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MountainBikeReview.com's Forum Archives - Lets Talk about Shocks
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Fox forx clearance issues on small frames (long, w/ pics)... (19 posts)
|  Fox forx clearance issues on small frames (long, w/ pics)... | Anonymous Gerbil
Jan 12, 2003 12:48 PM | | I just posted my review on the new F80RLT fork. Overall, it is a great performing fork, and if faced with making a choice again, I would still pick the F80. But there are some problems with the adjustment knob stackheight design - especially for small frames - that fortunately my bike shop creatively solved. In normal everyday use, this is not a problem. But if you are involved in a crash and the handlebar/front tire is hit in a certain way that forces your front end to twist 90-plus-degrees to the right and the knobs hit the bottom of the down tube, there could be some serious damage, possibly ruining the frame. I am posting this simply as an FYI to others who have small frames, or frames with large support gussets at the downtube-headtube joint.
When the fork came in, we installed the King headset and inserted the fork to see if there were any clearance issues. There were - about 4mm worth. I called up Seven about it. I asked them if any damage occured whether they would cover it under warranty. They said they would not.
I called up Fox and asked them what I could do. They suggested I wrap some inner tube in the area on the downtube where the fork would hit. As if a flimsy innertube would protect my frame in a heavy crash. If inner tubes were that strong, I would not be running tubeless tires! Fox also said that they have had similar complaints from folks who owned Moots frames. I asked them whether they made a rebound adjustment knob with a lower stack height, but they did not.
My local bike shop did two things to solve this little problem. First, they CNC machined a custom aluminum spacer - 2 mm in height - to fit between the fork's steerer tube and the bottom of the headset. You can see it in the pic, right below the bottom headset cups.
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But this still did not give the necessary clearance. For those familiar with Fox Float models, the knob on the left is for the air pressure adjustment. This side cleared without any problems. The knob(s) on the right (depending on what model you have, you would have one or more adjustment knobs) however did not even come close to clearing the downtube. In the case of the F90 RLT, there are two knobs - a blue one for the lockout feature and one red knob sitting above that for rebound adjustments. It was the red rebound knob that was hitting the bottom of the downtube, the blue lockout knob cleared just fine. So my bike shop CNC machined (beautifully, I might add) the edges of the rebound knob so that everything would clear.
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And the result is that everything clears, though barely. Fortunately the Fox Forx design is so stiff that I do not have to worry about the fork deflecting sideways in normal use and ploughing into the downtube. I also worked out an understanding with Seven on this matter and am happy to say that they will take care of me should this type of damage occur. I have it in writing!
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Here is the final set up. I am running the new XTR/XT disc brake combo and have posted some more pics of that under the "Brake Time" section if anyone is interested.
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As I stated earlier, I would buy this fork if I had to make the decision all over again. The fork is that good. But I think all the manufacturers (Rock Shox, Fox, Zokes, Manitou, etc.) need to get together and agree upon a standard stack height for their adjustment knobs - though I do not forsee that happening. I know some of the new upper-end Rock Shocx models have a remote lockout feature. I have seen some pics of the adjustment knobs on those things. I shudder to think what would happen if I had one of those on my bike and crashed the wrong way. |
| What bike shop has their own CNC equipment?... | D.F.L.
Jan 12, 2003 5:25 PM | | THAT'S a well-equipped shop. Do they produce their own bikes? Why do they have CNC machines? |
| a shop where i'd gladly spend all my money... | zedro
Jan 12, 2003 6:03 PM | | what a dream... |
| I was thinking the same thing...that shop is a keeper! (nm) | AndyH
Jan 13, 2003 5:41 AM | | |
| Yes. What shop/where is it? nm | Nat
Jan 13, 2003 8:25 AM | | |
| not CNC machined | laffeaux
Jan 13, 2003 5:12 PM | | I saw "CNC machined" too, and was going to comment. It's likely that they machined the part. It's very unlikely that they used (or own) a CNC machine.
CNC = computer numeric controlled
A part is only machined using a CNC machine when you need to make lots of a single part. You install the stock, press a button, and out pops a part (assuming someone has programed the machine properly). A CNC machined part is NOT handmade.
In this case, the shop may have turned the part on a lathe, or using a milling machine to do the work. In either case, it was not a CNC machine. Working buy hand is faster (in small quantities), and often produces higher quality work. The advantage of the CNC machine comes into play when you want 1,000 items that are all the same. A machinist would get really bored with the repitition.
