bike with a steel fork for trainer use.
Thanks for the heads up,
|Remember if it breaks, "I was just riding along..." nm||DougSloan|
Oct 8, 2002 4:18 PM
|Grzy, you know, MB1 has a bit more class than to take notice||bill|
Oct 8, 2002 7:09 AM
|of the personal grzy touch, but, "just continue to spew"?!!! Come on. You're better than that. I consider myself a grzy fan (whether you like it or not), and I appreciate a little acerbic wit now and then as much as the next guy, but when YOU have no data, you ought to tread a little more lightly.
You're an engineer. I'm a stupid lawyer, but even I can see that the stresses on a fork in normal riding are almost exclusively either along the axis of the fork (bumps, bunny hops) or the axis of the bike (bumps again). The twisting forces of a stationary fork and a loose rear are entirely different.