In any case, it sounds like the shop did a good job. |
| not CNC machined | Anonymous Gerbil
Jan 13, 2003 5:57 PM | | You are probably correct. I am not a technical person. My bad. |
| no problem | laffeaux
Jan 13, 2003 6:37 PM | | I see it on this site a lot. I think most people assume that all machines are CNC, and few (in small shops) actually are.
I spent two summers during college working at a machine shop, mostly operating the CNC machines (since they require less skill once set up), and driving the fork truck. It was a fun job in retrospect, but I busted my butt for $3.80/hr. |
| speaking of broad generalizations | wc
Jan 15, 2003 7:15 PM | | "A part is only machined using a CNC machine when you need to make lots of a single part."
Nothing could be further from the truth. Sure, CNC machines can be used to produce high volumes but they are also used extensively for single piece production. I spent a lot of time programming a CNC horizontal machining center that never saw the same part twice, ever.
Not flaming, just figured while we're clearing things up ... |
| pretty much the deal at school... | zedro
Jan 15, 2003 10:36 PM | | 5 axis machine centers for prototyping. Of course we havent figured out how to program the thing yet. |
| probably not their own.... | gra$$ya$$
Jan 14, 2003 1:22 PM | | most likely the shop doesn't own it, but one of the mechanics is a machinist and has access to the equipment. Or they have something going with the local machine shop... |
| how do I check clearance on the RLT? | SGG
Jan 14, 2003 8:01 AM | | How do I check to see if I will have the same problem that you had? I am getting ready to buy an RLT, but don't want to run into the same problem. My frame is a 19" Independent Fabrications, so not small (you don't say what size your frame is). Is the clearance issue a function of a shorter head tube combined with a steeper downtube due to the geometry of the frame, a problem with putting Fox forks on Seven bikes, or just a problem with Fox forks?
The IF has a small gusset at the downtube. As a final say, maybe I will call IF and see what they say.
Steve |
| It's a frame issue here... | NoWay
Jan 14, 2003 8:31 AM | | ...nothing to do with the fox forks in this case. It happens a lot with frames originally not designed for susp forks. Just look at the pictures, the fox provides plenty of room, the frame does not.
Same thing on my Breezer Lightning. Sorry to say that , but the frame builders screwed up a bit ;) |
| It's a frame issue here... - yes, it is | Anonymous Gerbil
Jan 14, 2003 9:31 AM | | I had specifically told Seven when placing my order that I am getting the F80 RLT and they need to design the frame with that in consideration.
But at the same time, when you get to small frames or frames with thick gussets, this issue crops up. And one cannot simply solve it by speccing a longer headtube - there are safety concerns on whether a longer headtube can be strong enough to take some hits through the fork without adequate support.
My frame is *much* smaller compared to your 19-incher. Mine is 14 inches. I definitely recommend calling up Independant Fabrications and discussing this with them. When it comes to titanium, decisions you make are set in stone and you can't go back - not cheaply anyways. |
| It's a frame issue here... - yes, it is | SGG
Jan 14, 2003 9:36 AM | | Actually, my frame is a steel Deluxe, and I got it at cost, so the situation is not as financially dire as it could be. However, I think that the RLT is the best fork out there for my situation, and I would really like to use it.
The IF guys recommended the Fox Float forks, but I don't know if they have checked to make sure that forks with a lockout lever will clear the downtube. I would bet that the RLT is the same dimensions as last year's RLC 80mm travel, but I'll call them up and make sure.
Thanks for the heads up...
Steve |
| By the way, beautiful ride. Could you.. | NoWay
Jan 15, 2003 7:42 AM | | ...post a picture of the whole bike ? I love small steel frames. |
| This weekend | Anonymous Gerbil
Jan 15, 2003 11:29 AM | | Look for lots of pics this weekend. Unless, of course, you are referring to the IF frame that SSG is talking about. |
| Nah, I'm interested in yours; can't wait !-nm- | NoWay
Jan 15, 2003 12:48 PM | | nm |
| Here are some - if you can't wait ... | Anonymous Gerbil
Jan 15, 2003 2:04 PM | | At least they will hold you over until I post some more this weekend
http://forums13.consumerreview.com/crforum?viewall@@.ef8b1c9
http://forums13.consumerreview.com/crforum?viewall@@.ef8b1c1 |
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